Adding upstream version 1.18.10.upstream/1.18.10upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

86 files changed, 42111 insertions, 0 deletions

diff --git a/src/encoding/ascii85/ascii85.go b/src/encoding/ascii85/ascii85.go
new file mode 100644
index 0000000..f1f7af8
--- /dev/null
+++ b/src/encoding/ascii85/ascii85.go
@@ -0,0 +1,308 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package ascii85 implements the ascii85 data encoding
+// as used in the btoa tool and Adobe's PostScript and PDF document formats.
+package ascii85
+
+import (
+	"io"
+	"strconv"
+)
+
+/*
+ * Encoder
+ */
+
+// Encode encodes src into at most MaxEncodedLen(len(src))
+// bytes of dst, returning the actual number of bytes written.
+//
+// The encoding handles 4-byte chunks, using a special encoding
+// for the last fragment, so Encode is not appropriate for use on
+// individual blocks of a large data stream. Use NewEncoder() instead.
+//
+// Often, ascii85-encoded data is wrapped in <~ and ~> symbols.
+// Encode does not add these.
+func Encode(dst, src []byte) int {
+	if len(src) == 0 {
+		return 0
+	}
+
+	n := 0
+	for len(src) > 0 {
+		dst[0] = 0
+		dst[1] = 0
+		dst[2] = 0
+		dst[3] = 0
+		dst[4] = 0
+
+		// Unpack 4 bytes into uint32 to repack into base 85 5-byte.
+		var v uint32
+		switch len(src) {
+		default:
+			v |= uint32(src[3])
+			fallthrough
+		case 3:
+			v |= uint32(src[2]) << 8
+			fallthrough
+		case 2:
+			v |= uint32(src[1]) << 16
+			fallthrough
+		case 1:
+			v |= uint32(src[0]) << 24
+		}
+
+		// Special case: zero (!!!!!) shortens to z.
+		if v == 0 && len(src) >= 4 {
+			dst[0] = 'z'
+			dst = dst[1:]
+			src = src[4:]
+			n++
+			continue
+		}
+
+		// Otherwise, 5 base 85 digits starting at !.
+		for i := 4; i >= 0; i-- {
+			dst[i] = '!' + byte(v%85)
+			v /= 85
+		}
+
+		// If src was short, discard the low destination bytes.
+		m := 5
+		if len(src) < 4 {
+			m -= 4 - len(src)
+			src = nil
+		} else {
+			src = src[4:]
+		}
+		dst = dst[m:]
+		n += m
+	}
+	return n
+}
+
+// MaxEncodedLen returns the maximum length of an encoding of n source bytes.
+func MaxEncodedLen(n int) int { return (n + 3) / 4 * 5 }
+
+// NewEncoder returns a new ascii85 stream encoder. Data written to
+// the returned writer will be encoded and then written to w.
+// Ascii85 encodings operate in 32-bit blocks; when finished
+// writing, the caller must Close the returned encoder to flush any
+// trailing partial block.
+func NewEncoder(w io.Writer) io.WriteCloser { return &encoder{w: w} }
+
+type encoder struct {
+	err  error
+	w    io.Writer
+	buf  [4]byte    // buffered data waiting to be encoded
+	nbuf int        // number of bytes in buf
+	out  [1024]byte // output buffer
+}
+
+func (e *encoder) Write(p []byte) (n int, err error) {
+	if e.err != nil {
+		return 0, e.err
+	}
+
+	// Leading fringe.
+	if e.nbuf > 0 {
+		var i int
+		for i = 0; i < len(p) && e.nbuf < 4; i++ {
+			e.buf[e.nbuf] = p[i]
+			e.nbuf++
+		}
+		n += i
+		p = p[i:]
+		if e.nbuf < 4 {
+			return
+		}
+		nout := Encode(e.out[0:], e.buf[0:])
+		if _, e.err = e.w.Write(e.out[0:nout]); e.err != nil {
+			return n, e.err
+		}
+		e.nbuf = 0
+	}
+
+	// Large interior chunks.
+	for len(p) >= 4 {
+		nn := len(e.out) / 5 * 4
+		if nn > len(p) {
+			nn = len(p)
+		}
+		nn -= nn % 4
+		if nn > 0 {
+			nout := Encode(e.out[0:], p[0:nn])
+			if _, e.err = e.w.Write(e.out[0:nout]); e.err != nil {
+				return n, e.err
+			}
+		}
+		n += nn
+		p = p[nn:]
+	}
+
+	// Trailing fringe.
+	copy(e.buf[:], p)
+	e.nbuf = len(p)
+	n += len(p)
+	return
+}
+
+// Close flushes any pending output from the encoder.
+// It is an error to call Write after calling Close.
+func (e *encoder) Close() error {
+	// If there's anything left in the buffer, flush it out
+	if e.err == nil && e.nbuf > 0 {
+		nout := Encode(e.out[0:], e.buf[0:e.nbuf])
+		e.nbuf = 0
+		_, e.err = e.w.Write(e.out[0:nout])
+	}
+	return e.err
+}
+
+/*
+ * Decoder
+ */
+
+type CorruptInputError int64
+
+func (e CorruptInputError) Error() string {
+	return "illegal ascii85 data at input byte " + strconv.FormatInt(int64(e), 10)
+}
+
+// Decode decodes src into dst, returning both the number
+// of bytes written to dst and the number consumed from src.
+// If src contains invalid ascii85 data, Decode will return the
+// number of bytes successfully written and a CorruptInputError.
+// Decode ignores space and control characters in src.
+// Often, ascii85-encoded data is wrapped in <~ and ~> symbols.
+// Decode expects these to have been stripped by the caller.
+//
+// If flush is true, Decode assumes that src represents the
+// end of the input stream and processes it completely rather
+// than wait for the completion of another 32-bit block.
+//
+// NewDecoder wraps an io.Reader interface around Decode.
+//
+func Decode(dst, src []byte, flush bool) (ndst, nsrc int, err error) {
+	var v uint32
+	var nb int
+	for i, b := range src {
+		if len(dst)-ndst < 4 {
+			return
+		}
+		switch {
+		case b <= ' ':
+			continue
+		case b == 'z' && nb == 0:
+			nb = 5
+			v = 0
+		case '!' <= b && b <= 'u':
+			v = v*85 + uint32(b-'!')
+			nb++
+		default:
+			return 0, 0, CorruptInputError(i)
+		}
+		if nb == 5 {
+			nsrc = i + 1
+			dst[ndst] = byte(v >> 24)
+			dst[ndst+1] = byte(v >> 16)
+			dst[ndst+2] = byte(v >> 8)
+			dst[ndst+3] = byte(v)
+			ndst += 4
+			nb = 0
+			v = 0
+		}
+	}
+	if flush {
+		nsrc = len(src)
+		if nb > 0 {
+			// The number of output bytes in the last fragment
+			// is the number of leftover input bytes - 1:
+			// the extra byte provides enough bits to cover
+			// the inefficiency of the encoding for the block.
+			if nb == 1 {
+				return 0, 0, CorruptInputError(len(src))
+			}
+			for i := nb; i < 5; i++ {
+				// The short encoding truncated the output value.
+				// We have to assume the worst case values (digit 84)
+				// in order to ensure that the top bits are correct.
+				v = v*85 + 84
+			}
+			for i := 0; i < nb-1; i++ {
+				dst[ndst] = byte(v >> 24)
+				v <<= 8
+				ndst++
+			}
+		}
+	}
+	return
+}
+
+// NewDecoder constructs a new ascii85 stream decoder.
+func NewDecoder(r io.Reader) io.Reader { return &decoder{r: r} }
+
+type decoder struct {
+	err     error
+	readErr error
+	r       io.Reader
+	buf     [1024]byte // leftover input
+	nbuf    int
+	out     []byte // leftover decoded output
+	outbuf  [1024]byte
+}
+
+func (d *decoder) Read(p []byte) (n int, err error) {
+	if len(p) == 0 {
+		return 0, nil
+	}
+	if d.err != nil {
+		return 0, d.err
+	}
+
+	for {
+		// Copy leftover output from last decode.
+		if len(d.out) > 0 {
+			n = copy(p, d.out)
+			d.out = d.out[n:]
+			return
+		}
+
+		// Decode leftover input from last read.
+		var nn, nsrc, ndst int
+		if d.nbuf > 0 {
+			ndst, nsrc, d.err = Decode(d.outbuf[0:], d.buf[0:d.nbuf], d.readErr != nil)
+			if ndst > 0 {
+				d.out = d.outbuf[0:ndst]
+				d.nbuf = copy(d.buf[0:], d.buf[nsrc:d.nbuf])
+				continue // copy out and return
+			}
+			if ndst == 0 && d.err == nil {
+				// Special case: input buffer is mostly filled with non-data bytes.
+				// Filter out such bytes to make room for more input.
+				off := 0
+				for i := 0; i < d.nbuf; i++ {
+					if d.buf[i] > ' ' {
+						d.buf[off] = d.buf[i]
+						off++
+					}
+				}
+				d.nbuf = off
+			}
+		}
+
+		// Out of input, out of decoded output. Check errors.
+		if d.err != nil {
+			return 0, d.err
+		}
+		if d.readErr != nil {
+			d.err = d.readErr
+			return 0, d.err
+		}
+
+		// Read more data.
+		nn, d.readErr = d.r.Read(d.buf[d.nbuf:])
+		d.nbuf += nn
+	}
+}
diff --git a/src/encoding/ascii85/ascii85_test.go b/src/encoding/ascii85/ascii85_test.go
new file mode 100644
index 0000000..9e6b34e
--- /dev/null
+++ b/src/encoding/ascii85/ascii85_test.go
@@ -0,0 +1,214 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ascii85
+
+import (
+	"bytes"
+	"io"
+	"strings"
+	"testing"
+)
+
+type testpair struct {
+	decoded, encoded string
+}
+
+var bigtest = testpair{
+	"Man is distinguished, not only by his reason, but by this singular passion from " +
+		"other animals, which is a lust of the mind, that by a perseverance of delight in " +
+		"the continued and indefatigable generation of knowledge, exceeds the short " +
+		"vehemence of any carnal pleasure.",
+	"9jqo^BlbD-BleB1DJ+*+F(f,q/0JhKF<GL>Cj@.4Gp$d7F!,L7@<6@)/0JDEF<G%<+EV:2F!,\n" +
+		"O<DJ+*.@<*K0@<6L(Df-\\0Ec5e;DffZ(EZee.Bl.9pF\"AGXBPCsi+DGm>@3BB/F*&OCAfu2/AKY\n" +
+		"i(DIb:@FD,*)+C]U=@3BN#EcYf8ATD3s@q?d$AftVqCh[NqF<G:8+EV:.+Cf>-FD5W8ARlolDIa\n" +
+		"l(DId<j@<?3r@:F%a+D58'ATD4$Bl@l3De:,-DJs`8ARoFb/0JMK@qB4^F!,R<AKZ&-DfTqBG%G\n" +
+		">uD.RTpAKYo'+CT/5+Cei#DII?(E,9)oF*2M7/c\n",
+}
+
+var pairs = []testpair{
+	// Encode returns 0 when len(src) is 0
+	{
+		"",
+		"",
+	},
+	// Wikipedia example
+	bigtest,
+	// Special case when shortening !!!!! to z.
+	{
+		"\000\000\000\000",
+		"z",
+	},
+}
+
+func testEqual(t *testing.T, msg string, args ...any) bool {
+	t.Helper()
+	if args[len(args)-2] != args[len(args)-1] {
+		t.Errorf(msg, args...)
+		return false
+	}
+	return true
+}
+
+func strip85(s string) string {
+	t := make([]byte, len(s))
+	w := 0
+	for r := 0; r < len(s); r++ {
+		c := s[r]
+		if c > ' ' {
+			t[w] = c
+			w++
+		}
+	}
+	return string(t[0:w])
+}
+
+func TestEncode(t *testing.T) {
+	for _, p := range pairs {
+		buf := make([]byte, MaxEncodedLen(len(p.decoded)))
+		n := Encode(buf, []byte(p.decoded))
+		buf = buf[0:n]
+		testEqual(t, "Encode(%q) = %q, want %q", p.decoded, strip85(string(buf)), strip85(p.encoded))
+	}
+}
+
+func TestEncoder(t *testing.T) {
+	for _, p := range pairs {
+		bb := &bytes.Buffer{}
+		encoder := NewEncoder(bb)
+		encoder.Write([]byte(p.decoded))
+		encoder.Close()
+		testEqual(t, "Encode(%q) = %q, want %q", p.decoded, strip85(bb.String()), strip85(p.encoded))
+	}
+}
+
+func TestEncoderBuffering(t *testing.T) {
+	input := []byte(bigtest.decoded)
+	for bs := 1; bs <= 12; bs++ {
+		bb := &bytes.Buffer{}
+		encoder := NewEncoder(bb)
+		for pos := 0; pos < len(input); pos += bs {
+			end := pos + bs
+			if end > len(input) {
+				end = len(input)
+			}
+			n, err := encoder.Write(input[pos:end])
+			testEqual(t, "Write(%q) gave error %v, want %v", input[pos:end], err, error(nil))
+			testEqual(t, "Write(%q) gave length %v, want %v", input[pos:end], n, end-pos)
+		}
+		err := encoder.Close()
+		testEqual(t, "Close gave error %v, want %v", err, error(nil))
+		testEqual(t, "Encoding/%d of %q = %q, want %q", bs, bigtest.decoded, strip85(bb.String()), strip85(bigtest.encoded))
+	}
+}
+
+func TestDecode(t *testing.T) {
+	for _, p := range pairs {
+		dbuf := make([]byte, 4*len(p.encoded))
+		ndst, nsrc, err := Decode(dbuf, []byte(p.encoded), true)
+		testEqual(t, "Decode(%q) = error %v, want %v", p.encoded, err, error(nil))
+		testEqual(t, "Decode(%q) = nsrc %v, want %v", p.encoded, nsrc, len(p.encoded))
+		testEqual(t, "Decode(%q) = ndst %v, want %v", p.encoded, ndst, len(p.decoded))
+		testEqual(t, "Decode(%q) = %q, want %q", p.encoded, string(dbuf[0:ndst]), p.decoded)
+	}
+}
+
+func TestDecoder(t *testing.T) {
+	for _, p := range pairs {
+		decoder := NewDecoder(strings.NewReader(p.encoded))
+		dbuf, err := io.ReadAll(decoder)
+		if err != nil {
+			t.Fatal("Read failed", err)
+		}
+		testEqual(t, "Read from %q = length %v, want %v", p.encoded, len(dbuf), len(p.decoded))
+		testEqual(t, "Decoding of %q = %q, want %q", p.encoded, string(dbuf), p.decoded)
+		if err != nil {
+			testEqual(t, "Read from %q = %v, want %v", p.encoded, err, io.EOF)
+		}
+	}
+}
+
+func TestDecoderBuffering(t *testing.T) {
+	for bs := 1; bs <= 12; bs++ {
+		decoder := NewDecoder(strings.NewReader(bigtest.encoded))
+		buf := make([]byte, len(bigtest.decoded)+12)
+		var total int
+		var n int
+		var err error
+		for total = 0; total < len(bigtest.decoded) && err == nil; {
+			n, err = decoder.Read(buf[total : total+bs])
+			total += n
+		}
+		if err != nil && err != io.EOF {
+			t.Errorf("Read from %q at pos %d = %d, unexpected error %v", bigtest.encoded, total, n, err)
+		}
+		testEqual(t, "Decoding/%d of %q = %q, want %q", bs, bigtest.encoded, string(buf[0:total]), bigtest.decoded)
+	}
+}
+
+func TestDecodeCorrupt(t *testing.T) {
+	type corrupt struct {
+		e string
+		p int
+	}
+	examples := []corrupt{
+		{"v", 0},
+		{"!z!!!!!!!!!", 1},
+	}
+
+	for _, e := range examples {
+		dbuf := make([]byte, 4*len(e.e))
+		_, _, err := Decode(dbuf, []byte(e.e), true)
+		switch err := err.(type) {
+		case CorruptInputError:
+			testEqual(t, "Corruption in %q at offset %v, want %v", e.e, int(err), e.p)
+		default:
+			t.Error("Decoder failed to detect corruption in", e)
+		}
+	}
+}
+
+func TestBig(t *testing.T) {
+	n := 3*1000 + 1
+	raw := make([]byte, n)
+	const alpha = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
+	for i := 0; i < n; i++ {
+		raw[i] = alpha[i%len(alpha)]
+	}
+	encoded := new(bytes.Buffer)
+	w := NewEncoder(encoded)
+	nn, err := w.Write(raw)
+	if nn != n || err != nil {
+		t.Fatalf("Encoder.Write(raw) = %d, %v want %d, nil", nn, err, n)
+	}
+	err = w.Close()
+	if err != nil {
+		t.Fatalf("Encoder.Close() = %v want nil", err)
+	}
+	decoded, err := io.ReadAll(NewDecoder(encoded))
+	if err != nil {
+		t.Fatalf("io.ReadAll(NewDecoder(...)): %v", err)
+	}
+
+	if !bytes.Equal(raw, decoded) {
+		var i int
+		for i = 0; i < len(decoded) && i < len(raw); i++ {
+			if decoded[i] != raw[i] {
+				break
+			}
+		}
+		t.Errorf("Decode(Encode(%d-byte string)) failed at offset %d", n, i)
+	}
+}
+
+func TestDecoderInternalWhitespace(t *testing.T) {
+	s := strings.Repeat(" ", 2048) + "z"
+	decoded, err := io.ReadAll(NewDecoder(strings.NewReader(s)))
+	if err != nil {
+		t.Errorf("Decode gave error %v", err)
+	}
+	if want := []byte("\000\000\000\000"); !bytes.Equal(want, decoded) {
+		t.Errorf("Decode failed: got %v, want %v", decoded, want)
+	}
+}
diff --git a/src/encoding/asn1/asn1.go b/src/encoding/asn1/asn1.go
new file mode 100644
index 0000000..cad1d7b
--- /dev/null
+++ b/src/encoding/asn1/asn1.go
@@ -0,0 +1,1122 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package asn1 implements parsing of DER-encoded ASN.1 data structures,
+// as defined in ITU-T Rec X.690.
+//
+// See also ``A Layman's Guide to a Subset of ASN.1, BER, and DER,''
+// http://luca.ntop.org/Teaching/Appunti/asn1.html.
+package asn1
+
+// ASN.1 is a syntax for specifying abstract objects and BER, DER, PER, XER etc
+// are different encoding formats for those objects. Here, we'll be dealing
+// with DER, the Distinguished Encoding Rules. DER is used in X.509 because
+// it's fast to parse and, unlike BER, has a unique encoding for every object.
+// When calculating hashes over objects, it's important that the resulting
+// bytes be the same at both ends and DER removes this margin of error.
+//
+// ASN.1 is very complex and this package doesn't attempt to implement
+// everything by any means.
+
+import (
+	"errors"
+	"fmt"
+	"math"
+	"math/big"
+	"reflect"
+	"strconv"
+	"time"
+	"unicode/utf16"
+	"unicode/utf8"
+)
+
+// A StructuralError suggests that the ASN.1 data is valid, but the Go type
+// which is receiving it doesn't match.
+type StructuralError struct {
+	Msg string
+}
+
+func (e StructuralError) Error() string { return "asn1: structure error: " + e.Msg }
+
+// A SyntaxError suggests that the ASN.1 data is invalid.
+type SyntaxError struct {
+	Msg string
+}
+
+func (e SyntaxError) Error() string { return "asn1: syntax error: " + e.Msg }
+
+// We start by dealing with each of the primitive types in turn.
+
+// BOOLEAN
+
+func parseBool(bytes []byte) (ret bool, err error) {
+	if len(bytes) != 1 {
+		err = SyntaxError{"invalid boolean"}
+		return
+	}
+
+	// DER demands that "If the encoding represents the boolean value TRUE,
+	// its single contents octet shall have all eight bits set to one."
+	// Thus only 0 and 255 are valid encoded values.
+	switch bytes[0] {
+	case 0:
+		ret = false
+	case 0xff:
+		ret = true
+	default:
+		err = SyntaxError{"invalid boolean"}
+	}
+
+	return
+}
+
+// INTEGER
+
+// checkInteger returns nil if the given bytes are a valid DER-encoded
+// INTEGER and an error otherwise.
+func checkInteger(bytes []byte) error {
+	if len(bytes) == 0 {
+		return StructuralError{"empty integer"}
+	}
+	if len(bytes) == 1 {
+		return nil
+	}
+	if (bytes[0] == 0 && bytes[1]&0x80 == 0) || (bytes[0] == 0xff && bytes[1]&0x80 == 0x80) {
+		return StructuralError{"integer not minimally-encoded"}
+	}
+	return nil
+}
+
+// parseInt64 treats the given bytes as a big-endian, signed integer and
+// returns the result.
+func parseInt64(bytes []byte) (ret int64, err error) {
+	err = checkInteger(bytes)
+	if err != nil {
+		return
+	}
+	if len(bytes) > 8 {
+		// We'll overflow an int64 in this case.
+		err = StructuralError{"integer too large"}
+		return
+	}
+	for bytesRead := 0; bytesRead < len(bytes); bytesRead++ {
+		ret <<= 8
+		ret |= int64(bytes[bytesRead])
+	}
+
+	// Shift up and down in order to sign extend the result.
+	ret <<= 64 - uint8(len(bytes))*8
+	ret >>= 64 - uint8(len(bytes))*8
+	return
+}
+
+// parseInt treats the given bytes as a big-endian, signed integer and returns
+// the result.
+func parseInt32(bytes []byte) (int32, error) {
+	if err := checkInteger(bytes); err != nil {
+		return 0, err
+	}
+	ret64, err := parseInt64(bytes)
+	if err != nil {
+		return 0, err
+	}
+	if ret64 != int64(int32(ret64)) {
+		return 0, StructuralError{"integer too large"}
+	}
+	return int32(ret64), nil
+}
+
+var bigOne = big.NewInt(1)
+
+// parseBigInt treats the given bytes as a big-endian, signed integer and returns
+// the result.
+func parseBigInt(bytes []byte) (*big.Int, error) {
+	if err := checkInteger(bytes); err != nil {
+		return nil, err
+	}
+	ret := new(big.Int)
+	if len(bytes) > 0 && bytes[0]&0x80 == 0x80 {
+		// This is a negative number.
+		notBytes := make([]byte, len(bytes))
+		for i := range notBytes {
+			notBytes[i] = ^bytes[i]
+		}
+		ret.SetBytes(notBytes)
+		ret.Add(ret, bigOne)
+		ret.Neg(ret)
+		return ret, nil
+	}
+	ret.SetBytes(bytes)
+	return ret, nil
+}
+
+// BIT STRING
+
+// BitString is the structure to use when you want an ASN.1 BIT STRING type. A
+// bit string is padded up to the nearest byte in memory and the number of
+// valid bits is recorded. Padding bits will be zero.
+type BitString struct {
+	Bytes     []byte // bits packed into bytes.
+	BitLength int    // length in bits.
+}
+
+// At returns the bit at the given index. If the index is out of range it
+// returns false.
+func (b BitString) At(i int) int {
+	if i < 0 || i >= b.BitLength {
+		return 0
+	}
+	x := i / 8
+	y := 7 - uint(i%8)
+	return int(b.Bytes[x]>>y) & 1
+}
+
+// RightAlign returns a slice where the padding bits are at the beginning. The
+// slice may share memory with the BitString.
+func (b BitString) RightAlign() []byte {
+	shift := uint(8 - (b.BitLength % 8))
+	if shift == 8 || len(b.Bytes) == 0 {
+		return b.Bytes
+	}
+
+	a := make([]byte, len(b.Bytes))
+	a[0] = b.Bytes[0] >> shift
+	for i := 1; i < len(b.Bytes); i++ {
+		a[i] = b.Bytes[i-1] << (8 - shift)
+		a[i] |= b.Bytes[i] >> shift
+	}
+
+	return a
+}
+
+// parseBitString parses an ASN.1 bit string from the given byte slice and returns it.
+func parseBitString(bytes []byte) (ret BitString, err error) {
+	if len(bytes) == 0 {
+		err = SyntaxError{"zero length BIT STRING"}
+		return
+	}
+	paddingBits := int(bytes[0])
+	if paddingBits > 7 ||
+		len(bytes) == 1 && paddingBits > 0 ||
+		bytes[len(bytes)-1]&((1<<bytes[0])-1) != 0 {
+		err = SyntaxError{"invalid padding bits in BIT STRING"}
+		return
+	}
+	ret.BitLength = (len(bytes)-1)*8 - paddingBits
+	ret.Bytes = bytes[1:]
+	return
+}
+
+// NULL
+
+// NullRawValue is a RawValue with its Tag set to the ASN.1 NULL type tag (5).
+var NullRawValue = RawValue{Tag: TagNull}
+
+// NullBytes contains bytes representing the DER-encoded ASN.1 NULL type.
+var NullBytes = []byte{TagNull, 0}
+
+// OBJECT IDENTIFIER
+
+// An ObjectIdentifier represents an ASN.1 OBJECT IDENTIFIER.
+type ObjectIdentifier []int
+
+// Equal reports whether oi and other represent the same identifier.
+func (oi ObjectIdentifier) Equal(other ObjectIdentifier) bool {
+	if len(oi) != len(other) {
+		return false
+	}
+	for i := 0; i < len(oi); i++ {
+		if oi[i] != other[i] {
+			return false
+		}
+	}
+
+	return true
+}
+
+func (oi ObjectIdentifier) String() string {
+	var s string
+
+	for i, v := range oi {
+		if i > 0 {
+			s += "."
+		}
+		s += strconv.Itoa(v)
+	}
+
+	return s
+}
+
+// parseObjectIdentifier parses an OBJECT IDENTIFIER from the given bytes and
+// returns it. An object identifier is a sequence of variable length integers
+// that are assigned in a hierarchy.
+func parseObjectIdentifier(bytes []byte) (s ObjectIdentifier, err error) {
+	if len(bytes) == 0 {
+		err = SyntaxError{"zero length OBJECT IDENTIFIER"}
+		return
+	}
+
+	// In the worst case, we get two elements from the first byte (which is
+	// encoded differently) and then every varint is a single byte long.
+	s = make([]int, len(bytes)+1)
+
+	// The first varint is 40*value1 + value2:
+	// According to this packing, value1 can take the values 0, 1 and 2 only.
+	// When value1 = 0 or value1 = 1, then value2 is <= 39. When value1 = 2,
+	// then there are no restrictions on value2.
+	v, offset, err := parseBase128Int(bytes, 0)
+	if err != nil {
+		return
+	}
+	if v < 80 {
+		s[0] = v / 40
+		s[1] = v % 40
+	} else {
+		s[0] = 2
+		s[1] = v - 80
+	}
+
+	i := 2
+	for ; offset < len(bytes); i++ {
+		v, offset, err = parseBase128Int(bytes, offset)
+		if err != nil {
+			return
+		}
+		s[i] = v
+	}
+	s = s[0:i]
+	return
+}
+
+// ENUMERATED
+
+// An Enumerated is represented as a plain int.
+type Enumerated int
+
+// FLAG
+
+// A Flag accepts any data and is set to true if present.
+type Flag bool
+
+// parseBase128Int parses a base-128 encoded int from the given offset in the
+// given byte slice. It returns the value and the new offset.
+func parseBase128Int(bytes []byte, initOffset int) (ret, offset int, err error) {
+	offset = initOffset
+	var ret64 int64
+	for shifted := 0; offset < len(bytes); shifted++ {
+		// 5 * 7 bits per byte == 35 bits of data
+		// Thus the representation is either non-minimal or too large for an int32
+		if shifted == 5 {
+			err = StructuralError{"base 128 integer too large"}
+			return
+		}
+		ret64 <<= 7
+		b := bytes[offset]
+		// integers should be minimally encoded, so the leading octet should
+		// never be 0x80
+		if shifted == 0 && b == 0x80 {
+			err = SyntaxError{"integer is not minimally encoded"}
+			return
+		}
+		ret64 |= int64(b & 0x7f)
+		offset++
+		if b&0x80 == 0 {
+			ret = int(ret64)
+			// Ensure that the returned value fits in an int on all platforms
+			if ret64 > math.MaxInt32 {
+				err = StructuralError{"base 128 integer too large"}
+			}
+			return
+		}
+	}
+	err = SyntaxError{"truncated base 128 integer"}
+	return
+}
+
+// UTCTime
+
+func parseUTCTime(bytes []byte) (ret time.Time, err error) {
+	s := string(bytes)
+
+	formatStr := "0601021504Z0700"
+	ret, err = time.Parse(formatStr, s)
+	if err != nil {
+		formatStr = "060102150405Z0700"
+		ret, err = time.Parse(formatStr, s)
+	}
+	if err != nil {
+		return
+	}
+
+	if serialized := ret.Format(formatStr); serialized != s {
+		err = fmt.Errorf("asn1: time did not serialize back to the original value and may be invalid: given %q, but serialized as %q", s, serialized)
+		return
+	}
+
+	if ret.Year() >= 2050 {
+		// UTCTime only encodes times prior to 2050. See https://tools.ietf.org/html/rfc5280#section-4.1.2.5.1
+		ret = ret.AddDate(-100, 0, 0)
+	}
+
+	return
+}
+
+// parseGeneralizedTime parses the GeneralizedTime from the given byte slice
+// and returns the resulting time.
+func parseGeneralizedTime(bytes []byte) (ret time.Time, err error) {
+	const formatStr = "20060102150405Z0700"
+	s := string(bytes)
+
+	if ret, err = time.Parse(formatStr, s); err != nil {
+		return
+	}
+
+	if serialized := ret.Format(formatStr); serialized != s {
+		err = fmt.Errorf("asn1: time did not serialize back to the original value and may be invalid: given %q, but serialized as %q", s, serialized)
+	}
+
+	return
+}
+
+// NumericString
+
+// parseNumericString parses an ASN.1 NumericString from the given byte array
+// and returns it.
+func parseNumericString(bytes []byte) (ret string, err error) {
+	for _, b := range bytes {
+		if !isNumeric(b) {
+			return "", SyntaxError{"NumericString contains invalid character"}
+		}
+	}
+	return string(bytes), nil
+}
+
+// isNumeric reports whether the given b is in the ASN.1 NumericString set.
+func isNumeric(b byte) bool {
+	return '0' <= b && b <= '9' ||
+		b == ' '
+}
+
+// PrintableString
+
+// parsePrintableString parses an ASN.1 PrintableString from the given byte
+// array and returns it.
+func parsePrintableString(bytes []byte) (ret string, err error) {
+	for _, b := range bytes {
+		if !isPrintable(b, allowAsterisk, allowAmpersand) {
+			err = SyntaxError{"PrintableString contains invalid character"}
+			return
+		}
+	}
+	ret = string(bytes)
+	return
+}
+
+type asteriskFlag bool
+type ampersandFlag bool
+
+const (
+	allowAsterisk  asteriskFlag = true
+	rejectAsterisk asteriskFlag = false
+
+	allowAmpersand  ampersandFlag = true
+	rejectAmpersand ampersandFlag = false
+)
+
+// isPrintable reports whether the given b is in the ASN.1 PrintableString set.
+// If asterisk is allowAsterisk then '*' is also allowed, reflecting existing
+// practice. If ampersand is allowAmpersand then '&' is allowed as well.
+func isPrintable(b byte, asterisk asteriskFlag, ampersand ampersandFlag) bool {
+	return 'a' <= b && b <= 'z' ||
+		'A' <= b && b <= 'Z' ||
+		'0' <= b && b <= '9' ||
+		'\'' <= b && b <= ')' ||
+		'+' <= b && b <= '/' ||
+		b == ' ' ||
+		b == ':' ||
+		b == '=' ||
+		b == '?' ||
+		// This is technically not allowed in a PrintableString.
+		// However, x509 certificates with wildcard strings don't
+		// always use the correct string type so we permit it.
+		(bool(asterisk) && b == '*') ||
+		// This is not technically allowed either. However, not
+		// only is it relatively common, but there are also a
+		// handful of CA certificates that contain it. At least
+		// one of which will not expire until 2027.
+		(bool(ampersand) && b == '&')
+}
+
+// IA5String
+
+// parseIA5String parses an ASN.1 IA5String (ASCII string) from the given
+// byte slice and returns it.
+func parseIA5String(bytes []byte) (ret string, err error) {
+	for _, b := range bytes {
+		if b >= utf8.RuneSelf {
+			err = SyntaxError{"IA5String contains invalid character"}
+			return
+		}
+	}
+	ret = string(bytes)
+	return
+}
+
+// T61String
+
+// parseT61String parses an ASN.1 T61String (8-bit clean string) from the given
+// byte slice and returns it.
+func parseT61String(bytes []byte) (ret string, err error) {
+	return string(bytes), nil
+}
+
+// UTF8String
+
+// parseUTF8String parses an ASN.1 UTF8String (raw UTF-8) from the given byte
+// array and returns it.
+func parseUTF8String(bytes []byte) (ret string, err error) {
+	if !utf8.Valid(bytes) {
+		return "", errors.New("asn1: invalid UTF-8 string")
+	}
+	return string(bytes), nil
+}
+
+// BMPString
+
+// parseBMPString parses an ASN.1 BMPString (Basic Multilingual Plane of
+// ISO/IEC/ITU 10646-1) from the given byte slice and returns it.
+func parseBMPString(bmpString []byte) (string, error) {
+	if len(bmpString)%2 != 0 {
+		return "", errors.New("pkcs12: odd-length BMP string")
+	}
+
+	// Strip terminator if present.
+	if l := len(bmpString); l >= 2 && bmpString[l-1] == 0 && bmpString[l-2] == 0 {
+		bmpString = bmpString[:l-2]
+	}
+
+	s := make([]uint16, 0, len(bmpString)/2)
+	for len(bmpString) > 0 {
+		s = append(s, uint16(bmpString[0])<<8+uint16(bmpString[1]))
+		bmpString = bmpString[2:]
+	}
+
+	return string(utf16.Decode(s)), nil
+}
+
+// A RawValue represents an undecoded ASN.1 object.
+type RawValue struct {
+	Class, Tag int
+	IsCompound bool
+	Bytes      []byte
+	FullBytes  []byte // includes the tag and length
+}
+
+// RawContent is used to signal that the undecoded, DER data needs to be
+// preserved for a struct. To use it, the first field of the struct must have
+// this type. It's an error for any of the other fields to have this type.
+type RawContent []byte
+
+// Tagging
+
+// parseTagAndLength parses an ASN.1 tag and length pair from the given offset
+// into a byte slice. It returns the parsed data and the new offset. SET and
+// SET OF (tag 17) are mapped to SEQUENCE and SEQUENCE OF (tag 16) since we
+// don't distinguish between ordered and unordered objects in this code.
+func parseTagAndLength(bytes []byte, initOffset int) (ret tagAndLength, offset int, err error) {
+	offset = initOffset
+	// parseTagAndLength should not be called without at least a single
+	// byte to read. Thus this check is for robustness:
+	if offset >= len(bytes) {
+		err = errors.New("asn1: internal error in parseTagAndLength")
+		return
+	}
+	b := bytes[offset]
+	offset++
+	ret.class = int(b >> 6)
+	ret.isCompound = b&0x20 == 0x20
+	ret.tag = int(b & 0x1f)
+
+	// If the bottom five bits are set, then the tag number is actually base 128
+	// encoded afterwards
+	if ret.tag == 0x1f {
+		ret.tag, offset, err = parseBase128Int(bytes, offset)
+		if err != nil {
+			return
+		}
+		// Tags should be encoded in minimal form.
+		if ret.tag < 0x1f {
+			err = SyntaxError{"non-minimal tag"}
+			return
+		}
+	}
+	if offset >= len(bytes) {
+		err = SyntaxError{"truncated tag or length"}
+		return
+	}
+	b = bytes[offset]
+	offset++
+	if b&0x80 == 0 {
+		// The length is encoded in the bottom 7 bits.
+		ret.length = int(b & 0x7f)
+	} else {
+		// Bottom 7 bits give the number of length bytes to follow.
+		numBytes := int(b & 0x7f)
+		if numBytes == 0 {
+			err = SyntaxError{"indefinite length found (not DER)"}
+			return
+		}
+		ret.length = 0
+		for i := 0; i < numBytes; i++ {
+			if offset >= len(bytes) {
+				err = SyntaxError{"truncated tag or length"}
+				return
+			}
+			b = bytes[offset]
+			offset++
+			if ret.length >= 1<<23 {
+				// We can't shift ret.length up without
+				// overflowing.
+				err = StructuralError{"length too large"}
+				return
+			}
+			ret.length <<= 8
+			ret.length |= int(b)
+			if ret.length == 0 {
+				// DER requires that lengths be minimal.
+				err = StructuralError{"superfluous leading zeros in length"}
+				return
+			}
+		}
+		// Short lengths must be encoded in short form.
+		if ret.length < 0x80 {
+			err = StructuralError{"non-minimal length"}
+			return
+		}
+	}
+
+	return
+}
+
+// parseSequenceOf is used for SEQUENCE OF and SET OF values. It tries to parse
+// a number of ASN.1 values from the given byte slice and returns them as a
+// slice of Go values of the given type.
+func parseSequenceOf(bytes []byte, sliceType reflect.Type, elemType reflect.Type) (ret reflect.Value, err error) {
+	matchAny, expectedTag, compoundType, ok := getUniversalType(elemType)
+	if !ok {
+		err = StructuralError{"unknown Go type for slice"}
+		return
+	}
+
+	// First we iterate over the input and count the number of elements,
+	// checking that the types are correct in each case.
+	numElements := 0
+	for offset := 0; offset < len(bytes); {
+		var t tagAndLength
+		t, offset, err = parseTagAndLength(bytes, offset)
+		if err != nil {
+			return
+		}
+		switch t.tag {
+		case TagIA5String, TagGeneralString, TagT61String, TagUTF8String, TagNumericString, TagBMPString:
+			// We pretend that various other string types are
+			// PRINTABLE STRINGs so that a sequence of them can be
+			// parsed into a []string.
+			t.tag = TagPrintableString
+		case TagGeneralizedTime, TagUTCTime:
+			// Likewise, both time types are treated the same.
+			t.tag = TagUTCTime
+		}
+
+		if !matchAny && (t.class != ClassUniversal || t.isCompound != compoundType || t.tag != expectedTag) {
+			err = StructuralError{"sequence tag mismatch"}
+			return
+		}
+		if invalidLength(offset, t.length, len(bytes)) {
+			err = SyntaxError{"truncated sequence"}
+			return
+		}
+		offset += t.length
+		numElements++
+	}
+	ret = reflect.MakeSlice(sliceType, numElements, numElements)
+	params := fieldParameters{}
+	offset := 0
+	for i := 0; i < numElements; i++ {
+		offset, err = parseField(ret.Index(i), bytes, offset, params)
+		if err != nil {
+			return
+		}
+	}
+	return
+}
+
+var (
+	bitStringType        = reflect.TypeOf(BitString{})
+	objectIdentifierType = reflect.TypeOf(ObjectIdentifier{})
+	enumeratedType       = reflect.TypeOf(Enumerated(0))
+	flagType             = reflect.TypeOf(Flag(false))
+	timeType             = reflect.TypeOf(time.Time{})
+	rawValueType         = reflect.TypeOf(RawValue{})
+	rawContentsType      = reflect.TypeOf(RawContent(nil))
+	bigIntType           = reflect.TypeOf(new(big.Int))
+)
+
+// invalidLength reports whether offset + length > sliceLength, or if the
+// addition would overflow.
+func invalidLength(offset, length, sliceLength int) bool {
+	return offset+length < offset || offset+length > sliceLength
+}
+
+// parseField is the main parsing function. Given a byte slice and an offset
+// into the array, it will try to parse a suitable ASN.1 value out and store it
+// in the given Value.
+func parseField(v reflect.Value, bytes []byte, initOffset int, params fieldParameters) (offset int, err error) {
+	offset = initOffset
+	fieldType := v.Type()
+
+	// If we have run out of data, it may be that there are optional elements at the end.
+	if offset == len(bytes) {
+		if !setDefaultValue(v, params) {
+			err = SyntaxError{"sequence truncated"}
+		}
+		return
+	}
+
+	// Deal with the ANY type.
+	if ifaceType := fieldType; ifaceType.Kind() == reflect.Interface && ifaceType.NumMethod() == 0 {
+		var t tagAndLength
+		t, offset, err = parseTagAndLength(bytes, offset)
+		if err != nil {
+			return
+		}
+		if invalidLength(offset, t.length, len(bytes)) {
+			err = SyntaxError{"data truncated"}
+			return
+		}
+		var result any
+		if !t.isCompound && t.class == ClassUniversal {
+			innerBytes := bytes[offset : offset+t.length]
+			switch t.tag {
+			case TagPrintableString:
+				result, err = parsePrintableString(innerBytes)
+			case TagNumericString:
+				result, err = parseNumericString(innerBytes)
+			case TagIA5String:
+				result, err = parseIA5String(innerBytes)
+			case TagT61String:
+				result, err = parseT61String(innerBytes)
+			case TagUTF8String:
+				result, err = parseUTF8String(innerBytes)
+			case TagInteger:
+				result, err = parseInt64(innerBytes)
+			case TagBitString:
+				result, err = parseBitString(innerBytes)
+			case TagOID:
+				result, err = parseObjectIdentifier(innerBytes)
+			case TagUTCTime:
+				result, err = parseUTCTime(innerBytes)
+			case TagGeneralizedTime:
+				result, err = parseGeneralizedTime(innerBytes)
+			case TagOctetString:
+				result = innerBytes
+			case TagBMPString:
+				result, err = parseBMPString(innerBytes)
+			default:
+				// If we don't know how to handle the type, we just leave Value as nil.
+			}
+		}
+		offset += t.length
+		if err != nil {
+			return
+		}
+		if result != nil {
+			v.Set(reflect.ValueOf(result))
+		}
+		return
+	}
+
+	t, offset, err := parseTagAndLength(bytes, offset)
+	if err != nil {
+		return
+	}
+	if params.explicit {
+		expectedClass := ClassContextSpecific
+		if params.application {
+			expectedClass = ClassApplication
+		}
+		if offset == len(bytes) {
+			err = StructuralError{"explicit tag has no child"}
+			return
+		}
+		if t.class == expectedClass && t.tag == *params.tag && (t.length == 0 || t.isCompound) {
+			if fieldType == rawValueType {
+				// The inner element should not be parsed for RawValues.
+			} else if t.length > 0 {
+				t, offset, err = parseTagAndLength(bytes, offset)
+				if err != nil {
+					return
+				}
+			} else {
+				if fieldType != flagType {
+					err = StructuralError{"zero length explicit tag was not an asn1.Flag"}
+					return
+				}
+				v.SetBool(true)
+				return
+			}
+		} else {
+			// The tags didn't match, it might be an optional element.
+			ok := setDefaultValue(v, params)
+			if ok {
+				offset = initOffset
+			} else {
+				err = StructuralError{"explicitly tagged member didn't match"}
+			}
+			return
+		}
+	}
+
+	matchAny, universalTag, compoundType, ok1 := getUniversalType(fieldType)
+	if !ok1 {
+		err = StructuralError{fmt.Sprintf("unknown Go type: %v", fieldType)}
+		return
+	}
+
+	// Special case for strings: all the ASN.1 string types map to the Go
+	// type string. getUniversalType returns the tag for PrintableString
+	// when it sees a string, so if we see a different string type on the
+	// wire, we change the universal type to match.
+	if universalTag == TagPrintableString {
+		if t.class == ClassUniversal {
+			switch t.tag {
+			case TagIA5String, TagGeneralString, TagT61String, TagUTF8String, TagNumericString, TagBMPString:
+				universalTag = t.tag
+			}
+		} else if params.stringType != 0 {
+			universalTag = params.stringType
+		}
+	}
+
+	// Special case for time: UTCTime and GeneralizedTime both map to the
+	// Go type time.Time.
+	if universalTag == TagUTCTime && t.tag == TagGeneralizedTime && t.class == ClassUniversal {
+		universalTag = TagGeneralizedTime
+	}
+
+	if params.set {
+		universalTag = TagSet
+	}
+
+	matchAnyClassAndTag := matchAny
+	expectedClass := ClassUniversal
+	expectedTag := universalTag
+
+	if !params.explicit && params.tag != nil {
+		expectedClass = ClassContextSpecific
+		expectedTag = *params.tag
+		matchAnyClassAndTag = false
+	}
+
+	if !params.explicit && params.application && params.tag != nil {
+		expectedClass = ClassApplication
+		expectedTag = *params.tag
+		matchAnyClassAndTag = false
+	}
+
+	if !params.explicit && params.private && params.tag != nil {
+		expectedClass = ClassPrivate
+		expectedTag = *params.tag
+		matchAnyClassAndTag = false
+	}
+
+	// We have unwrapped any explicit tagging at this point.
+	if !matchAnyClassAndTag && (t.class != expectedClass || t.tag != expectedTag) ||
+		(!matchAny && t.isCompound != compoundType) {
+		// Tags don't match. Again, it could be an optional element.
+		ok := setDefaultValue(v, params)
+		if ok {
+			offset = initOffset
+		} else {
+			err = StructuralError{fmt.Sprintf("tags don't match (%d vs %+v) %+v %s @%d", expectedTag, t, params, fieldType.Name(), offset)}
+		}
+		return
+	}
+	if invalidLength(offset, t.length, len(bytes)) {
+		err = SyntaxError{"data truncated"}
+		return
+	}
+	innerBytes := bytes[offset : offset+t.length]
+	offset += t.length
+
+	// We deal with the structures defined in this package first.
+	switch v := v.Addr().Interface().(type) {
+	case *RawValue:
+		*v = RawValue{t.class, t.tag, t.isCompound, innerBytes, bytes[initOffset:offset]}
+		return
+	case *ObjectIdentifier:
+		*v, err = parseObjectIdentifier(innerBytes)
+		return
+	case *BitString:
+		*v, err = parseBitString(innerBytes)
+		return
+	case *time.Time:
+		if universalTag == TagUTCTime {
+			*v, err = parseUTCTime(innerBytes)
+			return
+		}
+		*v, err = parseGeneralizedTime(innerBytes)
+		return
+	case *Enumerated:
+		parsedInt, err1 := parseInt32(innerBytes)
+		if err1 == nil {
+			*v = Enumerated(parsedInt)
+		}
+		err = err1
+		return
+	case *Flag:
+		*v = true
+		return
+	case **big.Int:
+		parsedInt, err1 := parseBigInt(innerBytes)
+		if err1 == nil {
+			*v = parsedInt
+		}
+		err = err1
+		return
+	}
+	switch val := v; val.Kind() {
+	case reflect.Bool:
+		parsedBool, err1 := parseBool(innerBytes)
+		if err1 == nil {
+			val.SetBool(parsedBool)
+		}
+		err = err1
+		return
+	case reflect.Int, reflect.Int32, reflect.Int64:
+		if val.Type().Size() == 4 {
+			parsedInt, err1 := parseInt32(innerBytes)
+			if err1 == nil {
+				val.SetInt(int64(parsedInt))
+			}
+			err = err1
+		} else {
+			parsedInt, err1 := parseInt64(innerBytes)
+			if err1 == nil {
+				val.SetInt(parsedInt)
+			}
+			err = err1
+		}
+		return
+	// TODO(dfc) Add support for the remaining integer types
+	case reflect.Struct:
+		structType := fieldType
+
+		for i := 0; i < structType.NumField(); i++ {
+			if !structType.Field(i).IsExported() {
+				err = StructuralError{"struct contains unexported fields"}
+				return
+			}
+		}
+
+		if structType.NumField() > 0 &&
+			structType.Field(0).Type == rawContentsType {
+			bytes := bytes[initOffset:offset]
+			val.Field(0).Set(reflect.ValueOf(RawContent(bytes)))
+		}
+
+		innerOffset := 0
+		for i := 0; i < structType.NumField(); i++ {
+			field := structType.Field(i)
+			if i == 0 && field.Type == rawContentsType {
+				continue
+			}
+			innerOffset, err = parseField(val.Field(i), innerBytes, innerOffset, parseFieldParameters(field.Tag.Get("asn1")))
+			if err != nil {
+				return
+			}
+		}
+		// We allow extra bytes at the end of the SEQUENCE because
+		// adding elements to the end has been used in X.509 as the
+		// version numbers have increased.
+		return
+	case reflect.Slice:
+		sliceType := fieldType
+		if sliceType.Elem().Kind() == reflect.Uint8 {
+			val.Set(reflect.MakeSlice(sliceType, len(innerBytes), len(innerBytes)))
+			reflect.Copy(val, reflect.ValueOf(innerBytes))
+			return
+		}
+		newSlice, err1 := parseSequenceOf(innerBytes, sliceType, sliceType.Elem())
+		if err1 == nil {
+			val.Set(newSlice)
+		}
+		err = err1
+		return
+	case reflect.String:
+		var v string
+		switch universalTag {
+		case TagPrintableString:
+			v, err = parsePrintableString(innerBytes)
+		case TagNumericString:
+			v, err = parseNumericString(innerBytes)
+		case TagIA5String:
+			v, err = parseIA5String(innerBytes)
+		case TagT61String:
+			v, err = parseT61String(innerBytes)
+		case TagUTF8String:
+			v, err = parseUTF8String(innerBytes)
+		case TagGeneralString:
+			// GeneralString is specified in ISO-2022/ECMA-35,
+			// A brief review suggests that it includes structures
+			// that allow the encoding to change midstring and
+			// such. We give up and pass it as an 8-bit string.
+			v, err = parseT61String(innerBytes)
+		case TagBMPString:
+			v, err = parseBMPString(innerBytes)
+
+		default:
+			err = SyntaxError{fmt.Sprintf("internal error: unknown string type %d", universalTag)}
+		}
+		if err == nil {
+			val.SetString(v)
+		}
+		return
+	}
+	err = StructuralError{"unsupported: " + v.Type().String()}
+	return
+}
+
+// canHaveDefaultValue reports whether k is a Kind that we will set a default
+// value for. (A signed integer, essentially.)
+func canHaveDefaultValue(k reflect.Kind) bool {
+	switch k {
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return true
+	}
+
+	return false
+}
+
+// setDefaultValue is used to install a default value, from a tag string, into
+// a Value. It is successful if the field was optional, even if a default value
+// wasn't provided or it failed to install it into the Value.
+func setDefaultValue(v reflect.Value, params fieldParameters) (ok bool) {
+	if !params.optional {
+		return
+	}
+	ok = true
+	if params.defaultValue == nil {
+		return
+	}
+	if canHaveDefaultValue(v.Kind()) {
+		v.SetInt(*params.defaultValue)
+	}
+	return
+}
+
+// Unmarshal parses the DER-encoded ASN.1 data structure b
+// and uses the reflect package to fill in an arbitrary value pointed at by val.
+// Because Unmarshal uses the reflect package, the structs
+// being written to must use upper case field names. If val
+// is nil or not a pointer, Unmarshal returns an error.
+//
+// After parsing b, any bytes that were leftover and not used to fill
+// val will be returned in rest. When parsing a SEQUENCE into a struct,
+// any trailing elements of the SEQUENCE that do not have matching
+// fields in val will not be included in rest, as these are considered
+// valid elements of the SEQUENCE and not trailing data.
+//
+// An ASN.1 INTEGER can be written to an int, int32, int64,
+// or *big.Int (from the math/big package).
+// If the encoded value does not fit in the Go type,
+// Unmarshal returns a parse error.
+//
+// An ASN.1 BIT STRING can be written to a BitString.
+//
+// An ASN.1 OCTET STRING can be written to a []byte.
+//
+// An ASN.1 OBJECT IDENTIFIER can be written to an
+// ObjectIdentifier.
+//
+// An ASN.1 ENUMERATED can be written to an Enumerated.
+//
+// An ASN.1 UTCTIME or GENERALIZEDTIME can be written to a time.Time.
+//
+// An ASN.1 PrintableString, IA5String, or NumericString can be written to a string.
+//
+// Any of the above ASN.1 values can be written to an interface{}.
+// The value stored in the interface has the corresponding Go type.
+// For integers, that type is int64.
+//
+// An ASN.1 SEQUENCE OF x or SET OF x can be written
+// to a slice if an x can be written to the slice's element type.
+//
+// An ASN.1 SEQUENCE or SET can be written to a struct
+// if each of the elements in the sequence can be
+// written to the corresponding element in the struct.
+//
+// The following tags on struct fields have special meaning to Unmarshal:
+//
+//	application specifies that an APPLICATION tag is used
+//	private     specifies that a PRIVATE tag is used
+//	default:x   sets the default value for optional integer fields (only used if optional is also present)
+//	explicit    specifies that an additional, explicit tag wraps the implicit one
+//	optional    marks the field as ASN.1 OPTIONAL
+//	set         causes a SET, rather than a SEQUENCE type to be expected
+//	tag:x       specifies the ASN.1 tag number; implies ASN.1 CONTEXT SPECIFIC
+//
+// When decoding an ASN.1 value with an IMPLICIT tag into a string field,
+// Unmarshal will default to a PrintableString, which doesn't support
+// characters such as '@' and '&'. To force other encodings, use the following
+// tags:
+//
+//	ia5     causes strings to be unmarshaled as ASN.1 IA5String values
+//	numeric causes strings to be unmarshaled as ASN.1 NumericString values
+//	utf8    causes strings to be unmarshaled as ASN.1 UTF8String values
+//
+// If the type of the first field of a structure is RawContent then the raw
+// ASN1 contents of the struct will be stored in it.
+//
+// If the name of a slice type ends with "SET" then it's treated as if
+// the "set" tag was set on it. This results in interpreting the type as a
+// SET OF x rather than a SEQUENCE OF x. This can be used with nested slices
+// where a struct tag cannot be given.
+//
+// Other ASN.1 types are not supported; if it encounters them,
+// Unmarshal returns a parse error.
+func Unmarshal(b []byte, val any) (rest []byte, err error) {
+	return UnmarshalWithParams(b, val, "")
+}
+
+// An invalidUnmarshalError describes an invalid argument passed to Unmarshal.
+// (The argument to Unmarshal must be a non-nil pointer.)
+type invalidUnmarshalError struct {
+	Type reflect.Type
+}
+
+func (e *invalidUnmarshalError) Error() string {
+	if e.Type == nil {
+		return "asn1: Unmarshal recipient value is nil"
+	}
+
+	if e.Type.Kind() != reflect.Pointer {
+		return "asn1: Unmarshal recipient value is non-pointer " + e.Type.String()
+	}
+	return "asn1: Unmarshal recipient value is nil " + e.Type.String()
+}
+
+// UnmarshalWithParams allows field parameters to be specified for the
+// top-level element. The form of the params is the same as the field tags.
+func UnmarshalWithParams(b []byte, val any, params string) (rest []byte, err error) {
+	v := reflect.ValueOf(val)
+	if v.Kind() != reflect.Pointer || v.IsNil() {
+		return nil, &invalidUnmarshalError{reflect.TypeOf(val)}
+	}
+	offset, err := parseField(v.Elem(), b, 0, parseFieldParameters(params))
+	if err != nil {
+		return nil, err
+	}
+	return b[offset:], nil
+}
diff --git a/src/encoding/asn1/asn1_test.go b/src/encoding/asn1/asn1_test.go
new file mode 100644
index 0000000..b1e05b9
--- /dev/null
+++ b/src/encoding/asn1/asn1_test.go
@@ -0,0 +1,1166 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package asn1
+
+import (
+	"bytes"
+	"encoding/hex"
+	"fmt"
+	"math"
+	"math/big"
+	"reflect"
+	"strings"
+	"testing"
+	"time"
+)
+
+type boolTest struct {
+	in  []byte
+	ok  bool
+	out bool
+}
+
+var boolTestData = []boolTest{
+	{[]byte{0x00}, true, false},
+	{[]byte{0xff}, true, true},
+	{[]byte{0x00, 0x00}, false, false},
+	{[]byte{0xff, 0xff}, false, false},
+	{[]byte{0x01}, false, false},
+}
+
+func TestParseBool(t *testing.T) {
+	for i, test := range boolTestData {
+		ret, err := parseBool(test.in)
+		if (err == nil) != test.ok {
+			t.Errorf("#%d: Incorrect error result (did fail? %v, expected: %v)", i, err == nil, test.ok)
+		}
+		if test.ok && ret != test.out {
+			t.Errorf("#%d: Bad result: %v (expected %v)", i, ret, test.out)
+		}
+	}
+}
+
+type int64Test struct {
+	in  []byte
+	ok  bool
+	out int64
+}
+
+var int64TestData = []int64Test{
+	{[]byte{0x00}, true, 0},
+	{[]byte{0x7f}, true, 127},
+	{[]byte{0x00, 0x80}, true, 128},
+	{[]byte{0x01, 0x00}, true, 256},
+	{[]byte{0x80}, true, -128},
+	{[]byte{0xff, 0x7f}, true, -129},
+	{[]byte{0xff}, true, -1},
+	{[]byte{0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, true, -9223372036854775808},
+	{[]byte{0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, false, 0},
+	{[]byte{}, false, 0},
+	{[]byte{0x00, 0x7f}, false, 0},
+	{[]byte{0xff, 0xf0}, false, 0},
+}
+
+func TestParseInt64(t *testing.T) {
+	for i, test := range int64TestData {
+		ret, err := parseInt64(test.in)
+		if (err == nil) != test.ok {
+			t.Errorf("#%d: Incorrect error result (did fail? %v, expected: %v)", i, err == nil, test.ok)
+		}
+		if test.ok && ret != test.out {
+			t.Errorf("#%d: Bad result: %v (expected %v)", i, ret, test.out)
+		}
+	}
+}
+
+type int32Test struct {
+	in  []byte
+	ok  bool
+	out int32
+}
+
+var int32TestData = []int32Test{
+	{[]byte{0x00}, true, 0},
+	{[]byte{0x7f}, true, 127},
+	{[]byte{0x00, 0x80}, true, 128},
+	{[]byte{0x01, 0x00}, true, 256},
+	{[]byte{0x80}, true, -128},
+	{[]byte{0xff, 0x7f}, true, -129},
+	{[]byte{0xff}, true, -1},
+	{[]byte{0x80, 0x00, 0x00, 0x00}, true, -2147483648},
+	{[]byte{0x80, 0x00, 0x00, 0x00, 0x00}, false, 0},
+	{[]byte{}, false, 0},
+	{[]byte{0x00, 0x7f}, false, 0},
+	{[]byte{0xff, 0xf0}, false, 0},
+}
+
+func TestParseInt32(t *testing.T) {
+	for i, test := range int32TestData {
+		ret, err := parseInt32(test.in)
+		if (err == nil) != test.ok {
+			t.Errorf("#%d: Incorrect error result (did fail? %v, expected: %v)", i, err == nil, test.ok)
+		}
+		if test.ok && int32(ret) != test.out {
+			t.Errorf("#%d: Bad result: %v (expected %v)", i, ret, test.out)
+		}
+	}
+}
+
+var bigIntTests = []struct {
+	in     []byte
+	ok     bool
+	base10 string
+}{
+	{[]byte{0xff}, true, "-1"},
+	{[]byte{0x00}, true, "0"},
+	{[]byte{0x01}, true, "1"},
+	{[]byte{0x00, 0xff}, true, "255"},
+	{[]byte{0xff, 0x00}, true, "-256"},
+	{[]byte{0x01, 0x00}, true, "256"},
+	{[]byte{}, false, ""},
+	{[]byte{0x00, 0x7f}, false, ""},
+	{[]byte{0xff, 0xf0}, false, ""},
+}
+
+func TestParseBigInt(t *testing.T) {
+	for i, test := range bigIntTests {
+		ret, err := parseBigInt(test.in)
+		if (err == nil) != test.ok {
+			t.Errorf("#%d: Incorrect error result (did fail? %v, expected: %v)", i, err == nil, test.ok)
+		}
+		if test.ok {
+			if ret.String() != test.base10 {
+				t.Errorf("#%d: bad result from %x, got %s want %s", i, test.in, ret.String(), test.base10)
+			}
+			e, err := makeBigInt(ret)
+			if err != nil {
+				t.Errorf("%d: err=%q", i, err)
+				continue
+			}
+			result := make([]byte, e.Len())
+			e.Encode(result)
+			if !bytes.Equal(result, test.in) {
+				t.Errorf("#%d: got %x from marshaling %s, want %x", i, result, ret, test.in)
+			}
+		}
+	}
+}
+
+type bitStringTest struct {
+	in        []byte
+	ok        bool
+	out       []byte
+	bitLength int
+}
+
+var bitStringTestData = []bitStringTest{
+	{[]byte{}, false, []byte{}, 0},
+	{[]byte{0x00}, true, []byte{}, 0},
+	{[]byte{0x07, 0x00}, true, []byte{0x00}, 1},
+	{[]byte{0x07, 0x01}, false, []byte{}, 0},
+	{[]byte{0x07, 0x40}, false, []byte{}, 0},
+	{[]byte{0x08, 0x00}, false, []byte{}, 0},
+}
+
+func TestBitString(t *testing.T) {
+	for i, test := range bitStringTestData {
+		ret, err := parseBitString(test.in)
+		if (err == nil) != test.ok {
+			t.Errorf("#%d: Incorrect error result (did fail? %v, expected: %v)", i, err == nil, test.ok)
+		}
+		if err == nil {
+			if test.bitLength != ret.BitLength || !bytes.Equal(ret.Bytes, test.out) {
+				t.Errorf("#%d: Bad result: %v (expected %v %v)", i, ret, test.out, test.bitLength)
+			}
+		}
+	}
+}
+
+func TestBitStringAt(t *testing.T) {
+	bs := BitString{[]byte{0x82, 0x40}, 16}
+	if bs.At(0) != 1 {
+		t.Error("#1: Failed")
+	}
+	if bs.At(1) != 0 {
+		t.Error("#2: Failed")
+	}
+	if bs.At(6) != 1 {
+		t.Error("#3: Failed")
+	}
+	if bs.At(9) != 1 {
+		t.Error("#4: Failed")
+	}
+	if bs.At(-1) != 0 {
+		t.Error("#5: Failed")
+	}
+	if bs.At(17) != 0 {
+		t.Error("#6: Failed")
+	}
+}
+
+type bitStringRightAlignTest struct {
+	in    []byte
+	inlen int
+	out   []byte
+}
+
+var bitStringRightAlignTests = []bitStringRightAlignTest{
+	{[]byte{0x80}, 1, []byte{0x01}},
+	{[]byte{0x80, 0x80}, 9, []byte{0x01, 0x01}},
+	{[]byte{}, 0, []byte{}},
+	{[]byte{0xce}, 8, []byte{0xce}},
+	{[]byte{0xce, 0x47}, 16, []byte{0xce, 0x47}},
+	{[]byte{0x34, 0x50}, 12, []byte{0x03, 0x45}},
+}
+
+func TestBitStringRightAlign(t *testing.T) {
+	for i, test := range bitStringRightAlignTests {
+		bs := BitString{test.in, test.inlen}
+		out := bs.RightAlign()
+		if !bytes.Equal(out, test.out) {
+			t.Errorf("#%d got: %x want: %x", i, out, test.out)
+		}
+	}
+}
+
+type objectIdentifierTest struct {
+	in  []byte
+	ok  bool
+	out ObjectIdentifier // has base type[]int
+}
+
+var objectIdentifierTestData = []objectIdentifierTest{
+	{[]byte{}, false, []int{}},
+	{[]byte{85}, true, []int{2, 5}},
+	{[]byte{85, 0x02}, true, []int{2, 5, 2}},
+	{[]byte{85, 0x02, 0xc0, 0x00}, true, []int{2, 5, 2, 0x2000}},
+	{[]byte{0x81, 0x34, 0x03}, true, []int{2, 100, 3}},
+	{[]byte{85, 0x02, 0xc0, 0x80, 0x80, 0x80, 0x80}, false, []int{}},
+}
+
+func TestObjectIdentifier(t *testing.T) {
+	for i, test := range objectIdentifierTestData {
+		ret, err := parseObjectIdentifier(test.in)
+		if (err == nil) != test.ok {
+			t.Errorf("#%d: Incorrect error result (did fail? %v, expected: %v)", i, err == nil, test.ok)
+		}
+		if err == nil {
+			if !reflect.DeepEqual(test.out, ret) {
+				t.Errorf("#%d: Bad result: %v (expected %v)", i, ret, test.out)
+			}
+		}
+	}
+
+	if s := ObjectIdentifier([]int{1, 2, 3, 4}).String(); s != "1.2.3.4" {
+		t.Errorf("bad ObjectIdentifier.String(). Got %s, want 1.2.3.4", s)
+	}
+}
+
+type timeTest struct {
+	in  string
+	ok  bool
+	out time.Time
+}
+
+var utcTestData = []timeTest{
+	{"910506164540-0700", true, time.Date(1991, 05, 06, 16, 45, 40, 0, time.FixedZone("", -7*60*60))},
+	{"910506164540+0730", true, time.Date(1991, 05, 06, 16, 45, 40, 0, time.FixedZone("", 7*60*60+30*60))},
+	{"910506234540Z", true, time.Date(1991, 05, 06, 23, 45, 40, 0, time.UTC)},
+	{"9105062345Z", true, time.Date(1991, 05, 06, 23, 45, 0, 0, time.UTC)},
+	{"5105062345Z", true, time.Date(1951, 05, 06, 23, 45, 0, 0, time.UTC)},
+	{"a10506234540Z", false, time.Time{}},
+	{"91a506234540Z", false, time.Time{}},
+	{"9105a6234540Z", false, time.Time{}},
+	{"910506a34540Z", false, time.Time{}},
+	{"910506334a40Z", false, time.Time{}},
+	{"91050633444aZ", false, time.Time{}},
+	{"910506334461Z", false, time.Time{}},
+	{"910506334400Za", false, time.Time{}},
+	/* These are invalid times. However, the time package normalises times
+	 * and they were accepted in some versions. See #11134. */
+	{"000100000000Z", false, time.Time{}},
+	{"101302030405Z", false, time.Time{}},
+	{"100002030405Z", false, time.Time{}},
+	{"100100030405Z", false, time.Time{}},
+	{"100132030405Z", false, time.Time{}},
+	{"100231030405Z", false, time.Time{}},
+	{"100102240405Z", false, time.Time{}},
+	{"100102036005Z", false, time.Time{}},
+	{"100102030460Z", false, time.Time{}},
+	{"-100102030410Z", false, time.Time{}},
+	{"10-0102030410Z", false, time.Time{}},
+	{"10-0002030410Z", false, time.Time{}},
+	{"1001-02030410Z", false, time.Time{}},
+	{"100102-030410Z", false, time.Time{}},
+	{"10010203-0410Z", false, time.Time{}},
+	{"1001020304-10Z", false, time.Time{}},
+}
+
+func TestUTCTime(t *testing.T) {
+	for i, test := range utcTestData {
+		ret, err := parseUTCTime([]byte(test.in))
+		if err != nil {
+			if test.ok {
+				t.Errorf("#%d: parseUTCTime(%q) = error %v", i, test.in, err)
+			}
+			continue
+		}
+		if !test.ok {
+			t.Errorf("#%d: parseUTCTime(%q) succeeded, should have failed", i, test.in)
+			continue
+		}
+		const format = "Jan _2 15:04:05 -0700 2006" // ignore zone name, just offset
+		have := ret.Format(format)
+		want := test.out.Format(format)
+		if have != want {
+			t.Errorf("#%d: parseUTCTime(%q) = %s, want %s", i, test.in, have, want)
+		}
+	}
+}
+
+var generalizedTimeTestData = []timeTest{
+	{"20100102030405Z", true, time.Date(2010, 01, 02, 03, 04, 05, 0, time.UTC)},
+	{"20100102030405", false, time.Time{}},
+	{"20100102030405+0607", true, time.Date(2010, 01, 02, 03, 04, 05, 0, time.FixedZone("", 6*60*60+7*60))},
+	{"20100102030405-0607", true, time.Date(2010, 01, 02, 03, 04, 05, 0, time.FixedZone("", -6*60*60-7*60))},
+	/* These are invalid times. However, the time package normalises times
+	 * and they were accepted in some versions. See #11134. */
+	{"00000100000000Z", false, time.Time{}},
+	{"20101302030405Z", false, time.Time{}},
+	{"20100002030405Z", false, time.Time{}},
+	{"20100100030405Z", false, time.Time{}},
+	{"20100132030405Z", false, time.Time{}},
+	{"20100231030405Z", false, time.Time{}},
+	{"20100102240405Z", false, time.Time{}},
+	{"20100102036005Z", false, time.Time{}},
+	{"20100102030460Z", false, time.Time{}},
+	{"-20100102030410Z", false, time.Time{}},
+	{"2010-0102030410Z", false, time.Time{}},
+	{"2010-0002030410Z", false, time.Time{}},
+	{"201001-02030410Z", false, time.Time{}},
+	{"20100102-030410Z", false, time.Time{}},
+	{"2010010203-0410Z", false, time.Time{}},
+	{"201001020304-10Z", false, time.Time{}},
+}
+
+func TestGeneralizedTime(t *testing.T) {
+	for i, test := range generalizedTimeTestData {
+		ret, err := parseGeneralizedTime([]byte(test.in))
+		if (err == nil) != test.ok {
+			t.Errorf("#%d: Incorrect error result (did fail? %v, expected: %v)", i, err == nil, test.ok)
+		}
+		if err == nil {
+			if !reflect.DeepEqual(test.out, ret) {
+				t.Errorf("#%d: Bad result: %q → %v (expected %v)", i, test.in, ret, test.out)
+			}
+		}
+	}
+}
+
+type tagAndLengthTest struct {
+	in  []byte
+	ok  bool
+	out tagAndLength
+}
+
+var tagAndLengthData = []tagAndLengthTest{
+	{[]byte{0x80, 0x01}, true, tagAndLength{2, 0, 1, false}},
+	{[]byte{0xa0, 0x01}, true, tagAndLength{2, 0, 1, true}},
+	{[]byte{0x02, 0x00}, true, tagAndLength{0, 2, 0, false}},
+	{[]byte{0xfe, 0x00}, true, tagAndLength{3, 30, 0, true}},
+	{[]byte{0x1f, 0x1f, 0x00}, true, tagAndLength{0, 31, 0, false}},
+	{[]byte{0x1f, 0x81, 0x00, 0x00}, true, tagAndLength{0, 128, 0, false}},
+	{[]byte{0x1f, 0x81, 0x80, 0x01, 0x00}, true, tagAndLength{0, 0x4001, 0, false}},
+	{[]byte{0x00, 0x81, 0x80}, true, tagAndLength{0, 0, 128, false}},
+	{[]byte{0x00, 0x82, 0x01, 0x00}, true, tagAndLength{0, 0, 256, false}},
+	{[]byte{0x00, 0x83, 0x01, 0x00}, false, tagAndLength{}},
+	{[]byte{0x1f, 0x85}, false, tagAndLength{}},
+	{[]byte{0x30, 0x80}, false, tagAndLength{}},
+	// Superfluous zeros in the length should be an error.
+	{[]byte{0xa0, 0x82, 0x00, 0xff}, false, tagAndLength{}},
+	// Lengths up to the maximum size of an int should work.
+	{[]byte{0xa0, 0x84, 0x7f, 0xff, 0xff, 0xff}, true, tagAndLength{2, 0, 0x7fffffff, true}},
+	// Lengths that would overflow an int should be rejected.
+	{[]byte{0xa0, 0x84, 0x80, 0x00, 0x00, 0x00}, false, tagAndLength{}},
+	// Long length form may not be used for lengths that fit in short form.
+	{[]byte{0xa0, 0x81, 0x7f}, false, tagAndLength{}},
+	// Tag numbers which would overflow int32 are rejected. (The value below is 2^31.)
+	{[]byte{0x1f, 0x88, 0x80, 0x80, 0x80, 0x00, 0x00}, false, tagAndLength{}},
+	// Tag numbers that fit in an int32 are valid. (The value below is 2^31 - 1.)
+	{[]byte{0x1f, 0x87, 0xFF, 0xFF, 0xFF, 0x7F, 0x00}, true, tagAndLength{tag: math.MaxInt32}},
+	// Long tag number form may not be used for tags that fit in short form.
+	{[]byte{0x1f, 0x1e, 0x00}, false, tagAndLength{}},
+}
+
+func TestParseTagAndLength(t *testing.T) {
+	for i, test := range tagAndLengthData {
+		tagAndLength, _, err := parseTagAndLength(test.in, 0)
+		if (err == nil) != test.ok {
+			t.Errorf("#%d: Incorrect error result (did pass? %v, expected: %v)", i, err == nil, test.ok)
+		}
+		if err == nil && !reflect.DeepEqual(test.out, tagAndLength) {
+			t.Errorf("#%d: Bad result: %v (expected %v)", i, tagAndLength, test.out)
+		}
+	}
+}
+
+type parseFieldParametersTest struct {
+	in  string
+	out fieldParameters
+}
+
+func newInt(n int) *int { return &n }
+
+func newInt64(n int64) *int64 { return &n }
+
+func newString(s string) *string { return &s }
+
+func newBool(b bool) *bool { return &b }
+
+var parseFieldParametersTestData []parseFieldParametersTest = []parseFieldParametersTest{
+	{"", fieldParameters{}},
+	{"ia5", fieldParameters{stringType: TagIA5String}},
+	{"generalized", fieldParameters{timeType: TagGeneralizedTime}},
+	{"utc", fieldParameters{timeType: TagUTCTime}},
+	{"printable", fieldParameters{stringType: TagPrintableString}},
+	{"numeric", fieldParameters{stringType: TagNumericString}},
+	{"optional", fieldParameters{optional: true}},
+	{"explicit", fieldParameters{explicit: true, tag: new(int)}},
+	{"application", fieldParameters{application: true, tag: new(int)}},
+	{"private", fieldParameters{private: true, tag: new(int)}},
+	{"optional,explicit", fieldParameters{optional: true, explicit: true, tag: new(int)}},
+	{"default:42", fieldParameters{defaultValue: newInt64(42)}},
+	{"tag:17", fieldParameters{tag: newInt(17)}},
+	{"optional,explicit,default:42,tag:17", fieldParameters{optional: true, explicit: true, defaultValue: newInt64(42), tag: newInt(17)}},
+	{"optional,explicit,default:42,tag:17,rubbish1", fieldParameters{optional: true, explicit: true, application: false, defaultValue: newInt64(42), tag: newInt(17), stringType: 0, timeType: 0, set: false, omitEmpty: false}},
+	{"set", fieldParameters{set: true}},
+}
+
+func TestParseFieldParameters(t *testing.T) {
+	for i, test := range parseFieldParametersTestData {
+		f := parseFieldParameters(test.in)
+		if !reflect.DeepEqual(f, test.out) {
+			t.Errorf("#%d: Bad result: %v (expected %v)", i, f, test.out)
+		}
+	}
+}
+
+type TestObjectIdentifierStruct struct {
+	OID ObjectIdentifier
+}
+
+type TestContextSpecificTags struct {
+	A int `asn1:"tag:1"`
+}
+
+type TestContextSpecificTags2 struct {
+	A int `asn1:"explicit,tag:1"`
+	B int
+}
+
+type TestContextSpecificTags3 struct {
+	S string `asn1:"tag:1,utf8"`
+}
+
+type TestElementsAfterString struct {
+	S    string
+	A, B int
+}
+
+type TestBigInt struct {
+	X *big.Int
+}
+
+type TestSet struct {
+	Ints []int `asn1:"set"`
+}
+
+var unmarshalTestData = []struct {
+	in  []byte
+	out any
+}{
+	{[]byte{0x02, 0x01, 0x42}, newInt(0x42)},
+	{[]byte{0x05, 0x00}, &RawValue{0, 5, false, []byte{}, []byte{0x05, 0x00}}},
+	{[]byte{0x30, 0x08, 0x06, 0x06, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d}, &TestObjectIdentifierStruct{[]int{1, 2, 840, 113549}}},
+	{[]byte{0x03, 0x04, 0x06, 0x6e, 0x5d, 0xc0}, &BitString{[]byte{110, 93, 192}, 18}},
+	{[]byte{0x30, 0x09, 0x02, 0x01, 0x01, 0x02, 0x01, 0x02, 0x02, 0x01, 0x03}, &[]int{1, 2, 3}},
+	{[]byte{0x02, 0x01, 0x10}, newInt(16)},
+	{[]byte{0x13, 0x04, 't', 'e', 's', 't'}, newString("test")},
+	{[]byte{0x16, 0x04, 't', 'e', 's', 't'}, newString("test")},
+	// Ampersand is allowed in PrintableString due to mistakes by major CAs.
+	{[]byte{0x13, 0x05, 't', 'e', 's', 't', '&'}, newString("test&")},
+	{[]byte{0x16, 0x04, 't', 'e', 's', 't'}, &RawValue{0, 22, false, []byte("test"), []byte("\x16\x04test")}},
+	{[]byte{0x04, 0x04, 1, 2, 3, 4}, &RawValue{0, 4, false, []byte{1, 2, 3, 4}, []byte{4, 4, 1, 2, 3, 4}}},
+	{[]byte{0x30, 0x03, 0x81, 0x01, 0x01}, &TestContextSpecificTags{1}},
+	{[]byte{0x30, 0x08, 0xa1, 0x03, 0x02, 0x01, 0x01, 0x02, 0x01, 0x02}, &TestContextSpecificTags2{1, 2}},
+	{[]byte{0x30, 0x03, 0x81, 0x01, '@'}, &TestContextSpecificTags3{"@"}},
+	{[]byte{0x01, 0x01, 0x00}, newBool(false)},
+	{[]byte{0x01, 0x01, 0xff}, newBool(true)},
+	{[]byte{0x30, 0x0b, 0x13, 0x03, 0x66, 0x6f, 0x6f, 0x02, 0x01, 0x22, 0x02, 0x01, 0x33}, &TestElementsAfterString{"foo", 0x22, 0x33}},
+	{[]byte{0x30, 0x05, 0x02, 0x03, 0x12, 0x34, 0x56}, &TestBigInt{big.NewInt(0x123456)}},
+	{[]byte{0x30, 0x0b, 0x31, 0x09, 0x02, 0x01, 0x01, 0x02, 0x01, 0x02, 0x02, 0x01, 0x03}, &TestSet{Ints: []int{1, 2, 3}}},
+	{[]byte{0x12, 0x0b, '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', ' '}, newString("0123456789 ")},
+}
+
+func TestUnmarshal(t *testing.T) {
+	for i, test := range unmarshalTestData {
+		pv := reflect.New(reflect.TypeOf(test.out).Elem())
+		val := pv.Interface()
+		_, err := Unmarshal(test.in, val)
+		if err != nil {
+			t.Errorf("Unmarshal failed at index %d %v", i, err)
+		}
+		if !reflect.DeepEqual(val, test.out) {
+			t.Errorf("#%d:\nhave %#v\nwant %#v", i, val, test.out)
+		}
+	}
+}
+
+func TestUnmarshalWithNilOrNonPointer(t *testing.T) {
+	tests := []struct {
+		b    []byte
+		v    any
+		want string
+	}{
+		{b: []byte{0x05, 0x00}, v: nil, want: "asn1: Unmarshal recipient value is nil"},
+		{b: []byte{0x05, 0x00}, v: RawValue{}, want: "asn1: Unmarshal recipient value is non-pointer asn1.RawValue"},
+		{b: []byte{0x05, 0x00}, v: (*RawValue)(nil), want: "asn1: Unmarshal recipient value is nil *asn1.RawValue"},
+	}
+
+	for _, test := range tests {
+		_, err := Unmarshal(test.b, test.v)
+		if err == nil {
+			t.Errorf("Unmarshal expecting error, got nil")
+			continue
+		}
+		if g, w := err.Error(), test.want; g != w {
+			t.Errorf("InvalidUnmarshalError mismatch\nGot:  %q\nWant: %q", g, w)
+		}
+	}
+}
+
+type Certificate struct {
+	TBSCertificate     TBSCertificate
+	SignatureAlgorithm AlgorithmIdentifier
+	SignatureValue     BitString
+}
+
+type TBSCertificate struct {
+	Version            int `asn1:"optional,explicit,default:0,tag:0"`
+	SerialNumber       RawValue
+	SignatureAlgorithm AlgorithmIdentifier
+	Issuer             RDNSequence
+	Validity           Validity
+	Subject            RDNSequence
+	PublicKey          PublicKeyInfo
+}
+
+type AlgorithmIdentifier struct {
+	Algorithm ObjectIdentifier
+}
+
+type RDNSequence []RelativeDistinguishedNameSET
+
+type RelativeDistinguishedNameSET []AttributeTypeAndValue
+
+type AttributeTypeAndValue struct {
+	Type  ObjectIdentifier
+	Value any
+}
+
+type Validity struct {
+	NotBefore, NotAfter time.Time
+}
+
+type PublicKeyInfo struct {
+	Algorithm AlgorithmIdentifier
+	PublicKey BitString
+}
+
+func TestCertificate(t *testing.T) {
+	// This is a minimal, self-signed certificate that should parse correctly.
+	var cert Certificate
+	if _, err := Unmarshal(derEncodedSelfSignedCertBytes, &cert); err != nil {
+		t.Errorf("Unmarshal failed: %v", err)
+	}
+	if !reflect.DeepEqual(cert, derEncodedSelfSignedCert) {
+		t.Errorf("Bad result:\ngot: %+v\nwant: %+v", cert, derEncodedSelfSignedCert)
+	}
+}
+
+func TestCertificateWithNUL(t *testing.T) {
+	// This is the paypal NUL-hack certificate. It should fail to parse because
+	// NUL isn't a permitted character in a PrintableString.
+
+	var cert Certificate
+	if _, err := Unmarshal(derEncodedPaypalNULCertBytes, &cert); err == nil {
+		t.Error("Unmarshal succeeded, should not have")
+	}
+}
+
+type rawStructTest struct {
+	Raw RawContent
+	A   int
+}
+
+func TestRawStructs(t *testing.T) {
+	var s rawStructTest
+	input := []byte{0x30, 0x03, 0x02, 0x01, 0x50}
+
+	rest, err := Unmarshal(input, &s)
+	if len(rest) != 0 {
+		t.Errorf("incomplete parse: %x", rest)
+		return
+	}
+	if err != nil {
+		t.Error(err)
+		return
+	}
+	if s.A != 0x50 {
+		t.Errorf("bad value for A: got %d want %d", s.A, 0x50)
+	}
+	if !bytes.Equal([]byte(s.Raw), input) {
+		t.Errorf("bad value for Raw: got %x want %x", s.Raw, input)
+	}
+}
+
+type oiEqualTest struct {
+	first  ObjectIdentifier
+	second ObjectIdentifier
+	same   bool
+}
+
+var oiEqualTests = []oiEqualTest{
+	{
+		ObjectIdentifier{1, 2, 3},
+		ObjectIdentifier{1, 2, 3},
+		true,
+	},
+	{
+		ObjectIdentifier{1},
+		ObjectIdentifier{1, 2, 3},
+		false,
+	},
+	{
+		ObjectIdentifier{1, 2, 3},
+		ObjectIdentifier{10, 11, 12},
+		false,
+	},
+}
+
+func TestObjectIdentifierEqual(t *testing.T) {
+	for _, o := range oiEqualTests {
+		if s := o.first.Equal(o.second); s != o.same {
+			t.Errorf("ObjectIdentifier.Equal: got: %t want: %t", s, o.same)
+		}
+	}
+}
+
+var derEncodedSelfSignedCert = Certificate{
+	TBSCertificate: TBSCertificate{
+		Version:            0,
+		SerialNumber:       RawValue{Class: 0, Tag: 2, IsCompound: false, Bytes: []uint8{0x0, 0x8c, 0xc3, 0x37, 0x92, 0x10, 0xec, 0x2c, 0x98}, FullBytes: []byte{2, 9, 0x0, 0x8c, 0xc3, 0x37, 0x92, 0x10, 0xec, 0x2c, 0x98}},
+		SignatureAlgorithm: AlgorithmIdentifier{Algorithm: ObjectIdentifier{1, 2, 840, 113549, 1, 1, 5}},
+		Issuer: RDNSequence{
+			RelativeDistinguishedNameSET{AttributeTypeAndValue{Type: ObjectIdentifier{2, 5, 4, 6}, Value: "XX"}},
+			RelativeDistinguishedNameSET{AttributeTypeAndValue{Type: ObjectIdentifier{2, 5, 4, 8}, Value: "Some-State"}},
+			RelativeDistinguishedNameSET{AttributeTypeAndValue{Type: ObjectIdentifier{2, 5, 4, 7}, Value: "City"}},
+			RelativeDistinguishedNameSET{AttributeTypeAndValue{Type: ObjectIdentifier{2, 5, 4, 10}, Value: "Internet Widgits Pty Ltd"}},
+			RelativeDistinguishedNameSET{AttributeTypeAndValue{Type: ObjectIdentifier{2, 5, 4, 3}, Value: "false.example.com"}},
+			RelativeDistinguishedNameSET{AttributeTypeAndValue{Type: ObjectIdentifier{1, 2, 840, 113549, 1, 9, 1}, Value: "false@example.com"}},
+		},
+		Validity: Validity{
+			NotBefore: time.Date(2009, 10, 8, 00, 25, 53, 0, time.UTC),
+			NotAfter:  time.Date(2010, 10, 8, 00, 25, 53, 0, time.UTC),
+		},
+		Subject: RDNSequence{
+			RelativeDistinguishedNameSET{AttributeTypeAndValue{Type: ObjectIdentifier{2, 5, 4, 6}, Value: "XX"}},
+			RelativeDistinguishedNameSET{AttributeTypeAndValue{Type: ObjectIdentifier{2, 5, 4, 8}, Value: "Some-State"}},
+			RelativeDistinguishedNameSET{AttributeTypeAndValue{Type: ObjectIdentifier{2, 5, 4, 7}, Value: "City"}},
+			RelativeDistinguishedNameSET{AttributeTypeAndValue{Type: ObjectIdentifier{2, 5, 4, 10}, Value: "Internet Widgits Pty Ltd"}},
+			RelativeDistinguishedNameSET{AttributeTypeAndValue{Type: ObjectIdentifier{2, 5, 4, 3}, Value: "false.example.com"}},
+			RelativeDistinguishedNameSET{AttributeTypeAndValue{Type: ObjectIdentifier{1, 2, 840, 113549, 1, 9, 1}, Value: "false@example.com"}},
+		},
+		PublicKey: PublicKeyInfo{
+			Algorithm: AlgorithmIdentifier{Algorithm: ObjectIdentifier{1, 2, 840, 113549, 1, 1, 1}},
+			PublicKey: BitString{
+				Bytes: []uint8{
+					0x30, 0x48, 0x2, 0x41, 0x0, 0xcd, 0xb7,
+					0x63, 0x9c, 0x32, 0x78, 0xf0, 0x6, 0xaa, 0x27, 0x7f, 0x6e, 0xaf, 0x42,
+					0x90, 0x2b, 0x59, 0x2d, 0x8c, 0xbc, 0xbe, 0x38, 0xa1, 0xc9, 0x2b, 0xa4,
+					0x69, 0x5a, 0x33, 0x1b, 0x1d, 0xea, 0xde, 0xad, 0xd8, 0xe9, 0xa5, 0xc2,
+					0x7e, 0x8c, 0x4c, 0x2f, 0xd0, 0xa8, 0x88, 0x96, 0x57, 0x72, 0x2a, 0x4f,
+					0x2a, 0xf7, 0x58, 0x9c, 0xf2, 0xc7, 0x70, 0x45, 0xdc, 0x8f, 0xde, 0xec,
+					0x35, 0x7d, 0x2, 0x3, 0x1, 0x0, 0x1,
+				},
+				BitLength: 592,
+			},
+		},
+	},
+	SignatureAlgorithm: AlgorithmIdentifier{Algorithm: ObjectIdentifier{1, 2, 840, 113549, 1, 1, 5}},
+	SignatureValue: BitString{
+		Bytes: []uint8{
+			0xa6, 0x7b, 0x6, 0xec, 0x5e, 0xce,
+			0x92, 0x77, 0x2c, 0xa4, 0x13, 0xcb, 0xa3, 0xca, 0x12, 0x56, 0x8f, 0xdc, 0x6c,
+			0x7b, 0x45, 0x11, 0xcd, 0x40, 0xa7, 0xf6, 0x59, 0x98, 0x4, 0x2, 0xdf, 0x2b,
+			0x99, 0x8b, 0xb9, 0xa4, 0xa8, 0xcb, 0xeb, 0x34, 0xc0, 0xf0, 0xa7, 0x8c, 0xf8,
+			0xd9, 0x1e, 0xde, 0x14, 0xa5, 0xed, 0x76, 0xbf, 0x11, 0x6f, 0xe3, 0x60, 0xaa,
+			0xfa, 0x88, 0x21, 0x49, 0x4, 0x35,
+		},
+		BitLength: 512,
+	},
+}
+
+var derEncodedSelfSignedCertBytes = []byte{
+	0x30, 0x82, 0x02, 0x18, 0x30,
+	0x82, 0x01, 0xc2, 0x02, 0x09, 0x00, 0x8c, 0xc3, 0x37, 0x92, 0x10, 0xec, 0x2c,
+	0x98, 0x30, 0x0d, 0x06, 0x09, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x01,
+	0x05, 0x05, 0x00, 0x30, 0x81, 0x92, 0x31, 0x0b, 0x30, 0x09, 0x06, 0x03, 0x55,
+	0x04, 0x06, 0x13, 0x02, 0x58, 0x58, 0x31, 0x13, 0x30, 0x11, 0x06, 0x03, 0x55,
+	0x04, 0x08, 0x13, 0x0a, 0x53, 0x6f, 0x6d, 0x65, 0x2d, 0x53, 0x74, 0x61, 0x74,
+	0x65, 0x31, 0x0d, 0x30, 0x0b, 0x06, 0x03, 0x55, 0x04, 0x07, 0x13, 0x04, 0x43,
+	0x69, 0x74, 0x79, 0x31, 0x21, 0x30, 0x1f, 0x06, 0x03, 0x55, 0x04, 0x0a, 0x13,
+	0x18, 0x49, 0x6e, 0x74, 0x65, 0x72, 0x6e, 0x65, 0x74, 0x20, 0x57, 0x69, 0x64,
+	0x67, 0x69, 0x74, 0x73, 0x20, 0x50, 0x74, 0x79, 0x20, 0x4c, 0x74, 0x64, 0x31,
+	0x1a, 0x30, 0x18, 0x06, 0x03, 0x55, 0x04, 0x03, 0x13, 0x11, 0x66, 0x61, 0x6c,
+	0x73, 0x65, 0x2e, 0x65, 0x78, 0x61, 0x6d, 0x70, 0x6c, 0x65, 0x2e, 0x63, 0x6f,
+	0x6d, 0x31, 0x20, 0x30, 0x1e, 0x06, 0x09, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d,
+	0x01, 0x09, 0x01, 0x16, 0x11, 0x66, 0x61, 0x6c, 0x73, 0x65, 0x40, 0x65, 0x78,
+	0x61, 0x6d, 0x70, 0x6c, 0x65, 0x2e, 0x63, 0x6f, 0x6d, 0x30, 0x1e, 0x17, 0x0d,
+	0x30, 0x39, 0x31, 0x30, 0x30, 0x38, 0x30, 0x30, 0x32, 0x35, 0x35, 0x33, 0x5a,
+	0x17, 0x0d, 0x31, 0x30, 0x31, 0x30, 0x30, 0x38, 0x30, 0x30, 0x32, 0x35, 0x35,
+	0x33, 0x5a, 0x30, 0x81, 0x92, 0x31, 0x0b, 0x30, 0x09, 0x06, 0x03, 0x55, 0x04,
+	0x06, 0x13, 0x02, 0x58, 0x58, 0x31, 0x13, 0x30, 0x11, 0x06, 0x03, 0x55, 0x04,
+	0x08, 0x13, 0x0a, 0x53, 0x6f, 0x6d, 0x65, 0x2d, 0x53, 0x74, 0x61, 0x74, 0x65,
+	0x31, 0x0d, 0x30, 0x0b, 0x06, 0x03, 0x55, 0x04, 0x07, 0x13, 0x04, 0x43, 0x69,
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+	0x05, 0x00, 0x03, 0x81, 0x81, 0x00, 0x68, 0xee, 0x79, 0x97, 0x97, 0xdd, 0x3b,
+	0xef, 0x16, 0x6a, 0x06, 0xf2, 0x14, 0x9a, 0x6e, 0xcd, 0x9e, 0x12, 0xf7, 0xaa,
+	0x83, 0x10, 0xbd, 0xd1, 0x7c, 0x98, 0xfa, 0xc7, 0xae, 0xd4, 0x0e, 0x2c, 0x9e,
+	0x38, 0x05, 0x9d, 0x52, 0x60, 0xa9, 0x99, 0x0a, 0x81, 0xb4, 0x98, 0x90, 0x1d,
+	0xae, 0xbb, 0x4a, 0xd7, 0xb9, 0xdc, 0x88, 0x9e, 0x37, 0x78, 0x41, 0x5b, 0xf7,
+	0x82, 0xa5, 0xf2, 0xba, 0x41, 0x25, 0x5a, 0x90, 0x1a, 0x1e, 0x45, 0x38, 0xa1,
+	0x52, 0x58, 0x75, 0x94, 0x26, 0x44, 0xfb, 0x20, 0x07, 0xba, 0x44, 0xcc, 0xe5,
+	0x4a, 0x2d, 0x72, 0x3f, 0x98, 0x47, 0xf6, 0x26, 0xdc, 0x05, 0x46, 0x05, 0x07,
+	0x63, 0x21, 0xab, 0x46, 0x9b, 0x9c, 0x78, 0xd5, 0x54, 0x5b, 0x3d, 0x0c, 0x1e,
+	0xc8, 0x64, 0x8c, 0xb5, 0x50, 0x23, 0x82, 0x6f, 0xdb, 0xb8, 0x22, 0x1c, 0x43,
+	0x96, 0x07, 0xa8, 0xbb,
+}
+
+var stringSliceTestData = [][]string{
+	{"foo", "bar"},
+	{"foo", "\\bar"},
+	{"foo", "\"bar\""},
+	{"foo", "åäö"},
+}
+
+func TestStringSlice(t *testing.T) {
+	for _, test := range stringSliceTestData {
+		bs, err := Marshal(test)
+		if err != nil {
+			t.Error(err)
+		}
+
+		var res []string
+		_, err = Unmarshal(bs, &res)
+		if err != nil {
+			t.Error(err)
+		}
+
+		if fmt.Sprintf("%v", res) != fmt.Sprintf("%v", test) {
+			t.Errorf("incorrect marshal/unmarshal; %v != %v", res, test)
+		}
+	}
+}
+
+type explicitTaggedTimeTest struct {
+	Time time.Time `asn1:"explicit,tag:0"`
+}
+
+var explicitTaggedTimeTestData = []struct {
+	in  []byte
+	out explicitTaggedTimeTest
+}{
+	{[]byte{0x30, 0x11, 0xa0, 0xf, 0x17, 0xd, '9', '1', '0', '5', '0', '6', '1', '6', '4', '5', '4', '0', 'Z'},
+		explicitTaggedTimeTest{time.Date(1991, 05, 06, 16, 45, 40, 0, time.UTC)}},
+	{[]byte{0x30, 0x17, 0xa0, 0xf, 0x18, 0x13, '2', '0', '1', '0', '0', '1', '0', '2', '0', '3', '0', '4', '0', '5', '+', '0', '6', '0', '7'},
+		explicitTaggedTimeTest{time.Date(2010, 01, 02, 03, 04, 05, 0, time.FixedZone("", 6*60*60+7*60))}},
+}
+
+func TestExplicitTaggedTime(t *testing.T) {
+	// Test that a time.Time will match either tagUTCTime or
+	// tagGeneralizedTime.
+	for i, test := range explicitTaggedTimeTestData {
+		var got explicitTaggedTimeTest
+		_, err := Unmarshal(test.in, &got)
+		if err != nil {
+			t.Errorf("Unmarshal failed at index %d %v", i, err)
+		}
+		if !got.Time.Equal(test.out.Time) {
+			t.Errorf("#%d: got %v, want %v", i, got.Time, test.out.Time)
+		}
+	}
+}
+
+type implicitTaggedTimeTest struct {
+	Time time.Time `asn1:"tag:24"`
+}
+
+func TestImplicitTaggedTime(t *testing.T) {
+	// An implicitly tagged time value, that happens to have an implicit
+	// tag equal to a GENERALIZEDTIME, should still be parsed as a UTCTime.
+	// (There's no "timeType" in fieldParameters to determine what type of
+	// time should be expected when implicitly tagged.)
+	der := []byte{0x30, 0x0f, 0x80 | 24, 0xd, '9', '1', '0', '5', '0', '6', '1', '6', '4', '5', '4', '0', 'Z'}
+	var result implicitTaggedTimeTest
+	if _, err := Unmarshal(der, &result); err != nil {
+		t.Fatalf("Error while parsing: %s", err)
+	}
+	if expected := time.Date(1991, 05, 06, 16, 45, 40, 0, time.UTC); !result.Time.Equal(expected) {
+		t.Errorf("Wrong result. Got %v, want %v", result.Time, expected)
+	}
+}
+
+type truncatedExplicitTagTest struct {
+	Test int `asn1:"explicit,tag:0"`
+}
+
+func TestTruncatedExplicitTag(t *testing.T) {
+	// This crashed Unmarshal in the past. See #11154.
+	der := []byte{
+		0x30, // SEQUENCE
+		0x02, // two bytes long
+		0xa0, // context-specific, tag 0
+		0x30, // 48 bytes long
+	}
+
+	var result truncatedExplicitTagTest
+	if _, err := Unmarshal(der, &result); err == nil {
+		t.Error("Unmarshal returned without error")
+	}
+}
+
+type invalidUTF8Test struct {
+	Str string `asn1:"utf8"`
+}
+
+func TestUnmarshalInvalidUTF8(t *testing.T) {
+	data := []byte("0\x05\f\x03a\xc9c")
+	var result invalidUTF8Test
+	_, err := Unmarshal(data, &result)
+
+	const expectedSubstring = "UTF"
+	if err == nil {
+		t.Fatal("Successfully unmarshaled invalid UTF-8 data")
+	} else if !strings.Contains(err.Error(), expectedSubstring) {
+		t.Fatalf("Expected error to mention %q but error was %q", expectedSubstring, err.Error())
+	}
+}
+
+func TestMarshalNilValue(t *testing.T) {
+	nilValueTestData := []any{
+		nil,
+		struct{ V any }{},
+	}
+	for i, test := range nilValueTestData {
+		if _, err := Marshal(test); err == nil {
+			t.Fatalf("#%d: successfully marshaled nil value", i)
+		}
+	}
+}
+
+type unexported struct {
+	X int
+	y int
+}
+
+type exported struct {
+	X int
+	Y int
+}
+
+func TestUnexportedStructField(t *testing.T) {
+	want := StructuralError{"struct contains unexported fields"}
+
+	_, err := Marshal(unexported{X: 5, y: 1})
+	if err != want {
+		t.Errorf("got %v, want %v", err, want)
+	}
+
+	bs, err := Marshal(exported{X: 5, Y: 1})
+	if err != nil {
+		t.Fatal(err)
+	}
+	var u unexported
+	_, err = Unmarshal(bs, &u)
+	if err != want {
+		t.Errorf("got %v, want %v", err, want)
+	}
+}
+
+func TestNull(t *testing.T) {
+	marshaled, err := Marshal(NullRawValue)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !bytes.Equal(NullBytes, marshaled) {
+		t.Errorf("Expected Marshal of NullRawValue to yield %x, got %x", NullBytes, marshaled)
+	}
+
+	unmarshaled := RawValue{}
+	if _, err := Unmarshal(NullBytes, &unmarshaled); err != nil {
+		t.Fatal(err)
+	}
+
+	unmarshaled.FullBytes = NullRawValue.FullBytes
+	if len(unmarshaled.Bytes) == 0 {
+		// DeepEqual considers a nil slice and an empty slice to be different.
+		unmarshaled.Bytes = NullRawValue.Bytes
+	}
+
+	if !reflect.DeepEqual(NullRawValue, unmarshaled) {
+		t.Errorf("Expected Unmarshal of NullBytes to yield %v, got %v", NullRawValue, unmarshaled)
+	}
+}
+
+func TestExplicitTagRawValueStruct(t *testing.T) {
+	type foo struct {
+		A RawValue `asn1:"optional,explicit,tag:5"`
+		B []byte   `asn1:"optional,explicit,tag:6"`
+	}
+	before := foo{B: []byte{1, 2, 3}}
+	derBytes, err := Marshal(before)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var after foo
+	if rest, err := Unmarshal(derBytes, &after); err != nil || len(rest) != 0 {
+		t.Fatal(err)
+	}
+
+	got := fmt.Sprintf("%#v", after)
+	want := fmt.Sprintf("%#v", before)
+	if got != want {
+		t.Errorf("got %s, want %s (DER: %x)", got, want, derBytes)
+	}
+}
+
+func TestTaggedRawValue(t *testing.T) {
+	type taggedRawValue struct {
+		A RawValue `asn1:"tag:5"`
+	}
+	type untaggedRawValue struct {
+		A RawValue
+	}
+	const isCompound = 0x20
+	const tag = 5
+
+	tests := []struct {
+		shouldMatch bool
+		derBytes    []byte
+	}{
+		{false, []byte{0x30, 3, TagInteger, 1, 1}},
+		{true, []byte{0x30, 3, (ClassContextSpecific << 6) | tag, 1, 1}},
+		{true, []byte{0x30, 3, (ClassContextSpecific << 6) | tag | isCompound, 1, 1}},
+		{false, []byte{0x30, 3, (ClassApplication << 6) | tag | isCompound, 1, 1}},
+		{false, []byte{0x30, 3, (ClassPrivate << 6) | tag | isCompound, 1, 1}},
+	}
+
+	for i, test := range tests {
+		var tagged taggedRawValue
+		if _, err := Unmarshal(test.derBytes, &tagged); (err == nil) != test.shouldMatch {
+			t.Errorf("#%d: unexpected result parsing %x: %s", i, test.derBytes, err)
+		}
+
+		// An untagged RawValue should accept anything.
+		var untagged untaggedRawValue
+		if _, err := Unmarshal(test.derBytes, &untagged); err != nil {
+			t.Errorf("#%d: unexpected failure parsing %x with untagged RawValue: %s", i, test.derBytes, err)
+		}
+	}
+}
+
+var bmpStringTests = []struct {
+	decoded    string
+	encodedHex string
+}{
+	{"", "0000"},
+	// Example from https://tools.ietf.org/html/rfc7292#appendix-B.
+	{"Beavis", "0042006500610076006900730000"},
+	// Some characters from the "Letterlike Symbols Unicode block".
+	{"\u2115 - Double-struck N", "21150020002d00200044006f00750062006c0065002d00730074007200750063006b0020004e0000"},
+}
+
+func TestBMPString(t *testing.T) {
+	for i, test := range bmpStringTests {
+		encoded, err := hex.DecodeString(test.encodedHex)
+		if err != nil {
+			t.Fatalf("#%d: failed to decode from hex string", i)
+		}
+
+		decoded, err := parseBMPString(encoded)
+
+		if err != nil {
+			t.Errorf("#%d: decoding output gave an error: %s", i, err)
+			continue
+		}
+
+		if decoded != test.decoded {
+			t.Errorf("#%d: decoding output resulted in %q, but it should have been %q", i, decoded, test.decoded)
+			continue
+		}
+	}
+}
+
+func TestNonMinimalEncodedOID(t *testing.T) {
+	h, err := hex.DecodeString("060a2a80864886f70d01010b")
+	if err != nil {
+		t.Fatalf("failed to decode from hex string: %s", err)
+	}
+	var oid ObjectIdentifier
+	_, err = Unmarshal(h, &oid)
+	if err == nil {
+		t.Fatalf("accepted non-minimally encoded oid")
+	}
+}
diff --git a/src/encoding/asn1/common.go b/src/encoding/asn1/common.go
new file mode 100644
index 0000000..40115df
--- /dev/null
+++ b/src/encoding/asn1/common.go
@@ -0,0 +1,185 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package asn1
+
+import (
+	"reflect"
+	"strconv"
+	"strings"
+)
+
+// ASN.1 objects have metadata preceding them:
+//   the tag: the type of the object
+//   a flag denoting if this object is compound or not
+//   the class type: the namespace of the tag
+//   the length of the object, in bytes
+
+// Here are some standard tags and classes
+
+// ASN.1 tags represent the type of the following object.
+const (
+	TagBoolean         = 1
+	TagInteger         = 2
+	TagBitString       = 3
+	TagOctetString     = 4
+	TagNull            = 5
+	TagOID             = 6
+	TagEnum            = 10
+	TagUTF8String      = 12
+	TagSequence        = 16
+	TagSet             = 17
+	TagNumericString   = 18
+	TagPrintableString = 19
+	TagT61String       = 20
+	TagIA5String       = 22
+	TagUTCTime         = 23
+	TagGeneralizedTime = 24
+	TagGeneralString   = 27
+	TagBMPString       = 30
+)
+
+// ASN.1 class types represent the namespace of the tag.
+const (
+	ClassUniversal       = 0
+	ClassApplication     = 1
+	ClassContextSpecific = 2
+	ClassPrivate         = 3
+)
+
+type tagAndLength struct {
+	class, tag, length int
+	isCompound         bool
+}
+
+// ASN.1 has IMPLICIT and EXPLICIT tags, which can be translated as "instead
+// of" and "in addition to". When not specified, every primitive type has a
+// default tag in the UNIVERSAL class.
+//
+// For example: a BIT STRING is tagged [UNIVERSAL 3] by default (although ASN.1
+// doesn't actually have a UNIVERSAL keyword). However, by saying [IMPLICIT
+// CONTEXT-SPECIFIC 42], that means that the tag is replaced by another.
+//
+// On the other hand, if it said [EXPLICIT CONTEXT-SPECIFIC 10], then an
+// /additional/ tag would wrap the default tag. This explicit tag will have the
+// compound flag set.
+//
+// (This is used in order to remove ambiguity with optional elements.)
+//
+// You can layer EXPLICIT and IMPLICIT tags to an arbitrary depth, however we
+// don't support that here. We support a single layer of EXPLICIT or IMPLICIT
+// tagging with tag strings on the fields of a structure.
+
+// fieldParameters is the parsed representation of tag string from a structure field.
+type fieldParameters struct {
+	optional     bool   // true iff the field is OPTIONAL
+	explicit     bool   // true iff an EXPLICIT tag is in use.
+	application  bool   // true iff an APPLICATION tag is in use.
+	private      bool   // true iff a PRIVATE tag is in use.
+	defaultValue *int64 // a default value for INTEGER typed fields (maybe nil).
+	tag          *int   // the EXPLICIT or IMPLICIT tag (maybe nil).
+	stringType   int    // the string tag to use when marshaling.
+	timeType     int    // the time tag to use when marshaling.
+	set          bool   // true iff this should be encoded as a SET
+	omitEmpty    bool   // true iff this should be omitted if empty when marshaling.
+
+	// Invariants:
+	//   if explicit is set, tag is non-nil.
+}
+
+// Given a tag string with the format specified in the package comment,
+// parseFieldParameters will parse it into a fieldParameters structure,
+// ignoring unknown parts of the string.
+func parseFieldParameters(str string) (ret fieldParameters) {
+	var part string
+	for len(str) > 0 {
+		part, str, _ = strings.Cut(str, ",")
+		switch {
+		case part == "optional":
+			ret.optional = true
+		case part == "explicit":
+			ret.explicit = true
+			if ret.tag == nil {
+				ret.tag = new(int)
+			}
+		case part == "generalized":
+			ret.timeType = TagGeneralizedTime
+		case part == "utc":
+			ret.timeType = TagUTCTime
+		case part == "ia5":
+			ret.stringType = TagIA5String
+		case part == "printable":
+			ret.stringType = TagPrintableString
+		case part == "numeric":
+			ret.stringType = TagNumericString
+		case part == "utf8":
+			ret.stringType = TagUTF8String
+		case strings.HasPrefix(part, "default:"):
+			i, err := strconv.ParseInt(part[8:], 10, 64)
+			if err == nil {
+				ret.defaultValue = new(int64)
+				*ret.defaultValue = i
+			}
+		case strings.HasPrefix(part, "tag:"):
+			i, err := strconv.Atoi(part[4:])
+			if err == nil {
+				ret.tag = new(int)
+				*ret.tag = i
+			}
+		case part == "set":
+			ret.set = true
+		case part == "application":
+			ret.application = true
+			if ret.tag == nil {
+				ret.tag = new(int)
+			}
+		case part == "private":
+			ret.private = true
+			if ret.tag == nil {
+				ret.tag = new(int)
+			}
+		case part == "omitempty":
+			ret.omitEmpty = true
+		}
+	}
+	return
+}
+
+// Given a reflected Go type, getUniversalType returns the default tag number
+// and expected compound flag.
+func getUniversalType(t reflect.Type) (matchAny bool, tagNumber int, isCompound, ok bool) {
+	switch t {
+	case rawValueType:
+		return true, -1, false, true
+	case objectIdentifierType:
+		return false, TagOID, false, true
+	case bitStringType:
+		return false, TagBitString, false, true
+	case timeType:
+		return false, TagUTCTime, false, true
+	case enumeratedType:
+		return false, TagEnum, false, true
+	case bigIntType:
+		return false, TagInteger, false, true
+	}
+	switch t.Kind() {
+	case reflect.Bool:
+		return false, TagBoolean, false, true
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return false, TagInteger, false, true
+	case reflect.Struct:
+		return false, TagSequence, true, true
+	case reflect.Slice:
+		if t.Elem().Kind() == reflect.Uint8 {
+			return false, TagOctetString, false, true
+		}
+		if strings.HasSuffix(t.Name(), "SET") {
+			return false, TagSet, true, true
+		}
+		return false, TagSequence, true, true
+	case reflect.String:
+		return false, TagPrintableString, false, true
+	}
+	return false, 0, false, false
+}
diff --git a/src/encoding/asn1/marshal.go b/src/encoding/asn1/marshal.go
new file mode 100644
index 0000000..c243349
--- /dev/null
+++ b/src/encoding/asn1/marshal.go
@@ -0,0 +1,747 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package asn1
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"math/big"
+	"reflect"
+	"sort"
+	"time"
+	"unicode/utf8"
+)
+
+var (
+	byte00Encoder encoder = byteEncoder(0x00)
+	byteFFEncoder encoder = byteEncoder(0xff)
+)
+
+// encoder represents an ASN.1 element that is waiting to be marshaled.
+type encoder interface {
+	// Len returns the number of bytes needed to marshal this element.
+	Len() int
+	// Encode encodes this element by writing Len() bytes to dst.
+	Encode(dst []byte)
+}
+
+type byteEncoder byte
+
+func (c byteEncoder) Len() int {
+	return 1
+}
+
+func (c byteEncoder) Encode(dst []byte) {
+	dst[0] = byte(c)
+}
+
+type bytesEncoder []byte
+
+func (b bytesEncoder) Len() int {
+	return len(b)
+}
+
+func (b bytesEncoder) Encode(dst []byte) {
+	if copy(dst, b) != len(b) {
+		panic("internal error")
+	}
+}
+
+type stringEncoder string
+
+func (s stringEncoder) Len() int {
+	return len(s)
+}
+
+func (s stringEncoder) Encode(dst []byte) {
+	if copy(dst, s) != len(s) {
+		panic("internal error")
+	}
+}
+
+type multiEncoder []encoder
+
+func (m multiEncoder) Len() int {
+	var size int
+	for _, e := range m {
+		size += e.Len()
+	}
+	return size
+}
+
+func (m multiEncoder) Encode(dst []byte) {
+	var off int
+	for _, e := range m {
+		e.Encode(dst[off:])
+		off += e.Len()
+	}
+}
+
+type setEncoder []encoder
+
+func (s setEncoder) Len() int {
+	var size int
+	for _, e := range s {
+		size += e.Len()
+	}
+	return size
+}
+
+func (s setEncoder) Encode(dst []byte) {
+	// Per X690 Section 11.6: The encodings of the component values of a
+	// set-of value shall appear in ascending order, the encodings being
+	// compared as octet strings with the shorter components being padded
+	// at their trailing end with 0-octets.
+	//
+	// First we encode each element to its TLV encoding and then use
+	// octetSort to get the ordering expected by X690 DER rules before
+	// writing the sorted encodings out to dst.
+	l := make([][]byte, len(s))
+	for i, e := range s {
+		l[i] = make([]byte, e.Len())
+		e.Encode(l[i])
+	}
+
+	sort.Slice(l, func(i, j int) bool {
+		// Since we are using bytes.Compare to compare TLV encodings we
+		// don't need to right pad s[i] and s[j] to the same length as
+		// suggested in X690. If len(s[i]) < len(s[j]) the length octet of
+		// s[i], which is the first determining byte, will inherently be
+		// smaller than the length octet of s[j]. This lets us skip the
+		// padding step.
+		return bytes.Compare(l[i], l[j]) < 0
+	})
+
+	var off int
+	for _, b := range l {
+		copy(dst[off:], b)
+		off += len(b)
+	}
+}
+
+type taggedEncoder struct {
+	// scratch contains temporary space for encoding the tag and length of
+	// an element in order to avoid extra allocations.
+	scratch [8]byte
+	tag     encoder
+	body    encoder
+}
+
+func (t *taggedEncoder) Len() int {
+	return t.tag.Len() + t.body.Len()
+}
+
+func (t *taggedEncoder) Encode(dst []byte) {
+	t.tag.Encode(dst)
+	t.body.Encode(dst[t.tag.Len():])
+}
+
+type int64Encoder int64
+
+func (i int64Encoder) Len() int {
+	n := 1
+
+	for i > 127 {
+		n++
+		i >>= 8
+	}
+
+	for i < -128 {
+		n++
+		i >>= 8
+	}
+
+	return n
+}
+
+func (i int64Encoder) Encode(dst []byte) {
+	n := i.Len()
+
+	for j := 0; j < n; j++ {
+		dst[j] = byte(i >> uint((n-1-j)*8))
+	}
+}
+
+func base128IntLength(n int64) int {
+	if n == 0 {
+		return 1
+	}
+
+	l := 0
+	for i := n; i > 0; i >>= 7 {
+		l++
+	}
+
+	return l
+}
+
+func appendBase128Int(dst []byte, n int64) []byte {
+	l := base128IntLength(n)
+
+	for i := l - 1; i >= 0; i-- {
+		o := byte(n >> uint(i*7))
+		o &= 0x7f
+		if i != 0 {
+			o |= 0x80
+		}
+
+		dst = append(dst, o)
+	}
+
+	return dst
+}
+
+func makeBigInt(n *big.Int) (encoder, error) {
+	if n == nil {
+		return nil, StructuralError{"empty integer"}
+	}
+
+	if n.Sign() < 0 {
+		// A negative number has to be converted to two's-complement
+		// form. So we'll invert and subtract 1. If the
+		// most-significant-bit isn't set then we'll need to pad the
+		// beginning with 0xff in order to keep the number negative.
+		nMinus1 := new(big.Int).Neg(n)
+		nMinus1.Sub(nMinus1, bigOne)
+		bytes := nMinus1.Bytes()
+		for i := range bytes {
+			bytes[i] ^= 0xff
+		}
+		if len(bytes) == 0 || bytes[0]&0x80 == 0 {
+			return multiEncoder([]encoder{byteFFEncoder, bytesEncoder(bytes)}), nil
+		}
+		return bytesEncoder(bytes), nil
+	} else if n.Sign() == 0 {
+		// Zero is written as a single 0 zero rather than no bytes.
+		return byte00Encoder, nil
+	} else {
+		bytes := n.Bytes()
+		if len(bytes) > 0 && bytes[0]&0x80 != 0 {
+			// We'll have to pad this with 0x00 in order to stop it
+			// looking like a negative number.
+			return multiEncoder([]encoder{byte00Encoder, bytesEncoder(bytes)}), nil
+		}
+		return bytesEncoder(bytes), nil
+	}
+}
+
+func appendLength(dst []byte, i int) []byte {
+	n := lengthLength(i)
+
+	for ; n > 0; n-- {
+		dst = append(dst, byte(i>>uint((n-1)*8)))
+	}
+
+	return dst
+}
+
+func lengthLength(i int) (numBytes int) {
+	numBytes = 1
+	for i > 255 {
+		numBytes++
+		i >>= 8
+	}
+	return
+}
+
+func appendTagAndLength(dst []byte, t tagAndLength) []byte {
+	b := uint8(t.class) << 6
+	if t.isCompound {
+		b |= 0x20
+	}
+	if t.tag >= 31 {
+		b |= 0x1f
+		dst = append(dst, b)
+		dst = appendBase128Int(dst, int64(t.tag))
+	} else {
+		b |= uint8(t.tag)
+		dst = append(dst, b)
+	}
+
+	if t.length >= 128 {
+		l := lengthLength(t.length)
+		dst = append(dst, 0x80|byte(l))
+		dst = appendLength(dst, t.length)
+	} else {
+		dst = append(dst, byte(t.length))
+	}
+
+	return dst
+}
+
+type bitStringEncoder BitString
+
+func (b bitStringEncoder) Len() int {
+	return len(b.Bytes) + 1
+}
+
+func (b bitStringEncoder) Encode(dst []byte) {
+	dst[0] = byte((8 - b.BitLength%8) % 8)
+	if copy(dst[1:], b.Bytes) != len(b.Bytes) {
+		panic("internal error")
+	}
+}
+
+type oidEncoder []int
+
+func (oid oidEncoder) Len() int {
+	l := base128IntLength(int64(oid[0]*40 + oid[1]))
+	for i := 2; i < len(oid); i++ {
+		l += base128IntLength(int64(oid[i]))
+	}
+	return l
+}
+
+func (oid oidEncoder) Encode(dst []byte) {
+	dst = appendBase128Int(dst[:0], int64(oid[0]*40+oid[1]))
+	for i := 2; i < len(oid); i++ {
+		dst = appendBase128Int(dst, int64(oid[i]))
+	}
+}
+
+func makeObjectIdentifier(oid []int) (e encoder, err error) {
+	if len(oid) < 2 || oid[0] > 2 || (oid[0] < 2 && oid[1] >= 40) {
+		return nil, StructuralError{"invalid object identifier"}
+	}
+
+	return oidEncoder(oid), nil
+}
+
+func makePrintableString(s string) (e encoder, err error) {
+	for i := 0; i < len(s); i++ {
+		// The asterisk is often used in PrintableString, even though
+		// it is invalid. If a PrintableString was specifically
+		// requested then the asterisk is permitted by this code.
+		// Ampersand is allowed in parsing due a handful of CA
+		// certificates, however when making new certificates
+		// it is rejected.
+		if !isPrintable(s[i], allowAsterisk, rejectAmpersand) {
+			return nil, StructuralError{"PrintableString contains invalid character"}
+		}
+	}
+
+	return stringEncoder(s), nil
+}
+
+func makeIA5String(s string) (e encoder, err error) {
+	for i := 0; i < len(s); i++ {
+		if s[i] > 127 {
+			return nil, StructuralError{"IA5String contains invalid character"}
+		}
+	}
+
+	return stringEncoder(s), nil
+}
+
+func makeNumericString(s string) (e encoder, err error) {
+	for i := 0; i < len(s); i++ {
+		if !isNumeric(s[i]) {
+			return nil, StructuralError{"NumericString contains invalid character"}
+		}
+	}
+
+	return stringEncoder(s), nil
+}
+
+func makeUTF8String(s string) encoder {
+	return stringEncoder(s)
+}
+
+func appendTwoDigits(dst []byte, v int) []byte {
+	return append(dst, byte('0'+(v/10)%10), byte('0'+v%10))
+}
+
+func appendFourDigits(dst []byte, v int) []byte {
+	var bytes [4]byte
+	for i := range bytes {
+		bytes[3-i] = '0' + byte(v%10)
+		v /= 10
+	}
+	return append(dst, bytes[:]...)
+}
+
+func outsideUTCRange(t time.Time) bool {
+	year := t.Year()
+	return year < 1950 || year >= 2050
+}
+
+func makeUTCTime(t time.Time) (e encoder, err error) {
+	dst := make([]byte, 0, 18)
+
+	dst, err = appendUTCTime(dst, t)
+	if err != nil {
+		return nil, err
+	}
+
+	return bytesEncoder(dst), nil
+}
+
+func makeGeneralizedTime(t time.Time) (e encoder, err error) {
+	dst := make([]byte, 0, 20)
+
+	dst, err = appendGeneralizedTime(dst, t)
+	if err != nil {
+		return nil, err
+	}
+
+	return bytesEncoder(dst), nil
+}
+
+func appendUTCTime(dst []byte, t time.Time) (ret []byte, err error) {
+	year := t.Year()
+
+	switch {
+	case 1950 <= year && year < 2000:
+		dst = appendTwoDigits(dst, year-1900)
+	case 2000 <= year && year < 2050:
+		dst = appendTwoDigits(dst, year-2000)
+	default:
+		return nil, StructuralError{"cannot represent time as UTCTime"}
+	}
+
+	return appendTimeCommon(dst, t), nil
+}
+
+func appendGeneralizedTime(dst []byte, t time.Time) (ret []byte, err error) {
+	year := t.Year()
+	if year < 0 || year > 9999 {
+		return nil, StructuralError{"cannot represent time as GeneralizedTime"}
+	}
+
+	dst = appendFourDigits(dst, year)
+
+	return appendTimeCommon(dst, t), nil
+}
+
+func appendTimeCommon(dst []byte, t time.Time) []byte {
+	_, month, day := t.Date()
+
+	dst = appendTwoDigits(dst, int(month))
+	dst = appendTwoDigits(dst, day)
+
+	hour, min, sec := t.Clock()
+
+	dst = appendTwoDigits(dst, hour)
+	dst = appendTwoDigits(dst, min)
+	dst = appendTwoDigits(dst, sec)
+
+	_, offset := t.Zone()
+
+	switch {
+	case offset/60 == 0:
+		return append(dst, 'Z')
+	case offset > 0:
+		dst = append(dst, '+')
+	case offset < 0:
+		dst = append(dst, '-')
+	}
+
+	offsetMinutes := offset / 60
+	if offsetMinutes < 0 {
+		offsetMinutes = -offsetMinutes
+	}
+
+	dst = appendTwoDigits(dst, offsetMinutes/60)
+	dst = appendTwoDigits(dst, offsetMinutes%60)
+
+	return dst
+}
+
+func stripTagAndLength(in []byte) []byte {
+	_, offset, err := parseTagAndLength(in, 0)
+	if err != nil {
+		return in
+	}
+	return in[offset:]
+}
+
+func makeBody(value reflect.Value, params fieldParameters) (e encoder, err error) {
+	switch value.Type() {
+	case flagType:
+		return bytesEncoder(nil), nil
+	case timeType:
+		t := value.Interface().(time.Time)
+		if params.timeType == TagGeneralizedTime || outsideUTCRange(t) {
+			return makeGeneralizedTime(t)
+		}
+		return makeUTCTime(t)
+	case bitStringType:
+		return bitStringEncoder(value.Interface().(BitString)), nil
+	case objectIdentifierType:
+		return makeObjectIdentifier(value.Interface().(ObjectIdentifier))
+	case bigIntType:
+		return makeBigInt(value.Interface().(*big.Int))
+	}
+
+	switch v := value; v.Kind() {
+	case reflect.Bool:
+		if v.Bool() {
+			return byteFFEncoder, nil
+		}
+		return byte00Encoder, nil
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return int64Encoder(v.Int()), nil
+	case reflect.Struct:
+		t := v.Type()
+
+		for i := 0; i < t.NumField(); i++ {
+			if !t.Field(i).IsExported() {
+				return nil, StructuralError{"struct contains unexported fields"}
+			}
+		}
+
+		startingField := 0
+
+		n := t.NumField()
+		if n == 0 {
+			return bytesEncoder(nil), nil
+		}
+
+		// If the first element of the structure is a non-empty
+		// RawContents, then we don't bother serializing the rest.
+		if t.Field(0).Type == rawContentsType {
+			s := v.Field(0)
+			if s.Len() > 0 {
+				bytes := s.Bytes()
+				/* The RawContents will contain the tag and
+				 * length fields but we'll also be writing
+				 * those ourselves, so we strip them out of
+				 * bytes */
+				return bytesEncoder(stripTagAndLength(bytes)), nil
+			}
+
+			startingField = 1
+		}
+
+		switch n1 := n - startingField; n1 {
+		case 0:
+			return bytesEncoder(nil), nil
+		case 1:
+			return makeField(v.Field(startingField), parseFieldParameters(t.Field(startingField).Tag.Get("asn1")))
+		default:
+			m := make([]encoder, n1)
+			for i := 0; i < n1; i++ {
+				m[i], err = makeField(v.Field(i+startingField), parseFieldParameters(t.Field(i+startingField).Tag.Get("asn1")))
+				if err != nil {
+					return nil, err
+				}
+			}
+
+			return multiEncoder(m), nil
+		}
+	case reflect.Slice:
+		sliceType := v.Type()
+		if sliceType.Elem().Kind() == reflect.Uint8 {
+			return bytesEncoder(v.Bytes()), nil
+		}
+
+		var fp fieldParameters
+
+		switch l := v.Len(); l {
+		case 0:
+			return bytesEncoder(nil), nil
+		case 1:
+			return makeField(v.Index(0), fp)
+		default:
+			m := make([]encoder, l)
+
+			for i := 0; i < l; i++ {
+				m[i], err = makeField(v.Index(i), fp)
+				if err != nil {
+					return nil, err
+				}
+			}
+
+			if params.set {
+				return setEncoder(m), nil
+			}
+			return multiEncoder(m), nil
+		}
+	case reflect.String:
+		switch params.stringType {
+		case TagIA5String:
+			return makeIA5String(v.String())
+		case TagPrintableString:
+			return makePrintableString(v.String())
+		case TagNumericString:
+			return makeNumericString(v.String())
+		default:
+			return makeUTF8String(v.String()), nil
+		}
+	}
+
+	return nil, StructuralError{"unknown Go type"}
+}
+
+func makeField(v reflect.Value, params fieldParameters) (e encoder, err error) {
+	if !v.IsValid() {
+		return nil, fmt.Errorf("asn1: cannot marshal nil value")
+	}
+	// If the field is an interface{} then recurse into it.
+	if v.Kind() == reflect.Interface && v.Type().NumMethod() == 0 {
+		return makeField(v.Elem(), params)
+	}
+
+	if v.Kind() == reflect.Slice && v.Len() == 0 && params.omitEmpty {
+		return bytesEncoder(nil), nil
+	}
+
+	if params.optional && params.defaultValue != nil && canHaveDefaultValue(v.Kind()) {
+		defaultValue := reflect.New(v.Type()).Elem()
+		defaultValue.SetInt(*params.defaultValue)
+
+		if reflect.DeepEqual(v.Interface(), defaultValue.Interface()) {
+			return bytesEncoder(nil), nil
+		}
+	}
+
+	// If no default value is given then the zero value for the type is
+	// assumed to be the default value. This isn't obviously the correct
+	// behavior, but it's what Go has traditionally done.
+	if params.optional && params.defaultValue == nil {
+		if reflect.DeepEqual(v.Interface(), reflect.Zero(v.Type()).Interface()) {
+			return bytesEncoder(nil), nil
+		}
+	}
+
+	if v.Type() == rawValueType {
+		rv := v.Interface().(RawValue)
+		if len(rv.FullBytes) != 0 {
+			return bytesEncoder(rv.FullBytes), nil
+		}
+
+		t := new(taggedEncoder)
+
+		t.tag = bytesEncoder(appendTagAndLength(t.scratch[:0], tagAndLength{rv.Class, rv.Tag, len(rv.Bytes), rv.IsCompound}))
+		t.body = bytesEncoder(rv.Bytes)
+
+		return t, nil
+	}
+
+	matchAny, tag, isCompound, ok := getUniversalType(v.Type())
+	if !ok || matchAny {
+		return nil, StructuralError{fmt.Sprintf("unknown Go type: %v", v.Type())}
+	}
+
+	if params.timeType != 0 && tag != TagUTCTime {
+		return nil, StructuralError{"explicit time type given to non-time member"}
+	}
+
+	if params.stringType != 0 && tag != TagPrintableString {
+		return nil, StructuralError{"explicit string type given to non-string member"}
+	}
+
+	switch tag {
+	case TagPrintableString:
+		if params.stringType == 0 {
+			// This is a string without an explicit string type. We'll use
+			// a PrintableString if the character set in the string is
+			// sufficiently limited, otherwise we'll use a UTF8String.
+			for _, r := range v.String() {
+				if r >= utf8.RuneSelf || !isPrintable(byte(r), rejectAsterisk, rejectAmpersand) {
+					if !utf8.ValidString(v.String()) {
+						return nil, errors.New("asn1: string not valid UTF-8")
+					}
+					tag = TagUTF8String
+					break
+				}
+			}
+		} else {
+			tag = params.stringType
+		}
+	case TagUTCTime:
+		if params.timeType == TagGeneralizedTime || outsideUTCRange(v.Interface().(time.Time)) {
+			tag = TagGeneralizedTime
+		}
+	}
+
+	if params.set {
+		if tag != TagSequence {
+			return nil, StructuralError{"non sequence tagged as set"}
+		}
+		tag = TagSet
+	}
+
+	// makeField can be called for a slice that should be treated as a SET
+	// but doesn't have params.set set, for instance when using a slice
+	// with the SET type name suffix. In this case getUniversalType returns
+	// TagSet, but makeBody doesn't know about that so will treat the slice
+	// as a sequence. To work around this we set params.set.
+	if tag == TagSet && !params.set {
+		params.set = true
+	}
+
+	t := new(taggedEncoder)
+
+	t.body, err = makeBody(v, params)
+	if err != nil {
+		return nil, err
+	}
+
+	bodyLen := t.body.Len()
+
+	class := ClassUniversal
+	if params.tag != nil {
+		if params.application {
+			class = ClassApplication
+		} else if params.private {
+			class = ClassPrivate
+		} else {
+			class = ClassContextSpecific
+		}
+
+		if params.explicit {
+			t.tag = bytesEncoder(appendTagAndLength(t.scratch[:0], tagAndLength{ClassUniversal, tag, bodyLen, isCompound}))
+
+			tt := new(taggedEncoder)
+
+			tt.body = t
+
+			tt.tag = bytesEncoder(appendTagAndLength(tt.scratch[:0], tagAndLength{
+				class:      class,
+				tag:        *params.tag,
+				length:     bodyLen + t.tag.Len(),
+				isCompound: true,
+			}))
+
+			return tt, nil
+		}
+
+		// implicit tag.
+		tag = *params.tag
+	}
+
+	t.tag = bytesEncoder(appendTagAndLength(t.scratch[:0], tagAndLength{class, tag, bodyLen, isCompound}))
+
+	return t, nil
+}
+
+// Marshal returns the ASN.1 encoding of val.
+//
+// In addition to the struct tags recognised by Unmarshal, the following can be
+// used:
+//
+//	ia5:         causes strings to be marshaled as ASN.1, IA5String values
+//	omitempty:   causes empty slices to be skipped
+//	printable:   causes strings to be marshaled as ASN.1, PrintableString values
+//	utf8:        causes strings to be marshaled as ASN.1, UTF8String values
+//	utc:         causes time.Time to be marshaled as ASN.1, UTCTime values
+//	generalized: causes time.Time to be marshaled as ASN.1, GeneralizedTime values
+func Marshal(val any) ([]byte, error) {
+	return MarshalWithParams(val, "")
+}
+
+// MarshalWithParams allows field parameters to be specified for the
+// top-level element. The form of the params is the same as the field tags.
+func MarshalWithParams(val any, params string) ([]byte, error) {
+	e, err := makeField(reflect.ValueOf(val), parseFieldParameters(params))
+	if err != nil {
+		return nil, err
+	}
+	b := make([]byte, e.Len())
+	e.Encode(b)
+	return b, nil
+}
diff --git a/src/encoding/asn1/marshal_test.go b/src/encoding/asn1/marshal_test.go
new file mode 100644
index 0000000..d9c3cf4
--- /dev/null
+++ b/src/encoding/asn1/marshal_test.go
@@ -0,0 +1,406 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package asn1
+
+import (
+	"bytes"
+	"encoding/hex"
+	"math/big"
+	"reflect"
+	"strings"
+	"testing"
+	"time"
+)
+
+type intStruct struct {
+	A int
+}
+
+type twoIntStruct struct {
+	A int
+	B int
+}
+
+type bigIntStruct struct {
+	A *big.Int
+}
+
+type nestedStruct struct {
+	A intStruct
+}
+
+type rawContentsStruct struct {
+	Raw RawContent
+	A   int
+}
+
+type implicitTagTest struct {
+	A int `asn1:"implicit,tag:5"`
+}
+
+type explicitTagTest struct {
+	A int `asn1:"explicit,tag:5"`
+}
+
+type flagTest struct {
+	A Flag `asn1:"tag:0,optional"`
+}
+
+type generalizedTimeTest struct {
+	A time.Time `asn1:"generalized"`
+}
+
+type ia5StringTest struct {
+	A string `asn1:"ia5"`
+}
+
+type printableStringTest struct {
+	A string `asn1:"printable"`
+}
+
+type genericStringTest struct {
+	A string
+}
+
+type optionalRawValueTest struct {
+	A RawValue `asn1:"optional"`
+}
+
+type omitEmptyTest struct {
+	A []string `asn1:"omitempty"`
+}
+
+type defaultTest struct {
+	A int `asn1:"optional,default:1"`
+}
+
+type applicationTest struct {
+	A int `asn1:"application,tag:0"`
+	B int `asn1:"application,tag:1,explicit"`
+}
+
+type privateTest struct {
+	A int `asn1:"private,tag:0"`
+	B int `asn1:"private,tag:1,explicit"`
+	C int `asn1:"private,tag:31"`  // tag size should be 2 octet
+	D int `asn1:"private,tag:128"` // tag size should be 3 octet
+}
+
+type numericStringTest struct {
+	A string `asn1:"numeric"`
+}
+
+type testSET []int
+
+var PST = time.FixedZone("PST", -8*60*60)
+
+type marshalTest struct {
+	in  any
+	out string // hex encoded
+}
+
+func farFuture() time.Time {
+	t, err := time.Parse(time.RFC3339, "2100-04-05T12:01:01Z")
+	if err != nil {
+		panic(err)
+	}
+	return t
+}
+
+var marshalTests = []marshalTest{
+	{10, "02010a"},
+	{127, "02017f"},
+	{128, "02020080"},
+	{-128, "020180"},
+	{-129, "0202ff7f"},
+	{intStruct{64}, "3003020140"},
+	{bigIntStruct{big.NewInt(0x123456)}, "30050203123456"},
+	{twoIntStruct{64, 65}, "3006020140020141"},
+	{nestedStruct{intStruct{127}}, "3005300302017f"},
+	{[]byte{1, 2, 3}, "0403010203"},
+	{implicitTagTest{64}, "3003850140"},
+	{explicitTagTest{64}, "3005a503020140"},
+	{flagTest{true}, "30028000"},
+	{flagTest{false}, "3000"},
+	{time.Unix(0, 0).UTC(), "170d3730303130313030303030305a"},
+	{time.Unix(1258325776, 0).UTC(), "170d3039313131353232353631365a"},
+	{time.Unix(1258325776, 0).In(PST), "17113039313131353134353631362d30383030"},
+	{farFuture(), "180f32313030303430353132303130315a"},
+	{generalizedTimeTest{time.Unix(1258325776, 0).UTC()}, "3011180f32303039313131353232353631365a"},
+	{BitString{[]byte{0x80}, 1}, "03020780"},
+	{BitString{[]byte{0x81, 0xf0}, 12}, "03030481f0"},
+	{ObjectIdentifier([]int{1, 2, 3, 4}), "06032a0304"},
+	{ObjectIdentifier([]int{1, 2, 840, 133549, 1, 1, 5}), "06092a864888932d010105"},
+	{ObjectIdentifier([]int{2, 100, 3}), "0603813403"},
+	{"test", "130474657374"},
+	{
+		"" +
+			"xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx" +
+			"xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx" +
+			"xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx" +
+			"xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx", // This is 127 times 'x'
+		"137f" +
+			"7878787878787878787878787878787878787878787878787878787878787878" +
+			"7878787878787878787878787878787878787878787878787878787878787878" +
+			"7878787878787878787878787878787878787878787878787878787878787878" +
+			"78787878787878787878787878787878787878787878787878787878787878",
+	},
+	{
+		"" +
+			"xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx" +
+			"xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx" +
+			"xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx" +
+			"xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx", // This is 128 times 'x'
+		"138180" +
+			"7878787878787878787878787878787878787878787878787878787878787878" +
+			"7878787878787878787878787878787878787878787878787878787878787878" +
+			"7878787878787878787878787878787878787878787878787878787878787878" +
+			"7878787878787878787878787878787878787878787878787878787878787878",
+	},
+	{ia5StringTest{"test"}, "3006160474657374"},
+	{optionalRawValueTest{}, "3000"},
+	{printableStringTest{"test"}, "3006130474657374"},
+	{printableStringTest{"test*"}, "30071305746573742a"},
+	{genericStringTest{"test"}, "3006130474657374"},
+	{genericStringTest{"test*"}, "30070c05746573742a"},
+	{genericStringTest{"test&"}, "30070c057465737426"},
+	{rawContentsStruct{nil, 64}, "3003020140"},
+	{rawContentsStruct{[]byte{0x30, 3, 1, 2, 3}, 64}, "3003010203"},
+	{RawValue{Tag: 1, Class: 2, IsCompound: false, Bytes: []byte{1, 2, 3}}, "8103010203"},
+	{testSET([]int{10}), "310302010a"},
+	{omitEmptyTest{[]string{}}, "3000"},
+	{omitEmptyTest{[]string{"1"}}, "30053003130131"},
+	{"Σ", "0c02cea3"},
+	{defaultTest{0}, "3003020100"},
+	{defaultTest{1}, "3000"},
+	{defaultTest{2}, "3003020102"},
+	{applicationTest{1, 2}, "30084001016103020102"},
+	{privateTest{1, 2, 3, 4}, "3011c00101e103020102df1f0103df81000104"},
+	{numericStringTest{"1 9"}, "30051203312039"},
+}
+
+func TestMarshal(t *testing.T) {
+	for i, test := range marshalTests {
+		data, err := Marshal(test.in)
+		if err != nil {
+			t.Errorf("#%d failed: %s", i, err)
+		}
+		out, _ := hex.DecodeString(test.out)
+		if !bytes.Equal(out, data) {
+			t.Errorf("#%d got: %x want %x\n\t%q\n\t%q", i, data, out, data, out)
+
+		}
+	}
+}
+
+type marshalWithParamsTest struct {
+	in     any
+	params string
+	out    string // hex encoded
+}
+
+var marshalWithParamsTests = []marshalWithParamsTest{
+	{intStruct{10}, "set", "310302010a"},
+	{intStruct{10}, "application", "600302010a"},
+	{intStruct{10}, "private", "e00302010a"},
+}
+
+func TestMarshalWithParams(t *testing.T) {
+	for i, test := range marshalWithParamsTests {
+		data, err := MarshalWithParams(test.in, test.params)
+		if err != nil {
+			t.Errorf("#%d failed: %s", i, err)
+		}
+		out, _ := hex.DecodeString(test.out)
+		if !bytes.Equal(out, data) {
+			t.Errorf("#%d got: %x want %x\n\t%q\n\t%q", i, data, out, data, out)
+
+		}
+	}
+}
+
+type marshalErrTest struct {
+	in  any
+	err string
+}
+
+var marshalErrTests = []marshalErrTest{
+	{bigIntStruct{nil}, "empty integer"},
+	{numericStringTest{"a"}, "invalid character"},
+	{ia5StringTest{"\xb0"}, "invalid character"},
+	{printableStringTest{"!"}, "invalid character"},
+}
+
+func TestMarshalError(t *testing.T) {
+	for i, test := range marshalErrTests {
+		_, err := Marshal(test.in)
+		if err == nil {
+			t.Errorf("#%d should fail, but success", i)
+			continue
+		}
+
+		if !strings.Contains(err.Error(), test.err) {
+			t.Errorf("#%d got: %v want %v", i, err, test.err)
+		}
+	}
+}
+
+func TestInvalidUTF8(t *testing.T) {
+	_, err := Marshal(string([]byte{0xff, 0xff}))
+	if err == nil {
+		t.Errorf("invalid UTF8 string was accepted")
+	}
+}
+
+func TestMarshalOID(t *testing.T) {
+	var marshalTestsOID = []marshalTest{
+		{[]byte("\x06\x01\x30"), "0403060130"}, // bytes format returns a byte sequence \x04
+		// {ObjectIdentifier([]int{0}), "060100"}, // returns an error as OID 0.0 has the same encoding
+		{[]byte("\x06\x010"), "0403060130"},                // same as above "\x06\x010" = "\x06\x01" + "0"
+		{ObjectIdentifier([]int{2, 999, 3}), "0603883703"}, // Example of ITU-T X.690
+		{ObjectIdentifier([]int{0, 0}), "060100"},          // zero OID
+	}
+	for i, test := range marshalTestsOID {
+		data, err := Marshal(test.in)
+		if err != nil {
+			t.Errorf("#%d failed: %s", i, err)
+		}
+		out, _ := hex.DecodeString(test.out)
+		if !bytes.Equal(out, data) {
+			t.Errorf("#%d got: %x want %x\n\t%q\n\t%q", i, data, out, data, out)
+		}
+	}
+}
+
+func TestIssue11130(t *testing.T) {
+	data := []byte("\x06\x010") // == \x06\x01\x30 == OID = 0 (the figure)
+	var v any
+	// v has Zero value here and Elem() would panic
+	_, err := Unmarshal(data, &v)
+	if err != nil {
+		t.Errorf("%v", err)
+		return
+	}
+	if reflect.TypeOf(v).String() != reflect.TypeOf(ObjectIdentifier{}).String() {
+		t.Errorf("marshal OID returned an invalid type")
+		return
+	}
+
+	data1, err := Marshal(v)
+	if err != nil {
+		t.Errorf("%v", err)
+		return
+	}
+
+	if !bytes.Equal(data, data1) {
+		t.Errorf("got: %q, want: %q \n", data1, data)
+		return
+	}
+
+	var v1 any
+	_, err = Unmarshal(data1, &v1)
+	if err != nil {
+		t.Errorf("%v", err)
+		return
+	}
+	if !reflect.DeepEqual(v, v1) {
+		t.Errorf("got: %#v data=%q, want : %#v data=%q\n ", v1, data1, v, data)
+	}
+}
+
+func BenchmarkMarshal(b *testing.B) {
+	b.ReportAllocs()
+
+	for i := 0; i < b.N; i++ {
+		for _, test := range marshalTests {
+			Marshal(test.in)
+		}
+	}
+}
+
+func TestSetEncoder(t *testing.T) {
+	testStruct := struct {
+		Strings []string `asn1:"set"`
+	}{
+		Strings: []string{"a", "aa", "b", "bb", "c", "cc"},
+	}
+
+	// Expected ordering of the SET should be:
+	// a, b, c, aa, bb, cc
+
+	output, err := Marshal(testStruct)
+	if err != nil {
+		t.Errorf("%v", err)
+	}
+
+	expectedOrder := []string{"a", "b", "c", "aa", "bb", "cc"}
+	var resultStruct struct {
+		Strings []string `asn1:"set"`
+	}
+	rest, err := Unmarshal(output, &resultStruct)
+	if err != nil {
+		t.Errorf("%v", err)
+	}
+	if len(rest) != 0 {
+		t.Error("Unmarshal returned extra garbage")
+	}
+	if !reflect.DeepEqual(expectedOrder, resultStruct.Strings) {
+		t.Errorf("Unexpected SET content. got: %s, want: %s", resultStruct.Strings, expectedOrder)
+	}
+}
+
+func TestSetEncoderSETSliceSuffix(t *testing.T) {
+	type testSetSET []string
+	testSet := testSetSET{"a", "aa", "b", "bb", "c", "cc"}
+
+	// Expected ordering of the SET should be:
+	// a, b, c, aa, bb, cc
+
+	output, err := Marshal(testSet)
+	if err != nil {
+		t.Errorf("%v", err)
+	}
+
+	expectedOrder := testSetSET{"a", "b", "c", "aa", "bb", "cc"}
+	var resultSet testSetSET
+	rest, err := Unmarshal(output, &resultSet)
+	if err != nil {
+		t.Errorf("%v", err)
+	}
+	if len(rest) != 0 {
+		t.Error("Unmarshal returned extra garbage")
+	}
+	if !reflect.DeepEqual(expectedOrder, resultSet) {
+		t.Errorf("Unexpected SET content. got: %s, want: %s", resultSet, expectedOrder)
+	}
+}
+
+func BenchmarkUnmarshal(b *testing.B) {
+	b.ReportAllocs()
+
+	type testCase struct {
+		in  []byte
+		out any
+	}
+	var testData []testCase
+	for _, test := range unmarshalTestData {
+		pv := reflect.New(reflect.TypeOf(test.out).Elem())
+		inCopy := make([]byte, len(test.in))
+		copy(inCopy, test.in)
+		outCopy := pv.Interface()
+
+		testData = append(testData, testCase{
+			in:  inCopy,
+			out: outCopy,
+		})
+	}
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		for _, testCase := range testData {
+			_, _ = Unmarshal(testCase.in, testCase.out)
+		}
+	}
+}
diff --git a/src/encoding/base32/base32.go b/src/encoding/base32/base32.go
new file mode 100644
index 0000000..3feea9b
--- /dev/null
+++ b/src/encoding/base32/base32.go
@@ -0,0 +1,531 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package base32 implements base32 encoding as specified by RFC 4648.
+package base32
+
+import (
+	"io"
+	"strconv"
+)
+
+/*
+ * Encodings
+ */
+
+// An Encoding is a radix 32 encoding/decoding scheme, defined by a
+// 32-character alphabet. The most common is the "base32" encoding
+// introduced for SASL GSSAPI and standardized in RFC 4648.
+// The alternate "base32hex" encoding is used in DNSSEC.
+type Encoding struct {
+	encode    [32]byte
+	decodeMap [256]byte
+	padChar   rune
+}
+
+const (
+	StdPadding rune = '=' // Standard padding character
+	NoPadding  rune = -1  // No padding
+)
+
+const encodeStd = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567"
+const encodeHex = "0123456789ABCDEFGHIJKLMNOPQRSTUV"
+
+// NewEncoding returns a new Encoding defined by the given alphabet,
+// which must be a 32-byte string.
+func NewEncoding(encoder string) *Encoding {
+	if len(encoder) != 32 {
+		panic("encoding alphabet is not 32-bytes long")
+	}
+
+	e := new(Encoding)
+	copy(e.encode[:], encoder)
+	e.padChar = StdPadding
+
+	for i := 0; i < len(e.decodeMap); i++ {
+		e.decodeMap[i] = 0xFF
+	}
+	for i := 0; i < len(encoder); i++ {
+		e.decodeMap[encoder[i]] = byte(i)
+	}
+	return e
+}
+
+// StdEncoding is the standard base32 encoding, as defined in
+// RFC 4648.
+var StdEncoding = NewEncoding(encodeStd)
+
+// HexEncoding is the ``Extended Hex Alphabet'' defined in RFC 4648.
+// It is typically used in DNS.
+var HexEncoding = NewEncoding(encodeHex)
+
+// WithPadding creates a new encoding identical to enc except
+// with a specified padding character, or NoPadding to disable padding.
+// The padding character must not be '\r' or '\n', must not
+// be contained in the encoding's alphabet and must be a rune equal or
+// below '\xff'.
+func (enc Encoding) WithPadding(padding rune) *Encoding {
+	if padding == '\r' || padding == '\n' || padding > 0xff {
+		panic("invalid padding")
+	}
+
+	for i := 0; i < len(enc.encode); i++ {
+		if rune(enc.encode[i]) == padding {
+			panic("padding contained in alphabet")
+		}
+	}
+
+	enc.padChar = padding
+	return &enc
+}
+
+/*
+ * Encoder
+ */
+
+// Encode encodes src using the encoding enc, writing
+// EncodedLen(len(src)) bytes to dst.
+//
+// The encoding pads the output to a multiple of 8 bytes,
+// so Encode is not appropriate for use on individual blocks
+// of a large data stream. Use NewEncoder() instead.
+func (enc *Encoding) Encode(dst, src []byte) {
+	for len(src) > 0 {
+		var b [8]byte
+
+		// Unpack 8x 5-bit source blocks into a 5 byte
+		// destination quantum
+		switch len(src) {
+		default:
+			b[7] = src[4] & 0x1F
+			b[6] = src[4] >> 5
+			fallthrough
+		case 4:
+			b[6] |= (src[3] << 3) & 0x1F
+			b[5] = (src[3] >> 2) & 0x1F
+			b[4] = src[3] >> 7
+			fallthrough
+		case 3:
+			b[4] |= (src[2] << 1) & 0x1F
+			b[3] = (src[2] >> 4) & 0x1F
+			fallthrough
+		case 2:
+			b[3] |= (src[1] << 4) & 0x1F
+			b[2] = (src[1] >> 1) & 0x1F
+			b[1] = (src[1] >> 6) & 0x1F
+			fallthrough
+		case 1:
+			b[1] |= (src[0] << 2) & 0x1F
+			b[0] = src[0] >> 3
+		}
+
+		// Encode 5-bit blocks using the base32 alphabet
+		size := len(dst)
+		if size >= 8 {
+			// Common case, unrolled for extra performance
+			dst[0] = enc.encode[b[0]&31]
+			dst[1] = enc.encode[b[1]&31]
+			dst[2] = enc.encode[b[2]&31]
+			dst[3] = enc.encode[b[3]&31]
+			dst[4] = enc.encode[b[4]&31]
+			dst[5] = enc.encode[b[5]&31]
+			dst[6] = enc.encode[b[6]&31]
+			dst[7] = enc.encode[b[7]&31]
+		} else {
+			for i := 0; i < size; i++ {
+				dst[i] = enc.encode[b[i]&31]
+			}
+		}
+
+		// Pad the final quantum
+		if len(src) < 5 {
+			if enc.padChar == NoPadding {
+				break
+			}
+
+			dst[7] = byte(enc.padChar)
+			if len(src) < 4 {
+				dst[6] = byte(enc.padChar)
+				dst[5] = byte(enc.padChar)
+				if len(src) < 3 {
+					dst[4] = byte(enc.padChar)
+					if len(src) < 2 {
+						dst[3] = byte(enc.padChar)
+						dst[2] = byte(enc.padChar)
+					}
+				}
+			}
+
+			break
+		}
+
+		src = src[5:]
+		dst = dst[8:]
+	}
+}
+
+// EncodeToString returns the base32 encoding of src.
+func (enc *Encoding) EncodeToString(src []byte) string {
+	buf := make([]byte, enc.EncodedLen(len(src)))
+	enc.Encode(buf, src)
+	return string(buf)
+}
+
+type encoder struct {
+	err  error
+	enc  *Encoding
+	w    io.Writer
+	buf  [5]byte    // buffered data waiting to be encoded
+	nbuf int        // number of bytes in buf
+	out  [1024]byte // output buffer
+}
+
+func (e *encoder) Write(p []byte) (n int, err error) {
+	if e.err != nil {
+		return 0, e.err
+	}
+
+	// Leading fringe.
+	if e.nbuf > 0 {
+		var i int
+		for i = 0; i < len(p) && e.nbuf < 5; i++ {
+			e.buf[e.nbuf] = p[i]
+			e.nbuf++
+		}
+		n += i
+		p = p[i:]
+		if e.nbuf < 5 {
+			return
+		}
+		e.enc.Encode(e.out[0:], e.buf[0:])
+		if _, e.err = e.w.Write(e.out[0:8]); e.err != nil {
+			return n, e.err
+		}
+		e.nbuf = 0
+	}
+
+	// Large interior chunks.
+	for len(p) >= 5 {
+		nn := len(e.out) / 8 * 5
+		if nn > len(p) {
+			nn = len(p)
+			nn -= nn % 5
+		}
+		e.enc.Encode(e.out[0:], p[0:nn])
+		if _, e.err = e.w.Write(e.out[0 : nn/5*8]); e.err != nil {
+			return n, e.err
+		}
+		n += nn
+		p = p[nn:]
+	}
+
+	// Trailing fringe.
+	copy(e.buf[:], p)
+	e.nbuf = len(p)
+	n += len(p)
+	return
+}
+
+// Close flushes any pending output from the encoder.
+// It is an error to call Write after calling Close.
+func (e *encoder) Close() error {
+	// If there's anything left in the buffer, flush it out
+	if e.err == nil && e.nbuf > 0 {
+		e.enc.Encode(e.out[0:], e.buf[0:e.nbuf])
+		encodedLen := e.enc.EncodedLen(e.nbuf)
+		e.nbuf = 0
+		_, e.err = e.w.Write(e.out[0:encodedLen])
+	}
+	return e.err
+}
+
+// NewEncoder returns a new base32 stream encoder. Data written to
+// the returned writer will be encoded using enc and then written to w.
+// Base32 encodings operate in 5-byte blocks; when finished
+// writing, the caller must Close the returned encoder to flush any
+// partially written blocks.
+func NewEncoder(enc *Encoding, w io.Writer) io.WriteCloser {
+	return &encoder{enc: enc, w: w}
+}
+
+// EncodedLen returns the length in bytes of the base32 encoding
+// of an input buffer of length n.
+func (enc *Encoding) EncodedLen(n int) int {
+	if enc.padChar == NoPadding {
+		return (n*8 + 4) / 5
+	}
+	return (n + 4) / 5 * 8
+}
+
+/*
+ * Decoder
+ */
+
+type CorruptInputError int64
+
+func (e CorruptInputError) Error() string {
+	return "illegal base32 data at input byte " + strconv.FormatInt(int64(e), 10)
+}
+
+// decode is like Decode but returns an additional 'end' value, which
+// indicates if end-of-message padding was encountered and thus any
+// additional data is an error. This method assumes that src has been
+// stripped of all supported whitespace ('\r' and '\n').
+func (enc *Encoding) decode(dst, src []byte) (n int, end bool, err error) {
+	// Lift the nil check outside of the loop.
+	_ = enc.decodeMap
+
+	dsti := 0
+	olen := len(src)
+
+	for len(src) > 0 && !end {
+		// Decode quantum using the base32 alphabet
+		var dbuf [8]byte
+		dlen := 8
+
+		for j := 0; j < 8; {
+
+			if len(src) == 0 {
+				if enc.padChar != NoPadding {
+					// We have reached the end and are missing padding
+					return n, false, CorruptInputError(olen - len(src) - j)
+				}
+				// We have reached the end and are not expecting any padding
+				dlen, end = j, true
+				break
+			}
+			in := src[0]
+			src = src[1:]
+			if in == byte(enc.padChar) && j >= 2 && len(src) < 8 {
+				// We've reached the end and there's padding
+				if len(src)+j < 8-1 {
+					// not enough padding
+					return n, false, CorruptInputError(olen)
+				}
+				for k := 0; k < 8-1-j; k++ {
+					if len(src) > k && src[k] != byte(enc.padChar) {
+						// incorrect padding
+						return n, false, CorruptInputError(olen - len(src) + k - 1)
+					}
+				}
+				dlen, end = j, true
+				// 7, 5 and 2 are not valid padding lengths, and so 1, 3 and 6 are not
+				// valid dlen values. See RFC 4648 Section 6 "Base 32 Encoding" listing
+				// the five valid padding lengths, and Section 9 "Illustrations and
+				// Examples" for an illustration for how the 1st, 3rd and 6th base32
+				// src bytes do not yield enough information to decode a dst byte.
+				if dlen == 1 || dlen == 3 || dlen == 6 {
+					return n, false, CorruptInputError(olen - len(src) - 1)
+				}
+				break
+			}
+			dbuf[j] = enc.decodeMap[in]
+			if dbuf[j] == 0xFF {
+				return n, false, CorruptInputError(olen - len(src) - 1)
+			}
+			j++
+		}
+
+		// Pack 8x 5-bit source blocks into 5 byte destination
+		// quantum
+		switch dlen {
+		case 8:
+			dst[dsti+4] = dbuf[6]<<5 | dbuf[7]
+			n++
+			fallthrough
+		case 7:
+			dst[dsti+3] = dbuf[4]<<7 | dbuf[5]<<2 | dbuf[6]>>3
+			n++
+			fallthrough
+		case 5:
+			dst[dsti+2] = dbuf[3]<<4 | dbuf[4]>>1
+			n++
+			fallthrough
+		case 4:
+			dst[dsti+1] = dbuf[1]<<6 | dbuf[2]<<1 | dbuf[3]>>4
+			n++
+			fallthrough
+		case 2:
+			dst[dsti+0] = dbuf[0]<<3 | dbuf[1]>>2
+			n++
+		}
+		dsti += 5
+	}
+	return n, end, nil
+}
+
+// Decode decodes src using the encoding enc. It writes at most
+// DecodedLen(len(src)) bytes to dst and returns the number of bytes
+// written. If src contains invalid base32 data, it will return the
+// number of bytes successfully written and CorruptInputError.
+// New line characters (\r and \n) are ignored.
+func (enc *Encoding) Decode(dst, src []byte) (n int, err error) {
+	buf := make([]byte, len(src))
+	l := stripNewlines(buf, src)
+	n, _, err = enc.decode(dst, buf[:l])
+	return
+}
+
+// DecodeString returns the bytes represented by the base32 string s.
+func (enc *Encoding) DecodeString(s string) ([]byte, error) {
+	buf := []byte(s)
+	l := stripNewlines(buf, buf)
+	n, _, err := enc.decode(buf, buf[:l])
+	return buf[:n], err
+}
+
+type decoder struct {
+	err    error
+	enc    *Encoding
+	r      io.Reader
+	end    bool       // saw end of message
+	buf    [1024]byte // leftover input
+	nbuf   int
+	out    []byte // leftover decoded output
+	outbuf [1024 / 8 * 5]byte
+}
+
+func readEncodedData(r io.Reader, buf []byte, min int, expectsPadding bool) (n int, err error) {
+	for n < min && err == nil {
+		var nn int
+		nn, err = r.Read(buf[n:])
+		n += nn
+	}
+	// data was read, less than min bytes could be read
+	if n < min && n > 0 && err == io.EOF {
+		err = io.ErrUnexpectedEOF
+	}
+	// no data was read, the buffer already contains some data
+	// when padding is disabled this is not an error, as the message can be of
+	// any length
+	if expectsPadding && min < 8 && n == 0 && err == io.EOF {
+		err = io.ErrUnexpectedEOF
+	}
+	return
+}
+
+func (d *decoder) Read(p []byte) (n int, err error) {
+	// Use leftover decoded output from last read.
+	if len(d.out) > 0 {
+		n = copy(p, d.out)
+		d.out = d.out[n:]
+		if len(d.out) == 0 {
+			return n, d.err
+		}
+		return n, nil
+	}
+
+	if d.err != nil {
+		return 0, d.err
+	}
+
+	// Read a chunk.
+	nn := len(p) / 5 * 8
+	if nn < 8 {
+		nn = 8
+	}
+	if nn > len(d.buf) {
+		nn = len(d.buf)
+	}
+
+	// Minimum amount of bytes that needs to be read each cycle
+	var min int
+	var expectsPadding bool
+	if d.enc.padChar == NoPadding {
+		min = 1
+		expectsPadding = false
+	} else {
+		min = 8 - d.nbuf
+		expectsPadding = true
+	}
+
+	nn, d.err = readEncodedData(d.r, d.buf[d.nbuf:nn], min, expectsPadding)
+	d.nbuf += nn
+	if d.nbuf < min {
+		return 0, d.err
+	}
+
+	// Decode chunk into p, or d.out and then p if p is too small.
+	var nr int
+	if d.enc.padChar == NoPadding {
+		nr = d.nbuf
+	} else {
+		nr = d.nbuf / 8 * 8
+	}
+	nw := d.enc.DecodedLen(d.nbuf)
+
+	if nw > len(p) {
+		nw, d.end, err = d.enc.decode(d.outbuf[0:], d.buf[0:nr])
+		d.out = d.outbuf[0:nw]
+		n = copy(p, d.out)
+		d.out = d.out[n:]
+	} else {
+		n, d.end, err = d.enc.decode(p, d.buf[0:nr])
+	}
+	d.nbuf -= nr
+	for i := 0; i < d.nbuf; i++ {
+		d.buf[i] = d.buf[i+nr]
+	}
+
+	if err != nil && (d.err == nil || d.err == io.EOF) {
+		d.err = err
+	}
+
+	if len(d.out) > 0 {
+		// We cannot return all the decoded bytes to the caller in this
+		// invocation of Read, so we return a nil error to ensure that Read
+		// will be called again.  The error stored in d.err, if any, will be
+		// returned with the last set of decoded bytes.
+		return n, nil
+	}
+
+	return n, d.err
+}
+
+type newlineFilteringReader struct {
+	wrapped io.Reader
+}
+
+// stripNewlines removes newline characters and returns the number
+// of non-newline characters copied to dst.
+func stripNewlines(dst, src []byte) int {
+	offset := 0
+	for _, b := range src {
+		if b == '\r' || b == '\n' {
+			continue
+		}
+		dst[offset] = b
+		offset++
+	}
+	return offset
+}
+
+func (r *newlineFilteringReader) Read(p []byte) (int, error) {
+	n, err := r.wrapped.Read(p)
+	for n > 0 {
+		s := p[0:n]
+		offset := stripNewlines(s, s)
+		if err != nil || offset > 0 {
+			return offset, err
+		}
+		// Previous buffer entirely whitespace, read again
+		n, err = r.wrapped.Read(p)
+	}
+	return n, err
+}
+
+// NewDecoder constructs a new base32 stream decoder.
+func NewDecoder(enc *Encoding, r io.Reader) io.Reader {
+	return &decoder{enc: enc, r: &newlineFilteringReader{r}}
+}
+
+// DecodedLen returns the maximum length in bytes of the decoded data
+// corresponding to n bytes of base32-encoded data.
+func (enc *Encoding) DecodedLen(n int) int {
+	if enc.padChar == NoPadding {
+		return n * 5 / 8
+	}
+
+	return n / 8 * 5
+}
diff --git a/src/encoding/base32/base32_test.go b/src/encoding/base32/base32_test.go
new file mode 100644
index 0000000..dbd2b61
--- /dev/null
+++ b/src/encoding/base32/base32_test.go
@@ -0,0 +1,768 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package base32
+
+import (
+	"bytes"
+	"errors"
+	"io"
+	"strings"
+	"testing"
+)
+
+type testpair struct {
+	decoded, encoded string
+}
+
+var pairs = []testpair{
+	// RFC 4648 examples
+	{"", ""},
+	{"f", "MY======"},
+	{"fo", "MZXQ===="},
+	{"foo", "MZXW6==="},
+	{"foob", "MZXW6YQ="},
+	{"fooba", "MZXW6YTB"},
+	{"foobar", "MZXW6YTBOI======"},
+
+	// Wikipedia examples, converted to base32
+	{"sure.", "ON2XEZJO"},
+	{"sure", "ON2XEZI="},
+	{"sur", "ON2XE==="},
+	{"su", "ON2Q===="},
+	{"leasure.", "NRSWC43VOJSS4==="},
+	{"easure.", "MVQXG5LSMUXA===="},
+	{"asure.", "MFZXK4TFFY======"},
+	{"sure.", "ON2XEZJO"},
+}
+
+var bigtest = testpair{
+	"Twas brillig, and the slithy toves",
+	"KR3WC4ZAMJZGS3DMNFTSYIDBNZSCA5DIMUQHG3DJORUHSIDUN53GK4Y=",
+}
+
+func testEqual(t *testing.T, msg string, args ...any) bool {
+	t.Helper()
+	if args[len(args)-2] != args[len(args)-1] {
+		t.Errorf(msg, args...)
+		return false
+	}
+	return true
+}
+
+func TestEncode(t *testing.T) {
+	for _, p := range pairs {
+		got := StdEncoding.EncodeToString([]byte(p.decoded))
+		testEqual(t, "Encode(%q) = %q, want %q", p.decoded, got, p.encoded)
+	}
+}
+
+func TestEncoder(t *testing.T) {
+	for _, p := range pairs {
+		bb := &bytes.Buffer{}
+		encoder := NewEncoder(StdEncoding, bb)
+		encoder.Write([]byte(p.decoded))
+		encoder.Close()
+		testEqual(t, "Encode(%q) = %q, want %q", p.decoded, bb.String(), p.encoded)
+	}
+}
+
+func TestEncoderBuffering(t *testing.T) {
+	input := []byte(bigtest.decoded)
+	for bs := 1; bs <= 12; bs++ {
+		bb := &bytes.Buffer{}
+		encoder := NewEncoder(StdEncoding, bb)
+		for pos := 0; pos < len(input); pos += bs {
+			end := pos + bs
+			if end > len(input) {
+				end = len(input)
+			}
+			n, err := encoder.Write(input[pos:end])
+			testEqual(t, "Write(%q) gave error %v, want %v", input[pos:end], err, error(nil))
+			testEqual(t, "Write(%q) gave length %v, want %v", input[pos:end], n, end-pos)
+		}
+		err := encoder.Close()
+		testEqual(t, "Close gave error %v, want %v", err, error(nil))
+		testEqual(t, "Encoding/%d of %q = %q, want %q", bs, bigtest.decoded, bb.String(), bigtest.encoded)
+	}
+}
+
+func TestDecode(t *testing.T) {
+	for _, p := range pairs {
+		dbuf := make([]byte, StdEncoding.DecodedLen(len(p.encoded)))
+		count, end, err := StdEncoding.decode(dbuf, []byte(p.encoded))
+		testEqual(t, "Decode(%q) = error %v, want %v", p.encoded, err, error(nil))
+		testEqual(t, "Decode(%q) = length %v, want %v", p.encoded, count, len(p.decoded))
+		if len(p.encoded) > 0 {
+			testEqual(t, "Decode(%q) = end %v, want %v", p.encoded, end, (p.encoded[len(p.encoded)-1] == '='))
+		}
+		testEqual(t, "Decode(%q) = %q, want %q", p.encoded,
+			string(dbuf[0:count]),
+			p.decoded)
+
+		dbuf, err = StdEncoding.DecodeString(p.encoded)
+		testEqual(t, "DecodeString(%q) = error %v, want %v", p.encoded, err, error(nil))
+		testEqual(t, "DecodeString(%q) = %q, want %q", p.encoded, string(dbuf), p.decoded)
+	}
+}
+
+func TestDecoder(t *testing.T) {
+	for _, p := range pairs {
+		decoder := NewDecoder(StdEncoding, strings.NewReader(p.encoded))
+		dbuf := make([]byte, StdEncoding.DecodedLen(len(p.encoded)))
+		count, err := decoder.Read(dbuf)
+		if err != nil && err != io.EOF {
+			t.Fatal("Read failed", err)
+		}
+		testEqual(t, "Read from %q = length %v, want %v", p.encoded, count, len(p.decoded))
+		testEqual(t, "Decoding of %q = %q, want %q", p.encoded, string(dbuf[0:count]), p.decoded)
+		if err != io.EOF {
+			_, err = decoder.Read(dbuf)
+		}
+		testEqual(t, "Read from %q = %v, want %v", p.encoded, err, io.EOF)
+	}
+}
+
+type badReader struct {
+	data   []byte
+	errs   []error
+	called int
+	limit  int
+}
+
+// Populates p with data, returns a count of the bytes written and an
+// error.  The error returned is taken from badReader.errs, with each
+// invocation of Read returning the next error in this slice, or io.EOF,
+// if all errors from the slice have already been returned.  The
+// number of bytes returned is determined by the size of the input buffer
+// the test passes to decoder.Read and will be a multiple of 8, unless
+// badReader.limit is non zero.
+func (b *badReader) Read(p []byte) (int, error) {
+	lim := len(p)
+	if b.limit != 0 && b.limit < lim {
+		lim = b.limit
+	}
+	if len(b.data) < lim {
+		lim = len(b.data)
+	}
+	for i := range p[:lim] {
+		p[i] = b.data[i]
+	}
+	b.data = b.data[lim:]
+	err := io.EOF
+	if b.called < len(b.errs) {
+		err = b.errs[b.called]
+	}
+	b.called++
+	return lim, err
+}
+
+// TestIssue20044 tests that decoder.Read behaves correctly when the caller
+// supplied reader returns an error.
+func TestIssue20044(t *testing.T) {
+	badErr := errors.New("bad reader error")
+	testCases := []struct {
+		r       badReader
+		res     string
+		err     error
+		dbuflen int
+	}{
+		// Check valid input data accompanied by an error is processed and the error is propagated.
+		{r: badReader{data: []byte("MY======"), errs: []error{badErr}},
+			res: "f", err: badErr},
+		// Check a read error accompanied by input data consisting of newlines only is propagated.
+		{r: badReader{data: []byte("\n\n\n\n\n\n\n\n"), errs: []error{badErr, nil}},
+			res: "", err: badErr},
+		// Reader will be called twice.  The first time it will return 8 newline characters.  The
+		// second time valid base32 encoded data and an error.  The data should be decoded
+		// correctly and the error should be propagated.
+		{r: badReader{data: []byte("\n\n\n\n\n\n\n\nMY======"), errs: []error{nil, badErr}},
+			res: "f", err: badErr, dbuflen: 8},
+		// Reader returns invalid input data (too short) and an error.  Verify the reader
+		// error is returned.
+		{r: badReader{data: []byte("MY====="), errs: []error{badErr}},
+			res: "", err: badErr},
+		// Reader returns invalid input data (too short) but no error.  Verify io.ErrUnexpectedEOF
+		// is returned.
+		{r: badReader{data: []byte("MY====="), errs: []error{nil}},
+			res: "", err: io.ErrUnexpectedEOF},
+		// Reader returns invalid input data and an error.  Verify the reader and not the
+		// decoder error is returned.
+		{r: badReader{data: []byte("Ma======"), errs: []error{badErr}},
+			res: "", err: badErr},
+		// Reader returns valid data and io.EOF.  Check data is decoded and io.EOF is propagated.
+		{r: badReader{data: []byte("MZXW6YTB"), errs: []error{io.EOF}},
+			res: "fooba", err: io.EOF},
+		// Check errors are properly reported when decoder.Read is called multiple times.
+		// decoder.Read will be called 8 times, badReader.Read will be called twice, returning
+		// valid data both times but an error on the second call.
+		{r: badReader{data: []byte("NRSWC43VOJSS4==="), errs: []error{nil, badErr}},
+			res: "leasure.", err: badErr, dbuflen: 1},
+		// Check io.EOF is properly reported when decoder.Read is called multiple times.
+		// decoder.Read will be called 8 times, badReader.Read will be called twice, returning
+		// valid data both times but io.EOF on the second call.
+		{r: badReader{data: []byte("NRSWC43VOJSS4==="), errs: []error{nil, io.EOF}},
+			res: "leasure.", err: io.EOF, dbuflen: 1},
+		// The following two test cases check that errors are propagated correctly when more than
+		// 8 bytes are read at a time.
+		{r: badReader{data: []byte("NRSWC43VOJSS4==="), errs: []error{io.EOF}},
+			res: "leasure.", err: io.EOF, dbuflen: 11},
+		{r: badReader{data: []byte("NRSWC43VOJSS4==="), errs: []error{badErr}},
+			res: "leasure.", err: badErr, dbuflen: 11},
+		// Check that errors are correctly propagated when the reader returns valid bytes in
+		// groups that are not divisible by 8.  The first read will return 11 bytes and no
+		// error.  The second will return 7 and an error.  The data should be decoded correctly
+		// and the error should be propagated.
+		{r: badReader{data: []byte("NRSWC43VOJSS4==="), errs: []error{nil, badErr}, limit: 11},
+			res: "leasure.", err: badErr},
+	}
+
+	for _, tc := range testCases {
+		input := tc.r.data
+		decoder := NewDecoder(StdEncoding, &tc.r)
+		var dbuflen int
+		if tc.dbuflen > 0 {
+			dbuflen = tc.dbuflen
+		} else {
+			dbuflen = StdEncoding.DecodedLen(len(input))
+		}
+		dbuf := make([]byte, dbuflen)
+		var err error
+		var res []byte
+		for err == nil {
+			var n int
+			n, err = decoder.Read(dbuf)
+			if n > 0 {
+				res = append(res, dbuf[:n]...)
+			}
+		}
+
+		testEqual(t, "Decoding of %q = %q, want %q", string(input), string(res), tc.res)
+		testEqual(t, "Decoding of %q err = %v, expected %v", string(input), err, tc.err)
+	}
+}
+
+// TestDecoderError verifies decode errors are propagated when there are no read
+// errors.
+func TestDecoderError(t *testing.T) {
+	for _, readErr := range []error{io.EOF, nil} {
+		input := "MZXW6YTb"
+		dbuf := make([]byte, StdEncoding.DecodedLen(len(input)))
+		br := badReader{data: []byte(input), errs: []error{readErr}}
+		decoder := NewDecoder(StdEncoding, &br)
+		n, err := decoder.Read(dbuf)
+		testEqual(t, "Read after EOF, n = %d, expected %d", n, 0)
+		if _, ok := err.(CorruptInputError); !ok {
+			t.Errorf("Corrupt input error expected.  Found %T", err)
+		}
+	}
+}
+
+// TestReaderEOF ensures decoder.Read behaves correctly when input data is
+// exhausted.
+func TestReaderEOF(t *testing.T) {
+	for _, readErr := range []error{io.EOF, nil} {
+		input := "MZXW6YTB"
+		br := badReader{data: []byte(input), errs: []error{nil, readErr}}
+		decoder := NewDecoder(StdEncoding, &br)
+		dbuf := make([]byte, StdEncoding.DecodedLen(len(input)))
+		n, err := decoder.Read(dbuf)
+		testEqual(t, "Decoding of %q err = %v, expected %v", string(input), err, error(nil))
+		n, err = decoder.Read(dbuf)
+		testEqual(t, "Read after EOF, n = %d, expected %d", n, 0)
+		testEqual(t, "Read after EOF, err = %v, expected %v", err, io.EOF)
+		n, err = decoder.Read(dbuf)
+		testEqual(t, "Read after EOF, n = %d, expected %d", n, 0)
+		testEqual(t, "Read after EOF, err = %v, expected %v", err, io.EOF)
+	}
+}
+
+func TestDecoderBuffering(t *testing.T) {
+	for bs := 1; bs <= 12; bs++ {
+		decoder := NewDecoder(StdEncoding, strings.NewReader(bigtest.encoded))
+		buf := make([]byte, len(bigtest.decoded)+12)
+		var total int
+		var n int
+		var err error
+		for total = 0; total < len(bigtest.decoded) && err == nil; {
+			n, err = decoder.Read(buf[total : total+bs])
+			total += n
+		}
+		if err != nil && err != io.EOF {
+			t.Errorf("Read from %q at pos %d = %d, unexpected error %v", bigtest.encoded, total, n, err)
+		}
+		testEqual(t, "Decoding/%d of %q = %q, want %q", bs, bigtest.encoded, string(buf[0:total]), bigtest.decoded)
+	}
+}
+
+func TestDecodeCorrupt(t *testing.T) {
+	testCases := []struct {
+		input  string
+		offset int // -1 means no corruption.
+	}{
+		{"", -1},
+		{"!!!!", 0},
+		{"x===", 0},
+		{"AA=A====", 2},
+		{"AAA=AAAA", 3},
+		{"MMMMMMMMM", 8},
+		{"MMMMMM", 0},
+		{"A=", 1},
+		{"AA=", 3},
+		{"AA==", 4},
+		{"AA===", 5},
+		{"AAAA=", 5},
+		{"AAAA==", 6},
+		{"AAAAA=", 6},
+		{"AAAAA==", 7},
+		{"A=======", 1},
+		{"AA======", -1},
+		{"AAA=====", 3},
+		{"AAAA====", -1},
+		{"AAAAA===", -1},
+		{"AAAAAA==", 6},
+		{"AAAAAAA=", -1},
+		{"AAAAAAAA", -1},
+	}
+	for _, tc := range testCases {
+		dbuf := make([]byte, StdEncoding.DecodedLen(len(tc.input)))
+		_, err := StdEncoding.Decode(dbuf, []byte(tc.input))
+		if tc.offset == -1 {
+			if err != nil {
+				t.Error("Decoder wrongly detected corruption in", tc.input)
+			}
+			continue
+		}
+		switch err := err.(type) {
+		case CorruptInputError:
+			testEqual(t, "Corruption in %q at offset %v, want %v", tc.input, int(err), tc.offset)
+		default:
+			t.Error("Decoder failed to detect corruption in", tc)
+		}
+	}
+}
+
+func TestBig(t *testing.T) {
+	n := 3*1000 + 1
+	raw := make([]byte, n)
+	const alpha = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
+	for i := 0; i < n; i++ {
+		raw[i] = alpha[i%len(alpha)]
+	}
+	encoded := new(bytes.Buffer)
+	w := NewEncoder(StdEncoding, encoded)
+	nn, err := w.Write(raw)
+	if nn != n || err != nil {
+		t.Fatalf("Encoder.Write(raw) = %d, %v want %d, nil", nn, err, n)
+	}
+	err = w.Close()
+	if err != nil {
+		t.Fatalf("Encoder.Close() = %v want nil", err)
+	}
+	decoded, err := io.ReadAll(NewDecoder(StdEncoding, encoded))
+	if err != nil {
+		t.Fatalf("io.ReadAll(NewDecoder(...)): %v", err)
+	}
+
+	if !bytes.Equal(raw, decoded) {
+		var i int
+		for i = 0; i < len(decoded) && i < len(raw); i++ {
+			if decoded[i] != raw[i] {
+				break
+			}
+		}
+		t.Errorf("Decode(Encode(%d-byte string)) failed at offset %d", n, i)
+	}
+}
+
+func testStringEncoding(t *testing.T, expected string, examples []string) {
+	for _, e := range examples {
+		buf, err := StdEncoding.DecodeString(e)
+		if err != nil {
+			t.Errorf("Decode(%q) failed: %v", e, err)
+			continue
+		}
+		if s := string(buf); s != expected {
+			t.Errorf("Decode(%q) = %q, want %q", e, s, expected)
+		}
+	}
+}
+
+func TestNewLineCharacters(t *testing.T) {
+	// Each of these should decode to the string "sure", without errors.
+	examples := []string{
+		"ON2XEZI=",
+		"ON2XEZI=\r",
+		"ON2XEZI=\n",
+		"ON2XEZI=\r\n",
+		"ON2XEZ\r\nI=",
+		"ON2X\rEZ\nI=",
+		"ON2X\nEZ\rI=",
+		"ON2XEZ\nI=",
+		"ON2XEZI\n=",
+	}
+	testStringEncoding(t, "sure", examples)
+
+	// Each of these should decode to the string "foobar", without errors.
+	examples = []string{
+		"MZXW6YTBOI======",
+		"MZXW6YTBOI=\r\n=====",
+	}
+	testStringEncoding(t, "foobar", examples)
+}
+
+func TestDecoderIssue4779(t *testing.T) {
+	encoded := `JRXXEZLNEBUXA43VNUQGI33MN5ZCA43JOQQGC3LFOQWCAY3PNZZWKY3UMV2HK4
+RAMFSGS4DJONUWG2LOM4QGK3DJOQWCA43FMQQGI3YKMVUXK43NN5SCA5DFNVYG64RANFXGG2LENFSH
+K3TUEB2XIIDMMFRG64TFEBSXIIDEN5WG64TFEBWWCZ3OMEQGC3DJOF2WCLRAKV2CAZLONFWQUYLEEB
+WWS3TJNUQHMZLONFQW2LBAOF2WS4ZANZXXG5DSOVSCAZLYMVZGG2LUMF2GS33OEB2WY3DBNVRW6IDM
+MFRG64TJOMQG42LTNEQHK5AKMFWGS4LVNFYCAZLYEBSWCIDDN5WW233EN4QGG33OONSXC5LBOQXCAR
+DVNFZSAYLVORSSA2LSOVZGKIDEN5WG64RANFXAU4TFOBZGK2DFNZSGK4TJOQQGS3RAOZXWY5LQORQX
+IZJAOZSWY2LUEBSXG43FEBRWS3DMOVWSAZDPNRXXEZJAMV2SAZTVM5UWC5BANZ2WY3DBBJYGC4TJMF
+2HK4ROEBCXQY3FOB2GK5LSEBZWS3TUEBXWGY3BMVRWC5BAMN2XA2LEMF2GC5BANZXW4IDQOJXWSZDF
+NZ2CYIDTOVXHIIDJNYFGG5LMOBQSA4LVNEQG6ZTGNFRWSYJAMRSXGZLSOVXHIIDNN5WGY2LUEBQW42
+LNEBUWIIDFON2CA3DBMJXXE5LNFY==
+====`
+	encodedShort := strings.ReplaceAll(encoded, "\n", "")
+
+	dec := NewDecoder(StdEncoding, strings.NewReader(encoded))
+	res1, err := io.ReadAll(dec)
+	if err != nil {
+		t.Errorf("ReadAll failed: %v", err)
+	}
+
+	dec = NewDecoder(StdEncoding, strings.NewReader(encodedShort))
+	var res2 []byte
+	res2, err = io.ReadAll(dec)
+	if err != nil {
+		t.Errorf("ReadAll failed: %v", err)
+	}
+
+	if !bytes.Equal(res1, res2) {
+		t.Error("Decoded results not equal")
+	}
+}
+
+func BenchmarkEncode(b *testing.B) {
+	data := make([]byte, 8192)
+	buf := make([]byte, StdEncoding.EncodedLen(len(data)))
+	b.SetBytes(int64(len(data)))
+	for i := 0; i < b.N; i++ {
+		StdEncoding.Encode(buf, data)
+	}
+}
+
+func BenchmarkEncodeToString(b *testing.B) {
+	data := make([]byte, 8192)
+	b.SetBytes(int64(len(data)))
+	for i := 0; i < b.N; i++ {
+		StdEncoding.EncodeToString(data)
+	}
+}
+
+func BenchmarkDecode(b *testing.B) {
+	data := make([]byte, StdEncoding.EncodedLen(8192))
+	StdEncoding.Encode(data, make([]byte, 8192))
+	buf := make([]byte, 8192)
+	b.SetBytes(int64(len(data)))
+	for i := 0; i < b.N; i++ {
+		StdEncoding.Decode(buf, data)
+	}
+}
+func BenchmarkDecodeString(b *testing.B) {
+	data := StdEncoding.EncodeToString(make([]byte, 8192))
+	b.SetBytes(int64(len(data)))
+	for i := 0; i < b.N; i++ {
+		StdEncoding.DecodeString(data)
+	}
+}
+
+func TestWithCustomPadding(t *testing.T) {
+	for _, testcase := range pairs {
+		defaultPadding := StdEncoding.EncodeToString([]byte(testcase.decoded))
+		customPadding := StdEncoding.WithPadding('@').EncodeToString([]byte(testcase.decoded))
+		expected := strings.ReplaceAll(defaultPadding, "=", "@")
+
+		if expected != customPadding {
+			t.Errorf("Expected custom %s, got %s", expected, customPadding)
+		}
+		if testcase.encoded != defaultPadding {
+			t.Errorf("Expected %s, got %s", testcase.encoded, defaultPadding)
+		}
+	}
+}
+
+func TestWithoutPadding(t *testing.T) {
+	for _, testcase := range pairs {
+		defaultPadding := StdEncoding.EncodeToString([]byte(testcase.decoded))
+		customPadding := StdEncoding.WithPadding(NoPadding).EncodeToString([]byte(testcase.decoded))
+		expected := strings.TrimRight(defaultPadding, "=")
+
+		if expected != customPadding {
+			t.Errorf("Expected custom %s, got %s", expected, customPadding)
+		}
+		if testcase.encoded != defaultPadding {
+			t.Errorf("Expected %s, got %s", testcase.encoded, defaultPadding)
+		}
+	}
+}
+
+func TestDecodeWithPadding(t *testing.T) {
+	encodings := []*Encoding{
+		StdEncoding,
+		StdEncoding.WithPadding('-'),
+		StdEncoding.WithPadding(NoPadding),
+	}
+
+	for i, enc := range encodings {
+		for _, pair := range pairs {
+
+			input := pair.decoded
+			encoded := enc.EncodeToString([]byte(input))
+
+			decoded, err := enc.DecodeString(encoded)
+			if err != nil {
+				t.Errorf("DecodeString Error for encoding %d (%q): %v", i, input, err)
+			}
+
+			if input != string(decoded) {
+				t.Errorf("Unexpected result for encoding %d: got %q; want %q", i, decoded, input)
+			}
+		}
+	}
+}
+
+func TestDecodeWithWrongPadding(t *testing.T) {
+	encoded := StdEncoding.EncodeToString([]byte("foobar"))
+
+	_, err := StdEncoding.WithPadding('-').DecodeString(encoded)
+	if err == nil {
+		t.Error("expected error")
+	}
+
+	_, err = StdEncoding.WithPadding(NoPadding).DecodeString(encoded)
+	if err == nil {
+		t.Error("expected error")
+	}
+}
+
+func TestBufferedDecodingSameError(t *testing.T) {
+	testcases := []struct {
+		prefix            string
+		chunkCombinations [][]string
+		expected          error
+	}{
+		// NBSWY3DPO5XXE3DE == helloworld
+		// Test with "ZZ" as extra input
+		{"helloworld", [][]string{
+			{"NBSW", "Y3DP", "O5XX", "E3DE", "ZZ"},
+			{"NBSWY3DPO5XXE3DE", "ZZ"},
+			{"NBSWY3DPO5XXE3DEZZ"},
+			{"NBS", "WY3", "DPO", "5XX", "E3D", "EZZ"},
+			{"NBSWY3DPO5XXE3", "DEZZ"},
+		}, io.ErrUnexpectedEOF},
+
+		// Test with "ZZY" as extra input
+		{"helloworld", [][]string{
+			{"NBSW", "Y3DP", "O5XX", "E3DE", "ZZY"},
+			{"NBSWY3DPO5XXE3DE", "ZZY"},
+			{"NBSWY3DPO5XXE3DEZZY"},
+			{"NBS", "WY3", "DPO", "5XX", "E3D", "EZZY"},
+			{"NBSWY3DPO5XXE3", "DEZZY"},
+		}, io.ErrUnexpectedEOF},
+
+		// Normal case, this is valid input
+		{"helloworld", [][]string{
+			{"NBSW", "Y3DP", "O5XX", "E3DE"},
+			{"NBSWY3DPO5XXE3DE"},
+			{"NBS", "WY3", "DPO", "5XX", "E3D", "E"},
+			{"NBSWY3DPO5XXE3", "DE"},
+		}, nil},
+
+		// MZXW6YTB = fooba
+		{"fooba", [][]string{
+			{"MZXW6YTBZZ"},
+			{"MZXW6YTBZ", "Z"},
+			{"MZXW6YTB", "ZZ"},
+			{"MZXW6YT", "BZZ"},
+			{"MZXW6Y", "TBZZ"},
+			{"MZXW6Y", "TB", "ZZ"},
+			{"MZXW6", "YTBZZ"},
+			{"MZXW6", "YTB", "ZZ"},
+			{"MZXW6", "YT", "BZZ"},
+		}, io.ErrUnexpectedEOF},
+
+		// Normal case, this is valid input
+		{"fooba", [][]string{
+			{"MZXW6YTB"},
+			{"MZXW6YT", "B"},
+			{"MZXW6Y", "TB"},
+			{"MZXW6", "YTB"},
+			{"MZXW6", "YT", "B"},
+			{"MZXW", "6YTB"},
+			{"MZXW", "6Y", "TB"},
+		}, nil},
+	}
+
+	for _, testcase := range testcases {
+		for _, chunks := range testcase.chunkCombinations {
+			pr, pw := io.Pipe()
+
+			// Write the encoded chunks into the pipe
+			go func() {
+				for _, chunk := range chunks {
+					pw.Write([]byte(chunk))
+				}
+				pw.Close()
+			}()
+
+			decoder := NewDecoder(StdEncoding, pr)
+			_, err := io.ReadAll(decoder)
+
+			if err != testcase.expected {
+				t.Errorf("Expected %v, got %v; case %s %+v", testcase.expected, err, testcase.prefix, chunks)
+			}
+		}
+	}
+}
+
+func TestEncodedDecodedLen(t *testing.T) {
+	type test struct {
+		in      int
+		wantEnc int
+		wantDec int
+	}
+	data := bytes.Repeat([]byte("x"), 100)
+	for _, test := range []struct {
+		name  string
+		enc   *Encoding
+		cases []test
+	}{
+		{"StdEncoding", StdEncoding, []test{
+			{0, 0, 0},
+			{1, 8, 5},
+			{5, 8, 5},
+			{6, 16, 10},
+			{10, 16, 10},
+		}},
+		{"NoPadding", StdEncoding.WithPadding(NoPadding), []test{
+			{0, 0, 0},
+			{1, 2, 1},
+			{2, 4, 2},
+			{5, 8, 5},
+			{6, 10, 6},
+			{7, 12, 7},
+			{10, 16, 10},
+			{11, 18, 11},
+		}},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			for _, tc := range test.cases {
+				encLen := test.enc.EncodedLen(tc.in)
+				decLen := test.enc.DecodedLen(encLen)
+				enc := test.enc.EncodeToString(data[:tc.in])
+				if len(enc) != encLen {
+					t.Fatalf("EncodedLen(%d) = %d but encoded to %q (%d)", tc.in, encLen, enc, len(enc))
+				}
+				if encLen != tc.wantEnc {
+					t.Fatalf("EncodedLen(%d) = %d; want %d", tc.in, encLen, tc.wantEnc)
+				}
+				if decLen != tc.wantDec {
+					t.Fatalf("DecodedLen(%d) = %d; want %d", encLen, decLen, tc.wantDec)
+				}
+			}
+		})
+	}
+}
+
+func TestWithoutPaddingClose(t *testing.T) {
+	encodings := []*Encoding{
+		StdEncoding,
+		StdEncoding.WithPadding(NoPadding),
+	}
+
+	for _, encoding := range encodings {
+		for _, testpair := range pairs {
+
+			var buf bytes.Buffer
+			encoder := NewEncoder(encoding, &buf)
+			encoder.Write([]byte(testpair.decoded))
+			encoder.Close()
+
+			expected := testpair.encoded
+			if encoding.padChar == NoPadding {
+				expected = strings.ReplaceAll(expected, "=", "")
+			}
+
+			res := buf.String()
+
+			if res != expected {
+				t.Errorf("Expected %s got %s; padChar=%d", expected, res, encoding.padChar)
+			}
+		}
+	}
+}
+
+func TestDecodeReadAll(t *testing.T) {
+	encodings := []*Encoding{
+		StdEncoding,
+		StdEncoding.WithPadding(NoPadding),
+	}
+
+	for _, pair := range pairs {
+		for encIndex, encoding := range encodings {
+			encoded := pair.encoded
+			if encoding.padChar == NoPadding {
+				encoded = strings.ReplaceAll(encoded, "=", "")
+			}
+
+			decReader, err := io.ReadAll(NewDecoder(encoding, strings.NewReader(encoded)))
+			if err != nil {
+				t.Errorf("NewDecoder error: %v", err)
+			}
+
+			if pair.decoded != string(decReader) {
+				t.Errorf("Expected %s got %s; Encoding %d", pair.decoded, decReader, encIndex)
+			}
+		}
+	}
+}
+
+func TestDecodeSmallBuffer(t *testing.T) {
+	encodings := []*Encoding{
+		StdEncoding,
+		StdEncoding.WithPadding(NoPadding),
+	}
+
+	for bufferSize := 1; bufferSize < 200; bufferSize++ {
+		for _, pair := range pairs {
+			for encIndex, encoding := range encodings {
+				encoded := pair.encoded
+				if encoding.padChar == NoPadding {
+					encoded = strings.ReplaceAll(encoded, "=", "")
+				}
+
+				decoder := NewDecoder(encoding, strings.NewReader(encoded))
+
+				var allRead []byte
+
+				for {
+					buf := make([]byte, bufferSize)
+					n, err := decoder.Read(buf)
+					allRead = append(allRead, buf[0:n]...)
+					if err == io.EOF {
+						break
+					}
+					if err != nil {
+						t.Error(err)
+					}
+				}
+
+				if pair.decoded != string(allRead) {
+					t.Errorf("Expected %s got %s; Encoding %d; bufferSize %d", pair.decoded, allRead, encIndex, bufferSize)
+				}
+			}
+		}
+	}
+}
diff --git a/src/encoding/base32/example_test.go b/src/encoding/base32/example_test.go
new file mode 100644
index 0000000..251624f
--- /dev/null
+++ b/src/encoding/base32/example_test.go
@@ -0,0 +1,68 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Keep in sync with ../base64/example_test.go.
+
+package base32_test
+
+import (
+	"encoding/base32"
+	"fmt"
+	"os"
+)
+
+func ExampleEncoding_EncodeToString() {
+	data := []byte("any + old & data")
+	str := base32.StdEncoding.EncodeToString(data)
+	fmt.Println(str)
+	// Output:
+	// MFXHSIBLEBXWYZBAEYQGIYLUME======
+}
+
+func ExampleEncoding_Encode() {
+	data := []byte("Hello, world!")
+	dst := make([]byte, base32.StdEncoding.EncodedLen(len(data)))
+	base32.StdEncoding.Encode(dst, data)
+	fmt.Println(string(dst))
+	// Output:
+	// JBSWY3DPFQQHO33SNRSCC===
+}
+
+func ExampleEncoding_DecodeString() {
+	str := "ONXW2ZJAMRQXIYJAO5UXI2BAAAQGC3TEEDX3XPY="
+	data, err := base32.StdEncoding.DecodeString(str)
+	if err != nil {
+		fmt.Println("error:", err)
+		return
+	}
+	fmt.Printf("%q\n", data)
+	// Output:
+	// "some data with \x00 and \ufeff"
+}
+
+func ExampleEncoding_Decode() {
+	str := "JBSWY3DPFQQHO33SNRSCC==="
+	dst := make([]byte, base32.StdEncoding.DecodedLen(len(str)))
+	n, err := base32.StdEncoding.Decode(dst, []byte(str))
+	if err != nil {
+		fmt.Println("decode error:", err)
+		return
+	}
+	dst = dst[:n]
+	fmt.Printf("%q\n", dst)
+	// Output:
+	// "Hello, world!"
+}
+
+func ExampleNewEncoder() {
+	input := []byte("foo\x00bar")
+	encoder := base32.NewEncoder(base32.StdEncoding, os.Stdout)
+	encoder.Write(input)
+	// Must close the encoder when finished to flush any partial blocks.
+	// If you comment out the following line, the last partial block "r"
+	// won't be encoded.
+	encoder.Close()
+	// Output:
+	// MZXW6ADCMFZA====
+}
diff --git a/src/encoding/base64/base64.go b/src/encoding/base64/base64.go
new file mode 100644
index 0000000..4a3e590
--- /dev/null
+++ b/src/encoding/base64/base64.go
@@ -0,0 +1,612 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package base64 implements base64 encoding as specified by RFC 4648.
+package base64
+
+import (
+	"encoding/binary"
+	"io"
+	"strconv"
+)
+
+/*
+ * Encodings
+ */
+
+// An Encoding is a radix 64 encoding/decoding scheme, defined by a
+// 64-character alphabet. The most common encoding is the "base64"
+// encoding defined in RFC 4648 and used in MIME (RFC 2045) and PEM
+// (RFC 1421).  RFC 4648 also defines an alternate encoding, which is
+// the standard encoding with - and _ substituted for + and /.
+type Encoding struct {
+	encode    [64]byte
+	decodeMap [256]byte
+	padChar   rune
+	strict    bool
+}
+
+const (
+	StdPadding rune = '=' // Standard padding character
+	NoPadding  rune = -1  // No padding
+)
+
+const encodeStd = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
+const encodeURL = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_"
+
+// NewEncoding returns a new padded Encoding defined by the given alphabet,
+// which must be a 64-byte string that does not contain the padding character
+// or CR / LF ('\r', '\n').
+// The resulting Encoding uses the default padding character ('='),
+// which may be changed or disabled via WithPadding.
+func NewEncoding(encoder string) *Encoding {
+	if len(encoder) != 64 {
+		panic("encoding alphabet is not 64-bytes long")
+	}
+	for i := 0; i < len(encoder); i++ {
+		if encoder[i] == '\n' || encoder[i] == '\r' {
+			panic("encoding alphabet contains newline character")
+		}
+	}
+
+	e := new(Encoding)
+	e.padChar = StdPadding
+	copy(e.encode[:], encoder)
+
+	for i := 0; i < len(e.decodeMap); i++ {
+		e.decodeMap[i] = 0xFF
+	}
+	for i := 0; i < len(encoder); i++ {
+		e.decodeMap[encoder[i]] = byte(i)
+	}
+	return e
+}
+
+// WithPadding creates a new encoding identical to enc except
+// with a specified padding character, or NoPadding to disable padding.
+// The padding character must not be '\r' or '\n', must not
+// be contained in the encoding's alphabet and must be a rune equal or
+// below '\xff'.
+func (enc Encoding) WithPadding(padding rune) *Encoding {
+	if padding == '\r' || padding == '\n' || padding > 0xff {
+		panic("invalid padding")
+	}
+
+	for i := 0; i < len(enc.encode); i++ {
+		if rune(enc.encode[i]) == padding {
+			panic("padding contained in alphabet")
+		}
+	}
+
+	enc.padChar = padding
+	return &enc
+}
+
+// Strict creates a new encoding identical to enc except with
+// strict decoding enabled. In this mode, the decoder requires that
+// trailing padding bits are zero, as described in RFC 4648 section 3.5.
+//
+// Note that the input is still malleable, as new line characters
+// (CR and LF) are still ignored.
+func (enc Encoding) Strict() *Encoding {
+	enc.strict = true
+	return &enc
+}
+
+// StdEncoding is the standard base64 encoding, as defined in
+// RFC 4648.
+var StdEncoding = NewEncoding(encodeStd)
+
+// URLEncoding is the alternate base64 encoding defined in RFC 4648.
+// It is typically used in URLs and file names.
+var URLEncoding = NewEncoding(encodeURL)
+
+// RawStdEncoding is the standard raw, unpadded base64 encoding,
+// as defined in RFC 4648 section 3.2.
+// This is the same as StdEncoding but omits padding characters.
+var RawStdEncoding = StdEncoding.WithPadding(NoPadding)
+
+// RawURLEncoding is the unpadded alternate base64 encoding defined in RFC 4648.
+// It is typically used in URLs and file names.
+// This is the same as URLEncoding but omits padding characters.
+var RawURLEncoding = URLEncoding.WithPadding(NoPadding)
+
+/*
+ * Encoder
+ */
+
+// Encode encodes src using the encoding enc, writing
+// EncodedLen(len(src)) bytes to dst.
+//
+// The encoding pads the output to a multiple of 4 bytes,
+// so Encode is not appropriate for use on individual blocks
+// of a large data stream. Use NewEncoder() instead.
+func (enc *Encoding) Encode(dst, src []byte) {
+	if len(src) == 0 {
+		return
+	}
+	// enc is a pointer receiver, so the use of enc.encode within the hot
+	// loop below means a nil check at every operation. Lift that nil check
+	// outside of the loop to speed up the encoder.
+	_ = enc.encode
+
+	di, si := 0, 0
+	n := (len(src) / 3) * 3
+	for si < n {
+		// Convert 3x 8bit source bytes into 4 bytes
+		val := uint(src[si+0])<<16 | uint(src[si+1])<<8 | uint(src[si+2])
+
+		dst[di+0] = enc.encode[val>>18&0x3F]
+		dst[di+1] = enc.encode[val>>12&0x3F]
+		dst[di+2] = enc.encode[val>>6&0x3F]
+		dst[di+3] = enc.encode[val&0x3F]
+
+		si += 3
+		di += 4
+	}
+
+	remain := len(src) - si
+	if remain == 0 {
+		return
+	}
+	// Add the remaining small block
+	val := uint(src[si+0]) << 16
+	if remain == 2 {
+		val |= uint(src[si+1]) << 8
+	}
+
+	dst[di+0] = enc.encode[val>>18&0x3F]
+	dst[di+1] = enc.encode[val>>12&0x3F]
+
+	switch remain {
+	case 2:
+		dst[di+2] = enc.encode[val>>6&0x3F]
+		if enc.padChar != NoPadding {
+			dst[di+3] = byte(enc.padChar)
+		}
+	case 1:
+		if enc.padChar != NoPadding {
+			dst[di+2] = byte(enc.padChar)
+			dst[di+3] = byte(enc.padChar)
+		}
+	}
+}
+
+// EncodeToString returns the base64 encoding of src.
+func (enc *Encoding) EncodeToString(src []byte) string {
+	buf := make([]byte, enc.EncodedLen(len(src)))
+	enc.Encode(buf, src)
+	return string(buf)
+}
+
+type encoder struct {
+	err  error
+	enc  *Encoding
+	w    io.Writer
+	buf  [3]byte    // buffered data waiting to be encoded
+	nbuf int        // number of bytes in buf
+	out  [1024]byte // output buffer
+}
+
+func (e *encoder) Write(p []byte) (n int, err error) {
+	if e.err != nil {
+		return 0, e.err
+	}
+
+	// Leading fringe.
+	if e.nbuf > 0 {
+		var i int
+		for i = 0; i < len(p) && e.nbuf < 3; i++ {
+			e.buf[e.nbuf] = p[i]
+			e.nbuf++
+		}
+		n += i
+		p = p[i:]
+		if e.nbuf < 3 {
+			return
+		}
+		e.enc.Encode(e.out[:], e.buf[:])
+		if _, e.err = e.w.Write(e.out[:4]); e.err != nil {
+			return n, e.err
+		}
+		e.nbuf = 0
+	}
+
+	// Large interior chunks.
+	for len(p) >= 3 {
+		nn := len(e.out) / 4 * 3
+		if nn > len(p) {
+			nn = len(p)
+			nn -= nn % 3
+		}
+		e.enc.Encode(e.out[:], p[:nn])
+		if _, e.err = e.w.Write(e.out[0 : nn/3*4]); e.err != nil {
+			return n, e.err
+		}
+		n += nn
+		p = p[nn:]
+	}
+
+	// Trailing fringe.
+	copy(e.buf[:], p)
+	e.nbuf = len(p)
+	n += len(p)
+	return
+}
+
+// Close flushes any pending output from the encoder.
+// It is an error to call Write after calling Close.
+func (e *encoder) Close() error {
+	// If there's anything left in the buffer, flush it out
+	if e.err == nil && e.nbuf > 0 {
+		e.enc.Encode(e.out[:], e.buf[:e.nbuf])
+		_, e.err = e.w.Write(e.out[:e.enc.EncodedLen(e.nbuf)])
+		e.nbuf = 0
+	}
+	return e.err
+}
+
+// NewEncoder returns a new base64 stream encoder. Data written to
+// the returned writer will be encoded using enc and then written to w.
+// Base64 encodings operate in 4-byte blocks; when finished
+// writing, the caller must Close the returned encoder to flush any
+// partially written blocks.
+func NewEncoder(enc *Encoding, w io.Writer) io.WriteCloser {
+	return &encoder{enc: enc, w: w}
+}
+
+// EncodedLen returns the length in bytes of the base64 encoding
+// of an input buffer of length n.
+func (enc *Encoding) EncodedLen(n int) int {
+	if enc.padChar == NoPadding {
+		return (n*8 + 5) / 6 // minimum # chars at 6 bits per char
+	}
+	return (n + 2) / 3 * 4 // minimum # 4-char quanta, 3 bytes each
+}
+
+/*
+ * Decoder
+ */
+
+type CorruptInputError int64
+
+func (e CorruptInputError) Error() string {
+	return "illegal base64 data at input byte " + strconv.FormatInt(int64(e), 10)
+}
+
+// decodeQuantum decodes up to 4 base64 bytes. The received parameters are
+// the destination buffer dst, the source buffer src and an index in the
+// source buffer si.
+// It returns the number of bytes read from src, the number of bytes written
+// to dst, and an error, if any.
+func (enc *Encoding) decodeQuantum(dst, src []byte, si int) (nsi, n int, err error) {
+	// Decode quantum using the base64 alphabet
+	var dbuf [4]byte
+	dlen := 4
+
+	// Lift the nil check outside of the loop.
+	_ = enc.decodeMap
+
+	for j := 0; j < len(dbuf); j++ {
+		if len(src) == si {
+			switch {
+			case j == 0:
+				return si, 0, nil
+			case j == 1, enc.padChar != NoPadding:
+				return si, 0, CorruptInputError(si - j)
+			}
+			dlen = j
+			break
+		}
+		in := src[si]
+		si++
+
+		out := enc.decodeMap[in]
+		if out != 0xff {
+			dbuf[j] = out
+			continue
+		}
+
+		if in == '\n' || in == '\r' {
+			j--
+			continue
+		}
+
+		if rune(in) != enc.padChar {
+			return si, 0, CorruptInputError(si - 1)
+		}
+
+		// We've reached the end and there's padding
+		switch j {
+		case 0, 1:
+			// incorrect padding
+			return si, 0, CorruptInputError(si - 1)
+		case 2:
+			// "==" is expected, the first "=" is already consumed.
+			// skip over newlines
+			for si < len(src) && (src[si] == '\n' || src[si] == '\r') {
+				si++
+			}
+			if si == len(src) {
+				// not enough padding
+				return si, 0, CorruptInputError(len(src))
+			}
+			if rune(src[si]) != enc.padChar {
+				// incorrect padding
+				return si, 0, CorruptInputError(si - 1)
+			}
+
+			si++
+		}
+
+		// skip over newlines
+		for si < len(src) && (src[si] == '\n' || src[si] == '\r') {
+			si++
+		}
+		if si < len(src) {
+			// trailing garbage
+			err = CorruptInputError(si)
+		}
+		dlen = j
+		break
+	}
+
+	// Convert 4x 6bit source bytes into 3 bytes
+	val := uint(dbuf[0])<<18 | uint(dbuf[1])<<12 | uint(dbuf[2])<<6 | uint(dbuf[3])
+	dbuf[2], dbuf[1], dbuf[0] = byte(val>>0), byte(val>>8), byte(val>>16)
+	switch dlen {
+	case 4:
+		dst[2] = dbuf[2]
+		dbuf[2] = 0
+		fallthrough
+	case 3:
+		dst[1] = dbuf[1]
+		if enc.strict && dbuf[2] != 0 {
+			return si, 0, CorruptInputError(si - 1)
+		}
+		dbuf[1] = 0
+		fallthrough
+	case 2:
+		dst[0] = dbuf[0]
+		if enc.strict && (dbuf[1] != 0 || dbuf[2] != 0) {
+			return si, 0, CorruptInputError(si - 2)
+		}
+	}
+
+	return si, dlen - 1, err
+}
+
+// DecodeString returns the bytes represented by the base64 string s.
+func (enc *Encoding) DecodeString(s string) ([]byte, error) {
+	dbuf := make([]byte, enc.DecodedLen(len(s)))
+	n, err := enc.Decode(dbuf, []byte(s))
+	return dbuf[:n], err
+}
+
+type decoder struct {
+	err     error
+	readErr error // error from r.Read
+	enc     *Encoding
+	r       io.Reader
+	buf     [1024]byte // leftover input
+	nbuf    int
+	out     []byte // leftover decoded output
+	outbuf  [1024 / 4 * 3]byte
+}
+
+func (d *decoder) Read(p []byte) (n int, err error) {
+	// Use leftover decoded output from last read.
+	if len(d.out) > 0 {
+		n = copy(p, d.out)
+		d.out = d.out[n:]
+		return n, nil
+	}
+
+	if d.err != nil {
+		return 0, d.err
+	}
+
+	// This code assumes that d.r strips supported whitespace ('\r' and '\n').
+
+	// Refill buffer.
+	for d.nbuf < 4 && d.readErr == nil {
+		nn := len(p) / 3 * 4
+		if nn < 4 {
+			nn = 4
+		}
+		if nn > len(d.buf) {
+			nn = len(d.buf)
+		}
+		nn, d.readErr = d.r.Read(d.buf[d.nbuf:nn])
+		d.nbuf += nn
+	}
+
+	if d.nbuf < 4 {
+		if d.enc.padChar == NoPadding && d.nbuf > 0 {
+			// Decode final fragment, without padding.
+			var nw int
+			nw, d.err = d.enc.Decode(d.outbuf[:], d.buf[:d.nbuf])
+			d.nbuf = 0
+			d.out = d.outbuf[:nw]
+			n = copy(p, d.out)
+			d.out = d.out[n:]
+			if n > 0 || len(p) == 0 && len(d.out) > 0 {
+				return n, nil
+			}
+			if d.err != nil {
+				return 0, d.err
+			}
+		}
+		d.err = d.readErr
+		if d.err == io.EOF && d.nbuf > 0 {
+			d.err = io.ErrUnexpectedEOF
+		}
+		return 0, d.err
+	}
+
+	// Decode chunk into p, or d.out and then p if p is too small.
+	nr := d.nbuf / 4 * 4
+	nw := d.nbuf / 4 * 3
+	if nw > len(p) {
+		nw, d.err = d.enc.Decode(d.outbuf[:], d.buf[:nr])
+		d.out = d.outbuf[:nw]
+		n = copy(p, d.out)
+		d.out = d.out[n:]
+	} else {
+		n, d.err = d.enc.Decode(p, d.buf[:nr])
+	}
+	d.nbuf -= nr
+	copy(d.buf[:d.nbuf], d.buf[nr:])
+	return n, d.err
+}
+
+// Decode decodes src using the encoding enc. It writes at most
+// DecodedLen(len(src)) bytes to dst and returns the number of bytes
+// written. If src contains invalid base64 data, it will return the
+// number of bytes successfully written and CorruptInputError.
+// New line characters (\r and \n) are ignored.
+func (enc *Encoding) Decode(dst, src []byte) (n int, err error) {
+	if len(src) == 0 {
+		return 0, nil
+	}
+
+	// Lift the nil check outside of the loop. enc.decodeMap is directly
+	// used later in this function, to let the compiler know that the
+	// receiver can't be nil.
+	_ = enc.decodeMap
+
+	si := 0
+	for strconv.IntSize >= 64 && len(src)-si >= 8 && len(dst)-n >= 8 {
+		src2 := src[si : si+8]
+		if dn, ok := assemble64(
+			enc.decodeMap[src2[0]],
+			enc.decodeMap[src2[1]],
+			enc.decodeMap[src2[2]],
+			enc.decodeMap[src2[3]],
+			enc.decodeMap[src2[4]],
+			enc.decodeMap[src2[5]],
+			enc.decodeMap[src2[6]],
+			enc.decodeMap[src2[7]],
+		); ok {
+			binary.BigEndian.PutUint64(dst[n:], dn)
+			n += 6
+			si += 8
+		} else {
+			var ninc int
+			si, ninc, err = enc.decodeQuantum(dst[n:], src, si)
+			n += ninc
+			if err != nil {
+				return n, err
+			}
+		}
+	}
+
+	for len(src)-si >= 4 && len(dst)-n >= 4 {
+		src2 := src[si : si+4]
+		if dn, ok := assemble32(
+			enc.decodeMap[src2[0]],
+			enc.decodeMap[src2[1]],
+			enc.decodeMap[src2[2]],
+			enc.decodeMap[src2[3]],
+		); ok {
+			binary.BigEndian.PutUint32(dst[n:], dn)
+			n += 3
+			si += 4
+		} else {
+			var ninc int
+			si, ninc, err = enc.decodeQuantum(dst[n:], src, si)
+			n += ninc
+			if err != nil {
+				return n, err
+			}
+		}
+	}
+
+	for si < len(src) {
+		var ninc int
+		si, ninc, err = enc.decodeQuantum(dst[n:], src, si)
+		n += ninc
+		if err != nil {
+			return n, err
+		}
+	}
+	return n, err
+}
+
+// assemble32 assembles 4 base64 digits into 3 bytes.
+// Each digit comes from the decode map, and will be 0xff
+// if it came from an invalid character.
+func assemble32(n1, n2, n3, n4 byte) (dn uint32, ok bool) {
+	// Check that all the digits are valid. If any of them was 0xff, their
+	// bitwise OR will be 0xff.
+	if n1|n2|n3|n4 == 0xff {
+		return 0, false
+	}
+	return uint32(n1)<<26 |
+			uint32(n2)<<20 |
+			uint32(n3)<<14 |
+			uint32(n4)<<8,
+		true
+}
+
+// assemble64 assembles 8 base64 digits into 6 bytes.
+// Each digit comes from the decode map, and will be 0xff
+// if it came from an invalid character.
+func assemble64(n1, n2, n3, n4, n5, n6, n7, n8 byte) (dn uint64, ok bool) {
+	// Check that all the digits are valid. If any of them was 0xff, their
+	// bitwise OR will be 0xff.
+	if n1|n2|n3|n4|n5|n6|n7|n8 == 0xff {
+		return 0, false
+	}
+	return uint64(n1)<<58 |
+			uint64(n2)<<52 |
+			uint64(n3)<<46 |
+			uint64(n4)<<40 |
+			uint64(n5)<<34 |
+			uint64(n6)<<28 |
+			uint64(n7)<<22 |
+			uint64(n8)<<16,
+		true
+}
+
+type newlineFilteringReader struct {
+	wrapped io.Reader
+}
+
+func (r *newlineFilteringReader) Read(p []byte) (int, error) {
+	n, err := r.wrapped.Read(p)
+	for n > 0 {
+		offset := 0
+		for i, b := range p[:n] {
+			if b != '\r' && b != '\n' {
+				if i != offset {
+					p[offset] = b
+				}
+				offset++
+			}
+		}
+		if offset > 0 {
+			return offset, err
+		}
+		// Previous buffer entirely whitespace, read again
+		n, err = r.wrapped.Read(p)
+	}
+	return n, err
+}
+
+// NewDecoder constructs a new base64 stream decoder.
+func NewDecoder(enc *Encoding, r io.Reader) io.Reader {
+	return &decoder{enc: enc, r: &newlineFilteringReader{r}}
+}
+
+// DecodedLen returns the maximum length in bytes of the decoded data
+// corresponding to n bytes of base64-encoded data.
+func (enc *Encoding) DecodedLen(n int) int {
+	if enc.padChar == NoPadding {
+		// Unpadded data may end with partial block of 2-3 characters.
+		return n * 6 / 8
+	}
+	// Padded base64 should always be a multiple of 4 characters in length.
+	return n / 4 * 3
+}
diff --git a/src/encoding/base64/base64_test.go b/src/encoding/base64/base64_test.go
new file mode 100644
index 0000000..57256a3
--- /dev/null
+++ b/src/encoding/base64/base64_test.go
@@ -0,0 +1,530 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package base64
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"reflect"
+	"runtime/debug"
+	"strings"
+	"testing"
+	"time"
+)
+
+type testpair struct {
+	decoded, encoded string
+}
+
+var pairs = []testpair{
+	// RFC 3548 examples
+	{"\x14\xfb\x9c\x03\xd9\x7e", "FPucA9l+"},
+	{"\x14\xfb\x9c\x03\xd9", "FPucA9k="},
+	{"\x14\xfb\x9c\x03", "FPucAw=="},
+
+	// RFC 4648 examples
+	{"", ""},
+	{"f", "Zg=="},
+	{"fo", "Zm8="},
+	{"foo", "Zm9v"},
+	{"foob", "Zm9vYg=="},
+	{"fooba", "Zm9vYmE="},
+	{"foobar", "Zm9vYmFy"},
+
+	// Wikipedia examples
+	{"sure.", "c3VyZS4="},
+	{"sure", "c3VyZQ=="},
+	{"sur", "c3Vy"},
+	{"su", "c3U="},
+	{"leasure.", "bGVhc3VyZS4="},
+	{"easure.", "ZWFzdXJlLg=="},
+	{"asure.", "YXN1cmUu"},
+	{"sure.", "c3VyZS4="},
+}
+
+// Do nothing to a reference base64 string (leave in standard format)
+func stdRef(ref string) string {
+	return ref
+}
+
+// Convert a reference string to URL-encoding
+func urlRef(ref string) string {
+	ref = strings.ReplaceAll(ref, "+", "-")
+	ref = strings.ReplaceAll(ref, "/", "_")
+	return ref
+}
+
+// Convert a reference string to raw, unpadded format
+func rawRef(ref string) string {
+	return strings.TrimRight(ref, "=")
+}
+
+// Both URL and unpadding conversions
+func rawURLRef(ref string) string {
+	return rawRef(urlRef(ref))
+}
+
+// A nonstandard encoding with a funny padding character, for testing
+var funnyEncoding = NewEncoding(encodeStd).WithPadding(rune('@'))
+
+func funnyRef(ref string) string {
+	return strings.ReplaceAll(ref, "=", "@")
+}
+
+type encodingTest struct {
+	enc  *Encoding           // Encoding to test
+	conv func(string) string // Reference string converter
+}
+
+var encodingTests = []encodingTest{
+	{StdEncoding, stdRef},
+	{URLEncoding, urlRef},
+	{RawStdEncoding, rawRef},
+	{RawURLEncoding, rawURLRef},
+	{funnyEncoding, funnyRef},
+	{StdEncoding.Strict(), stdRef},
+	{URLEncoding.Strict(), urlRef},
+	{RawStdEncoding.Strict(), rawRef},
+	{RawURLEncoding.Strict(), rawURLRef},
+	{funnyEncoding.Strict(), funnyRef},
+}
+
+var bigtest = testpair{
+	"Twas brillig, and the slithy toves",
+	"VHdhcyBicmlsbGlnLCBhbmQgdGhlIHNsaXRoeSB0b3Zlcw==",
+}
+
+func testEqual(t *testing.T, msg string, args ...any) bool {
+	t.Helper()
+	if args[len(args)-2] != args[len(args)-1] {
+		t.Errorf(msg, args...)
+		return false
+	}
+	return true
+}
+
+func TestEncode(t *testing.T) {
+	for _, p := range pairs {
+		for _, tt := range encodingTests {
+			got := tt.enc.EncodeToString([]byte(p.decoded))
+			testEqual(t, "Encode(%q) = %q, want %q", p.decoded,
+				got, tt.conv(p.encoded))
+		}
+	}
+}
+
+func TestEncoder(t *testing.T) {
+	for _, p := range pairs {
+		bb := &bytes.Buffer{}
+		encoder := NewEncoder(StdEncoding, bb)
+		encoder.Write([]byte(p.decoded))
+		encoder.Close()
+		testEqual(t, "Encode(%q) = %q, want %q", p.decoded, bb.String(), p.encoded)
+	}
+}
+
+func TestEncoderBuffering(t *testing.T) {
+	input := []byte(bigtest.decoded)
+	for bs := 1; bs <= 12; bs++ {
+		bb := &bytes.Buffer{}
+		encoder := NewEncoder(StdEncoding, bb)
+		for pos := 0; pos < len(input); pos += bs {
+			end := pos + bs
+			if end > len(input) {
+				end = len(input)
+			}
+			n, err := encoder.Write(input[pos:end])
+			testEqual(t, "Write(%q) gave error %v, want %v", input[pos:end], err, error(nil))
+			testEqual(t, "Write(%q) gave length %v, want %v", input[pos:end], n, end-pos)
+		}
+		err := encoder.Close()
+		testEqual(t, "Close gave error %v, want %v", err, error(nil))
+		testEqual(t, "Encoding/%d of %q = %q, want %q", bs, bigtest.decoded, bb.String(), bigtest.encoded)
+	}
+}
+
+func TestDecode(t *testing.T) {
+	for _, p := range pairs {
+		for _, tt := range encodingTests {
+			encoded := tt.conv(p.encoded)
+			dbuf := make([]byte, tt.enc.DecodedLen(len(encoded)))
+			count, err := tt.enc.Decode(dbuf, []byte(encoded))
+			testEqual(t, "Decode(%q) = error %v, want %v", encoded, err, error(nil))
+			testEqual(t, "Decode(%q) = length %v, want %v", encoded, count, len(p.decoded))
+			testEqual(t, "Decode(%q) = %q, want %q", encoded, string(dbuf[0:count]), p.decoded)
+
+			dbuf, err = tt.enc.DecodeString(encoded)
+			testEqual(t, "DecodeString(%q) = error %v, want %v", encoded, err, error(nil))
+			testEqual(t, "DecodeString(%q) = %q, want %q", encoded, string(dbuf), p.decoded)
+		}
+	}
+}
+
+func TestDecoder(t *testing.T) {
+	for _, p := range pairs {
+		decoder := NewDecoder(StdEncoding, strings.NewReader(p.encoded))
+		dbuf := make([]byte, StdEncoding.DecodedLen(len(p.encoded)))
+		count, err := decoder.Read(dbuf)
+		if err != nil && err != io.EOF {
+			t.Fatal("Read failed", err)
+		}
+		testEqual(t, "Read from %q = length %v, want %v", p.encoded, count, len(p.decoded))
+		testEqual(t, "Decoding of %q = %q, want %q", p.encoded, string(dbuf[0:count]), p.decoded)
+		if err != io.EOF {
+			_, err = decoder.Read(dbuf)
+		}
+		testEqual(t, "Read from %q = %v, want %v", p.encoded, err, io.EOF)
+	}
+}
+
+func TestDecoderBuffering(t *testing.T) {
+	for bs := 1; bs <= 12; bs++ {
+		decoder := NewDecoder(StdEncoding, strings.NewReader(bigtest.encoded))
+		buf := make([]byte, len(bigtest.decoded)+12)
+		var total int
+		var n int
+		var err error
+		for total = 0; total < len(bigtest.decoded) && err == nil; {
+			n, err = decoder.Read(buf[total : total+bs])
+			total += n
+		}
+		if err != nil && err != io.EOF {
+			t.Errorf("Read from %q at pos %d = %d, unexpected error %v", bigtest.encoded, total, n, err)
+		}
+		testEqual(t, "Decoding/%d of %q = %q, want %q", bs, bigtest.encoded, string(buf[0:total]), bigtest.decoded)
+	}
+}
+
+func TestDecodeCorrupt(t *testing.T) {
+	testCases := []struct {
+		input  string
+		offset int // -1 means no corruption.
+	}{
+		{"", -1},
+		{"\n", -1},
+		{"AAA=\n", -1},
+		{"AAAA\n", -1},
+		{"!!!!", 0},
+		{"====", 0},
+		{"x===", 1},
+		{"=AAA", 0},
+		{"A=AA", 1},
+		{"AA=A", 2},
+		{"AA==A", 4},
+		{"AAA=AAAA", 4},
+		{"AAAAA", 4},
+		{"AAAAAA", 4},
+		{"A=", 1},
+		{"A==", 1},
+		{"AA=", 3},
+		{"AA==", -1},
+		{"AAA=", -1},
+		{"AAAA", -1},
+		{"AAAAAA=", 7},
+		{"YWJjZA=====", 8},
+		{"A!\n", 1},
+		{"A=\n", 1},
+	}
+	for _, tc := range testCases {
+		dbuf := make([]byte, StdEncoding.DecodedLen(len(tc.input)))
+		_, err := StdEncoding.Decode(dbuf, []byte(tc.input))
+		if tc.offset == -1 {
+			if err != nil {
+				t.Error("Decoder wrongly detected corruption in", tc.input)
+			}
+			continue
+		}
+		switch err := err.(type) {
+		case CorruptInputError:
+			testEqual(t, "Corruption in %q at offset %v, want %v", tc.input, int(err), tc.offset)
+		default:
+			t.Error("Decoder failed to detect corruption in", tc)
+		}
+	}
+}
+
+func TestDecodeBounds(t *testing.T) {
+	var buf [32]byte
+	s := StdEncoding.EncodeToString(buf[:])
+	defer func() {
+		if err := recover(); err != nil {
+			t.Fatalf("Decode panicked unexpectedly: %v\n%s", err, debug.Stack())
+		}
+	}()
+	n, err := StdEncoding.Decode(buf[:], []byte(s))
+	if n != len(buf) || err != nil {
+		t.Fatalf("StdEncoding.Decode = %d, %v, want %d, nil", n, err, len(buf))
+	}
+}
+
+func TestEncodedLen(t *testing.T) {
+	for _, tt := range []struct {
+		enc  *Encoding
+		n    int
+		want int
+	}{
+		{RawStdEncoding, 0, 0},
+		{RawStdEncoding, 1, 2},
+		{RawStdEncoding, 2, 3},
+		{RawStdEncoding, 3, 4},
+		{RawStdEncoding, 7, 10},
+		{StdEncoding, 0, 0},
+		{StdEncoding, 1, 4},
+		{StdEncoding, 2, 4},
+		{StdEncoding, 3, 4},
+		{StdEncoding, 4, 8},
+		{StdEncoding, 7, 12},
+	} {
+		if got := tt.enc.EncodedLen(tt.n); got != tt.want {
+			t.Errorf("EncodedLen(%d): got %d, want %d", tt.n, got, tt.want)
+		}
+	}
+}
+
+func TestDecodedLen(t *testing.T) {
+	for _, tt := range []struct {
+		enc  *Encoding
+		n    int
+		want int
+	}{
+		{RawStdEncoding, 0, 0},
+		{RawStdEncoding, 2, 1},
+		{RawStdEncoding, 3, 2},
+		{RawStdEncoding, 4, 3},
+		{RawStdEncoding, 10, 7},
+		{StdEncoding, 0, 0},
+		{StdEncoding, 4, 3},
+		{StdEncoding, 8, 6},
+	} {
+		if got := tt.enc.DecodedLen(tt.n); got != tt.want {
+			t.Errorf("DecodedLen(%d): got %d, want %d", tt.n, got, tt.want)
+		}
+	}
+}
+
+func TestBig(t *testing.T) {
+	n := 3*1000 + 1
+	raw := make([]byte, n)
+	const alpha = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
+	for i := 0; i < n; i++ {
+		raw[i] = alpha[i%len(alpha)]
+	}
+	encoded := new(bytes.Buffer)
+	w := NewEncoder(StdEncoding, encoded)
+	nn, err := w.Write(raw)
+	if nn != n || err != nil {
+		t.Fatalf("Encoder.Write(raw) = %d, %v want %d, nil", nn, err, n)
+	}
+	err = w.Close()
+	if err != nil {
+		t.Fatalf("Encoder.Close() = %v want nil", err)
+	}
+	decoded, err := io.ReadAll(NewDecoder(StdEncoding, encoded))
+	if err != nil {
+		t.Fatalf("io.ReadAll(NewDecoder(...)): %v", err)
+	}
+
+	if !bytes.Equal(raw, decoded) {
+		var i int
+		for i = 0; i < len(decoded) && i < len(raw); i++ {
+			if decoded[i] != raw[i] {
+				break
+			}
+		}
+		t.Errorf("Decode(Encode(%d-byte string)) failed at offset %d", n, i)
+	}
+}
+
+func TestNewLineCharacters(t *testing.T) {
+	// Each of these should decode to the string "sure", without errors.
+	const expected = "sure"
+	examples := []string{
+		"c3VyZQ==",
+		"c3VyZQ==\r",
+		"c3VyZQ==\n",
+		"c3VyZQ==\r\n",
+		"c3VyZ\r\nQ==",
+		"c3V\ryZ\nQ==",
+		"c3V\nyZ\rQ==",
+		"c3VyZ\nQ==",
+		"c3VyZQ\n==",
+		"c3VyZQ=\n=",
+		"c3VyZQ=\r\n\r\n=",
+	}
+	for _, e := range examples {
+		buf, err := StdEncoding.DecodeString(e)
+		if err != nil {
+			t.Errorf("Decode(%q) failed: %v", e, err)
+			continue
+		}
+		if s := string(buf); s != expected {
+			t.Errorf("Decode(%q) = %q, want %q", e, s, expected)
+		}
+	}
+}
+
+type nextRead struct {
+	n   int   // bytes to return
+	err error // error to return
+}
+
+// faultInjectReader returns data from source, rate-limited
+// and with the errors as written to nextc.
+type faultInjectReader struct {
+	source string
+	nextc  <-chan nextRead
+}
+
+func (r *faultInjectReader) Read(p []byte) (int, error) {
+	nr := <-r.nextc
+	if len(p) > nr.n {
+		p = p[:nr.n]
+	}
+	n := copy(p, r.source)
+	r.source = r.source[n:]
+	return n, nr.err
+}
+
+// tests that we don't ignore errors from our underlying reader
+func TestDecoderIssue3577(t *testing.T) {
+	next := make(chan nextRead, 10)
+	wantErr := errors.New("my error")
+	next <- nextRead{5, nil}
+	next <- nextRead{10, wantErr}
+	next <- nextRead{0, wantErr}
+	d := NewDecoder(StdEncoding, &faultInjectReader{
+		source: "VHdhcyBicmlsbGlnLCBhbmQgdGhlIHNsaXRoeSB0b3Zlcw==", // twas brillig...
+		nextc:  next,
+	})
+	errc := make(chan error, 1)
+	go func() {
+		_, err := io.ReadAll(d)
+		errc <- err
+	}()
+	select {
+	case err := <-errc:
+		if err != wantErr {
+			t.Errorf("got error %v; want %v", err, wantErr)
+		}
+	case <-time.After(5 * time.Second):
+		t.Errorf("timeout; Decoder blocked without returning an error")
+	}
+}
+
+func TestDecoderIssue4779(t *testing.T) {
+	encoded := `CP/EAT8AAAEF
+AQEBAQEBAAAAAAAAAAMAAQIEBQYHCAkKCwEAAQUBAQEBAQEAAAAAAAAAAQACAwQFBgcICQoLEAAB
+BAEDAgQCBQcGCAUDDDMBAAIRAwQhEjEFQVFhEyJxgTIGFJGhsUIjJBVSwWIzNHKC0UMHJZJT8OHx
+Y3M1FqKygyZEk1RkRcKjdDYX0lXiZfKzhMPTdePzRieUpIW0lcTU5PSltcXV5fVWZnaGlqa2xtbm
+9jdHV2d3h5ent8fX5/cRAAICAQIEBAMEBQYHBwYFNQEAAhEDITESBEFRYXEiEwUygZEUobFCI8FS
+0fAzJGLhcoKSQ1MVY3M08SUGFqKygwcmNcLSRJNUoxdkRVU2dGXi8rOEw9N14/NGlKSFtJXE1OT0
+pbXF1eX1VmZ2hpamtsbW5vYnN0dXZ3eHl6e3x//aAAwDAQACEQMRAD8A9VSSSSUpJJJJSkkkJ+Tj
+1kiy1jCJJDnAcCTykpKkuQ6p/jN6FgmxlNduXawwAzaGH+V6jn/R/wCt71zdn+N/qL3kVYFNYB4N
+ji6PDVjWpKp9TSXnvTf8bFNjg3qOEa2n6VlLpj/rT/pf567DpX1i6L1hs9Py67X8mqdtg/rUWbbf
++gkp0kkkklKSSSSUpJJJJT//0PVUkkklKVLq3WMDpGI7KzrNjADtYNXvI/Mqr/Pd/q9W3vaxjnvM
+NaCXE9gNSvGPrf8AWS3qmba5jjsJhoB0DAf0NDf6sevf+/lf8Hj0JJATfWT6/dV6oXU1uOLQeKKn
+EQP+Hubtfe/+R7Mf/g7f5xcocp++Z11JMCJPgFBxOg7/AOuqDx8I/ikpkXkmSdU8mJIJA/O8EMAy
+j+mSARB/17pKVXYWHXjsj7yIex0PadzXMO1zT5KHoNA3HT8ietoGhgjsfA+CSnvvqh/jJtqsrwOv
+2b6NGNzXfTYexzJ+nU7/ALkf4P8Awv6P9KvTQQ4AgyDqCF85Pho3CTB7eHwXoH+LT65uZbX9X+o2
+bqbPb06551Y4
+`
+	encodedShort := strings.ReplaceAll(encoded, "\n", "")
+
+	dec := NewDecoder(StdEncoding, strings.NewReader(encoded))
+	res1, err := io.ReadAll(dec)
+	if err != nil {
+		t.Errorf("ReadAll failed: %v", err)
+	}
+
+	dec = NewDecoder(StdEncoding, strings.NewReader(encodedShort))
+	var res2 []byte
+	res2, err = io.ReadAll(dec)
+	if err != nil {
+		t.Errorf("ReadAll failed: %v", err)
+	}
+
+	if !bytes.Equal(res1, res2) {
+		t.Error("Decoded results not equal")
+	}
+}
+
+func TestDecoderIssue7733(t *testing.T) {
+	s, err := StdEncoding.DecodeString("YWJjZA=====")
+	want := CorruptInputError(8)
+	if !reflect.DeepEqual(want, err) {
+		t.Errorf("Error = %v; want CorruptInputError(8)", err)
+	}
+	if string(s) != "abcd" {
+		t.Errorf("DecodeString = %q; want abcd", s)
+	}
+}
+
+func TestDecoderIssue15656(t *testing.T) {
+	_, err := StdEncoding.Strict().DecodeString("WvLTlMrX9NpYDQlEIFlnDB==")
+	want := CorruptInputError(22)
+	if !reflect.DeepEqual(want, err) {
+		t.Errorf("Error = %v; want CorruptInputError(22)", err)
+	}
+	_, err = StdEncoding.Strict().DecodeString("WvLTlMrX9NpYDQlEIFlnDA==")
+	if err != nil {
+		t.Errorf("Error = %v; want nil", err)
+	}
+	_, err = StdEncoding.DecodeString("WvLTlMrX9NpYDQlEIFlnDB==")
+	if err != nil {
+		t.Errorf("Error = %v; want nil", err)
+	}
+}
+
+func BenchmarkEncodeToString(b *testing.B) {
+	data := make([]byte, 8192)
+	b.SetBytes(int64(len(data)))
+	for i := 0; i < b.N; i++ {
+		StdEncoding.EncodeToString(data)
+	}
+}
+
+func BenchmarkDecodeString(b *testing.B) {
+	sizes := []int{2, 4, 8, 64, 8192}
+	benchFunc := func(b *testing.B, benchSize int) {
+		data := StdEncoding.EncodeToString(make([]byte, benchSize))
+		b.SetBytes(int64(len(data)))
+		b.ResetTimer()
+		for i := 0; i < b.N; i++ {
+			StdEncoding.DecodeString(data)
+		}
+	}
+	for _, size := range sizes {
+		b.Run(fmt.Sprintf("%d", size), func(b *testing.B) {
+			benchFunc(b, size)
+		})
+	}
+}
+
+func TestDecoderRaw(t *testing.T) {
+	source := "AAAAAA"
+	want := []byte{0, 0, 0, 0}
+
+	// Direct.
+	dec1, err := RawURLEncoding.DecodeString(source)
+	if err != nil || !bytes.Equal(dec1, want) {
+		t.Errorf("RawURLEncoding.DecodeString(%q) = %x, %v, want %x, nil", source, dec1, err, want)
+	}
+
+	// Through reader. Used to fail.
+	r := NewDecoder(RawURLEncoding, bytes.NewReader([]byte(source)))
+	dec2, err := io.ReadAll(io.LimitReader(r, 100))
+	if err != nil || !bytes.Equal(dec2, want) {
+		t.Errorf("reading NewDecoder(RawURLEncoding, %q) = %x, %v, want %x, nil", source, dec2, err, want)
+	}
+
+	// Should work with padding.
+	r = NewDecoder(URLEncoding, bytes.NewReader([]byte(source+"==")))
+	dec3, err := io.ReadAll(r)
+	if err != nil || !bytes.Equal(dec3, want) {
+		t.Errorf("reading NewDecoder(URLEncoding, %q) = %x, %v, want %x, nil", source+"==", dec3, err, want)
+	}
+}
diff --git a/src/encoding/base64/example_test.go b/src/encoding/base64/example_test.go
new file mode 100644
index 0000000..61a3adc
--- /dev/null
+++ b/src/encoding/base64/example_test.go
@@ -0,0 +1,83 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Keep in sync with ../base32/example_test.go.
+
+package base64_test
+
+import (
+	"encoding/base64"
+	"fmt"
+	"os"
+)
+
+func Example() {
+	msg := "Hello, 世界"
+	encoded := base64.StdEncoding.EncodeToString([]byte(msg))
+	fmt.Println(encoded)
+	decoded, err := base64.StdEncoding.DecodeString(encoded)
+	if err != nil {
+		fmt.Println("decode error:", err)
+		return
+	}
+	fmt.Println(string(decoded))
+	// Output:
+	// SGVsbG8sIOS4lueVjA==
+	// Hello, 世界
+}
+
+func ExampleEncoding_EncodeToString() {
+	data := []byte("any + old & data")
+	str := base64.StdEncoding.EncodeToString(data)
+	fmt.Println(str)
+	// Output:
+	// YW55ICsgb2xkICYgZGF0YQ==
+}
+
+func ExampleEncoding_Encode() {
+	data := []byte("Hello, world!")
+	dst := make([]byte, base64.StdEncoding.EncodedLen(len(data)))
+	base64.StdEncoding.Encode(dst, data)
+	fmt.Println(string(dst))
+	// Output:
+	// SGVsbG8sIHdvcmxkIQ==
+}
+
+func ExampleEncoding_DecodeString() {
+	str := "c29tZSBkYXRhIHdpdGggACBhbmQg77u/"
+	data, err := base64.StdEncoding.DecodeString(str)
+	if err != nil {
+		fmt.Println("error:", err)
+		return
+	}
+	fmt.Printf("%q\n", data)
+	// Output:
+	// "some data with \x00 and \ufeff"
+}
+
+func ExampleEncoding_Decode() {
+	str := "SGVsbG8sIHdvcmxkIQ=="
+	dst := make([]byte, base64.StdEncoding.DecodedLen(len(str)))
+	n, err := base64.StdEncoding.Decode(dst, []byte(str))
+	if err != nil {
+		fmt.Println("decode error:", err)
+		return
+	}
+	dst = dst[:n]
+	fmt.Printf("%q\n", dst)
+	// Output:
+	// "Hello, world!"
+}
+
+func ExampleNewEncoder() {
+	input := []byte("foo\x00bar")
+	encoder := base64.NewEncoder(base64.StdEncoding, os.Stdout)
+	encoder.Write(input)
+	// Must close the encoder when finished to flush any partial blocks.
+	// If you comment out the following line, the last partial block "r"
+	// won't be encoded.
+	encoder.Close()
+	// Output:
+	// Zm9vAGJhcg==
+}
diff --git a/src/encoding/binary/binary.go b/src/encoding/binary/binary.go
new file mode 100644
index 0000000..ee93346
--- /dev/null
+++ b/src/encoding/binary/binary.go
@@ -0,0 +1,737 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package binary implements simple translation between numbers and byte
+// sequences and encoding and decoding of varints.
+//
+// Numbers are translated by reading and writing fixed-size values.
+// A fixed-size value is either a fixed-size arithmetic
+// type (bool, int8, uint8, int16, float32, complex64, ...)
+// or an array or struct containing only fixed-size values.
+//
+// The varint functions encode and decode single integer values using
+// a variable-length encoding; smaller values require fewer bytes.
+// For a specification, see
+// https://developers.google.com/protocol-buffers/docs/encoding.
+//
+// This package favors simplicity over efficiency. Clients that require
+// high-performance serialization, especially for large data structures,
+// should look at more advanced solutions such as the encoding/gob
+// package or protocol buffers.
+package binary
+
+import (
+	"errors"
+	"io"
+	"math"
+	"reflect"
+	"sync"
+)
+
+// A ByteOrder specifies how to convert byte sequences into
+// 16-, 32-, or 64-bit unsigned integers.
+type ByteOrder interface {
+	Uint16([]byte) uint16
+	Uint32([]byte) uint32
+	Uint64([]byte) uint64
+	PutUint16([]byte, uint16)
+	PutUint32([]byte, uint32)
+	PutUint64([]byte, uint64)
+	String() string
+}
+
+// LittleEndian is the little-endian implementation of ByteOrder.
+var LittleEndian littleEndian
+
+// BigEndian is the big-endian implementation of ByteOrder.
+var BigEndian bigEndian
+
+type littleEndian struct{}
+
+func (littleEndian) Uint16(b []byte) uint16 {
+	_ = b[1] // bounds check hint to compiler; see golang.org/issue/14808
+	return uint16(b[0]) | uint16(b[1])<<8
+}
+
+func (littleEndian) PutUint16(b []byte, v uint16) {
+	_ = b[1] // early bounds check to guarantee safety of writes below
+	b[0] = byte(v)
+	b[1] = byte(v >> 8)
+}
+
+func (littleEndian) Uint32(b []byte) uint32 {
+	_ = b[3] // bounds check hint to compiler; see golang.org/issue/14808
+	return uint32(b[0]) | uint32(b[1])<<8 | uint32(b[2])<<16 | uint32(b[3])<<24
+}
+
+func (littleEndian) PutUint32(b []byte, v uint32) {
+	_ = b[3] // early bounds check to guarantee safety of writes below
+	b[0] = byte(v)
+	b[1] = byte(v >> 8)
+	b[2] = byte(v >> 16)
+	b[3] = byte(v >> 24)
+}
+
+func (littleEndian) Uint64(b []byte) uint64 {
+	_ = b[7] // bounds check hint to compiler; see golang.org/issue/14808
+	return uint64(b[0]) | uint64(b[1])<<8 | uint64(b[2])<<16 | uint64(b[3])<<24 |
+		uint64(b[4])<<32 | uint64(b[5])<<40 | uint64(b[6])<<48 | uint64(b[7])<<56
+}
+
+func (littleEndian) PutUint64(b []byte, v uint64) {
+	_ = b[7] // early bounds check to guarantee safety of writes below
+	b[0] = byte(v)
+	b[1] = byte(v >> 8)
+	b[2] = byte(v >> 16)
+	b[3] = byte(v >> 24)
+	b[4] = byte(v >> 32)
+	b[5] = byte(v >> 40)
+	b[6] = byte(v >> 48)
+	b[7] = byte(v >> 56)
+}
+
+func (littleEndian) String() string { return "LittleEndian" }
+
+func (littleEndian) GoString() string { return "binary.LittleEndian" }
+
+type bigEndian struct{}
+
+func (bigEndian) Uint16(b []byte) uint16 {
+	_ = b[1] // bounds check hint to compiler; see golang.org/issue/14808
+	return uint16(b[1]) | uint16(b[0])<<8
+}
+
+func (bigEndian) PutUint16(b []byte, v uint16) {
+	_ = b[1] // early bounds check to guarantee safety of writes below
+	b[0] = byte(v >> 8)
+	b[1] = byte(v)
+}
+
+func (bigEndian) Uint32(b []byte) uint32 {
+	_ = b[3] // bounds check hint to compiler; see golang.org/issue/14808
+	return uint32(b[3]) | uint32(b[2])<<8 | uint32(b[1])<<16 | uint32(b[0])<<24
+}
+
+func (bigEndian) PutUint32(b []byte, v uint32) {
+	_ = b[3] // early bounds check to guarantee safety of writes below
+	b[0] = byte(v >> 24)
+	b[1] = byte(v >> 16)
+	b[2] = byte(v >> 8)
+	b[3] = byte(v)
+}
+
+func (bigEndian) Uint64(b []byte) uint64 {
+	_ = b[7] // bounds check hint to compiler; see golang.org/issue/14808
+	return uint64(b[7]) | uint64(b[6])<<8 | uint64(b[5])<<16 | uint64(b[4])<<24 |
+		uint64(b[3])<<32 | uint64(b[2])<<40 | uint64(b[1])<<48 | uint64(b[0])<<56
+}
+
+func (bigEndian) PutUint64(b []byte, v uint64) {
+	_ = b[7] // early bounds check to guarantee safety of writes below
+	b[0] = byte(v >> 56)
+	b[1] = byte(v >> 48)
+	b[2] = byte(v >> 40)
+	b[3] = byte(v >> 32)
+	b[4] = byte(v >> 24)
+	b[5] = byte(v >> 16)
+	b[6] = byte(v >> 8)
+	b[7] = byte(v)
+}
+
+func (bigEndian) String() string { return "BigEndian" }
+
+func (bigEndian) GoString() string { return "binary.BigEndian" }
+
+// Read reads structured binary data from r into data.
+// Data must be a pointer to a fixed-size value or a slice
+// of fixed-size values.
+// Bytes read from r are decoded using the specified byte order
+// and written to successive fields of the data.
+// When decoding boolean values, a zero byte is decoded as false, and
+// any other non-zero byte is decoded as true.
+// When reading into structs, the field data for fields with
+// blank (_) field names is skipped; i.e., blank field names
+// may be used for padding.
+// When reading into a struct, all non-blank fields must be exported
+// or Read may panic.
+//
+// The error is EOF only if no bytes were read.
+// If an EOF happens after reading some but not all the bytes,
+// Read returns ErrUnexpectedEOF.
+func Read(r io.Reader, order ByteOrder, data any) error {
+	// Fast path for basic types and slices.
+	if n := intDataSize(data); n != 0 {
+		bs := make([]byte, n)
+		if _, err := io.ReadFull(r, bs); err != nil {
+			return err
+		}
+		switch data := data.(type) {
+		case *bool:
+			*data = bs[0] != 0
+		case *int8:
+			*data = int8(bs[0])
+		case *uint8:
+			*data = bs[0]
+		case *int16:
+			*data = int16(order.Uint16(bs))
+		case *uint16:
+			*data = order.Uint16(bs)
+		case *int32:
+			*data = int32(order.Uint32(bs))
+		case *uint32:
+			*data = order.Uint32(bs)
+		case *int64:
+			*data = int64(order.Uint64(bs))
+		case *uint64:
+			*data = order.Uint64(bs)
+		case *float32:
+			*data = math.Float32frombits(order.Uint32(bs))
+		case *float64:
+			*data = math.Float64frombits(order.Uint64(bs))
+		case []bool:
+			for i, x := range bs { // Easier to loop over the input for 8-bit values.
+				data[i] = x != 0
+			}
+		case []int8:
+			for i, x := range bs {
+				data[i] = int8(x)
+			}
+		case []uint8:
+			copy(data, bs)
+		case []int16:
+			for i := range data {
+				data[i] = int16(order.Uint16(bs[2*i:]))
+			}
+		case []uint16:
+			for i := range data {
+				data[i] = order.Uint16(bs[2*i:])
+			}
+		case []int32:
+			for i := range data {
+				data[i] = int32(order.Uint32(bs[4*i:]))
+			}
+		case []uint32:
+			for i := range data {
+				data[i] = order.Uint32(bs[4*i:])
+			}
+		case []int64:
+			for i := range data {
+				data[i] = int64(order.Uint64(bs[8*i:]))
+			}
+		case []uint64:
+			for i := range data {
+				data[i] = order.Uint64(bs[8*i:])
+			}
+		case []float32:
+			for i := range data {
+				data[i] = math.Float32frombits(order.Uint32(bs[4*i:]))
+			}
+		case []float64:
+			for i := range data {
+				data[i] = math.Float64frombits(order.Uint64(bs[8*i:]))
+			}
+		default:
+			n = 0 // fast path doesn't apply
+		}
+		if n != 0 {
+			return nil
+		}
+	}
+
+	// Fallback to reflect-based decoding.
+	v := reflect.ValueOf(data)
+	size := -1
+	switch v.Kind() {
+	case reflect.Pointer:
+		v = v.Elem()
+		size = dataSize(v)
+	case reflect.Slice:
+		size = dataSize(v)
+	}
+	if size < 0 {
+		return errors.New("binary.Read: invalid type " + reflect.TypeOf(data).String())
+	}
+	d := &decoder{order: order, buf: make([]byte, size)}
+	if _, err := io.ReadFull(r, d.buf); err != nil {
+		return err
+	}
+	d.value(v)
+	return nil
+}
+
+// Write writes the binary representation of data into w.
+// Data must be a fixed-size value or a slice of fixed-size
+// values, or a pointer to such data.
+// Boolean values encode as one byte: 1 for true, and 0 for false.
+// Bytes written to w are encoded using the specified byte order
+// and read from successive fields of the data.
+// When writing structs, zero values are written for fields
+// with blank (_) field names.
+func Write(w io.Writer, order ByteOrder, data any) error {
+	// Fast path for basic types and slices.
+	if n := intDataSize(data); n != 0 {
+		bs := make([]byte, n)
+		switch v := data.(type) {
+		case *bool:
+			if *v {
+				bs[0] = 1
+			} else {
+				bs[0] = 0
+			}
+		case bool:
+			if v {
+				bs[0] = 1
+			} else {
+				bs[0] = 0
+			}
+		case []bool:
+			for i, x := range v {
+				if x {
+					bs[i] = 1
+				} else {
+					bs[i] = 0
+				}
+			}
+		case *int8:
+			bs[0] = byte(*v)
+		case int8:
+			bs[0] = byte(v)
+		case []int8:
+			for i, x := range v {
+				bs[i] = byte(x)
+			}
+		case *uint8:
+			bs[0] = *v
+		case uint8:
+			bs[0] = v
+		case []uint8:
+			bs = v
+		case *int16:
+			order.PutUint16(bs, uint16(*v))
+		case int16:
+			order.PutUint16(bs, uint16(v))
+		case []int16:
+			for i, x := range v {
+				order.PutUint16(bs[2*i:], uint16(x))
+			}
+		case *uint16:
+			order.PutUint16(bs, *v)
+		case uint16:
+			order.PutUint16(bs, v)
+		case []uint16:
+			for i, x := range v {
+				order.PutUint16(bs[2*i:], x)
+			}
+		case *int32:
+			order.PutUint32(bs, uint32(*v))
+		case int32:
+			order.PutUint32(bs, uint32(v))
+		case []int32:
+			for i, x := range v {
+				order.PutUint32(bs[4*i:], uint32(x))
+			}
+		case *uint32:
+			order.PutUint32(bs, *v)
+		case uint32:
+			order.PutUint32(bs, v)
+		case []uint32:
+			for i, x := range v {
+				order.PutUint32(bs[4*i:], x)
+			}
+		case *int64:
+			order.PutUint64(bs, uint64(*v))
+		case int64:
+			order.PutUint64(bs, uint64(v))
+		case []int64:
+			for i, x := range v {
+				order.PutUint64(bs[8*i:], uint64(x))
+			}
+		case *uint64:
+			order.PutUint64(bs, *v)
+		case uint64:
+			order.PutUint64(bs, v)
+		case []uint64:
+			for i, x := range v {
+				order.PutUint64(bs[8*i:], x)
+			}
+		case *float32:
+			order.PutUint32(bs, math.Float32bits(*v))
+		case float32:
+			order.PutUint32(bs, math.Float32bits(v))
+		case []float32:
+			for i, x := range v {
+				order.PutUint32(bs[4*i:], math.Float32bits(x))
+			}
+		case *float64:
+			order.PutUint64(bs, math.Float64bits(*v))
+		case float64:
+			order.PutUint64(bs, math.Float64bits(v))
+		case []float64:
+			for i, x := range v {
+				order.PutUint64(bs[8*i:], math.Float64bits(x))
+			}
+		}
+		_, err := w.Write(bs)
+		return err
+	}
+
+	// Fallback to reflect-based encoding.
+	v := reflect.Indirect(reflect.ValueOf(data))
+	size := dataSize(v)
+	if size < 0 {
+		return errors.New("binary.Write: invalid type " + reflect.TypeOf(data).String())
+	}
+	buf := make([]byte, size)
+	e := &encoder{order: order, buf: buf}
+	e.value(v)
+	_, err := w.Write(buf)
+	return err
+}
+
+// Size returns how many bytes Write would generate to encode the value v, which
+// must be a fixed-size value or a slice of fixed-size values, or a pointer to such data.
+// If v is neither of these, Size returns -1.
+func Size(v any) int {
+	return dataSize(reflect.Indirect(reflect.ValueOf(v)))
+}
+
+var structSize sync.Map // map[reflect.Type]int
+
+// dataSize returns the number of bytes the actual data represented by v occupies in memory.
+// For compound structures, it sums the sizes of the elements. Thus, for instance, for a slice
+// it returns the length of the slice times the element size and does not count the memory
+// occupied by the header. If the type of v is not acceptable, dataSize returns -1.
+func dataSize(v reflect.Value) int {
+	switch v.Kind() {
+	case reflect.Slice:
+		if s := sizeof(v.Type().Elem()); s >= 0 {
+			return s * v.Len()
+		}
+		return -1
+
+	case reflect.Struct:
+		t := v.Type()
+		if size, ok := structSize.Load(t); ok {
+			return size.(int)
+		}
+		size := sizeof(t)
+		structSize.Store(t, size)
+		return size
+
+	default:
+		return sizeof(v.Type())
+	}
+}
+
+// sizeof returns the size >= 0 of variables for the given type or -1 if the type is not acceptable.
+func sizeof(t reflect.Type) int {
+	switch t.Kind() {
+	case reflect.Array:
+		if s := sizeof(t.Elem()); s >= 0 {
+			return s * t.Len()
+		}
+
+	case reflect.Struct:
+		sum := 0
+		for i, n := 0, t.NumField(); i < n; i++ {
+			s := sizeof(t.Field(i).Type)
+			if s < 0 {
+				return -1
+			}
+			sum += s
+		}
+		return sum
+
+	case reflect.Bool,
+		reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64,
+		reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
+		reflect.Float32, reflect.Float64, reflect.Complex64, reflect.Complex128:
+		return int(t.Size())
+	}
+
+	return -1
+}
+
+type coder struct {
+	order  ByteOrder
+	buf    []byte
+	offset int
+}
+
+type decoder coder
+type encoder coder
+
+func (d *decoder) bool() bool {
+	x := d.buf[d.offset]
+	d.offset++
+	return x != 0
+}
+
+func (e *encoder) bool(x bool) {
+	if x {
+		e.buf[e.offset] = 1
+	} else {
+		e.buf[e.offset] = 0
+	}
+	e.offset++
+}
+
+func (d *decoder) uint8() uint8 {
+	x := d.buf[d.offset]
+	d.offset++
+	return x
+}
+
+func (e *encoder) uint8(x uint8) {
+	e.buf[e.offset] = x
+	e.offset++
+}
+
+func (d *decoder) uint16() uint16 {
+	x := d.order.Uint16(d.buf[d.offset : d.offset+2])
+	d.offset += 2
+	return x
+}
+
+func (e *encoder) uint16(x uint16) {
+	e.order.PutUint16(e.buf[e.offset:e.offset+2], x)
+	e.offset += 2
+}
+
+func (d *decoder) uint32() uint32 {
+	x := d.order.Uint32(d.buf[d.offset : d.offset+4])
+	d.offset += 4
+	return x
+}
+
+func (e *encoder) uint32(x uint32) {
+	e.order.PutUint32(e.buf[e.offset:e.offset+4], x)
+	e.offset += 4
+}
+
+func (d *decoder) uint64() uint64 {
+	x := d.order.Uint64(d.buf[d.offset : d.offset+8])
+	d.offset += 8
+	return x
+}
+
+func (e *encoder) uint64(x uint64) {
+	e.order.PutUint64(e.buf[e.offset:e.offset+8], x)
+	e.offset += 8
+}
+
+func (d *decoder) int8() int8 { return int8(d.uint8()) }
+
+func (e *encoder) int8(x int8) { e.uint8(uint8(x)) }
+
+func (d *decoder) int16() int16 { return int16(d.uint16()) }
+
+func (e *encoder) int16(x int16) { e.uint16(uint16(x)) }
+
+func (d *decoder) int32() int32 { return int32(d.uint32()) }
+
+func (e *encoder) int32(x int32) { e.uint32(uint32(x)) }
+
+func (d *decoder) int64() int64 { return int64(d.uint64()) }
+
+func (e *encoder) int64(x int64) { e.uint64(uint64(x)) }
+
+func (d *decoder) value(v reflect.Value) {
+	switch v.Kind() {
+	case reflect.Array:
+		l := v.Len()
+		for i := 0; i < l; i++ {
+			d.value(v.Index(i))
+		}
+
+	case reflect.Struct:
+		t := v.Type()
+		l := v.NumField()
+		for i := 0; i < l; i++ {
+			// Note: Calling v.CanSet() below is an optimization.
+			// It would be sufficient to check the field name,
+			// but creating the StructField info for each field is
+			// costly (run "go test -bench=ReadStruct" and compare
+			// results when making changes to this code).
+			if v := v.Field(i); v.CanSet() || t.Field(i).Name != "_" {
+				d.value(v)
+			} else {
+				d.skip(v)
+			}
+		}
+
+	case reflect.Slice:
+		l := v.Len()
+		for i := 0; i < l; i++ {
+			d.value(v.Index(i))
+		}
+
+	case reflect.Bool:
+		v.SetBool(d.bool())
+
+	case reflect.Int8:
+		v.SetInt(int64(d.int8()))
+	case reflect.Int16:
+		v.SetInt(int64(d.int16()))
+	case reflect.Int32:
+		v.SetInt(int64(d.int32()))
+	case reflect.Int64:
+		v.SetInt(d.int64())
+
+	case reflect.Uint8:
+		v.SetUint(uint64(d.uint8()))
+	case reflect.Uint16:
+		v.SetUint(uint64(d.uint16()))
+	case reflect.Uint32:
+		v.SetUint(uint64(d.uint32()))
+	case reflect.Uint64:
+		v.SetUint(d.uint64())
+
+	case reflect.Float32:
+		v.SetFloat(float64(math.Float32frombits(d.uint32())))
+	case reflect.Float64:
+		v.SetFloat(math.Float64frombits(d.uint64()))
+
+	case reflect.Complex64:
+		v.SetComplex(complex(
+			float64(math.Float32frombits(d.uint32())),
+			float64(math.Float32frombits(d.uint32())),
+		))
+	case reflect.Complex128:
+		v.SetComplex(complex(
+			math.Float64frombits(d.uint64()),
+			math.Float64frombits(d.uint64()),
+		))
+	}
+}
+
+func (e *encoder) value(v reflect.Value) {
+	switch v.Kind() {
+	case reflect.Array:
+		l := v.Len()
+		for i := 0; i < l; i++ {
+			e.value(v.Index(i))
+		}
+
+	case reflect.Struct:
+		t := v.Type()
+		l := v.NumField()
+		for i := 0; i < l; i++ {
+			// see comment for corresponding code in decoder.value()
+			if v := v.Field(i); v.CanSet() || t.Field(i).Name != "_" {
+				e.value(v)
+			} else {
+				e.skip(v)
+			}
+		}
+
+	case reflect.Slice:
+		l := v.Len()
+		for i := 0; i < l; i++ {
+			e.value(v.Index(i))
+		}
+
+	case reflect.Bool:
+		e.bool(v.Bool())
+
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		switch v.Type().Kind() {
+		case reflect.Int8:
+			e.int8(int8(v.Int()))
+		case reflect.Int16:
+			e.int16(int16(v.Int()))
+		case reflect.Int32:
+			e.int32(int32(v.Int()))
+		case reflect.Int64:
+			e.int64(v.Int())
+		}
+
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		switch v.Type().Kind() {
+		case reflect.Uint8:
+			e.uint8(uint8(v.Uint()))
+		case reflect.Uint16:
+			e.uint16(uint16(v.Uint()))
+		case reflect.Uint32:
+			e.uint32(uint32(v.Uint()))
+		case reflect.Uint64:
+			e.uint64(v.Uint())
+		}
+
+	case reflect.Float32, reflect.Float64:
+		switch v.Type().Kind() {
+		case reflect.Float32:
+			e.uint32(math.Float32bits(float32(v.Float())))
+		case reflect.Float64:
+			e.uint64(math.Float64bits(v.Float()))
+		}
+
+	case reflect.Complex64, reflect.Complex128:
+		switch v.Type().Kind() {
+		case reflect.Complex64:
+			x := v.Complex()
+			e.uint32(math.Float32bits(float32(real(x))))
+			e.uint32(math.Float32bits(float32(imag(x))))
+		case reflect.Complex128:
+			x := v.Complex()
+			e.uint64(math.Float64bits(real(x)))
+			e.uint64(math.Float64bits(imag(x)))
+		}
+	}
+}
+
+func (d *decoder) skip(v reflect.Value) {
+	d.offset += dataSize(v)
+}
+
+func (e *encoder) skip(v reflect.Value) {
+	n := dataSize(v)
+	zero := e.buf[e.offset : e.offset+n]
+	for i := range zero {
+		zero[i] = 0
+	}
+	e.offset += n
+}
+
+// intDataSize returns the size of the data required to represent the data when encoded.
+// It returns zero if the type cannot be implemented by the fast path in Read or Write.
+func intDataSize(data any) int {
+	switch data := data.(type) {
+	case bool, int8, uint8, *bool, *int8, *uint8:
+		return 1
+	case []bool:
+		return len(data)
+	case []int8:
+		return len(data)
+	case []uint8:
+		return len(data)
+	case int16, uint16, *int16, *uint16:
+		return 2
+	case []int16:
+		return 2 * len(data)
+	case []uint16:
+		return 2 * len(data)
+	case int32, uint32, *int32, *uint32:
+		return 4
+	case []int32:
+		return 4 * len(data)
+	case []uint32:
+		return 4 * len(data)
+	case int64, uint64, *int64, *uint64:
+		return 8
+	case []int64:
+		return 8 * len(data)
+	case []uint64:
+		return 8 * len(data)
+	case float32, *float32:
+		return 4
+	case float64, *float64:
+		return 8
+	case []float32:
+		return 4 * len(data)
+	case []float64:
+		return 8 * len(data)
+	}
+	return 0
+}
diff --git a/src/encoding/binary/binary_test.go b/src/encoding/binary/binary_test.go
new file mode 100644
index 0000000..9e1b5f1
--- /dev/null
+++ b/src/encoding/binary/binary_test.go
@@ -0,0 +1,731 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package binary
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"math"
+	"reflect"
+	"strings"
+	"sync"
+	"testing"
+)
+
+type Struct struct {
+	Int8       int8
+	Int16      int16
+	Int32      int32
+	Int64      int64
+	Uint8      uint8
+	Uint16     uint16
+	Uint32     uint32
+	Uint64     uint64
+	Float32    float32
+	Float64    float64
+	Complex64  complex64
+	Complex128 complex128
+	Array      [4]uint8
+	Bool       bool
+	BoolArray  [4]bool
+}
+
+type T struct {
+	Int     int
+	Uint    uint
+	Uintptr uintptr
+	Array   [4]int
+}
+
+var s = Struct{
+	0x01,
+	0x0203,
+	0x04050607,
+	0x08090a0b0c0d0e0f,
+	0x10,
+	0x1112,
+	0x13141516,
+	0x1718191a1b1c1d1e,
+
+	math.Float32frombits(0x1f202122),
+	math.Float64frombits(0x232425262728292a),
+	complex(
+		math.Float32frombits(0x2b2c2d2e),
+		math.Float32frombits(0x2f303132),
+	),
+	complex(
+		math.Float64frombits(0x333435363738393a),
+		math.Float64frombits(0x3b3c3d3e3f404142),
+	),
+
+	[4]uint8{0x43, 0x44, 0x45, 0x46},
+
+	true,
+	[4]bool{true, false, true, false},
+}
+
+var big = []byte{
+	1,
+	2, 3,
+	4, 5, 6, 7,
+	8, 9, 10, 11, 12, 13, 14, 15,
+	16,
+	17, 18,
+	19, 20, 21, 22,
+	23, 24, 25, 26, 27, 28, 29, 30,
+
+	31, 32, 33, 34,
+	35, 36, 37, 38, 39, 40, 41, 42,
+	43, 44, 45, 46, 47, 48, 49, 50,
+	51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66,
+
+	67, 68, 69, 70,
+
+	1,
+	1, 0, 1, 0,
+}
+
+var little = []byte{
+	1,
+	3, 2,
+	7, 6, 5, 4,
+	15, 14, 13, 12, 11, 10, 9, 8,
+	16,
+	18, 17,
+	22, 21, 20, 19,
+	30, 29, 28, 27, 26, 25, 24, 23,
+
+	34, 33, 32, 31,
+	42, 41, 40, 39, 38, 37, 36, 35,
+	46, 45, 44, 43, 50, 49, 48, 47,
+	58, 57, 56, 55, 54, 53, 52, 51, 66, 65, 64, 63, 62, 61, 60, 59,
+
+	67, 68, 69, 70,
+
+	1,
+	1, 0, 1, 0,
+}
+
+var src = []byte{1, 2, 3, 4, 5, 6, 7, 8}
+var res = []int32{0x01020304, 0x05060708}
+var putbuf = []byte{0, 0, 0, 0, 0, 0, 0, 0}
+
+func checkResult(t *testing.T, dir string, order ByteOrder, err error, have, want any) {
+	if err != nil {
+		t.Errorf("%v %v: %v", dir, order, err)
+		return
+	}
+	if !reflect.DeepEqual(have, want) {
+		t.Errorf("%v %v:\n\thave %+v\n\twant %+v", dir, order, have, want)
+	}
+}
+
+func testRead(t *testing.T, order ByteOrder, b []byte, s1 any) {
+	var s2 Struct
+	err := Read(bytes.NewReader(b), order, &s2)
+	checkResult(t, "Read", order, err, s2, s1)
+}
+
+func testWrite(t *testing.T, order ByteOrder, b []byte, s1 any) {
+	buf := new(bytes.Buffer)
+	err := Write(buf, order, s1)
+	checkResult(t, "Write", order, err, buf.Bytes(), b)
+}
+
+func TestLittleEndianRead(t *testing.T)     { testRead(t, LittleEndian, little, s) }
+func TestLittleEndianWrite(t *testing.T)    { testWrite(t, LittleEndian, little, s) }
+func TestLittleEndianPtrWrite(t *testing.T) { testWrite(t, LittleEndian, little, &s) }
+
+func TestBigEndianRead(t *testing.T)     { testRead(t, BigEndian, big, s) }
+func TestBigEndianWrite(t *testing.T)    { testWrite(t, BigEndian, big, s) }
+func TestBigEndianPtrWrite(t *testing.T) { testWrite(t, BigEndian, big, &s) }
+
+func TestReadSlice(t *testing.T) {
+	slice := make([]int32, 2)
+	err := Read(bytes.NewReader(src), BigEndian, slice)
+	checkResult(t, "ReadSlice", BigEndian, err, slice, res)
+}
+
+func TestWriteSlice(t *testing.T) {
+	buf := new(bytes.Buffer)
+	err := Write(buf, BigEndian, res)
+	checkResult(t, "WriteSlice", BigEndian, err, buf.Bytes(), src)
+}
+
+func TestReadBool(t *testing.T) {
+	var res bool
+	var err error
+	err = Read(bytes.NewReader([]byte{0}), BigEndian, &res)
+	checkResult(t, "ReadBool", BigEndian, err, res, false)
+	res = false
+	err = Read(bytes.NewReader([]byte{1}), BigEndian, &res)
+	checkResult(t, "ReadBool", BigEndian, err, res, true)
+	res = false
+	err = Read(bytes.NewReader([]byte{2}), BigEndian, &res)
+	checkResult(t, "ReadBool", BigEndian, err, res, true)
+}
+
+func TestReadBoolSlice(t *testing.T) {
+	slice := make([]bool, 4)
+	err := Read(bytes.NewReader([]byte{0, 1, 2, 255}), BigEndian, slice)
+	checkResult(t, "ReadBoolSlice", BigEndian, err, slice, []bool{false, true, true, true})
+}
+
+// Addresses of arrays are easier to manipulate with reflection than are slices.
+var intArrays = []any{
+	&[100]int8{},
+	&[100]int16{},
+	&[100]int32{},
+	&[100]int64{},
+	&[100]uint8{},
+	&[100]uint16{},
+	&[100]uint32{},
+	&[100]uint64{},
+}
+
+func TestSliceRoundTrip(t *testing.T) {
+	buf := new(bytes.Buffer)
+	for _, array := range intArrays {
+		src := reflect.ValueOf(array).Elem()
+		unsigned := false
+		switch src.Index(0).Kind() {
+		case reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
+			unsigned = true
+		}
+		for i := 0; i < src.Len(); i++ {
+			if unsigned {
+				src.Index(i).SetUint(uint64(i * 0x07654321))
+			} else {
+				src.Index(i).SetInt(int64(i * 0x07654321))
+			}
+		}
+		buf.Reset()
+		srcSlice := src.Slice(0, src.Len())
+		err := Write(buf, BigEndian, srcSlice.Interface())
+		if err != nil {
+			t.Fatal(err)
+		}
+		dst := reflect.New(src.Type()).Elem()
+		dstSlice := dst.Slice(0, dst.Len())
+		err = Read(buf, BigEndian, dstSlice.Interface())
+		if err != nil {
+			t.Fatal(err)
+		}
+		if !reflect.DeepEqual(src.Interface(), dst.Interface()) {
+			t.Fatal(src)
+		}
+	}
+}
+
+func TestWriteT(t *testing.T) {
+	buf := new(bytes.Buffer)
+	ts := T{}
+	if err := Write(buf, BigEndian, ts); err == nil {
+		t.Errorf("WriteT: have err == nil, want non-nil")
+	}
+
+	tv := reflect.Indirect(reflect.ValueOf(ts))
+	for i, n := 0, tv.NumField(); i < n; i++ {
+		typ := tv.Field(i).Type().String()
+		if typ == "[4]int" {
+			typ = "int" // the problem is int, not the [4]
+		}
+		if err := Write(buf, BigEndian, tv.Field(i).Interface()); err == nil {
+			t.Errorf("WriteT.%v: have err == nil, want non-nil", tv.Field(i).Type())
+		} else if !strings.Contains(err.Error(), typ) {
+			t.Errorf("WriteT: have err == %q, want it to mention %s", err, typ)
+		}
+	}
+}
+
+type BlankFields struct {
+	A uint32
+	_ int32
+	B float64
+	_ [4]int16
+	C byte
+	_ [7]byte
+	_ struct {
+		f [8]float32
+	}
+}
+
+type BlankFieldsProbe struct {
+	A  uint32
+	P0 int32
+	B  float64
+	P1 [4]int16
+	C  byte
+	P2 [7]byte
+	P3 struct {
+		F [8]float32
+	}
+}
+
+func TestBlankFields(t *testing.T) {
+	buf := new(bytes.Buffer)
+	b1 := BlankFields{A: 1234567890, B: 2.718281828, C: 42}
+	if err := Write(buf, LittleEndian, &b1); err != nil {
+		t.Error(err)
+	}
+
+	// zero values must have been written for blank fields
+	var p BlankFieldsProbe
+	if err := Read(buf, LittleEndian, &p); err != nil {
+		t.Error(err)
+	}
+
+	// quick test: only check first value of slices
+	if p.P0 != 0 || p.P1[0] != 0 || p.P2[0] != 0 || p.P3.F[0] != 0 {
+		t.Errorf("non-zero values for originally blank fields: %#v", p)
+	}
+
+	// write p and see if we can probe only some fields
+	if err := Write(buf, LittleEndian, &p); err != nil {
+		t.Error(err)
+	}
+
+	// read should ignore blank fields in b2
+	var b2 BlankFields
+	if err := Read(buf, LittleEndian, &b2); err != nil {
+		t.Error(err)
+	}
+	if b1.A != b2.A || b1.B != b2.B || b1.C != b2.C {
+		t.Errorf("%#v != %#v", b1, b2)
+	}
+}
+
+func TestSizeStructCache(t *testing.T) {
+	// Reset the cache, otherwise multiple test runs fail.
+	structSize = sync.Map{}
+
+	count := func() int {
+		var i int
+		structSize.Range(func(_, _ any) bool {
+			i++
+			return true
+		})
+		return i
+	}
+
+	var total int
+	added := func() int {
+		delta := count() - total
+		total += delta
+		return delta
+	}
+
+	type foo struct {
+		A uint32
+	}
+
+	type bar struct {
+		A Struct
+		B foo
+		C Struct
+	}
+
+	testcases := []struct {
+		val  any
+		want int
+	}{
+		{new(foo), 1},
+		{new(bar), 1},
+		{new(bar), 0},
+		{new(struct{ A Struct }), 1},
+		{new(struct{ A Struct }), 0},
+	}
+
+	for _, tc := range testcases {
+		if Size(tc.val) == -1 {
+			t.Fatalf("Can't get the size of %T", tc.val)
+		}
+
+		if n := added(); n != tc.want {
+			t.Errorf("Sizing %T added %d entries to the cache, want %d", tc.val, n, tc.want)
+		}
+	}
+}
+
+// An attempt to read into a struct with an unexported field will
+// panic. This is probably not the best choice, but at this point
+// anything else would be an API change.
+
+type Unexported struct {
+	a int32
+}
+
+func TestUnexportedRead(t *testing.T) {
+	var buf bytes.Buffer
+	u1 := Unexported{a: 1}
+	if err := Write(&buf, LittleEndian, &u1); err != nil {
+		t.Fatal(err)
+	}
+
+	defer func() {
+		if recover() == nil {
+			t.Fatal("did not panic")
+		}
+	}()
+	var u2 Unexported
+	Read(&buf, LittleEndian, &u2)
+}
+
+func TestReadErrorMsg(t *testing.T) {
+	var buf bytes.Buffer
+	read := func(data any) {
+		err := Read(&buf, LittleEndian, data)
+		want := "binary.Read: invalid type " + reflect.TypeOf(data).String()
+		if err == nil {
+			t.Errorf("%T: got no error; want %q", data, want)
+			return
+		}
+		if got := err.Error(); got != want {
+			t.Errorf("%T: got %q; want %q", data, got, want)
+		}
+	}
+	read(0)
+	s := new(struct{})
+	read(&s)
+	p := &s
+	read(&p)
+}
+
+func TestReadTruncated(t *testing.T) {
+	const data = "0123456789abcdef"
+
+	var b1 = make([]int32, 4)
+	var b2 struct {
+		A, B, C, D byte
+		E          int32
+		F          float64
+	}
+
+	for i := 0; i <= len(data); i++ {
+		var errWant error
+		switch i {
+		case 0:
+			errWant = io.EOF
+		case len(data):
+			errWant = nil
+		default:
+			errWant = io.ErrUnexpectedEOF
+		}
+
+		if err := Read(strings.NewReader(data[:i]), LittleEndian, &b1); err != errWant {
+			t.Errorf("Read(%d) with slice: got %v, want %v", i, err, errWant)
+		}
+		if err := Read(strings.NewReader(data[:i]), LittleEndian, &b2); err != errWant {
+			t.Errorf("Read(%d) with struct: got %v, want %v", i, err, errWant)
+		}
+	}
+}
+
+func testUint64SmallSliceLengthPanics() (panicked bool) {
+	defer func() {
+		panicked = recover() != nil
+	}()
+	b := [8]byte{1, 2, 3, 4, 5, 6, 7, 8}
+	LittleEndian.Uint64(b[:4])
+	return false
+}
+
+func testPutUint64SmallSliceLengthPanics() (panicked bool) {
+	defer func() {
+		panicked = recover() != nil
+	}()
+	b := [8]byte{}
+	LittleEndian.PutUint64(b[:4], 0x0102030405060708)
+	return false
+}
+
+func TestEarlyBoundsChecks(t *testing.T) {
+	if testUint64SmallSliceLengthPanics() != true {
+		t.Errorf("binary.LittleEndian.Uint64 expected to panic for small slices, but didn't")
+	}
+	if testPutUint64SmallSliceLengthPanics() != true {
+		t.Errorf("binary.LittleEndian.PutUint64 expected to panic for small slices, but didn't")
+	}
+}
+
+func TestReadInvalidDestination(t *testing.T) {
+	testReadInvalidDestination(t, BigEndian)
+	testReadInvalidDestination(t, LittleEndian)
+}
+
+func testReadInvalidDestination(t *testing.T, order ByteOrder) {
+	destinations := []any{
+		int8(0),
+		int16(0),
+		int32(0),
+		int64(0),
+
+		uint8(0),
+		uint16(0),
+		uint32(0),
+		uint64(0),
+
+		bool(false),
+	}
+
+	for _, dst := range destinations {
+		err := Read(bytes.NewReader([]byte{1, 2, 3, 4, 5, 6, 7, 8}), order, dst)
+		want := fmt.Sprintf("binary.Read: invalid type %T", dst)
+		if err == nil || err.Error() != want {
+			t.Fatalf("for type %T: got %q; want %q", dst, err, want)
+		}
+	}
+}
+
+type byteSliceReader struct {
+	remain []byte
+}
+
+func (br *byteSliceReader) Read(p []byte) (int, error) {
+	n := copy(p, br.remain)
+	br.remain = br.remain[n:]
+	return n, nil
+}
+
+func BenchmarkReadSlice1000Int32s(b *testing.B) {
+	bsr := &byteSliceReader{}
+	slice := make([]int32, 1000)
+	buf := make([]byte, len(slice)*4)
+	b.SetBytes(int64(len(buf)))
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		bsr.remain = buf
+		Read(bsr, BigEndian, slice)
+	}
+}
+
+func BenchmarkReadStruct(b *testing.B) {
+	bsr := &byteSliceReader{}
+	var buf bytes.Buffer
+	Write(&buf, BigEndian, &s)
+	b.SetBytes(int64(dataSize(reflect.ValueOf(s))))
+	t := s
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		bsr.remain = buf.Bytes()
+		Read(bsr, BigEndian, &t)
+	}
+	b.StopTimer()
+	if b.N > 0 && !reflect.DeepEqual(s, t) {
+		b.Fatalf("struct doesn't match:\ngot  %v;\nwant %v", t, s)
+	}
+}
+
+func BenchmarkWriteStruct(b *testing.B) {
+	b.SetBytes(int64(Size(&s)))
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		Write(io.Discard, BigEndian, &s)
+	}
+}
+
+func BenchmarkReadInts(b *testing.B) {
+	var ls Struct
+	bsr := &byteSliceReader{}
+	var r io.Reader = bsr
+	b.SetBytes(2 * (1 + 2 + 4 + 8))
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		bsr.remain = big
+		Read(r, BigEndian, &ls.Int8)
+		Read(r, BigEndian, &ls.Int16)
+		Read(r, BigEndian, &ls.Int32)
+		Read(r, BigEndian, &ls.Int64)
+		Read(r, BigEndian, &ls.Uint8)
+		Read(r, BigEndian, &ls.Uint16)
+		Read(r, BigEndian, &ls.Uint32)
+		Read(r, BigEndian, &ls.Uint64)
+	}
+	b.StopTimer()
+	want := s
+	want.Float32 = 0
+	want.Float64 = 0
+	want.Complex64 = 0
+	want.Complex128 = 0
+	want.Array = [4]uint8{0, 0, 0, 0}
+	want.Bool = false
+	want.BoolArray = [4]bool{false, false, false, false}
+	if b.N > 0 && !reflect.DeepEqual(ls, want) {
+		b.Fatalf("struct doesn't match:\ngot  %v;\nwant %v", ls, want)
+	}
+}
+
+func BenchmarkWriteInts(b *testing.B) {
+	buf := new(bytes.Buffer)
+	var w io.Writer = buf
+	b.SetBytes(2 * (1 + 2 + 4 + 8))
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		buf.Reset()
+		Write(w, BigEndian, s.Int8)
+		Write(w, BigEndian, s.Int16)
+		Write(w, BigEndian, s.Int32)
+		Write(w, BigEndian, s.Int64)
+		Write(w, BigEndian, s.Uint8)
+		Write(w, BigEndian, s.Uint16)
+		Write(w, BigEndian, s.Uint32)
+		Write(w, BigEndian, s.Uint64)
+	}
+	b.StopTimer()
+	if b.N > 0 && !bytes.Equal(buf.Bytes(), big[:30]) {
+		b.Fatalf("first half doesn't match: %x %x", buf.Bytes(), big[:30])
+	}
+}
+
+func BenchmarkWriteSlice1000Int32s(b *testing.B) {
+	slice := make([]int32, 1000)
+	buf := new(bytes.Buffer)
+	var w io.Writer = buf
+	b.SetBytes(4 * 1000)
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		buf.Reset()
+		Write(w, BigEndian, slice)
+	}
+	b.StopTimer()
+}
+
+func BenchmarkPutUint16(b *testing.B) {
+	b.SetBytes(2)
+	for i := 0; i < b.N; i++ {
+		BigEndian.PutUint16(putbuf[:], uint16(i))
+	}
+}
+
+func BenchmarkPutUint32(b *testing.B) {
+	b.SetBytes(4)
+	for i := 0; i < b.N; i++ {
+		BigEndian.PutUint32(putbuf[:], uint32(i))
+	}
+}
+
+func BenchmarkPutUint64(b *testing.B) {
+	b.SetBytes(8)
+	for i := 0; i < b.N; i++ {
+		BigEndian.PutUint64(putbuf[:], uint64(i))
+	}
+}
+func BenchmarkLittleEndianPutUint16(b *testing.B) {
+	b.SetBytes(2)
+	for i := 0; i < b.N; i++ {
+		LittleEndian.PutUint16(putbuf[:], uint16(i))
+	}
+}
+
+func BenchmarkLittleEndianPutUint32(b *testing.B) {
+	b.SetBytes(4)
+	for i := 0; i < b.N; i++ {
+		LittleEndian.PutUint32(putbuf[:], uint32(i))
+	}
+}
+
+func BenchmarkLittleEndianPutUint64(b *testing.B) {
+	b.SetBytes(8)
+	for i := 0; i < b.N; i++ {
+		LittleEndian.PutUint64(putbuf[:], uint64(i))
+	}
+}
+
+func BenchmarkReadFloats(b *testing.B) {
+	var ls Struct
+	bsr := &byteSliceReader{}
+	var r io.Reader = bsr
+	b.SetBytes(4 + 8)
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		bsr.remain = big[30:]
+		Read(r, BigEndian, &ls.Float32)
+		Read(r, BigEndian, &ls.Float64)
+	}
+	b.StopTimer()
+	want := s
+	want.Int8 = 0
+	want.Int16 = 0
+	want.Int32 = 0
+	want.Int64 = 0
+	want.Uint8 = 0
+	want.Uint16 = 0
+	want.Uint32 = 0
+	want.Uint64 = 0
+	want.Complex64 = 0
+	want.Complex128 = 0
+	want.Array = [4]uint8{0, 0, 0, 0}
+	want.Bool = false
+	want.BoolArray = [4]bool{false, false, false, false}
+	if b.N > 0 && !reflect.DeepEqual(ls, want) {
+		b.Fatalf("struct doesn't match:\ngot  %v;\nwant %v", ls, want)
+	}
+}
+
+func BenchmarkWriteFloats(b *testing.B) {
+	buf := new(bytes.Buffer)
+	var w io.Writer = buf
+	b.SetBytes(4 + 8)
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		buf.Reset()
+		Write(w, BigEndian, s.Float32)
+		Write(w, BigEndian, s.Float64)
+	}
+	b.StopTimer()
+	if b.N > 0 && !bytes.Equal(buf.Bytes(), big[30:30+4+8]) {
+		b.Fatalf("first half doesn't match: %x %x", buf.Bytes(), big[30:30+4+8])
+	}
+}
+
+func BenchmarkReadSlice1000Float32s(b *testing.B) {
+	bsr := &byteSliceReader{}
+	slice := make([]float32, 1000)
+	buf := make([]byte, len(slice)*4)
+	b.SetBytes(int64(len(buf)))
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		bsr.remain = buf
+		Read(bsr, BigEndian, slice)
+	}
+}
+
+func BenchmarkWriteSlice1000Float32s(b *testing.B) {
+	slice := make([]float32, 1000)
+	buf := new(bytes.Buffer)
+	var w io.Writer = buf
+	b.SetBytes(4 * 1000)
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		buf.Reset()
+		Write(w, BigEndian, slice)
+	}
+	b.StopTimer()
+}
+
+func BenchmarkReadSlice1000Uint8s(b *testing.B) {
+	bsr := &byteSliceReader{}
+	slice := make([]uint8, 1000)
+	buf := make([]byte, len(slice))
+	b.SetBytes(int64(len(buf)))
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		bsr.remain = buf
+		Read(bsr, BigEndian, slice)
+	}
+}
+
+func BenchmarkWriteSlice1000Uint8s(b *testing.B) {
+	slice := make([]uint8, 1000)
+	buf := new(bytes.Buffer)
+	var w io.Writer = buf
+	b.SetBytes(1000)
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		buf.Reset()
+		Write(w, BigEndian, slice)
+	}
+}
diff --git a/src/encoding/binary/example_test.go b/src/encoding/binary/example_test.go
new file mode 100644
index 0000000..4c10daa
--- /dev/null
+++ b/src/encoding/binary/example_test.go
@@ -0,0 +1,187 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package binary_test
+
+import (
+	"bytes"
+	"encoding/binary"
+	"fmt"
+	"math"
+)
+
+func ExampleWrite() {
+	buf := new(bytes.Buffer)
+	var pi float64 = math.Pi
+	err := binary.Write(buf, binary.LittleEndian, pi)
+	if err != nil {
+		fmt.Println("binary.Write failed:", err)
+	}
+	fmt.Printf("% x", buf.Bytes())
+	// Output: 18 2d 44 54 fb 21 09 40
+}
+
+func ExampleWrite_multi() {
+	buf := new(bytes.Buffer)
+	var data = []any{
+		uint16(61374),
+		int8(-54),
+		uint8(254),
+	}
+	for _, v := range data {
+		err := binary.Write(buf, binary.LittleEndian, v)
+		if err != nil {
+			fmt.Println("binary.Write failed:", err)
+		}
+	}
+	fmt.Printf("%x", buf.Bytes())
+	// Output: beefcafe
+}
+
+func ExampleRead() {
+	var pi float64
+	b := []byte{0x18, 0x2d, 0x44, 0x54, 0xfb, 0x21, 0x09, 0x40}
+	buf := bytes.NewReader(b)
+	err := binary.Read(buf, binary.LittleEndian, &pi)
+	if err != nil {
+		fmt.Println("binary.Read failed:", err)
+	}
+	fmt.Print(pi)
+	// Output: 3.141592653589793
+}
+
+func ExampleRead_multi() {
+	b := []byte{0x18, 0x2d, 0x44, 0x54, 0xfb, 0x21, 0x09, 0x40, 0xff, 0x01, 0x02, 0x03, 0xbe, 0xef}
+	r := bytes.NewReader(b)
+
+	var data struct {
+		PI   float64
+		Uate uint8
+		Mine [3]byte
+		Too  uint16
+	}
+
+	if err := binary.Read(r, binary.LittleEndian, &data); err != nil {
+		fmt.Println("binary.Read failed:", err)
+	}
+
+	fmt.Println(data.PI)
+	fmt.Println(data.Uate)
+	fmt.Printf("% x\n", data.Mine)
+	fmt.Println(data.Too)
+	// Output:
+	// 3.141592653589793
+	// 255
+	// 01 02 03
+	// 61374
+}
+
+func ExampleByteOrder_put() {
+	b := make([]byte, 4)
+	binary.LittleEndian.PutUint16(b[0:], 0x03e8)
+	binary.LittleEndian.PutUint16(b[2:], 0x07d0)
+	fmt.Printf("% x\n", b)
+	// Output:
+	// e8 03 d0 07
+}
+
+func ExampleByteOrder_get() {
+	b := []byte{0xe8, 0x03, 0xd0, 0x07}
+	x1 := binary.LittleEndian.Uint16(b[0:])
+	x2 := binary.LittleEndian.Uint16(b[2:])
+	fmt.Printf("%#04x %#04x\n", x1, x2)
+	// Output:
+	// 0x03e8 0x07d0
+}
+
+func ExamplePutUvarint() {
+	buf := make([]byte, binary.MaxVarintLen64)
+
+	for _, x := range []uint64{1, 2, 127, 128, 255, 256} {
+		n := binary.PutUvarint(buf, x)
+		fmt.Printf("%x\n", buf[:n])
+	}
+	// Output:
+	// 01
+	// 02
+	// 7f
+	// 8001
+	// ff01
+	// 8002
+}
+
+func ExamplePutVarint() {
+	buf := make([]byte, binary.MaxVarintLen64)
+
+	for _, x := range []int64{-65, -64, -2, -1, 0, 1, 2, 63, 64} {
+		n := binary.PutVarint(buf, x)
+		fmt.Printf("%x\n", buf[:n])
+	}
+	// Output:
+	// 8101
+	// 7f
+	// 03
+	// 01
+	// 00
+	// 02
+	// 04
+	// 7e
+	// 8001
+}
+
+func ExampleUvarint() {
+	inputs := [][]byte{
+		{0x01},
+		{0x02},
+		{0x7f},
+		{0x80, 0x01},
+		{0xff, 0x01},
+		{0x80, 0x02},
+	}
+	for _, b := range inputs {
+		x, n := binary.Uvarint(b)
+		if n != len(b) {
+			fmt.Println("Uvarint did not consume all of in")
+		}
+		fmt.Println(x)
+	}
+	// Output:
+	// 1
+	// 2
+	// 127
+	// 128
+	// 255
+	// 256
+}
+
+func ExampleVarint() {
+	inputs := [][]byte{
+		{0x81, 0x01},
+		{0x7f},
+		{0x03},
+		{0x01},
+		{0x00},
+		{0x02},
+		{0x04},
+		{0x7e},
+		{0x80, 0x01},
+	}
+	for _, b := range inputs {
+		x, n := binary.Varint(b)
+		if n != len(b) {
+			fmt.Println("Varint did not consume all of in")
+		}
+		fmt.Println(x)
+	}
+	// Output:
+	// -65
+	// -64
+	// -2
+	// -1
+	// 0
+	// 1
+	// 2
+	// 63
+	// 64
+}
diff --git a/src/encoding/binary/varint.go b/src/encoding/binary/varint.go
new file mode 100644
index 0000000..8fe20b5
--- /dev/null
+++ b/src/encoding/binary/varint.go
@@ -0,0 +1,139 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package binary
+
+// This file implements "varint" encoding of 64-bit integers.
+// The encoding is:
+// - unsigned integers are serialized 7 bits at a time, starting with the
+//   least significant bits
+// - the most significant bit (msb) in each output byte indicates if there
+//   is a continuation byte (msb = 1)
+// - signed integers are mapped to unsigned integers using "zig-zag"
+//   encoding: Positive values x are written as 2*x + 0, negative values
+//   are written as 2*(^x) + 1; that is, negative numbers are complemented
+//   and whether to complement is encoded in bit 0.
+//
+// Design note:
+// At most 10 bytes are needed for 64-bit values. The encoding could
+// be more dense: a full 64-bit value needs an extra byte just to hold bit 63.
+// Instead, the msb of the previous byte could be used to hold bit 63 since we
+// know there can't be more than 64 bits. This is a trivial improvement and
+// would reduce the maximum encoding length to 9 bytes. However, it breaks the
+// invariant that the msb is always the "continuation bit" and thus makes the
+// format incompatible with a varint encoding for larger numbers (say 128-bit).
+
+import (
+	"errors"
+	"io"
+)
+
+// MaxVarintLenN is the maximum length of a varint-encoded N-bit integer.
+const (
+	MaxVarintLen16 = 3
+	MaxVarintLen32 = 5
+	MaxVarintLen64 = 10
+)
+
+// PutUvarint encodes a uint64 into buf and returns the number of bytes written.
+// If the buffer is too small, PutUvarint will panic.
+func PutUvarint(buf []byte, x uint64) int {
+	i := 0
+	for x >= 0x80 {
+		buf[i] = byte(x) | 0x80
+		x >>= 7
+		i++
+	}
+	buf[i] = byte(x)
+	return i + 1
+}
+
+// Uvarint decodes a uint64 from buf and returns that value and the
+// number of bytes read (> 0). If an error occurred, the value is 0
+// and the number of bytes n is <= 0 meaning:
+//
+// 	n == 0: buf too small
+// 	n  < 0: value larger than 64 bits (overflow)
+// 	        and -n is the number of bytes read
+//
+func Uvarint(buf []byte) (uint64, int) {
+	var x uint64
+	var s uint
+	for i, b := range buf {
+		if i == MaxVarintLen64 {
+			// Catch byte reads past MaxVarintLen64.
+			// See issue https://golang.org/issues/41185
+			return 0, -(i + 1) // overflow
+		}
+		if b < 0x80 {
+			if i == MaxVarintLen64-1 && b > 1 {
+				return 0, -(i + 1) // overflow
+			}
+			return x | uint64(b)<<s, i + 1
+		}
+		x |= uint64(b&0x7f) << s
+		s += 7
+	}
+	return 0, 0
+}
+
+// PutVarint encodes an int64 into buf and returns the number of bytes written.
+// If the buffer is too small, PutVarint will panic.
+func PutVarint(buf []byte, x int64) int {
+	ux := uint64(x) << 1
+	if x < 0 {
+		ux = ^ux
+	}
+	return PutUvarint(buf, ux)
+}
+
+// Varint decodes an int64 from buf and returns that value and the
+// number of bytes read (> 0). If an error occurred, the value is 0
+// and the number of bytes n is <= 0 with the following meaning:
+//
+// 	n == 0: buf too small
+// 	n  < 0: value larger than 64 bits (overflow)
+// 	        and -n is the number of bytes read
+//
+func Varint(buf []byte) (int64, int) {
+	ux, n := Uvarint(buf) // ok to continue in presence of error
+	x := int64(ux >> 1)
+	if ux&1 != 0 {
+		x = ^x
+	}
+	return x, n
+}
+
+var overflow = errors.New("binary: varint overflows a 64-bit integer")
+
+// ReadUvarint reads an encoded unsigned integer from r and returns it as a uint64.
+func ReadUvarint(r io.ByteReader) (uint64, error) {
+	var x uint64
+	var s uint
+	for i := 0; i < MaxVarintLen64; i++ {
+		b, err := r.ReadByte()
+		if err != nil {
+			return x, err
+		}
+		if b < 0x80 {
+			if i == MaxVarintLen64-1 && b > 1 {
+				return x, overflow
+			}
+			return x | uint64(b)<<s, nil
+		}
+		x |= uint64(b&0x7f) << s
+		s += 7
+	}
+	return x, overflow
+}
+
+// ReadVarint reads an encoded signed integer from r and returns it as an int64.
+func ReadVarint(r io.ByteReader) (int64, error) {
+	ux, err := ReadUvarint(r) // ok to continue in presence of error
+	x := int64(ux >> 1)
+	if ux&1 != 0 {
+		x = ^x
+	}
+	return x, err
+}
diff --git a/src/encoding/binary/varint_test.go b/src/encoding/binary/varint_test.go
new file mode 100644
index 0000000..d025a67
--- /dev/null
+++ b/src/encoding/binary/varint_test.go
@@ -0,0 +1,231 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package binary
+
+import (
+	"bytes"
+	"io"
+	"math"
+	"testing"
+)
+
+func testConstant(t *testing.T, w uint, max int) {
+	buf := make([]byte, MaxVarintLen64)
+	n := PutUvarint(buf, 1<<w-1)
+	if n != max {
+		t.Errorf("MaxVarintLen%d = %d; want %d", w, max, n)
+	}
+}
+
+func TestConstants(t *testing.T) {
+	testConstant(t, 16, MaxVarintLen16)
+	testConstant(t, 32, MaxVarintLen32)
+	testConstant(t, 64, MaxVarintLen64)
+}
+
+func testVarint(t *testing.T, x int64) {
+	buf := make([]byte, MaxVarintLen64)
+	n := PutVarint(buf, x)
+	y, m := Varint(buf[0:n])
+	if x != y {
+		t.Errorf("Varint(%d): got %d", x, y)
+	}
+	if n != m {
+		t.Errorf("Varint(%d): got n = %d; want %d", x, m, n)
+	}
+
+	y, err := ReadVarint(bytes.NewReader(buf))
+	if err != nil {
+		t.Errorf("ReadVarint(%d): %s", x, err)
+	}
+	if x != y {
+		t.Errorf("ReadVarint(%d): got %d", x, y)
+	}
+}
+
+func testUvarint(t *testing.T, x uint64) {
+	buf := make([]byte, MaxVarintLen64)
+	n := PutUvarint(buf, x)
+	y, m := Uvarint(buf[0:n])
+	if x != y {
+		t.Errorf("Uvarint(%d): got %d", x, y)
+	}
+	if n != m {
+		t.Errorf("Uvarint(%d): got n = %d; want %d", x, m, n)
+	}
+
+	y, err := ReadUvarint(bytes.NewReader(buf))
+	if err != nil {
+		t.Errorf("ReadUvarint(%d): %s", x, err)
+	}
+	if x != y {
+		t.Errorf("ReadUvarint(%d): got %d", x, y)
+	}
+}
+
+var tests = []int64{
+	-1 << 63,
+	-1<<63 + 1,
+	-1,
+	0,
+	1,
+	2,
+	10,
+	20,
+	63,
+	64,
+	65,
+	127,
+	128,
+	129,
+	255,
+	256,
+	257,
+	1<<63 - 1,
+}
+
+func TestVarint(t *testing.T) {
+	for _, x := range tests {
+		testVarint(t, x)
+		testVarint(t, -x)
+	}
+	for x := int64(0x7); x != 0; x <<= 1 {
+		testVarint(t, x)
+		testVarint(t, -x)
+	}
+}
+
+func TestUvarint(t *testing.T) {
+	for _, x := range tests {
+		testUvarint(t, uint64(x))
+	}
+	for x := uint64(0x7); x != 0; x <<= 1 {
+		testUvarint(t, x)
+	}
+}
+
+func TestBufferTooSmall(t *testing.T) {
+	buf := []byte{0x80, 0x80, 0x80, 0x80}
+	for i := 0; i <= len(buf); i++ {
+		buf := buf[0:i]
+		x, n := Uvarint(buf)
+		if x != 0 || n != 0 {
+			t.Errorf("Uvarint(%v): got x = %d, n = %d", buf, x, n)
+		}
+
+		x, err := ReadUvarint(bytes.NewReader(buf))
+		if x != 0 || err != io.EOF {
+			t.Errorf("ReadUvarint(%v): got x = %d, err = %s", buf, x, err)
+		}
+	}
+}
+
+// Ensure that we catch overflows of bytes going past MaxVarintLen64.
+// See issue https://golang.org/issues/41185
+func TestBufferTooBigWithOverflow(t *testing.T) {
+	tests := []struct {
+		in        []byte
+		name      string
+		wantN     int
+		wantValue uint64
+	}{
+		{
+			name: "invalid: 1000 bytes",
+			in: func() []byte {
+				b := make([]byte, 1000)
+				for i := range b {
+					b[i] = 0xff
+				}
+				b[999] = 0
+				return b
+			}(),
+			wantN:     -11,
+			wantValue: 0,
+		},
+		{
+			name:      "valid: math.MaxUint64-40",
+			in:        []byte{0xd7, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x01},
+			wantValue: math.MaxUint64 - 40,
+			wantN:     10,
+		},
+		{
+			name:      "invalid: with more than MaxVarintLen64 bytes",
+			in:        []byte{0xd7, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x01},
+			wantN:     -11,
+			wantValue: 0,
+		},
+		{
+			name:      "invalid: 10th byte",
+			in:        []byte{0xd7, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x7f},
+			wantN:     -10,
+			wantValue: 0,
+		},
+	}
+
+	for _, tt := range tests {
+		tt := tt
+		t.Run(tt.name, func(t *testing.T) {
+			value, n := Uvarint(tt.in)
+			if g, w := n, tt.wantN; g != w {
+				t.Errorf("bytes returned=%d, want=%d", g, w)
+			}
+			if g, w := value, tt.wantValue; g != w {
+				t.Errorf("value=%d, want=%d", g, w)
+			}
+		})
+	}
+}
+
+func testOverflow(t *testing.T, buf []byte, x0 uint64, n0 int, err0 error) {
+	x, n := Uvarint(buf)
+	if x != 0 || n != n0 {
+		t.Errorf("Uvarint(% X): got x = %d, n = %d; want 0, %d", buf, x, n, n0)
+	}
+
+	r := bytes.NewReader(buf)
+	len := r.Len()
+	x, err := ReadUvarint(r)
+	if x != x0 || err != err0 {
+		t.Errorf("ReadUvarint(%v): got x = %d, err = %s; want %d, %s", buf, x, err, x0, err0)
+	}
+	if read := len - r.Len(); read > MaxVarintLen64 {
+		t.Errorf("ReadUvarint(%v): read more than MaxVarintLen64 bytes, got %d", buf, read)
+	}
+}
+
+func TestOverflow(t *testing.T) {
+	testOverflow(t, []byte{0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x2}, 0, -10, overflow)
+	testOverflow(t, []byte{0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x1, 0, 0}, 0, -11, overflow)
+	testOverflow(t, []byte{0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF}, 1<<64-1, -11, overflow) // 11 bytes, should overflow
+}
+
+func TestNonCanonicalZero(t *testing.T) {
+	buf := []byte{0x80, 0x80, 0x80, 0}
+	x, n := Uvarint(buf)
+	if x != 0 || n != 4 {
+		t.Errorf("Uvarint(%v): got x = %d, n = %d; want 0, 4", buf, x, n)
+
+	}
+}
+
+func BenchmarkPutUvarint32(b *testing.B) {
+	buf := make([]byte, MaxVarintLen32)
+	b.SetBytes(4)
+	for i := 0; i < b.N; i++ {
+		for j := uint(0); j < MaxVarintLen32; j++ {
+			PutUvarint(buf, 1<<(j*7))
+		}
+	}
+}
+
+func BenchmarkPutUvarint64(b *testing.B) {
+	buf := make([]byte, MaxVarintLen64)
+	b.SetBytes(8)
+	for i := 0; i < b.N; i++ {
+		for j := uint(0); j < MaxVarintLen64; j++ {
+			PutUvarint(buf, 1<<(j*7))
+		}
+	}
+}
diff --git a/src/encoding/csv/example_test.go b/src/encoding/csv/example_test.go
new file mode 100644
index 0000000..dc227d4
--- /dev/null
+++ b/src/encoding/csv/example_test.go
@@ -0,0 +1,131 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package csv_test
+
+import (
+	"encoding/csv"
+	"fmt"
+	"io"
+	"log"
+	"os"
+	"strings"
+)
+
+func ExampleReader() {
+	in := `first_name,last_name,username
+"Rob","Pike",rob
+Ken,Thompson,ken
+"Robert","Griesemer","gri"
+`
+	r := csv.NewReader(strings.NewReader(in))
+
+	for {
+		record, err := r.Read()
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			log.Fatal(err)
+		}
+
+		fmt.Println(record)
+	}
+	// Output:
+	// [first_name last_name username]
+	// [Rob Pike rob]
+	// [Ken Thompson ken]
+	// [Robert Griesemer gri]
+}
+
+// This example shows how csv.Reader can be configured to handle other
+// types of CSV files.
+func ExampleReader_options() {
+	in := `first_name;last_name;username
+"Rob";"Pike";rob
+# lines beginning with a # character are ignored
+Ken;Thompson;ken
+"Robert";"Griesemer";"gri"
+`
+	r := csv.NewReader(strings.NewReader(in))
+	r.Comma = ';'
+	r.Comment = '#'
+
+	records, err := r.ReadAll()
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	fmt.Print(records)
+	// Output:
+	// [[first_name last_name username] [Rob Pike rob] [Ken Thompson ken] [Robert Griesemer gri]]
+}
+
+func ExampleReader_ReadAll() {
+	in := `first_name,last_name,username
+"Rob","Pike",rob
+Ken,Thompson,ken
+"Robert","Griesemer","gri"
+`
+	r := csv.NewReader(strings.NewReader(in))
+
+	records, err := r.ReadAll()
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	fmt.Print(records)
+	// Output:
+	// [[first_name last_name username] [Rob Pike rob] [Ken Thompson ken] [Robert Griesemer gri]]
+}
+
+func ExampleWriter() {
+	records := [][]string{
+		{"first_name", "last_name", "username"},
+		{"Rob", "Pike", "rob"},
+		{"Ken", "Thompson", "ken"},
+		{"Robert", "Griesemer", "gri"},
+	}
+
+	w := csv.NewWriter(os.Stdout)
+
+	for _, record := range records {
+		if err := w.Write(record); err != nil {
+			log.Fatalln("error writing record to csv:", err)
+		}
+	}
+
+	// Write any buffered data to the underlying writer (standard output).
+	w.Flush()
+
+	if err := w.Error(); err != nil {
+		log.Fatal(err)
+	}
+	// Output:
+	// first_name,last_name,username
+	// Rob,Pike,rob
+	// Ken,Thompson,ken
+	// Robert,Griesemer,gri
+}
+
+func ExampleWriter_WriteAll() {
+	records := [][]string{
+		{"first_name", "last_name", "username"},
+		{"Rob", "Pike", "rob"},
+		{"Ken", "Thompson", "ken"},
+		{"Robert", "Griesemer", "gri"},
+	}
+
+	w := csv.NewWriter(os.Stdout)
+	w.WriteAll(records) // calls Flush internally
+
+	if err := w.Error(); err != nil {
+		log.Fatalln("error writing csv:", err)
+	}
+	// Output:
+	// first_name,last_name,username
+	// Rob,Pike,rob
+	// Ken,Thompson,ken
+	// Robert,Griesemer,gri
+}
diff --git a/src/encoding/csv/fuzz.go b/src/encoding/csv/fuzz.go
new file mode 100644
index 0000000..5f5cdfc
--- /dev/null
+++ b/src/encoding/csv/fuzz.go
@@ -0,0 +1,70 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build gofuzz
+
+package csv
+
+import (
+	"bytes"
+	"fmt"
+	"reflect"
+)
+
+func Fuzz(data []byte) int {
+	score := 0
+	buf := new(bytes.Buffer)
+
+	for _, tt := range []Reader{
+		{},
+		{Comma: ';'},
+		{Comma: '\t'},
+		{LazyQuotes: true},
+		{TrimLeadingSpace: true},
+		{Comment: '#'},
+		{Comment: ';'},
+	} {
+		r := NewReader(bytes.NewReader(data))
+		r.Comma = tt.Comma
+		r.Comment = tt.Comment
+		r.LazyQuotes = tt.LazyQuotes
+		r.TrimLeadingSpace = tt.TrimLeadingSpace
+
+		records, err := r.ReadAll()
+		if err != nil {
+			continue
+		}
+		score = 1
+
+		buf.Reset()
+		w := NewWriter(buf)
+		w.Comma = tt.Comma
+		err = w.WriteAll(records)
+		if err != nil {
+			fmt.Printf("writer  = %#v\n", w)
+			fmt.Printf("records = %v\n", records)
+			panic(err)
+		}
+
+		r = NewReader(buf)
+		r.Comma = tt.Comma
+		r.Comment = tt.Comment
+		r.LazyQuotes = tt.LazyQuotes
+		r.TrimLeadingSpace = tt.TrimLeadingSpace
+		result, err := r.ReadAll()
+		if err != nil {
+			fmt.Printf("reader  = %#v\n", r)
+			fmt.Printf("records = %v\n", records)
+			panic(err)
+		}
+
+		if !reflect.DeepEqual(records, result) {
+			fmt.Println("records = \n", records)
+			fmt.Println("result  = \n", records)
+			panic("not equal")
+		}
+	}
+
+	return score
+}
diff --git a/src/encoding/csv/reader.go b/src/encoding/csv/reader.go
new file mode 100644
index 0000000..f860f4f
--- /dev/null
+++ b/src/encoding/csv/reader.go
@@ -0,0 +1,450 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package csv reads and writes comma-separated values (CSV) files.
+// There are many kinds of CSV files; this package supports the format
+// described in RFC 4180.
+//
+// A csv file contains zero or more records of one or more fields per record.
+// Each record is separated by the newline character. The final record may
+// optionally be followed by a newline character.
+//
+//	field1,field2,field3
+//
+// White space is considered part of a field.
+//
+// Carriage returns before newline characters are silently removed.
+//
+// Blank lines are ignored. A line with only whitespace characters (excluding
+// the ending newline character) is not considered a blank line.
+//
+// Fields which start and stop with the quote character " are called
+// quoted-fields. The beginning and ending quote are not part of the
+// field.
+//
+// The source:
+//
+//	normal string,"quoted-field"
+//
+// results in the fields
+//
+//	{`normal string`, `quoted-field`}
+//
+// Within a quoted-field a quote character followed by a second quote
+// character is considered a single quote.
+//
+//	"the ""word"" is true","a ""quoted-field"""
+//
+// results in
+//
+//	{`the "word" is true`, `a "quoted-field"`}
+//
+// Newlines and commas may be included in a quoted-field
+//
+//	"Multi-line
+//	field","comma is ,"
+//
+// results in
+//
+//	{`Multi-line
+//	field`, `comma is ,`}
+package csv
+
+import (
+	"bufio"
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"unicode"
+	"unicode/utf8"
+)
+
+// A ParseError is returned for parsing errors.
+// Line numbers are 1-indexed and columns are 0-indexed.
+type ParseError struct {
+	StartLine int   // Line where the record starts
+	Line      int   // Line where the error occurred
+	Column    int   // Column (1-based byte index) where the error occurred
+	Err       error // The actual error
+}
+
+func (e *ParseError) Error() string {
+	if e.Err == ErrFieldCount {
+		return fmt.Sprintf("record on line %d: %v", e.Line, e.Err)
+	}
+	if e.StartLine != e.Line {
+		return fmt.Sprintf("record on line %d; parse error on line %d, column %d: %v", e.StartLine, e.Line, e.Column, e.Err)
+	}
+	return fmt.Sprintf("parse error on line %d, column %d: %v", e.Line, e.Column, e.Err)
+}
+
+func (e *ParseError) Unwrap() error { return e.Err }
+
+// These are the errors that can be returned in ParseError.Err.
+var (
+	ErrTrailingComma = errors.New("extra delimiter at end of line") // Deprecated: No longer used.
+	ErrBareQuote     = errors.New("bare \" in non-quoted-field")
+	ErrQuote         = errors.New("extraneous or missing \" in quoted-field")
+	ErrFieldCount    = errors.New("wrong number of fields")
+)
+
+var errInvalidDelim = errors.New("csv: invalid field or comment delimiter")
+
+func validDelim(r rune) bool {
+	return r != 0 && r != '"' && r != '\r' && r != '\n' && utf8.ValidRune(r) && r != utf8.RuneError
+}
+
+// A Reader reads records from a CSV-encoded file.
+//
+// As returned by NewReader, a Reader expects input conforming to RFC 4180.
+// The exported fields can be changed to customize the details before the
+// first call to Read or ReadAll.
+//
+// The Reader converts all \r\n sequences in its input to plain \n,
+// including in multiline field values, so that the returned data does
+// not depend on which line-ending convention an input file uses.
+type Reader struct {
+	// Comma is the field delimiter.
+	// It is set to comma (',') by NewReader.
+	// Comma must be a valid rune and must not be \r, \n,
+	// or the Unicode replacement character (0xFFFD).
+	Comma rune
+
+	// Comment, if not 0, is the comment character. Lines beginning with the
+	// Comment character without preceding whitespace are ignored.
+	// With leading whitespace the Comment character becomes part of the
+	// field, even if TrimLeadingSpace is true.
+	// Comment must be a valid rune and must not be \r, \n,
+	// or the Unicode replacement character (0xFFFD).
+	// It must also not be equal to Comma.
+	Comment rune
+
+	// FieldsPerRecord is the number of expected fields per record.
+	// If FieldsPerRecord is positive, Read requires each record to
+	// have the given number of fields. If FieldsPerRecord is 0, Read sets it to
+	// the number of fields in the first record, so that future records must
+	// have the same field count. If FieldsPerRecord is negative, no check is
+	// made and records may have a variable number of fields.
+	FieldsPerRecord int
+
+	// If LazyQuotes is true, a quote may appear in an unquoted field and a
+	// non-doubled quote may appear in a quoted field.
+	LazyQuotes bool
+
+	// If TrimLeadingSpace is true, leading white space in a field is ignored.
+	// This is done even if the field delimiter, Comma, is white space.
+	TrimLeadingSpace bool
+
+	// ReuseRecord controls whether calls to Read may return a slice sharing
+	// the backing array of the previous call's returned slice for performance.
+	// By default, each call to Read returns newly allocated memory owned by the caller.
+	ReuseRecord bool
+
+	TrailingComma bool // Deprecated: No longer used.
+
+	r *bufio.Reader
+
+	// numLine is the current line being read in the CSV file.
+	numLine int
+
+	// rawBuffer is a line buffer only used by the readLine method.
+	rawBuffer []byte
+
+	// recordBuffer holds the unescaped fields, one after another.
+	// The fields can be accessed by using the indexes in fieldIndexes.
+	// E.g., For the row `a,"b","c""d",e`, recordBuffer will contain `abc"de`
+	// and fieldIndexes will contain the indexes [1, 2, 5, 6].
+	recordBuffer []byte
+
+	// fieldIndexes is an index of fields inside recordBuffer.
+	// The i'th field ends at offset fieldIndexes[i] in recordBuffer.
+	fieldIndexes []int
+
+	// fieldPositions is an index of field positions for the
+	// last record returned by Read.
+	fieldPositions []position
+
+	// lastRecord is a record cache and only used when ReuseRecord == true.
+	lastRecord []string
+}
+
+// NewReader returns a new Reader that reads from r.
+func NewReader(r io.Reader) *Reader {
+	return &Reader{
+		Comma: ',',
+		r:     bufio.NewReader(r),
+	}
+}
+
+// Read reads one record (a slice of fields) from r.
+// If the record has an unexpected number of fields,
+// Read returns the record along with the error ErrFieldCount.
+// Except for that case, Read always returns either a non-nil
+// record or a non-nil error, but not both.
+// If there is no data left to be read, Read returns nil, io.EOF.
+// If ReuseRecord is true, the returned slice may be shared
+// between multiple calls to Read.
+func (r *Reader) Read() (record []string, err error) {
+	if r.ReuseRecord {
+		record, err = r.readRecord(r.lastRecord)
+		r.lastRecord = record
+	} else {
+		record, err = r.readRecord(nil)
+	}
+	return record, err
+}
+
+// FieldPos returns the line and column corresponding to
+// the start of the field with the given index in the slice most recently
+// returned by Read. Numbering of lines and columns starts at 1;
+// columns are counted in bytes, not runes.
+//
+// If this is called with an out-of-bounds index, it panics.
+func (r *Reader) FieldPos(field int) (line, column int) {
+	if field < 0 || field >= len(r.fieldPositions) {
+		panic("out of range index passed to FieldPos")
+	}
+	p := &r.fieldPositions[field]
+	return p.line, p.col
+}
+
+// pos holds the position of a field in the current line.
+type position struct {
+	line, col int
+}
+
+// ReadAll reads all the remaining records from r.
+// Each record is a slice of fields.
+// A successful call returns err == nil, not err == io.EOF. Because ReadAll is
+// defined to read until EOF, it does not treat end of file as an error to be
+// reported.
+func (r *Reader) ReadAll() (records [][]string, err error) {
+	for {
+		record, err := r.readRecord(nil)
+		if err == io.EOF {
+			return records, nil
+		}
+		if err != nil {
+			return nil, err
+		}
+		records = append(records, record)
+	}
+}
+
+// readLine reads the next line (with the trailing endline).
+// If EOF is hit without a trailing endline, it will be omitted.
+// If some bytes were read, then the error is never io.EOF.
+// The result is only valid until the next call to readLine.
+func (r *Reader) readLine() ([]byte, error) {
+	line, err := r.r.ReadSlice('\n')
+	if err == bufio.ErrBufferFull {
+		r.rawBuffer = append(r.rawBuffer[:0], line...)
+		for err == bufio.ErrBufferFull {
+			line, err = r.r.ReadSlice('\n')
+			r.rawBuffer = append(r.rawBuffer, line...)
+		}
+		line = r.rawBuffer
+	}
+	if len(line) > 0 && err == io.EOF {
+		err = nil
+		// For backwards compatibility, drop trailing \r before EOF.
+		if line[len(line)-1] == '\r' {
+			line = line[:len(line)-1]
+		}
+	}
+	r.numLine++
+	// Normalize \r\n to \n on all input lines.
+	if n := len(line); n >= 2 && line[n-2] == '\r' && line[n-1] == '\n' {
+		line[n-2] = '\n'
+		line = line[:n-1]
+	}
+	return line, err
+}
+
+// lengthNL reports the number of bytes for the trailing \n.
+func lengthNL(b []byte) int {
+	if len(b) > 0 && b[len(b)-1] == '\n' {
+		return 1
+	}
+	return 0
+}
+
+// nextRune returns the next rune in b or utf8.RuneError.
+func nextRune(b []byte) rune {
+	r, _ := utf8.DecodeRune(b)
+	return r
+}
+
+func (r *Reader) readRecord(dst []string) ([]string, error) {
+	if r.Comma == r.Comment || !validDelim(r.Comma) || (r.Comment != 0 && !validDelim(r.Comment)) {
+		return nil, errInvalidDelim
+	}
+
+	// Read line (automatically skipping past empty lines and any comments).
+	var line []byte
+	var errRead error
+	for errRead == nil {
+		line, errRead = r.readLine()
+		if r.Comment != 0 && nextRune(line) == r.Comment {
+			line = nil
+			continue // Skip comment lines
+		}
+		if errRead == nil && len(line) == lengthNL(line) {
+			line = nil
+			continue // Skip empty lines
+		}
+		break
+	}
+	if errRead == io.EOF {
+		return nil, errRead
+	}
+
+	// Parse each field in the record.
+	var err error
+	const quoteLen = len(`"`)
+	commaLen := utf8.RuneLen(r.Comma)
+	recLine := r.numLine // Starting line for record
+	r.recordBuffer = r.recordBuffer[:0]
+	r.fieldIndexes = r.fieldIndexes[:0]
+	r.fieldPositions = r.fieldPositions[:0]
+	pos := position{line: r.numLine, col: 1}
+parseField:
+	for {
+		if r.TrimLeadingSpace {
+			i := bytes.IndexFunc(line, func(r rune) bool {
+				return !unicode.IsSpace(r)
+			})
+			if i < 0 {
+				i = len(line)
+				pos.col -= lengthNL(line)
+			}
+			line = line[i:]
+			pos.col += i
+		}
+		if len(line) == 0 || line[0] != '"' {
+			// Non-quoted string field
+			i := bytes.IndexRune(line, r.Comma)
+			field := line
+			if i >= 0 {
+				field = field[:i]
+			} else {
+				field = field[:len(field)-lengthNL(field)]
+			}
+			// Check to make sure a quote does not appear in field.
+			if !r.LazyQuotes {
+				if j := bytes.IndexByte(field, '"'); j >= 0 {
+					col := pos.col + j
+					err = &ParseError{StartLine: recLine, Line: r.numLine, Column: col, Err: ErrBareQuote}
+					break parseField
+				}
+			}
+			r.recordBuffer = append(r.recordBuffer, field...)
+			r.fieldIndexes = append(r.fieldIndexes, len(r.recordBuffer))
+			r.fieldPositions = append(r.fieldPositions, pos)
+			if i >= 0 {
+				line = line[i+commaLen:]
+				pos.col += i + commaLen
+				continue parseField
+			}
+			break parseField
+		} else {
+			// Quoted string field
+			fieldPos := pos
+			line = line[quoteLen:]
+			pos.col += quoteLen
+			for {
+				i := bytes.IndexByte(line, '"')
+				if i >= 0 {
+					// Hit next quote.
+					r.recordBuffer = append(r.recordBuffer, line[:i]...)
+					line = line[i+quoteLen:]
+					pos.col += i + quoteLen
+					switch rn := nextRune(line); {
+					case rn == '"':
+						// `""` sequence (append quote).
+						r.recordBuffer = append(r.recordBuffer, '"')
+						line = line[quoteLen:]
+						pos.col += quoteLen
+					case rn == r.Comma:
+						// `",` sequence (end of field).
+						line = line[commaLen:]
+						pos.col += commaLen
+						r.fieldIndexes = append(r.fieldIndexes, len(r.recordBuffer))
+						r.fieldPositions = append(r.fieldPositions, fieldPos)
+						continue parseField
+					case lengthNL(line) == len(line):
+						// `"\n` sequence (end of line).
+						r.fieldIndexes = append(r.fieldIndexes, len(r.recordBuffer))
+						r.fieldPositions = append(r.fieldPositions, fieldPos)
+						break parseField
+					case r.LazyQuotes:
+						// `"` sequence (bare quote).
+						r.recordBuffer = append(r.recordBuffer, '"')
+					default:
+						// `"*` sequence (invalid non-escaped quote).
+						err = &ParseError{StartLine: recLine, Line: r.numLine, Column: pos.col - quoteLen, Err: ErrQuote}
+						break parseField
+					}
+				} else if len(line) > 0 {
+					// Hit end of line (copy all data so far).
+					r.recordBuffer = append(r.recordBuffer, line...)
+					if errRead != nil {
+						break parseField
+					}
+					pos.col += len(line)
+					line, errRead = r.readLine()
+					if len(line) > 0 {
+						pos.line++
+						pos.col = 1
+					}
+					if errRead == io.EOF {
+						errRead = nil
+					}
+				} else {
+					// Abrupt end of file (EOF or error).
+					if !r.LazyQuotes && errRead == nil {
+						err = &ParseError{StartLine: recLine, Line: pos.line, Column: pos.col, Err: ErrQuote}
+						break parseField
+					}
+					r.fieldIndexes = append(r.fieldIndexes, len(r.recordBuffer))
+					r.fieldPositions = append(r.fieldPositions, fieldPos)
+					break parseField
+				}
+			}
+		}
+	}
+	if err == nil {
+		err = errRead
+	}
+
+	// Create a single string and create slices out of it.
+	// This pins the memory of the fields together, but allocates once.
+	str := string(r.recordBuffer) // Convert to string once to batch allocations
+	dst = dst[:0]
+	if cap(dst) < len(r.fieldIndexes) {
+		dst = make([]string, len(r.fieldIndexes))
+	}
+	dst = dst[:len(r.fieldIndexes)]
+	var preIdx int
+	for i, idx := range r.fieldIndexes {
+		dst[i] = str[preIdx:idx]
+		preIdx = idx
+	}
+
+	// Check or update the expected fields per record.
+	if r.FieldsPerRecord > 0 {
+		if len(dst) != r.FieldsPerRecord && err == nil {
+			err = &ParseError{
+				StartLine: recLine,
+				Line:      recLine,
+				Column:    1,
+				Err:       ErrFieldCount,
+			}
+		}
+	} else if r.FieldsPerRecord == 0 {
+		r.FieldsPerRecord = len(dst)
+	}
+	return dst, err
+}
diff --git a/src/encoding/csv/reader_test.go b/src/encoding/csv/reader_test.go
new file mode 100644
index 0000000..abe3fdf
--- /dev/null
+++ b/src/encoding/csv/reader_test.go
@@ -0,0 +1,650 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package csv
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"reflect"
+	"strings"
+	"testing"
+	"unicode/utf8"
+)
+
+type readTest struct {
+	Name      string
+	Input     string
+	Output    [][]string
+	Positions [][][2]int
+	Errors    []error
+
+	// These fields are copied into the Reader
+	Comma              rune
+	Comment            rune
+	UseFieldsPerRecord bool // false (default) means FieldsPerRecord is -1
+	FieldsPerRecord    int
+	LazyQuotes         bool
+	TrimLeadingSpace   bool
+	ReuseRecord        bool
+}
+
+// In these tests, the §, ¶ and ∑ characters in readTest.Input are used to denote
+// the start of a field, a record boundary and the position of an error respectively.
+// They are removed before parsing and are used to verify the position
+// information reported by FieldPos.
+
+var readTests = []readTest{{
+	Name:   "Simple",
+	Input:  "§a,§b,§c\n",
+	Output: [][]string{{"a", "b", "c"}},
+}, {
+	Name:   "CRLF",
+	Input:  "§a,§b\r\n¶§c,§d\r\n",
+	Output: [][]string{{"a", "b"}, {"c", "d"}},
+}, {
+	Name:   "BareCR",
+	Input:  "§a,§b\rc,§d\r\n",
+	Output: [][]string{{"a", "b\rc", "d"}},
+}, {
+	Name: "RFC4180test",
+	Input: `§#field1,§field2,§field3
+¶§"aaa",§"bb
+b",§"ccc"
+¶§"a,a",§"b""bb",§"ccc"
+¶§zzz,§yyy,§xxx
+`,
+	Output: [][]string{
+		{"#field1", "field2", "field3"},
+		{"aaa", "bb\nb", "ccc"},
+		{"a,a", `b"bb`, "ccc"},
+		{"zzz", "yyy", "xxx"},
+	},
+	UseFieldsPerRecord: true,
+	FieldsPerRecord:    0,
+}, {
+	Name:   "NoEOLTest",
+	Input:  "§a,§b,§c",
+	Output: [][]string{{"a", "b", "c"}},
+}, {
+	Name:   "Semicolon",
+	Input:  "§a;§b;§c\n",
+	Output: [][]string{{"a", "b", "c"}},
+	Comma:  ';',
+}, {
+	Name: "MultiLine",
+	Input: `§"two
+line",§"one line",§"three
+line
+field"`,
+	Output: [][]string{{"two\nline", "one line", "three\nline\nfield"}},
+}, {
+	Name:  "BlankLine",
+	Input: "§a,§b,§c\n\n¶§d,§e,§f\n\n",
+	Output: [][]string{
+		{"a", "b", "c"},
+		{"d", "e", "f"},
+	},
+}, {
+	Name:  "BlankLineFieldCount",
+	Input: "§a,§b,§c\n\n¶§d,§e,§f\n\n",
+	Output: [][]string{
+		{"a", "b", "c"},
+		{"d", "e", "f"},
+	},
+	UseFieldsPerRecord: true,
+	FieldsPerRecord:    0,
+}, {
+	Name:             "TrimSpace",
+	Input:            " §a,  §b,   §c\n",
+	Output:           [][]string{{"a", "b", "c"}},
+	TrimLeadingSpace: true,
+}, {
+	Name:   "LeadingSpace",
+	Input:  "§ a,§  b,§   c\n",
+	Output: [][]string{{" a", "  b", "   c"}},
+}, {
+	Name:    "Comment",
+	Input:   "#1,2,3\n§a,§b,§c\n#comment",
+	Output:  [][]string{{"a", "b", "c"}},
+	Comment: '#',
+}, {
+	Name:   "NoComment",
+	Input:  "§#1,§2,§3\n¶§a,§b,§c",
+	Output: [][]string{{"#1", "2", "3"}, {"a", "b", "c"}},
+}, {
+	Name:       "LazyQuotes",
+	Input:      `§a "word",§"1"2",§a",§"b`,
+	Output:     [][]string{{`a "word"`, `1"2`, `a"`, `b`}},
+	LazyQuotes: true,
+}, {
+	Name:       "BareQuotes",
+	Input:      `§a "word",§"1"2",§a"`,
+	Output:     [][]string{{`a "word"`, `1"2`, `a"`}},
+	LazyQuotes: true,
+}, {
+	Name:       "BareDoubleQuotes",
+	Input:      `§a""b,§c`,
+	Output:     [][]string{{`a""b`, `c`}},
+	LazyQuotes: true,
+}, {
+	Name:   "BadDoubleQuotes",
+	Input:  `§a∑""b,c`,
+	Errors: []error{&ParseError{Err: ErrBareQuote}},
+}, {
+	Name:             "TrimQuote",
+	Input:            ` §"a",§" b",§c`,
+	Output:           [][]string{{"a", " b", "c"}},
+	TrimLeadingSpace: true,
+}, {
+	Name:   "BadBareQuote",
+	Input:  `§a ∑"word","b"`,
+	Errors: []error{&ParseError{Err: ErrBareQuote}},
+}, {
+	Name:   "BadTrailingQuote",
+	Input:  `§"a word",b∑"`,
+	Errors: []error{&ParseError{Err: ErrBareQuote}},
+}, {
+	Name:   "ExtraneousQuote",
+	Input:  `§"a ∑"word","b"`,
+	Errors: []error{&ParseError{Err: ErrQuote}},
+}, {
+	Name:               "BadFieldCount",
+	Input:              "§a,§b,§c\n¶∑§d,§e",
+	Errors:             []error{nil, &ParseError{Err: ErrFieldCount}},
+	Output:             [][]string{{"a", "b", "c"}, {"d", "e"}},
+	UseFieldsPerRecord: true,
+	FieldsPerRecord:    0,
+}, {
+	Name:               "BadFieldCountMultiple",
+	Input:              "§a,§b,§c\n¶∑§d,§e\n¶∑§f",
+	Errors:             []error{nil, &ParseError{Err: ErrFieldCount}, &ParseError{Err: ErrFieldCount}},
+	Output:             [][]string{{"a", "b", "c"}, {"d", "e"}, {"f"}},
+	UseFieldsPerRecord: true,
+	FieldsPerRecord:    0,
+}, {
+	Name:               "BadFieldCount1",
+	Input:              `§∑a,§b,§c`,
+	Errors:             []error{&ParseError{Err: ErrFieldCount}},
+	Output:             [][]string{{"a", "b", "c"}},
+	UseFieldsPerRecord: true,
+	FieldsPerRecord:    2,
+}, {
+	Name:   "FieldCount",
+	Input:  "§a,§b,§c\n¶§d,§e",
+	Output: [][]string{{"a", "b", "c"}, {"d", "e"}},
+}, {
+	Name:   "TrailingCommaEOF",
+	Input:  "§a,§b,§c,§",
+	Output: [][]string{{"a", "b", "c", ""}},
+}, {
+	Name:   "TrailingCommaEOL",
+	Input:  "§a,§b,§c,§\n",
+	Output: [][]string{{"a", "b", "c", ""}},
+}, {
+	Name:             "TrailingCommaSpaceEOF",
+	Input:            "§a,§b,§c, §",
+	Output:           [][]string{{"a", "b", "c", ""}},
+	TrimLeadingSpace: true,
+}, {
+	Name:             "TrailingCommaSpaceEOL",
+	Input:            "§a,§b,§c, §\n",
+	Output:           [][]string{{"a", "b", "c", ""}},
+	TrimLeadingSpace: true,
+}, {
+	Name:             "TrailingCommaLine3",
+	Input:            "§a,§b,§c\n¶§d,§e,§f\n¶§g,§hi,§",
+	Output:           [][]string{{"a", "b", "c"}, {"d", "e", "f"}, {"g", "hi", ""}},
+	TrimLeadingSpace: true,
+}, {
+	Name:   "NotTrailingComma3",
+	Input:  "§a,§b,§c,§ \n",
+	Output: [][]string{{"a", "b", "c", " "}},
+}, {
+	Name: "CommaFieldTest",
+	Input: `§x,§y,§z,§w
+¶§x,§y,§z,§
+¶§x,§y,§,§
+¶§x,§,§,§
+¶§,§,§,§
+¶§"x",§"y",§"z",§"w"
+¶§"x",§"y",§"z",§""
+¶§"x",§"y",§"",§""
+¶§"x",§"",§"",§""
+¶§"",§"",§"",§""
+`,
+	Output: [][]string{
+		{"x", "y", "z", "w"},
+		{"x", "y", "z", ""},
+		{"x", "y", "", ""},
+		{"x", "", "", ""},
+		{"", "", "", ""},
+		{"x", "y", "z", "w"},
+		{"x", "y", "z", ""},
+		{"x", "y", "", ""},
+		{"x", "", "", ""},
+		{"", "", "", ""},
+	},
+}, {
+	Name:  "TrailingCommaIneffective1",
+	Input: "§a,§b,§\n¶§c,§d,§e",
+	Output: [][]string{
+		{"a", "b", ""},
+		{"c", "d", "e"},
+	},
+	TrimLeadingSpace: true,
+}, {
+	Name:  "ReadAllReuseRecord",
+	Input: "§a,§b\n¶§c,§d",
+	Output: [][]string{
+		{"a", "b"},
+		{"c", "d"},
+	},
+	ReuseRecord: true,
+}, {
+	Name:   "StartLine1", // Issue 19019
+	Input:  "§a,\"b\nc∑\"d,e",
+	Errors: []error{&ParseError{Err: ErrQuote}},
+}, {
+	Name:   "StartLine2",
+	Input:  "§a,§b\n¶§\"d\n\n,e∑",
+	Errors: []error{nil, &ParseError{Err: ErrQuote}},
+	Output: [][]string{{"a", "b"}},
+}, {
+	Name:  "CRLFInQuotedField", // Issue 21201
+	Input: "§A,§\"Hello\r\nHi\",§B\r\n",
+	Output: [][]string{
+		{"A", "Hello\nHi", "B"},
+	},
+}, {
+	Name:   "BinaryBlobField", // Issue 19410
+	Input:  "§x09\x41\xb4\x1c,§aktau",
+	Output: [][]string{{"x09A\xb4\x1c", "aktau"}},
+}, {
+	Name:   "TrailingCR",
+	Input:  "§field1,§field2\r",
+	Output: [][]string{{"field1", "field2"}},
+}, {
+	Name:   "QuotedTrailingCR",
+	Input:  "§\"field\"\r",
+	Output: [][]string{{"field"}},
+}, {
+	Name:   "QuotedTrailingCRCR",
+	Input:  "§\"field∑\"\r\r",
+	Errors: []error{&ParseError{Err: ErrQuote}},
+}, {
+	Name:   "FieldCR",
+	Input:  "§field\rfield\r",
+	Output: [][]string{{"field\rfield"}},
+}, {
+	Name:   "FieldCRCR",
+	Input:  "§field\r\rfield\r\r",
+	Output: [][]string{{"field\r\rfield\r"}},
+}, {
+	Name:   "FieldCRCRLF",
+	Input:  "§field\r\r\n¶§field\r\r\n",
+	Output: [][]string{{"field\r"}, {"field\r"}},
+}, {
+	Name:   "FieldCRCRLFCR",
+	Input:  "§field\r\r\n¶§\rfield\r\r\n\r",
+	Output: [][]string{{"field\r"}, {"\rfield\r"}},
+}, {
+	Name:   "FieldCRCRLFCRCR",
+	Input:  "§field\r\r\n¶§\r\rfield\r\r\n¶§\r\r",
+	Output: [][]string{{"field\r"}, {"\r\rfield\r"}, {"\r"}},
+}, {
+	Name:  "MultiFieldCRCRLFCRCR",
+	Input: "§field1,§field2\r\r\n¶§\r\rfield1,§field2\r\r\n¶§\r\r,§",
+	Output: [][]string{
+		{"field1", "field2\r"},
+		{"\r\rfield1", "field2\r"},
+		{"\r\r", ""},
+	},
+}, {
+	Name:             "NonASCIICommaAndComment",
+	Input:            "§a£§b,c£ \t§d,e\n€ comment\n",
+	Output:           [][]string{{"a", "b,c", "d,e"}},
+	TrimLeadingSpace: true,
+	Comma:            '£',
+	Comment:          '€',
+}, {
+	Name:    "NonASCIICommaAndCommentWithQuotes",
+	Input:   "§a€§\"  b,\"€§ c\nλ comment\n",
+	Output:  [][]string{{"a", "  b,", " c"}},
+	Comma:   '€',
+	Comment: 'λ',
+}, {
+	// λ and θ start with the same byte.
+	// This tests that the parser doesn't confuse such characters.
+	Name:    "NonASCIICommaConfusion",
+	Input:   "§\"abθcd\"λ§efθgh",
+	Output:  [][]string{{"abθcd", "efθgh"}},
+	Comma:   'λ',
+	Comment: '€',
+}, {
+	Name:    "NonASCIICommentConfusion",
+	Input:   "§λ\n¶§λ\nθ\n¶§λ\n",
+	Output:  [][]string{{"λ"}, {"λ"}, {"λ"}},
+	Comment: 'θ',
+}, {
+	Name:   "QuotedFieldMultipleLF",
+	Input:  "§\"\n\n\n\n\"",
+	Output: [][]string{{"\n\n\n\n"}},
+}, {
+	Name:  "MultipleCRLF",
+	Input: "\r\n\r\n\r\n\r\n",
+}, {
+	// The implementation may read each line in several chunks if it doesn't fit entirely
+	// in the read buffer, so we should test the code to handle that condition.
+	Name:    "HugeLines",
+	Input:   strings.Repeat("#ignore\n", 10000) + "§" + strings.Repeat("@", 5000) + ",§" + strings.Repeat("*", 5000),
+	Output:  [][]string{{strings.Repeat("@", 5000), strings.Repeat("*", 5000)}},
+	Comment: '#',
+}, {
+	Name:   "QuoteWithTrailingCRLF",
+	Input:  "§\"foo∑\"bar\"\r\n",
+	Errors: []error{&ParseError{Err: ErrQuote}},
+}, {
+	Name:       "LazyQuoteWithTrailingCRLF",
+	Input:      "§\"foo\"bar\"\r\n",
+	Output:     [][]string{{`foo"bar`}},
+	LazyQuotes: true,
+}, {
+	Name:   "DoubleQuoteWithTrailingCRLF",
+	Input:  "§\"foo\"\"bar\"\r\n",
+	Output: [][]string{{`foo"bar`}},
+}, {
+	Name:   "EvenQuotes",
+	Input:  `§""""""""`,
+	Output: [][]string{{`"""`}},
+}, {
+	Name:   "OddQuotes",
+	Input:  `§"""""""∑`,
+	Errors: []error{&ParseError{Err: ErrQuote}},
+}, {
+	Name:       "LazyOddQuotes",
+	Input:      `§"""""""`,
+	Output:     [][]string{{`"""`}},
+	LazyQuotes: true,
+}, {
+	Name:   "BadComma1",
+	Comma:  '\n',
+	Errors: []error{errInvalidDelim},
+}, {
+	Name:   "BadComma2",
+	Comma:  '\r',
+	Errors: []error{errInvalidDelim},
+}, {
+	Name:   "BadComma3",
+	Comma:  '"',
+	Errors: []error{errInvalidDelim},
+}, {
+	Name:   "BadComma4",
+	Comma:  utf8.RuneError,
+	Errors: []error{errInvalidDelim},
+}, {
+	Name:    "BadComment1",
+	Comment: '\n',
+	Errors:  []error{errInvalidDelim},
+}, {
+	Name:    "BadComment2",
+	Comment: '\r',
+	Errors:  []error{errInvalidDelim},
+}, {
+	Name:    "BadComment3",
+	Comment: utf8.RuneError,
+	Errors:  []error{errInvalidDelim},
+}, {
+	Name:    "BadCommaComment",
+	Comma:   'X',
+	Comment: 'X',
+	Errors:  []error{errInvalidDelim},
+}}
+
+func TestRead(t *testing.T) {
+	newReader := func(tt readTest) (*Reader, [][][2]int, map[int][2]int) {
+		positions, errPositions, input := makePositions(tt.Input)
+		r := NewReader(strings.NewReader(input))
+
+		if tt.Comma != 0 {
+			r.Comma = tt.Comma
+		}
+		r.Comment = tt.Comment
+		if tt.UseFieldsPerRecord {
+			r.FieldsPerRecord = tt.FieldsPerRecord
+		} else {
+			r.FieldsPerRecord = -1
+		}
+		r.LazyQuotes = tt.LazyQuotes
+		r.TrimLeadingSpace = tt.TrimLeadingSpace
+		r.ReuseRecord = tt.ReuseRecord
+		return r, positions, errPositions
+	}
+
+	for _, tt := range readTests {
+		t.Run(tt.Name, func(t *testing.T) {
+			r, positions, errPositions := newReader(tt)
+			out, err := r.ReadAll()
+			if wantErr := firstError(tt.Errors, positions, errPositions); wantErr != nil {
+				if !reflect.DeepEqual(err, wantErr) {
+					t.Fatalf("ReadAll() error mismatch:\ngot  %v (%#v)\nwant %v (%#v)", err, err, wantErr, wantErr)
+				}
+				if out != nil {
+					t.Fatalf("ReadAll() output:\ngot  %q\nwant nil", out)
+				}
+			} else {
+				if err != nil {
+					t.Fatalf("unexpected Readall() error: %v", err)
+				}
+				if !reflect.DeepEqual(out, tt.Output) {
+					t.Fatalf("ReadAll() output:\ngot  %q\nwant %q", out, tt.Output)
+				}
+			}
+
+			// Check field and error positions.
+			r, _, _ = newReader(tt)
+			for recNum := 0; ; recNum++ {
+				rec, err := r.Read()
+				var wantErr error
+				if recNum < len(tt.Errors) && tt.Errors[recNum] != nil {
+					wantErr = errorWithPosition(tt.Errors[recNum], recNum, positions, errPositions)
+				} else if recNum >= len(tt.Output) {
+					wantErr = io.EOF
+				}
+				if !reflect.DeepEqual(err, wantErr) {
+					t.Fatalf("Read() error at record %d:\ngot %v (%#v)\nwant %v (%#v)", recNum, err, err, wantErr, wantErr)
+				}
+				// ErrFieldCount is explicitly non-fatal.
+				if err != nil && !errors.Is(err, ErrFieldCount) {
+					if recNum < len(tt.Output) {
+						t.Fatalf("need more records; got %d want %d", recNum, len(tt.Output))
+					}
+					break
+				}
+				if got, want := rec, tt.Output[recNum]; !reflect.DeepEqual(got, want) {
+					t.Errorf("Read vs ReadAll mismatch;\ngot %q\nwant %q", got, want)
+				}
+				pos := positions[recNum]
+				if len(pos) != len(rec) {
+					t.Fatalf("mismatched position length at record %d", recNum)
+				}
+				for i := range rec {
+					line, col := r.FieldPos(i)
+					if got, want := [2]int{line, col}, pos[i]; got != want {
+						t.Errorf("position mismatch at record %d, field %d;\ngot %v\nwant %v", recNum, i, got, want)
+					}
+				}
+			}
+		})
+	}
+}
+
+// firstError returns the first non-nil error in errs,
+// with the position adjusted according to the error's
+// index inside positions.
+func firstError(errs []error, positions [][][2]int, errPositions map[int][2]int) error {
+	for i, err := range errs {
+		if err != nil {
+			return errorWithPosition(err, i, positions, errPositions)
+		}
+	}
+	return nil
+}
+
+func errorWithPosition(err error, recNum int, positions [][][2]int, errPositions map[int][2]int) error {
+	parseErr, ok := err.(*ParseError)
+	if !ok {
+		return err
+	}
+	if recNum >= len(positions) {
+		panic(fmt.Errorf("no positions found for error at record %d", recNum))
+	}
+	errPos, ok := errPositions[recNum]
+	if !ok {
+		panic(fmt.Errorf("no error position found for error at record %d", recNum))
+	}
+	parseErr1 := *parseErr
+	parseErr1.StartLine = positions[recNum][0][0]
+	parseErr1.Line = errPos[0]
+	parseErr1.Column = errPos[1]
+	return &parseErr1
+}
+
+// makePositions returns the expected field positions of all
+// the fields in text, the positions of any errors, and the text with the position markers
+// removed.
+//
+// The start of each field is marked with a § symbol;
+// CSV lines are separated by ¶ symbols;
+// Error positions are marked with ∑ symbols.
+func makePositions(text string) ([][][2]int, map[int][2]int, string) {
+	buf := make([]byte, 0, len(text))
+	var positions [][][2]int
+	errPositions := make(map[int][2]int)
+	line, col := 1, 1
+	recNum := 0
+
+	for len(text) > 0 {
+		r, size := utf8.DecodeRuneInString(text)
+		switch r {
+		case '\n':
+			line++
+			col = 1
+			buf = append(buf, '\n')
+		case '§':
+			if len(positions) == 0 {
+				positions = append(positions, [][2]int{})
+			}
+			positions[len(positions)-1] = append(positions[len(positions)-1], [2]int{line, col})
+		case '¶':
+			positions = append(positions, [][2]int{})
+			recNum++
+		case '∑':
+			errPositions[recNum] = [2]int{line, col}
+		default:
+			buf = append(buf, text[:size]...)
+			col += size
+		}
+		text = text[size:]
+	}
+	return positions, errPositions, string(buf)
+}
+
+// nTimes is an io.Reader which yields the string s n times.
+type nTimes struct {
+	s   string
+	n   int
+	off int
+}
+
+func (r *nTimes) Read(p []byte) (n int, err error) {
+	for {
+		if r.n <= 0 || r.s == "" {
+			return n, io.EOF
+		}
+		n0 := copy(p, r.s[r.off:])
+		p = p[n0:]
+		n += n0
+		r.off += n0
+		if r.off == len(r.s) {
+			r.off = 0
+			r.n--
+		}
+		if len(p) == 0 {
+			return
+		}
+	}
+}
+
+// benchmarkRead measures reading the provided CSV rows data.
+// initReader, if non-nil, modifies the Reader before it's used.
+func benchmarkRead(b *testing.B, initReader func(*Reader), rows string) {
+	b.ReportAllocs()
+	r := NewReader(&nTimes{s: rows, n: b.N})
+	if initReader != nil {
+		initReader(r)
+	}
+	for {
+		_, err := r.Read()
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			b.Fatal(err)
+		}
+	}
+}
+
+const benchmarkCSVData = `x,y,z,w
+x,y,z,
+x,y,,
+x,,,
+,,,
+"x","y","z","w"
+"x","y","z",""
+"x","y","",""
+"x","","",""
+"","","",""
+`
+
+func BenchmarkRead(b *testing.B) {
+	benchmarkRead(b, nil, benchmarkCSVData)
+}
+
+func BenchmarkReadWithFieldsPerRecord(b *testing.B) {
+	benchmarkRead(b, func(r *Reader) { r.FieldsPerRecord = 4 }, benchmarkCSVData)
+}
+
+func BenchmarkReadWithoutFieldsPerRecord(b *testing.B) {
+	benchmarkRead(b, func(r *Reader) { r.FieldsPerRecord = -1 }, benchmarkCSVData)
+}
+
+func BenchmarkReadLargeFields(b *testing.B) {
+	benchmarkRead(b, nil, strings.Repeat(`xxxxxxxxxxxxxxxx,yyyyyyyyyyyyyyyy,zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz,wwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwww,vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
+xxxxxxxxxxxxxxxxxxxxxxxx,yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy,zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz,wwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwww,vvvv
+,,zzzz,wwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwww,vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
+xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx,yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy,zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz,wwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwww,vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
+`, 3))
+}
+
+func BenchmarkReadReuseRecord(b *testing.B) {
+	benchmarkRead(b, func(r *Reader) { r.ReuseRecord = true }, benchmarkCSVData)
+}
+
+func BenchmarkReadReuseRecordWithFieldsPerRecord(b *testing.B) {
+	benchmarkRead(b, func(r *Reader) { r.ReuseRecord = true; r.FieldsPerRecord = 4 }, benchmarkCSVData)
+}
+
+func BenchmarkReadReuseRecordWithoutFieldsPerRecord(b *testing.B) {
+	benchmarkRead(b, func(r *Reader) { r.ReuseRecord = true; r.FieldsPerRecord = -1 }, benchmarkCSVData)
+}
+
+func BenchmarkReadReuseRecordLargeFields(b *testing.B) {
+	benchmarkRead(b, func(r *Reader) { r.ReuseRecord = true }, strings.Repeat(`xxxxxxxxxxxxxxxx,yyyyyyyyyyyyyyyy,zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz,wwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwww,vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
+xxxxxxxxxxxxxxxxxxxxxxxx,yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy,zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz,wwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwww,vvvv
+,,zzzz,wwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwww,vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
+xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx,yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy,zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz,wwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwww,vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
+`, 3))
+}
diff --git a/src/encoding/csv/writer.go b/src/encoding/csv/writer.go
new file mode 100644
index 0000000..ac64b4d
--- /dev/null
+++ b/src/encoding/csv/writer.go
@@ -0,0 +1,181 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package csv
+
+import (
+	"bufio"
+	"io"
+	"strings"
+	"unicode"
+	"unicode/utf8"
+)
+
+// A Writer writes records using CSV encoding.
+//
+// As returned by NewWriter, a Writer writes records terminated by a
+// newline and uses ',' as the field delimiter. The exported fields can be
+// changed to customize the details before the first call to Write or WriteAll.
+//
+// Comma is the field delimiter.
+//
+// If UseCRLF is true, the Writer ends each output line with \r\n instead of \n.
+//
+// The writes of individual records are buffered.
+// After all data has been written, the client should call the
+// Flush method to guarantee all data has been forwarded to
+// the underlying io.Writer.  Any errors that occurred should
+// be checked by calling the Error method.
+type Writer struct {
+	Comma   rune // Field delimiter (set to ',' by NewWriter)
+	UseCRLF bool // True to use \r\n as the line terminator
+	w       *bufio.Writer
+}
+
+// NewWriter returns a new Writer that writes to w.
+func NewWriter(w io.Writer) *Writer {
+	return &Writer{
+		Comma: ',',
+		w:     bufio.NewWriter(w),
+	}
+}
+
+// Write writes a single CSV record to w along with any necessary quoting.
+// A record is a slice of strings with each string being one field.
+// Writes are buffered, so Flush must eventually be called to ensure
+// that the record is written to the underlying io.Writer.
+func (w *Writer) Write(record []string) error {
+	if !validDelim(w.Comma) {
+		return errInvalidDelim
+	}
+
+	for n, field := range record {
+		if n > 0 {
+			if _, err := w.w.WriteRune(w.Comma); err != nil {
+				return err
+			}
+		}
+
+		// If we don't have to have a quoted field then just
+		// write out the field and continue to the next field.
+		if !w.fieldNeedsQuotes(field) {
+			if _, err := w.w.WriteString(field); err != nil {
+				return err
+			}
+			continue
+		}
+
+		if err := w.w.WriteByte('"'); err != nil {
+			return err
+		}
+		for len(field) > 0 {
+			// Search for special characters.
+			i := strings.IndexAny(field, "\"\r\n")
+			if i < 0 {
+				i = len(field)
+			}
+
+			// Copy verbatim everything before the special character.
+			if _, err := w.w.WriteString(field[:i]); err != nil {
+				return err
+			}
+			field = field[i:]
+
+			// Encode the special character.
+			if len(field) > 0 {
+				var err error
+				switch field[0] {
+				case '"':
+					_, err = w.w.WriteString(`""`)
+				case '\r':
+					if !w.UseCRLF {
+						err = w.w.WriteByte('\r')
+					}
+				case '\n':
+					if w.UseCRLF {
+						_, err = w.w.WriteString("\r\n")
+					} else {
+						err = w.w.WriteByte('\n')
+					}
+				}
+				field = field[1:]
+				if err != nil {
+					return err
+				}
+			}
+		}
+		if err := w.w.WriteByte('"'); err != nil {
+			return err
+		}
+	}
+	var err error
+	if w.UseCRLF {
+		_, err = w.w.WriteString("\r\n")
+	} else {
+		err = w.w.WriteByte('\n')
+	}
+	return err
+}
+
+// Flush writes any buffered data to the underlying io.Writer.
+// To check if an error occurred during the Flush, call Error.
+func (w *Writer) Flush() {
+	w.w.Flush()
+}
+
+// Error reports any error that has occurred during a previous Write or Flush.
+func (w *Writer) Error() error {
+	_, err := w.w.Write(nil)
+	return err
+}
+
+// WriteAll writes multiple CSV records to w using Write and then calls Flush,
+// returning any error from the Flush.
+func (w *Writer) WriteAll(records [][]string) error {
+	for _, record := range records {
+		err := w.Write(record)
+		if err != nil {
+			return err
+		}
+	}
+	return w.w.Flush()
+}
+
+// fieldNeedsQuotes reports whether our field must be enclosed in quotes.
+// Fields with a Comma, fields with a quote or newline, and
+// fields which start with a space must be enclosed in quotes.
+// We used to quote empty strings, but we do not anymore (as of Go 1.4).
+// The two representations should be equivalent, but Postgres distinguishes
+// quoted vs non-quoted empty string during database imports, and it has
+// an option to force the quoted behavior for non-quoted CSV but it has
+// no option to force the non-quoted behavior for quoted CSV, making
+// CSV with quoted empty strings strictly less useful.
+// Not quoting the empty string also makes this package match the behavior
+// of Microsoft Excel and Google Drive.
+// For Postgres, quote the data terminating string `\.`.
+func (w *Writer) fieldNeedsQuotes(field string) bool {
+	if field == "" {
+		return false
+	}
+
+	if field == `\.` {
+		return true
+	}
+
+	if w.Comma < utf8.RuneSelf {
+		for i := 0; i < len(field); i++ {
+			c := field[i]
+			if c == '\n' || c == '\r' || c == '"' || c == byte(w.Comma) {
+				return true
+			}
+		}
+	} else {
+		if strings.ContainsRune(field, w.Comma) || strings.ContainsAny(field, "\"\r\n") {
+			return true
+		}
+	}
+
+	r1, _ := utf8.DecodeRuneInString(field)
+	return unicode.IsSpace(r1)
+}
diff --git a/src/encoding/csv/writer_test.go b/src/encoding/csv/writer_test.go
new file mode 100644
index 0000000..ab28b0d
--- /dev/null
+++ b/src/encoding/csv/writer_test.go
@@ -0,0 +1,112 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package csv
+
+import (
+	"bytes"
+	"errors"
+	"testing"
+)
+
+var writeTests = []struct {
+	Input   [][]string
+	Output  string
+	Error   error
+	UseCRLF bool
+	Comma   rune
+}{
+	{Input: [][]string{{"abc"}}, Output: "abc\n"},
+	{Input: [][]string{{"abc"}}, Output: "abc\r\n", UseCRLF: true},
+	{Input: [][]string{{`"abc"`}}, Output: `"""abc"""` + "\n"},
+	{Input: [][]string{{`a"b`}}, Output: `"a""b"` + "\n"},
+	{Input: [][]string{{`"a"b"`}}, Output: `"""a""b"""` + "\n"},
+	{Input: [][]string{{" abc"}}, Output: `" abc"` + "\n"},
+	{Input: [][]string{{"abc,def"}}, Output: `"abc,def"` + "\n"},
+	{Input: [][]string{{"abc", "def"}}, Output: "abc,def\n"},
+	{Input: [][]string{{"abc"}, {"def"}}, Output: "abc\ndef\n"},
+	{Input: [][]string{{"abc\ndef"}}, Output: "\"abc\ndef\"\n"},
+	{Input: [][]string{{"abc\ndef"}}, Output: "\"abc\r\ndef\"\r\n", UseCRLF: true},
+	{Input: [][]string{{"abc\rdef"}}, Output: "\"abcdef\"\r\n", UseCRLF: true},
+	{Input: [][]string{{"abc\rdef"}}, Output: "\"abc\rdef\"\n", UseCRLF: false},
+	{Input: [][]string{{""}}, Output: "\n"},
+	{Input: [][]string{{"", ""}}, Output: ",\n"},
+	{Input: [][]string{{"", "", ""}}, Output: ",,\n"},
+	{Input: [][]string{{"", "", "a"}}, Output: ",,a\n"},
+	{Input: [][]string{{"", "a", ""}}, Output: ",a,\n"},
+	{Input: [][]string{{"", "a", "a"}}, Output: ",a,a\n"},
+	{Input: [][]string{{"a", "", ""}}, Output: "a,,\n"},
+	{Input: [][]string{{"a", "", "a"}}, Output: "a,,a\n"},
+	{Input: [][]string{{"a", "a", ""}}, Output: "a,a,\n"},
+	{Input: [][]string{{"a", "a", "a"}}, Output: "a,a,a\n"},
+	{Input: [][]string{{`\.`}}, Output: "\"\\.\"\n"},
+	{Input: [][]string{{"x09\x41\xb4\x1c", "aktau"}}, Output: "x09\x41\xb4\x1c,aktau\n"},
+	{Input: [][]string{{",x09\x41\xb4\x1c", "aktau"}}, Output: "\",x09\x41\xb4\x1c\",aktau\n"},
+	{Input: [][]string{{"a", "a", ""}}, Output: "a|a|\n", Comma: '|'},
+	{Input: [][]string{{",", ",", ""}}, Output: ",|,|\n", Comma: '|'},
+	{Input: [][]string{{"foo"}}, Comma: '"', Error: errInvalidDelim},
+}
+
+func TestWrite(t *testing.T) {
+	for n, tt := range writeTests {
+		b := &bytes.Buffer{}
+		f := NewWriter(b)
+		f.UseCRLF = tt.UseCRLF
+		if tt.Comma != 0 {
+			f.Comma = tt.Comma
+		}
+		err := f.WriteAll(tt.Input)
+		if err != tt.Error {
+			t.Errorf("Unexpected error:\ngot  %v\nwant %v", err, tt.Error)
+		}
+		out := b.String()
+		if out != tt.Output {
+			t.Errorf("#%d: out=%q want %q", n, out, tt.Output)
+		}
+	}
+}
+
+type errorWriter struct{}
+
+func (e errorWriter) Write(b []byte) (int, error) {
+	return 0, errors.New("Test")
+}
+
+func TestError(t *testing.T) {
+	b := &bytes.Buffer{}
+	f := NewWriter(b)
+	f.Write([]string{"abc"})
+	f.Flush()
+	err := f.Error()
+
+	if err != nil {
+		t.Errorf("Unexpected error: %s\n", err)
+	}
+
+	f = NewWriter(errorWriter{})
+	f.Write([]string{"abc"})
+	f.Flush()
+	err = f.Error()
+
+	if err == nil {
+		t.Error("Error should not be nil")
+	}
+}
+
+var benchmarkWriteData = [][]string{
+	{"abc", "def", "12356", "1234567890987654311234432141542132"},
+	{"abc", "def", "12356", "1234567890987654311234432141542132"},
+	{"abc", "def", "12356", "1234567890987654311234432141542132"},
+}
+
+func BenchmarkWrite(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		w := NewWriter(&bytes.Buffer{})
+		err := w.WriteAll(benchmarkWriteData)
+		if err != nil {
+			b.Fatal(err)
+		}
+		w.Flush()
+	}
+}
diff --git a/src/encoding/encoding.go b/src/encoding/encoding.go
new file mode 100644
index 0000000..cc5a536
--- /dev/null
+++ b/src/encoding/encoding.go
@@ -0,0 +1,48 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package encoding defines interfaces shared by other packages that
+// convert data to and from byte-level and textual representations.
+// Packages that check for these interfaces include encoding/gob,
+// encoding/json, and encoding/xml. As a result, implementing an
+// interface once can make a type useful in multiple encodings.
+// Standard types that implement these interfaces include time.Time and net.IP.
+// The interfaces come in pairs that produce and consume encoded data.
+package encoding
+
+// BinaryMarshaler is the interface implemented by an object that can
+// marshal itself into a binary form.
+//
+// MarshalBinary encodes the receiver into a binary form and returns the result.
+type BinaryMarshaler interface {
+	MarshalBinary() (data []byte, err error)
+}
+
+// BinaryUnmarshaler is the interface implemented by an object that can
+// unmarshal a binary representation of itself.
+//
+// UnmarshalBinary must be able to decode the form generated by MarshalBinary.
+// UnmarshalBinary must copy the data if it wishes to retain the data
+// after returning.
+type BinaryUnmarshaler interface {
+	UnmarshalBinary(data []byte) error
+}
+
+// TextMarshaler is the interface implemented by an object that can
+// marshal itself into a textual form.
+//
+// MarshalText encodes the receiver into UTF-8-encoded text and returns the result.
+type TextMarshaler interface {
+	MarshalText() (text []byte, err error)
+}
+
+// TextUnmarshaler is the interface implemented by an object that can
+// unmarshal a textual representation of itself.
+//
+// UnmarshalText must be able to decode the form generated by MarshalText.
+// UnmarshalText must copy the text if it wishes to retain the text
+// after returning.
+type TextUnmarshaler interface {
+	UnmarshalText(text []byte) error
+}
diff --git a/src/encoding/gob/codec_test.go b/src/encoding/gob/codec_test.go
new file mode 100644
index 0000000..1ca9d87
--- /dev/null
+++ b/src/encoding/gob/codec_test.go
@@ -0,0 +1,1529 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package gob
+
+import (
+	"bytes"
+	"errors"
+	"flag"
+	"math"
+	"math/rand"
+	"reflect"
+	"strings"
+	"testing"
+	"time"
+)
+
+var doFuzzTests = flag.Bool("gob.fuzz", false, "run the fuzz tests, which are large and very slow")
+
+// Guarantee encoding format by comparing some encodings to hand-written values
+type EncodeT struct {
+	x uint64
+	b []byte
+}
+
+var encodeT = []EncodeT{
+	{0x00, []byte{0x00}},
+	{0x0F, []byte{0x0F}},
+	{0xFF, []byte{0xFF, 0xFF}},
+	{0xFFFF, []byte{0xFE, 0xFF, 0xFF}},
+	{0xFFFFFF, []byte{0xFD, 0xFF, 0xFF, 0xFF}},
+	{0xFFFFFFFF, []byte{0xFC, 0xFF, 0xFF, 0xFF, 0xFF}},
+	{0xFFFFFFFFFF, []byte{0xFB, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF}},
+	{0xFFFFFFFFFFFF, []byte{0xFA, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF}},
+	{0xFFFFFFFFFFFFFF, []byte{0xF9, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF}},
+	{0xFFFFFFFFFFFFFFFF, []byte{0xF8, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF}},
+	{0x1111, []byte{0xFE, 0x11, 0x11}},
+	{0x1111111111111111, []byte{0xF8, 0x11, 0x11, 0x11, 0x11, 0x11, 0x11, 0x11, 0x11}},
+	{0x8888888888888888, []byte{0xF8, 0x88, 0x88, 0x88, 0x88, 0x88, 0x88, 0x88, 0x88}},
+	{1 << 63, []byte{0xF8, 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}},
+}
+
+// testError is meant to be used as a deferred function to turn a panic(gobError) into a
+// plain test.Error call.
+func testError(t *testing.T) {
+	if e := recover(); e != nil {
+		t.Error(e.(gobError).err) // Will re-panic if not one of our errors, such as a runtime error.
+	}
+}
+
+func newDecBuffer(data []byte) *decBuffer {
+	return &decBuffer{
+		data: data,
+	}
+}
+
+// Test basic encode/decode routines for unsigned integers
+func TestUintCodec(t *testing.T) {
+	defer testError(t)
+	b := new(encBuffer)
+	encState := newEncoderState(b)
+	for _, tt := range encodeT {
+		b.Reset()
+		encState.encodeUint(tt.x)
+		if !bytes.Equal(tt.b, b.Bytes()) {
+			t.Errorf("encodeUint: %#x encode: expected % x got % x", tt.x, tt.b, b.Bytes())
+		}
+	}
+	for u := uint64(0); ; u = (u + 1) * 7 {
+		b.Reset()
+		encState.encodeUint(u)
+		decState := newDecodeState(newDecBuffer(b.Bytes()))
+		v := decState.decodeUint()
+		if u != v {
+			t.Errorf("Encode/Decode: sent %#x received %#x", u, v)
+		}
+		if u&(1<<63) != 0 {
+			break
+		}
+	}
+}
+
+func verifyInt(i int64, t *testing.T) {
+	defer testError(t)
+	var b = new(encBuffer)
+	encState := newEncoderState(b)
+	encState.encodeInt(i)
+	decState := newDecodeState(newDecBuffer(b.Bytes()))
+	j := decState.decodeInt()
+	if i != j {
+		t.Errorf("Encode/Decode: sent %#x received %#x", uint64(i), uint64(j))
+	}
+}
+
+// Test basic encode/decode routines for signed integers
+func TestIntCodec(t *testing.T) {
+	for u := uint64(0); ; u = (u + 1) * 7 {
+		// Do positive and negative values
+		i := int64(u)
+		verifyInt(i, t)
+		verifyInt(-i, t)
+		verifyInt(^i, t)
+		if u&(1<<63) != 0 {
+			break
+		}
+	}
+	verifyInt(-1<<63, t) // a tricky case
+}
+
+// The result of encoding a true boolean with field number 7
+var boolResult = []byte{0x07, 0x01}
+
+// The result of encoding a number 17 with field number 7
+var signedResult = []byte{0x07, 2 * 17}
+var unsignedResult = []byte{0x07, 17}
+var floatResult = []byte{0x07, 0xFE, 0x31, 0x40}
+
+// The result of encoding a number 17+19i with field number 7
+var complexResult = []byte{0x07, 0xFE, 0x31, 0x40, 0xFE, 0x33, 0x40}
+
+// The result of encoding "hello" with field number 7
+var bytesResult = []byte{0x07, 0x05, 'h', 'e', 'l', 'l', 'o'}
+
+func newDecodeState(buf *decBuffer) *decoderState {
+	d := new(decoderState)
+	d.b = buf
+	return d
+}
+
+func newEncoderState(b *encBuffer) *encoderState {
+	b.Reset()
+	state := &encoderState{enc: nil, b: b}
+	state.fieldnum = -1
+	return state
+}
+
+// Test instruction execution for encoding.
+// Do not run the machine yet; instead do individual instructions crafted by hand.
+func TestScalarEncInstructions(t *testing.T) {
+	var b = new(encBuffer)
+
+	// bool
+	{
+		var data bool = true
+		instr := &encInstr{encBool, 6, nil, 0}
+		state := newEncoderState(b)
+		instr.op(instr, state, reflect.ValueOf(data))
+		if !bytes.Equal(boolResult, b.Bytes()) {
+			t.Errorf("bool enc instructions: expected % x got % x", boolResult, b.Bytes())
+		}
+	}
+
+	// int
+	{
+		b.Reset()
+		var data int = 17
+		instr := &encInstr{encInt, 6, nil, 0}
+		state := newEncoderState(b)
+		instr.op(instr, state, reflect.ValueOf(data))
+		if !bytes.Equal(signedResult, b.Bytes()) {
+			t.Errorf("int enc instructions: expected % x got % x", signedResult, b.Bytes())
+		}
+	}
+
+	// uint
+	{
+		b.Reset()
+		var data uint = 17
+		instr := &encInstr{encUint, 6, nil, 0}
+		state := newEncoderState(b)
+		instr.op(instr, state, reflect.ValueOf(data))
+		if !bytes.Equal(unsignedResult, b.Bytes()) {
+			t.Errorf("uint enc instructions: expected % x got % x", unsignedResult, b.Bytes())
+		}
+	}
+
+	// int8
+	{
+		b.Reset()
+		var data int8 = 17
+		instr := &encInstr{encInt, 6, nil, 0}
+		state := newEncoderState(b)
+		instr.op(instr, state, reflect.ValueOf(data))
+		if !bytes.Equal(signedResult, b.Bytes()) {
+			t.Errorf("int8 enc instructions: expected % x got % x", signedResult, b.Bytes())
+		}
+	}
+
+	// uint8
+	{
+		b.Reset()
+		var data uint8 = 17
+		instr := &encInstr{encUint, 6, nil, 0}
+		state := newEncoderState(b)
+		instr.op(instr, state, reflect.ValueOf(data))
+		if !bytes.Equal(unsignedResult, b.Bytes()) {
+			t.Errorf("uint8 enc instructions: expected % x got % x", unsignedResult, b.Bytes())
+		}
+	}
+
+	// int16
+	{
+		b.Reset()
+		var data int16 = 17
+		instr := &encInstr{encInt, 6, nil, 0}
+		state := newEncoderState(b)
+		instr.op(instr, state, reflect.ValueOf(data))
+		if !bytes.Equal(signedResult, b.Bytes()) {
+			t.Errorf("int16 enc instructions: expected % x got % x", signedResult, b.Bytes())
+		}
+	}
+
+	// uint16
+	{
+		b.Reset()
+		var data uint16 = 17
+		instr := &encInstr{encUint, 6, nil, 0}
+		state := newEncoderState(b)
+		instr.op(instr, state, reflect.ValueOf(data))
+		if !bytes.Equal(unsignedResult, b.Bytes()) {
+			t.Errorf("uint16 enc instructions: expected % x got % x", unsignedResult, b.Bytes())
+		}
+	}
+
+	// int32
+	{
+		b.Reset()
+		var data int32 = 17
+		instr := &encInstr{encInt, 6, nil, 0}
+		state := newEncoderState(b)
+		instr.op(instr, state, reflect.ValueOf(data))
+		if !bytes.Equal(signedResult, b.Bytes()) {
+			t.Errorf("int32 enc instructions: expected % x got % x", signedResult, b.Bytes())
+		}
+	}
+
+	// uint32
+	{
+		b.Reset()
+		var data uint32 = 17
+		instr := &encInstr{encUint, 6, nil, 0}
+		state := newEncoderState(b)
+		instr.op(instr, state, reflect.ValueOf(data))
+		if !bytes.Equal(unsignedResult, b.Bytes()) {
+			t.Errorf("uint32 enc instructions: expected % x got % x", unsignedResult, b.Bytes())
+		}
+	}
+
+	// int64
+	{
+		b.Reset()
+		var data int64 = 17
+		instr := &encInstr{encInt, 6, nil, 0}
+		state := newEncoderState(b)
+		instr.op(instr, state, reflect.ValueOf(data))
+		if !bytes.Equal(signedResult, b.Bytes()) {
+			t.Errorf("int64 enc instructions: expected % x got % x", signedResult, b.Bytes())
+		}
+	}
+
+	// uint64
+	{
+		b.Reset()
+		var data uint64 = 17
+		instr := &encInstr{encUint, 6, nil, 0}
+		state := newEncoderState(b)
+		instr.op(instr, state, reflect.ValueOf(data))
+		if !bytes.Equal(unsignedResult, b.Bytes()) {
+			t.Errorf("uint64 enc instructions: expected % x got % x", unsignedResult, b.Bytes())
+		}
+	}
+
+	// float32
+	{
+		b.Reset()
+		var data float32 = 17
+		instr := &encInstr{encFloat, 6, nil, 0}
+		state := newEncoderState(b)
+		instr.op(instr, state, reflect.ValueOf(data))
+		if !bytes.Equal(floatResult, b.Bytes()) {
+			t.Errorf("float32 enc instructions: expected % x got % x", floatResult, b.Bytes())
+		}
+	}
+
+	// float64
+	{
+		b.Reset()
+		var data float64 = 17
+		instr := &encInstr{encFloat, 6, nil, 0}
+		state := newEncoderState(b)
+		instr.op(instr, state, reflect.ValueOf(data))
+		if !bytes.Equal(floatResult, b.Bytes()) {
+			t.Errorf("float64 enc instructions: expected % x got % x", floatResult, b.Bytes())
+		}
+	}
+
+	// bytes == []uint8
+	{
+		b.Reset()
+		data := []byte("hello")
+		instr := &encInstr{encUint8Array, 6, nil, 0}
+		state := newEncoderState(b)
+		instr.op(instr, state, reflect.ValueOf(data))
+		if !bytes.Equal(bytesResult, b.Bytes()) {
+			t.Errorf("bytes enc instructions: expected % x got % x", bytesResult, b.Bytes())
+		}
+	}
+
+	// string
+	{
+		b.Reset()
+		var data string = "hello"
+		instr := &encInstr{encString, 6, nil, 0}
+		state := newEncoderState(b)
+		instr.op(instr, state, reflect.ValueOf(data))
+		if !bytes.Equal(bytesResult, b.Bytes()) {
+			t.Errorf("string enc instructions: expected % x got % x", bytesResult, b.Bytes())
+		}
+	}
+}
+
+func execDec(instr *decInstr, state *decoderState, t *testing.T, value reflect.Value) {
+	defer testError(t)
+	v := int(state.decodeUint())
+	if v+state.fieldnum != 6 {
+		t.Fatalf("decoding field number %d, got %d", 6, v+state.fieldnum)
+	}
+	instr.op(instr, state, value.Elem())
+	state.fieldnum = 6
+}
+
+func newDecodeStateFromData(data []byte) *decoderState {
+	b := newDecBuffer(data)
+	state := newDecodeState(b)
+	state.fieldnum = -1
+	return state
+}
+
+// Test instruction execution for decoding.
+// Do not run the machine yet; instead do individual instructions crafted by hand.
+func TestScalarDecInstructions(t *testing.T) {
+	ovfl := errors.New("overflow")
+
+	// bool
+	{
+		var data bool
+		instr := &decInstr{decBool, 6, nil, ovfl}
+		state := newDecodeStateFromData(boolResult)
+		execDec(instr, state, t, reflect.ValueOf(&data))
+		if data != true {
+			t.Errorf("bool a = %v not true", data)
+		}
+	}
+	// int
+	{
+		var data int
+		instr := &decInstr{decOpTable[reflect.Int], 6, nil, ovfl}
+		state := newDecodeStateFromData(signedResult)
+		execDec(instr, state, t, reflect.ValueOf(&data))
+		if data != 17 {
+			t.Errorf("int a = %v not 17", data)
+		}
+	}
+
+	// uint
+	{
+		var data uint
+		instr := &decInstr{decOpTable[reflect.Uint], 6, nil, ovfl}
+		state := newDecodeStateFromData(unsignedResult)
+		execDec(instr, state, t, reflect.ValueOf(&data))
+		if data != 17 {
+			t.Errorf("uint a = %v not 17", data)
+		}
+	}
+
+	// int8
+	{
+		var data int8
+		instr := &decInstr{decInt8, 6, nil, ovfl}
+		state := newDecodeStateFromData(signedResult)
+		execDec(instr, state, t, reflect.ValueOf(&data))
+		if data != 17 {
+			t.Errorf("int8 a = %v not 17", data)
+		}
+	}
+
+	// uint8
+	{
+		var data uint8
+		instr := &decInstr{decUint8, 6, nil, ovfl}
+		state := newDecodeStateFromData(unsignedResult)
+		execDec(instr, state, t, reflect.ValueOf(&data))
+		if data != 17 {
+			t.Errorf("uint8 a = %v not 17", data)
+		}
+	}
+
+	// int16
+	{
+		var data int16
+		instr := &decInstr{decInt16, 6, nil, ovfl}
+		state := newDecodeStateFromData(signedResult)
+		execDec(instr, state, t, reflect.ValueOf(&data))
+		if data != 17 {
+			t.Errorf("int16 a = %v not 17", data)
+		}
+	}
+
+	// uint16
+	{
+		var data uint16
+		instr := &decInstr{decUint16, 6, nil, ovfl}
+		state := newDecodeStateFromData(unsignedResult)
+		execDec(instr, state, t, reflect.ValueOf(&data))
+		if data != 17 {
+			t.Errorf("uint16 a = %v not 17", data)
+		}
+	}
+
+	// int32
+	{
+		var data int32
+		instr := &decInstr{decInt32, 6, nil, ovfl}
+		state := newDecodeStateFromData(signedResult)
+		execDec(instr, state, t, reflect.ValueOf(&data))
+		if data != 17 {
+			t.Errorf("int32 a = %v not 17", data)
+		}
+	}
+
+	// uint32
+	{
+		var data uint32
+		instr := &decInstr{decUint32, 6, nil, ovfl}
+		state := newDecodeStateFromData(unsignedResult)
+		execDec(instr, state, t, reflect.ValueOf(&data))
+		if data != 17 {
+			t.Errorf("uint32 a = %v not 17", data)
+		}
+	}
+
+	// uintptr
+	{
+		var data uintptr
+		instr := &decInstr{decOpTable[reflect.Uintptr], 6, nil, ovfl}
+		state := newDecodeStateFromData(unsignedResult)
+		execDec(instr, state, t, reflect.ValueOf(&data))
+		if data != 17 {
+			t.Errorf("uintptr a = %v not 17", data)
+		}
+	}
+
+	// int64
+	{
+		var data int64
+		instr := &decInstr{decInt64, 6, nil, ovfl}
+		state := newDecodeStateFromData(signedResult)
+		execDec(instr, state, t, reflect.ValueOf(&data))
+		if data != 17 {
+			t.Errorf("int64 a = %v not 17", data)
+		}
+	}
+
+	// uint64
+	{
+		var data uint64
+		instr := &decInstr{decUint64, 6, nil, ovfl}
+		state := newDecodeStateFromData(unsignedResult)
+		execDec(instr, state, t, reflect.ValueOf(&data))
+		if data != 17 {
+			t.Errorf("uint64 a = %v not 17", data)
+		}
+	}
+
+	// float32
+	{
+		var data float32
+		instr := &decInstr{decFloat32, 6, nil, ovfl}
+		state := newDecodeStateFromData(floatResult)
+		execDec(instr, state, t, reflect.ValueOf(&data))
+		if data != 17 {
+			t.Errorf("float32 a = %v not 17", data)
+		}
+	}
+
+	// float64
+	{
+		var data float64
+		instr := &decInstr{decFloat64, 6, nil, ovfl}
+		state := newDecodeStateFromData(floatResult)
+		execDec(instr, state, t, reflect.ValueOf(&data))
+		if data != 17 {
+			t.Errorf("float64 a = %v not 17", data)
+		}
+	}
+
+	// complex64
+	{
+		var data complex64
+		instr := &decInstr{decOpTable[reflect.Complex64], 6, nil, ovfl}
+		state := newDecodeStateFromData(complexResult)
+		execDec(instr, state, t, reflect.ValueOf(&data))
+		if data != 17+19i {
+			t.Errorf("complex a = %v not 17+19i", data)
+		}
+	}
+
+	// complex128
+	{
+		var data complex128
+		instr := &decInstr{decOpTable[reflect.Complex128], 6, nil, ovfl}
+		state := newDecodeStateFromData(complexResult)
+		execDec(instr, state, t, reflect.ValueOf(&data))
+		if data != 17+19i {
+			t.Errorf("complex a = %v not 17+19i", data)
+		}
+	}
+
+	// bytes == []uint8
+	{
+		var data []byte
+		instr := &decInstr{decUint8Slice, 6, nil, ovfl}
+		state := newDecodeStateFromData(bytesResult)
+		execDec(instr, state, t, reflect.ValueOf(&data))
+		if string(data) != "hello" {
+			t.Errorf(`bytes a = %q not "hello"`, string(data))
+		}
+	}
+
+	// string
+	{
+		var data string
+		instr := &decInstr{decString, 6, nil, ovfl}
+		state := newDecodeStateFromData(bytesResult)
+		execDec(instr, state, t, reflect.ValueOf(&data))
+		if data != "hello" {
+			t.Errorf(`bytes a = %q not "hello"`, data)
+		}
+	}
+}
+
+func TestEndToEnd(t *testing.T) {
+	type T2 struct {
+		T string
+	}
+	type T3 struct {
+		X float64
+		Z *int
+	}
+	type T1 struct {
+		A, B, C  int
+		M        map[string]*float64
+		M2       map[int]T3
+		Mstring  map[string]string
+		Mintptr  map[int]*int
+		Mcomp    map[complex128]complex128
+		Marr     map[[2]string][2]*float64
+		EmptyMap map[string]int // to check that we receive a non-nil map.
+		N        *[3]float64
+		Strs     *[2]string
+		Int64s   *[]int64
+		RI       complex64
+		S        string
+		Y        []byte
+		T        *T2
+	}
+	pi := 3.14159
+	e := 2.71828
+	two := 2.0
+	meaning := 42
+	fingers := 5
+	s1 := "string1"
+	s2 := "string2"
+	var comp1 complex128 = complex(1.0, 1.0)
+	var comp2 complex128 = complex(1.0, 1.0)
+	var arr1 [2]string
+	arr1[0] = s1
+	arr1[1] = s2
+	var arr2 [2]string
+	arr2[0] = s2
+	arr2[1] = s1
+	var floatArr1 [2]*float64
+	floatArr1[0] = &pi
+	floatArr1[1] = &e
+	var floatArr2 [2]*float64
+	floatArr2[0] = &e
+	floatArr2[1] = &two
+	t1 := &T1{
+		A:        17,
+		B:        18,
+		C:        -5,
+		M:        map[string]*float64{"pi": &pi, "e": &e},
+		M2:       map[int]T3{4: {X: pi, Z: &meaning}, 10: {X: e, Z: &fingers}},
+		Mstring:  map[string]string{"pi": "3.14", "e": "2.71"},
+		Mintptr:  map[int]*int{meaning: &fingers, fingers: &meaning},
+		Mcomp:    map[complex128]complex128{comp1: comp2, comp2: comp1},
+		Marr:     map[[2]string][2]*float64{arr1: floatArr1, arr2: floatArr2},
+		EmptyMap: make(map[string]int),
+		N:        &[3]float64{1.5, 2.5, 3.5},
+		Strs:     &[2]string{s1, s2},
+		Int64s:   &[]int64{77, 89, 123412342134},
+		RI:       17 - 23i,
+		S:        "Now is the time",
+		Y:        []byte("hello, sailor"),
+		T:        &T2{"this is T2"},
+	}
+	b := new(bytes.Buffer)
+	err := NewEncoder(b).Encode(t1)
+	if err != nil {
+		t.Error("encode:", err)
+	}
+	var _t1 T1
+	err = NewDecoder(b).Decode(&_t1)
+	if err != nil {
+		t.Fatal("decode:", err)
+	}
+	if !reflect.DeepEqual(t1, &_t1) {
+		t.Errorf("encode expected %v got %v", *t1, _t1)
+	}
+	// Be absolutely sure the received map is non-nil.
+	if t1.EmptyMap == nil {
+		t.Errorf("nil map sent")
+	}
+	if _t1.EmptyMap == nil {
+		t.Errorf("nil map received")
+	}
+}
+
+func TestOverflow(t *testing.T) {
+	type inputT struct {
+		Maxi int64
+		Mini int64
+		Maxu uint64
+		Maxf float64
+		Minf float64
+		Maxc complex128
+		Minc complex128
+	}
+	var it inputT
+	var err error
+	b := new(bytes.Buffer)
+	enc := NewEncoder(b)
+	dec := NewDecoder(b)
+
+	// int8
+	b.Reset()
+	it = inputT{
+		Maxi: math.MaxInt8 + 1,
+	}
+	type outi8 struct {
+		Maxi int8
+		Mini int8
+	}
+	var o1 outi8
+	enc.Encode(it)
+	err = dec.Decode(&o1)
+	if err == nil || err.Error() != `value for "Maxi" out of range` {
+		t.Error("wrong overflow error for int8:", err)
+	}
+	it = inputT{
+		Mini: math.MinInt8 - 1,
+	}
+	b.Reset()
+	enc.Encode(it)
+	err = dec.Decode(&o1)
+	if err == nil || err.Error() != `value for "Mini" out of range` {
+		t.Error("wrong underflow error for int8:", err)
+	}
+
+	// int16
+	b.Reset()
+	it = inputT{
+		Maxi: math.MaxInt16 + 1,
+	}
+	type outi16 struct {
+		Maxi int16
+		Mini int16
+	}
+	var o2 outi16
+	enc.Encode(it)
+	err = dec.Decode(&o2)
+	if err == nil || err.Error() != `value for "Maxi" out of range` {
+		t.Error("wrong overflow error for int16:", err)
+	}
+	it = inputT{
+		Mini: math.MinInt16 - 1,
+	}
+	b.Reset()
+	enc.Encode(it)
+	err = dec.Decode(&o2)
+	if err == nil || err.Error() != `value for "Mini" out of range` {
+		t.Error("wrong underflow error for int16:", err)
+	}
+
+	// int32
+	b.Reset()
+	it = inputT{
+		Maxi: math.MaxInt32 + 1,
+	}
+	type outi32 struct {
+		Maxi int32
+		Mini int32
+	}
+	var o3 outi32
+	enc.Encode(it)
+	err = dec.Decode(&o3)
+	if err == nil || err.Error() != `value for "Maxi" out of range` {
+		t.Error("wrong overflow error for int32:", err)
+	}
+	it = inputT{
+		Mini: math.MinInt32 - 1,
+	}
+	b.Reset()
+	enc.Encode(it)
+	err = dec.Decode(&o3)
+	if err == nil || err.Error() != `value for "Mini" out of range` {
+		t.Error("wrong underflow error for int32:", err)
+	}
+
+	// uint8
+	b.Reset()
+	it = inputT{
+		Maxu: math.MaxUint8 + 1,
+	}
+	type outu8 struct {
+		Maxu uint8
+	}
+	var o4 outu8
+	enc.Encode(it)
+	err = dec.Decode(&o4)
+	if err == nil || err.Error() != `value for "Maxu" out of range` {
+		t.Error("wrong overflow error for uint8:", err)
+	}
+
+	// uint16
+	b.Reset()
+	it = inputT{
+		Maxu: math.MaxUint16 + 1,
+	}
+	type outu16 struct {
+		Maxu uint16
+	}
+	var o5 outu16
+	enc.Encode(it)
+	err = dec.Decode(&o5)
+	if err == nil || err.Error() != `value for "Maxu" out of range` {
+		t.Error("wrong overflow error for uint16:", err)
+	}
+
+	// uint32
+	b.Reset()
+	it = inputT{
+		Maxu: math.MaxUint32 + 1,
+	}
+	type outu32 struct {
+		Maxu uint32
+	}
+	var o6 outu32
+	enc.Encode(it)
+	err = dec.Decode(&o6)
+	if err == nil || err.Error() != `value for "Maxu" out of range` {
+		t.Error("wrong overflow error for uint32:", err)
+	}
+
+	// float32
+	b.Reset()
+	it = inputT{
+		Maxf: math.MaxFloat32 * 2,
+	}
+	type outf32 struct {
+		Maxf float32
+		Minf float32
+	}
+	var o7 outf32
+	enc.Encode(it)
+	err = dec.Decode(&o7)
+	if err == nil || err.Error() != `value for "Maxf" out of range` {
+		t.Error("wrong overflow error for float32:", err)
+	}
+
+	// complex64
+	b.Reset()
+	it = inputT{
+		Maxc: complex(math.MaxFloat32*2, math.MaxFloat32*2),
+	}
+	type outc64 struct {
+		Maxc complex64
+		Minc complex64
+	}
+	var o8 outc64
+	enc.Encode(it)
+	err = dec.Decode(&o8)
+	if err == nil || err.Error() != `value for "Maxc" out of range` {
+		t.Error("wrong overflow error for complex64:", err)
+	}
+}
+
+func TestNesting(t *testing.T) {
+	type RT struct {
+		A    string
+		Next *RT
+	}
+	rt := new(RT)
+	rt.A = "level1"
+	rt.Next = new(RT)
+	rt.Next.A = "level2"
+	b := new(bytes.Buffer)
+	NewEncoder(b).Encode(rt)
+	var drt RT
+	dec := NewDecoder(b)
+	err := dec.Decode(&drt)
+	if err != nil {
+		t.Fatal("decoder error:", err)
+	}
+	if drt.A != rt.A {
+		t.Errorf("nesting: encode expected %v got %v", *rt, drt)
+	}
+	if drt.Next == nil {
+		t.Errorf("nesting: recursion failed")
+	}
+	if drt.Next.A != rt.Next.A {
+		t.Errorf("nesting: encode expected %v got %v", *rt.Next, *drt.Next)
+	}
+}
+
+// These three structures have the same data with different indirections
+type T0 struct {
+	A int
+	B int
+	C int
+	D int
+}
+type T1 struct {
+	A int
+	B *int
+	C **int
+	D ***int
+}
+type T2 struct {
+	A ***int
+	B **int
+	C *int
+	D int
+}
+
+func TestAutoIndirection(t *testing.T) {
+	// First transfer t1 into t0
+	var t1 T1
+	t1.A = 17
+	t1.B = new(int)
+	*t1.B = 177
+	t1.C = new(*int)
+	*t1.C = new(int)
+	**t1.C = 1777
+	t1.D = new(**int)
+	*t1.D = new(*int)
+	**t1.D = new(int)
+	***t1.D = 17777
+	b := new(bytes.Buffer)
+	enc := NewEncoder(b)
+	enc.Encode(t1)
+	dec := NewDecoder(b)
+	var t0 T0
+	dec.Decode(&t0)
+	if t0.A != 17 || t0.B != 177 || t0.C != 1777 || t0.D != 17777 {
+		t.Errorf("t1->t0: expected {17 177 1777 17777}; got %v", t0)
+	}
+
+	// Now transfer t2 into t0
+	var t2 T2
+	t2.D = 17777
+	t2.C = new(int)
+	*t2.C = 1777
+	t2.B = new(*int)
+	*t2.B = new(int)
+	**t2.B = 177
+	t2.A = new(**int)
+	*t2.A = new(*int)
+	**t2.A = new(int)
+	***t2.A = 17
+	b.Reset()
+	enc.Encode(t2)
+	t0 = T0{}
+	dec.Decode(&t0)
+	if t0.A != 17 || t0.B != 177 || t0.C != 1777 || t0.D != 17777 {
+		t.Errorf("t2->t0 expected {17 177 1777 17777}; got %v", t0)
+	}
+
+	// Now transfer t0 into t1
+	t0 = T0{17, 177, 1777, 17777}
+	b.Reset()
+	enc.Encode(t0)
+	t1 = T1{}
+	dec.Decode(&t1)
+	if t1.A != 17 || *t1.B != 177 || **t1.C != 1777 || ***t1.D != 17777 {
+		t.Errorf("t0->t1 expected {17 177 1777 17777}; got {%d %d %d %d}", t1.A, *t1.B, **t1.C, ***t1.D)
+	}
+
+	// Now transfer t0 into t2
+	b.Reset()
+	enc.Encode(t0)
+	t2 = T2{}
+	dec.Decode(&t2)
+	if ***t2.A != 17 || **t2.B != 177 || *t2.C != 1777 || t2.D != 17777 {
+		t.Errorf("t0->t2 expected {17 177 1777 17777}; got {%d %d %d %d}", ***t2.A, **t2.B, *t2.C, t2.D)
+	}
+
+	// Now do t2 again but without pre-allocated pointers.
+	b.Reset()
+	enc.Encode(t0)
+	***t2.A = 0
+	**t2.B = 0
+	*t2.C = 0
+	t2.D = 0
+	dec.Decode(&t2)
+	if ***t2.A != 17 || **t2.B != 177 || *t2.C != 1777 || t2.D != 17777 {
+		t.Errorf("t0->t2 expected {17 177 1777 17777}; got {%d %d %d %d}", ***t2.A, **t2.B, *t2.C, t2.D)
+	}
+}
+
+type RT0 struct {
+	A int
+	B string
+	C float64
+}
+type RT1 struct {
+	C      float64
+	B      string
+	A      int
+	NotSet string
+}
+
+func TestReorderedFields(t *testing.T) {
+	var rt0 RT0
+	rt0.A = 17
+	rt0.B = "hello"
+	rt0.C = 3.14159
+	b := new(bytes.Buffer)
+	NewEncoder(b).Encode(rt0)
+	dec := NewDecoder(b)
+	var rt1 RT1
+	// Wire type is RT0, local type is RT1.
+	err := dec.Decode(&rt1)
+	if err != nil {
+		t.Fatal("decode error:", err)
+	}
+	if rt0.A != rt1.A || rt0.B != rt1.B || rt0.C != rt1.C {
+		t.Errorf("rt1->rt0: expected %v; got %v", rt0, rt1)
+	}
+}
+
+// Like an RT0 but with fields we'll ignore on the decode side.
+type IT0 struct {
+	A        int64
+	B        string
+	Ignore_d []int
+	Ignore_e [3]float64
+	Ignore_f bool
+	Ignore_g string
+	Ignore_h []byte
+	Ignore_i *RT1
+	Ignore_m map[string]int
+	C        float64
+}
+
+func TestIgnoredFields(t *testing.T) {
+	var it0 IT0
+	it0.A = 17
+	it0.B = "hello"
+	it0.C = 3.14159
+	it0.Ignore_d = []int{1, 2, 3}
+	it0.Ignore_e[0] = 1.0
+	it0.Ignore_e[1] = 2.0
+	it0.Ignore_e[2] = 3.0
+	it0.Ignore_f = true
+	it0.Ignore_g = "pay no attention"
+	it0.Ignore_h = []byte("to the curtain")
+	it0.Ignore_i = &RT1{3.1, "hi", 7, "hello"}
+	it0.Ignore_m = map[string]int{"one": 1, "two": 2}
+
+	b := new(bytes.Buffer)
+	NewEncoder(b).Encode(it0)
+	dec := NewDecoder(b)
+	var rt1 RT1
+	// Wire type is IT0, local type is RT1.
+	err := dec.Decode(&rt1)
+	if err != nil {
+		t.Error("error: ", err)
+	}
+	if int(it0.A) != rt1.A || it0.B != rt1.B || it0.C != rt1.C {
+		t.Errorf("rt0->rt1: expected %v; got %v", it0, rt1)
+	}
+}
+
+func TestBadRecursiveType(t *testing.T) {
+	type Rec ***Rec
+	var rec Rec
+	b := new(bytes.Buffer)
+	err := NewEncoder(b).Encode(&rec)
+	if err == nil {
+		t.Error("expected error; got none")
+	} else if !strings.Contains(err.Error(), "recursive") {
+		t.Error("expected recursive type error; got", err)
+	}
+	// Can't test decode easily because we can't encode one, so we can't pass one to a Decoder.
+}
+
+type Indirect struct {
+	A ***[3]int
+	S ***[]int
+	M ****map[string]int
+}
+
+type Direct struct {
+	A [3]int
+	S []int
+	M map[string]int
+}
+
+func TestIndirectSliceMapArray(t *testing.T) {
+	// Marshal indirect, unmarshal to direct.
+	i := new(Indirect)
+	i.A = new(**[3]int)
+	*i.A = new(*[3]int)
+	**i.A = new([3]int)
+	***i.A = [3]int{1, 2, 3}
+	i.S = new(**[]int)
+	*i.S = new(*[]int)
+	**i.S = new([]int)
+	***i.S = []int{4, 5, 6}
+	i.M = new(***map[string]int)
+	*i.M = new(**map[string]int)
+	**i.M = new(*map[string]int)
+	***i.M = new(map[string]int)
+	****i.M = map[string]int{"one": 1, "two": 2, "three": 3}
+	b := new(bytes.Buffer)
+	NewEncoder(b).Encode(i)
+	dec := NewDecoder(b)
+	var d Direct
+	err := dec.Decode(&d)
+	if err != nil {
+		t.Error("error: ", err)
+	}
+	if len(d.A) != 3 || d.A[0] != 1 || d.A[1] != 2 || d.A[2] != 3 {
+		t.Errorf("indirect to direct: d.A is %v not %v", d.A, ***i.A)
+	}
+	if len(d.S) != 3 || d.S[0] != 4 || d.S[1] != 5 || d.S[2] != 6 {
+		t.Errorf("indirect to direct: d.S is %v not %v", d.S, ***i.S)
+	}
+	if len(d.M) != 3 || d.M["one"] != 1 || d.M["two"] != 2 || d.M["three"] != 3 {
+		t.Errorf("indirect to direct: d.M is %v not %v", d.M, ***i.M)
+	}
+	// Marshal direct, unmarshal to indirect.
+	d.A = [3]int{11, 22, 33}
+	d.S = []int{44, 55, 66}
+	d.M = map[string]int{"four": 4, "five": 5, "six": 6}
+	i = new(Indirect)
+	b.Reset()
+	NewEncoder(b).Encode(d)
+	dec = NewDecoder(b)
+	err = dec.Decode(&i)
+	if err != nil {
+		t.Fatal("error: ", err)
+	}
+	if len(***i.A) != 3 || (***i.A)[0] != 11 || (***i.A)[1] != 22 || (***i.A)[2] != 33 {
+		t.Errorf("direct to indirect: ***i.A is %v not %v", ***i.A, d.A)
+	}
+	if len(***i.S) != 3 || (***i.S)[0] != 44 || (***i.S)[1] != 55 || (***i.S)[2] != 66 {
+		t.Errorf("direct to indirect: ***i.S is %v not %v", ***i.S, ***i.S)
+	}
+	if len(****i.M) != 3 || (****i.M)["four"] != 4 || (****i.M)["five"] != 5 || (****i.M)["six"] != 6 {
+		t.Errorf("direct to indirect: ****i.M is %v not %v", ****i.M, d.M)
+	}
+}
+
+// An interface with several implementations
+type Squarer interface {
+	Square() int
+}
+
+type Int int
+
+func (i Int) Square() int {
+	return int(i * i)
+}
+
+type Float float64
+
+func (f Float) Square() int {
+	return int(f * f)
+}
+
+type Vector []int
+
+func (v Vector) Square() int {
+	sum := 0
+	for _, x := range v {
+		sum += x * x
+	}
+	return sum
+}
+
+type Point struct {
+	X, Y int
+}
+
+func (p Point) Square() int {
+	return p.X*p.X + p.Y*p.Y
+}
+
+// A struct with interfaces in it.
+type InterfaceItem struct {
+	I             int
+	Sq1, Sq2, Sq3 Squarer
+	F             float64
+	Sq            []Squarer
+}
+
+// The same struct without interfaces
+type NoInterfaceItem struct {
+	I int
+	F float64
+}
+
+func TestInterface(t *testing.T) {
+	iVal := Int(3)
+	fVal := Float(5)
+	// Sending a Vector will require that the receiver define a type in the middle of
+	// receiving the value for item2.
+	vVal := Vector{1, 2, 3}
+	b := new(bytes.Buffer)
+	item1 := &InterfaceItem{1, iVal, fVal, vVal, 11.5, []Squarer{iVal, fVal, nil, vVal}}
+	// Register the types.
+	Register(Int(0))
+	Register(Float(0))
+	Register(Vector{})
+	err := NewEncoder(b).Encode(item1)
+	if err != nil {
+		t.Error("expected no encode error; got", err)
+	}
+
+	item2 := InterfaceItem{}
+	err = NewDecoder(b).Decode(&item2)
+	if err != nil {
+		t.Fatal("decode:", err)
+	}
+	if item2.I != item1.I {
+		t.Error("normal int did not decode correctly")
+	}
+	if item2.Sq1 == nil || item2.Sq1.Square() != iVal.Square() {
+		t.Error("Int did not decode correctly")
+	}
+	if item2.Sq2 == nil || item2.Sq2.Square() != fVal.Square() {
+		t.Error("Float did not decode correctly")
+	}
+	if item2.Sq3 == nil || item2.Sq3.Square() != vVal.Square() {
+		t.Error("Vector did not decode correctly")
+	}
+	if item2.F != item1.F {
+		t.Error("normal float did not decode correctly")
+	}
+	// Now check that we received a slice of Squarers correctly, including a nil element
+	if len(item1.Sq) != len(item2.Sq) {
+		t.Fatalf("[]Squarer length wrong: got %d; expected %d", len(item2.Sq), len(item1.Sq))
+	}
+	for i, v1 := range item1.Sq {
+		v2 := item2.Sq[i]
+		if v1 == nil || v2 == nil {
+			if v1 != nil || v2 != nil {
+				t.Errorf("item %d inconsistent nils", i)
+			}
+		} else if v1.Square() != v2.Square() {
+			t.Errorf("item %d inconsistent values: %v %v", i, v1, v2)
+		}
+	}
+}
+
+// A struct with all basic types, stored in interfaces.
+type BasicInterfaceItem struct {
+	Int, Int8, Int16, Int32, Int64      any
+	Uint, Uint8, Uint16, Uint32, Uint64 any
+	Float32, Float64                    any
+	Complex64, Complex128               any
+	Bool                                any
+	String                              any
+	Bytes                               any
+}
+
+func TestInterfaceBasic(t *testing.T) {
+	b := new(bytes.Buffer)
+	item1 := &BasicInterfaceItem{
+		int(1), int8(1), int16(1), int32(1), int64(1),
+		uint(1), uint8(1), uint16(1), uint32(1), uint64(1),
+		float32(1), 1.0,
+		complex64(1i), complex128(1i),
+		true,
+		"hello",
+		[]byte("sailor"),
+	}
+	err := NewEncoder(b).Encode(item1)
+	if err != nil {
+		t.Error("expected no encode error; got", err)
+	}
+
+	item2 := &BasicInterfaceItem{}
+	err = NewDecoder(b).Decode(&item2)
+	if err != nil {
+		t.Fatal("decode:", err)
+	}
+	if !reflect.DeepEqual(item1, item2) {
+		t.Errorf("encode expected %v got %v", item1, item2)
+	}
+	// Hand check a couple for correct types.
+	if v, ok := item2.Bool.(bool); !ok || !v {
+		t.Error("boolean should be true")
+	}
+	if v, ok := item2.String.(string); !ok || v != item1.String.(string) {
+		t.Errorf("string should be %v is %v", item1.String, v)
+	}
+}
+
+type String string
+
+type PtrInterfaceItem struct {
+	Str1 any // basic
+	Str2 any // derived
+}
+
+// We'll send pointers; should receive values.
+// Also check that we can register T but send *T.
+func TestInterfacePointer(t *testing.T) {
+	b := new(bytes.Buffer)
+	str1 := "howdy"
+	str2 := String("kiddo")
+	item1 := &PtrInterfaceItem{
+		&str1,
+		&str2,
+	}
+	// Register the type.
+	Register(str2)
+	err := NewEncoder(b).Encode(item1)
+	if err != nil {
+		t.Error("expected no encode error; got", err)
+	}
+
+	item2 := &PtrInterfaceItem{}
+	err = NewDecoder(b).Decode(&item2)
+	if err != nil {
+		t.Fatal("decode:", err)
+	}
+	// Hand test for correct types and values.
+	if v, ok := item2.Str1.(string); !ok || v != str1 {
+		t.Errorf("basic string failed: %q should be %q", v, str1)
+	}
+	if v, ok := item2.Str2.(String); !ok || v != str2 {
+		t.Errorf("derived type String failed: %q should be %q", v, str2)
+	}
+}
+
+func TestIgnoreInterface(t *testing.T) {
+	iVal := Int(3)
+	fVal := Float(5)
+	// Sending a Point will require that the receiver define a type in the middle of
+	// receiving the value for item2.
+	pVal := Point{2, 3}
+	b := new(bytes.Buffer)
+	item1 := &InterfaceItem{1, iVal, fVal, pVal, 11.5, nil}
+	// Register the types.
+	Register(Int(0))
+	Register(Float(0))
+	Register(Point{})
+	err := NewEncoder(b).Encode(item1)
+	if err != nil {
+		t.Error("expected no encode error; got", err)
+	}
+
+	item2 := NoInterfaceItem{}
+	err = NewDecoder(b).Decode(&item2)
+	if err != nil {
+		t.Fatal("decode:", err)
+	}
+	if item2.I != item1.I {
+		t.Error("normal int did not decode correctly")
+	}
+	if item2.F != item1.F {
+		t.Error("normal float did not decode correctly")
+	}
+}
+
+type U struct {
+	A int
+	B string
+	c float64
+	D uint
+}
+
+func TestUnexportedFields(t *testing.T) {
+	var u0 U
+	u0.A = 17
+	u0.B = "hello"
+	u0.c = 3.14159
+	u0.D = 23
+	b := new(bytes.Buffer)
+	NewEncoder(b).Encode(u0)
+	dec := NewDecoder(b)
+	var u1 U
+	u1.c = 1234.
+	err := dec.Decode(&u1)
+	if err != nil {
+		t.Fatal("decode error:", err)
+	}
+	if u0.A != u1.A || u0.B != u1.B || u0.D != u1.D {
+		t.Errorf("u1->u0: expected %v; got %v", u0, u1)
+	}
+	if u1.c != 1234. {
+		t.Error("u1.c modified")
+	}
+}
+
+var singletons = []any{
+	true,
+	7,
+	uint(10),
+	3.2,
+	"hello",
+	[3]int{11, 22, 33},
+	[]float32{0.5, 0.25, 0.125},
+	map[string]int{"one": 1, "two": 2},
+}
+
+func TestDebugSingleton(t *testing.T) {
+	if debugFunc == nil {
+		return
+	}
+	b := new(bytes.Buffer)
+	// Accumulate a number of values and print them out all at once.
+	for _, x := range singletons {
+		err := NewEncoder(b).Encode(x)
+		if err != nil {
+			t.Fatal("encode:", err)
+		}
+	}
+	debugFunc(b)
+}
+
+// A type that won't be defined in the gob until we send it in an interface value.
+type OnTheFly struct {
+	A int
+}
+
+type DT struct {
+	//	X OnTheFly
+	A     int
+	B     string
+	C     float64
+	I     any
+	J     any
+	I_nil any
+	M     map[string]int
+	T     [3]int
+	S     []string
+}
+
+func newDT() DT {
+	var dt DT
+	dt.A = 17
+	dt.B = "hello"
+	dt.C = 3.14159
+	dt.I = 271828
+	dt.J = OnTheFly{3}
+	dt.I_nil = nil
+	dt.M = map[string]int{"one": 1, "two": 2}
+	dt.T = [3]int{11, 22, 33}
+	dt.S = []string{"hi", "joe"}
+	return dt
+}
+
+func TestDebugStruct(t *testing.T) {
+	if debugFunc == nil {
+		return
+	}
+	Register(OnTheFly{})
+	dt := newDT()
+	b := new(bytes.Buffer)
+	err := NewEncoder(b).Encode(dt)
+	if err != nil {
+		t.Fatal("encode:", err)
+	}
+	debugBuffer := bytes.NewBuffer(b.Bytes())
+	dt2 := &DT{}
+	err = NewDecoder(b).Decode(&dt2)
+	if err != nil {
+		t.Error("decode:", err)
+	}
+	debugFunc(debugBuffer)
+}
+
+func encFuzzDec(rng *rand.Rand, in any) error {
+	buf := new(bytes.Buffer)
+	enc := NewEncoder(buf)
+	if err := enc.Encode(&in); err != nil {
+		return err
+	}
+
+	b := buf.Bytes()
+	for i, bi := range b {
+		if rng.Intn(10) < 3 {
+			b[i] = bi + uint8(rng.Intn(256))
+		}
+	}
+
+	dec := NewDecoder(buf)
+	var e any
+	if err := dec.Decode(&e); err != nil {
+		return err
+	}
+	return nil
+}
+
+// This does some "fuzz testing" by attempting to decode a sequence of random bytes.
+func TestFuzz(t *testing.T) {
+	if !*doFuzzTests {
+		t.Skipf("disabled; run with -gob.fuzz to enable")
+	}
+
+	// all possible inputs
+	input := []any{
+		new(int),
+		new(float32),
+		new(float64),
+		new(complex128),
+		&ByteStruct{255},
+		&ArrayStruct{},
+		&StringStruct{"hello"},
+		&GobTest1{0, &StringStruct{"hello"}},
+	}
+	testFuzz(t, time.Now().UnixNano(), 100, input...)
+}
+
+func TestFuzzRegressions(t *testing.T) {
+	if !*doFuzzTests {
+		t.Skipf("disabled; run with -gob.fuzz to enable")
+	}
+
+	// An instance triggering a type name of length ~102 GB.
+	testFuzz(t, 1328492090837718000, 100, new(float32))
+	// An instance triggering a type name of 1.6 GB.
+	// Note: can take several minutes to run.
+	testFuzz(t, 1330522872628565000, 100, new(int))
+}
+
+func testFuzz(t *testing.T, seed int64, n int, input ...any) {
+	for _, e := range input {
+		t.Logf("seed=%d n=%d e=%T", seed, n, e)
+		rng := rand.New(rand.NewSource(seed))
+		for i := 0; i < n; i++ {
+			encFuzzDec(rng, e)
+		}
+	}
+}
+
+// TestFuzzOneByte tries to decode corrupted input sequences
+// and checks that no panic occurs.
+func TestFuzzOneByte(t *testing.T) {
+	if !*doFuzzTests {
+		t.Skipf("disabled; run with -gob.fuzz to enable")
+	}
+
+	buf := new(bytes.Buffer)
+	Register(OnTheFly{})
+	dt := newDT()
+	if err := NewEncoder(buf).Encode(dt); err != nil {
+		t.Fatal(err)
+	}
+	s := buf.String()
+
+	indices := make([]int, 0, len(s))
+	for i := 0; i < len(s); i++ {
+		switch i {
+		case 14, 167, 231, 265: // a slice length, corruptions are not handled yet.
+			continue
+		case 248:
+			// Large map size, which currently causes an out of memory panic.
+			// See golang.org/issue/24308 and golang.org/issue/20221.
+			continue
+		}
+		indices = append(indices, i)
+	}
+	if testing.Short() {
+		indices = []int{1, 111, 178} // known fixed panics
+	}
+	for _, i := range indices {
+		for j := 0; j < 256; j += 3 {
+			b := []byte(s)
+			b[i] ^= byte(j)
+			var e DT
+			func() {
+				defer func() {
+					if p := recover(); p != nil {
+						t.Errorf("crash for b[%d] ^= 0x%x", i, j)
+						panic(p)
+					}
+				}()
+				err := NewDecoder(bytes.NewReader(b)).Decode(&e)
+				_ = err
+			}()
+		}
+	}
+}
+
+// Don't crash, just give error with invalid type id.
+// Issue 9649.
+func TestErrorInvalidTypeId(t *testing.T) {
+	data := []byte{0x01, 0x00, 0x01, 0x00}
+	d := NewDecoder(bytes.NewReader(data))
+	// When running d.Decode(&foo) the first time the decoder stops
+	// after []byte{0x01, 0x00} and reports an errBadType. Running
+	// d.Decode(&foo) again on exactly the same input sequence should
+	// give another errBadType, but instead caused a panic because
+	// decoderMap wasn't cleaned up properly after the first error.
+	for i := 0; i < 2; i++ {
+		var foo struct{}
+		err := d.Decode(&foo)
+		if err != errBadType {
+			t.Fatalf("decode: expected %s, got %s", errBadType, err)
+		}
+	}
+}
diff --git a/src/encoding/gob/debug.go b/src/encoding/gob/debug.go
new file mode 100644
index 0000000..b6d5a3e
--- /dev/null
+++ b/src/encoding/gob/debug.go
@@ -0,0 +1,705 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Delete the next line to include in the gob package.
+//go:build ignore
+
+package gob
+
+// This file is not normally included in the gob package. Used only for debugging the package itself.
+// Except for reading uints, it is an implementation of a reader that is independent of
+// the one implemented by Decoder.
+// To enable the Debug function, delete the +build ignore line above and do
+//	go install
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"os"
+	"strings"
+	"sync"
+)
+
+var dumpBytes = false // If true, print the remaining bytes in the input buffer at each item.
+
+// Init installs the debugging facility. If this file is not compiled in the
+// package, the tests in codec_test.go are no-ops.
+func init() {
+	debugFunc = Debug
+}
+
+var (
+	blanks = bytes.Repeat([]byte{' '}, 3*10)
+	empty  = []byte(": <empty>\n")
+	tabs   = strings.Repeat("\t", 100)
+)
+
+// tab indents itself when printed.
+type tab int
+
+func (t tab) String() string {
+	n := int(t)
+	if n > len(tabs) {
+		n = len(tabs)
+	}
+	return tabs[0:n]
+}
+
+func (t tab) print() {
+	fmt.Fprint(os.Stderr, t)
+}
+
+// A peekReader wraps an io.Reader, allowing one to peek ahead to see
+// what's coming without stealing the data from the client of the Reader.
+type peekReader struct {
+	r    io.Reader
+	data []byte // read-ahead data
+}
+
+// newPeekReader returns a peekReader that wraps r.
+func newPeekReader(r io.Reader) *peekReader {
+	return &peekReader{r: r}
+}
+
+// Read is the usual method. It will first take data that has been read ahead.
+func (p *peekReader) Read(b []byte) (n int, err error) {
+	if len(p.data) == 0 {
+		return p.r.Read(b)
+	}
+	// Satisfy what's possible from the read-ahead data.
+	n = copy(b, p.data)
+	// Move data down to beginning of slice, to avoid endless growth
+	copy(p.data, p.data[n:])
+	p.data = p.data[:len(p.data)-n]
+	return
+}
+
+// peek returns as many bytes as possible from the unread
+// portion of the stream, up to the length of b.
+func (p *peekReader) peek(b []byte) (n int, err error) {
+	if len(p.data) > 0 {
+		n = copy(b, p.data)
+		if n == len(b) {
+			return
+		}
+		b = b[n:]
+	}
+	if len(b) == 0 {
+		return
+	}
+	m, e := io.ReadFull(p.r, b)
+	if m > 0 {
+		p.data = append(p.data, b[:m]...)
+	}
+	n += m
+	if e == io.ErrUnexpectedEOF {
+		// That means m > 0 but we reached EOF. If we got data
+		// we won't complain about not being able to peek enough.
+		if n > 0 {
+			e = nil
+		} else {
+			e = io.EOF
+		}
+	}
+	return n, e
+}
+
+type debugger struct {
+	mutex          sync.Mutex
+	remain         int  // the number of bytes known to remain in the input
+	remainingKnown bool // the value of 'remain' is valid
+	r              *peekReader
+	wireType       map[typeId]*wireType
+	tmp            []byte // scratch space for decoding uints.
+}
+
+// dump prints the next nBytes of the input.
+// It arranges to print the output aligned from call to
+// call, to make it easy to see what has been consumed.
+func (deb *debugger) dump(format string, args ...any) {
+	if !dumpBytes {
+		return
+	}
+	fmt.Fprintf(os.Stderr, format+" ", args...)
+	if !deb.remainingKnown {
+		return
+	}
+	if deb.remain < 0 {
+		fmt.Fprintf(os.Stderr, "remaining byte count is negative! %d\n", deb.remain)
+		return
+	}
+	data := make([]byte, deb.remain)
+	n, _ := deb.r.peek(data)
+	if n == 0 {
+		os.Stderr.Write(empty)
+		return
+	}
+	b := new(bytes.Buffer)
+	fmt.Fprintf(b, "[%d]{\n", deb.remain)
+	// Blanks until first byte
+	lineLength := 0
+	if n := len(data); n%10 != 0 {
+		lineLength = 10 - n%10
+		fmt.Fprintf(b, "\t%s", blanks[:lineLength*3])
+	}
+	// 10 bytes per line
+	for len(data) > 0 {
+		if lineLength == 0 {
+			fmt.Fprint(b, "\t")
+		}
+		m := 10 - lineLength
+		lineLength = 0
+		if m > len(data) {
+			m = len(data)
+		}
+		fmt.Fprintf(b, "% x\n", data[:m])
+		data = data[m:]
+	}
+	fmt.Fprint(b, "}\n")
+	os.Stderr.Write(b.Bytes())
+}
+
+// Debug prints a human-readable representation of the gob data read from r.
+// It is a no-op unless debugging was enabled when the package was built.
+func Debug(r io.Reader) {
+	err := debug(r)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "gob debug: %s\n", err)
+	}
+}
+
+// debug implements Debug, but catches panics and returns
+// them as errors to be printed by Debug.
+func debug(r io.Reader) (err error) {
+	defer catchError(&err)
+	fmt.Fprintln(os.Stderr, "Start of debugging")
+	deb := &debugger{
+		r:        newPeekReader(r),
+		wireType: make(map[typeId]*wireType),
+		tmp:      make([]byte, 16),
+	}
+	if b, ok := r.(*bytes.Buffer); ok {
+		deb.remain = b.Len()
+		deb.remainingKnown = true
+	}
+	deb.gobStream()
+	return
+}
+
+// note that we've consumed some bytes
+func (deb *debugger) consumed(n int) {
+	if deb.remainingKnown {
+		deb.remain -= n
+	}
+}
+
+// int64 decodes and returns the next integer, which must be present.
+// Don't call this if you could be at EOF.
+func (deb *debugger) int64() int64 {
+	return toInt(deb.uint64())
+}
+
+// uint64 returns and decodes the next unsigned integer, which must be present.
+// Don't call this if you could be at EOF.
+// TODO: handle errors better.
+func (deb *debugger) uint64() uint64 {
+	n, w, err := decodeUintReader(deb.r, deb.tmp)
+	if err != nil {
+		errorf("debug: read error: %s", err)
+	}
+	deb.consumed(w)
+	return n
+}
+
+// GobStream:
+//	DelimitedMessage* (until EOF)
+func (deb *debugger) gobStream() {
+	// Make sure we're single-threaded through here.
+	deb.mutex.Lock()
+	defer deb.mutex.Unlock()
+
+	for deb.delimitedMessage(0) {
+	}
+}
+
+// DelimitedMessage:
+//	uint(lengthOfMessage) Message
+func (deb *debugger) delimitedMessage(indent tab) bool {
+	for {
+		n := deb.loadBlock(true)
+		if n < 0 {
+			return false
+		}
+		deb.dump("Delimited message of length %d", n)
+		deb.message(indent)
+	}
+	return true
+}
+
+// loadBlock preps us to read a message
+// of the length specified next in the input. It returns
+// the length of the block. The argument tells whether
+// an EOF is acceptable now. If it is and one is found,
+// the return value is negative.
+func (deb *debugger) loadBlock(eofOK bool) int {
+	n64, w, err := decodeUintReader(deb.r, deb.tmp) // deb.uint64 will error at EOF
+	if err != nil {
+		if eofOK && err == io.EOF {
+			return -1
+		}
+		errorf("debug: unexpected error: %s", err)
+	}
+	deb.consumed(w)
+	n := int(n64)
+	if n < 0 {
+		errorf("huge value for message length: %d", n64)
+	}
+	return int(n)
+}
+
+// Message:
+//	TypeSequence TypedValue
+// TypeSequence
+//	(TypeDefinition DelimitedTypeDefinition*)?
+// DelimitedTypeDefinition:
+//	uint(lengthOfTypeDefinition) TypeDefinition
+// TypedValue:
+//	int(typeId) Value
+func (deb *debugger) message(indent tab) bool {
+	for {
+		// Convert the uint64 to a signed integer typeId
+		uid := deb.int64()
+		id := typeId(uid)
+		deb.dump("type id=%d", id)
+		if id < 0 {
+			deb.typeDefinition(indent, -id)
+			n := deb.loadBlock(false)
+			deb.dump("Message of length %d", n)
+			continue
+		} else {
+			deb.value(indent, id)
+			break
+		}
+	}
+	return true
+}
+
+// Helper methods to make it easy to scan a type descriptor.
+
+// common returns the CommonType at the input point.
+func (deb *debugger) common() CommonType {
+	fieldNum := -1
+	name := ""
+	id := typeId(0)
+	for {
+		delta := deb.delta(-1)
+		if delta == 0 {
+			break
+		}
+		fieldNum += delta
+		switch fieldNum {
+		case 0:
+			name = deb.string()
+		case 1:
+			// Id typeId
+			id = deb.typeId()
+		default:
+			errorf("corrupted CommonType, delta is %d fieldNum is %d", delta, fieldNum)
+		}
+	}
+	return CommonType{name, id}
+}
+
+// uint returns the unsigned int at the input point, as a uint (not uint64).
+func (deb *debugger) uint() uint {
+	return uint(deb.uint64())
+}
+
+// int returns the signed int at the input point, as an int (not int64).
+func (deb *debugger) int() int {
+	return int(deb.int64())
+}
+
+// typeId returns the type id at the input point.
+func (deb *debugger) typeId() typeId {
+	return typeId(deb.int64())
+}
+
+// string returns the string at the input point.
+func (deb *debugger) string() string {
+	x := int(deb.uint64())
+	b := make([]byte, x)
+	nb, _ := deb.r.Read(b)
+	if nb != x {
+		errorf("corrupted type")
+	}
+	deb.consumed(nb)
+	return string(b)
+}
+
+// delta returns the field delta at the input point. The expect argument,
+// if non-negative, identifies what the value should be.
+func (deb *debugger) delta(expect int) int {
+	delta := int(deb.uint64())
+	if delta < 0 || (expect >= 0 && delta != expect) {
+		errorf("decode: corrupted type: delta %d expected %d", delta, expect)
+	}
+	return delta
+}
+
+// TypeDefinition:
+//	[int(-typeId) (already read)] encodingOfWireType
+func (deb *debugger) typeDefinition(indent tab, id typeId) {
+	deb.dump("type definition for id %d", id)
+	// Encoding is of a wireType. Decode the structure as usual
+	fieldNum := -1
+	wire := new(wireType)
+	// A wireType defines a single field.
+	delta := deb.delta(-1)
+	fieldNum += delta
+	switch fieldNum {
+	case 0: // array type, one field of {{Common}, elem, length}
+		// Field number 0 is CommonType
+		deb.delta(1)
+		com := deb.common()
+		// Field number 1 is type Id of elem
+		deb.delta(1)
+		id := deb.typeId()
+		// Field number 3 is length
+		deb.delta(1)
+		length := deb.int()
+		wire.ArrayT = &arrayType{com, id, length}
+
+	case 1: // slice type, one field of {{Common}, elem}
+		// Field number 0 is CommonType
+		deb.delta(1)
+		com := deb.common()
+		// Field number 1 is type Id of elem
+		deb.delta(1)
+		id := deb.typeId()
+		wire.SliceT = &sliceType{com, id}
+
+	case 2: // struct type, one field of {{Common}, []fieldType}
+		// Field number 0 is CommonType
+		deb.delta(1)
+		com := deb.common()
+		// Field number 1 is slice of FieldType
+		deb.delta(1)
+		numField := int(deb.uint())
+		field := make([]*fieldType, numField)
+		for i := 0; i < numField; i++ {
+			field[i] = new(fieldType)
+			deb.delta(1) // field 0 of fieldType: name
+			field[i].Name = deb.string()
+			deb.delta(1) // field 1 of fieldType: id
+			field[i].Id = deb.typeId()
+			deb.delta(0) // end of fieldType
+		}
+		wire.StructT = &structType{com, field}
+
+	case 3: // map type, one field of {{Common}, key, elem}
+		// Field number 0 is CommonType
+		deb.delta(1)
+		com := deb.common()
+		// Field number 1 is type Id of key
+		deb.delta(1)
+		keyId := deb.typeId()
+		// Field number 2 is type Id of elem
+		deb.delta(1)
+		elemId := deb.typeId()
+		wire.MapT = &mapType{com, keyId, elemId}
+	case 4: // GobEncoder type, one field of {{Common}}
+		// Field number 0 is CommonType
+		deb.delta(1)
+		com := deb.common()
+		wire.GobEncoderT = &gobEncoderType{com}
+	case 5: // BinaryMarshaler type, one field of {{Common}}
+		// Field number 0 is CommonType
+		deb.delta(1)
+		com := deb.common()
+		wire.BinaryMarshalerT = &gobEncoderType{com}
+	case 6: // TextMarshaler type, one field of {{Common}}
+		// Field number 0 is CommonType
+		deb.delta(1)
+		com := deb.common()
+		wire.TextMarshalerT = &gobEncoderType{com}
+	default:
+		errorf("bad field in type %d", fieldNum)
+	}
+	deb.printWireType(indent, wire)
+	deb.delta(0) // end inner type (arrayType, etc.)
+	deb.delta(0) // end wireType
+	// Remember we've seen this type.
+	deb.wireType[id] = wire
+}
+
+// Value:
+//	SingletonValue | StructValue
+func (deb *debugger) value(indent tab, id typeId) {
+	wire, ok := deb.wireType[id]
+	if ok && wire.StructT != nil {
+		deb.structValue(indent, id)
+	} else {
+		deb.singletonValue(indent, id)
+	}
+}
+
+// SingletonValue:
+//	uint(0) FieldValue
+func (deb *debugger) singletonValue(indent tab, id typeId) {
+	deb.dump("Singleton value")
+	// is it a builtin type?
+	wire := deb.wireType[id]
+	_, ok := builtinIdToType[id]
+	if !ok && wire == nil {
+		errorf("type id %d not defined", id)
+	}
+	m := deb.uint64()
+	if m != 0 {
+		errorf("expected zero; got %d", m)
+	}
+	deb.fieldValue(indent, id)
+}
+
+// InterfaceValue:
+//	NilInterfaceValue | NonNilInterfaceValue
+func (deb *debugger) interfaceValue(indent tab) {
+	deb.dump("Start of interface value")
+	if nameLen := deb.uint64(); nameLen == 0 {
+		deb.nilInterfaceValue(indent)
+	} else {
+		deb.nonNilInterfaceValue(indent, int(nameLen))
+	}
+}
+
+// NilInterfaceValue:
+//	uint(0) [already read]
+func (deb *debugger) nilInterfaceValue(indent tab) int {
+	fmt.Fprintf(os.Stderr, "%snil interface\n", indent)
+	return 0
+}
+
+// NonNilInterfaceValue:
+//	ConcreteTypeName TypeSequence InterfaceContents
+// ConcreteTypeName:
+//	uint(lengthOfName) [already read=n] name
+// InterfaceContents:
+//	int(concreteTypeId) DelimitedValue
+// DelimitedValue:
+//	uint(length) Value
+func (deb *debugger) nonNilInterfaceValue(indent tab, nameLen int) {
+	// ConcreteTypeName
+	b := make([]byte, nameLen)
+	deb.r.Read(b) // TODO: CHECK THESE READS!!
+	deb.consumed(nameLen)
+	name := string(b)
+
+	for {
+		id := deb.typeId()
+		if id < 0 {
+			deb.typeDefinition(indent, -id)
+			n := deb.loadBlock(false)
+			deb.dump("Nested message of length %d", n)
+		} else {
+			// DelimitedValue
+			x := deb.uint64() // in case we want to ignore the value; we don't.
+			fmt.Fprintf(os.Stderr, "%sinterface value, type %q id=%d; valueLength %d\n", indent, name, id, x)
+			deb.value(indent, id)
+			break
+		}
+	}
+}
+
+// printCommonType prints a common type; used by printWireType.
+func (deb *debugger) printCommonType(indent tab, kind string, common *CommonType) {
+	indent.print()
+	fmt.Fprintf(os.Stderr, "%s %q id=%d\n", kind, common.Name, common.Id)
+}
+
+// printWireType prints the contents of a wireType.
+func (deb *debugger) printWireType(indent tab, wire *wireType) {
+	fmt.Fprintf(os.Stderr, "%stype definition {\n", indent)
+	indent++
+	switch {
+	case wire.ArrayT != nil:
+		deb.printCommonType(indent, "array", &wire.ArrayT.CommonType)
+		fmt.Fprintf(os.Stderr, "%slen %d\n", indent+1, wire.ArrayT.Len)
+		fmt.Fprintf(os.Stderr, "%selemid %d\n", indent+1, wire.ArrayT.Elem)
+	case wire.MapT != nil:
+		deb.printCommonType(indent, "map", &wire.MapT.CommonType)
+		fmt.Fprintf(os.Stderr, "%skey id=%d\n", indent+1, wire.MapT.Key)
+		fmt.Fprintf(os.Stderr, "%selem id=%d\n", indent+1, wire.MapT.Elem)
+	case wire.SliceT != nil:
+		deb.printCommonType(indent, "slice", &wire.SliceT.CommonType)
+		fmt.Fprintf(os.Stderr, "%selem id=%d\n", indent+1, wire.SliceT.Elem)
+	case wire.StructT != nil:
+		deb.printCommonType(indent, "struct", &wire.StructT.CommonType)
+		for i, field := range wire.StructT.Field {
+			fmt.Fprintf(os.Stderr, "%sfield %d:\t%s\tid=%d\n", indent+1, i, field.Name, field.Id)
+		}
+	case wire.GobEncoderT != nil:
+		deb.printCommonType(indent, "GobEncoder", &wire.GobEncoderT.CommonType)
+	}
+	indent--
+	fmt.Fprintf(os.Stderr, "%s}\n", indent)
+}
+
+// fieldValue prints a value of any type, such as a struct field.
+// FieldValue:
+//	builtinValue | ArrayValue | MapValue | SliceValue | StructValue | InterfaceValue
+func (deb *debugger) fieldValue(indent tab, id typeId) {
+	_, ok := builtinIdToType[id]
+	if ok {
+		if id == tInterface {
+			deb.interfaceValue(indent)
+		} else {
+			deb.printBuiltin(indent, id)
+		}
+		return
+	}
+	wire, ok := deb.wireType[id]
+	if !ok {
+		errorf("type id %d not defined", id)
+	}
+	switch {
+	case wire.ArrayT != nil:
+		deb.arrayValue(indent, wire)
+	case wire.MapT != nil:
+		deb.mapValue(indent, wire)
+	case wire.SliceT != nil:
+		deb.sliceValue(indent, wire)
+	case wire.StructT != nil:
+		deb.structValue(indent, id)
+	case wire.GobEncoderT != nil:
+		deb.gobEncoderValue(indent, id)
+	default:
+		panic("bad wire type for field")
+	}
+}
+
+// printBuiltin prints a value not of a fundamental type, that is,
+// one whose type is known to gobs at bootstrap time.
+func (deb *debugger) printBuiltin(indent tab, id typeId) {
+	switch id {
+	case tBool:
+		x := deb.int64()
+		if x == 0 {
+			fmt.Fprintf(os.Stderr, "%sfalse\n", indent)
+		} else {
+			fmt.Fprintf(os.Stderr, "%strue\n", indent)
+		}
+	case tInt:
+		x := deb.int64()
+		fmt.Fprintf(os.Stderr, "%s%d\n", indent, x)
+	case tUint:
+		x := deb.uint64()
+		fmt.Fprintf(os.Stderr, "%s%d\n", indent, x)
+	case tFloat:
+		x := deb.uint64()
+		fmt.Fprintf(os.Stderr, "%s%g\n", indent, float64FromBits(x))
+	case tComplex:
+		r := deb.uint64()
+		i := deb.uint64()
+		fmt.Fprintf(os.Stderr, "%s%g+%gi\n", indent, float64FromBits(r), float64FromBits(i))
+	case tBytes:
+		x := int(deb.uint64())
+		b := make([]byte, x)
+		deb.r.Read(b)
+		deb.consumed(x)
+		fmt.Fprintf(os.Stderr, "%s{% x}=%q\n", indent, b, b)
+	case tString:
+		x := int(deb.uint64())
+		b := make([]byte, x)
+		deb.r.Read(b)
+		deb.consumed(x)
+		fmt.Fprintf(os.Stderr, "%s%q\n", indent, b)
+	default:
+		panic("unknown builtin")
+	}
+}
+
+// ArrayValue:
+//	uint(n) FieldValue*n
+func (deb *debugger) arrayValue(indent tab, wire *wireType) {
+	elemId := wire.ArrayT.Elem
+	u := deb.uint64()
+	length := int(u)
+	for i := 0; i < length; i++ {
+		deb.fieldValue(indent, elemId)
+	}
+	if length != wire.ArrayT.Len {
+		fmt.Fprintf(os.Stderr, "%s(wrong length for array: %d should be %d)\n", indent, length, wire.ArrayT.Len)
+	}
+}
+
+// MapValue:
+//	uint(n) (FieldValue FieldValue)*n  [n (key, value) pairs]
+func (deb *debugger) mapValue(indent tab, wire *wireType) {
+	keyId := wire.MapT.Key
+	elemId := wire.MapT.Elem
+	u := deb.uint64()
+	length := int(u)
+	for i := 0; i < length; i++ {
+		deb.fieldValue(indent+1, keyId)
+		deb.fieldValue(indent+1, elemId)
+	}
+}
+
+// SliceValue:
+//	uint(n) (n FieldValue)
+func (deb *debugger) sliceValue(indent tab, wire *wireType) {
+	elemId := wire.SliceT.Elem
+	u := deb.uint64()
+	length := int(u)
+	deb.dump("Start of slice of length %d", length)
+
+	for i := 0; i < length; i++ {
+		deb.fieldValue(indent, elemId)
+	}
+}
+
+// StructValue:
+//	(uint(fieldDelta) FieldValue)*
+func (deb *debugger) structValue(indent tab, id typeId) {
+	deb.dump("Start of struct value of %q id=%d\n<<\n", id.name(), id)
+	fmt.Fprintf(os.Stderr, "%s%s struct {\n", indent, id.name())
+	wire, ok := deb.wireType[id]
+	if !ok {
+		errorf("type id %d not defined", id)
+	}
+	strct := wire.StructT
+	fieldNum := -1
+	indent++
+	for {
+		delta := deb.uint64()
+		if delta == 0 { // struct terminator is zero delta fieldnum
+			break
+		}
+		fieldNum += int(delta)
+		if fieldNum < 0 || fieldNum >= len(strct.Field) {
+			deb.dump("field number out of range: prevField=%d delta=%d", fieldNum-int(delta), delta)
+			break
+		}
+		fmt.Fprintf(os.Stderr, "%sfield %d:\t%s\n", indent, fieldNum, wire.StructT.Field[fieldNum].Name)
+		deb.fieldValue(indent+1, strct.Field[fieldNum].Id)
+	}
+	indent--
+	fmt.Fprintf(os.Stderr, "%s} // end %s struct\n", indent, id.name())
+	deb.dump(">> End of struct value of type %d %q", id, id.name())
+}
+
+// GobEncoderValue:
+//	uint(n) byte*n
+func (deb *debugger) gobEncoderValue(indent tab, id typeId) {
+	len := deb.uint64()
+	deb.dump("GobEncoder value of %q id=%d, length %d\n", id.name(), id, len)
+	fmt.Fprintf(os.Stderr, "%s%s (implements GobEncoder)\n", indent, id.name())
+	data := make([]byte, len)
+	_, err := deb.r.Read(data)
+	if err != nil {
+		errorf("gobEncoder data read: %s", err)
+	}
+	fmt.Fprintf(os.Stderr, "%s[% .2x]\n", indent+1, data)
+}
diff --git a/src/encoding/gob/dec_helpers.go b/src/encoding/gob/dec_helpers.go
new file mode 100644
index 0000000..26eb9e4
--- /dev/null
+++ b/src/encoding/gob/dec_helpers.go
@@ -0,0 +1,469 @@
+// Code generated by go run decgen.go -output dec_helpers.go; DO NOT EDIT.
+
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package gob
+
+import (
+	"math"
+	"reflect"
+)
+
+var decArrayHelper = map[reflect.Kind]decHelper{
+	reflect.Bool:       decBoolArray,
+	reflect.Complex64:  decComplex64Array,
+	reflect.Complex128: decComplex128Array,
+	reflect.Float32:    decFloat32Array,
+	reflect.Float64:    decFloat64Array,
+	reflect.Int:        decIntArray,
+	reflect.Int16:      decInt16Array,
+	reflect.Int32:      decInt32Array,
+	reflect.Int64:      decInt64Array,
+	reflect.Int8:       decInt8Array,
+	reflect.String:     decStringArray,
+	reflect.Uint:       decUintArray,
+	reflect.Uint16:     decUint16Array,
+	reflect.Uint32:     decUint32Array,
+	reflect.Uint64:     decUint64Array,
+	reflect.Uintptr:    decUintptrArray,
+}
+
+var decSliceHelper = map[reflect.Kind]decHelper{
+	reflect.Bool:       decBoolSlice,
+	reflect.Complex64:  decComplex64Slice,
+	reflect.Complex128: decComplex128Slice,
+	reflect.Float32:    decFloat32Slice,
+	reflect.Float64:    decFloat64Slice,
+	reflect.Int:        decIntSlice,
+	reflect.Int16:      decInt16Slice,
+	reflect.Int32:      decInt32Slice,
+	reflect.Int64:      decInt64Slice,
+	reflect.Int8:       decInt8Slice,
+	reflect.String:     decStringSlice,
+	reflect.Uint:       decUintSlice,
+	reflect.Uint16:     decUint16Slice,
+	reflect.Uint32:     decUint32Slice,
+	reflect.Uint64:     decUint64Slice,
+	reflect.Uintptr:    decUintptrSlice,
+}
+
+func decBoolArray(state *decoderState, v reflect.Value, length int, ovfl error) bool {
+	// Can only slice if it is addressable.
+	if !v.CanAddr() {
+		return false
+	}
+	return decBoolSlice(state, v.Slice(0, v.Len()), length, ovfl)
+}
+
+func decBoolSlice(state *decoderState, v reflect.Value, length int, ovfl error) bool {
+	slice, ok := v.Interface().([]bool)
+	if !ok {
+		// It is kind bool but not type bool. TODO: We can handle this unsafely.
+		return false
+	}
+	for i := 0; i < length; i++ {
+		if state.b.Len() == 0 {
+			errorf("decoding bool array or slice: length exceeds input size (%d elements)", length)
+		}
+		slice[i] = state.decodeUint() != 0
+	}
+	return true
+}
+
+func decComplex64Array(state *decoderState, v reflect.Value, length int, ovfl error) bool {
+	// Can only slice if it is addressable.
+	if !v.CanAddr() {
+		return false
+	}
+	return decComplex64Slice(state, v.Slice(0, v.Len()), length, ovfl)
+}
+
+func decComplex64Slice(state *decoderState, v reflect.Value, length int, ovfl error) bool {
+	slice, ok := v.Interface().([]complex64)
+	if !ok {
+		// It is kind complex64 but not type complex64. TODO: We can handle this unsafely.
+		return false
+	}
+	for i := 0; i < length; i++ {
+		if state.b.Len() == 0 {
+			errorf("decoding complex64 array or slice: length exceeds input size (%d elements)", length)
+		}
+		real := float32FromBits(state.decodeUint(), ovfl)
+		imag := float32FromBits(state.decodeUint(), ovfl)
+		slice[i] = complex(float32(real), float32(imag))
+	}
+	return true
+}
+
+func decComplex128Array(state *decoderState, v reflect.Value, length int, ovfl error) bool {
+	// Can only slice if it is addressable.
+	if !v.CanAddr() {
+		return false
+	}
+	return decComplex128Slice(state, v.Slice(0, v.Len()), length, ovfl)
+}
+
+func decComplex128Slice(state *decoderState, v reflect.Value, length int, ovfl error) bool {
+	slice, ok := v.Interface().([]complex128)
+	if !ok {
+		// It is kind complex128 but not type complex128. TODO: We can handle this unsafely.
+		return false
+	}
+	for i := 0; i < length; i++ {
+		if state.b.Len() == 0 {
+			errorf("decoding complex128 array or slice: length exceeds input size (%d elements)", length)
+		}
+		real := float64FromBits(state.decodeUint())
+		imag := float64FromBits(state.decodeUint())
+		slice[i] = complex(real, imag)
+	}
+	return true
+}
+
+func decFloat32Array(state *decoderState, v reflect.Value, length int, ovfl error) bool {
+	// Can only slice if it is addressable.
+	if !v.CanAddr() {
+		return false
+	}
+	return decFloat32Slice(state, v.Slice(0, v.Len()), length, ovfl)
+}
+
+func decFloat32Slice(state *decoderState, v reflect.Value, length int, ovfl error) bool {
+	slice, ok := v.Interface().([]float32)
+	if !ok {
+		// It is kind float32 but not type float32. TODO: We can handle this unsafely.
+		return false
+	}
+	for i := 0; i < length; i++ {
+		if state.b.Len() == 0 {
+			errorf("decoding float32 array or slice: length exceeds input size (%d elements)", length)
+		}
+		slice[i] = float32(float32FromBits(state.decodeUint(), ovfl))
+	}
+	return true
+}
+
+func decFloat64Array(state *decoderState, v reflect.Value, length int, ovfl error) bool {
+	// Can only slice if it is addressable.
+	if !v.CanAddr() {
+		return false
+	}
+	return decFloat64Slice(state, v.Slice(0, v.Len()), length, ovfl)
+}
+
+func decFloat64Slice(state *decoderState, v reflect.Value, length int, ovfl error) bool {
+	slice, ok := v.Interface().([]float64)
+	if !ok {
+		// It is kind float64 but not type float64. TODO: We can handle this unsafely.
+		return false
+	}
+	for i := 0; i < length; i++ {
+		if state.b.Len() == 0 {
+			errorf("decoding float64 array or slice: length exceeds input size (%d elements)", length)
+		}
+		slice[i] = float64FromBits(state.decodeUint())
+	}
+	return true
+}
+
+func decIntArray(state *decoderState, v reflect.Value, length int, ovfl error) bool {
+	// Can only slice if it is addressable.
+	if !v.CanAddr() {
+		return false
+	}
+	return decIntSlice(state, v.Slice(0, v.Len()), length, ovfl)
+}
+
+func decIntSlice(state *decoderState, v reflect.Value, length int, ovfl error) bool {
+	slice, ok := v.Interface().([]int)
+	if !ok {
+		// It is kind int but not type int. TODO: We can handle this unsafely.
+		return false
+	}
+	for i := 0; i < length; i++ {
+		if state.b.Len() == 0 {
+			errorf("decoding int array or slice: length exceeds input size (%d elements)", length)
+		}
+		x := state.decodeInt()
+		// MinInt and MaxInt
+		if x < ^int64(^uint(0)>>1) || int64(^uint(0)>>1) < x {
+			error_(ovfl)
+		}
+		slice[i] = int(x)
+	}
+	return true
+}
+
+func decInt16Array(state *decoderState, v reflect.Value, length int, ovfl error) bool {
+	// Can only slice if it is addressable.
+	if !v.CanAddr() {
+		return false
+	}
+	return decInt16Slice(state, v.Slice(0, v.Len()), length, ovfl)
+}
+
+func decInt16Slice(state *decoderState, v reflect.Value, length int, ovfl error) bool {
+	slice, ok := v.Interface().([]int16)
+	if !ok {
+		// It is kind int16 but not type int16. TODO: We can handle this unsafely.
+		return false
+	}
+	for i := 0; i < length; i++ {
+		if state.b.Len() == 0 {
+			errorf("decoding int16 array or slice: length exceeds input size (%d elements)", length)
+		}
+		x := state.decodeInt()
+		if x < math.MinInt16 || math.MaxInt16 < x {
+			error_(ovfl)
+		}
+		slice[i] = int16(x)
+	}
+	return true
+}
+
+func decInt32Array(state *decoderState, v reflect.Value, length int, ovfl error) bool {
+	// Can only slice if it is addressable.
+	if !v.CanAddr() {
+		return false
+	}
+	return decInt32Slice(state, v.Slice(0, v.Len()), length, ovfl)
+}
+
+func decInt32Slice(state *decoderState, v reflect.Value, length int, ovfl error) bool {
+	slice, ok := v.Interface().([]int32)
+	if !ok {
+		// It is kind int32 but not type int32. TODO: We can handle this unsafely.
+		return false
+	}
+	for i := 0; i < length; i++ {
+		if state.b.Len() == 0 {
+			errorf("decoding int32 array or slice: length exceeds input size (%d elements)", length)
+		}
+		x := state.decodeInt()
+		if x < math.MinInt32 || math.MaxInt32 < x {
+			error_(ovfl)
+		}
+		slice[i] = int32(x)
+	}
+	return true
+}
+
+func decInt64Array(state *decoderState, v reflect.Value, length int, ovfl error) bool {
+	// Can only slice if it is addressable.
+	if !v.CanAddr() {
+		return false
+	}
+	return decInt64Slice(state, v.Slice(0, v.Len()), length, ovfl)
+}
+
+func decInt64Slice(state *decoderState, v reflect.Value, length int, ovfl error) bool {
+	slice, ok := v.Interface().([]int64)
+	if !ok {
+		// It is kind int64 but not type int64. TODO: We can handle this unsafely.
+		return false
+	}
+	for i := 0; i < length; i++ {
+		if state.b.Len() == 0 {
+			errorf("decoding int64 array or slice: length exceeds input size (%d elements)", length)
+		}
+		slice[i] = state.decodeInt()
+	}
+	return true
+}
+
+func decInt8Array(state *decoderState, v reflect.Value, length int, ovfl error) bool {
+	// Can only slice if it is addressable.
+	if !v.CanAddr() {
+		return false
+	}
+	return decInt8Slice(state, v.Slice(0, v.Len()), length, ovfl)
+}
+
+func decInt8Slice(state *decoderState, v reflect.Value, length int, ovfl error) bool {
+	slice, ok := v.Interface().([]int8)
+	if !ok {
+		// It is kind int8 but not type int8. TODO: We can handle this unsafely.
+		return false
+	}
+	for i := 0; i < length; i++ {
+		if state.b.Len() == 0 {
+			errorf("decoding int8 array or slice: length exceeds input size (%d elements)", length)
+		}
+		x := state.decodeInt()
+		if x < math.MinInt8 || math.MaxInt8 < x {
+			error_(ovfl)
+		}
+		slice[i] = int8(x)
+	}
+	return true
+}
+
+func decStringArray(state *decoderState, v reflect.Value, length int, ovfl error) bool {
+	// Can only slice if it is addressable.
+	if !v.CanAddr() {
+		return false
+	}
+	return decStringSlice(state, v.Slice(0, v.Len()), length, ovfl)
+}
+
+func decStringSlice(state *decoderState, v reflect.Value, length int, ovfl error) bool {
+	slice, ok := v.Interface().([]string)
+	if !ok {
+		// It is kind string but not type string. TODO: We can handle this unsafely.
+		return false
+	}
+	for i := 0; i < length; i++ {
+		if state.b.Len() == 0 {
+			errorf("decoding string array or slice: length exceeds input size (%d elements)", length)
+		}
+		u := state.decodeUint()
+		n := int(u)
+		if n < 0 || uint64(n) != u || n > state.b.Len() {
+			errorf("length of string exceeds input size (%d bytes)", u)
+		}
+		if n > state.b.Len() {
+			errorf("string data too long for buffer: %d", n)
+		}
+		// Read the data.
+		data := state.b.Bytes()
+		if len(data) < n {
+			errorf("invalid string length %d: exceeds input size %d", n, len(data))
+		}
+		slice[i] = string(data[:n])
+		state.b.Drop(n)
+	}
+	return true
+}
+
+func decUintArray(state *decoderState, v reflect.Value, length int, ovfl error) bool {
+	// Can only slice if it is addressable.
+	if !v.CanAddr() {
+		return false
+	}
+	return decUintSlice(state, v.Slice(0, v.Len()), length, ovfl)
+}
+
+func decUintSlice(state *decoderState, v reflect.Value, length int, ovfl error) bool {
+	slice, ok := v.Interface().([]uint)
+	if !ok {
+		// It is kind uint but not type uint. TODO: We can handle this unsafely.
+		return false
+	}
+	for i := 0; i < length; i++ {
+		if state.b.Len() == 0 {
+			errorf("decoding uint array or slice: length exceeds input size (%d elements)", length)
+		}
+		x := state.decodeUint()
+		/*TODO if math.MaxUint32 < x {
+			error_(ovfl)
+		}*/
+		slice[i] = uint(x)
+	}
+	return true
+}
+
+func decUint16Array(state *decoderState, v reflect.Value, length int, ovfl error) bool {
+	// Can only slice if it is addressable.
+	if !v.CanAddr() {
+		return false
+	}
+	return decUint16Slice(state, v.Slice(0, v.Len()), length, ovfl)
+}
+
+func decUint16Slice(state *decoderState, v reflect.Value, length int, ovfl error) bool {
+	slice, ok := v.Interface().([]uint16)
+	if !ok {
+		// It is kind uint16 but not type uint16. TODO: We can handle this unsafely.
+		return false
+	}
+	for i := 0; i < length; i++ {
+		if state.b.Len() == 0 {
+			errorf("decoding uint16 array or slice: length exceeds input size (%d elements)", length)
+		}
+		x := state.decodeUint()
+		if math.MaxUint16 < x {
+			error_(ovfl)
+		}
+		slice[i] = uint16(x)
+	}
+	return true
+}
+
+func decUint32Array(state *decoderState, v reflect.Value, length int, ovfl error) bool {
+	// Can only slice if it is addressable.
+	if !v.CanAddr() {
+		return false
+	}
+	return decUint32Slice(state, v.Slice(0, v.Len()), length, ovfl)
+}
+
+func decUint32Slice(state *decoderState, v reflect.Value, length int, ovfl error) bool {
+	slice, ok := v.Interface().([]uint32)
+	if !ok {
+		// It is kind uint32 but not type uint32. TODO: We can handle this unsafely.
+		return false
+	}
+	for i := 0; i < length; i++ {
+		if state.b.Len() == 0 {
+			errorf("decoding uint32 array or slice: length exceeds input size (%d elements)", length)
+		}
+		x := state.decodeUint()
+		if math.MaxUint32 < x {
+			error_(ovfl)
+		}
+		slice[i] = uint32(x)
+	}
+	return true
+}
+
+func decUint64Array(state *decoderState, v reflect.Value, length int, ovfl error) bool {
+	// Can only slice if it is addressable.
+	if !v.CanAddr() {
+		return false
+	}
+	return decUint64Slice(state, v.Slice(0, v.Len()), length, ovfl)
+}
+
+func decUint64Slice(state *decoderState, v reflect.Value, length int, ovfl error) bool {
+	slice, ok := v.Interface().([]uint64)
+	if !ok {
+		// It is kind uint64 but not type uint64. TODO: We can handle this unsafely.
+		return false
+	}
+	for i := 0; i < length; i++ {
+		if state.b.Len() == 0 {
+			errorf("decoding uint64 array or slice: length exceeds input size (%d elements)", length)
+		}
+		slice[i] = state.decodeUint()
+	}
+	return true
+}
+
+func decUintptrArray(state *decoderState, v reflect.Value, length int, ovfl error) bool {
+	// Can only slice if it is addressable.
+	if !v.CanAddr() {
+		return false
+	}
+	return decUintptrSlice(state, v.Slice(0, v.Len()), length, ovfl)
+}
+
+func decUintptrSlice(state *decoderState, v reflect.Value, length int, ovfl error) bool {
+	slice, ok := v.Interface().([]uintptr)
+	if !ok {
+		// It is kind uintptr but not type uintptr. TODO: We can handle this unsafely.
+		return false
+	}
+	for i := 0; i < length; i++ {
+		if state.b.Len() == 0 {
+			errorf("decoding uintptr array or slice: length exceeds input size (%d elements)", length)
+		}
+		x := state.decodeUint()
+		if uint64(^uintptr(0)) < x {
+			error_(ovfl)
+		}
+		slice[i] = uintptr(x)
+	}
+	return true
+}
diff --git a/src/encoding/gob/decgen.go b/src/encoding/gob/decgen.go
new file mode 100644
index 0000000..e40816e
--- /dev/null
+++ b/src/encoding/gob/decgen.go
@@ -0,0 +1,243 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build ignore
+
+// encgen writes the helper functions for encoding. Intended to be
+// used with go generate; see the invocation in encode.go.
+
+// TODO: We could do more by being unsafe. Add a -unsafe flag?
+
+package main
+
+import (
+	"bytes"
+	"flag"
+	"fmt"
+	"go/format"
+	"log"
+	"os"
+)
+
+var output = flag.String("output", "dec_helpers.go", "file name to write")
+
+type Type struct {
+	lower   string
+	upper   string
+	decoder string
+}
+
+var types = []Type{
+	{
+		"bool",
+		"Bool",
+		`slice[i] = state.decodeUint() != 0`,
+	},
+	{
+		"complex64",
+		"Complex64",
+		`real := float32FromBits(state.decodeUint(), ovfl)
+		imag := float32FromBits(state.decodeUint(), ovfl)
+		slice[i] = complex(float32(real), float32(imag))`,
+	},
+	{
+		"complex128",
+		"Complex128",
+		`real := float64FromBits(state.decodeUint())
+		imag := float64FromBits(state.decodeUint())
+		slice[i] = complex(real, imag)`,
+	},
+	{
+		"float32",
+		"Float32",
+		`slice[i] = float32(float32FromBits(state.decodeUint(), ovfl))`,
+	},
+	{
+		"float64",
+		"Float64",
+		`slice[i] = float64FromBits(state.decodeUint())`,
+	},
+	{
+		"int",
+		"Int",
+		`x := state.decodeInt()
+		// MinInt and MaxInt
+		if x < ^int64(^uint(0)>>1) || int64(^uint(0)>>1) < x {
+			error_(ovfl)
+		}
+		slice[i] = int(x)`,
+	},
+	{
+		"int16",
+		"Int16",
+		`x := state.decodeInt()
+		if x < math.MinInt16 || math.MaxInt16 < x {
+			error_(ovfl)
+		}
+		slice[i] = int16(x)`,
+	},
+	{
+		"int32",
+		"Int32",
+		`x := state.decodeInt()
+		if x < math.MinInt32 || math.MaxInt32 < x {
+			error_(ovfl)
+		}
+		slice[i] = int32(x)`,
+	},
+	{
+		"int64",
+		"Int64",
+		`slice[i] = state.decodeInt()`,
+	},
+	{
+		"int8",
+		"Int8",
+		`x := state.decodeInt()
+		if x < math.MinInt8 || math.MaxInt8 < x {
+			error_(ovfl)
+		}
+		slice[i] = int8(x)`,
+	},
+	{
+		"string",
+		"String",
+		`u := state.decodeUint()
+		n := int(u)
+		if n < 0 || uint64(n) != u || n > state.b.Len() {
+			errorf("length of string exceeds input size (%d bytes)", u)
+		}
+		if n > state.b.Len() {
+			errorf("string data too long for buffer: %d", n)
+		}
+		// Read the data.
+		data := state.b.Bytes()
+		if len(data) < n {
+			errorf("invalid string length %d: exceeds input size %d", n, len(data))
+		}
+		slice[i] = string(data[:n])
+		state.b.Drop(n)`,
+	},
+	{
+		"uint",
+		"Uint",
+		`x := state.decodeUint()
+		/*TODO if math.MaxUint32 < x {
+			error_(ovfl)
+		}*/
+		slice[i] = uint(x)`,
+	},
+	{
+		"uint16",
+		"Uint16",
+		`x := state.decodeUint()
+		if math.MaxUint16 < x {
+			error_(ovfl)
+		}
+		slice[i] = uint16(x)`,
+	},
+	{
+		"uint32",
+		"Uint32",
+		`x := state.decodeUint()
+		if math.MaxUint32 < x {
+			error_(ovfl)
+		}
+		slice[i] = uint32(x)`,
+	},
+	{
+		"uint64",
+		"Uint64",
+		`slice[i] = state.decodeUint()`,
+	},
+	{
+		"uintptr",
+		"Uintptr",
+		`x := state.decodeUint()
+		if uint64(^uintptr(0)) < x {
+			error_(ovfl)
+		}
+		slice[i] = uintptr(x)`,
+	},
+	// uint8 Handled separately.
+}
+
+func main() {
+	log.SetFlags(0)
+	log.SetPrefix("decgen: ")
+	flag.Parse()
+	if flag.NArg() != 0 {
+		log.Fatal("usage: decgen [--output filename]")
+	}
+	var b bytes.Buffer
+	fmt.Fprintf(&b, "// Code generated by go run decgen.go -output %s; DO NOT EDIT.\n", *output)
+	fmt.Fprint(&b, header)
+	printMaps(&b, "Array")
+	fmt.Fprint(&b, "\n")
+	printMaps(&b, "Slice")
+	for _, t := range types {
+		fmt.Fprintf(&b, arrayHelper, t.lower, t.upper)
+		fmt.Fprintf(&b, sliceHelper, t.lower, t.upper, t.decoder)
+	}
+	source, err := format.Source(b.Bytes())
+	if err != nil {
+		log.Fatal("source format error:", err)
+	}
+	fd, err := os.Create(*output)
+	if err != nil {
+		log.Fatal(err)
+	}
+	if _, err := fd.Write(source); err != nil {
+		log.Fatal(err)
+	}
+}
+
+func printMaps(b *bytes.Buffer, upperClass string) {
+	fmt.Fprintf(b, "var dec%sHelper = map[reflect.Kind]decHelper{\n", upperClass)
+	for _, t := range types {
+		fmt.Fprintf(b, "reflect.%s: dec%s%s,\n", t.upper, t.upper, upperClass)
+	}
+	fmt.Fprintf(b, "}\n")
+}
+
+const header = `
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package gob
+
+import (
+	"math"
+	"reflect"
+)
+
+`
+
+const arrayHelper = `
+func dec%[2]sArray(state *decoderState, v reflect.Value, length int, ovfl error) bool {
+	// Can only slice if it is addressable.
+	if !v.CanAddr() {
+		return false
+	}
+	return dec%[2]sSlice(state, v.Slice(0, v.Len()), length, ovfl)
+}
+`
+
+const sliceHelper = `
+func dec%[2]sSlice(state *decoderState, v reflect.Value, length int, ovfl error) bool {
+	slice, ok := v.Interface().([]%[1]s)
+	if !ok {
+		// It is kind %[1]s but not type %[1]s. TODO: We can handle this unsafely.
+		return false
+	}
+	for i := 0; i < length; i++ {
+		if state.b.Len() == 0 {
+			errorf("decoding %[1]s array or slice: length exceeds input size (%%d elements)", length)
+		}
+		%[3]s
+	}
+	return true
+}
+`
diff --git a/src/encoding/gob/decode.go b/src/encoding/gob/decode.go
new file mode 100644
index 0000000..eea2924
--- /dev/null
+++ b/src/encoding/gob/decode.go
@@ -0,0 +1,1264 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:generate go run decgen.go -output dec_helpers.go
+
+package gob
+
+import (
+	"encoding"
+	"errors"
+	"io"
+	"math"
+	"math/bits"
+	"reflect"
+)
+
+var (
+	errBadUint = errors.New("gob: encoded unsigned integer out of range")
+	errBadType = errors.New("gob: unknown type id or corrupted data")
+	errRange   = errors.New("gob: bad data: field numbers out of bounds")
+)
+
+type decHelper func(state *decoderState, v reflect.Value, length int, ovfl error) bool
+
+// decoderState is the execution state of an instance of the decoder. A new state
+// is created for nested objects.
+type decoderState struct {
+	dec *Decoder
+	// The buffer is stored with an extra indirection because it may be replaced
+	// if we load a type during decode (when reading an interface value).
+	b        *decBuffer
+	fieldnum int           // the last field number read.
+	next     *decoderState // for free list
+}
+
+// decBuffer is an extremely simple, fast implementation of a read-only byte buffer.
+// It is initialized by calling Size and then copying the data into the slice returned by Bytes().
+type decBuffer struct {
+	data   []byte
+	offset int // Read offset.
+}
+
+func (d *decBuffer) Read(p []byte) (int, error) {
+	n := copy(p, d.data[d.offset:])
+	if n == 0 && len(p) != 0 {
+		return 0, io.EOF
+	}
+	d.offset += n
+	return n, nil
+}
+
+func (d *decBuffer) Drop(n int) {
+	if n > d.Len() {
+		panic("drop")
+	}
+	d.offset += n
+}
+
+// Size grows the buffer to exactly n bytes, so d.Bytes() will
+// return a slice of length n. Existing data is first discarded.
+func (d *decBuffer) Size(n int) {
+	d.Reset()
+	if cap(d.data) < n {
+		d.data = make([]byte, n)
+	} else {
+		d.data = d.data[0:n]
+	}
+}
+
+func (d *decBuffer) ReadByte() (byte, error) {
+	if d.offset >= len(d.data) {
+		return 0, io.EOF
+	}
+	c := d.data[d.offset]
+	d.offset++
+	return c, nil
+}
+
+func (d *decBuffer) Len() int {
+	return len(d.data) - d.offset
+}
+
+func (d *decBuffer) Bytes() []byte {
+	return d.data[d.offset:]
+}
+
+func (d *decBuffer) Reset() {
+	d.data = d.data[0:0]
+	d.offset = 0
+}
+
+// We pass the bytes.Buffer separately for easier testing of the infrastructure
+// without requiring a full Decoder.
+func (dec *Decoder) newDecoderState(buf *decBuffer) *decoderState {
+	d := dec.freeList
+	if d == nil {
+		d = new(decoderState)
+		d.dec = dec
+	} else {
+		dec.freeList = d.next
+	}
+	d.b = buf
+	return d
+}
+
+func (dec *Decoder) freeDecoderState(d *decoderState) {
+	d.next = dec.freeList
+	dec.freeList = d
+}
+
+func overflow(name string) error {
+	return errors.New(`value for "` + name + `" out of range`)
+}
+
+// decodeUintReader reads an encoded unsigned integer from an io.Reader.
+// Used only by the Decoder to read the message length.
+func decodeUintReader(r io.Reader, buf []byte) (x uint64, width int, err error) {
+	width = 1
+	n, err := io.ReadFull(r, buf[0:width])
+	if n == 0 {
+		return
+	}
+	b := buf[0]
+	if b <= 0x7f {
+		return uint64(b), width, nil
+	}
+	n = -int(int8(b))
+	if n > uint64Size {
+		err = errBadUint
+		return
+	}
+	width, err = io.ReadFull(r, buf[0:n])
+	if err != nil {
+		if err == io.EOF {
+			err = io.ErrUnexpectedEOF
+		}
+		return
+	}
+	// Could check that the high byte is zero but it's not worth it.
+	for _, b := range buf[0:width] {
+		x = x<<8 | uint64(b)
+	}
+	width++ // +1 for length byte
+	return
+}
+
+// decodeUint reads an encoded unsigned integer from state.r.
+// Does not check for overflow.
+func (state *decoderState) decodeUint() (x uint64) {
+	b, err := state.b.ReadByte()
+	if err != nil {
+		error_(err)
+	}
+	if b <= 0x7f {
+		return uint64(b)
+	}
+	n := -int(int8(b))
+	if n > uint64Size {
+		error_(errBadUint)
+	}
+	buf := state.b.Bytes()
+	if len(buf) < n {
+		errorf("invalid uint data length %d: exceeds input size %d", n, len(buf))
+	}
+	// Don't need to check error; it's safe to loop regardless.
+	// Could check that the high byte is zero but it's not worth it.
+	for _, b := range buf[0:n] {
+		x = x<<8 | uint64(b)
+	}
+	state.b.Drop(n)
+	return x
+}
+
+// decodeInt reads an encoded signed integer from state.r.
+// Does not check for overflow.
+func (state *decoderState) decodeInt() int64 {
+	x := state.decodeUint()
+	if x&1 != 0 {
+		return ^int64(x >> 1)
+	}
+	return int64(x >> 1)
+}
+
+// getLength decodes the next uint and makes sure it is a possible
+// size for a data item that follows, which means it must fit in a
+// non-negative int and fit in the buffer.
+func (state *decoderState) getLength() (int, bool) {
+	n := int(state.decodeUint())
+	if n < 0 || state.b.Len() < n || tooBig <= n {
+		return 0, false
+	}
+	return n, true
+}
+
+// decOp is the signature of a decoding operator for a given type.
+type decOp func(i *decInstr, state *decoderState, v reflect.Value)
+
+// The 'instructions' of the decoding machine
+type decInstr struct {
+	op    decOp
+	field int   // field number of the wire type
+	index []int // field access indices for destination type
+	ovfl  error // error message for overflow/underflow (for arrays, of the elements)
+}
+
+// ignoreUint discards a uint value with no destination.
+func ignoreUint(i *decInstr, state *decoderState, v reflect.Value) {
+	state.decodeUint()
+}
+
+// ignoreTwoUints discards a uint value with no destination. It's used to skip
+// complex values.
+func ignoreTwoUints(i *decInstr, state *decoderState, v reflect.Value) {
+	state.decodeUint()
+	state.decodeUint()
+}
+
+// Since the encoder writes no zeros, if we arrive at a decoder we have
+// a value to extract and store. The field number has already been read
+// (it's how we knew to call this decoder).
+// Each decoder is responsible for handling any indirections associated
+// with the data structure. If any pointer so reached is nil, allocation must
+// be done.
+
+// decAlloc takes a value and returns a settable value that can
+// be assigned to. If the value is a pointer, decAlloc guarantees it points to storage.
+// The callers to the individual decoders are expected to have used decAlloc.
+// The individual decoders don't need to it.
+func decAlloc(v reflect.Value) reflect.Value {
+	for v.Kind() == reflect.Pointer {
+		if v.IsNil() {
+			v.Set(reflect.New(v.Type().Elem()))
+		}
+		v = v.Elem()
+	}
+	return v
+}
+
+// decBool decodes a uint and stores it as a boolean in value.
+func decBool(i *decInstr, state *decoderState, value reflect.Value) {
+	value.SetBool(state.decodeUint() != 0)
+}
+
+// decInt8 decodes an integer and stores it as an int8 in value.
+func decInt8(i *decInstr, state *decoderState, value reflect.Value) {
+	v := state.decodeInt()
+	if v < math.MinInt8 || math.MaxInt8 < v {
+		error_(i.ovfl)
+	}
+	value.SetInt(v)
+}
+
+// decUint8 decodes an unsigned integer and stores it as a uint8 in value.
+func decUint8(i *decInstr, state *decoderState, value reflect.Value) {
+	v := state.decodeUint()
+	if math.MaxUint8 < v {
+		error_(i.ovfl)
+	}
+	value.SetUint(v)
+}
+
+// decInt16 decodes an integer and stores it as an int16 in value.
+func decInt16(i *decInstr, state *decoderState, value reflect.Value) {
+	v := state.decodeInt()
+	if v < math.MinInt16 || math.MaxInt16 < v {
+		error_(i.ovfl)
+	}
+	value.SetInt(v)
+}
+
+// decUint16 decodes an unsigned integer and stores it as a uint16 in value.
+func decUint16(i *decInstr, state *decoderState, value reflect.Value) {
+	v := state.decodeUint()
+	if math.MaxUint16 < v {
+		error_(i.ovfl)
+	}
+	value.SetUint(v)
+}
+
+// decInt32 decodes an integer and stores it as an int32 in value.
+func decInt32(i *decInstr, state *decoderState, value reflect.Value) {
+	v := state.decodeInt()
+	if v < math.MinInt32 || math.MaxInt32 < v {
+		error_(i.ovfl)
+	}
+	value.SetInt(v)
+}
+
+// decUint32 decodes an unsigned integer and stores it as a uint32 in value.
+func decUint32(i *decInstr, state *decoderState, value reflect.Value) {
+	v := state.decodeUint()
+	if math.MaxUint32 < v {
+		error_(i.ovfl)
+	}
+	value.SetUint(v)
+}
+
+// decInt64 decodes an integer and stores it as an int64 in value.
+func decInt64(i *decInstr, state *decoderState, value reflect.Value) {
+	v := state.decodeInt()
+	value.SetInt(v)
+}
+
+// decUint64 decodes an unsigned integer and stores it as a uint64 in value.
+func decUint64(i *decInstr, state *decoderState, value reflect.Value) {
+	v := state.decodeUint()
+	value.SetUint(v)
+}
+
+// Floating-point numbers are transmitted as uint64s holding the bits
+// of the underlying representation. They are sent byte-reversed, with
+// the exponent end coming out first, so integer floating point numbers
+// (for example) transmit more compactly. This routine does the
+// unswizzling.
+func float64FromBits(u uint64) float64 {
+	v := bits.ReverseBytes64(u)
+	return math.Float64frombits(v)
+}
+
+// float32FromBits decodes an unsigned integer, treats it as a 32-bit floating-point
+// number, and returns it. It's a helper function for float32 and complex64.
+// It returns a float64 because that's what reflection needs, but its return
+// value is known to be accurately representable in a float32.
+func float32FromBits(u uint64, ovfl error) float64 {
+	v := float64FromBits(u)
+	av := v
+	if av < 0 {
+		av = -av
+	}
+	// +Inf is OK in both 32- and 64-bit floats. Underflow is always OK.
+	if math.MaxFloat32 < av && av <= math.MaxFloat64 {
+		error_(ovfl)
+	}
+	return v
+}
+
+// decFloat32 decodes an unsigned integer, treats it as a 32-bit floating-point
+// number, and stores it in value.
+func decFloat32(i *decInstr, state *decoderState, value reflect.Value) {
+	value.SetFloat(float32FromBits(state.decodeUint(), i.ovfl))
+}
+
+// decFloat64 decodes an unsigned integer, treats it as a 64-bit floating-point
+// number, and stores it in value.
+func decFloat64(i *decInstr, state *decoderState, value reflect.Value) {
+	value.SetFloat(float64FromBits(state.decodeUint()))
+}
+
+// decComplex64 decodes a pair of unsigned integers, treats them as a
+// pair of floating point numbers, and stores them as a complex64 in value.
+// The real part comes first.
+func decComplex64(i *decInstr, state *decoderState, value reflect.Value) {
+	real := float32FromBits(state.decodeUint(), i.ovfl)
+	imag := float32FromBits(state.decodeUint(), i.ovfl)
+	value.SetComplex(complex(real, imag))
+}
+
+// decComplex128 decodes a pair of unsigned integers, treats them as a
+// pair of floating point numbers, and stores them as a complex128 in value.
+// The real part comes first.
+func decComplex128(i *decInstr, state *decoderState, value reflect.Value) {
+	real := float64FromBits(state.decodeUint())
+	imag := float64FromBits(state.decodeUint())
+	value.SetComplex(complex(real, imag))
+}
+
+// decUint8Slice decodes a byte slice and stores in value a slice header
+// describing the data.
+// uint8 slices are encoded as an unsigned count followed by the raw bytes.
+func decUint8Slice(i *decInstr, state *decoderState, value reflect.Value) {
+	n, ok := state.getLength()
+	if !ok {
+		errorf("bad %s slice length: %d", value.Type(), n)
+	}
+	if value.Cap() < n {
+		value.Set(reflect.MakeSlice(value.Type(), n, n))
+	} else {
+		value.SetLen(n)
+	}
+	if _, err := state.b.Read(value.Bytes()); err != nil {
+		errorf("error decoding []byte: %s", err)
+	}
+}
+
+// decString decodes byte array and stores in value a string header
+// describing the data.
+// Strings are encoded as an unsigned count followed by the raw bytes.
+func decString(i *decInstr, state *decoderState, value reflect.Value) {
+	n, ok := state.getLength()
+	if !ok {
+		errorf("bad %s slice length: %d", value.Type(), n)
+	}
+	// Read the data.
+	data := state.b.Bytes()
+	if len(data) < n {
+		errorf("invalid string length %d: exceeds input size %d", n, len(data))
+	}
+	s := string(data[:n])
+	state.b.Drop(n)
+	value.SetString(s)
+}
+
+// ignoreUint8Array skips over the data for a byte slice value with no destination.
+func ignoreUint8Array(i *decInstr, state *decoderState, value reflect.Value) {
+	n, ok := state.getLength()
+	if !ok {
+		errorf("slice length too large")
+	}
+	bn := state.b.Len()
+	if bn < n {
+		errorf("invalid slice length %d: exceeds input size %d", n, bn)
+	}
+	state.b.Drop(n)
+}
+
+// Execution engine
+
+// The encoder engine is an array of instructions indexed by field number of the incoming
+// decoder. It is executed with random access according to field number.
+type decEngine struct {
+	instr    []decInstr
+	numInstr int // the number of active instructions
+}
+
+// decodeSingle decodes a top-level value that is not a struct and stores it in value.
+// Such values are preceded by a zero, making them have the memory layout of a
+// struct field (although with an illegal field number).
+func (dec *Decoder) decodeSingle(engine *decEngine, value reflect.Value) {
+	state := dec.newDecoderState(&dec.buf)
+	defer dec.freeDecoderState(state)
+	state.fieldnum = singletonField
+	if state.decodeUint() != 0 {
+		errorf("decode: corrupted data: non-zero delta for singleton")
+	}
+	instr := &engine.instr[singletonField]
+	instr.op(instr, state, value)
+}
+
+// decodeStruct decodes a top-level struct and stores it in value.
+// Indir is for the value, not the type. At the time of the call it may
+// differ from ut.indir, which was computed when the engine was built.
+// This state cannot arise for decodeSingle, which is called directly
+// from the user's value, not from the innards of an engine.
+func (dec *Decoder) decodeStruct(engine *decEngine, value reflect.Value) {
+	state := dec.newDecoderState(&dec.buf)
+	defer dec.freeDecoderState(state)
+	state.fieldnum = -1
+	for state.b.Len() > 0 {
+		delta := int(state.decodeUint())
+		if delta < 0 {
+			errorf("decode: corrupted data: negative delta")
+		}
+		if delta == 0 { // struct terminator is zero delta fieldnum
+			break
+		}
+		fieldnum := state.fieldnum + delta
+		if fieldnum >= len(engine.instr) {
+			error_(errRange)
+			break
+		}
+		instr := &engine.instr[fieldnum]
+		var field reflect.Value
+		if instr.index != nil {
+			// Otherwise the field is unknown to us and instr.op is an ignore op.
+			field = value.FieldByIndex(instr.index)
+			if field.Kind() == reflect.Pointer {
+				field = decAlloc(field)
+			}
+		}
+		instr.op(instr, state, field)
+		state.fieldnum = fieldnum
+	}
+}
+
+var noValue reflect.Value
+
+// ignoreStruct discards the data for a struct with no destination.
+func (dec *Decoder) ignoreStruct(engine *decEngine) {
+	state := dec.newDecoderState(&dec.buf)
+	defer dec.freeDecoderState(state)
+	state.fieldnum = -1
+	for state.b.Len() > 0 {
+		delta := int(state.decodeUint())
+		if delta < 0 {
+			errorf("ignore decode: corrupted data: negative delta")
+		}
+		if delta == 0 { // struct terminator is zero delta fieldnum
+			break
+		}
+		fieldnum := state.fieldnum + delta
+		if fieldnum >= len(engine.instr) {
+			error_(errRange)
+		}
+		instr := &engine.instr[fieldnum]
+		instr.op(instr, state, noValue)
+		state.fieldnum = fieldnum
+	}
+}
+
+// ignoreSingle discards the data for a top-level non-struct value with no
+// destination. It's used when calling Decode with a nil value.
+func (dec *Decoder) ignoreSingle(engine *decEngine) {
+	state := dec.newDecoderState(&dec.buf)
+	defer dec.freeDecoderState(state)
+	state.fieldnum = singletonField
+	delta := int(state.decodeUint())
+	if delta != 0 {
+		errorf("decode: corrupted data: non-zero delta for singleton")
+	}
+	instr := &engine.instr[singletonField]
+	instr.op(instr, state, noValue)
+}
+
+// decodeArrayHelper does the work for decoding arrays and slices.
+func (dec *Decoder) decodeArrayHelper(state *decoderState, value reflect.Value, elemOp decOp, length int, ovfl error, helper decHelper) {
+	if helper != nil && helper(state, value, length, ovfl) {
+		return
+	}
+	instr := &decInstr{elemOp, 0, nil, ovfl}
+	isPtr := value.Type().Elem().Kind() == reflect.Pointer
+	for i := 0; i < length; i++ {
+		if state.b.Len() == 0 {
+			errorf("decoding array or slice: length exceeds input size (%d elements)", length)
+		}
+		v := value.Index(i)
+		if isPtr {
+			v = decAlloc(v)
+		}
+		elemOp(instr, state, v)
+	}
+}
+
+// decodeArray decodes an array and stores it in value.
+// The length is an unsigned integer preceding the elements. Even though the length is redundant
+// (it's part of the type), it's a useful check and is included in the encoding.
+func (dec *Decoder) decodeArray(state *decoderState, value reflect.Value, elemOp decOp, length int, ovfl error, helper decHelper) {
+	if n := state.decodeUint(); n != uint64(length) {
+		errorf("length mismatch in decodeArray")
+	}
+	dec.decodeArrayHelper(state, value, elemOp, length, ovfl, helper)
+}
+
+// decodeIntoValue is a helper for map decoding.
+func decodeIntoValue(state *decoderState, op decOp, isPtr bool, value reflect.Value, instr *decInstr) reflect.Value {
+	v := value
+	if isPtr {
+		v = decAlloc(value)
+	}
+
+	op(instr, state, v)
+	return value
+}
+
+// decodeMap decodes a map and stores it in value.
+// Maps are encoded as a length followed by key:value pairs.
+// Because the internals of maps are not visible to us, we must
+// use reflection rather than pointer magic.
+func (dec *Decoder) decodeMap(mtyp reflect.Type, state *decoderState, value reflect.Value, keyOp, elemOp decOp, ovfl error) {
+	n := int(state.decodeUint())
+	if value.IsNil() {
+		value.Set(reflect.MakeMapWithSize(mtyp, n))
+	}
+	keyIsPtr := mtyp.Key().Kind() == reflect.Pointer
+	elemIsPtr := mtyp.Elem().Kind() == reflect.Pointer
+	keyInstr := &decInstr{keyOp, 0, nil, ovfl}
+	elemInstr := &decInstr{elemOp, 0, nil, ovfl}
+	keyP := reflect.New(mtyp.Key())
+	keyZ := reflect.Zero(mtyp.Key())
+	elemP := reflect.New(mtyp.Elem())
+	elemZ := reflect.Zero(mtyp.Elem())
+	for i := 0; i < n; i++ {
+		key := decodeIntoValue(state, keyOp, keyIsPtr, keyP.Elem(), keyInstr)
+		elem := decodeIntoValue(state, elemOp, elemIsPtr, elemP.Elem(), elemInstr)
+		value.SetMapIndex(key, elem)
+		keyP.Elem().Set(keyZ)
+		elemP.Elem().Set(elemZ)
+	}
+}
+
+// ignoreArrayHelper does the work for discarding arrays and slices.
+func (dec *Decoder) ignoreArrayHelper(state *decoderState, elemOp decOp, length int) {
+	instr := &decInstr{elemOp, 0, nil, errors.New("no error")}
+	for i := 0; i < length; i++ {
+		if state.b.Len() == 0 {
+			errorf("decoding array or slice: length exceeds input size (%d elements)", length)
+		}
+		elemOp(instr, state, noValue)
+	}
+}
+
+// ignoreArray discards the data for an array value with no destination.
+func (dec *Decoder) ignoreArray(state *decoderState, elemOp decOp, length int) {
+	if n := state.decodeUint(); n != uint64(length) {
+		errorf("length mismatch in ignoreArray")
+	}
+	dec.ignoreArrayHelper(state, elemOp, length)
+}
+
+// ignoreMap discards the data for a map value with no destination.
+func (dec *Decoder) ignoreMap(state *decoderState, keyOp, elemOp decOp) {
+	n := int(state.decodeUint())
+	keyInstr := &decInstr{keyOp, 0, nil, errors.New("no error")}
+	elemInstr := &decInstr{elemOp, 0, nil, errors.New("no error")}
+	for i := 0; i < n; i++ {
+		keyOp(keyInstr, state, noValue)
+		elemOp(elemInstr, state, noValue)
+	}
+}
+
+// decodeSlice decodes a slice and stores it in value.
+// Slices are encoded as an unsigned length followed by the elements.
+func (dec *Decoder) decodeSlice(state *decoderState, value reflect.Value, elemOp decOp, ovfl error, helper decHelper) {
+	u := state.decodeUint()
+	typ := value.Type()
+	size := uint64(typ.Elem().Size())
+	nBytes := u * size
+	n := int(u)
+	// Take care with overflow in this calculation.
+	if n < 0 || uint64(n) != u || nBytes > tooBig || (size > 0 && nBytes/size != u) {
+		// We don't check n against buffer length here because if it's a slice
+		// of interfaces, there will be buffer reloads.
+		errorf("%s slice too big: %d elements of %d bytes", typ.Elem(), u, size)
+	}
+	if value.Cap() < n {
+		value.Set(reflect.MakeSlice(typ, n, n))
+	} else {
+		value.SetLen(n)
+	}
+	dec.decodeArrayHelper(state, value, elemOp, n, ovfl, helper)
+}
+
+// ignoreSlice skips over the data for a slice value with no destination.
+func (dec *Decoder) ignoreSlice(state *decoderState, elemOp decOp) {
+	dec.ignoreArrayHelper(state, elemOp, int(state.decodeUint()))
+}
+
+// decodeInterface decodes an interface value and stores it in value.
+// Interfaces are encoded as the name of a concrete type followed by a value.
+// If the name is empty, the value is nil and no value is sent.
+func (dec *Decoder) decodeInterface(ityp reflect.Type, state *decoderState, value reflect.Value) {
+	// Read the name of the concrete type.
+	nr := state.decodeUint()
+	if nr > 1<<31 { // zero is permissible for anonymous types
+		errorf("invalid type name length %d", nr)
+	}
+	if nr > uint64(state.b.Len()) {
+		errorf("invalid type name length %d: exceeds input size", nr)
+	}
+	n := int(nr)
+	name := state.b.Bytes()[:n]
+	state.b.Drop(n)
+	// Allocate the destination interface value.
+	if len(name) == 0 {
+		// Copy the nil interface value to the target.
+		value.Set(reflect.Zero(value.Type()))
+		return
+	}
+	if len(name) > 1024 {
+		errorf("name too long (%d bytes): %.20q...", len(name), name)
+	}
+	// The concrete type must be registered.
+	typi, ok := nameToConcreteType.Load(string(name))
+	if !ok {
+		errorf("name not registered for interface: %q", name)
+	}
+	typ := typi.(reflect.Type)
+
+	// Read the type id of the concrete value.
+	concreteId := dec.decodeTypeSequence(true)
+	if concreteId < 0 {
+		error_(dec.err)
+	}
+	// Byte count of value is next; we don't care what it is (it's there
+	// in case we want to ignore the value by skipping it completely).
+	state.decodeUint()
+	// Read the concrete value.
+	v := allocValue(typ)
+	dec.decodeValue(concreteId, v)
+	if dec.err != nil {
+		error_(dec.err)
+	}
+	// Assign the concrete value to the interface.
+	// Tread carefully; it might not satisfy the interface.
+	if !typ.AssignableTo(ityp) {
+		errorf("%s is not assignable to type %s", typ, ityp)
+	}
+	// Copy the interface value to the target.
+	value.Set(v)
+}
+
+// ignoreInterface discards the data for an interface value with no destination.
+func (dec *Decoder) ignoreInterface(state *decoderState) {
+	// Read the name of the concrete type.
+	n, ok := state.getLength()
+	if !ok {
+		errorf("bad interface encoding: name too large for buffer")
+	}
+	bn := state.b.Len()
+	if bn < n {
+		errorf("invalid interface value length %d: exceeds input size %d", n, bn)
+	}
+	state.b.Drop(n)
+	id := dec.decodeTypeSequence(true)
+	if id < 0 {
+		error_(dec.err)
+	}
+	// At this point, the decoder buffer contains a delimited value. Just toss it.
+	n, ok = state.getLength()
+	if !ok {
+		errorf("bad interface encoding: data length too large for buffer")
+	}
+	state.b.Drop(n)
+}
+
+// decodeGobDecoder decodes something implementing the GobDecoder interface.
+// The data is encoded as a byte slice.
+func (dec *Decoder) decodeGobDecoder(ut *userTypeInfo, state *decoderState, value reflect.Value) {
+	// Read the bytes for the value.
+	n, ok := state.getLength()
+	if !ok {
+		errorf("GobDecoder: length too large for buffer")
+	}
+	b := state.b.Bytes()
+	if len(b) < n {
+		errorf("GobDecoder: invalid data length %d: exceeds input size %d", n, len(b))
+	}
+	b = b[:n]
+	state.b.Drop(n)
+	var err error
+	// We know it's one of these.
+	switch ut.externalDec {
+	case xGob:
+		err = value.Interface().(GobDecoder).GobDecode(b)
+	case xBinary:
+		err = value.Interface().(encoding.BinaryUnmarshaler).UnmarshalBinary(b)
+	case xText:
+		err = value.Interface().(encoding.TextUnmarshaler).UnmarshalText(b)
+	}
+	if err != nil {
+		error_(err)
+	}
+}
+
+// ignoreGobDecoder discards the data for a GobDecoder value with no destination.
+func (dec *Decoder) ignoreGobDecoder(state *decoderState) {
+	// Read the bytes for the value.
+	n, ok := state.getLength()
+	if !ok {
+		errorf("GobDecoder: length too large for buffer")
+	}
+	bn := state.b.Len()
+	if bn < n {
+		errorf("GobDecoder: invalid data length %d: exceeds input size %d", n, bn)
+	}
+	state.b.Drop(n)
+}
+
+// Index by Go types.
+var decOpTable = [...]decOp{
+	reflect.Bool:       decBool,
+	reflect.Int8:       decInt8,
+	reflect.Int16:      decInt16,
+	reflect.Int32:      decInt32,
+	reflect.Int64:      decInt64,
+	reflect.Uint8:      decUint8,
+	reflect.Uint16:     decUint16,
+	reflect.Uint32:     decUint32,
+	reflect.Uint64:     decUint64,
+	reflect.Float32:    decFloat32,
+	reflect.Float64:    decFloat64,
+	reflect.Complex64:  decComplex64,
+	reflect.Complex128: decComplex128,
+	reflect.String:     decString,
+}
+
+// Indexed by gob types.  tComplex will be added during type.init().
+var decIgnoreOpMap = map[typeId]decOp{
+	tBool:    ignoreUint,
+	tInt:     ignoreUint,
+	tUint:    ignoreUint,
+	tFloat:   ignoreUint,
+	tBytes:   ignoreUint8Array,
+	tString:  ignoreUint8Array,
+	tComplex: ignoreTwoUints,
+}
+
+// decOpFor returns the decoding op for the base type under rt and
+// the indirection count to reach it.
+func (dec *Decoder) decOpFor(wireId typeId, rt reflect.Type, name string, inProgress map[reflect.Type]*decOp) *decOp {
+	ut := userType(rt)
+	// If the type implements GobEncoder, we handle it without further processing.
+	if ut.externalDec != 0 {
+		return dec.gobDecodeOpFor(ut)
+	}
+
+	// If this type is already in progress, it's a recursive type (e.g. map[string]*T).
+	// Return the pointer to the op we're already building.
+	if opPtr := inProgress[rt]; opPtr != nil {
+		return opPtr
+	}
+	typ := ut.base
+	var op decOp
+	k := typ.Kind()
+	if int(k) < len(decOpTable) {
+		op = decOpTable[k]
+	}
+	if op == nil {
+		inProgress[rt] = &op
+		// Special cases
+		switch t := typ; t.Kind() {
+		case reflect.Array:
+			name = "element of " + name
+			elemId := dec.wireType[wireId].ArrayT.Elem
+			elemOp := dec.decOpFor(elemId, t.Elem(), name, inProgress)
+			ovfl := overflow(name)
+			helper := decArrayHelper[t.Elem().Kind()]
+			op = func(i *decInstr, state *decoderState, value reflect.Value) {
+				state.dec.decodeArray(state, value, *elemOp, t.Len(), ovfl, helper)
+			}
+
+		case reflect.Map:
+			keyId := dec.wireType[wireId].MapT.Key
+			elemId := dec.wireType[wireId].MapT.Elem
+			keyOp := dec.decOpFor(keyId, t.Key(), "key of "+name, inProgress)
+			elemOp := dec.decOpFor(elemId, t.Elem(), "element of "+name, inProgress)
+			ovfl := overflow(name)
+			op = func(i *decInstr, state *decoderState, value reflect.Value) {
+				state.dec.decodeMap(t, state, value, *keyOp, *elemOp, ovfl)
+			}
+
+		case reflect.Slice:
+			name = "element of " + name
+			if t.Elem().Kind() == reflect.Uint8 {
+				op = decUint8Slice
+				break
+			}
+			var elemId typeId
+			if tt, ok := builtinIdToType[wireId]; ok {
+				elemId = tt.(*sliceType).Elem
+			} else {
+				elemId = dec.wireType[wireId].SliceT.Elem
+			}
+			elemOp := dec.decOpFor(elemId, t.Elem(), name, inProgress)
+			ovfl := overflow(name)
+			helper := decSliceHelper[t.Elem().Kind()]
+			op = func(i *decInstr, state *decoderState, value reflect.Value) {
+				state.dec.decodeSlice(state, value, *elemOp, ovfl, helper)
+			}
+
+		case reflect.Struct:
+			// Generate a closure that calls out to the engine for the nested type.
+			ut := userType(typ)
+			enginePtr, err := dec.getDecEnginePtr(wireId, ut)
+			if err != nil {
+				error_(err)
+			}
+			op = func(i *decInstr, state *decoderState, value reflect.Value) {
+				// indirect through enginePtr to delay evaluation for recursive structs.
+				dec.decodeStruct(*enginePtr, value)
+			}
+		case reflect.Interface:
+			op = func(i *decInstr, state *decoderState, value reflect.Value) {
+				state.dec.decodeInterface(t, state, value)
+			}
+		}
+	}
+	if op == nil {
+		errorf("decode can't handle type %s", rt)
+	}
+	return &op
+}
+
+var maxIgnoreNestingDepth = 10000
+
+// decIgnoreOpFor returns the decoding op for a field that has no destination.
+func (dec *Decoder) decIgnoreOpFor(wireId typeId, inProgress map[typeId]*decOp, depth int) *decOp {
+	if depth > maxIgnoreNestingDepth {
+		error_(errors.New("invalid nesting depth"))
+	}
+	// If this type is already in progress, it's a recursive type (e.g. map[string]*T).
+	// Return the pointer to the op we're already building.
+	if opPtr := inProgress[wireId]; opPtr != nil {
+		return opPtr
+	}
+	op, ok := decIgnoreOpMap[wireId]
+	if !ok {
+		inProgress[wireId] = &op
+		if wireId == tInterface {
+			// Special case because it's a method: the ignored item might
+			// define types and we need to record their state in the decoder.
+			op = func(i *decInstr, state *decoderState, value reflect.Value) {
+				state.dec.ignoreInterface(state)
+			}
+			return &op
+		}
+		// Special cases
+		wire := dec.wireType[wireId]
+		switch {
+		case wire == nil:
+			errorf("bad data: undefined type %s", wireId.string())
+		case wire.ArrayT != nil:
+			elemId := wire.ArrayT.Elem
+			elemOp := dec.decIgnoreOpFor(elemId, inProgress, depth+1)
+			op = func(i *decInstr, state *decoderState, value reflect.Value) {
+				state.dec.ignoreArray(state, *elemOp, wire.ArrayT.Len)
+			}
+
+		case wire.MapT != nil:
+			keyId := dec.wireType[wireId].MapT.Key
+			elemId := dec.wireType[wireId].MapT.Elem
+			keyOp := dec.decIgnoreOpFor(keyId, inProgress, depth+1)
+			elemOp := dec.decIgnoreOpFor(elemId, inProgress, depth+1)
+			op = func(i *decInstr, state *decoderState, value reflect.Value) {
+				state.dec.ignoreMap(state, *keyOp, *elemOp)
+			}
+
+		case wire.SliceT != nil:
+			elemId := wire.SliceT.Elem
+			elemOp := dec.decIgnoreOpFor(elemId, inProgress, depth+1)
+			op = func(i *decInstr, state *decoderState, value reflect.Value) {
+				state.dec.ignoreSlice(state, *elemOp)
+			}
+
+		case wire.StructT != nil:
+			// Generate a closure that calls out to the engine for the nested type.
+			enginePtr, err := dec.getIgnoreEnginePtr(wireId)
+			if err != nil {
+				error_(err)
+			}
+			op = func(i *decInstr, state *decoderState, value reflect.Value) {
+				// indirect through enginePtr to delay evaluation for recursive structs
+				state.dec.ignoreStruct(*enginePtr)
+			}
+
+		case wire.GobEncoderT != nil, wire.BinaryMarshalerT != nil, wire.TextMarshalerT != nil:
+			op = func(i *decInstr, state *decoderState, value reflect.Value) {
+				state.dec.ignoreGobDecoder(state)
+			}
+		}
+	}
+	if op == nil {
+		errorf("bad data: ignore can't handle type %s", wireId.string())
+	}
+	return &op
+}
+
+// gobDecodeOpFor returns the op for a type that is known to implement
+// GobDecoder.
+func (dec *Decoder) gobDecodeOpFor(ut *userTypeInfo) *decOp {
+	rcvrType := ut.user
+	if ut.decIndir == -1 {
+		rcvrType = reflect.PointerTo(rcvrType)
+	} else if ut.decIndir > 0 {
+		for i := int8(0); i < ut.decIndir; i++ {
+			rcvrType = rcvrType.Elem()
+		}
+	}
+	var op decOp
+	op = func(i *decInstr, state *decoderState, value reflect.Value) {
+		// We now have the base type. We need its address if the receiver is a pointer.
+		if value.Kind() != reflect.Pointer && rcvrType.Kind() == reflect.Pointer {
+			value = value.Addr()
+		}
+		state.dec.decodeGobDecoder(ut, state, value)
+	}
+	return &op
+}
+
+// compatibleType asks: Are these two gob Types compatible?
+// Answers the question for basic types, arrays, maps and slices, plus
+// GobEncoder/Decoder pairs.
+// Structs are considered ok; fields will be checked later.
+func (dec *Decoder) compatibleType(fr reflect.Type, fw typeId, inProgress map[reflect.Type]typeId) bool {
+	if rhs, ok := inProgress[fr]; ok {
+		return rhs == fw
+	}
+	inProgress[fr] = fw
+	ut := userType(fr)
+	wire, ok := dec.wireType[fw]
+	// If wire was encoded with an encoding method, fr must have that method.
+	// And if not, it must not.
+	// At most one of the booleans in ut is set.
+	// We could possibly relax this constraint in the future in order to
+	// choose the decoding method using the data in the wireType.
+	// The parentheses look odd but are correct.
+	if (ut.externalDec == xGob) != (ok && wire.GobEncoderT != nil) ||
+		(ut.externalDec == xBinary) != (ok && wire.BinaryMarshalerT != nil) ||
+		(ut.externalDec == xText) != (ok && wire.TextMarshalerT != nil) {
+		return false
+	}
+	if ut.externalDec != 0 { // This test trumps all others.
+		return true
+	}
+	switch t := ut.base; t.Kind() {
+	default:
+		// chan, etc: cannot handle.
+		return false
+	case reflect.Bool:
+		return fw == tBool
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return fw == tInt
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		return fw == tUint
+	case reflect.Float32, reflect.Float64:
+		return fw == tFloat
+	case reflect.Complex64, reflect.Complex128:
+		return fw == tComplex
+	case reflect.String:
+		return fw == tString
+	case reflect.Interface:
+		return fw == tInterface
+	case reflect.Array:
+		if !ok || wire.ArrayT == nil {
+			return false
+		}
+		array := wire.ArrayT
+		return t.Len() == array.Len && dec.compatibleType(t.Elem(), array.Elem, inProgress)
+	case reflect.Map:
+		if !ok || wire.MapT == nil {
+			return false
+		}
+		MapType := wire.MapT
+		return dec.compatibleType(t.Key(), MapType.Key, inProgress) && dec.compatibleType(t.Elem(), MapType.Elem, inProgress)
+	case reflect.Slice:
+		// Is it an array of bytes?
+		if t.Elem().Kind() == reflect.Uint8 {
+			return fw == tBytes
+		}
+		// Extract and compare element types.
+		var sw *sliceType
+		if tt, ok := builtinIdToType[fw]; ok {
+			sw, _ = tt.(*sliceType)
+		} else if wire != nil {
+			sw = wire.SliceT
+		}
+		elem := userType(t.Elem()).base
+		return sw != nil && dec.compatibleType(elem, sw.Elem, inProgress)
+	case reflect.Struct:
+		return true
+	}
+}
+
+// typeString returns a human-readable description of the type identified by remoteId.
+func (dec *Decoder) typeString(remoteId typeId) string {
+	typeLock.Lock()
+	defer typeLock.Unlock()
+	if t := idToType[remoteId]; t != nil {
+		// globally known type.
+		return t.string()
+	}
+	return dec.wireType[remoteId].string()
+}
+
+// compileSingle compiles the decoder engine for a non-struct top-level value, including
+// GobDecoders.
+func (dec *Decoder) compileSingle(remoteId typeId, ut *userTypeInfo) (engine *decEngine, err error) {
+	rt := ut.user
+	engine = new(decEngine)
+	engine.instr = make([]decInstr, 1) // one item
+	name := rt.String()                // best we can do
+	if !dec.compatibleType(rt, remoteId, make(map[reflect.Type]typeId)) {
+		remoteType := dec.typeString(remoteId)
+		// Common confusing case: local interface type, remote concrete type.
+		if ut.base.Kind() == reflect.Interface && remoteId != tInterface {
+			return nil, errors.New("gob: local interface type " + name + " can only be decoded from remote interface type; received concrete type " + remoteType)
+		}
+		return nil, errors.New("gob: decoding into local type " + name + ", received remote type " + remoteType)
+	}
+	op := dec.decOpFor(remoteId, rt, name, make(map[reflect.Type]*decOp))
+	ovfl := errors.New(`value for "` + name + `" out of range`)
+	engine.instr[singletonField] = decInstr{*op, singletonField, nil, ovfl}
+	engine.numInstr = 1
+	return
+}
+
+// compileIgnoreSingle compiles the decoder engine for a non-struct top-level value that will be discarded.
+func (dec *Decoder) compileIgnoreSingle(remoteId typeId) *decEngine {
+	engine := new(decEngine)
+	engine.instr = make([]decInstr, 1) // one item
+	op := dec.decIgnoreOpFor(remoteId, make(map[typeId]*decOp), 0)
+	ovfl := overflow(dec.typeString(remoteId))
+	engine.instr[0] = decInstr{*op, 0, nil, ovfl}
+	engine.numInstr = 1
+	return engine
+}
+
+// compileDec compiles the decoder engine for a value. If the value is not a struct,
+// it calls out to compileSingle.
+func (dec *Decoder) compileDec(remoteId typeId, ut *userTypeInfo) (engine *decEngine, err error) {
+	defer catchError(&err)
+	rt := ut.base
+	srt := rt
+	if srt.Kind() != reflect.Struct || ut.externalDec != 0 {
+		return dec.compileSingle(remoteId, ut)
+	}
+	var wireStruct *structType
+	// Builtin types can come from global pool; the rest must be defined by the decoder.
+	// Also we know we're decoding a struct now, so the client must have sent one.
+	if t, ok := builtinIdToType[remoteId]; ok {
+		wireStruct, _ = t.(*structType)
+	} else {
+		wire := dec.wireType[remoteId]
+		if wire == nil {
+			error_(errBadType)
+		}
+		wireStruct = wire.StructT
+	}
+	if wireStruct == nil {
+		errorf("type mismatch in decoder: want struct type %s; got non-struct", rt)
+	}
+	engine = new(decEngine)
+	engine.instr = make([]decInstr, len(wireStruct.Field))
+	seen := make(map[reflect.Type]*decOp)
+	// Loop over the fields of the wire type.
+	for fieldnum := 0; fieldnum < len(wireStruct.Field); fieldnum++ {
+		wireField := wireStruct.Field[fieldnum]
+		if wireField.Name == "" {
+			errorf("empty name for remote field of type %s", wireStruct.Name)
+		}
+		ovfl := overflow(wireField.Name)
+		// Find the field of the local type with the same name.
+		localField, present := srt.FieldByName(wireField.Name)
+		// TODO(r): anonymous names
+		if !present || !isExported(wireField.Name) {
+			op := dec.decIgnoreOpFor(wireField.Id, make(map[typeId]*decOp), 0)
+			engine.instr[fieldnum] = decInstr{*op, fieldnum, nil, ovfl}
+			continue
+		}
+		if !dec.compatibleType(localField.Type, wireField.Id, make(map[reflect.Type]typeId)) {
+			errorf("wrong type (%s) for received field %s.%s", localField.Type, wireStruct.Name, wireField.Name)
+		}
+		op := dec.decOpFor(wireField.Id, localField.Type, localField.Name, seen)
+		engine.instr[fieldnum] = decInstr{*op, fieldnum, localField.Index, ovfl}
+		engine.numInstr++
+	}
+	return
+}
+
+// getDecEnginePtr returns the engine for the specified type.
+func (dec *Decoder) getDecEnginePtr(remoteId typeId, ut *userTypeInfo) (enginePtr **decEngine, err error) {
+	rt := ut.user
+	decoderMap, ok := dec.decoderCache[rt]
+	if !ok {
+		decoderMap = make(map[typeId]**decEngine)
+		dec.decoderCache[rt] = decoderMap
+	}
+	if enginePtr, ok = decoderMap[remoteId]; !ok {
+		// To handle recursive types, mark this engine as underway before compiling.
+		enginePtr = new(*decEngine)
+		decoderMap[remoteId] = enginePtr
+		*enginePtr, err = dec.compileDec(remoteId, ut)
+		if err != nil {
+			delete(decoderMap, remoteId)
+		}
+	}
+	return
+}
+
+// emptyStruct is the type we compile into when ignoring a struct value.
+type emptyStruct struct{}
+
+var emptyStructType = reflect.TypeOf(emptyStruct{})
+
+// getIgnoreEnginePtr returns the engine for the specified type when the value is to be discarded.
+func (dec *Decoder) getIgnoreEnginePtr(wireId typeId) (enginePtr **decEngine, err error) {
+	var ok bool
+	if enginePtr, ok = dec.ignorerCache[wireId]; !ok {
+		// To handle recursive types, mark this engine as underway before compiling.
+		enginePtr = new(*decEngine)
+		dec.ignorerCache[wireId] = enginePtr
+		wire := dec.wireType[wireId]
+		if wire != nil && wire.StructT != nil {
+			*enginePtr, err = dec.compileDec(wireId, userType(emptyStructType))
+		} else {
+			*enginePtr = dec.compileIgnoreSingle(wireId)
+		}
+		if err != nil {
+			delete(dec.ignorerCache, wireId)
+		}
+	}
+	return
+}
+
+// decodeValue decodes the data stream representing a value and stores it in value.
+func (dec *Decoder) decodeValue(wireId typeId, value reflect.Value) {
+	defer catchError(&dec.err)
+	// If the value is nil, it means we should just ignore this item.
+	if !value.IsValid() {
+		dec.decodeIgnoredValue(wireId)
+		return
+	}
+	// Dereference down to the underlying type.
+	ut := userType(value.Type())
+	base := ut.base
+	var enginePtr **decEngine
+	enginePtr, dec.err = dec.getDecEnginePtr(wireId, ut)
+	if dec.err != nil {
+		return
+	}
+	value = decAlloc(value)
+	engine := *enginePtr
+	if st := base; st.Kind() == reflect.Struct && ut.externalDec == 0 {
+		wt := dec.wireType[wireId]
+		if engine.numInstr == 0 && st.NumField() > 0 &&
+			wt != nil && len(wt.StructT.Field) > 0 {
+			name := base.Name()
+			errorf("type mismatch: no fields matched compiling decoder for %s", name)
+		}
+		dec.decodeStruct(engine, value)
+	} else {
+		dec.decodeSingle(engine, value)
+	}
+}
+
+// decodeIgnoredValue decodes the data stream representing a value of the specified type and discards it.
+func (dec *Decoder) decodeIgnoredValue(wireId typeId) {
+	var enginePtr **decEngine
+	enginePtr, dec.err = dec.getIgnoreEnginePtr(wireId)
+	if dec.err != nil {
+		return
+	}
+	wire := dec.wireType[wireId]
+	if wire != nil && wire.StructT != nil {
+		dec.ignoreStruct(*enginePtr)
+	} else {
+		dec.ignoreSingle(*enginePtr)
+	}
+}
+
+func init() {
+	var iop, uop decOp
+	switch reflect.TypeOf(int(0)).Bits() {
+	case 32:
+		iop = decInt32
+		uop = decUint32
+	case 64:
+		iop = decInt64
+		uop = decUint64
+	default:
+		panic("gob: unknown size of int/uint")
+	}
+	decOpTable[reflect.Int] = iop
+	decOpTable[reflect.Uint] = uop
+
+	// Finally uintptr
+	switch reflect.TypeOf(uintptr(0)).Bits() {
+	case 32:
+		uop = decUint32
+	case 64:
+		uop = decUint64
+	default:
+		panic("gob: unknown size of uintptr")
+	}
+	decOpTable[reflect.Uintptr] = uop
+}
+
+// Gob depends on being able to take the address
+// of zeroed Values it creates, so use this wrapper instead
+// of the standard reflect.Zero.
+// Each call allocates once.
+func allocValue(t reflect.Type) reflect.Value {
+	return reflect.New(t).Elem()
+}
diff --git a/src/encoding/gob/decoder.go b/src/encoding/gob/decoder.go
new file mode 100644
index 0000000..86f54b4
--- /dev/null
+++ b/src/encoding/gob/decoder.go
@@ -0,0 +1,233 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package gob
+
+import (
+	"bufio"
+	"errors"
+	"io"
+	"reflect"
+	"sync"
+)
+
+// tooBig provides a sanity check for sizes; used in several places. Upper limit
+// of is 1GB on 32-bit systems, 8GB on 64-bit, allowing room to grow a little
+// without overflow.
+const tooBig = (1 << 30) << (^uint(0) >> 62)
+
+// A Decoder manages the receipt of type and data information read from the
+// remote side of a connection.  It is safe for concurrent use by multiple
+// goroutines.
+//
+// The Decoder does only basic sanity checking on decoded input sizes,
+// and its limits are not configurable. Take caution when decoding gob data
+// from untrusted sources.
+type Decoder struct {
+	mutex        sync.Mutex                              // each item must be received atomically
+	r            io.Reader                               // source of the data
+	buf          decBuffer                               // buffer for more efficient i/o from r
+	wireType     map[typeId]*wireType                    // map from remote ID to local description
+	decoderCache map[reflect.Type]map[typeId]**decEngine // cache of compiled engines
+	ignorerCache map[typeId]**decEngine                  // ditto for ignored objects
+	freeList     *decoderState                           // list of free decoderStates; avoids reallocation
+	countBuf     []byte                                  // used for decoding integers while parsing messages
+	err          error
+}
+
+// NewDecoder returns a new decoder that reads from the io.Reader.
+// If r does not also implement io.ByteReader, it will be wrapped in a
+// bufio.Reader.
+func NewDecoder(r io.Reader) *Decoder {
+	dec := new(Decoder)
+	// We use the ability to read bytes as a plausible surrogate for buffering.
+	if _, ok := r.(io.ByteReader); !ok {
+		r = bufio.NewReader(r)
+	}
+	dec.r = r
+	dec.wireType = make(map[typeId]*wireType)
+	dec.decoderCache = make(map[reflect.Type]map[typeId]**decEngine)
+	dec.ignorerCache = make(map[typeId]**decEngine)
+	dec.countBuf = make([]byte, 9) // counts may be uint64s (unlikely!), require 9 bytes
+
+	return dec
+}
+
+// recvType loads the definition of a type.
+func (dec *Decoder) recvType(id typeId) {
+	// Have we already seen this type? That's an error
+	if id < firstUserId || dec.wireType[id] != nil {
+		dec.err = errors.New("gob: duplicate type received")
+		return
+	}
+
+	// Type:
+	wire := new(wireType)
+	dec.decodeValue(tWireType, reflect.ValueOf(wire))
+	if dec.err != nil {
+		return
+	}
+	// Remember we've seen this type.
+	dec.wireType[id] = wire
+}
+
+var errBadCount = errors.New("invalid message length")
+
+// recvMessage reads the next count-delimited item from the input. It is the converse
+// of Encoder.writeMessage. It returns false on EOF or other error reading the message.
+func (dec *Decoder) recvMessage() bool {
+	// Read a count.
+	nbytes, _, err := decodeUintReader(dec.r, dec.countBuf)
+	if err != nil {
+		dec.err = err
+		return false
+	}
+	if nbytes >= tooBig {
+		dec.err = errBadCount
+		return false
+	}
+	dec.readMessage(int(nbytes))
+	return dec.err == nil
+}
+
+// readMessage reads the next nbytes bytes from the input.
+func (dec *Decoder) readMessage(nbytes int) {
+	if dec.buf.Len() != 0 {
+		// The buffer should always be empty now.
+		panic("non-empty decoder buffer")
+	}
+	// Read the data
+	dec.buf.Size(nbytes)
+	_, dec.err = io.ReadFull(dec.r, dec.buf.Bytes())
+	if dec.err == io.EOF {
+		dec.err = io.ErrUnexpectedEOF
+	}
+}
+
+// toInt turns an encoded uint64 into an int, according to the marshaling rules.
+func toInt(x uint64) int64 {
+	i := int64(x >> 1)
+	if x&1 != 0 {
+		i = ^i
+	}
+	return i
+}
+
+func (dec *Decoder) nextInt() int64 {
+	n, _, err := decodeUintReader(&dec.buf, dec.countBuf)
+	if err != nil {
+		dec.err = err
+	}
+	return toInt(n)
+}
+
+func (dec *Decoder) nextUint() uint64 {
+	n, _, err := decodeUintReader(&dec.buf, dec.countBuf)
+	if err != nil {
+		dec.err = err
+	}
+	return n
+}
+
+// decodeTypeSequence parses:
+// TypeSequence
+//	(TypeDefinition DelimitedTypeDefinition*)?
+// and returns the type id of the next value. It returns -1 at
+// EOF.  Upon return, the remainder of dec.buf is the value to be
+// decoded. If this is an interface value, it can be ignored by
+// resetting that buffer.
+func (dec *Decoder) decodeTypeSequence(isInterface bool) typeId {
+	firstMessage := true
+	for dec.err == nil {
+		if dec.buf.Len() == 0 {
+			if !dec.recvMessage() {
+				// We can only return io.EOF if the input was empty.
+				// If we read one or more type spec messages,
+				// require a data item message to follow.
+				// If we hit an EOF before that, then give ErrUnexpectedEOF.
+				if !firstMessage && dec.err == io.EOF {
+					dec.err = io.ErrUnexpectedEOF
+				}
+				break
+			}
+		}
+		// Receive a type id.
+		id := typeId(dec.nextInt())
+		if id >= 0 {
+			// Value follows.
+			return id
+		}
+		// Type definition for (-id) follows.
+		dec.recvType(-id)
+		if dec.err != nil {
+			break
+		}
+		// When decoding an interface, after a type there may be a
+		// DelimitedValue still in the buffer. Skip its count.
+		// (Alternatively, the buffer is empty and the byte count
+		// will be absorbed by recvMessage.)
+		if dec.buf.Len() > 0 {
+			if !isInterface {
+				dec.err = errors.New("extra data in buffer")
+				break
+			}
+			dec.nextUint()
+		}
+		firstMessage = false
+	}
+	return -1
+}
+
+// Decode reads the next value from the input stream and stores
+// it in the data represented by the empty interface value.
+// If e is nil, the value will be discarded. Otherwise,
+// the value underlying e must be a pointer to the
+// correct type for the next data item received.
+// If the input is at EOF, Decode returns io.EOF and
+// does not modify e.
+func (dec *Decoder) Decode(e any) error {
+	if e == nil {
+		return dec.DecodeValue(reflect.Value{})
+	}
+	value := reflect.ValueOf(e)
+	// If e represents a value as opposed to a pointer, the answer won't
+	// get back to the caller. Make sure it's a pointer.
+	if value.Type().Kind() != reflect.Pointer {
+		dec.err = errors.New("gob: attempt to decode into a non-pointer")
+		return dec.err
+	}
+	return dec.DecodeValue(value)
+}
+
+// DecodeValue reads the next value from the input stream.
+// If v is the zero reflect.Value (v.Kind() == Invalid), DecodeValue discards the value.
+// Otherwise, it stores the value into v. In that case, v must represent
+// a non-nil pointer to data or be an assignable reflect.Value (v.CanSet())
+// If the input is at EOF, DecodeValue returns io.EOF and
+// does not modify v.
+func (dec *Decoder) DecodeValue(v reflect.Value) error {
+	if v.IsValid() {
+		if v.Kind() == reflect.Pointer && !v.IsNil() {
+			// That's okay, we'll store through the pointer.
+		} else if !v.CanSet() {
+			return errors.New("gob: DecodeValue of unassignable value")
+		}
+	}
+	// Make sure we're single-threaded through here.
+	dec.mutex.Lock()
+	defer dec.mutex.Unlock()
+
+	dec.buf.Reset() // In case data lingers from previous invocation.
+	dec.err = nil
+	id := dec.decodeTypeSequence(false)
+	if dec.err == nil {
+		dec.decodeValue(id, v)
+	}
+	return dec.err
+}
+
+// If debug.go is compiled into the program, debugFunc prints a human-readable
+// representation of the gob data read from r by calling that file's Debug function.
+// Otherwise it is nil.
+var debugFunc func(io.Reader)
diff --git a/src/encoding/gob/doc.go b/src/encoding/gob/doc.go
new file mode 100644
index 0000000..c765707
--- /dev/null
+++ b/src/encoding/gob/doc.go
@@ -0,0 +1,415 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+/*
+Package gob manages streams of gobs - binary values exchanged between an
+Encoder (transmitter) and a Decoder (receiver). A typical use is transporting
+arguments and results of remote procedure calls (RPCs) such as those provided by
+package "net/rpc".
+
+The implementation compiles a custom codec for each data type in the stream and
+is most efficient when a single Encoder is used to transmit a stream of values,
+amortizing the cost of compilation.
+
+Basics
+
+A stream of gobs is self-describing. Each data item in the stream is preceded by
+a specification of its type, expressed in terms of a small set of predefined
+types. Pointers are not transmitted, but the things they point to are
+transmitted; that is, the values are flattened. Nil pointers are not permitted,
+as they have no value. Recursive types work fine, but
+recursive values (data with cycles) are problematic. This may change.
+
+To use gobs, create an Encoder and present it with a series of data items as
+values or addresses that can be dereferenced to values. The Encoder makes sure
+all type information is sent before it is needed. At the receive side, a
+Decoder retrieves values from the encoded stream and unpacks them into local
+variables.
+
+Types and Values
+
+The source and destination values/types need not correspond exactly. For structs,
+fields (identified by name) that are in the source but absent from the receiving
+variable will be ignored. Fields that are in the receiving variable but missing
+from the transmitted type or value will be ignored in the destination. If a field
+with the same name is present in both, their types must be compatible. Both the
+receiver and transmitter will do all necessary indirection and dereferencing to
+convert between gobs and actual Go values. For instance, a gob type that is
+schematically,
+
+	struct { A, B int }
+
+can be sent from or received into any of these Go types:
+
+	struct { A, B int }	// the same
+	*struct { A, B int }	// extra indirection of the struct
+	struct { *A, **B int }	// extra indirection of the fields
+	struct { A, B int64 }	// different concrete value type; see below
+
+It may also be received into any of these:
+
+	struct { A, B int }	// the same
+	struct { B, A int }	// ordering doesn't matter; matching is by name
+	struct { A, B, C int }	// extra field (C) ignored
+	struct { B int }	// missing field (A) ignored; data will be dropped
+	struct { B, C int }	// missing field (A) ignored; extra field (C) ignored.
+
+Attempting to receive into these types will draw a decode error:
+
+	struct { A int; B uint }	// change of signedness for B
+	struct { A int; B float }	// change of type for B
+	struct { }			// no field names in common
+	struct { C, D int }		// no field names in common
+
+Integers are transmitted two ways: arbitrary precision signed integers or
+arbitrary precision unsigned integers. There is no int8, int16 etc.
+discrimination in the gob format; there are only signed and unsigned integers. As
+described below, the transmitter sends the value in a variable-length encoding;
+the receiver accepts the value and stores it in the destination variable.
+Floating-point numbers are always sent using IEEE-754 64-bit precision (see
+below).
+
+Signed integers may be received into any signed integer variable: int, int16, etc.;
+unsigned integers may be received into any unsigned integer variable; and floating
+point values may be received into any floating point variable. However,
+the destination variable must be able to represent the value or the decode
+operation will fail.
+
+Structs, arrays and slices are also supported. Structs encode and decode only
+exported fields. Strings and arrays of bytes are supported with a special,
+efficient representation (see below). When a slice is decoded, if the existing
+slice has capacity the slice will be extended in place; if not, a new array is
+allocated. Regardless, the length of the resulting slice reports the number of
+elements decoded.
+
+In general, if allocation is required, the decoder will allocate memory. If not,
+it will update the destination variables with values read from the stream. It does
+not initialize them first, so if the destination is a compound value such as a
+map, struct, or slice, the decoded values will be merged elementwise into the
+existing variables.
+
+Functions and channels will not be sent in a gob. Attempting to encode such a value
+at the top level will fail. A struct field of chan or func type is treated exactly
+like an unexported field and is ignored.
+
+Gob can encode a value of any type implementing the GobEncoder or
+encoding.BinaryMarshaler interfaces by calling the corresponding method,
+in that order of preference.
+
+Gob can decode a value of any type implementing the GobDecoder or
+encoding.BinaryUnmarshaler interfaces by calling the corresponding method,
+again in that order of preference.
+
+Encoding Details
+
+This section documents the encoding, details that are not important for most
+users. Details are presented bottom-up.
+
+An unsigned integer is sent one of two ways. If it is less than 128, it is sent
+as a byte with that value. Otherwise it is sent as a minimal-length big-endian
+(high byte first) byte stream holding the value, preceded by one byte holding the
+byte count, negated. Thus 0 is transmitted as (00), 7 is transmitted as (07) and
+256 is transmitted as (FE 01 00).
+
+A boolean is encoded within an unsigned integer: 0 for false, 1 for true.
+
+A signed integer, i, is encoded within an unsigned integer, u. Within u, bits 1
+upward contain the value; bit 0 says whether they should be complemented upon
+receipt. The encode algorithm looks like this:
+
+	var u uint
+	if i < 0 {
+		u = (^uint(i) << 1) | 1 // complement i, bit 0 is 1
+	} else {
+		u = (uint(i) << 1) // do not complement i, bit 0 is 0
+	}
+	encodeUnsigned(u)
+
+The low bit is therefore analogous to a sign bit, but making it the complement bit
+instead guarantees that the largest negative integer is not a special case. For
+example, -129=^128=(^256>>1) encodes as (FE 01 01).
+
+Floating-point numbers are always sent as a representation of a float64 value.
+That value is converted to a uint64 using math.Float64bits. The uint64 is then
+byte-reversed and sent as a regular unsigned integer. The byte-reversal means the
+exponent and high-precision part of the mantissa go first. Since the low bits are
+often zero, this can save encoding bytes. For instance, 17.0 is encoded in only
+three bytes (FE 31 40).
+
+Strings and slices of bytes are sent as an unsigned count followed by that many
+uninterpreted bytes of the value.
+
+All other slices and arrays are sent as an unsigned count followed by that many
+elements using the standard gob encoding for their type, recursively.
+
+Maps are sent as an unsigned count followed by that many key, element
+pairs. Empty but non-nil maps are sent, so if the receiver has not allocated
+one already, one will always be allocated on receipt unless the transmitted map
+is nil and not at the top level.
+
+In slices and arrays, as well as maps, all elements, even zero-valued elements,
+are transmitted, even if all the elements are zero.
+
+Structs are sent as a sequence of (field number, field value) pairs. The field
+value is sent using the standard gob encoding for its type, recursively. If a
+field has the zero value for its type (except for arrays; see above), it is omitted
+from the transmission. The field number is defined by the type of the encoded
+struct: the first field of the encoded type is field 0, the second is field 1,
+etc. When encoding a value, the field numbers are delta encoded for efficiency
+and the fields are always sent in order of increasing field number; the deltas are
+therefore unsigned. The initialization for the delta encoding sets the field
+number to -1, so an unsigned integer field 0 with value 7 is transmitted as unsigned
+delta = 1, unsigned value = 7 or (01 07). Finally, after all the fields have been
+sent a terminating mark denotes the end of the struct. That mark is a delta=0
+value, which has representation (00).
+
+Interface types are not checked for compatibility; all interface types are
+treated, for transmission, as members of a single "interface" type, analogous to
+int or []byte - in effect they're all treated as interface{}. Interface values
+are transmitted as a string identifying the concrete type being sent (a name
+that must be pre-defined by calling Register), followed by a byte count of the
+length of the following data (so the value can be skipped if it cannot be
+stored), followed by the usual encoding of concrete (dynamic) value stored in
+the interface value. (A nil interface value is identified by the empty string
+and transmits no value.) Upon receipt, the decoder verifies that the unpacked
+concrete item satisfies the interface of the receiving variable.
+
+If a value is passed to Encode and the type is not a struct (or pointer to struct,
+etc.), for simplicity of processing it is represented as a struct of one field.
+The only visible effect of this is to encode a zero byte after the value, just as
+after the last field of an encoded struct, so that the decode algorithm knows when
+the top-level value is complete.
+
+The representation of types is described below. When a type is defined on a given
+connection between an Encoder and Decoder, it is assigned a signed integer type
+id. When Encoder.Encode(v) is called, it makes sure there is an id assigned for
+the type of v and all its elements and then it sends the pair (typeid, encoded-v)
+where typeid is the type id of the encoded type of v and encoded-v is the gob
+encoding of the value v.
+
+To define a type, the encoder chooses an unused, positive type id and sends the
+pair (-type id, encoded-type) where encoded-type is the gob encoding of a wireType
+description, constructed from these types:
+
+	type wireType struct {
+		ArrayT           *ArrayType
+		SliceT           *SliceType
+		StructT          *StructType
+		MapT             *MapType
+		GobEncoderT      *gobEncoderType
+		BinaryMarshalerT *gobEncoderType
+		TextMarshalerT   *gobEncoderType
+
+	}
+	type arrayType struct {
+		CommonType
+		Elem typeId
+		Len  int
+	}
+	type CommonType struct {
+		Name string // the name of the struct type
+		Id  int    // the id of the type, repeated so it's inside the type
+	}
+	type sliceType struct {
+		CommonType
+		Elem typeId
+	}
+	type structType struct {
+		CommonType
+		Field []*fieldType // the fields of the struct.
+	}
+	type fieldType struct {
+		Name string // the name of the field.
+		Id   int    // the type id of the field, which must be already defined
+	}
+	type mapType struct {
+		CommonType
+		Key  typeId
+		Elem typeId
+	}
+	type gobEncoderType struct {
+		CommonType
+	}
+
+If there are nested type ids, the types for all inner type ids must be defined
+before the top-level type id is used to describe an encoded-v.
+
+For simplicity in setup, the connection is defined to understand these types a
+priori, as well as the basic gob types int, uint, etc. Their ids are:
+
+	bool        1
+	int         2
+	uint        3
+	float       4
+	[]byte      5
+	string      6
+	complex     7
+	interface   8
+	// gap for reserved ids.
+	WireType    16
+	ArrayType   17
+	CommonType  18
+	SliceType   19
+	StructType  20
+	FieldType   21
+	// 22 is slice of fieldType.
+	MapType     23
+
+Finally, each message created by a call to Encode is preceded by an encoded
+unsigned integer count of the number of bytes remaining in the message. After
+the initial type name, interface values are wrapped the same way; in effect, the
+interface value acts like a recursive invocation of Encode.
+
+In summary, a gob stream looks like
+
+	(byteCount (-type id, encoding of a wireType)* (type id, encoding of a value))*
+
+where * signifies zero or more repetitions and the type id of a value must
+be predefined or be defined before the value in the stream.
+
+Compatibility: Any future changes to the package will endeavor to maintain
+compatibility with streams encoded using previous versions. That is, any released
+version of this package should be able to decode data written with any previously
+released version, subject to issues such as security fixes. See the Go compatibility
+document for background: https://golang.org/doc/go1compat
+
+See "Gobs of data" for a design discussion of the gob wire format:
+https://blog.golang.org/gobs-of-data
+*/
+package gob
+
+/*
+Grammar:
+
+Tokens starting with a lower case letter are terminals; int(n)
+and uint(n) represent the signed/unsigned encodings of the value n.
+
+GobStream:
+	DelimitedMessage*
+DelimitedMessage:
+	uint(lengthOfMessage) Message
+Message:
+	TypeSequence TypedValue
+TypeSequence
+	(TypeDefinition DelimitedTypeDefinition*)?
+DelimitedTypeDefinition:
+	uint(lengthOfTypeDefinition) TypeDefinition
+TypedValue:
+	int(typeId) Value
+TypeDefinition:
+	int(-typeId) encodingOfWireType
+Value:
+	SingletonValue | StructValue
+SingletonValue:
+	uint(0) FieldValue
+FieldValue:
+	builtinValue | ArrayValue | MapValue | SliceValue | StructValue | InterfaceValue
+InterfaceValue:
+	NilInterfaceValue | NonNilInterfaceValue
+NilInterfaceValue:
+	uint(0)
+NonNilInterfaceValue:
+	ConcreteTypeName TypeSequence InterfaceContents
+ConcreteTypeName:
+	uint(lengthOfName) [already read=n] name
+InterfaceContents:
+	int(concreteTypeId) DelimitedValue
+DelimitedValue:
+	uint(length) Value
+ArrayValue:
+	uint(n) FieldValue*n [n elements]
+MapValue:
+	uint(n) (FieldValue FieldValue)*n  [n (key, value) pairs]
+SliceValue:
+	uint(n) FieldValue*n [n elements]
+StructValue:
+	(uint(fieldDelta) FieldValue)*
+*/
+
+/*
+For implementers and the curious, here is an encoded example. Given
+	type Point struct {X, Y int}
+and the value
+	p := Point{22, 33}
+the bytes transmitted that encode p will be:
+	1f ff 81 03 01 01 05 50 6f 69 6e 74 01 ff 82 00
+	01 02 01 01 58 01 04 00 01 01 59 01 04 00 00 00
+	07 ff 82 01 2c 01 42 00
+They are determined as follows.
+
+Since this is the first transmission of type Point, the type descriptor
+for Point itself must be sent before the value. This is the first type
+we've sent on this Encoder, so it has type id 65 (0 through 64 are
+reserved).
+
+	1f	// This item (a type descriptor) is 31 bytes long.
+	ff 81	// The negative of the id for the type we're defining, -65.
+		// This is one byte (indicated by FF = -1) followed by
+		// ^-65<<1 | 1. The low 1 bit signals to complement the
+		// rest upon receipt.
+
+	// Now we send a type descriptor, which is itself a struct (wireType).
+	// The type of wireType itself is known (it's built in, as is the type of
+	// all its components), so we just need to send a *value* of type wireType
+	// that represents type "Point".
+	// Here starts the encoding of that value.
+	// Set the field number implicitly to -1; this is done at the beginning
+	// of every struct, including nested structs.
+	03	// Add 3 to field number; now 2 (wireType.structType; this is a struct).
+		// structType starts with an embedded CommonType, which appears
+		// as a regular structure here too.
+	01	// add 1 to field number (now 0); start of embedded CommonType.
+	01	// add 1 to field number (now 0, the name of the type)
+	05	// string is (unsigned) 5 bytes long
+	50 6f 69 6e 74	// wireType.structType.CommonType.name = "Point"
+	01	// add 1 to field number (now 1, the id of the type)
+	ff 82	// wireType.structType.CommonType._id = 65
+	00	// end of embedded wiretype.structType.CommonType struct
+	01	// add 1 to field number (now 1, the field array in wireType.structType)
+	02	// There are two fields in the type (len(structType.field))
+	01	// Start of first field structure; add 1 to get field number 0: field[0].name
+	01	// 1 byte
+	58	// structType.field[0].name = "X"
+	01	// Add 1 to get field number 1: field[0].id
+	04	// structType.field[0].typeId is 2 (signed int).
+	00	// End of structType.field[0]; start structType.field[1]; set field number to -1.
+	01	// Add 1 to get field number 0: field[1].name
+	01	// 1 byte
+	59	// structType.field[1].name = "Y"
+	01	// Add 1 to get field number 1: field[1].id
+	04	// struct.Type.field[1].typeId is 2 (signed int).
+	00	// End of structType.field[1]; end of structType.field.
+	00	// end of wireType.structType structure
+	00	// end of wireType structure
+
+Now we can send the Point value. Again the field number resets to -1:
+
+	07	// this value is 7 bytes long
+	ff 82	// the type number, 65 (1 byte (-FF) followed by 65<<1)
+	01	// add one to field number, yielding field 0
+	2c	// encoding of signed "22" (0x2c = 44 = 22<<1); Point.x = 22
+	01	// add one to field number, yielding field 1
+	42	// encoding of signed "33" (0x42 = 66 = 33<<1); Point.y = 33
+	00	// end of structure
+
+The type encoding is long and fairly intricate but we send it only once.
+If p is transmitted a second time, the type is already known so the
+output will be just:
+
+	07 ff 82 01 2c 01 42 00
+
+A single non-struct value at top level is transmitted like a field with
+delta tag 0. For instance, a signed integer with value 3 presented as
+the argument to Encode will emit:
+
+	03 04 00 06
+
+Which represents:
+
+	03	// this value is 3 bytes long
+	04	// the type number, 2, represents an integer
+	00	// tag delta 0
+	06	// value 3
+
+*/
diff --git a/src/encoding/gob/dump.go b/src/encoding/gob/dump.go
new file mode 100644
index 0000000..f4b1beb
--- /dev/null
+++ b/src/encoding/gob/dump.go
@@ -0,0 +1,29 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build ignore
+
+package main
+
+// Need to compile package gob with debug.go to build this program.
+// See comments in debug.go for how to do this.
+
+import (
+	"encoding/gob"
+	"fmt"
+	"os"
+)
+
+func main() {
+	var err error
+	file := os.Stdin
+	if len(os.Args) > 1 {
+		file, err = os.Open(os.Args[1])
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "dump: %s\n", err)
+			os.Exit(1)
+		}
+	}
+	gob.Debug(file)
+}
diff --git a/src/encoding/gob/enc_helpers.go b/src/encoding/gob/enc_helpers.go
new file mode 100644
index 0000000..c3b4ca8
--- /dev/null
+++ b/src/encoding/gob/enc_helpers.go
@@ -0,0 +1,414 @@
+// Code generated by go run encgen.go -output enc_helpers.go; DO NOT EDIT.
+
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package gob
+
+import (
+	"reflect"
+)
+
+var encArrayHelper = map[reflect.Kind]encHelper{
+	reflect.Bool:       encBoolArray,
+	reflect.Complex64:  encComplex64Array,
+	reflect.Complex128: encComplex128Array,
+	reflect.Float32:    encFloat32Array,
+	reflect.Float64:    encFloat64Array,
+	reflect.Int:        encIntArray,
+	reflect.Int16:      encInt16Array,
+	reflect.Int32:      encInt32Array,
+	reflect.Int64:      encInt64Array,
+	reflect.Int8:       encInt8Array,
+	reflect.String:     encStringArray,
+	reflect.Uint:       encUintArray,
+	reflect.Uint16:     encUint16Array,
+	reflect.Uint32:     encUint32Array,
+	reflect.Uint64:     encUint64Array,
+	reflect.Uintptr:    encUintptrArray,
+}
+
+var encSliceHelper = map[reflect.Kind]encHelper{
+	reflect.Bool:       encBoolSlice,
+	reflect.Complex64:  encComplex64Slice,
+	reflect.Complex128: encComplex128Slice,
+	reflect.Float32:    encFloat32Slice,
+	reflect.Float64:    encFloat64Slice,
+	reflect.Int:        encIntSlice,
+	reflect.Int16:      encInt16Slice,
+	reflect.Int32:      encInt32Slice,
+	reflect.Int64:      encInt64Slice,
+	reflect.Int8:       encInt8Slice,
+	reflect.String:     encStringSlice,
+	reflect.Uint:       encUintSlice,
+	reflect.Uint16:     encUint16Slice,
+	reflect.Uint32:     encUint32Slice,
+	reflect.Uint64:     encUint64Slice,
+	reflect.Uintptr:    encUintptrSlice,
+}
+
+func encBoolArray(state *encoderState, v reflect.Value) bool {
+	// Can only slice if it is addressable.
+	if !v.CanAddr() {
+		return false
+	}
+	return encBoolSlice(state, v.Slice(0, v.Len()))
+}
+
+func encBoolSlice(state *encoderState, v reflect.Value) bool {
+	slice, ok := v.Interface().([]bool)
+	if !ok {
+		// It is kind bool but not type bool. TODO: We can handle this unsafely.
+		return false
+	}
+	for _, x := range slice {
+		if x != false || state.sendZero {
+			if x {
+				state.encodeUint(1)
+			} else {
+				state.encodeUint(0)
+			}
+		}
+	}
+	return true
+}
+
+func encComplex64Array(state *encoderState, v reflect.Value) bool {
+	// Can only slice if it is addressable.
+	if !v.CanAddr() {
+		return false
+	}
+	return encComplex64Slice(state, v.Slice(0, v.Len()))
+}
+
+func encComplex64Slice(state *encoderState, v reflect.Value) bool {
+	slice, ok := v.Interface().([]complex64)
+	if !ok {
+		// It is kind complex64 but not type complex64. TODO: We can handle this unsafely.
+		return false
+	}
+	for _, x := range slice {
+		if x != 0+0i || state.sendZero {
+			rpart := floatBits(float64(real(x)))
+			ipart := floatBits(float64(imag(x)))
+			state.encodeUint(rpart)
+			state.encodeUint(ipart)
+		}
+	}
+	return true
+}
+
+func encComplex128Array(state *encoderState, v reflect.Value) bool {
+	// Can only slice if it is addressable.
+	if !v.CanAddr() {
+		return false
+	}
+	return encComplex128Slice(state, v.Slice(0, v.Len()))
+}
+
+func encComplex128Slice(state *encoderState, v reflect.Value) bool {
+	slice, ok := v.Interface().([]complex128)
+	if !ok {
+		// It is kind complex128 but not type complex128. TODO: We can handle this unsafely.
+		return false
+	}
+	for _, x := range slice {
+		if x != 0+0i || state.sendZero {
+			rpart := floatBits(real(x))
+			ipart := floatBits(imag(x))
+			state.encodeUint(rpart)
+			state.encodeUint(ipart)
+		}
+	}
+	return true
+}
+
+func encFloat32Array(state *encoderState, v reflect.Value) bool {
+	// Can only slice if it is addressable.
+	if !v.CanAddr() {
+		return false
+	}
+	return encFloat32Slice(state, v.Slice(0, v.Len()))
+}
+
+func encFloat32Slice(state *encoderState, v reflect.Value) bool {
+	slice, ok := v.Interface().([]float32)
+	if !ok {
+		// It is kind float32 but not type float32. TODO: We can handle this unsafely.
+		return false
+	}
+	for _, x := range slice {
+		if x != 0 || state.sendZero {
+			bits := floatBits(float64(x))
+			state.encodeUint(bits)
+		}
+	}
+	return true
+}
+
+func encFloat64Array(state *encoderState, v reflect.Value) bool {
+	// Can only slice if it is addressable.
+	if !v.CanAddr() {
+		return false
+	}
+	return encFloat64Slice(state, v.Slice(0, v.Len()))
+}
+
+func encFloat64Slice(state *encoderState, v reflect.Value) bool {
+	slice, ok := v.Interface().([]float64)
+	if !ok {
+		// It is kind float64 but not type float64. TODO: We can handle this unsafely.
+		return false
+	}
+	for _, x := range slice {
+		if x != 0 || state.sendZero {
+			bits := floatBits(x)
+			state.encodeUint(bits)
+		}
+	}
+	return true
+}
+
+func encIntArray(state *encoderState, v reflect.Value) bool {
+	// Can only slice if it is addressable.
+	if !v.CanAddr() {
+		return false
+	}
+	return encIntSlice(state, v.Slice(0, v.Len()))
+}
+
+func encIntSlice(state *encoderState, v reflect.Value) bool {
+	slice, ok := v.Interface().([]int)
+	if !ok {
+		// It is kind int but not type int. TODO: We can handle this unsafely.
+		return false
+	}
+	for _, x := range slice {
+		if x != 0 || state.sendZero {
+			state.encodeInt(int64(x))
+		}
+	}
+	return true
+}
+
+func encInt16Array(state *encoderState, v reflect.Value) bool {
+	// Can only slice if it is addressable.
+	if !v.CanAddr() {
+		return false
+	}
+	return encInt16Slice(state, v.Slice(0, v.Len()))
+}
+
+func encInt16Slice(state *encoderState, v reflect.Value) bool {
+	slice, ok := v.Interface().([]int16)
+	if !ok {
+		// It is kind int16 but not type int16. TODO: We can handle this unsafely.
+		return false
+	}
+	for _, x := range slice {
+		if x != 0 || state.sendZero {
+			state.encodeInt(int64(x))
+		}
+	}
+	return true
+}
+
+func encInt32Array(state *encoderState, v reflect.Value) bool {
+	// Can only slice if it is addressable.
+	if !v.CanAddr() {
+		return false
+	}
+	return encInt32Slice(state, v.Slice(0, v.Len()))
+}
+
+func encInt32Slice(state *encoderState, v reflect.Value) bool {
+	slice, ok := v.Interface().([]int32)
+	if !ok {
+		// It is kind int32 but not type int32. TODO: We can handle this unsafely.
+		return false
+	}
+	for _, x := range slice {
+		if x != 0 || state.sendZero {
+			state.encodeInt(int64(x))
+		}
+	}
+	return true
+}
+
+func encInt64Array(state *encoderState, v reflect.Value) bool {
+	// Can only slice if it is addressable.
+	if !v.CanAddr() {
+		return false
+	}
+	return encInt64Slice(state, v.Slice(0, v.Len()))
+}
+
+func encInt64Slice(state *encoderState, v reflect.Value) bool {
+	slice, ok := v.Interface().([]int64)
+	if !ok {
+		// It is kind int64 but not type int64. TODO: We can handle this unsafely.
+		return false
+	}
+	for _, x := range slice {
+		if x != 0 || state.sendZero {
+			state.encodeInt(x)
+		}
+	}
+	return true
+}
+
+func encInt8Array(state *encoderState, v reflect.Value) bool {
+	// Can only slice if it is addressable.
+	if !v.CanAddr() {
+		return false
+	}
+	return encInt8Slice(state, v.Slice(0, v.Len()))
+}
+
+func encInt8Slice(state *encoderState, v reflect.Value) bool {
+	slice, ok := v.Interface().([]int8)
+	if !ok {
+		// It is kind int8 but not type int8. TODO: We can handle this unsafely.
+		return false
+	}
+	for _, x := range slice {
+		if x != 0 || state.sendZero {
+			state.encodeInt(int64(x))
+		}
+	}
+	return true
+}
+
+func encStringArray(state *encoderState, v reflect.Value) bool {
+	// Can only slice if it is addressable.
+	if !v.CanAddr() {
+		return false
+	}
+	return encStringSlice(state, v.Slice(0, v.Len()))
+}
+
+func encStringSlice(state *encoderState, v reflect.Value) bool {
+	slice, ok := v.Interface().([]string)
+	if !ok {
+		// It is kind string but not type string. TODO: We can handle this unsafely.
+		return false
+	}
+	for _, x := range slice {
+		if x != "" || state.sendZero {
+			state.encodeUint(uint64(len(x)))
+			state.b.WriteString(x)
+		}
+	}
+	return true
+}
+
+func encUintArray(state *encoderState, v reflect.Value) bool {
+	// Can only slice if it is addressable.
+	if !v.CanAddr() {
+		return false
+	}
+	return encUintSlice(state, v.Slice(0, v.Len()))
+}
+
+func encUintSlice(state *encoderState, v reflect.Value) bool {
+	slice, ok := v.Interface().([]uint)
+	if !ok {
+		// It is kind uint but not type uint. TODO: We can handle this unsafely.
+		return false
+	}
+	for _, x := range slice {
+		if x != 0 || state.sendZero {
+			state.encodeUint(uint64(x))
+		}
+	}
+	return true
+}
+
+func encUint16Array(state *encoderState, v reflect.Value) bool {
+	// Can only slice if it is addressable.
+	if !v.CanAddr() {
+		return false
+	}
+	return encUint16Slice(state, v.Slice(0, v.Len()))
+}
+
+func encUint16Slice(state *encoderState, v reflect.Value) bool {
+	slice, ok := v.Interface().([]uint16)
+	if !ok {
+		// It is kind uint16 but not type uint16. TODO: We can handle this unsafely.
+		return false
+	}
+	for _, x := range slice {
+		if x != 0 || state.sendZero {
+			state.encodeUint(uint64(x))
+		}
+	}
+	return true
+}
+
+func encUint32Array(state *encoderState, v reflect.Value) bool {
+	// Can only slice if it is addressable.
+	if !v.CanAddr() {
+		return false
+	}
+	return encUint32Slice(state, v.Slice(0, v.Len()))
+}
+
+func encUint32Slice(state *encoderState, v reflect.Value) bool {
+	slice, ok := v.Interface().([]uint32)
+	if !ok {
+		// It is kind uint32 but not type uint32. TODO: We can handle this unsafely.
+		return false
+	}
+	for _, x := range slice {
+		if x != 0 || state.sendZero {
+			state.encodeUint(uint64(x))
+		}
+	}
+	return true
+}
+
+func encUint64Array(state *encoderState, v reflect.Value) bool {
+	// Can only slice if it is addressable.
+	if !v.CanAddr() {
+		return false
+	}
+	return encUint64Slice(state, v.Slice(0, v.Len()))
+}
+
+func encUint64Slice(state *encoderState, v reflect.Value) bool {
+	slice, ok := v.Interface().([]uint64)
+	if !ok {
+		// It is kind uint64 but not type uint64. TODO: We can handle this unsafely.
+		return false
+	}
+	for _, x := range slice {
+		if x != 0 || state.sendZero {
+			state.encodeUint(x)
+		}
+	}
+	return true
+}
+
+func encUintptrArray(state *encoderState, v reflect.Value) bool {
+	// Can only slice if it is addressable.
+	if !v.CanAddr() {
+		return false
+	}
+	return encUintptrSlice(state, v.Slice(0, v.Len()))
+}
+
+func encUintptrSlice(state *encoderState, v reflect.Value) bool {
+	slice, ok := v.Interface().([]uintptr)
+	if !ok {
+		// It is kind uintptr but not type uintptr. TODO: We can handle this unsafely.
+		return false
+	}
+	for _, x := range slice {
+		if x != 0 || state.sendZero {
+			state.encodeUint(uint64(x))
+		}
+	}
+	return true
+}
diff --git a/src/encoding/gob/encgen.go b/src/encoding/gob/encgen.go
new file mode 100644
index 0000000..e5f6878
--- /dev/null
+++ b/src/encoding/gob/encgen.go
@@ -0,0 +1,220 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build ignore
+
+// encgen writes the helper functions for encoding. Intended to be
+// used with go generate; see the invocation in encode.go.
+
+// TODO: We could do more by being unsafe. Add a -unsafe flag?
+
+package main
+
+import (
+	"bytes"
+	"flag"
+	"fmt"
+	"go/format"
+	"log"
+	"os"
+)
+
+var output = flag.String("output", "enc_helpers.go", "file name to write")
+
+type Type struct {
+	lower   string
+	upper   string
+	zero    string
+	encoder string
+}
+
+var types = []Type{
+	{
+		"bool",
+		"Bool",
+		"false",
+		`if x {
+			state.encodeUint(1)
+		} else {
+			state.encodeUint(0)
+		}`,
+	},
+	{
+		"complex64",
+		"Complex64",
+		"0+0i",
+		`rpart := floatBits(float64(real(x)))
+		ipart := floatBits(float64(imag(x)))
+		state.encodeUint(rpart)
+		state.encodeUint(ipart)`,
+	},
+	{
+		"complex128",
+		"Complex128",
+		"0+0i",
+		`rpart := floatBits(real(x))
+		ipart := floatBits(imag(x))
+		state.encodeUint(rpart)
+		state.encodeUint(ipart)`,
+	},
+	{
+		"float32",
+		"Float32",
+		"0",
+		`bits := floatBits(float64(x))
+		state.encodeUint(bits)`,
+	},
+	{
+		"float64",
+		"Float64",
+		"0",
+		`bits := floatBits(x)
+		state.encodeUint(bits)`,
+	},
+	{
+		"int",
+		"Int",
+		"0",
+		`state.encodeInt(int64(x))`,
+	},
+	{
+		"int16",
+		"Int16",
+		"0",
+		`state.encodeInt(int64(x))`,
+	},
+	{
+		"int32",
+		"Int32",
+		"0",
+		`state.encodeInt(int64(x))`,
+	},
+	{
+		"int64",
+		"Int64",
+		"0",
+		`state.encodeInt(x)`,
+	},
+	{
+		"int8",
+		"Int8",
+		"0",
+		`state.encodeInt(int64(x))`,
+	},
+	{
+		"string",
+		"String",
+		`""`,
+		`state.encodeUint(uint64(len(x)))
+		state.b.WriteString(x)`,
+	},
+	{
+		"uint",
+		"Uint",
+		"0",
+		`state.encodeUint(uint64(x))`,
+	},
+	{
+		"uint16",
+		"Uint16",
+		"0",
+		`state.encodeUint(uint64(x))`,
+	},
+	{
+		"uint32",
+		"Uint32",
+		"0",
+		`state.encodeUint(uint64(x))`,
+	},
+	{
+		"uint64",
+		"Uint64",
+		"0",
+		`state.encodeUint(x)`,
+	},
+	{
+		"uintptr",
+		"Uintptr",
+		"0",
+		`state.encodeUint(uint64(x))`,
+	},
+	// uint8 Handled separately.
+}
+
+func main() {
+	log.SetFlags(0)
+	log.SetPrefix("encgen: ")
+	flag.Parse()
+	if flag.NArg() != 0 {
+		log.Fatal("usage: encgen [--output filename]")
+	}
+	var b bytes.Buffer
+	fmt.Fprintf(&b, "// Code generated by go run encgen.go -output %s; DO NOT EDIT.\n", *output)
+	fmt.Fprint(&b, header)
+	printMaps(&b, "Array")
+	fmt.Fprint(&b, "\n")
+	printMaps(&b, "Slice")
+	for _, t := range types {
+		fmt.Fprintf(&b, arrayHelper, t.lower, t.upper)
+		fmt.Fprintf(&b, sliceHelper, t.lower, t.upper, t.zero, t.encoder)
+	}
+	source, err := format.Source(b.Bytes())
+	if err != nil {
+		log.Fatal("source format error:", err)
+	}
+	fd, err := os.Create(*output)
+	if err != nil {
+		log.Fatal(err)
+	}
+	if _, err := fd.Write(source); err != nil {
+		log.Fatal(err)
+	}
+}
+
+func printMaps(b *bytes.Buffer, upperClass string) {
+	fmt.Fprintf(b, "var enc%sHelper = map[reflect.Kind]encHelper{\n", upperClass)
+	for _, t := range types {
+		fmt.Fprintf(b, "reflect.%s: enc%s%s,\n", t.upper, t.upper, upperClass)
+	}
+	fmt.Fprintf(b, "}\n")
+}
+
+const header = `
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package gob
+
+import (
+	"reflect"
+)
+
+`
+
+const arrayHelper = `
+func enc%[2]sArray(state *encoderState, v reflect.Value) bool {
+	// Can only slice if it is addressable.
+	if !v.CanAddr() {
+		return false
+	}
+	return enc%[2]sSlice(state, v.Slice(0, v.Len()))
+}
+`
+
+const sliceHelper = `
+func enc%[2]sSlice(state *encoderState, v reflect.Value) bool {
+	slice, ok := v.Interface().([]%[1]s)
+	if !ok {
+		// It is kind %[1]s but not type %[1]s. TODO: We can handle this unsafely.
+		return false
+	}
+	for _, x := range slice {
+		if x != %[3]s || state.sendZero {
+			%[4]s
+		}
+	}
+	return true
+}
+`
diff --git a/src/encoding/gob/encode.go b/src/encoding/gob/encode.go
new file mode 100644
index 0000000..548d614
--- /dev/null
+++ b/src/encoding/gob/encode.go
@@ -0,0 +1,705 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:generate go run encgen.go -output enc_helpers.go
+
+package gob
+
+import (
+	"encoding"
+	"encoding/binary"
+	"math"
+	"math/bits"
+	"reflect"
+	"sync"
+)
+
+const uint64Size = 8
+
+type encHelper func(state *encoderState, v reflect.Value) bool
+
+// encoderState is the global execution state of an instance of the encoder.
+// Field numbers are delta encoded and always increase. The field
+// number is initialized to -1 so 0 comes out as delta(1). A delta of
+// 0 terminates the structure.
+type encoderState struct {
+	enc      *Encoder
+	b        *encBuffer
+	sendZero bool                 // encoding an array element or map key/value pair; send zero values
+	fieldnum int                  // the last field number written.
+	buf      [1 + uint64Size]byte // buffer used by the encoder; here to avoid allocation.
+	next     *encoderState        // for free list
+}
+
+// encBuffer is an extremely simple, fast implementation of a write-only byte buffer.
+// It never returns a non-nil error, but Write returns an error value so it matches io.Writer.
+type encBuffer struct {
+	data    []byte
+	scratch [64]byte
+}
+
+var encBufferPool = sync.Pool{
+	New: func() any {
+		e := new(encBuffer)
+		e.data = e.scratch[0:0]
+		return e
+	},
+}
+
+func (e *encBuffer) writeByte(c byte) {
+	e.data = append(e.data, c)
+}
+
+func (e *encBuffer) Write(p []byte) (int, error) {
+	e.data = append(e.data, p...)
+	return len(p), nil
+}
+
+func (e *encBuffer) WriteString(s string) {
+	e.data = append(e.data, s...)
+}
+
+func (e *encBuffer) Len() int {
+	return len(e.data)
+}
+
+func (e *encBuffer) Bytes() []byte {
+	return e.data
+}
+
+func (e *encBuffer) Reset() {
+	if len(e.data) >= tooBig {
+		e.data = e.scratch[0:0]
+	} else {
+		e.data = e.data[0:0]
+	}
+}
+
+func (enc *Encoder) newEncoderState(b *encBuffer) *encoderState {
+	e := enc.freeList
+	if e == nil {
+		e = new(encoderState)
+		e.enc = enc
+	} else {
+		enc.freeList = e.next
+	}
+	e.sendZero = false
+	e.fieldnum = 0
+	e.b = b
+	if len(b.data) == 0 {
+		b.data = b.scratch[0:0]
+	}
+	return e
+}
+
+func (enc *Encoder) freeEncoderState(e *encoderState) {
+	e.next = enc.freeList
+	enc.freeList = e
+}
+
+// Unsigned integers have a two-state encoding. If the number is less
+// than 128 (0 through 0x7F), its value is written directly.
+// Otherwise the value is written in big-endian byte order preceded
+// by the byte length, negated.
+
+// encodeUint writes an encoded unsigned integer to state.b.
+func (state *encoderState) encodeUint(x uint64) {
+	if x <= 0x7F {
+		state.b.writeByte(uint8(x))
+		return
+	}
+
+	binary.BigEndian.PutUint64(state.buf[1:], x)
+	bc := bits.LeadingZeros64(x) >> 3      // 8 - bytelen(x)
+	state.buf[bc] = uint8(bc - uint64Size) // and then we subtract 8 to get -bytelen(x)
+
+	state.b.Write(state.buf[bc : uint64Size+1])
+}
+
+// encodeInt writes an encoded signed integer to state.w.
+// The low bit of the encoding says whether to bit complement the (other bits of the)
+// uint to recover the int.
+func (state *encoderState) encodeInt(i int64) {
+	var x uint64
+	if i < 0 {
+		x = uint64(^i<<1) | 1
+	} else {
+		x = uint64(i << 1)
+	}
+	state.encodeUint(x)
+}
+
+// encOp is the signature of an encoding operator for a given type.
+type encOp func(i *encInstr, state *encoderState, v reflect.Value)
+
+// The 'instructions' of the encoding machine
+type encInstr struct {
+	op    encOp
+	field int   // field number in input
+	index []int // struct index
+	indir int   // how many pointer indirections to reach the value in the struct
+}
+
+// update emits a field number and updates the state to record its value for delta encoding.
+// If the instruction pointer is nil, it does nothing
+func (state *encoderState) update(instr *encInstr) {
+	if instr != nil {
+		state.encodeUint(uint64(instr.field - state.fieldnum))
+		state.fieldnum = instr.field
+	}
+}
+
+// Each encoder for a composite is responsible for handling any
+// indirections associated with the elements of the data structure.
+// If any pointer so reached is nil, no bytes are written. If the
+// data item is zero, no bytes are written. Single values - ints,
+// strings etc. - are indirected before calling their encoders.
+// Otherwise, the output (for a scalar) is the field number, as an
+// encoded integer, followed by the field data in its appropriate
+// format.
+
+// encIndirect dereferences pv indir times and returns the result.
+func encIndirect(pv reflect.Value, indir int) reflect.Value {
+	for ; indir > 0; indir-- {
+		if pv.IsNil() {
+			break
+		}
+		pv = pv.Elem()
+	}
+	return pv
+}
+
+// encBool encodes the bool referenced by v as an unsigned 0 or 1.
+func encBool(i *encInstr, state *encoderState, v reflect.Value) {
+	b := v.Bool()
+	if b || state.sendZero {
+		state.update(i)
+		if b {
+			state.encodeUint(1)
+		} else {
+			state.encodeUint(0)
+		}
+	}
+}
+
+// encInt encodes the signed integer (int int8 int16 int32 int64) referenced by v.
+func encInt(i *encInstr, state *encoderState, v reflect.Value) {
+	value := v.Int()
+	if value != 0 || state.sendZero {
+		state.update(i)
+		state.encodeInt(value)
+	}
+}
+
+// encUint encodes the unsigned integer (uint uint8 uint16 uint32 uint64 uintptr) referenced by v.
+func encUint(i *encInstr, state *encoderState, v reflect.Value) {
+	value := v.Uint()
+	if value != 0 || state.sendZero {
+		state.update(i)
+		state.encodeUint(value)
+	}
+}
+
+// floatBits returns a uint64 holding the bits of a floating-point number.
+// Floating-point numbers are transmitted as uint64s holding the bits
+// of the underlying representation. They are sent byte-reversed, with
+// the exponent end coming out first, so integer floating point numbers
+// (for example) transmit more compactly. This routine does the
+// swizzling.
+func floatBits(f float64) uint64 {
+	u := math.Float64bits(f)
+	return bits.ReverseBytes64(u)
+}
+
+// encFloat encodes the floating point value (float32 float64) referenced by v.
+func encFloat(i *encInstr, state *encoderState, v reflect.Value) {
+	f := v.Float()
+	if f != 0 || state.sendZero {
+		bits := floatBits(f)
+		state.update(i)
+		state.encodeUint(bits)
+	}
+}
+
+// encComplex encodes the complex value (complex64 complex128) referenced by v.
+// Complex numbers are just a pair of floating-point numbers, real part first.
+func encComplex(i *encInstr, state *encoderState, v reflect.Value) {
+	c := v.Complex()
+	if c != 0+0i || state.sendZero {
+		rpart := floatBits(real(c))
+		ipart := floatBits(imag(c))
+		state.update(i)
+		state.encodeUint(rpart)
+		state.encodeUint(ipart)
+	}
+}
+
+// encUint8Array encodes the byte array referenced by v.
+// Byte arrays are encoded as an unsigned count followed by the raw bytes.
+func encUint8Array(i *encInstr, state *encoderState, v reflect.Value) {
+	b := v.Bytes()
+	if len(b) > 0 || state.sendZero {
+		state.update(i)
+		state.encodeUint(uint64(len(b)))
+		state.b.Write(b)
+	}
+}
+
+// encString encodes the string referenced by v.
+// Strings are encoded as an unsigned count followed by the raw bytes.
+func encString(i *encInstr, state *encoderState, v reflect.Value) {
+	s := v.String()
+	if len(s) > 0 || state.sendZero {
+		state.update(i)
+		state.encodeUint(uint64(len(s)))
+		state.b.WriteString(s)
+	}
+}
+
+// encStructTerminator encodes the end of an encoded struct
+// as delta field number of 0.
+func encStructTerminator(i *encInstr, state *encoderState, v reflect.Value) {
+	state.encodeUint(0)
+}
+
+// Execution engine
+
+// encEngine an array of instructions indexed by field number of the encoding
+// data, typically a struct. It is executed top to bottom, walking the struct.
+type encEngine struct {
+	instr []encInstr
+}
+
+const singletonField = 0
+
+// valid reports whether the value is valid and a non-nil pointer.
+// (Slices, maps, and chans take care of themselves.)
+func valid(v reflect.Value) bool {
+	switch v.Kind() {
+	case reflect.Invalid:
+		return false
+	case reflect.Pointer:
+		return !v.IsNil()
+	}
+	return true
+}
+
+// encodeSingle encodes a single top-level non-struct value.
+func (enc *Encoder) encodeSingle(b *encBuffer, engine *encEngine, value reflect.Value) {
+	state := enc.newEncoderState(b)
+	defer enc.freeEncoderState(state)
+	state.fieldnum = singletonField
+	// There is no surrounding struct to frame the transmission, so we must
+	// generate data even if the item is zero. To do this, set sendZero.
+	state.sendZero = true
+	instr := &engine.instr[singletonField]
+	if instr.indir > 0 {
+		value = encIndirect(value, instr.indir)
+	}
+	if valid(value) {
+		instr.op(instr, state, value)
+	}
+}
+
+// encodeStruct encodes a single struct value.
+func (enc *Encoder) encodeStruct(b *encBuffer, engine *encEngine, value reflect.Value) {
+	if !valid(value) {
+		return
+	}
+	state := enc.newEncoderState(b)
+	defer enc.freeEncoderState(state)
+	state.fieldnum = -1
+	for i := 0; i < len(engine.instr); i++ {
+		instr := &engine.instr[i]
+		if i >= value.NumField() {
+			// encStructTerminator
+			instr.op(instr, state, reflect.Value{})
+			break
+		}
+		field := value.FieldByIndex(instr.index)
+		if instr.indir > 0 {
+			field = encIndirect(field, instr.indir)
+			// TODO: Is field guaranteed valid? If so we could avoid this check.
+			if !valid(field) {
+				continue
+			}
+		}
+		instr.op(instr, state, field)
+	}
+}
+
+// encodeArray encodes an array.
+func (enc *Encoder) encodeArray(b *encBuffer, value reflect.Value, op encOp, elemIndir int, length int, helper encHelper) {
+	state := enc.newEncoderState(b)
+	defer enc.freeEncoderState(state)
+	state.fieldnum = -1
+	state.sendZero = true
+	state.encodeUint(uint64(length))
+	if helper != nil && helper(state, value) {
+		return
+	}
+	for i := 0; i < length; i++ {
+		elem := value.Index(i)
+		if elemIndir > 0 {
+			elem = encIndirect(elem, elemIndir)
+			// TODO: Is elem guaranteed valid? If so we could avoid this check.
+			if !valid(elem) {
+				errorf("encodeArray: nil element")
+			}
+		}
+		op(nil, state, elem)
+	}
+}
+
+// encodeReflectValue is a helper for maps. It encodes the value v.
+func encodeReflectValue(state *encoderState, v reflect.Value, op encOp, indir int) {
+	for i := 0; i < indir && v.IsValid(); i++ {
+		v = reflect.Indirect(v)
+	}
+	if !v.IsValid() {
+		errorf("encodeReflectValue: nil element")
+	}
+	op(nil, state, v)
+}
+
+// encodeMap encodes a map as unsigned count followed by key:value pairs.
+func (enc *Encoder) encodeMap(b *encBuffer, mv reflect.Value, keyOp, elemOp encOp, keyIndir, elemIndir int) {
+	state := enc.newEncoderState(b)
+	state.fieldnum = -1
+	state.sendZero = true
+	state.encodeUint(uint64(mv.Len()))
+	mi := mv.MapRange()
+	for mi.Next() {
+		encodeReflectValue(state, mi.Key(), keyOp, keyIndir)
+		encodeReflectValue(state, mi.Value(), elemOp, elemIndir)
+	}
+	enc.freeEncoderState(state)
+}
+
+// encodeInterface encodes the interface value iv.
+// To send an interface, we send a string identifying the concrete type, followed
+// by the type identifier (which might require defining that type right now), followed
+// by the concrete value. A nil value gets sent as the empty string for the name,
+// followed by no value.
+func (enc *Encoder) encodeInterface(b *encBuffer, iv reflect.Value) {
+	// Gobs can encode nil interface values but not typed interface
+	// values holding nil pointers, since nil pointers point to no value.
+	elem := iv.Elem()
+	if elem.Kind() == reflect.Pointer && elem.IsNil() {
+		errorf("gob: cannot encode nil pointer of type %s inside interface", iv.Elem().Type())
+	}
+	state := enc.newEncoderState(b)
+	state.fieldnum = -1
+	state.sendZero = true
+	if iv.IsNil() {
+		state.encodeUint(0)
+		return
+	}
+
+	ut := userType(iv.Elem().Type())
+	namei, ok := concreteTypeToName.Load(ut.base)
+	if !ok {
+		errorf("type not registered for interface: %s", ut.base)
+	}
+	name := namei.(string)
+
+	// Send the name.
+	state.encodeUint(uint64(len(name)))
+	state.b.WriteString(name)
+	// Define the type id if necessary.
+	enc.sendTypeDescriptor(enc.writer(), state, ut)
+	// Send the type id.
+	enc.sendTypeId(state, ut)
+	// Encode the value into a new buffer. Any nested type definitions
+	// should be written to b, before the encoded value.
+	enc.pushWriter(b)
+	data := encBufferPool.Get().(*encBuffer)
+	data.Write(spaceForLength)
+	enc.encode(data, elem, ut)
+	if enc.err != nil {
+		error_(enc.err)
+	}
+	enc.popWriter()
+	enc.writeMessage(b, data)
+	data.Reset()
+	encBufferPool.Put(data)
+	if enc.err != nil {
+		error_(enc.err)
+	}
+	enc.freeEncoderState(state)
+}
+
+// isZero reports whether the value is the zero of its type.
+func isZero(val reflect.Value) bool {
+	switch val.Kind() {
+	case reflect.Array:
+		for i := 0; i < val.Len(); i++ {
+			if !isZero(val.Index(i)) {
+				return false
+			}
+		}
+		return true
+	case reflect.Map, reflect.Slice, reflect.String:
+		return val.Len() == 0
+	case reflect.Bool:
+		return !val.Bool()
+	case reflect.Complex64, reflect.Complex128:
+		return val.Complex() == 0
+	case reflect.Chan, reflect.Func, reflect.Interface, reflect.Pointer:
+		return val.IsNil()
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return val.Int() == 0
+	case reflect.Float32, reflect.Float64:
+		return val.Float() == 0
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		return val.Uint() == 0
+	case reflect.Struct:
+		for i := 0; i < val.NumField(); i++ {
+			if !isZero(val.Field(i)) {
+				return false
+			}
+		}
+		return true
+	}
+	panic("unknown type in isZero " + val.Type().String())
+}
+
+// encGobEncoder encodes a value that implements the GobEncoder interface.
+// The data is sent as a byte array.
+func (enc *Encoder) encodeGobEncoder(b *encBuffer, ut *userTypeInfo, v reflect.Value) {
+	// TODO: should we catch panics from the called method?
+
+	var data []byte
+	var err error
+	// We know it's one of these.
+	switch ut.externalEnc {
+	case xGob:
+		data, err = v.Interface().(GobEncoder).GobEncode()
+	case xBinary:
+		data, err = v.Interface().(encoding.BinaryMarshaler).MarshalBinary()
+	case xText:
+		data, err = v.Interface().(encoding.TextMarshaler).MarshalText()
+	}
+	if err != nil {
+		error_(err)
+	}
+	state := enc.newEncoderState(b)
+	state.fieldnum = -1
+	state.encodeUint(uint64(len(data)))
+	state.b.Write(data)
+	enc.freeEncoderState(state)
+}
+
+var encOpTable = [...]encOp{
+	reflect.Bool:       encBool,
+	reflect.Int:        encInt,
+	reflect.Int8:       encInt,
+	reflect.Int16:      encInt,
+	reflect.Int32:      encInt,
+	reflect.Int64:      encInt,
+	reflect.Uint:       encUint,
+	reflect.Uint8:      encUint,
+	reflect.Uint16:     encUint,
+	reflect.Uint32:     encUint,
+	reflect.Uint64:     encUint,
+	reflect.Uintptr:    encUint,
+	reflect.Float32:    encFloat,
+	reflect.Float64:    encFloat,
+	reflect.Complex64:  encComplex,
+	reflect.Complex128: encComplex,
+	reflect.String:     encString,
+}
+
+// encOpFor returns (a pointer to) the encoding op for the base type under rt and
+// the indirection count to reach it.
+func encOpFor(rt reflect.Type, inProgress map[reflect.Type]*encOp, building map[*typeInfo]bool) (*encOp, int) {
+	ut := userType(rt)
+	// If the type implements GobEncoder, we handle it without further processing.
+	if ut.externalEnc != 0 {
+		return gobEncodeOpFor(ut)
+	}
+	// If this type is already in progress, it's a recursive type (e.g. map[string]*T).
+	// Return the pointer to the op we're already building.
+	if opPtr := inProgress[rt]; opPtr != nil {
+		return opPtr, ut.indir
+	}
+	typ := ut.base
+	indir := ut.indir
+	k := typ.Kind()
+	var op encOp
+	if int(k) < len(encOpTable) {
+		op = encOpTable[k]
+	}
+	if op == nil {
+		inProgress[rt] = &op
+		// Special cases
+		switch t := typ; t.Kind() {
+		case reflect.Slice:
+			if t.Elem().Kind() == reflect.Uint8 {
+				op = encUint8Array
+				break
+			}
+			// Slices have a header; we decode it to find the underlying array.
+			elemOp, elemIndir := encOpFor(t.Elem(), inProgress, building)
+			helper := encSliceHelper[t.Elem().Kind()]
+			op = func(i *encInstr, state *encoderState, slice reflect.Value) {
+				if !state.sendZero && slice.Len() == 0 {
+					return
+				}
+				state.update(i)
+				state.enc.encodeArray(state.b, slice, *elemOp, elemIndir, slice.Len(), helper)
+			}
+		case reflect.Array:
+			// True arrays have size in the type.
+			elemOp, elemIndir := encOpFor(t.Elem(), inProgress, building)
+			helper := encArrayHelper[t.Elem().Kind()]
+			op = func(i *encInstr, state *encoderState, array reflect.Value) {
+				state.update(i)
+				state.enc.encodeArray(state.b, array, *elemOp, elemIndir, array.Len(), helper)
+			}
+		case reflect.Map:
+			keyOp, keyIndir := encOpFor(t.Key(), inProgress, building)
+			elemOp, elemIndir := encOpFor(t.Elem(), inProgress, building)
+			op = func(i *encInstr, state *encoderState, mv reflect.Value) {
+				// We send zero-length (but non-nil) maps because the
+				// receiver might want to use the map.  (Maps don't use append.)
+				if !state.sendZero && mv.IsNil() {
+					return
+				}
+				state.update(i)
+				state.enc.encodeMap(state.b, mv, *keyOp, *elemOp, keyIndir, elemIndir)
+			}
+		case reflect.Struct:
+			// Generate a closure that calls out to the engine for the nested type.
+			getEncEngine(userType(typ), building)
+			info := mustGetTypeInfo(typ)
+			op = func(i *encInstr, state *encoderState, sv reflect.Value) {
+				state.update(i)
+				// indirect through info to delay evaluation for recursive structs
+				enc := info.encoder.Load().(*encEngine)
+				state.enc.encodeStruct(state.b, enc, sv)
+			}
+		case reflect.Interface:
+			op = func(i *encInstr, state *encoderState, iv reflect.Value) {
+				if !state.sendZero && (!iv.IsValid() || iv.IsNil()) {
+					return
+				}
+				state.update(i)
+				state.enc.encodeInterface(state.b, iv)
+			}
+		}
+	}
+	if op == nil {
+		errorf("can't happen: encode type %s", rt)
+	}
+	return &op, indir
+}
+
+// gobEncodeOpFor returns the op for a type that is known to implement GobEncoder.
+func gobEncodeOpFor(ut *userTypeInfo) (*encOp, int) {
+	rt := ut.user
+	if ut.encIndir == -1 {
+		rt = reflect.PointerTo(rt)
+	} else if ut.encIndir > 0 {
+		for i := int8(0); i < ut.encIndir; i++ {
+			rt = rt.Elem()
+		}
+	}
+	var op encOp
+	op = func(i *encInstr, state *encoderState, v reflect.Value) {
+		if ut.encIndir == -1 {
+			// Need to climb up one level to turn value into pointer.
+			if !v.CanAddr() {
+				errorf("unaddressable value of type %s", rt)
+			}
+			v = v.Addr()
+		}
+		if !state.sendZero && isZero(v) {
+			return
+		}
+		state.update(i)
+		state.enc.encodeGobEncoder(state.b, ut, v)
+	}
+	return &op, int(ut.encIndir) // encIndir: op will get called with p == address of receiver.
+}
+
+// compileEnc returns the engine to compile the type.
+func compileEnc(ut *userTypeInfo, building map[*typeInfo]bool) *encEngine {
+	srt := ut.base
+	engine := new(encEngine)
+	seen := make(map[reflect.Type]*encOp)
+	rt := ut.base
+	if ut.externalEnc != 0 {
+		rt = ut.user
+	}
+	if ut.externalEnc == 0 && srt.Kind() == reflect.Struct {
+		for fieldNum, wireFieldNum := 0, 0; fieldNum < srt.NumField(); fieldNum++ {
+			f := srt.Field(fieldNum)
+			if !isSent(&f) {
+				continue
+			}
+			op, indir := encOpFor(f.Type, seen, building)
+			engine.instr = append(engine.instr, encInstr{*op, wireFieldNum, f.Index, indir})
+			wireFieldNum++
+		}
+		if srt.NumField() > 0 && len(engine.instr) == 0 {
+			errorf("type %s has no exported fields", rt)
+		}
+		engine.instr = append(engine.instr, encInstr{encStructTerminator, 0, nil, 0})
+	} else {
+		engine.instr = make([]encInstr, 1)
+		op, indir := encOpFor(rt, seen, building)
+		engine.instr[0] = encInstr{*op, singletonField, nil, indir}
+	}
+	return engine
+}
+
+// getEncEngine returns the engine to compile the type.
+func getEncEngine(ut *userTypeInfo, building map[*typeInfo]bool) *encEngine {
+	info, err := getTypeInfo(ut)
+	if err != nil {
+		error_(err)
+	}
+	enc, ok := info.encoder.Load().(*encEngine)
+	if !ok {
+		enc = buildEncEngine(info, ut, building)
+	}
+	return enc
+}
+
+func buildEncEngine(info *typeInfo, ut *userTypeInfo, building map[*typeInfo]bool) *encEngine {
+	// Check for recursive types.
+	if building != nil && building[info] {
+		return nil
+	}
+	info.encInit.Lock()
+	defer info.encInit.Unlock()
+	enc, ok := info.encoder.Load().(*encEngine)
+	if !ok {
+		if building == nil {
+			building = make(map[*typeInfo]bool)
+		}
+		building[info] = true
+		enc = compileEnc(ut, building)
+		info.encoder.Store(enc)
+	}
+	return enc
+}
+
+func (enc *Encoder) encode(b *encBuffer, value reflect.Value, ut *userTypeInfo) {
+	defer catchError(&enc.err)
+	engine := getEncEngine(ut, nil)
+	indir := ut.indir
+	if ut.externalEnc != 0 {
+		indir = int(ut.encIndir)
+	}
+	for i := 0; i < indir; i++ {
+		value = reflect.Indirect(value)
+	}
+	if ut.externalEnc == 0 && value.Type().Kind() == reflect.Struct {
+		enc.encodeStruct(b, engine, value)
+	} else {
+		enc.encodeSingle(b, engine, value)
+	}
+}
diff --git a/src/encoding/gob/encoder.go b/src/encoding/gob/encoder.go
new file mode 100644
index 0000000..5a80e6c
--- /dev/null
+++ b/src/encoding/gob/encoder.go
@@ -0,0 +1,258 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package gob
+
+import (
+	"errors"
+	"io"
+	"reflect"
+	"sync"
+)
+
+// An Encoder manages the transmission of type and data information to the
+// other side of a connection.  It is safe for concurrent use by multiple
+// goroutines.
+type Encoder struct {
+	mutex      sync.Mutex              // each item must be sent atomically
+	w          []io.Writer             // where to send the data
+	sent       map[reflect.Type]typeId // which types we've already sent
+	countState *encoderState           // stage for writing counts
+	freeList   *encoderState           // list of free encoderStates; avoids reallocation
+	byteBuf    encBuffer               // buffer for top-level encoderState
+	err        error
+}
+
+// Before we encode a message, we reserve space at the head of the
+// buffer in which to encode its length. This means we can use the
+// buffer to assemble the message without another allocation.
+const maxLength = 9 // Maximum size of an encoded length.
+var spaceForLength = make([]byte, maxLength)
+
+// NewEncoder returns a new encoder that will transmit on the io.Writer.
+func NewEncoder(w io.Writer) *Encoder {
+	enc := new(Encoder)
+	enc.w = []io.Writer{w}
+	enc.sent = make(map[reflect.Type]typeId)
+	enc.countState = enc.newEncoderState(new(encBuffer))
+	return enc
+}
+
+// writer() returns the innermost writer the encoder is using
+func (enc *Encoder) writer() io.Writer {
+	return enc.w[len(enc.w)-1]
+}
+
+// pushWriter adds a writer to the encoder.
+func (enc *Encoder) pushWriter(w io.Writer) {
+	enc.w = append(enc.w, w)
+}
+
+// popWriter pops the innermost writer.
+func (enc *Encoder) popWriter() {
+	enc.w = enc.w[0 : len(enc.w)-1]
+}
+
+func (enc *Encoder) setError(err error) {
+	if enc.err == nil { // remember the first.
+		enc.err = err
+	}
+}
+
+// writeMessage sends the data item preceded by a unsigned count of its length.
+func (enc *Encoder) writeMessage(w io.Writer, b *encBuffer) {
+	// Space has been reserved for the length at the head of the message.
+	// This is a little dirty: we grab the slice from the bytes.Buffer and massage
+	// it by hand.
+	message := b.Bytes()
+	messageLen := len(message) - maxLength
+	// Length cannot be bigger than the decoder can handle.
+	if messageLen >= tooBig {
+		enc.setError(errors.New("gob: encoder: message too big"))
+		return
+	}
+	// Encode the length.
+	enc.countState.b.Reset()
+	enc.countState.encodeUint(uint64(messageLen))
+	// Copy the length to be a prefix of the message.
+	offset := maxLength - enc.countState.b.Len()
+	copy(message[offset:], enc.countState.b.Bytes())
+	// Write the data.
+	_, err := w.Write(message[offset:])
+	// Drain the buffer and restore the space at the front for the count of the next message.
+	b.Reset()
+	b.Write(spaceForLength)
+	if err != nil {
+		enc.setError(err)
+	}
+}
+
+// sendActualType sends the requested type, without further investigation, unless
+// it's been sent before.
+func (enc *Encoder) sendActualType(w io.Writer, state *encoderState, ut *userTypeInfo, actual reflect.Type) (sent bool) {
+	if _, alreadySent := enc.sent[actual]; alreadySent {
+		return false
+	}
+	info, err := getTypeInfo(ut)
+	if err != nil {
+		enc.setError(err)
+		return
+	}
+	// Send the pair (-id, type)
+	// Id:
+	state.encodeInt(-int64(info.id))
+	// Type:
+	enc.encode(state.b, reflect.ValueOf(info.wire), wireTypeUserInfo)
+	enc.writeMessage(w, state.b)
+	if enc.err != nil {
+		return
+	}
+
+	// Remember we've sent this type, both what the user gave us and the base type.
+	enc.sent[ut.base] = info.id
+	if ut.user != ut.base {
+		enc.sent[ut.user] = info.id
+	}
+	// Now send the inner types
+	switch st := actual; st.Kind() {
+	case reflect.Struct:
+		for i := 0; i < st.NumField(); i++ {
+			if isExported(st.Field(i).Name) {
+				enc.sendType(w, state, st.Field(i).Type)
+			}
+		}
+	case reflect.Array, reflect.Slice:
+		enc.sendType(w, state, st.Elem())
+	case reflect.Map:
+		enc.sendType(w, state, st.Key())
+		enc.sendType(w, state, st.Elem())
+	}
+	return true
+}
+
+// sendType sends the type info to the other side, if necessary.
+func (enc *Encoder) sendType(w io.Writer, state *encoderState, origt reflect.Type) (sent bool) {
+	ut := userType(origt)
+	if ut.externalEnc != 0 {
+		// The rules are different: regardless of the underlying type's representation,
+		// we need to tell the other side that the base type is a GobEncoder.
+		return enc.sendActualType(w, state, ut, ut.base)
+	}
+
+	// It's a concrete value, so drill down to the base type.
+	switch rt := ut.base; rt.Kind() {
+	default:
+		// Basic types and interfaces do not need to be described.
+		return
+	case reflect.Slice:
+		// If it's []uint8, don't send; it's considered basic.
+		if rt.Elem().Kind() == reflect.Uint8 {
+			return
+		}
+		// Otherwise we do send.
+		break
+	case reflect.Array:
+		// arrays must be sent so we know their lengths and element types.
+		break
+	case reflect.Map:
+		// maps must be sent so we know their lengths and key/value types.
+		break
+	case reflect.Struct:
+		// structs must be sent so we know their fields.
+		break
+	case reflect.Chan, reflect.Func:
+		// If we get here, it's a field of a struct; ignore it.
+		return
+	}
+
+	return enc.sendActualType(w, state, ut, ut.base)
+}
+
+// Encode transmits the data item represented by the empty interface value,
+// guaranteeing that all necessary type information has been transmitted first.
+// Passing a nil pointer to Encoder will panic, as they cannot be transmitted by gob.
+func (enc *Encoder) Encode(e any) error {
+	return enc.EncodeValue(reflect.ValueOf(e))
+}
+
+// sendTypeDescriptor makes sure the remote side knows about this type.
+// It will send a descriptor if this is the first time the type has been
+// sent.
+func (enc *Encoder) sendTypeDescriptor(w io.Writer, state *encoderState, ut *userTypeInfo) {
+	// Make sure the type is known to the other side.
+	// First, have we already sent this type?
+	rt := ut.base
+	if ut.externalEnc != 0 {
+		rt = ut.user
+	}
+	if _, alreadySent := enc.sent[rt]; !alreadySent {
+		// No, so send it.
+		sent := enc.sendType(w, state, rt)
+		if enc.err != nil {
+			return
+		}
+		// If the type info has still not been transmitted, it means we have
+		// a singleton basic type (int, []byte etc.) at top level. We don't
+		// need to send the type info but we do need to update enc.sent.
+		if !sent {
+			info, err := getTypeInfo(ut)
+			if err != nil {
+				enc.setError(err)
+				return
+			}
+			enc.sent[rt] = info.id
+		}
+	}
+}
+
+// sendTypeId sends the id, which must have already been defined.
+func (enc *Encoder) sendTypeId(state *encoderState, ut *userTypeInfo) {
+	// Identify the type of this top-level value.
+	state.encodeInt(int64(enc.sent[ut.base]))
+}
+
+// EncodeValue transmits the data item represented by the reflection value,
+// guaranteeing that all necessary type information has been transmitted first.
+// Passing a nil pointer to EncodeValue will panic, as they cannot be transmitted by gob.
+func (enc *Encoder) EncodeValue(value reflect.Value) error {
+	if value.Kind() == reflect.Invalid {
+		return errors.New("gob: cannot encode nil value")
+	}
+	if value.Kind() == reflect.Pointer && value.IsNil() {
+		panic("gob: cannot encode nil pointer of type " + value.Type().String())
+	}
+
+	// Make sure we're single-threaded through here, so multiple
+	// goroutines can share an encoder.
+	enc.mutex.Lock()
+	defer enc.mutex.Unlock()
+
+	// Remove any nested writers remaining due to previous errors.
+	enc.w = enc.w[0:1]
+
+	ut, err := validUserType(value.Type())
+	if err != nil {
+		return err
+	}
+
+	enc.err = nil
+	enc.byteBuf.Reset()
+	enc.byteBuf.Write(spaceForLength)
+	state := enc.newEncoderState(&enc.byteBuf)
+
+	enc.sendTypeDescriptor(enc.writer(), state, ut)
+	enc.sendTypeId(state, ut)
+	if enc.err != nil {
+		return enc.err
+	}
+
+	// Encode the object.
+	enc.encode(state.b, value, ut)
+	if enc.err == nil {
+		enc.writeMessage(enc.writer(), state.b)
+	}
+
+	enc.freeEncoderState(state)
+	return enc.err
+}
diff --git a/src/encoding/gob/encoder_test.go b/src/encoding/gob/encoder_test.go
new file mode 100644
index 0000000..6934841
--- /dev/null
+++ b/src/encoding/gob/encoder_test.go
@@ -0,0 +1,1267 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package gob
+
+import (
+	"bytes"
+	"encoding/hex"
+	"fmt"
+	"io"
+	"math"
+	"reflect"
+	"sort"
+	"strings"
+	"testing"
+)
+
+// Test basic operations in a safe manner.
+func TestBasicEncoderDecoder(t *testing.T) {
+	var values = []any{
+		true,
+		int(123),
+		int8(123),
+		int16(-12345),
+		int32(123456),
+		int64(-1234567),
+		uint(123),
+		uint8(123),
+		uint16(12345),
+		uint32(123456),
+		uint64(1234567),
+		uintptr(12345678),
+		float32(1.2345),
+		float64(1.2345678),
+		complex64(1.2345 + 2.3456i),
+		complex128(1.2345678 + 2.3456789i),
+		[]byte("hello"),
+		string("hello"),
+	}
+	for _, value := range values {
+		b := new(bytes.Buffer)
+		enc := NewEncoder(b)
+		err := enc.Encode(value)
+		if err != nil {
+			t.Error("encoder fail:", err)
+		}
+		dec := NewDecoder(b)
+		result := reflect.New(reflect.TypeOf(value))
+		err = dec.Decode(result.Interface())
+		if err != nil {
+			t.Fatalf("error decoding %T: %v:", reflect.TypeOf(value), err)
+		}
+		if !reflect.DeepEqual(value, result.Elem().Interface()) {
+			t.Fatalf("%T: expected %v got %v", value, value, result.Elem().Interface())
+		}
+	}
+}
+
+func TestEncodeIntSlice(t *testing.T) {
+
+	s8 := []int8{1, 5, 12, 22, 35, 51, 70, 92, 117}
+	s16 := []int16{145, 176, 210, 247, 287, 330, 376, 425, 477}
+	s32 := []int32{532, 590, 651, 715, 782, 852, 925, 1001, 1080}
+	s64 := []int64{1162, 1247, 1335, 1426, 1520, 1617, 1717, 1820, 1926}
+
+	t.Run("int8", func(t *testing.T) {
+		var sink bytes.Buffer
+		enc := NewEncoder(&sink)
+		enc.Encode(s8)
+
+		dec := NewDecoder(&sink)
+		res := make([]int8, 9)
+		dec.Decode(&res)
+
+		if !reflect.DeepEqual(s8, res) {
+			t.Fatalf("EncodeIntSlice: expected %v, got %v", s8, res)
+		}
+	})
+
+	t.Run("int16", func(t *testing.T) {
+		var sink bytes.Buffer
+		enc := NewEncoder(&sink)
+		enc.Encode(s16)
+
+		dec := NewDecoder(&sink)
+		res := make([]int16, 9)
+		dec.Decode(&res)
+
+		if !reflect.DeepEqual(s16, res) {
+			t.Fatalf("EncodeIntSlice: expected %v, got %v", s16, res)
+		}
+	})
+
+	t.Run("int32", func(t *testing.T) {
+		var sink bytes.Buffer
+		enc := NewEncoder(&sink)
+		enc.Encode(s32)
+
+		dec := NewDecoder(&sink)
+		res := make([]int32, 9)
+		dec.Decode(&res)
+
+		if !reflect.DeepEqual(s32, res) {
+			t.Fatalf("EncodeIntSlice: expected %v, got %v", s32, res)
+		}
+	})
+
+	t.Run("int64", func(t *testing.T) {
+		var sink bytes.Buffer
+		enc := NewEncoder(&sink)
+		enc.Encode(s64)
+
+		dec := NewDecoder(&sink)
+		res := make([]int64, 9)
+		dec.Decode(&res)
+
+		if !reflect.DeepEqual(s64, res) {
+			t.Fatalf("EncodeIntSlice: expected %v, got %v", s64, res)
+		}
+	})
+
+}
+
+type ET0 struct {
+	A int
+	B string
+}
+
+type ET2 struct {
+	X string
+}
+
+type ET1 struct {
+	A    int
+	Et2  *ET2
+	Next *ET1
+}
+
+// Like ET1 but with a different name for a field
+type ET3 struct {
+	A             int
+	Et2           *ET2
+	DifferentNext *ET1
+}
+
+// Like ET1 but with a different type for a field
+type ET4 struct {
+	A    int
+	Et2  float64
+	Next int
+}
+
+func TestEncoderDecoder(t *testing.T) {
+	b := new(bytes.Buffer)
+	enc := NewEncoder(b)
+	et0 := new(ET0)
+	et0.A = 7
+	et0.B = "gobs of fun"
+	err := enc.Encode(et0)
+	if err != nil {
+		t.Error("encoder fail:", err)
+	}
+	//fmt.Printf("% x %q\n", b, b)
+	//Debug(b)
+	dec := NewDecoder(b)
+	newEt0 := new(ET0)
+	err = dec.Decode(newEt0)
+	if err != nil {
+		t.Fatal("error decoding ET0:", err)
+	}
+
+	if !reflect.DeepEqual(et0, newEt0) {
+		t.Fatalf("invalid data for et0: expected %+v; got %+v", *et0, *newEt0)
+	}
+	if b.Len() != 0 {
+		t.Error("not at eof;", b.Len(), "bytes left")
+	}
+	//	t.FailNow()
+
+	b = new(bytes.Buffer)
+	enc = NewEncoder(b)
+	et1 := new(ET1)
+	et1.A = 7
+	et1.Et2 = new(ET2)
+	err = enc.Encode(et1)
+	if err != nil {
+		t.Error("encoder fail:", err)
+	}
+	dec = NewDecoder(b)
+	newEt1 := new(ET1)
+	err = dec.Decode(newEt1)
+	if err != nil {
+		t.Fatal("error decoding ET1:", err)
+	}
+
+	if !reflect.DeepEqual(et1, newEt1) {
+		t.Fatalf("invalid data for et1: expected %+v; got %+v", *et1, *newEt1)
+	}
+	if b.Len() != 0 {
+		t.Error("not at eof;", b.Len(), "bytes left")
+	}
+
+	enc.Encode(et1)
+	newEt1 = new(ET1)
+	err = dec.Decode(newEt1)
+	if err != nil {
+		t.Fatal("round 2: error decoding ET1:", err)
+	}
+	if !reflect.DeepEqual(et1, newEt1) {
+		t.Fatalf("round 2: invalid data for et1: expected %+v; got %+v", *et1, *newEt1)
+	}
+	if b.Len() != 0 {
+		t.Error("round 2: not at eof;", b.Len(), "bytes left")
+	}
+
+	// Now test with a running encoder/decoder pair that we recognize a type mismatch.
+	err = enc.Encode(et1)
+	if err != nil {
+		t.Error("round 3: encoder fail:", err)
+	}
+	newEt2 := new(ET2)
+	err = dec.Decode(newEt2)
+	if err == nil {
+		t.Fatal("round 3: expected `bad type' error decoding ET2")
+	}
+}
+
+// Run one value through the encoder/decoder, but use the wrong type.
+// Input is always an ET1; we compare it to whatever is under 'e'.
+func badTypeCheck(e any, shouldFail bool, msg string, t *testing.T) {
+	b := new(bytes.Buffer)
+	enc := NewEncoder(b)
+	et1 := new(ET1)
+	et1.A = 7
+	et1.Et2 = new(ET2)
+	err := enc.Encode(et1)
+	if err != nil {
+		t.Error("encoder fail:", err)
+	}
+	dec := NewDecoder(b)
+	err = dec.Decode(e)
+	if shouldFail && err == nil {
+		t.Error("expected error for", msg)
+	}
+	if !shouldFail && err != nil {
+		t.Error("unexpected error for", msg, err)
+	}
+}
+
+// Test that we recognize a bad type the first time.
+func TestWrongTypeDecoder(t *testing.T) {
+	badTypeCheck(new(ET2), true, "no fields in common", t)
+	badTypeCheck(new(ET3), false, "different name of field", t)
+	badTypeCheck(new(ET4), true, "different type of field", t)
+}
+
+// Types not supported at top level by the Encoder.
+var unsupportedValues = []any{
+	make(chan int),
+	func(a int) bool { return true },
+}
+
+func TestUnsupported(t *testing.T) {
+	var b bytes.Buffer
+	enc := NewEncoder(&b)
+	for _, v := range unsupportedValues {
+		err := enc.Encode(v)
+		if err == nil {
+			t.Errorf("expected error for %T; got none", v)
+		}
+	}
+}
+
+func encAndDec(in, out any) error {
+	b := new(bytes.Buffer)
+	enc := NewEncoder(b)
+	err := enc.Encode(in)
+	if err != nil {
+		return err
+	}
+	dec := NewDecoder(b)
+	err = dec.Decode(out)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+func TestTypeToPtrType(t *testing.T) {
+	// Encode a T, decode a *T
+	type Type0 struct {
+		A int
+	}
+	t0 := Type0{7}
+	t0p := new(Type0)
+	if err := encAndDec(t0, t0p); err != nil {
+		t.Error(err)
+	}
+}
+
+func TestPtrTypeToType(t *testing.T) {
+	// Encode a *T, decode a T
+	type Type1 struct {
+		A uint
+	}
+	t1p := &Type1{17}
+	var t1 Type1
+	if err := encAndDec(t1, t1p); err != nil {
+		t.Error(err)
+	}
+}
+
+func TestTypeToPtrPtrPtrPtrType(t *testing.T) {
+	type Type2 struct {
+		A ****float64
+	}
+	t2 := Type2{}
+	t2.A = new(***float64)
+	*t2.A = new(**float64)
+	**t2.A = new(*float64)
+	***t2.A = new(float64)
+	****t2.A = 27.4
+	t2pppp := new(***Type2)
+	if err := encAndDec(t2, t2pppp); err != nil {
+		t.Fatal(err)
+	}
+	if ****(****t2pppp).A != ****t2.A {
+		t.Errorf("wrong value after decode: %g not %g", ****(****t2pppp).A, ****t2.A)
+	}
+}
+
+func TestSlice(t *testing.T) {
+	type Type3 struct {
+		A []string
+	}
+	t3p := &Type3{[]string{"hello", "world"}}
+	var t3 Type3
+	if err := encAndDec(t3, t3p); err != nil {
+		t.Error(err)
+	}
+}
+
+func TestValueError(t *testing.T) {
+	// Encode a *T, decode a T
+	type Type4 struct {
+		A int
+	}
+	t4p := &Type4{3}
+	var t4 Type4 // note: not a pointer.
+	if err := encAndDec(t4p, t4); err == nil || !strings.Contains(err.Error(), "pointer") {
+		t.Error("expected error about pointer; got", err)
+	}
+}
+
+func TestArray(t *testing.T) {
+	type Type5 struct {
+		A [3]string
+		B [3]byte
+	}
+	type Type6 struct {
+		A [2]string // can't hold t5.a
+	}
+	t5 := Type5{[3]string{"hello", ",", "world"}, [3]byte{1, 2, 3}}
+	var t5p Type5
+	if err := encAndDec(t5, &t5p); err != nil {
+		t.Error(err)
+	}
+	var t6 Type6
+	if err := encAndDec(t5, &t6); err == nil {
+		t.Error("should fail with mismatched array sizes")
+	}
+}
+
+func TestRecursiveMapType(t *testing.T) {
+	type recursiveMap map[string]recursiveMap
+	r1 := recursiveMap{"A": recursiveMap{"B": nil, "C": nil}, "D": nil}
+	r2 := make(recursiveMap)
+	if err := encAndDec(r1, &r2); err != nil {
+		t.Error(err)
+	}
+}
+
+func TestRecursiveSliceType(t *testing.T) {
+	type recursiveSlice []recursiveSlice
+	r1 := recursiveSlice{0: recursiveSlice{0: nil}, 1: nil}
+	r2 := make(recursiveSlice, 0)
+	if err := encAndDec(r1, &r2); err != nil {
+		t.Error(err)
+	}
+}
+
+// Regression test for bug: must send zero values inside arrays
+func TestDefaultsInArray(t *testing.T) {
+	type Type7 struct {
+		B []bool
+		I []int
+		S []string
+		F []float64
+	}
+	t7 := Type7{
+		[]bool{false, false, true},
+		[]int{0, 0, 1},
+		[]string{"hi", "", "there"},
+		[]float64{0, 0, 1},
+	}
+	var t7p Type7
+	if err := encAndDec(t7, &t7p); err != nil {
+		t.Error(err)
+	}
+}
+
+var testInt int
+var testFloat32 float32
+var testString string
+var testSlice []string
+var testMap map[string]int
+var testArray [7]int
+
+type SingleTest struct {
+	in  any
+	out any
+	err string
+}
+
+var singleTests = []SingleTest{
+	{17, &testInt, ""},
+	{float32(17.5), &testFloat32, ""},
+	{"bike shed", &testString, ""},
+	{[]string{"bike", "shed", "paint", "color"}, &testSlice, ""},
+	{map[string]int{"seven": 7, "twelve": 12}, &testMap, ""},
+	{[7]int{4, 55, 0, 0, 0, 0, 0}, &testArray, ""}, // case that once triggered a bug
+	{[7]int{4, 55, 1, 44, 22, 66, 1234}, &testArray, ""},
+
+	// Decode errors
+	{172, &testFloat32, "type"},
+}
+
+func TestSingletons(t *testing.T) {
+	b := new(bytes.Buffer)
+	enc := NewEncoder(b)
+	dec := NewDecoder(b)
+	for _, test := range singleTests {
+		b.Reset()
+		err := enc.Encode(test.in)
+		if err != nil {
+			t.Errorf("error encoding %v: %s", test.in, err)
+			continue
+		}
+		err = dec.Decode(test.out)
+		switch {
+		case err != nil && test.err == "":
+			t.Errorf("error decoding %v: %s", test.in, err)
+			continue
+		case err == nil && test.err != "":
+			t.Errorf("expected error decoding %v: %s", test.in, test.err)
+			continue
+		case err != nil && test.err != "":
+			if !strings.Contains(err.Error(), test.err) {
+				t.Errorf("wrong error decoding %v: wanted %s, got %v", test.in, test.err, err)
+			}
+			continue
+		}
+		// Get rid of the pointer in the rhs
+		val := reflect.ValueOf(test.out).Elem().Interface()
+		if !reflect.DeepEqual(test.in, val) {
+			t.Errorf("decoding singleton: expected %v got %v", test.in, val)
+		}
+	}
+}
+
+func TestStructNonStruct(t *testing.T) {
+	type Struct struct {
+		A string
+	}
+	type NonStruct string
+	s := Struct{"hello"}
+	var sp Struct
+	if err := encAndDec(s, &sp); err != nil {
+		t.Error(err)
+	}
+	var ns NonStruct
+	if err := encAndDec(s, &ns); err == nil {
+		t.Error("should get error for struct/non-struct")
+	} else if !strings.Contains(err.Error(), "type") {
+		t.Error("for struct/non-struct expected type error; got", err)
+	}
+	// Now try the other way
+	var nsp NonStruct
+	if err := encAndDec(ns, &nsp); err != nil {
+		t.Error(err)
+	}
+	if err := encAndDec(ns, &s); err == nil {
+		t.Error("should get error for non-struct/struct")
+	} else if !strings.Contains(err.Error(), "type") {
+		t.Error("for non-struct/struct expected type error; got", err)
+	}
+}
+
+type interfaceIndirectTestI interface {
+	F() bool
+}
+
+type interfaceIndirectTestT struct{}
+
+func (this *interfaceIndirectTestT) F() bool {
+	return true
+}
+
+// A version of a bug reported on golang-nuts. Also tests top-level
+// slice of interfaces. The issue was registering *T caused T to be
+// stored as the concrete type.
+func TestInterfaceIndirect(t *testing.T) {
+	Register(&interfaceIndirectTestT{})
+	b := new(bytes.Buffer)
+	w := []interfaceIndirectTestI{&interfaceIndirectTestT{}}
+	err := NewEncoder(b).Encode(w)
+	if err != nil {
+		t.Fatal("encode error:", err)
+	}
+
+	var r []interfaceIndirectTestI
+	err = NewDecoder(b).Decode(&r)
+	if err != nil {
+		t.Fatal("decode error:", err)
+	}
+}
+
+// Now follow various tests that decode into things that can't represent the
+// encoded value, all of which should be legal.
+
+// Also, when the ignored object contains an interface value, it may define
+// types. Make sure that skipping the value still defines the types by using
+// the encoder/decoder pair to send a value afterwards. If an interface
+// is sent, its type in the test is always NewType0, so this checks that the
+// encoder and decoder don't skew with respect to type definitions.
+
+type Struct0 struct {
+	I any
+}
+
+type NewType0 struct {
+	S string
+}
+
+type ignoreTest struct {
+	in, out any
+}
+
+var ignoreTests = []ignoreTest{
+	// Decode normal struct into an empty struct
+	{&struct{ A int }{23}, &struct{}{}},
+	// Decode normal struct into a nil.
+	{&struct{ A int }{23}, nil},
+	// Decode singleton string into a nil.
+	{"hello, world", nil},
+	// Decode singleton slice into a nil.
+	{[]int{1, 2, 3, 4}, nil},
+	// Decode struct containing an interface into a nil.
+	{&Struct0{&NewType0{"value0"}}, nil},
+	// Decode singleton slice of interfaces into a nil.
+	{[]any{"hi", &NewType0{"value1"}, 23}, nil},
+}
+
+func TestDecodeIntoNothing(t *testing.T) {
+	Register(new(NewType0))
+	for i, test := range ignoreTests {
+		b := new(bytes.Buffer)
+		enc := NewEncoder(b)
+		err := enc.Encode(test.in)
+		if err != nil {
+			t.Errorf("%d: encode error %s:", i, err)
+			continue
+		}
+		dec := NewDecoder(b)
+		err = dec.Decode(test.out)
+		if err != nil {
+			t.Errorf("%d: decode error: %s", i, err)
+			continue
+		}
+		// Now see if the encoder and decoder are in a consistent state.
+		str := fmt.Sprintf("Value %d", i)
+		err = enc.Encode(&NewType0{str})
+		if err != nil {
+			t.Fatalf("%d: NewType0 encode error: %s", i, err)
+		}
+		ns := new(NewType0)
+		err = dec.Decode(ns)
+		if err != nil {
+			t.Fatalf("%d: NewType0 decode error: %s", i, err)
+		}
+		if ns.S != str {
+			t.Fatalf("%d: expected %q got %q", i, str, ns.S)
+		}
+	}
+}
+
+func TestIgnoreRecursiveType(t *testing.T) {
+	// It's hard to build a self-contained test for this because
+	// we can't build compatible types in one package with
+	// different items so something is ignored. Here is
+	// some data that represents, according to debug.go:
+	// type definition {
+	//	slice "recursiveSlice" id=106
+	//		elem id=106
+	// }
+	data := []byte{
+		0x1d, 0xff, 0xd3, 0x02, 0x01, 0x01, 0x0e, 0x72,
+		0x65, 0x63, 0x75, 0x72, 0x73, 0x69, 0x76, 0x65,
+		0x53, 0x6c, 0x69, 0x63, 0x65, 0x01, 0xff, 0xd4,
+		0x00, 0x01, 0xff, 0xd4, 0x00, 0x00, 0x07, 0xff,
+		0xd4, 0x00, 0x02, 0x01, 0x00, 0x00,
+	}
+	dec := NewDecoder(bytes.NewReader(data))
+	// Issue 10415: This caused infinite recursion.
+	err := dec.Decode(nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+// Another bug from golang-nuts, involving nested interfaces.
+type Bug0Outer struct {
+	Bug0Field any
+}
+
+type Bug0Inner struct {
+	A int
+}
+
+func TestNestedInterfaces(t *testing.T) {
+	var buf bytes.Buffer
+	e := NewEncoder(&buf)
+	d := NewDecoder(&buf)
+	Register(new(Bug0Outer))
+	Register(new(Bug0Inner))
+	f := &Bug0Outer{&Bug0Outer{&Bug0Inner{7}}}
+	var v any = f
+	err := e.Encode(&v)
+	if err != nil {
+		t.Fatal("Encode:", err)
+	}
+	err = d.Decode(&v)
+	if err != nil {
+		t.Fatal("Decode:", err)
+	}
+	// Make sure it decoded correctly.
+	outer1, ok := v.(*Bug0Outer)
+	if !ok {
+		t.Fatalf("v not Bug0Outer: %T", v)
+	}
+	outer2, ok := outer1.Bug0Field.(*Bug0Outer)
+	if !ok {
+		t.Fatalf("v.Bug0Field not Bug0Outer: %T", outer1.Bug0Field)
+	}
+	inner, ok := outer2.Bug0Field.(*Bug0Inner)
+	if !ok {
+		t.Fatalf("v.Bug0Field.Bug0Field not Bug0Inner: %T", outer2.Bug0Field)
+	}
+	if inner.A != 7 {
+		t.Fatalf("final value %d; expected %d", inner.A, 7)
+	}
+}
+
+// The bugs keep coming. We forgot to send map subtypes before the map.
+
+type Bug1Elem struct {
+	Name string
+	Id   int
+}
+
+type Bug1StructMap map[string]Bug1Elem
+
+func TestMapBug1(t *testing.T) {
+	in := make(Bug1StructMap)
+	in["val1"] = Bug1Elem{"elem1", 1}
+	in["val2"] = Bug1Elem{"elem2", 2}
+
+	b := new(bytes.Buffer)
+	enc := NewEncoder(b)
+	err := enc.Encode(in)
+	if err != nil {
+		t.Fatal("encode:", err)
+	}
+	dec := NewDecoder(b)
+	out := make(Bug1StructMap)
+	err = dec.Decode(&out)
+	if err != nil {
+		t.Fatal("decode:", err)
+	}
+	if !reflect.DeepEqual(in, out) {
+		t.Errorf("mismatch: %v %v", in, out)
+	}
+}
+
+func TestGobMapInterfaceEncode(t *testing.T) {
+	m := map[string]any{
+		"up": uintptr(0),
+		"i0": []int{-1},
+		"i1": []int8{-1},
+		"i2": []int16{-1},
+		"i3": []int32{-1},
+		"i4": []int64{-1},
+		"u0": []uint{1},
+		"u1": []uint8{1},
+		"u2": []uint16{1},
+		"u3": []uint32{1},
+		"u4": []uint64{1},
+		"f0": []float32{1},
+		"f1": []float64{1},
+		"c0": []complex64{complex(2, -2)},
+		"c1": []complex128{complex(2, float64(-2))},
+		"us": []uintptr{0},
+		"bo": []bool{false},
+		"st": []string{"s"},
+	}
+	enc := NewEncoder(new(bytes.Buffer))
+	err := enc.Encode(m)
+	if err != nil {
+		t.Errorf("encode map: %s", err)
+	}
+}
+
+func TestSliceReusesMemory(t *testing.T) {
+	buf := new(bytes.Buffer)
+	// Bytes
+	{
+		x := []byte("abcd")
+		enc := NewEncoder(buf)
+		err := enc.Encode(x)
+		if err != nil {
+			t.Errorf("bytes: encode: %s", err)
+		}
+		// Decode into y, which is big enough.
+		y := []byte("ABCDE")
+		addr := &y[0]
+		dec := NewDecoder(buf)
+		err = dec.Decode(&y)
+		if err != nil {
+			t.Fatal("bytes: decode:", err)
+		}
+		if !bytes.Equal(x, y) {
+			t.Errorf("bytes: expected %q got %q\n", x, y)
+		}
+		if addr != &y[0] {
+			t.Errorf("bytes: unnecessary reallocation")
+		}
+	}
+	// general slice
+	{
+		x := []rune("abcd")
+		enc := NewEncoder(buf)
+		err := enc.Encode(x)
+		if err != nil {
+			t.Errorf("ints: encode: %s", err)
+		}
+		// Decode into y, which is big enough.
+		y := []rune("ABCDE")
+		addr := &y[0]
+		dec := NewDecoder(buf)
+		err = dec.Decode(&y)
+		if err != nil {
+			t.Fatal("ints: decode:", err)
+		}
+		if !reflect.DeepEqual(x, y) {
+			t.Errorf("ints: expected %q got %q\n", x, y)
+		}
+		if addr != &y[0] {
+			t.Errorf("ints: unnecessary reallocation")
+		}
+	}
+}
+
+// Used to crash: negative count in recvMessage.
+func TestBadCount(t *testing.T) {
+	b := []byte{0xfb, 0xa5, 0x82, 0x2f, 0xca, 0x1}
+	if err := NewDecoder(bytes.NewReader(b)).Decode(nil); err == nil {
+		t.Error("expected error from bad count")
+	} else if err.Error() != errBadCount.Error() {
+		t.Error("expected bad count error; got", err)
+	}
+}
+
+// Verify that sequential Decoders built on a single input will
+// succeed if the input implements ReadByte and there is no
+// type information in the stream.
+func TestSequentialDecoder(t *testing.T) {
+	b := new(bytes.Buffer)
+	enc := NewEncoder(b)
+	const count = 10
+	for i := 0; i < count; i++ {
+		s := fmt.Sprintf("%d", i)
+		if err := enc.Encode(s); err != nil {
+			t.Error("encoder fail:", err)
+		}
+	}
+	for i := 0; i < count; i++ {
+		dec := NewDecoder(b)
+		var s string
+		if err := dec.Decode(&s); err != nil {
+			t.Fatal("decoder fail:", err)
+		}
+		if s != fmt.Sprintf("%d", i) {
+			t.Fatalf("decode expected %d got %s", i, s)
+		}
+	}
+}
+
+// Should be able to have unrepresentable fields (chan, func, *chan etc.); we just ignore them.
+type Bug2 struct {
+	A   int
+	C   chan int
+	CP  *chan int
+	F   func()
+	FPP **func()
+}
+
+func TestChanFuncIgnored(t *testing.T) {
+	c := make(chan int)
+	f := func() {}
+	fp := &f
+	b0 := Bug2{23, c, &c, f, &fp}
+	var buf bytes.Buffer
+	enc := NewEncoder(&buf)
+	if err := enc.Encode(b0); err != nil {
+		t.Fatal("error encoding:", err)
+	}
+	var b1 Bug2
+	err := NewDecoder(&buf).Decode(&b1)
+	if err != nil {
+		t.Fatal("decode:", err)
+	}
+	if b1.A != b0.A {
+		t.Fatalf("got %d want %d", b1.A, b0.A)
+	}
+	if b1.C != nil || b1.CP != nil || b1.F != nil || b1.FPP != nil {
+		t.Fatal("unexpected value for chan or func")
+	}
+}
+
+func TestSliceIncompatibility(t *testing.T) {
+	var in = []byte{1, 2, 3}
+	var out []int
+	if err := encAndDec(in, &out); err == nil {
+		t.Error("expected compatibility error")
+	}
+}
+
+// Mutually recursive slices of structs caused problems.
+type Bug3 struct {
+	Num      int
+	Children []*Bug3
+}
+
+func TestGobPtrSlices(t *testing.T) {
+	in := []*Bug3{
+		{1, nil},
+		{2, nil},
+	}
+	b := new(bytes.Buffer)
+	err := NewEncoder(b).Encode(&in)
+	if err != nil {
+		t.Fatal("encode:", err)
+	}
+
+	var out []*Bug3
+	err = NewDecoder(b).Decode(&out)
+	if err != nil {
+		t.Fatal("decode:", err)
+	}
+	if !reflect.DeepEqual(in, out) {
+		t.Fatalf("got %v; wanted %v", out, in)
+	}
+}
+
+// getDecEnginePtr cached engine for ut.base instead of ut.user so we passed
+// a *map and then tried to reuse its engine to decode the inner map.
+func TestPtrToMapOfMap(t *testing.T) {
+	Register(make(map[string]any))
+	subdata := make(map[string]any)
+	subdata["bar"] = "baz"
+	data := make(map[string]any)
+	data["foo"] = subdata
+
+	b := new(bytes.Buffer)
+	err := NewEncoder(b).Encode(data)
+	if err != nil {
+		t.Fatal("encode:", err)
+	}
+	var newData map[string]any
+	err = NewDecoder(b).Decode(&newData)
+	if err != nil {
+		t.Fatal("decode:", err)
+	}
+	if !reflect.DeepEqual(data, newData) {
+		t.Fatalf("expected %v got %v", data, newData)
+	}
+}
+
+// Test that untyped nils generate an error, not a panic.
+// See Issue 16204.
+func TestCatchInvalidNilValue(t *testing.T) {
+	encodeErr, panicErr := encodeAndRecover(nil)
+	if panicErr != nil {
+		t.Fatalf("panicErr=%v, should not panic encoding untyped nil", panicErr)
+	}
+	if encodeErr == nil {
+		t.Errorf("got err=nil, want non-nil error when encoding untyped nil value")
+	} else if !strings.Contains(encodeErr.Error(), "nil value") {
+		t.Errorf("expected 'nil value' error; got err=%v", encodeErr)
+	}
+}
+
+// A top-level nil pointer generates a panic with a helpful string-valued message.
+func TestTopLevelNilPointer(t *testing.T) {
+	var ip *int
+	encodeErr, panicErr := encodeAndRecover(ip)
+	if encodeErr != nil {
+		t.Fatal("error in encode:", encodeErr)
+	}
+	if panicErr == nil {
+		t.Fatal("top-level nil pointer did not panic")
+	}
+	errMsg := panicErr.Error()
+	if !strings.Contains(errMsg, "nil pointer") {
+		t.Fatal("expected nil pointer error, got:", errMsg)
+	}
+}
+
+func encodeAndRecover(value any) (encodeErr, panicErr error) {
+	defer func() {
+		e := recover()
+		if e != nil {
+			switch err := e.(type) {
+			case error:
+				panicErr = err
+			default:
+				panicErr = fmt.Errorf("%v", err)
+			}
+		}
+	}()
+
+	encodeErr = NewEncoder(io.Discard).Encode(value)
+	return
+}
+
+func TestNilPointerPanics(t *testing.T) {
+	var (
+		nilStringPtr      *string
+		intMap            = make(map[int]int)
+		intMapPtr         = &intMap
+		nilIntMapPtr      *map[int]int
+		zero              int
+		nilBoolChannel    chan bool
+		nilBoolChannelPtr *chan bool
+		nilStringSlice    []string
+		stringSlice       = make([]string, 1)
+		nilStringSlicePtr *[]string
+	)
+
+	testCases := []struct {
+		value     any
+		mustPanic bool
+	}{
+		{nilStringPtr, true},
+		{intMap, false},
+		{intMapPtr, false},
+		{nilIntMapPtr, true},
+		{zero, false},
+		{nilStringSlice, false},
+		{stringSlice, false},
+		{nilStringSlicePtr, true},
+		{nilBoolChannel, false},
+		{nilBoolChannelPtr, true},
+	}
+
+	for _, tt := range testCases {
+		_, panicErr := encodeAndRecover(tt.value)
+		if tt.mustPanic {
+			if panicErr == nil {
+				t.Errorf("expected panic with input %#v, did not panic", tt.value)
+			}
+			continue
+		}
+		if panicErr != nil {
+			t.Fatalf("expected no panic with input %#v, got panic=%v", tt.value, panicErr)
+		}
+	}
+}
+
+func TestNilPointerInsideInterface(t *testing.T) {
+	var ip *int
+	si := struct {
+		I any
+	}{
+		I: ip,
+	}
+	buf := new(bytes.Buffer)
+	err := NewEncoder(buf).Encode(si)
+	if err == nil {
+		t.Fatal("expected error, got none")
+	}
+	errMsg := err.Error()
+	if !strings.Contains(errMsg, "nil pointer") || !strings.Contains(errMsg, "interface") {
+		t.Fatal("expected error about nil pointer and interface, got:", errMsg)
+	}
+}
+
+type Bug4Public struct {
+	Name   string
+	Secret Bug4Secret
+}
+
+type Bug4Secret struct {
+	a int // error: no exported fields.
+}
+
+// Test that a failed compilation doesn't leave around an executable encoder.
+// Issue 3723.
+func TestMutipleEncodingsOfBadType(t *testing.T) {
+	x := Bug4Public{
+		Name:   "name",
+		Secret: Bug4Secret{1},
+	}
+	buf := new(bytes.Buffer)
+	enc := NewEncoder(buf)
+	err := enc.Encode(x)
+	if err == nil {
+		t.Fatal("first encoding: expected error")
+	}
+	buf.Reset()
+	enc = NewEncoder(buf)
+	err = enc.Encode(x)
+	if err == nil {
+		t.Fatal("second encoding: expected error")
+	}
+	if !strings.Contains(err.Error(), "no exported fields") {
+		t.Errorf("expected error about no exported fields; got %v", err)
+	}
+}
+
+// There was an error check comparing the length of the input with the
+// length of the slice being decoded. It was wrong because the next
+// thing in the input might be a type definition, which would lead to
+// an incorrect length check. This test reproduces the corner case.
+
+type Z struct {
+}
+
+func Test29ElementSlice(t *testing.T) {
+	Register(Z{})
+	src := make([]any, 100) // Size needs to be bigger than size of type definition.
+	for i := range src {
+		src[i] = Z{}
+	}
+	buf := new(bytes.Buffer)
+	err := NewEncoder(buf).Encode(src)
+	if err != nil {
+		t.Fatalf("encode: %v", err)
+		return
+	}
+
+	var dst []any
+	err = NewDecoder(buf).Decode(&dst)
+	if err != nil {
+		t.Errorf("decode: %v", err)
+		return
+	}
+}
+
+// Don't crash, just give error when allocating a huge slice.
+// Issue 8084.
+func TestErrorForHugeSlice(t *testing.T) {
+	// Encode an int slice.
+	buf := new(bytes.Buffer)
+	slice := []int{1, 1, 1, 1, 1, 1, 1, 1, 1, 1}
+	err := NewEncoder(buf).Encode(slice)
+	if err != nil {
+		t.Fatal("encode:", err)
+	}
+	// Reach into the buffer and smash the count to make the encoded slice very long.
+	buf.Bytes()[buf.Len()-len(slice)-1] = 0xfa
+	// Decode and see error.
+	err = NewDecoder(buf).Decode(&slice)
+	if err == nil {
+		t.Fatal("decode: no error")
+	}
+	if !strings.Contains(err.Error(), "slice too big") {
+		t.Fatalf("decode: expected slice too big error, got %s", err.Error())
+	}
+}
+
+type badDataTest struct {
+	input string // The input encoded as a hex string.
+	error string // A substring of the error that should result.
+	data  any    // What to decode into.
+}
+
+var badDataTests = []badDataTest{
+	{"", "EOF", nil},
+	{"7F6869", "unexpected EOF", nil},
+	{"036e6f77206973207468652074696d6520666f7220616c6c20676f6f64206d656e", "unknown type id", new(ET2)},
+	{"0424666f6f", "field numbers out of bounds", new(ET2)}, // Issue 6323.
+	{"05100028557b02027f8302", "interface encoding", nil},   // Issue 10270.
+	// Issue 10273.
+	{"130a00fb5dad0bf8ff020263e70002fa28020202a89859", "slice length too large", nil},
+	{"0f1000fb285d003316020735ff023a65c5", "interface encoding", nil},
+	{"03fffb0616fffc00f902ff02ff03bf005d02885802a311a8120228022c028ee7", "GobDecoder", nil},
+	// Issue 10491.
+	{"10fe010f020102fe01100001fe010e000016fe010d030102fe010e00010101015801fe01100000000bfe011000f85555555555555555", "exceeds input size", nil},
+}
+
+// TestBadData tests that various problems caused by malformed input
+// are caught as errors and do not cause panics.
+func TestBadData(t *testing.T) {
+	for i, test := range badDataTests {
+		data, err := hex.DecodeString(test.input)
+		if err != nil {
+			t.Fatalf("#%d: hex error: %s", i, err)
+		}
+		d := NewDecoder(bytes.NewReader(data))
+		err = d.Decode(test.data)
+		if err == nil {
+			t.Errorf("decode: no error")
+			continue
+		}
+		if !strings.Contains(err.Error(), test.error) {
+			t.Errorf("#%d: decode: expected %q error, got %s", i, test.error, err.Error())
+		}
+	}
+}
+
+func TestDecodeErrorMultipleTypes(t *testing.T) {
+	type Test struct {
+		A string
+		B int
+	}
+	var b bytes.Buffer
+	NewEncoder(&b).Encode(Test{"one", 1})
+
+	var result, result2 Test
+	dec := NewDecoder(&b)
+	err := dec.Decode(&result)
+	if err != nil {
+		t.Errorf("decode: unexpected error %v", err)
+	}
+
+	b.Reset()
+	NewEncoder(&b).Encode(Test{"two", 2})
+	err = dec.Decode(&result2)
+	if err == nil {
+		t.Errorf("decode: expected duplicate type error, got nil")
+	} else if !strings.Contains(err.Error(), "duplicate type") {
+		t.Errorf("decode: expected duplicate type error, got %s", err.Error())
+	}
+}
+
+// Issue 24075
+func TestMarshalFloatMap(t *testing.T) {
+	nan1 := math.NaN()
+	nan2 := math.Float64frombits(math.Float64bits(nan1) ^ 1) // A different NaN in the same class.
+
+	in := map[float64]string{
+		nan1: "a",
+		nan1: "b",
+		nan2: "c",
+	}
+
+	var b bytes.Buffer
+	enc := NewEncoder(&b)
+	if err := enc.Encode(in); err != nil {
+		t.Errorf("Encode : %v", err)
+	}
+
+	out := map[float64]string{}
+	dec := NewDecoder(&b)
+	if err := dec.Decode(&out); err != nil {
+		t.Fatalf("Decode : %v", err)
+	}
+
+	type mapEntry struct {
+		keyBits uint64
+		value   string
+	}
+	readMap := func(m map[float64]string) (entries []mapEntry) {
+		for k, v := range m {
+			entries = append(entries, mapEntry{math.Float64bits(k), v})
+		}
+		sort.Slice(entries, func(i, j int) bool {
+			ei, ej := entries[i], entries[j]
+			if ei.keyBits != ej.keyBits {
+				return ei.keyBits < ej.keyBits
+			}
+			return ei.value < ej.value
+		})
+		return entries
+	}
+
+	got := readMap(out)
+	want := readMap(in)
+	if !reflect.DeepEqual(got, want) {
+		t.Fatalf("\nEncode: %v\nDecode: %v", want, got)
+	}
+}
+
+func TestDecodePartial(t *testing.T) {
+	type T struct {
+		X []int
+		Y string
+	}
+
+	var buf bytes.Buffer
+	t1 := T{X: []int{1, 2, 3}, Y: "foo"}
+	t2 := T{X: []int{4, 5, 6}, Y: "bar"}
+	enc := NewEncoder(&buf)
+
+	t1start := 0
+	if err := enc.Encode(&t1); err != nil {
+		t.Fatal(err)
+	}
+
+	t2start := buf.Len()
+	if err := enc.Encode(&t2); err != nil {
+		t.Fatal(err)
+	}
+
+	data := buf.Bytes()
+	for i := 0; i <= len(data); i++ {
+		bufr := bytes.NewReader(data[:i])
+
+		// Decode both values, stopping at the first error.
+		var t1b, t2b T
+		dec := NewDecoder(bufr)
+		var err error
+		err = dec.Decode(&t1b)
+		if err == nil {
+			err = dec.Decode(&t2b)
+		}
+
+		switch i {
+		case t1start, t2start:
+			// Either the first or the second Decode calls had zero input.
+			if err != io.EOF {
+				t.Errorf("%d/%d: expected io.EOF: %v", i, len(data), err)
+			}
+		case len(data):
+			// We reached the end of the entire input.
+			if err != nil {
+				t.Errorf("%d/%d: unexpected error: %v", i, len(data), err)
+			}
+			if !reflect.DeepEqual(t1b, t1) {
+				t.Fatalf("t1 value mismatch: got %v, want %v", t1b, t1)
+			}
+			if !reflect.DeepEqual(t2b, t2) {
+				t.Fatalf("t2 value mismatch: got %v, want %v", t2b, t2)
+			}
+		default:
+			// In between, we must see io.ErrUnexpectedEOF.
+			// The decoder used to erroneously return io.EOF in some cases here,
+			// such as if the input was cut off right after some type specs,
+			// but before any value was actually transmitted.
+			if err != io.ErrUnexpectedEOF {
+				t.Errorf("%d/%d: expected io.ErrUnexpectedEOF: %v", i, len(data), err)
+			}
+		}
+	}
+}
diff --git a/src/encoding/gob/error.go b/src/encoding/gob/error.go
new file mode 100644
index 0000000..3c9515b
--- /dev/null
+++ b/src/encoding/gob/error.go
@@ -0,0 +1,42 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package gob
+
+import "fmt"
+
+// Errors in decoding and encoding are handled using panic and recover.
+// Panics caused by user error (that is, everything except run-time panics
+// such as "index out of bounds" errors) do not leave the file that caused
+// them, but are instead turned into plain error returns. Encoding and
+// decoding functions and methods that do not return an error either use
+// panic to report an error or are guaranteed error-free.
+
+// A gobError is used to distinguish errors (panics) generated in this package.
+type gobError struct {
+	err error
+}
+
+// errorf is like error_ but takes Printf-style arguments to construct an error.
+// It always prefixes the message with "gob: ".
+func errorf(format string, args ...any) {
+	error_(fmt.Errorf("gob: "+format, args...))
+}
+
+// error wraps the argument error and uses it as the argument to panic.
+func error_(err error) {
+	panic(gobError{err})
+}
+
+// catchError is meant to be used as a deferred function to turn a panic(gobError) into a
+// plain error. It overwrites the error return of the function that deferred its call.
+func catchError(err *error) {
+	if e := recover(); e != nil {
+		ge, ok := e.(gobError)
+		if !ok {
+			panic(e)
+		}
+		*err = ge.err
+	}
+}
diff --git a/src/encoding/gob/example_encdec_test.go b/src/encoding/gob/example_encdec_test.go
new file mode 100644
index 0000000..e45ad4c
--- /dev/null
+++ b/src/encoding/gob/example_encdec_test.go
@@ -0,0 +1,61 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package gob_test
+
+import (
+	"bytes"
+	"encoding/gob"
+	"fmt"
+	"log"
+)
+
+// The Vector type has unexported fields, which the package cannot access.
+// We therefore write a BinaryMarshal/BinaryUnmarshal method pair to allow us
+// to send and receive the type with the gob package. These interfaces are
+// defined in the "encoding" package.
+// We could equivalently use the locally defined GobEncode/GobDecoder
+// interfaces.
+type Vector struct {
+	x, y, z int
+}
+
+func (v Vector) MarshalBinary() ([]byte, error) {
+	// A simple encoding: plain text.
+	var b bytes.Buffer
+	fmt.Fprintln(&b, v.x, v.y, v.z)
+	return b.Bytes(), nil
+}
+
+// UnmarshalBinary modifies the receiver so it must take a pointer receiver.
+func (v *Vector) UnmarshalBinary(data []byte) error {
+	// A simple encoding: plain text.
+	b := bytes.NewBuffer(data)
+	_, err := fmt.Fscanln(b, &v.x, &v.y, &v.z)
+	return err
+}
+
+// This example transmits a value that implements the custom encoding and decoding methods.
+func Example_encodeDecode() {
+	var network bytes.Buffer // Stand-in for the network.
+
+	// Create an encoder and send a value.
+	enc := gob.NewEncoder(&network)
+	err := enc.Encode(Vector{3, 4, 5})
+	if err != nil {
+		log.Fatal("encode:", err)
+	}
+
+	// Create a decoder and receive a value.
+	dec := gob.NewDecoder(&network)
+	var v Vector
+	err = dec.Decode(&v)
+	if err != nil {
+		log.Fatal("decode:", err)
+	}
+	fmt.Println(v)
+
+	// Output:
+	// {3 4 5}
+}
diff --git a/src/encoding/gob/example_interface_test.go b/src/encoding/gob/example_interface_test.go
new file mode 100644
index 0000000..cf5ba38
--- /dev/null
+++ b/src/encoding/gob/example_interface_test.go
@@ -0,0 +1,81 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package gob_test
+
+import (
+	"bytes"
+	"encoding/gob"
+	"fmt"
+	"log"
+	"math"
+)
+
+type Point struct {
+	X, Y int
+}
+
+func (p Point) Hypotenuse() float64 {
+	return math.Hypot(float64(p.X), float64(p.Y))
+}
+
+type Pythagoras interface {
+	Hypotenuse() float64
+}
+
+// This example shows how to encode an interface value. The key
+// distinction from regular types is to register the concrete type that
+// implements the interface.
+func Example_interface() {
+	var network bytes.Buffer // Stand-in for the network.
+
+	// We must register the concrete type for the encoder and decoder (which would
+	// normally be on a separate machine from the encoder). On each end, this tells the
+	// engine which concrete type is being sent that implements the interface.
+	gob.Register(Point{})
+
+	// Create an encoder and send some values.
+	enc := gob.NewEncoder(&network)
+	for i := 1; i <= 3; i++ {
+		interfaceEncode(enc, Point{3 * i, 4 * i})
+	}
+
+	// Create a decoder and receive some values.
+	dec := gob.NewDecoder(&network)
+	for i := 1; i <= 3; i++ {
+		result := interfaceDecode(dec)
+		fmt.Println(result.Hypotenuse())
+	}
+
+	// Output:
+	// 5
+	// 10
+	// 15
+}
+
+// interfaceEncode encodes the interface value into the encoder.
+func interfaceEncode(enc *gob.Encoder, p Pythagoras) {
+	// The encode will fail unless the concrete type has been
+	// registered. We registered it in the calling function.
+
+	// Pass pointer to interface so Encode sees (and hence sends) a value of
+	// interface type. If we passed p directly it would see the concrete type instead.
+	// See the blog post, "The Laws of Reflection" for background.
+	err := enc.Encode(&p)
+	if err != nil {
+		log.Fatal("encode:", err)
+	}
+}
+
+// interfaceDecode decodes the next interface value from the stream and returns it.
+func interfaceDecode(dec *gob.Decoder) Pythagoras {
+	// The decode will fail unless the concrete type on the wire has been
+	// registered. We registered it in the calling function.
+	var p Pythagoras
+	err := dec.Decode(&p)
+	if err != nil {
+		log.Fatal("decode:", err)
+	}
+	return p
+}
diff --git a/src/encoding/gob/example_test.go b/src/encoding/gob/example_test.go
new file mode 100644
index 0000000..16b7123
--- /dev/null
+++ b/src/encoding/gob/example_test.go
@@ -0,0 +1,60 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package gob_test
+
+import (
+	"bytes"
+	"encoding/gob"
+	"fmt"
+	"log"
+)
+
+type P struct {
+	X, Y, Z int
+	Name    string
+}
+
+type Q struct {
+	X, Y *int32
+	Name string
+}
+
+// This example shows the basic usage of the package: Create an encoder,
+// transmit some values, receive them with a decoder.
+func Example_basic() {
+	// Initialize the encoder and decoder. Normally enc and dec would be
+	// bound to network connections and the encoder and decoder would
+	// run in different processes.
+	var network bytes.Buffer        // Stand-in for a network connection
+	enc := gob.NewEncoder(&network) // Will write to network.
+	dec := gob.NewDecoder(&network) // Will read from network.
+
+	// Encode (send) some values.
+	err := enc.Encode(P{3, 4, 5, "Pythagoras"})
+	if err != nil {
+		log.Fatal("encode error:", err)
+	}
+	err = enc.Encode(P{1782, 1841, 1922, "Treehouse"})
+	if err != nil {
+		log.Fatal("encode error:", err)
+	}
+
+	// Decode (receive) and print the values.
+	var q Q
+	err = dec.Decode(&q)
+	if err != nil {
+		log.Fatal("decode error 1:", err)
+	}
+	fmt.Printf("%q: {%d, %d}\n", q.Name, *q.X, *q.Y)
+	err = dec.Decode(&q)
+	if err != nil {
+		log.Fatal("decode error 2:", err)
+	}
+	fmt.Printf("%q: {%d, %d}\n", q.Name, *q.X, *q.Y)
+
+	// Output:
+	// "Pythagoras": {3, 4}
+	// "Treehouse": {1782, 1841}
+}
diff --git a/src/encoding/gob/gobencdec_test.go b/src/encoding/gob/gobencdec_test.go
new file mode 100644
index 0000000..3d49887
--- /dev/null
+++ b/src/encoding/gob/gobencdec_test.go
@@ -0,0 +1,822 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file contains tests of the GobEncoder/GobDecoder support.
+
+package gob
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"net"
+	"reflect"
+	"strings"
+	"testing"
+	"time"
+)
+
+// Types that implement the GobEncoder/Decoder interfaces.
+
+type ByteStruct struct {
+	a byte // not an exported field
+}
+
+type StringStruct struct {
+	s string // not an exported field
+}
+
+type ArrayStruct struct {
+	a [8192]byte // not an exported field
+}
+
+type Gobber int
+
+type ValueGobber string // encodes with a value, decodes with a pointer.
+
+type BinaryGobber int
+
+type BinaryValueGobber string
+
+type TextGobber int
+
+type TextValueGobber string
+
+// The relevant methods
+
+func (g *ByteStruct) GobEncode() ([]byte, error) {
+	b := make([]byte, 3)
+	b[0] = g.a
+	b[1] = g.a + 1
+	b[2] = g.a + 2
+	return b, nil
+}
+
+func (g *ByteStruct) GobDecode(data []byte) error {
+	if g == nil {
+		return errors.New("NIL RECEIVER")
+	}
+	// Expect N sequential-valued bytes.
+	if len(data) == 0 {
+		return io.EOF
+	}
+	g.a = data[0]
+	for i, c := range data {
+		if c != g.a+byte(i) {
+			return errors.New("invalid data sequence")
+		}
+	}
+	return nil
+}
+
+func (g *StringStruct) GobEncode() ([]byte, error) {
+	return []byte(g.s), nil
+}
+
+func (g *StringStruct) GobDecode(data []byte) error {
+	// Expect N sequential-valued bytes.
+	if len(data) == 0 {
+		return io.EOF
+	}
+	a := data[0]
+	for i, c := range data {
+		if c != a+byte(i) {
+			return errors.New("invalid data sequence")
+		}
+	}
+	g.s = string(data)
+	return nil
+}
+
+func (a *ArrayStruct) GobEncode() ([]byte, error) {
+	return a.a[:], nil
+}
+
+func (a *ArrayStruct) GobDecode(data []byte) error {
+	if len(data) != len(a.a) {
+		return errors.New("wrong length in array decode")
+	}
+	copy(a.a[:], data)
+	return nil
+}
+
+func (g *Gobber) GobEncode() ([]byte, error) {
+	return []byte(fmt.Sprintf("VALUE=%d", *g)), nil
+}
+
+func (g *Gobber) GobDecode(data []byte) error {
+	_, err := fmt.Sscanf(string(data), "VALUE=%d", (*int)(g))
+	return err
+}
+
+func (g *BinaryGobber) MarshalBinary() ([]byte, error) {
+	return []byte(fmt.Sprintf("VALUE=%d", *g)), nil
+}
+
+func (g *BinaryGobber) UnmarshalBinary(data []byte) error {
+	_, err := fmt.Sscanf(string(data), "VALUE=%d", (*int)(g))
+	return err
+}
+
+func (g *TextGobber) MarshalText() ([]byte, error) {
+	return []byte(fmt.Sprintf("VALUE=%d", *g)), nil
+}
+
+func (g *TextGobber) UnmarshalText(data []byte) error {
+	_, err := fmt.Sscanf(string(data), "VALUE=%d", (*int)(g))
+	return err
+}
+
+func (v ValueGobber) GobEncode() ([]byte, error) {
+	return []byte(fmt.Sprintf("VALUE=%s", v)), nil
+}
+
+func (v *ValueGobber) GobDecode(data []byte) error {
+	_, err := fmt.Sscanf(string(data), "VALUE=%s", (*string)(v))
+	return err
+}
+
+func (v BinaryValueGobber) MarshalBinary() ([]byte, error) {
+	return []byte(fmt.Sprintf("VALUE=%s", v)), nil
+}
+
+func (v *BinaryValueGobber) UnmarshalBinary(data []byte) error {
+	_, err := fmt.Sscanf(string(data), "VALUE=%s", (*string)(v))
+	return err
+}
+
+func (v TextValueGobber) MarshalText() ([]byte, error) {
+	return []byte(fmt.Sprintf("VALUE=%s", v)), nil
+}
+
+func (v *TextValueGobber) UnmarshalText(data []byte) error {
+	_, err := fmt.Sscanf(string(data), "VALUE=%s", (*string)(v))
+	return err
+}
+
+// Structs that include GobEncodable fields.
+
+type GobTest0 struct {
+	X int // guarantee we have  something in common with GobTest*
+	G *ByteStruct
+}
+
+type GobTest1 struct {
+	X int // guarantee we have  something in common with GobTest*
+	G *StringStruct
+}
+
+type GobTest2 struct {
+	X int    // guarantee we have  something in common with GobTest*
+	G string // not a GobEncoder - should give us errors
+}
+
+type GobTest3 struct {
+	X int // guarantee we have  something in common with GobTest*
+	G *Gobber
+	B *BinaryGobber
+	T *TextGobber
+}
+
+type GobTest4 struct {
+	X  int // guarantee we have  something in common with GobTest*
+	V  ValueGobber
+	BV BinaryValueGobber
+	TV TextValueGobber
+}
+
+type GobTest5 struct {
+	X  int // guarantee we have  something in common with GobTest*
+	V  *ValueGobber
+	BV *BinaryValueGobber
+	TV *TextValueGobber
+}
+
+type GobTest6 struct {
+	X  int // guarantee we have  something in common with GobTest*
+	V  ValueGobber
+	W  *ValueGobber
+	BV BinaryValueGobber
+	BW *BinaryValueGobber
+	TV TextValueGobber
+	TW *TextValueGobber
+}
+
+type GobTest7 struct {
+	X  int // guarantee we have  something in common with GobTest*
+	V  *ValueGobber
+	W  ValueGobber
+	BV *BinaryValueGobber
+	BW BinaryValueGobber
+	TV *TextValueGobber
+	TW TextValueGobber
+}
+
+type GobTestIgnoreEncoder struct {
+	X int // guarantee we have  something in common with GobTest*
+}
+
+type GobTestValueEncDec struct {
+	X int          // guarantee we have  something in common with GobTest*
+	G StringStruct // not a pointer.
+}
+
+type GobTestIndirectEncDec struct {
+	X int             // guarantee we have  something in common with GobTest*
+	G ***StringStruct // indirections to the receiver.
+}
+
+type GobTestArrayEncDec struct {
+	X int         // guarantee we have  something in common with GobTest*
+	A ArrayStruct // not a pointer.
+}
+
+type GobTestIndirectArrayEncDec struct {
+	X int            // guarantee we have  something in common with GobTest*
+	A ***ArrayStruct // indirections to a large receiver.
+}
+
+func TestGobEncoderField(t *testing.T) {
+	b := new(bytes.Buffer)
+	// First a field that's a structure.
+	enc := NewEncoder(b)
+	err := enc.Encode(GobTest0{17, &ByteStruct{'A'}})
+	if err != nil {
+		t.Fatal("encode error:", err)
+	}
+	dec := NewDecoder(b)
+	x := new(GobTest0)
+	err = dec.Decode(x)
+	if err != nil {
+		t.Fatal("decode error:", err)
+	}
+	if x.G.a != 'A' {
+		t.Errorf("expected 'A' got %c", x.G.a)
+	}
+	// Now a field that's not a structure.
+	b.Reset()
+	gobber := Gobber(23)
+	bgobber := BinaryGobber(24)
+	tgobber := TextGobber(25)
+	err = enc.Encode(GobTest3{17, &gobber, &bgobber, &tgobber})
+	if err != nil {
+		t.Fatal("encode error:", err)
+	}
+	y := new(GobTest3)
+	err = dec.Decode(y)
+	if err != nil {
+		t.Fatal("decode error:", err)
+	}
+	if *y.G != 23 || *y.B != 24 || *y.T != 25 {
+		t.Errorf("expected '23 got %d", *y.G)
+	}
+}
+
+// Even though the field is a value, we can still take its address
+// and should be able to call the methods.
+func TestGobEncoderValueField(t *testing.T) {
+	b := new(bytes.Buffer)
+	// First a field that's a structure.
+	enc := NewEncoder(b)
+	err := enc.Encode(&GobTestValueEncDec{17, StringStruct{"HIJKL"}})
+	if err != nil {
+		t.Fatal("encode error:", err)
+	}
+	dec := NewDecoder(b)
+	x := new(GobTestValueEncDec)
+	err = dec.Decode(x)
+	if err != nil {
+		t.Fatal("decode error:", err)
+	}
+	if x.G.s != "HIJKL" {
+		t.Errorf("expected `HIJKL` got %s", x.G.s)
+	}
+}
+
+// GobEncode/Decode should work even if the value is
+// more indirect than the receiver.
+func TestGobEncoderIndirectField(t *testing.T) {
+	b := new(bytes.Buffer)
+	// First a field that's a structure.
+	enc := NewEncoder(b)
+	s := &StringStruct{"HIJKL"}
+	sp := &s
+	err := enc.Encode(GobTestIndirectEncDec{17, &sp})
+	if err != nil {
+		t.Fatal("encode error:", err)
+	}
+	dec := NewDecoder(b)
+	x := new(GobTestIndirectEncDec)
+	err = dec.Decode(x)
+	if err != nil {
+		t.Fatal("decode error:", err)
+	}
+	if (***x.G).s != "HIJKL" {
+		t.Errorf("expected `HIJKL` got %s", (***x.G).s)
+	}
+}
+
+// Test with a large field with methods.
+func TestGobEncoderArrayField(t *testing.T) {
+	b := new(bytes.Buffer)
+	enc := NewEncoder(b)
+	var a GobTestArrayEncDec
+	a.X = 17
+	for i := range a.A.a {
+		a.A.a[i] = byte(i)
+	}
+	err := enc.Encode(&a)
+	if err != nil {
+		t.Fatal("encode error:", err)
+	}
+	dec := NewDecoder(b)
+	x := new(GobTestArrayEncDec)
+	err = dec.Decode(x)
+	if err != nil {
+		t.Fatal("decode error:", err)
+	}
+	for i, v := range x.A.a {
+		if v != byte(i) {
+			t.Errorf("expected %x got %x", byte(i), v)
+			break
+		}
+	}
+}
+
+// Test an indirection to a large field with methods.
+func TestGobEncoderIndirectArrayField(t *testing.T) {
+	b := new(bytes.Buffer)
+	enc := NewEncoder(b)
+	var a GobTestIndirectArrayEncDec
+	a.X = 17
+	var array ArrayStruct
+	ap := &array
+	app := &ap
+	a.A = &app
+	for i := range array.a {
+		array.a[i] = byte(i)
+	}
+	err := enc.Encode(a)
+	if err != nil {
+		t.Fatal("encode error:", err)
+	}
+	dec := NewDecoder(b)
+	x := new(GobTestIndirectArrayEncDec)
+	err = dec.Decode(x)
+	if err != nil {
+		t.Fatal("decode error:", err)
+	}
+	for i, v := range (***x.A).a {
+		if v != byte(i) {
+			t.Errorf("expected %x got %x", byte(i), v)
+			break
+		}
+	}
+}
+
+// As long as the fields have the same name and implement the
+// interface, we can cross-connect them. Not sure it's useful
+// and may even be bad but it works and it's hard to prevent
+// without exposing the contents of the object, which would
+// defeat the purpose.
+func TestGobEncoderFieldsOfDifferentType(t *testing.T) {
+	// first, string in field to byte in field
+	b := new(bytes.Buffer)
+	enc := NewEncoder(b)
+	err := enc.Encode(GobTest1{17, &StringStruct{"ABC"}})
+	if err != nil {
+		t.Fatal("encode error:", err)
+	}
+	dec := NewDecoder(b)
+	x := new(GobTest0)
+	err = dec.Decode(x)
+	if err != nil {
+		t.Fatal("decode error:", err)
+	}
+	if x.G.a != 'A' {
+		t.Errorf("expected 'A' got %c", x.G.a)
+	}
+	// now the other direction, byte in field to string in field
+	b.Reset()
+	err = enc.Encode(GobTest0{17, &ByteStruct{'X'}})
+	if err != nil {
+		t.Fatal("encode error:", err)
+	}
+	y := new(GobTest1)
+	err = dec.Decode(y)
+	if err != nil {
+		t.Fatal("decode error:", err)
+	}
+	if y.G.s != "XYZ" {
+		t.Fatalf("expected `XYZ` got %q", y.G.s)
+	}
+}
+
+// Test that we can encode a value and decode into a pointer.
+func TestGobEncoderValueEncoder(t *testing.T) {
+	// first, string in field to byte in field
+	b := new(bytes.Buffer)
+	enc := NewEncoder(b)
+	err := enc.Encode(GobTest4{17, ValueGobber("hello"), BinaryValueGobber("Καλημέρα"), TextValueGobber("こんにちは")})
+	if err != nil {
+		t.Fatal("encode error:", err)
+	}
+	dec := NewDecoder(b)
+	x := new(GobTest5)
+	err = dec.Decode(x)
+	if err != nil {
+		t.Fatal("decode error:", err)
+	}
+	if *x.V != "hello" || *x.BV != "Καλημέρα" || *x.TV != "こんにちは" {
+		t.Errorf("expected `hello` got %s", *x.V)
+	}
+}
+
+// Test that we can use a value then a pointer type of a GobEncoder
+// in the same encoded value. Bug 4647.
+func TestGobEncoderValueThenPointer(t *testing.T) {
+	v := ValueGobber("forty-two")
+	w := ValueGobber("six-by-nine")
+	bv := BinaryValueGobber("1nanocentury")
+	bw := BinaryValueGobber("πseconds")
+	tv := TextValueGobber("gravitationalacceleration")
+	tw := TextValueGobber("π²ft/s²")
+
+	// this was a bug: encoding a GobEncoder by value before a GobEncoder
+	// pointer would cause duplicate type definitions to be sent.
+
+	b := new(bytes.Buffer)
+	enc := NewEncoder(b)
+	if err := enc.Encode(GobTest6{42, v, &w, bv, &bw, tv, &tw}); err != nil {
+		t.Fatal("encode error:", err)
+	}
+	dec := NewDecoder(b)
+	x := new(GobTest6)
+	if err := dec.Decode(x); err != nil {
+		t.Fatal("decode error:", err)
+	}
+
+	if got, want := x.V, v; got != want {
+		t.Errorf("v = %q, want %q", got, want)
+	}
+	if got, want := x.W, w; got == nil {
+		t.Errorf("w = nil, want %q", want)
+	} else if *got != want {
+		t.Errorf("w = %q, want %q", *got, want)
+	}
+
+	if got, want := x.BV, bv; got != want {
+		t.Errorf("bv = %q, want %q", got, want)
+	}
+	if got, want := x.BW, bw; got == nil {
+		t.Errorf("bw = nil, want %q", want)
+	} else if *got != want {
+		t.Errorf("bw = %q, want %q", *got, want)
+	}
+
+	if got, want := x.TV, tv; got != want {
+		t.Errorf("tv = %q, want %q", got, want)
+	}
+	if got, want := x.TW, tw; got == nil {
+		t.Errorf("tw = nil, want %q", want)
+	} else if *got != want {
+		t.Errorf("tw = %q, want %q", *got, want)
+	}
+}
+
+// Test that we can use a pointer then a value type of a GobEncoder
+// in the same encoded value.
+func TestGobEncoderPointerThenValue(t *testing.T) {
+	v := ValueGobber("forty-two")
+	w := ValueGobber("six-by-nine")
+	bv := BinaryValueGobber("1nanocentury")
+	bw := BinaryValueGobber("πseconds")
+	tv := TextValueGobber("gravitationalacceleration")
+	tw := TextValueGobber("π²ft/s²")
+
+	b := new(bytes.Buffer)
+	enc := NewEncoder(b)
+	if err := enc.Encode(GobTest7{42, &v, w, &bv, bw, &tv, tw}); err != nil {
+		t.Fatal("encode error:", err)
+	}
+	dec := NewDecoder(b)
+	x := new(GobTest7)
+	if err := dec.Decode(x); err != nil {
+		t.Fatal("decode error:", err)
+	}
+
+	if got, want := x.V, v; got == nil {
+		t.Errorf("v = nil, want %q", want)
+	} else if *got != want {
+		t.Errorf("v = %q, want %q", *got, want)
+	}
+	if got, want := x.W, w; got != want {
+		t.Errorf("w = %q, want %q", got, want)
+	}
+
+	if got, want := x.BV, bv; got == nil {
+		t.Errorf("bv = nil, want %q", want)
+	} else if *got != want {
+		t.Errorf("bv = %q, want %q", *got, want)
+	}
+	if got, want := x.BW, bw; got != want {
+		t.Errorf("bw = %q, want %q", got, want)
+	}
+
+	if got, want := x.TV, tv; got == nil {
+		t.Errorf("tv = nil, want %q", want)
+	} else if *got != want {
+		t.Errorf("tv = %q, want %q", *got, want)
+	}
+	if got, want := x.TW, tw; got != want {
+		t.Errorf("tw = %q, want %q", got, want)
+	}
+}
+
+func TestGobEncoderFieldTypeError(t *testing.T) {
+	// GobEncoder to non-decoder: error
+	b := new(bytes.Buffer)
+	enc := NewEncoder(b)
+	err := enc.Encode(GobTest1{17, &StringStruct{"ABC"}})
+	if err != nil {
+		t.Fatal("encode error:", err)
+	}
+	dec := NewDecoder(b)
+	x := &GobTest2{}
+	err = dec.Decode(x)
+	if err == nil {
+		t.Fatal("expected decode error for mismatched fields (encoder to non-decoder)")
+	}
+	if !strings.Contains(err.Error(), "type") {
+		t.Fatal("expected type error; got", err)
+	}
+	// Non-encoder to GobDecoder: error
+	b.Reset()
+	err = enc.Encode(GobTest2{17, "ABC"})
+	if err != nil {
+		t.Fatal("encode error:", err)
+	}
+	y := &GobTest1{}
+	err = dec.Decode(y)
+	if err == nil {
+		t.Fatal("expected decode error for mismatched fields (non-encoder to decoder)")
+	}
+	if !strings.Contains(err.Error(), "type") {
+		t.Fatal("expected type error; got", err)
+	}
+}
+
+// Even though ByteStruct is a struct, it's treated as a singleton at the top level.
+func TestGobEncoderStructSingleton(t *testing.T) {
+	b := new(bytes.Buffer)
+	enc := NewEncoder(b)
+	err := enc.Encode(&ByteStruct{'A'})
+	if err != nil {
+		t.Fatal("encode error:", err)
+	}
+	dec := NewDecoder(b)
+	x := new(ByteStruct)
+	err = dec.Decode(x)
+	if err != nil {
+		t.Fatal("decode error:", err)
+	}
+	if x.a != 'A' {
+		t.Errorf("expected 'A' got %c", x.a)
+	}
+}
+
+func TestGobEncoderNonStructSingleton(t *testing.T) {
+	b := new(bytes.Buffer)
+	enc := NewEncoder(b)
+	var g Gobber = 1234
+	err := enc.Encode(&g)
+	if err != nil {
+		t.Fatal("encode error:", err)
+	}
+	dec := NewDecoder(b)
+	var x Gobber
+	err = dec.Decode(&x)
+	if err != nil {
+		t.Fatal("decode error:", err)
+	}
+	if x != 1234 {
+		t.Errorf("expected 1234 got %d", x)
+	}
+}
+
+func TestGobEncoderIgnoreStructField(t *testing.T) {
+	b := new(bytes.Buffer)
+	// First a field that's a structure.
+	enc := NewEncoder(b)
+	err := enc.Encode(GobTest0{17, &ByteStruct{'A'}})
+	if err != nil {
+		t.Fatal("encode error:", err)
+	}
+	dec := NewDecoder(b)
+	x := new(GobTestIgnoreEncoder)
+	err = dec.Decode(x)
+	if err != nil {
+		t.Fatal("decode error:", err)
+	}
+	if x.X != 17 {
+		t.Errorf("expected 17 got %c", x.X)
+	}
+}
+
+func TestGobEncoderIgnoreNonStructField(t *testing.T) {
+	b := new(bytes.Buffer)
+	// First a field that's a structure.
+	enc := NewEncoder(b)
+	gobber := Gobber(23)
+	bgobber := BinaryGobber(24)
+	tgobber := TextGobber(25)
+	err := enc.Encode(GobTest3{17, &gobber, &bgobber, &tgobber})
+	if err != nil {
+		t.Fatal("encode error:", err)
+	}
+	dec := NewDecoder(b)
+	x := new(GobTestIgnoreEncoder)
+	err = dec.Decode(x)
+	if err != nil {
+		t.Fatal("decode error:", err)
+	}
+	if x.X != 17 {
+		t.Errorf("expected 17 got %c", x.X)
+	}
+}
+
+func TestGobEncoderIgnoreNilEncoder(t *testing.T) {
+	b := new(bytes.Buffer)
+	// First a field that's a structure.
+	enc := NewEncoder(b)
+	err := enc.Encode(GobTest0{X: 18}) // G is nil
+	if err != nil {
+		t.Fatal("encode error:", err)
+	}
+	dec := NewDecoder(b)
+	x := new(GobTest0)
+	err = dec.Decode(x)
+	if err != nil {
+		t.Fatal("decode error:", err)
+	}
+	if x.X != 18 {
+		t.Errorf("expected x.X = 18, got %v", x.X)
+	}
+	if x.G != nil {
+		t.Errorf("expected x.G = nil, got %v", x.G)
+	}
+}
+
+type gobDecoderBug0 struct {
+	foo, bar string
+}
+
+func (br *gobDecoderBug0) String() string {
+	return br.foo + "-" + br.bar
+}
+
+func (br *gobDecoderBug0) GobEncode() ([]byte, error) {
+	return []byte(br.String()), nil
+}
+
+func (br *gobDecoderBug0) GobDecode(b []byte) error {
+	br.foo = "foo"
+	br.bar = "bar"
+	return nil
+}
+
+// This was a bug: the receiver has a different indirection level
+// than the variable.
+func TestGobEncoderExtraIndirect(t *testing.T) {
+	gdb := &gobDecoderBug0{"foo", "bar"}
+	buf := new(bytes.Buffer)
+	e := NewEncoder(buf)
+	if err := e.Encode(gdb); err != nil {
+		t.Fatalf("encode: %v", err)
+	}
+	d := NewDecoder(buf)
+	var got *gobDecoderBug0
+	if err := d.Decode(&got); err != nil {
+		t.Fatalf("decode: %v", err)
+	}
+	if got.foo != gdb.foo || got.bar != gdb.bar {
+		t.Errorf("got = %q, want %q", got, gdb)
+	}
+}
+
+// Another bug: this caused a crash with the new Go1 Time type.
+// We throw in a gob-encoding array, to test another case of isZero,
+// and a struct containing a nil interface, to test a third.
+type isZeroBug struct {
+	T time.Time
+	S string
+	I int
+	A isZeroBugArray
+	F isZeroBugInterface
+}
+
+type isZeroBugArray [2]uint8
+
+// Receiver is value, not pointer, to test isZero of array.
+func (a isZeroBugArray) GobEncode() (b []byte, e error) {
+	b = append(b, a[:]...)
+	return b, nil
+}
+
+func (a *isZeroBugArray) GobDecode(data []byte) error {
+	if len(data) != len(a) {
+		return io.EOF
+	}
+	a[0] = data[0]
+	a[1] = data[1]
+	return nil
+}
+
+type isZeroBugInterface struct {
+	I any
+}
+
+func (i isZeroBugInterface) GobEncode() (b []byte, e error) {
+	return []byte{}, nil
+}
+
+func (i *isZeroBugInterface) GobDecode(data []byte) error {
+	return nil
+}
+
+func TestGobEncodeIsZero(t *testing.T) {
+	x := isZeroBug{time.Unix(1e9, 0), "hello", -55, isZeroBugArray{1, 2}, isZeroBugInterface{}}
+	b := new(bytes.Buffer)
+	enc := NewEncoder(b)
+	err := enc.Encode(x)
+	if err != nil {
+		t.Fatal("encode:", err)
+	}
+	var y isZeroBug
+	dec := NewDecoder(b)
+	err = dec.Decode(&y)
+	if err != nil {
+		t.Fatal("decode:", err)
+	}
+	if x != y {
+		t.Fatalf("%v != %v", x, y)
+	}
+}
+
+func TestGobEncodePtrError(t *testing.T) {
+	var err error
+	b := new(bytes.Buffer)
+	enc := NewEncoder(b)
+	err = enc.Encode(&err)
+	if err != nil {
+		t.Fatal("encode:", err)
+	}
+	dec := NewDecoder(b)
+	err2 := fmt.Errorf("foo")
+	err = dec.Decode(&err2)
+	if err != nil {
+		t.Fatal("decode:", err)
+	}
+	if err2 != nil {
+		t.Fatalf("expected nil, got %v", err2)
+	}
+}
+
+func TestNetIP(t *testing.T) {
+	// Encoding of net.IP{1,2,3,4} in Go 1.1.
+	enc := []byte{0x07, 0x0a, 0x00, 0x04, 0x01, 0x02, 0x03, 0x04}
+
+	var ip net.IP
+	err := NewDecoder(bytes.NewReader(enc)).Decode(&ip)
+	if err != nil {
+		t.Fatalf("decode: %v", err)
+	}
+	if ip.String() != "1.2.3.4" {
+		t.Errorf("decoded to %v, want 1.2.3.4", ip.String())
+	}
+}
+
+func TestIngoreDepthLimit(t *testing.T) {
+	// We don't test the actual depth limit because it requires building an
+	// extremely large message, which takes quite a while.
+	oldNestingDepth := maxIgnoreNestingDepth
+	maxIgnoreNestingDepth = 100
+	defer func() { maxIgnoreNestingDepth = oldNestingDepth }()
+	b := new(bytes.Buffer)
+	enc := NewEncoder(b)
+	typ := reflect.TypeOf(int(0))
+	nested := reflect.ArrayOf(1, typ)
+	for i := 0; i < 100; i++ {
+		nested = reflect.ArrayOf(1, nested)
+	}
+	badStruct := reflect.New(reflect.StructOf([]reflect.StructField{{Name: "F", Type: nested}}))
+	enc.Encode(badStruct.Interface())
+	dec := NewDecoder(b)
+	var output struct{ Hello int }
+	expectedErr := "invalid nesting depth"
+	if err := dec.Decode(&output); err == nil || err.Error() != expectedErr {
+		t.Errorf("Decode didn't fail with depth limit of 100: want %q, got %q", expectedErr, err)
+	}
+}
diff --git a/src/encoding/gob/timing_test.go b/src/encoding/gob/timing_test.go
new file mode 100644
index 0000000..bdee39c
--- /dev/null
+++ b/src/encoding/gob/timing_test.go
@@ -0,0 +1,328 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package gob
+
+import (
+	"bytes"
+	"io"
+	"os"
+	"reflect"
+	"runtime"
+	"testing"
+)
+
+type Bench struct {
+	A int
+	B float64
+	C string
+	D []byte
+}
+
+func benchmarkEndToEnd(b *testing.B, ctor func() any, pipe func() (r io.Reader, w io.Writer, err error)) {
+	b.RunParallel(func(pb *testing.PB) {
+		r, w, err := pipe()
+		if err != nil {
+			b.Fatal("can't get pipe:", err)
+		}
+		v := ctor()
+		enc := NewEncoder(w)
+		dec := NewDecoder(r)
+		for pb.Next() {
+			if err := enc.Encode(v); err != nil {
+				b.Fatal("encode error:", err)
+			}
+			if err := dec.Decode(v); err != nil {
+				b.Fatal("decode error:", err)
+			}
+		}
+	})
+}
+
+func BenchmarkEndToEndPipe(b *testing.B) {
+	benchmarkEndToEnd(b, func() any {
+		return &Bench{7, 3.2, "now is the time", bytes.Repeat([]byte("for all good men"), 100)}
+	}, func() (r io.Reader, w io.Writer, err error) {
+		r, w, err = os.Pipe()
+		return
+	})
+}
+
+func BenchmarkEndToEndByteBuffer(b *testing.B) {
+	benchmarkEndToEnd(b, func() any {
+		return &Bench{7, 3.2, "now is the time", bytes.Repeat([]byte("for all good men"), 100)}
+	}, func() (r io.Reader, w io.Writer, err error) {
+		var buf bytes.Buffer
+		return &buf, &buf, nil
+	})
+}
+
+func BenchmarkEndToEndSliceByteBuffer(b *testing.B) {
+	benchmarkEndToEnd(b, func() any {
+		v := &Bench{7, 3.2, "now is the time", nil}
+		Register(v)
+		arr := make([]any, 100)
+		for i := range arr {
+			arr[i] = v
+		}
+		return &arr
+	}, func() (r io.Reader, w io.Writer, err error) {
+		var buf bytes.Buffer
+		return &buf, &buf, nil
+	})
+}
+
+func TestCountEncodeMallocs(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping malloc count in short mode")
+	}
+	if runtime.GOMAXPROCS(0) > 1 {
+		t.Skip("skipping; GOMAXPROCS>1")
+	}
+
+	const N = 1000
+
+	var buf bytes.Buffer
+	enc := NewEncoder(&buf)
+	bench := &Bench{7, 3.2, "now is the time", []byte("for all good men")}
+
+	allocs := testing.AllocsPerRun(N, func() {
+		err := enc.Encode(bench)
+		if err != nil {
+			t.Fatal("encode:", err)
+		}
+	})
+	if allocs != 0 {
+		t.Fatalf("mallocs per encode of type Bench: %v; wanted 0\n", allocs)
+	}
+}
+
+func TestCountDecodeMallocs(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping malloc count in short mode")
+	}
+	if runtime.GOMAXPROCS(0) > 1 {
+		t.Skip("skipping; GOMAXPROCS>1")
+	}
+
+	const N = 1000
+
+	var buf bytes.Buffer
+	enc := NewEncoder(&buf)
+	bench := &Bench{7, 3.2, "now is the time", []byte("for all good men")}
+
+	// Fill the buffer with enough to decode
+	testing.AllocsPerRun(N, func() {
+		err := enc.Encode(bench)
+		if err != nil {
+			t.Fatal("encode:", err)
+		}
+	})
+
+	dec := NewDecoder(&buf)
+	allocs := testing.AllocsPerRun(N, func() {
+		*bench = Bench{}
+		err := dec.Decode(&bench)
+		if err != nil {
+			t.Fatal("decode:", err)
+		}
+	})
+	if allocs != 3 {
+		t.Fatalf("mallocs per decode of type Bench: %v; wanted 3\n", allocs)
+	}
+}
+
+func benchmarkEncodeSlice(b *testing.B, a any) {
+	b.ResetTimer()
+	b.RunParallel(func(pb *testing.PB) {
+		var buf bytes.Buffer
+		enc := NewEncoder(&buf)
+
+		for pb.Next() {
+			buf.Reset()
+			err := enc.Encode(a)
+			if err != nil {
+				b.Fatal(err)
+			}
+		}
+	})
+}
+
+func BenchmarkEncodeComplex128Slice(b *testing.B) {
+	a := make([]complex128, 1000)
+	for i := range a {
+		a[i] = 1.2 + 3.4i
+	}
+	benchmarkEncodeSlice(b, a)
+}
+
+func BenchmarkEncodeFloat64Slice(b *testing.B) {
+	a := make([]float64, 1000)
+	for i := range a {
+		a[i] = 1.23e4
+	}
+	benchmarkEncodeSlice(b, a)
+}
+
+func BenchmarkEncodeInt32Slice(b *testing.B) {
+	a := make([]int32, 1000)
+	for i := range a {
+		a[i] = int32(i * 100)
+	}
+	benchmarkEncodeSlice(b, a)
+}
+
+func BenchmarkEncodeStringSlice(b *testing.B) {
+	a := make([]string, 1000)
+	for i := range a {
+		a[i] = "now is the time"
+	}
+	benchmarkEncodeSlice(b, a)
+}
+
+func BenchmarkEncodeInterfaceSlice(b *testing.B) {
+	a := make([]any, 1000)
+	for i := range a {
+		a[i] = "now is the time"
+	}
+	benchmarkEncodeSlice(b, a)
+}
+
+// benchmarkBuf is a read buffer we can reset
+type benchmarkBuf struct {
+	offset int
+	data   []byte
+}
+
+func (b *benchmarkBuf) Read(p []byte) (n int, err error) {
+	n = copy(p, b.data[b.offset:])
+	if n == 0 {
+		return 0, io.EOF
+	}
+	b.offset += n
+	return
+}
+
+func (b *benchmarkBuf) ReadByte() (c byte, err error) {
+	if b.offset >= len(b.data) {
+		return 0, io.EOF
+	}
+	c = b.data[b.offset]
+	b.offset++
+	return
+}
+
+func (b *benchmarkBuf) reset() {
+	b.offset = 0
+}
+
+func benchmarkDecodeSlice(b *testing.B, a any) {
+	var buf bytes.Buffer
+	enc := NewEncoder(&buf)
+	err := enc.Encode(a)
+	if err != nil {
+		b.Fatal(err)
+	}
+
+	ra := reflect.ValueOf(a)
+	rt := ra.Type()
+	b.ResetTimer()
+
+	b.RunParallel(func(pb *testing.PB) {
+		// TODO(#19025): Move per-thread allocation before ResetTimer.
+		rp := reflect.New(rt)
+		rp.Elem().Set(reflect.MakeSlice(rt, ra.Len(), ra.Cap()))
+		p := rp.Interface()
+
+		bbuf := benchmarkBuf{data: buf.Bytes()}
+
+		for pb.Next() {
+			bbuf.reset()
+			dec := NewDecoder(&bbuf)
+			err := dec.Decode(p)
+			if err != nil {
+				b.Fatal(err)
+			}
+		}
+	})
+}
+
+func BenchmarkDecodeComplex128Slice(b *testing.B) {
+	a := make([]complex128, 1000)
+	for i := range a {
+		a[i] = 1.2 + 3.4i
+	}
+	benchmarkDecodeSlice(b, a)
+}
+
+func BenchmarkDecodeFloat64Slice(b *testing.B) {
+	a := make([]float64, 1000)
+	for i := range a {
+		a[i] = 1.23e4
+	}
+	benchmarkDecodeSlice(b, a)
+}
+
+func BenchmarkDecodeInt32Slice(b *testing.B) {
+	a := make([]int32, 1000)
+	for i := range a {
+		a[i] = 1234
+	}
+	benchmarkDecodeSlice(b, a)
+}
+
+func BenchmarkDecodeStringSlice(b *testing.B) {
+	a := make([]string, 1000)
+	for i := range a {
+		a[i] = "now is the time"
+	}
+	benchmarkDecodeSlice(b, a)
+}
+func BenchmarkDecodeStringsSlice(b *testing.B) {
+	a := make([][]string, 1000)
+	for i := range a {
+		a[i] = []string{"now is the time"}
+	}
+	benchmarkDecodeSlice(b, a)
+}
+func BenchmarkDecodeBytesSlice(b *testing.B) {
+	a := make([][]byte, 1000)
+	for i := range a {
+		a[i] = []byte("now is the time")
+	}
+	benchmarkDecodeSlice(b, a)
+}
+
+func BenchmarkDecodeInterfaceSlice(b *testing.B) {
+	a := make([]any, 1000)
+	for i := range a {
+		a[i] = "now is the time"
+	}
+	benchmarkDecodeSlice(b, a)
+}
+
+func BenchmarkDecodeMap(b *testing.B) {
+	count := 1000
+	m := make(map[int]int, count)
+	for i := 0; i < count; i++ {
+		m[i] = i
+	}
+	var buf bytes.Buffer
+	enc := NewEncoder(&buf)
+	err := enc.Encode(m)
+	if err != nil {
+		b.Fatal(err)
+	}
+	bbuf := benchmarkBuf{data: buf.Bytes()}
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		var rm map[int]int
+		bbuf.reset()
+		dec := NewDecoder(&bbuf)
+		err := dec.Decode(&rm)
+		if err != nil {
+			b.Fatal(i, err)
+		}
+	}
+}
diff --git a/src/encoding/gob/type.go b/src/encoding/gob/type.go
new file mode 100644
index 0000000..6e2c724
--- /dev/null
+++ b/src/encoding/gob/type.go
@@ -0,0 +1,913 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package gob
+
+import (
+	"encoding"
+	"errors"
+	"fmt"
+	"os"
+	"reflect"
+	"sync"
+	"sync/atomic"
+	"unicode"
+	"unicode/utf8"
+)
+
+// userTypeInfo stores the information associated with a type the user has handed
+// to the package. It's computed once and stored in a map keyed by reflection
+// type.
+type userTypeInfo struct {
+	user        reflect.Type // the type the user handed us
+	base        reflect.Type // the base type after all indirections
+	indir       int          // number of indirections to reach the base type
+	externalEnc int          // xGob, xBinary, or xText
+	externalDec int          // xGob, xBinary or xText
+	encIndir    int8         // number of indirections to reach the receiver type; may be negative
+	decIndir    int8         // number of indirections to reach the receiver type; may be negative
+}
+
+// externalEncoding bits
+const (
+	xGob    = 1 + iota // GobEncoder or GobDecoder
+	xBinary            // encoding.BinaryMarshaler or encoding.BinaryUnmarshaler
+	xText              // encoding.TextMarshaler or encoding.TextUnmarshaler
+)
+
+var userTypeCache sync.Map // map[reflect.Type]*userTypeInfo
+
+// validType returns, and saves, the information associated with user-provided type rt.
+// If the user type is not valid, err will be non-nil. To be used when the error handler
+// is not set up.
+func validUserType(rt reflect.Type) (*userTypeInfo, error) {
+	if ui, ok := userTypeCache.Load(rt); ok {
+		return ui.(*userTypeInfo), nil
+	}
+
+	// Construct a new userTypeInfo and atomically add it to the userTypeCache.
+	// If we lose the race, we'll waste a little CPU and create a little garbage
+	// but return the existing value anyway.
+
+	ut := new(userTypeInfo)
+	ut.base = rt
+	ut.user = rt
+	// A type that is just a cycle of pointers (such as type T *T) cannot
+	// be represented in gobs, which need some concrete data. We use a
+	// cycle detection algorithm from Knuth, Vol 2, Section 3.1, Ex 6,
+	// pp 539-540.  As we step through indirections, run another type at
+	// half speed. If they meet up, there's a cycle.
+	slowpoke := ut.base // walks half as fast as ut.base
+	for {
+		pt := ut.base
+		if pt.Kind() != reflect.Pointer {
+			break
+		}
+		ut.base = pt.Elem()
+		if ut.base == slowpoke { // ut.base lapped slowpoke
+			// recursive pointer type.
+			return nil, errors.New("can't represent recursive pointer type " + ut.base.String())
+		}
+		if ut.indir%2 == 0 {
+			slowpoke = slowpoke.Elem()
+		}
+		ut.indir++
+	}
+
+	if ok, indir := implementsInterface(ut.user, gobEncoderInterfaceType); ok {
+		ut.externalEnc, ut.encIndir = xGob, indir
+	} else if ok, indir := implementsInterface(ut.user, binaryMarshalerInterfaceType); ok {
+		ut.externalEnc, ut.encIndir = xBinary, indir
+	}
+
+	// NOTE(rsc): Would like to allow MarshalText here, but results in incompatibility
+	// with older encodings for net.IP. See golang.org/issue/6760.
+	// } else if ok, indir := implementsInterface(ut.user, textMarshalerInterfaceType); ok {
+	// 	ut.externalEnc, ut.encIndir = xText, indir
+	// }
+
+	if ok, indir := implementsInterface(ut.user, gobDecoderInterfaceType); ok {
+		ut.externalDec, ut.decIndir = xGob, indir
+	} else if ok, indir := implementsInterface(ut.user, binaryUnmarshalerInterfaceType); ok {
+		ut.externalDec, ut.decIndir = xBinary, indir
+	}
+
+	// See note above.
+	// } else if ok, indir := implementsInterface(ut.user, textUnmarshalerInterfaceType); ok {
+	// 	ut.externalDec, ut.decIndir = xText, indir
+	// }
+
+	ui, _ := userTypeCache.LoadOrStore(rt, ut)
+	return ui.(*userTypeInfo), nil
+}
+
+var (
+	gobEncoderInterfaceType        = reflect.TypeOf((*GobEncoder)(nil)).Elem()
+	gobDecoderInterfaceType        = reflect.TypeOf((*GobDecoder)(nil)).Elem()
+	binaryMarshalerInterfaceType   = reflect.TypeOf((*encoding.BinaryMarshaler)(nil)).Elem()
+	binaryUnmarshalerInterfaceType = reflect.TypeOf((*encoding.BinaryUnmarshaler)(nil)).Elem()
+	textMarshalerInterfaceType     = reflect.TypeOf((*encoding.TextMarshaler)(nil)).Elem()
+	textUnmarshalerInterfaceType   = reflect.TypeOf((*encoding.TextUnmarshaler)(nil)).Elem()
+)
+
+// implementsInterface reports whether the type implements the
+// gobEncoder/gobDecoder interface.
+// It also returns the number of indirections required to get to the
+// implementation.
+func implementsInterface(typ, gobEncDecType reflect.Type) (success bool, indir int8) {
+	if typ == nil {
+		return
+	}
+	rt := typ
+	// The type might be a pointer and we need to keep
+	// dereferencing to the base type until we find an implementation.
+	for {
+		if rt.Implements(gobEncDecType) {
+			return true, indir
+		}
+		if p := rt; p.Kind() == reflect.Pointer {
+			indir++
+			if indir > 100 { // insane number of indirections
+				return false, 0
+			}
+			rt = p.Elem()
+			continue
+		}
+		break
+	}
+	// No luck yet, but if this is a base type (non-pointer), the pointer might satisfy.
+	if typ.Kind() != reflect.Pointer {
+		// Not a pointer, but does the pointer work?
+		if reflect.PointerTo(typ).Implements(gobEncDecType) {
+			return true, -1
+		}
+	}
+	return false, 0
+}
+
+// userType returns, and saves, the information associated with user-provided type rt.
+// If the user type is not valid, it calls error.
+func userType(rt reflect.Type) *userTypeInfo {
+	ut, err := validUserType(rt)
+	if err != nil {
+		error_(err)
+	}
+	return ut
+}
+
+// A typeId represents a gob Type as an integer that can be passed on the wire.
+// Internally, typeIds are used as keys to a map to recover the underlying type info.
+type typeId int32
+
+var nextId typeId       // incremented for each new type we build
+var typeLock sync.Mutex // set while building a type
+const firstUserId = 64  // lowest id number granted to user
+
+type gobType interface {
+	id() typeId
+	setId(id typeId)
+	name() string
+	string() string // not public; only for debugging
+	safeString(seen map[typeId]bool) string
+}
+
+var types = make(map[reflect.Type]gobType)
+var idToType = make(map[typeId]gobType)
+var builtinIdToType map[typeId]gobType // set in init() after builtins are established
+
+func setTypeId(typ gobType) {
+	// When building recursive types, someone may get there before us.
+	if typ.id() != 0 {
+		return
+	}
+	nextId++
+	typ.setId(nextId)
+	idToType[nextId] = typ
+}
+
+func (t typeId) gobType() gobType {
+	if t == 0 {
+		return nil
+	}
+	return idToType[t]
+}
+
+// string returns the string representation of the type associated with the typeId.
+func (t typeId) string() string {
+	if t.gobType() == nil {
+		return "<nil>"
+	}
+	return t.gobType().string()
+}
+
+// Name returns the name of the type associated with the typeId.
+func (t typeId) name() string {
+	if t.gobType() == nil {
+		return "<nil>"
+	}
+	return t.gobType().name()
+}
+
+// CommonType holds elements of all types.
+// It is a historical artifact, kept for binary compatibility and exported
+// only for the benefit of the package's encoding of type descriptors. It is
+// not intended for direct use by clients.
+type CommonType struct {
+	Name string
+	Id   typeId
+}
+
+func (t *CommonType) id() typeId { return t.Id }
+
+func (t *CommonType) setId(id typeId) { t.Id = id }
+
+func (t *CommonType) string() string { return t.Name }
+
+func (t *CommonType) safeString(seen map[typeId]bool) string {
+	return t.Name
+}
+
+func (t *CommonType) name() string { return t.Name }
+
+// Create and check predefined types
+// The string for tBytes is "bytes" not "[]byte" to signify its specialness.
+
+var (
+	// Primordial types, needed during initialization.
+	// Always passed as pointers so the interface{} type
+	// goes through without losing its interfaceness.
+	tBool      = bootstrapType("bool", (*bool)(nil), 1)
+	tInt       = bootstrapType("int", (*int)(nil), 2)
+	tUint      = bootstrapType("uint", (*uint)(nil), 3)
+	tFloat     = bootstrapType("float", (*float64)(nil), 4)
+	tBytes     = bootstrapType("bytes", (*[]byte)(nil), 5)
+	tString    = bootstrapType("string", (*string)(nil), 6)
+	tComplex   = bootstrapType("complex", (*complex128)(nil), 7)
+	tInterface = bootstrapType("interface", (*any)(nil), 8)
+	// Reserve some Ids for compatible expansion
+	tReserved7 = bootstrapType("_reserved1", (*struct{ r7 int })(nil), 9)
+	tReserved6 = bootstrapType("_reserved1", (*struct{ r6 int })(nil), 10)
+	tReserved5 = bootstrapType("_reserved1", (*struct{ r5 int })(nil), 11)
+	tReserved4 = bootstrapType("_reserved1", (*struct{ r4 int })(nil), 12)
+	tReserved3 = bootstrapType("_reserved1", (*struct{ r3 int })(nil), 13)
+	tReserved2 = bootstrapType("_reserved1", (*struct{ r2 int })(nil), 14)
+	tReserved1 = bootstrapType("_reserved1", (*struct{ r1 int })(nil), 15)
+)
+
+// Predefined because it's needed by the Decoder
+var tWireType = mustGetTypeInfo(reflect.TypeOf(wireType{})).id
+var wireTypeUserInfo *userTypeInfo // userTypeInfo of (*wireType)
+
+func init() {
+	// Some magic numbers to make sure there are no surprises.
+	checkId(16, tWireType)
+	checkId(17, mustGetTypeInfo(reflect.TypeOf(arrayType{})).id)
+	checkId(18, mustGetTypeInfo(reflect.TypeOf(CommonType{})).id)
+	checkId(19, mustGetTypeInfo(reflect.TypeOf(sliceType{})).id)
+	checkId(20, mustGetTypeInfo(reflect.TypeOf(structType{})).id)
+	checkId(21, mustGetTypeInfo(reflect.TypeOf(fieldType{})).id)
+	checkId(23, mustGetTypeInfo(reflect.TypeOf(mapType{})).id)
+
+	builtinIdToType = make(map[typeId]gobType)
+	for k, v := range idToType {
+		builtinIdToType[k] = v
+	}
+
+	// Move the id space upwards to allow for growth in the predefined world
+	// without breaking existing files.
+	if nextId > firstUserId {
+		panic(fmt.Sprintln("nextId too large:", nextId))
+	}
+	nextId = firstUserId
+	registerBasics()
+	wireTypeUserInfo = userType(reflect.TypeOf((*wireType)(nil)))
+}
+
+// Array type
+type arrayType struct {
+	CommonType
+	Elem typeId
+	Len  int
+}
+
+func newArrayType(name string) *arrayType {
+	a := &arrayType{CommonType{Name: name}, 0, 0}
+	return a
+}
+
+func (a *arrayType) init(elem gobType, len int) {
+	// Set our type id before evaluating the element's, in case it's our own.
+	setTypeId(a)
+	a.Elem = elem.id()
+	a.Len = len
+}
+
+func (a *arrayType) safeString(seen map[typeId]bool) string {
+	if seen[a.Id] {
+		return a.Name
+	}
+	seen[a.Id] = true
+	return fmt.Sprintf("[%d]%s", a.Len, a.Elem.gobType().safeString(seen))
+}
+
+func (a *arrayType) string() string { return a.safeString(make(map[typeId]bool)) }
+
+// GobEncoder type (something that implements the GobEncoder interface)
+type gobEncoderType struct {
+	CommonType
+}
+
+func newGobEncoderType(name string) *gobEncoderType {
+	g := &gobEncoderType{CommonType{Name: name}}
+	setTypeId(g)
+	return g
+}
+
+func (g *gobEncoderType) safeString(seen map[typeId]bool) string {
+	return g.Name
+}
+
+func (g *gobEncoderType) string() string { return g.Name }
+
+// Map type
+type mapType struct {
+	CommonType
+	Key  typeId
+	Elem typeId
+}
+
+func newMapType(name string) *mapType {
+	m := &mapType{CommonType{Name: name}, 0, 0}
+	return m
+}
+
+func (m *mapType) init(key, elem gobType) {
+	// Set our type id before evaluating the element's, in case it's our own.
+	setTypeId(m)
+	m.Key = key.id()
+	m.Elem = elem.id()
+}
+
+func (m *mapType) safeString(seen map[typeId]bool) string {
+	if seen[m.Id] {
+		return m.Name
+	}
+	seen[m.Id] = true
+	key := m.Key.gobType().safeString(seen)
+	elem := m.Elem.gobType().safeString(seen)
+	return fmt.Sprintf("map[%s]%s", key, elem)
+}
+
+func (m *mapType) string() string { return m.safeString(make(map[typeId]bool)) }
+
+// Slice type
+type sliceType struct {
+	CommonType
+	Elem typeId
+}
+
+func newSliceType(name string) *sliceType {
+	s := &sliceType{CommonType{Name: name}, 0}
+	return s
+}
+
+func (s *sliceType) init(elem gobType) {
+	// Set our type id before evaluating the element's, in case it's our own.
+	setTypeId(s)
+	// See the comments about ids in newTypeObject. Only slices and
+	// structs have mutual recursion.
+	if elem.id() == 0 {
+		setTypeId(elem)
+	}
+	s.Elem = elem.id()
+}
+
+func (s *sliceType) safeString(seen map[typeId]bool) string {
+	if seen[s.Id] {
+		return s.Name
+	}
+	seen[s.Id] = true
+	return fmt.Sprintf("[]%s", s.Elem.gobType().safeString(seen))
+}
+
+func (s *sliceType) string() string { return s.safeString(make(map[typeId]bool)) }
+
+// Struct type
+type fieldType struct {
+	Name string
+	Id   typeId
+}
+
+type structType struct {
+	CommonType
+	Field []*fieldType
+}
+
+func (s *structType) safeString(seen map[typeId]bool) string {
+	if s == nil {
+		return "<nil>"
+	}
+	if _, ok := seen[s.Id]; ok {
+		return s.Name
+	}
+	seen[s.Id] = true
+	str := s.Name + " = struct { "
+	for _, f := range s.Field {
+		str += fmt.Sprintf("%s %s; ", f.Name, f.Id.gobType().safeString(seen))
+	}
+	str += "}"
+	return str
+}
+
+func (s *structType) string() string { return s.safeString(make(map[typeId]bool)) }
+
+func newStructType(name string) *structType {
+	s := &structType{CommonType{Name: name}, nil}
+	// For historical reasons we set the id here rather than init.
+	// See the comment in newTypeObject for details.
+	setTypeId(s)
+	return s
+}
+
+// newTypeObject allocates a gobType for the reflection type rt.
+// Unless ut represents a GobEncoder, rt should be the base type
+// of ut.
+// This is only called from the encoding side. The decoding side
+// works through typeIds and userTypeInfos alone.
+func newTypeObject(name string, ut *userTypeInfo, rt reflect.Type) (gobType, error) {
+	// Does this type implement GobEncoder?
+	if ut.externalEnc != 0 {
+		return newGobEncoderType(name), nil
+	}
+	var err error
+	var type0, type1 gobType
+	defer func() {
+		if err != nil {
+			delete(types, rt)
+		}
+	}()
+	// Install the top-level type before the subtypes (e.g. struct before
+	// fields) so recursive types can be constructed safely.
+	switch t := rt; t.Kind() {
+	// All basic types are easy: they are predefined.
+	case reflect.Bool:
+		return tBool.gobType(), nil
+
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return tInt.gobType(), nil
+
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		return tUint.gobType(), nil
+
+	case reflect.Float32, reflect.Float64:
+		return tFloat.gobType(), nil
+
+	case reflect.Complex64, reflect.Complex128:
+		return tComplex.gobType(), nil
+
+	case reflect.String:
+		return tString.gobType(), nil
+
+	case reflect.Interface:
+		return tInterface.gobType(), nil
+
+	case reflect.Array:
+		at := newArrayType(name)
+		types[rt] = at
+		type0, err = getBaseType("", t.Elem())
+		if err != nil {
+			return nil, err
+		}
+		// Historical aside:
+		// For arrays, maps, and slices, we set the type id after the elements
+		// are constructed. This is to retain the order of type id allocation after
+		// a fix made to handle recursive types, which changed the order in
+		// which types are built. Delaying the setting in this way preserves
+		// type ids while allowing recursive types to be described. Structs,
+		// done below, were already handling recursion correctly so they
+		// assign the top-level id before those of the field.
+		at.init(type0, t.Len())
+		return at, nil
+
+	case reflect.Map:
+		mt := newMapType(name)
+		types[rt] = mt
+		type0, err = getBaseType("", t.Key())
+		if err != nil {
+			return nil, err
+		}
+		type1, err = getBaseType("", t.Elem())
+		if err != nil {
+			return nil, err
+		}
+		mt.init(type0, type1)
+		return mt, nil
+
+	case reflect.Slice:
+		// []byte == []uint8 is a special case
+		if t.Elem().Kind() == reflect.Uint8 {
+			return tBytes.gobType(), nil
+		}
+		st := newSliceType(name)
+		types[rt] = st
+		type0, err = getBaseType(t.Elem().Name(), t.Elem())
+		if err != nil {
+			return nil, err
+		}
+		st.init(type0)
+		return st, nil
+
+	case reflect.Struct:
+		st := newStructType(name)
+		types[rt] = st
+		idToType[st.id()] = st
+		for i := 0; i < t.NumField(); i++ {
+			f := t.Field(i)
+			if !isSent(&f) {
+				continue
+			}
+			typ := userType(f.Type).base
+			tname := typ.Name()
+			if tname == "" {
+				t := userType(f.Type).base
+				tname = t.String()
+			}
+			gt, err := getBaseType(tname, f.Type)
+			if err != nil {
+				return nil, err
+			}
+			// Some mutually recursive types can cause us to be here while
+			// still defining the element. Fix the element type id here.
+			// We could do this more neatly by setting the id at the start of
+			// building every type, but that would break binary compatibility.
+			if gt.id() == 0 {
+				setTypeId(gt)
+			}
+			st.Field = append(st.Field, &fieldType{f.Name, gt.id()})
+		}
+		return st, nil
+
+	default:
+		return nil, errors.New("gob NewTypeObject can't handle type: " + rt.String())
+	}
+}
+
+// isExported reports whether this is an exported - upper case - name.
+func isExported(name string) bool {
+	rune, _ := utf8.DecodeRuneInString(name)
+	return unicode.IsUpper(rune)
+}
+
+// isSent reports whether this struct field is to be transmitted.
+// It will be transmitted only if it is exported and not a chan or func field
+// or pointer to chan or func.
+func isSent(field *reflect.StructField) bool {
+	if !isExported(field.Name) {
+		return false
+	}
+	// If the field is a chan or func or pointer thereto, don't send it.
+	// That is, treat it like an unexported field.
+	typ := field.Type
+	for typ.Kind() == reflect.Pointer {
+		typ = typ.Elem()
+	}
+	if typ.Kind() == reflect.Chan || typ.Kind() == reflect.Func {
+		return false
+	}
+	return true
+}
+
+// getBaseType returns the Gob type describing the given reflect.Type's base type.
+// typeLock must be held.
+func getBaseType(name string, rt reflect.Type) (gobType, error) {
+	ut := userType(rt)
+	return getType(name, ut, ut.base)
+}
+
+// getType returns the Gob type describing the given reflect.Type.
+// Should be called only when handling GobEncoders/Decoders,
+// which may be pointers. All other types are handled through the
+// base type, never a pointer.
+// typeLock must be held.
+func getType(name string, ut *userTypeInfo, rt reflect.Type) (gobType, error) {
+	typ, present := types[rt]
+	if present {
+		return typ, nil
+	}
+	typ, err := newTypeObject(name, ut, rt)
+	if err == nil {
+		types[rt] = typ
+	}
+	return typ, err
+}
+
+func checkId(want, got typeId) {
+	if want != got {
+		fmt.Fprintf(os.Stderr, "checkId: %d should be %d\n", int(got), int(want))
+		panic("bootstrap type wrong id: " + got.name() + " " + got.string() + " not " + want.string())
+	}
+}
+
+// used for building the basic types; called only from init().  the incoming
+// interface always refers to a pointer.
+func bootstrapType(name string, e any, expect typeId) typeId {
+	rt := reflect.TypeOf(e).Elem()
+	_, present := types[rt]
+	if present {
+		panic("bootstrap type already present: " + name + ", " + rt.String())
+	}
+	typ := &CommonType{Name: name}
+	types[rt] = typ
+	setTypeId(typ)
+	checkId(expect, nextId)
+	userType(rt) // might as well cache it now
+	return nextId
+}
+
+// Representation of the information we send and receive about this type.
+// Each value we send is preceded by its type definition: an encoded int.
+// However, the very first time we send the value, we first send the pair
+// (-id, wireType).
+// For bootstrapping purposes, we assume that the recipient knows how
+// to decode a wireType; it is exactly the wireType struct here, interpreted
+// using the gob rules for sending a structure, except that we assume the
+// ids for wireType and structType etc. are known. The relevant pieces
+// are built in encode.go's init() function.
+// To maintain binary compatibility, if you extend this type, always put
+// the new fields last.
+type wireType struct {
+	ArrayT           *arrayType
+	SliceT           *sliceType
+	StructT          *structType
+	MapT             *mapType
+	GobEncoderT      *gobEncoderType
+	BinaryMarshalerT *gobEncoderType
+	TextMarshalerT   *gobEncoderType
+}
+
+func (w *wireType) string() string {
+	const unknown = "unknown type"
+	if w == nil {
+		return unknown
+	}
+	switch {
+	case w.ArrayT != nil:
+		return w.ArrayT.Name
+	case w.SliceT != nil:
+		return w.SliceT.Name
+	case w.StructT != nil:
+		return w.StructT.Name
+	case w.MapT != nil:
+		return w.MapT.Name
+	case w.GobEncoderT != nil:
+		return w.GobEncoderT.Name
+	case w.BinaryMarshalerT != nil:
+		return w.BinaryMarshalerT.Name
+	case w.TextMarshalerT != nil:
+		return w.TextMarshalerT.Name
+	}
+	return unknown
+}
+
+type typeInfo struct {
+	id      typeId
+	encInit sync.Mutex   // protects creation of encoder
+	encoder atomic.Value // *encEngine
+	wire    *wireType
+}
+
+// typeInfoMap is an atomic pointer to map[reflect.Type]*typeInfo.
+// It's updated copy-on-write. Readers just do an atomic load
+// to get the current version of the map. Writers make a full copy of
+// the map and atomically update the pointer to point to the new map.
+// Under heavy read contention, this is significantly faster than a map
+// protected by a mutex.
+var typeInfoMap atomic.Value
+
+func lookupTypeInfo(rt reflect.Type) *typeInfo {
+	m, _ := typeInfoMap.Load().(map[reflect.Type]*typeInfo)
+	return m[rt]
+}
+
+func getTypeInfo(ut *userTypeInfo) (*typeInfo, error) {
+	rt := ut.base
+	if ut.externalEnc != 0 {
+		// We want the user type, not the base type.
+		rt = ut.user
+	}
+	if info := lookupTypeInfo(rt); info != nil {
+		return info, nil
+	}
+	return buildTypeInfo(ut, rt)
+}
+
+// buildTypeInfo constructs the type information for the type
+// and stores it in the type info map.
+func buildTypeInfo(ut *userTypeInfo, rt reflect.Type) (*typeInfo, error) {
+	typeLock.Lock()
+	defer typeLock.Unlock()
+
+	if info := lookupTypeInfo(rt); info != nil {
+		return info, nil
+	}
+
+	gt, err := getBaseType(rt.Name(), rt)
+	if err != nil {
+		return nil, err
+	}
+	info := &typeInfo{id: gt.id()}
+
+	if ut.externalEnc != 0 {
+		userType, err := getType(rt.Name(), ut, rt)
+		if err != nil {
+			return nil, err
+		}
+		gt := userType.id().gobType().(*gobEncoderType)
+		switch ut.externalEnc {
+		case xGob:
+			info.wire = &wireType{GobEncoderT: gt}
+		case xBinary:
+			info.wire = &wireType{BinaryMarshalerT: gt}
+		case xText:
+			info.wire = &wireType{TextMarshalerT: gt}
+		}
+		rt = ut.user
+	} else {
+		t := info.id.gobType()
+		switch typ := rt; typ.Kind() {
+		case reflect.Array:
+			info.wire = &wireType{ArrayT: t.(*arrayType)}
+		case reflect.Map:
+			info.wire = &wireType{MapT: t.(*mapType)}
+		case reflect.Slice:
+			// []byte == []uint8 is a special case handled separately
+			if typ.Elem().Kind() != reflect.Uint8 {
+				info.wire = &wireType{SliceT: t.(*sliceType)}
+			}
+		case reflect.Struct:
+			info.wire = &wireType{StructT: t.(*structType)}
+		}
+	}
+
+	// Create new map with old contents plus new entry.
+	newm := make(map[reflect.Type]*typeInfo)
+	m, _ := typeInfoMap.Load().(map[reflect.Type]*typeInfo)
+	for k, v := range m {
+		newm[k] = v
+	}
+	newm[rt] = info
+	typeInfoMap.Store(newm)
+	return info, nil
+}
+
+// Called only when a panic is acceptable and unexpected.
+func mustGetTypeInfo(rt reflect.Type) *typeInfo {
+	t, err := getTypeInfo(userType(rt))
+	if err != nil {
+		panic("getTypeInfo: " + err.Error())
+	}
+	return t
+}
+
+// GobEncoder is the interface describing data that provides its own
+// representation for encoding values for transmission to a GobDecoder.
+// A type that implements GobEncoder and GobDecoder has complete
+// control over the representation of its data and may therefore
+// contain things such as private fields, channels, and functions,
+// which are not usually transmissible in gob streams.
+//
+// Note: Since gobs can be stored permanently, it is good design
+// to guarantee the encoding used by a GobEncoder is stable as the
+// software evolves. For instance, it might make sense for GobEncode
+// to include a version number in the encoding.
+type GobEncoder interface {
+	// GobEncode returns a byte slice representing the encoding of the
+	// receiver for transmission to a GobDecoder, usually of the same
+	// concrete type.
+	GobEncode() ([]byte, error)
+}
+
+// GobDecoder is the interface describing data that provides its own
+// routine for decoding transmitted values sent by a GobEncoder.
+type GobDecoder interface {
+	// GobDecode overwrites the receiver, which must be a pointer,
+	// with the value represented by the byte slice, which was written
+	// by GobEncode, usually for the same concrete type.
+	GobDecode([]byte) error
+}
+
+var (
+	nameToConcreteType sync.Map // map[string]reflect.Type
+	concreteTypeToName sync.Map // map[reflect.Type]string
+)
+
+// RegisterName is like Register but uses the provided name rather than the
+// type's default.
+func RegisterName(name string, value any) {
+	if name == "" {
+		// reserved for nil
+		panic("attempt to register empty name")
+	}
+
+	ut := userType(reflect.TypeOf(value))
+
+	// Check for incompatible duplicates. The name must refer to the
+	// same user type, and vice versa.
+
+	// Store the name and type provided by the user....
+	if t, dup := nameToConcreteType.LoadOrStore(name, reflect.TypeOf(value)); dup && t != ut.user {
+		panic(fmt.Sprintf("gob: registering duplicate types for %q: %s != %s", name, t, ut.user))
+	}
+
+	// but the flattened type in the type table, since that's what decode needs.
+	if n, dup := concreteTypeToName.LoadOrStore(ut.base, name); dup && n != name {
+		nameToConcreteType.Delete(name)
+		panic(fmt.Sprintf("gob: registering duplicate names for %s: %q != %q", ut.user, n, name))
+	}
+}
+
+// Register records a type, identified by a value for that type, under its
+// internal type name. That name will identify the concrete type of a value
+// sent or received as an interface variable. Only types that will be
+// transferred as implementations of interface values need to be registered.
+// Expecting to be used only during initialization, it panics if the mapping
+// between types and names is not a bijection.
+func Register(value any) {
+	// Default to printed representation for unnamed types
+	rt := reflect.TypeOf(value)
+	name := rt.String()
+
+	// But for named types (or pointers to them), qualify with import path (but see inner comment).
+	// Dereference one pointer looking for a named type.
+	star := ""
+	if rt.Name() == "" {
+		if pt := rt; pt.Kind() == reflect.Pointer {
+			star = "*"
+			// NOTE: The following line should be rt = pt.Elem() to implement
+			// what the comment above claims, but fixing it would break compatibility
+			// with existing gobs.
+			//
+			// Given package p imported as "full/p" with these definitions:
+			//     package p
+			//     type T1 struct { ... }
+			// this table shows the intended and actual strings used by gob to
+			// name the types:
+			//
+			// Type      Correct string     Actual string
+			//
+			// T1        full/p.T1          full/p.T1
+			// *T1       *full/p.T1         *p.T1
+			//
+			// The missing full path cannot be fixed without breaking existing gob decoders.
+			rt = pt
+		}
+	}
+	if rt.Name() != "" {
+		if rt.PkgPath() == "" {
+			name = star + rt.Name()
+		} else {
+			name = star + rt.PkgPath() + "." + rt.Name()
+		}
+	}
+
+	RegisterName(name, value)
+}
+
+func registerBasics() {
+	Register(int(0))
+	Register(int8(0))
+	Register(int16(0))
+	Register(int32(0))
+	Register(int64(0))
+	Register(uint(0))
+	Register(uint8(0))
+	Register(uint16(0))
+	Register(uint32(0))
+	Register(uint64(0))
+	Register(float32(0))
+	Register(float64(0))
+	Register(complex64(0i))
+	Register(complex128(0i))
+	Register(uintptr(0))
+	Register(false)
+	Register("")
+	Register([]byte(nil))
+	Register([]int(nil))
+	Register([]int8(nil))
+	Register([]int16(nil))
+	Register([]int32(nil))
+	Register([]int64(nil))
+	Register([]uint(nil))
+	Register([]uint8(nil))
+	Register([]uint16(nil))
+	Register([]uint32(nil))
+	Register([]uint64(nil))
+	Register([]float32(nil))
+	Register([]float64(nil))
+	Register([]complex64(nil))
+	Register([]complex128(nil))
+	Register([]uintptr(nil))
+	Register([]bool(nil))
+	Register([]string(nil))
+}
diff --git a/src/encoding/gob/type_test.go b/src/encoding/gob/type_test.go
new file mode 100644
index 0000000..f5f8db8
--- /dev/null
+++ b/src/encoding/gob/type_test.go
@@ -0,0 +1,262 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package gob
+
+import (
+	"bytes"
+	"reflect"
+	"sync"
+	"testing"
+)
+
+type typeT struct {
+	id  typeId
+	str string
+}
+
+var basicTypes = []typeT{
+	{tBool, "bool"},
+	{tInt, "int"},
+	{tUint, "uint"},
+	{tFloat, "float"},
+	{tBytes, "bytes"},
+	{tString, "string"},
+}
+
+func getTypeUnlocked(name string, rt reflect.Type) gobType {
+	typeLock.Lock()
+	defer typeLock.Unlock()
+	t, err := getBaseType(name, rt)
+	if err != nil {
+		panic("getTypeUnlocked: " + err.Error())
+	}
+	return t
+}
+
+// Sanity checks
+func TestBasic(t *testing.T) {
+	for _, tt := range basicTypes {
+		if tt.id.string() != tt.str {
+			t.Errorf("checkType: expected %q got %s", tt.str, tt.id.string())
+		}
+		if tt.id == 0 {
+			t.Errorf("id for %q is zero", tt.str)
+		}
+	}
+}
+
+// Reregister some basic types to check registration is idempotent.
+func TestReregistration(t *testing.T) {
+	newtyp := getTypeUnlocked("int", reflect.TypeOf(int(0)))
+	if newtyp != tInt.gobType() {
+		t.Errorf("reregistration of %s got new type", newtyp.string())
+	}
+	newtyp = getTypeUnlocked("uint", reflect.TypeOf(uint(0)))
+	if newtyp != tUint.gobType() {
+		t.Errorf("reregistration of %s got new type", newtyp.string())
+	}
+	newtyp = getTypeUnlocked("string", reflect.TypeOf("hello"))
+	if newtyp != tString.gobType() {
+		t.Errorf("reregistration of %s got new type", newtyp.string())
+	}
+}
+
+func TestArrayType(t *testing.T) {
+	var a3 [3]int
+	a3int := getTypeUnlocked("foo", reflect.TypeOf(a3))
+	newa3int := getTypeUnlocked("bar", reflect.TypeOf(a3))
+	if a3int != newa3int {
+		t.Errorf("second registration of [3]int creates new type")
+	}
+	var a4 [4]int
+	a4int := getTypeUnlocked("goo", reflect.TypeOf(a4))
+	if a3int == a4int {
+		t.Errorf("registration of [3]int creates same type as [4]int")
+	}
+	var b3 [3]bool
+	a3bool := getTypeUnlocked("", reflect.TypeOf(b3))
+	if a3int == a3bool {
+		t.Errorf("registration of [3]bool creates same type as [3]int")
+	}
+	str := a3bool.string()
+	expected := "[3]bool"
+	if str != expected {
+		t.Errorf("array printed as %q; expected %q", str, expected)
+	}
+}
+
+func TestSliceType(t *testing.T) {
+	var s []int
+	sint := getTypeUnlocked("slice", reflect.TypeOf(s))
+	var news []int
+	newsint := getTypeUnlocked("slice1", reflect.TypeOf(news))
+	if sint != newsint {
+		t.Errorf("second registration of []int creates new type")
+	}
+	var b []bool
+	sbool := getTypeUnlocked("", reflect.TypeOf(b))
+	if sbool == sint {
+		t.Errorf("registration of []bool creates same type as []int")
+	}
+	str := sbool.string()
+	expected := "[]bool"
+	if str != expected {
+		t.Errorf("slice printed as %q; expected %q", str, expected)
+	}
+}
+
+func TestMapType(t *testing.T) {
+	var m map[string]int
+	mapStringInt := getTypeUnlocked("map", reflect.TypeOf(m))
+	var newm map[string]int
+	newMapStringInt := getTypeUnlocked("map1", reflect.TypeOf(newm))
+	if mapStringInt != newMapStringInt {
+		t.Errorf("second registration of map[string]int creates new type")
+	}
+	var b map[string]bool
+	mapStringBool := getTypeUnlocked("", reflect.TypeOf(b))
+	if mapStringBool == mapStringInt {
+		t.Errorf("registration of map[string]bool creates same type as map[string]int")
+	}
+	str := mapStringBool.string()
+	expected := "map[string]bool"
+	if str != expected {
+		t.Errorf("map printed as %q; expected %q", str, expected)
+	}
+}
+
+type Bar struct {
+	X string
+}
+
+// This structure has pointers and refers to itself, making it a good test case.
+type Foo struct {
+	A int
+	B int32 // will become int
+	C string
+	D []byte
+	E *float64    // will become float64
+	F ****float64 // will become float64
+	G *Bar
+	H *Bar // should not interpolate the definition of Bar again
+	I *Foo // will not explode
+}
+
+func TestStructType(t *testing.T) {
+	sstruct := getTypeUnlocked("Foo", reflect.TypeOf(Foo{}))
+	str := sstruct.string()
+	// If we can print it correctly, we built it correctly.
+	expected := "Foo = struct { A int; B int; C string; D bytes; E float; F float; G Bar = struct { X string; }; H Bar; I Foo; }"
+	if str != expected {
+		t.Errorf("struct printed as %q; expected %q", str, expected)
+	}
+}
+
+// Should be OK to register the same type multiple times, as long as they're
+// at the same level of indirection.
+func TestRegistration(t *testing.T) {
+	type T struct{ a int }
+	Register(new(T))
+	Register(new(T))
+}
+
+type N1 struct{}
+type N2 struct{}
+
+// See comment in type.go/Register.
+func TestRegistrationNaming(t *testing.T) {
+	testCases := []struct {
+		t    any
+		name string
+	}{
+		{&N1{}, "*gob.N1"},
+		{N2{}, "encoding/gob.N2"},
+	}
+
+	for _, tc := range testCases {
+		Register(tc.t)
+
+		tct := reflect.TypeOf(tc.t)
+		ct, _ := nameToConcreteType.Load(tc.name)
+		if ct != tct {
+			t.Errorf("nameToConcreteType[%q] = %v, want %v", tc.name, ct, tct)
+		}
+		// concreteTypeToName is keyed off the base type.
+		if tct.Kind() == reflect.Pointer {
+			tct = tct.Elem()
+		}
+		if n, _ := concreteTypeToName.Load(tct); n != tc.name {
+			t.Errorf("concreteTypeToName[%v] got %v, want %v", tct, n, tc.name)
+		}
+	}
+}
+
+func TestStressParallel(t *testing.T) {
+	type T2 struct{ A int }
+	c := make(chan bool)
+	const N = 10
+	for i := 0; i < N; i++ {
+		go func() {
+			p := new(T2)
+			Register(p)
+			b := new(bytes.Buffer)
+			enc := NewEncoder(b)
+			err := enc.Encode(p)
+			if err != nil {
+				t.Error("encoder fail:", err)
+			}
+			dec := NewDecoder(b)
+			err = dec.Decode(p)
+			if err != nil {
+				t.Error("decoder fail:", err)
+			}
+			c <- true
+		}()
+	}
+	for i := 0; i < N; i++ {
+		<-c
+	}
+}
+
+// Issue 23328. Note that this test name is known to cmd/dist/test.go.
+func TestTypeRace(t *testing.T) {
+	c := make(chan bool)
+	var wg sync.WaitGroup
+	for i := 0; i < 2; i++ {
+		wg.Add(1)
+		go func(i int) {
+			defer wg.Done()
+			var buf bytes.Buffer
+			enc := NewEncoder(&buf)
+			dec := NewDecoder(&buf)
+			var x any
+			switch i {
+			case 0:
+				x = &N1{}
+			case 1:
+				x = &N2{}
+			default:
+				t.Errorf("bad i %d", i)
+				return
+			}
+			m := make(map[string]string)
+			<-c
+			if err := enc.Encode(x); err != nil {
+				t.Error(err)
+				return
+			}
+			if err := enc.Encode(x); err != nil {
+				t.Error(err)
+				return
+			}
+			if err := dec.Decode(&m); err == nil {
+				t.Error("decode unexpectedly succeeded")
+				return
+			}
+		}(i)
+	}
+	close(c)
+	wg.Wait()
+}
diff --git a/src/encoding/hex/example_test.go b/src/encoding/hex/example_test.go
new file mode 100644
index 0000000..3580757
--- /dev/null
+++ b/src/encoding/hex/example_test.go
@@ -0,0 +1,98 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package hex_test
+
+import (
+	"encoding/hex"
+	"fmt"
+	"log"
+	"os"
+)
+
+func ExampleEncode() {
+	src := []byte("Hello Gopher!")
+
+	dst := make([]byte, hex.EncodedLen(len(src)))
+	hex.Encode(dst, src)
+
+	fmt.Printf("%s\n", dst)
+
+	// Output:
+	// 48656c6c6f20476f7068657221
+}
+
+func ExampleDecode() {
+	src := []byte("48656c6c6f20476f7068657221")
+
+	dst := make([]byte, hex.DecodedLen(len(src)))
+	n, err := hex.Decode(dst, src)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	fmt.Printf("%s\n", dst[:n])
+
+	// Output:
+	// Hello Gopher!
+}
+
+func ExampleDecodeString() {
+	const s = "48656c6c6f20476f7068657221"
+	decoded, err := hex.DecodeString(s)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	fmt.Printf("%s\n", decoded)
+
+	// Output:
+	// Hello Gopher!
+}
+
+func ExampleDump() {
+	content := []byte("Go is an open source programming language.")
+
+	fmt.Printf("%s", hex.Dump(content))
+
+	// Output:
+	// 00000000  47 6f 20 69 73 20 61 6e  20 6f 70 65 6e 20 73 6f  |Go is an open so|
+	// 00000010  75 72 63 65 20 70 72 6f  67 72 61 6d 6d 69 6e 67  |urce programming|
+	// 00000020  20 6c 61 6e 67 75 61 67  65 2e                    | language.|
+}
+
+func ExampleDumper() {
+	lines := []string{
+		"Go is an open source programming language.",
+		"\n",
+		"We encourage all Go users to subscribe to golang-announce.",
+	}
+
+	stdoutDumper := hex.Dumper(os.Stdout)
+
+	defer stdoutDumper.Close()
+
+	for _, line := range lines {
+		stdoutDumper.Write([]byte(line))
+	}
+
+	// Output:
+	// 00000000  47 6f 20 69 73 20 61 6e  20 6f 70 65 6e 20 73 6f  |Go is an open so|
+	// 00000010  75 72 63 65 20 70 72 6f  67 72 61 6d 6d 69 6e 67  |urce programming|
+	// 00000020  20 6c 61 6e 67 75 61 67  65 2e 0a 57 65 20 65 6e  | language..We en|
+	// 00000030  63 6f 75 72 61 67 65 20  61 6c 6c 20 47 6f 20 75  |courage all Go u|
+	// 00000040  73 65 72 73 20 74 6f 20  73 75 62 73 63 72 69 62  |sers to subscrib|
+	// 00000050  65 20 74 6f 20 67 6f 6c  61 6e 67 2d 61 6e 6e 6f  |e to golang-anno|
+	// 00000060  75 6e 63 65 2e                                    |unce.|
+}
+
+func ExampleEncodeToString() {
+	src := []byte("Hello")
+	encodedStr := hex.EncodeToString(src)
+
+	fmt.Printf("%s\n", encodedStr)
+
+	// Output:
+	// 48656c6c6f
+}
diff --git a/src/encoding/hex/hex.go b/src/encoding/hex/hex.go
new file mode 100644
index 0000000..fbba78f
--- /dev/null
+++ b/src/encoding/hex/hex.go
@@ -0,0 +1,326 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package hex implements hexadecimal encoding and decoding.
+package hex
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"strings"
+)
+
+const hextable = "0123456789abcdef"
+
+// EncodedLen returns the length of an encoding of n source bytes.
+// Specifically, it returns n * 2.
+func EncodedLen(n int) int { return n * 2 }
+
+// Encode encodes src into EncodedLen(len(src))
+// bytes of dst. As a convenience, it returns the number
+// of bytes written to dst, but this value is always EncodedLen(len(src)).
+// Encode implements hexadecimal encoding.
+func Encode(dst, src []byte) int {
+	j := 0
+	for _, v := range src {
+		dst[j] = hextable[v>>4]
+		dst[j+1] = hextable[v&0x0f]
+		j += 2
+	}
+	return len(src) * 2
+}
+
+// ErrLength reports an attempt to decode an odd-length input
+// using Decode or DecodeString.
+// The stream-based Decoder returns io.ErrUnexpectedEOF instead of ErrLength.
+var ErrLength = errors.New("encoding/hex: odd length hex string")
+
+// InvalidByteError values describe errors resulting from an invalid byte in a hex string.
+type InvalidByteError byte
+
+func (e InvalidByteError) Error() string {
+	return fmt.Sprintf("encoding/hex: invalid byte: %#U", rune(e))
+}
+
+// DecodedLen returns the length of a decoding of x source bytes.
+// Specifically, it returns x / 2.
+func DecodedLen(x int) int { return x / 2 }
+
+// Decode decodes src into DecodedLen(len(src)) bytes,
+// returning the actual number of bytes written to dst.
+//
+// Decode expects that src contains only hexadecimal
+// characters and that src has even length.
+// If the input is malformed, Decode returns the number
+// of bytes decoded before the error.
+func Decode(dst, src []byte) (int, error) {
+	i, j := 0, 1
+	for ; j < len(src); j += 2 {
+		a, ok := fromHexChar(src[j-1])
+		if !ok {
+			return i, InvalidByteError(src[j-1])
+		}
+		b, ok := fromHexChar(src[j])
+		if !ok {
+			return i, InvalidByteError(src[j])
+		}
+		dst[i] = (a << 4) | b
+		i++
+	}
+	if len(src)%2 == 1 {
+		// Check for invalid char before reporting bad length,
+		// since the invalid char (if present) is an earlier problem.
+		if _, ok := fromHexChar(src[j-1]); !ok {
+			return i, InvalidByteError(src[j-1])
+		}
+		return i, ErrLength
+	}
+	return i, nil
+}
+
+// fromHexChar converts a hex character into its value and a success flag.
+func fromHexChar(c byte) (byte, bool) {
+	switch {
+	case '0' <= c && c <= '9':
+		return c - '0', true
+	case 'a' <= c && c <= 'f':
+		return c - 'a' + 10, true
+	case 'A' <= c && c <= 'F':
+		return c - 'A' + 10, true
+	}
+
+	return 0, false
+}
+
+// EncodeToString returns the hexadecimal encoding of src.
+func EncodeToString(src []byte) string {
+	dst := make([]byte, EncodedLen(len(src)))
+	Encode(dst, src)
+	return string(dst)
+}
+
+// DecodeString returns the bytes represented by the hexadecimal string s.
+//
+// DecodeString expects that src contains only hexadecimal
+// characters and that src has even length.
+// If the input is malformed, DecodeString returns
+// the bytes decoded before the error.
+func DecodeString(s string) ([]byte, error) {
+	src := []byte(s)
+	// We can use the source slice itself as the destination
+	// because the decode loop increments by one and then the 'seen' byte is not used anymore.
+	n, err := Decode(src, src)
+	return src[:n], err
+}
+
+// Dump returns a string that contains a hex dump of the given data. The format
+// of the hex dump matches the output of `hexdump -C` on the command line.
+func Dump(data []byte) string {
+	if len(data) == 0 {
+		return ""
+	}
+
+	var buf strings.Builder
+	// Dumper will write 79 bytes per complete 16 byte chunk, and at least
+	// 64 bytes for whatever remains. Round the allocation up, since only a
+	// maximum of 15 bytes will be wasted.
+	buf.Grow((1 + ((len(data) - 1) / 16)) * 79)
+
+	dumper := Dumper(&buf)
+	dumper.Write(data)
+	dumper.Close()
+	return buf.String()
+}
+
+// bufferSize is the number of hexadecimal characters to buffer in encoder and decoder.
+const bufferSize = 1024
+
+type encoder struct {
+	w   io.Writer
+	err error
+	out [bufferSize]byte // output buffer
+}
+
+// NewEncoder returns an io.Writer that writes lowercase hexadecimal characters to w.
+func NewEncoder(w io.Writer) io.Writer {
+	return &encoder{w: w}
+}
+
+func (e *encoder) Write(p []byte) (n int, err error) {
+	for len(p) > 0 && e.err == nil {
+		chunkSize := bufferSize / 2
+		if len(p) < chunkSize {
+			chunkSize = len(p)
+		}
+
+		var written int
+		encoded := Encode(e.out[:], p[:chunkSize])
+		written, e.err = e.w.Write(e.out[:encoded])
+		n += written / 2
+		p = p[chunkSize:]
+	}
+	return n, e.err
+}
+
+type decoder struct {
+	r   io.Reader
+	err error
+	in  []byte           // input buffer (encoded form)
+	arr [bufferSize]byte // backing array for in
+}
+
+// NewDecoder returns an io.Reader that decodes hexadecimal characters from r.
+// NewDecoder expects that r contain only an even number of hexadecimal characters.
+func NewDecoder(r io.Reader) io.Reader {
+	return &decoder{r: r}
+}
+
+func (d *decoder) Read(p []byte) (n int, err error) {
+	// Fill internal buffer with sufficient bytes to decode
+	if len(d.in) < 2 && d.err == nil {
+		var numCopy, numRead int
+		numCopy = copy(d.arr[:], d.in) // Copies either 0 or 1 bytes
+		numRead, d.err = d.r.Read(d.arr[numCopy:])
+		d.in = d.arr[:numCopy+numRead]
+		if d.err == io.EOF && len(d.in)%2 != 0 {
+			if _, ok := fromHexChar(d.in[len(d.in)-1]); !ok {
+				d.err = InvalidByteError(d.in[len(d.in)-1])
+			} else {
+				d.err = io.ErrUnexpectedEOF
+			}
+		}
+	}
+
+	// Decode internal buffer into output buffer
+	if numAvail := len(d.in) / 2; len(p) > numAvail {
+		p = p[:numAvail]
+	}
+	numDec, err := Decode(p, d.in[:len(p)*2])
+	d.in = d.in[2*numDec:]
+	if err != nil {
+		d.in, d.err = nil, err // Decode error; discard input remainder
+	}
+
+	if len(d.in) < 2 {
+		return numDec, d.err // Only expose errors when buffer fully consumed
+	}
+	return numDec, nil
+}
+
+// Dumper returns a WriteCloser that writes a hex dump of all written data to
+// w. The format of the dump matches the output of `hexdump -C` on the command
+// line.
+func Dumper(w io.Writer) io.WriteCloser {
+	return &dumper{w: w}
+}
+
+type dumper struct {
+	w          io.Writer
+	rightChars [18]byte
+	buf        [14]byte
+	used       int  // number of bytes in the current line
+	n          uint // number of bytes, total
+	closed     bool
+}
+
+func toChar(b byte) byte {
+	if b < 32 || b > 126 {
+		return '.'
+	}
+	return b
+}
+
+func (h *dumper) Write(data []byte) (n int, err error) {
+	if h.closed {
+		return 0, errors.New("encoding/hex: dumper closed")
+	}
+
+	// Output lines look like:
+	// 00000010  2e 2f 30 31 32 33 34 35  36 37 38 39 3a 3b 3c 3d  |./0123456789:;<=|
+	// ^ offset                          ^ extra space              ^ ASCII of line.
+	for i := range data {
+		if h.used == 0 {
+			// At the beginning of a line we print the current
+			// offset in hex.
+			h.buf[0] = byte(h.n >> 24)
+			h.buf[1] = byte(h.n >> 16)
+			h.buf[2] = byte(h.n >> 8)
+			h.buf[3] = byte(h.n)
+			Encode(h.buf[4:], h.buf[:4])
+			h.buf[12] = ' '
+			h.buf[13] = ' '
+			_, err = h.w.Write(h.buf[4:])
+			if err != nil {
+				return
+			}
+		}
+		Encode(h.buf[:], data[i:i+1])
+		h.buf[2] = ' '
+		l := 3
+		if h.used == 7 {
+			// There's an additional space after the 8th byte.
+			h.buf[3] = ' '
+			l = 4
+		} else if h.used == 15 {
+			// At the end of the line there's an extra space and
+			// the bar for the right column.
+			h.buf[3] = ' '
+			h.buf[4] = '|'
+			l = 5
+		}
+		_, err = h.w.Write(h.buf[:l])
+		if err != nil {
+			return
+		}
+		n++
+		h.rightChars[h.used] = toChar(data[i])
+		h.used++
+		h.n++
+		if h.used == 16 {
+			h.rightChars[16] = '|'
+			h.rightChars[17] = '\n'
+			_, err = h.w.Write(h.rightChars[:])
+			if err != nil {
+				return
+			}
+			h.used = 0
+		}
+	}
+	return
+}
+
+func (h *dumper) Close() (err error) {
+	// See the comments in Write() for the details of this format.
+	if h.closed {
+		return
+	}
+	h.closed = true
+	if h.used == 0 {
+		return
+	}
+	h.buf[0] = ' '
+	h.buf[1] = ' '
+	h.buf[2] = ' '
+	h.buf[3] = ' '
+	h.buf[4] = '|'
+	nBytes := h.used
+	for h.used < 16 {
+		l := 3
+		if h.used == 7 {
+			l = 4
+		} else if h.used == 15 {
+			l = 5
+		}
+		_, err = h.w.Write(h.buf[:l])
+		if err != nil {
+			return
+		}
+		h.used++
+	}
+	h.rightChars[nBytes] = '|'
+	h.rightChars[nBytes+1] = '\n'
+	_, err = h.w.Write(h.rightChars[:nBytes+2])
+	return
+}
diff --git a/src/encoding/hex/hex_test.go b/src/encoding/hex/hex_test.go
new file mode 100644
index 0000000..7593e20
--- /dev/null
+++ b/src/encoding/hex/hex_test.go
@@ -0,0 +1,277 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package hex
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"strings"
+	"testing"
+)
+
+type encDecTest struct {
+	enc string
+	dec []byte
+}
+
+var encDecTests = []encDecTest{
+	{"", []byte{}},
+	{"0001020304050607", []byte{0, 1, 2, 3, 4, 5, 6, 7}},
+	{"08090a0b0c0d0e0f", []byte{8, 9, 10, 11, 12, 13, 14, 15}},
+	{"f0f1f2f3f4f5f6f7", []byte{0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7}},
+	{"f8f9fafbfcfdfeff", []byte{0xf8, 0xf9, 0xfa, 0xfb, 0xfc, 0xfd, 0xfe, 0xff}},
+	{"67", []byte{'g'}},
+	{"e3a1", []byte{0xe3, 0xa1}},
+}
+
+func TestEncode(t *testing.T) {
+	for i, test := range encDecTests {
+		dst := make([]byte, EncodedLen(len(test.dec)))
+		n := Encode(dst, test.dec)
+		if n != len(dst) {
+			t.Errorf("#%d: bad return value: got: %d want: %d", i, n, len(dst))
+		}
+		if string(dst) != test.enc {
+			t.Errorf("#%d: got: %#v want: %#v", i, dst, test.enc)
+		}
+	}
+}
+
+func TestDecode(t *testing.T) {
+	// Case for decoding uppercase hex characters, since
+	// Encode always uses lowercase.
+	decTests := append(encDecTests, encDecTest{"F8F9FAFBFCFDFEFF", []byte{0xf8, 0xf9, 0xfa, 0xfb, 0xfc, 0xfd, 0xfe, 0xff}})
+	for i, test := range decTests {
+		dst := make([]byte, DecodedLen(len(test.enc)))
+		n, err := Decode(dst, []byte(test.enc))
+		if err != nil {
+			t.Errorf("#%d: bad return value: got:%d want:%d", i, n, len(dst))
+		} else if !bytes.Equal(dst, test.dec) {
+			t.Errorf("#%d: got: %#v want: %#v", i, dst, test.dec)
+		}
+	}
+}
+
+func TestEncodeToString(t *testing.T) {
+	for i, test := range encDecTests {
+		s := EncodeToString(test.dec)
+		if s != test.enc {
+			t.Errorf("#%d got:%s want:%s", i, s, test.enc)
+		}
+	}
+}
+
+func TestDecodeString(t *testing.T) {
+	for i, test := range encDecTests {
+		dst, err := DecodeString(test.enc)
+		if err != nil {
+			t.Errorf("#%d: unexpected err value: %s", i, err)
+			continue
+		}
+		if !bytes.Equal(dst, test.dec) {
+			t.Errorf("#%d: got: %#v want: #%v", i, dst, test.dec)
+		}
+	}
+}
+
+var errTests = []struct {
+	in  string
+	out string
+	err error
+}{
+	{"", "", nil},
+	{"0", "", ErrLength},
+	{"zd4aa", "", InvalidByteError('z')},
+	{"d4aaz", "\xd4\xaa", InvalidByteError('z')},
+	{"30313", "01", ErrLength},
+	{"0g", "", InvalidByteError('g')},
+	{"00gg", "\x00", InvalidByteError('g')},
+	{"0\x01", "", InvalidByteError('\x01')},
+	{"ffeed", "\xff\xee", ErrLength},
+}
+
+func TestDecodeErr(t *testing.T) {
+	for _, tt := range errTests {
+		out := make([]byte, len(tt.in)+10)
+		n, err := Decode(out, []byte(tt.in))
+		if string(out[:n]) != tt.out || err != tt.err {
+			t.Errorf("Decode(%q) = %q, %v, want %q, %v", tt.in, string(out[:n]), err, tt.out, tt.err)
+		}
+	}
+}
+
+func TestDecodeStringErr(t *testing.T) {
+	for _, tt := range errTests {
+		out, err := DecodeString(tt.in)
+		if string(out) != tt.out || err != tt.err {
+			t.Errorf("DecodeString(%q) = %q, %v, want %q, %v", tt.in, out, err, tt.out, tt.err)
+		}
+	}
+}
+
+func TestEncoderDecoder(t *testing.T) {
+	for _, multiplier := range []int{1, 128, 192} {
+		for _, test := range encDecTests {
+			input := bytes.Repeat(test.dec, multiplier)
+			output := strings.Repeat(test.enc, multiplier)
+
+			var buf bytes.Buffer
+			enc := NewEncoder(&buf)
+			r := struct{ io.Reader }{bytes.NewReader(input)} // io.Reader only; not io.WriterTo
+			if n, err := io.CopyBuffer(enc, r, make([]byte, 7)); n != int64(len(input)) || err != nil {
+				t.Errorf("encoder.Write(%q*%d) = (%d, %v), want (%d, nil)", test.dec, multiplier, n, err, len(input))
+				continue
+			}
+
+			if encDst := buf.String(); encDst != output {
+				t.Errorf("buf(%q*%d) = %v, want %v", test.dec, multiplier, encDst, output)
+				continue
+			}
+
+			dec := NewDecoder(&buf)
+			var decBuf bytes.Buffer
+			w := struct{ io.Writer }{&decBuf} // io.Writer only; not io.ReaderFrom
+			if _, err := io.CopyBuffer(w, dec, make([]byte, 7)); err != nil || decBuf.Len() != len(input) {
+				t.Errorf("decoder.Read(%q*%d) = (%d, %v), want (%d, nil)", test.enc, multiplier, decBuf.Len(), err, len(input))
+			}
+
+			if !bytes.Equal(decBuf.Bytes(), input) {
+				t.Errorf("decBuf(%q*%d) = %v, want %v", test.dec, multiplier, decBuf.Bytes(), input)
+				continue
+			}
+		}
+	}
+}
+
+func TestDecoderErr(t *testing.T) {
+	for _, tt := range errTests {
+		dec := NewDecoder(strings.NewReader(tt.in))
+		out, err := io.ReadAll(dec)
+		wantErr := tt.err
+		// Decoder is reading from stream, so it reports io.ErrUnexpectedEOF instead of ErrLength.
+		if wantErr == ErrLength {
+			wantErr = io.ErrUnexpectedEOF
+		}
+		if string(out) != tt.out || err != wantErr {
+			t.Errorf("NewDecoder(%q) = %q, %v, want %q, %v", tt.in, out, err, tt.out, wantErr)
+		}
+	}
+}
+
+func TestDumper(t *testing.T) {
+	var in [40]byte
+	for i := range in {
+		in[i] = byte(i + 30)
+	}
+
+	for stride := 1; stride < len(in); stride++ {
+		var out bytes.Buffer
+		dumper := Dumper(&out)
+		done := 0
+		for done < len(in) {
+			todo := done + stride
+			if todo > len(in) {
+				todo = len(in)
+			}
+			dumper.Write(in[done:todo])
+			done = todo
+		}
+
+		dumper.Close()
+		if !bytes.Equal(out.Bytes(), expectedHexDump) {
+			t.Errorf("stride: %d failed. got:\n%s\nwant:\n%s", stride, out.Bytes(), expectedHexDump)
+		}
+	}
+}
+
+func TestDumper_doubleclose(t *testing.T) {
+	var out bytes.Buffer
+	dumper := Dumper(&out)
+
+	dumper.Write([]byte(`gopher`))
+	dumper.Close()
+	dumper.Close()
+	dumper.Write([]byte(`gopher`))
+	dumper.Close()
+
+	expected := "00000000  67 6f 70 68 65 72                                 |gopher|\n"
+	if out.String() != expected {
+		t.Fatalf("got:\n%#v\nwant:\n%#v", out.String(), expected)
+	}
+}
+
+func TestDumper_earlyclose(t *testing.T) {
+	var out bytes.Buffer
+	dumper := Dumper(&out)
+
+	dumper.Close()
+	dumper.Write([]byte(`gopher`))
+
+	expected := ""
+	if out.String() != expected {
+		t.Fatalf("got:\n%#v\nwant:\n%#v", out.String(), expected)
+	}
+}
+
+func TestDump(t *testing.T) {
+	var in [40]byte
+	for i := range in {
+		in[i] = byte(i + 30)
+	}
+
+	out := []byte(Dump(in[:]))
+	if !bytes.Equal(out, expectedHexDump) {
+		t.Errorf("got:\n%s\nwant:\n%s", out, expectedHexDump)
+	}
+}
+
+var expectedHexDump = []byte(`00000000  1e 1f 20 21 22 23 24 25  26 27 28 29 2a 2b 2c 2d  |.. !"#$%&'()*+,-|
+00000010  2e 2f 30 31 32 33 34 35  36 37 38 39 3a 3b 3c 3d  |./0123456789:;<=|
+00000020  3e 3f 40 41 42 43 44 45                           |>?@ABCDE|
+`)
+
+var sink []byte
+
+func BenchmarkEncode(b *testing.B) {
+	for _, size := range []int{256, 1024, 4096, 16384} {
+		src := bytes.Repeat([]byte{2, 3, 5, 7, 9, 11, 13, 17}, size/8)
+		sink = make([]byte, 2*size)
+
+		b.Run(fmt.Sprintf("%v", size), func(b *testing.B) {
+			b.SetBytes(int64(size))
+			for i := 0; i < b.N; i++ {
+				Encode(sink, src)
+			}
+		})
+	}
+}
+
+func BenchmarkDecode(b *testing.B) {
+	for _, size := range []int{256, 1024, 4096, 16384} {
+		src := bytes.Repeat([]byte{'2', 'b', '7', '4', '4', 'f', 'a', 'a'}, size/8)
+		sink = make([]byte, size/2)
+
+		b.Run(fmt.Sprintf("%v", size), func(b *testing.B) {
+			b.SetBytes(int64(size))
+			for i := 0; i < b.N; i++ {
+				Decode(sink, src)
+			}
+		})
+	}
+}
+
+func BenchmarkDump(b *testing.B) {
+	for _, size := range []int{256, 1024, 4096, 16384} {
+		src := bytes.Repeat([]byte{2, 3, 5, 7, 9, 11, 13, 17}, size/8)
+
+		b.Run(fmt.Sprintf("%v", size), func(b *testing.B) {
+			b.SetBytes(int64(size))
+			for i := 0; i < b.N; i++ {
+				Dump(src)
+			}
+		})
+	}
+}
diff --git a/src/encoding/json/bench_test.go b/src/encoding/json/bench_test.go
new file mode 100644
index 0000000..9560914
--- /dev/null
+++ b/src/encoding/json/bench_test.go
@@ -0,0 +1,410 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Large data benchmark.
+// The JSON data is a summary of agl's changes in the
+// go, webkit, and chromium open source projects.
+// We benchmark converting between the JSON form
+// and in-memory data structures.
+
+package json
+
+import (
+	"bytes"
+	"compress/gzip"
+	"fmt"
+	"internal/testenv"
+	"io"
+	"os"
+	"reflect"
+	"runtime"
+	"strings"
+	"sync"
+	"testing"
+)
+
+type codeResponse struct {
+	Tree     *codeNode `json:"tree"`
+	Username string    `json:"username"`
+}
+
+type codeNode struct {
+	Name     string      `json:"name"`
+	Kids     []*codeNode `json:"kids"`
+	CLWeight float64     `json:"cl_weight"`
+	Touches  int         `json:"touches"`
+	MinT     int64       `json:"min_t"`
+	MaxT     int64       `json:"max_t"`
+	MeanT    int64       `json:"mean_t"`
+}
+
+var codeJSON []byte
+var codeStruct codeResponse
+
+func codeInit() {
+	f, err := os.Open("testdata/code.json.gz")
+	if err != nil {
+		panic(err)
+	}
+	defer f.Close()
+	gz, err := gzip.NewReader(f)
+	if err != nil {
+		panic(err)
+	}
+	data, err := io.ReadAll(gz)
+	if err != nil {
+		panic(err)
+	}
+
+	codeJSON = data
+
+	if err := Unmarshal(codeJSON, &codeStruct); err != nil {
+		panic("unmarshal code.json: " + err.Error())
+	}
+
+	if data, err = Marshal(&codeStruct); err != nil {
+		panic("marshal code.json: " + err.Error())
+	}
+
+	if !bytes.Equal(data, codeJSON) {
+		println("different lengths", len(data), len(codeJSON))
+		for i := 0; i < len(data) && i < len(codeJSON); i++ {
+			if data[i] != codeJSON[i] {
+				println("re-marshal: changed at byte", i)
+				println("orig: ", string(codeJSON[i-10:i+10]))
+				println("new: ", string(data[i-10:i+10]))
+				break
+			}
+		}
+		panic("re-marshal code.json: different result")
+	}
+}
+
+func BenchmarkCodeEncoder(b *testing.B) {
+	b.ReportAllocs()
+	if codeJSON == nil {
+		b.StopTimer()
+		codeInit()
+		b.StartTimer()
+	}
+	b.RunParallel(func(pb *testing.PB) {
+		enc := NewEncoder(io.Discard)
+		for pb.Next() {
+			if err := enc.Encode(&codeStruct); err != nil {
+				b.Fatal("Encode:", err)
+			}
+		}
+	})
+	b.SetBytes(int64(len(codeJSON)))
+}
+
+func BenchmarkCodeMarshal(b *testing.B) {
+	b.ReportAllocs()
+	if codeJSON == nil {
+		b.StopTimer()
+		codeInit()
+		b.StartTimer()
+	}
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			if _, err := Marshal(&codeStruct); err != nil {
+				b.Fatal("Marshal:", err)
+			}
+		}
+	})
+	b.SetBytes(int64(len(codeJSON)))
+}
+
+func benchMarshalBytes(n int) func(*testing.B) {
+	sample := []byte("hello world")
+	// Use a struct pointer, to avoid an allocation when passing it as an
+	// interface parameter to Marshal.
+	v := &struct {
+		Bytes []byte
+	}{
+		bytes.Repeat(sample, (n/len(sample))+1)[:n],
+	}
+	return func(b *testing.B) {
+		for i := 0; i < b.N; i++ {
+			if _, err := Marshal(v); err != nil {
+				b.Fatal("Marshal:", err)
+			}
+		}
+	}
+}
+
+func BenchmarkMarshalBytes(b *testing.B) {
+	b.ReportAllocs()
+	// 32 fits within encodeState.scratch.
+	b.Run("32", benchMarshalBytes(32))
+	// 256 doesn't fit in encodeState.scratch, but is small enough to
+	// allocate and avoid the slower base64.NewEncoder.
+	b.Run("256", benchMarshalBytes(256))
+	// 4096 is large enough that we want to avoid allocating for it.
+	b.Run("4096", benchMarshalBytes(4096))
+}
+
+func BenchmarkCodeDecoder(b *testing.B) {
+	b.ReportAllocs()
+	if codeJSON == nil {
+		b.StopTimer()
+		codeInit()
+		b.StartTimer()
+	}
+	b.RunParallel(func(pb *testing.PB) {
+		var buf bytes.Buffer
+		dec := NewDecoder(&buf)
+		var r codeResponse
+		for pb.Next() {
+			buf.Write(codeJSON)
+			// hide EOF
+			buf.WriteByte('\n')
+			buf.WriteByte('\n')
+			buf.WriteByte('\n')
+			if err := dec.Decode(&r); err != nil {
+				b.Fatal("Decode:", err)
+			}
+		}
+	})
+	b.SetBytes(int64(len(codeJSON)))
+}
+
+func BenchmarkUnicodeDecoder(b *testing.B) {
+	b.ReportAllocs()
+	j := []byte(`"\uD83D\uDE01"`)
+	b.SetBytes(int64(len(j)))
+	r := bytes.NewReader(j)
+	dec := NewDecoder(r)
+	var out string
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		if err := dec.Decode(&out); err != nil {
+			b.Fatal("Decode:", err)
+		}
+		r.Seek(0, 0)
+	}
+}
+
+func BenchmarkDecoderStream(b *testing.B) {
+	b.ReportAllocs()
+	b.StopTimer()
+	var buf bytes.Buffer
+	dec := NewDecoder(&buf)
+	buf.WriteString(`"` + strings.Repeat("x", 1000000) + `"` + "\n\n\n")
+	var x any
+	if err := dec.Decode(&x); err != nil {
+		b.Fatal("Decode:", err)
+	}
+	ones := strings.Repeat(" 1\n", 300000) + "\n\n\n"
+	b.StartTimer()
+	for i := 0; i < b.N; i++ {
+		if i%300000 == 0 {
+			buf.WriteString(ones)
+		}
+		x = nil
+		if err := dec.Decode(&x); err != nil || x != 1.0 {
+			b.Fatalf("Decode: %v after %d", err, i)
+		}
+	}
+}
+
+func BenchmarkCodeUnmarshal(b *testing.B) {
+	b.ReportAllocs()
+	if codeJSON == nil {
+		b.StopTimer()
+		codeInit()
+		b.StartTimer()
+	}
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			var r codeResponse
+			if err := Unmarshal(codeJSON, &r); err != nil {
+				b.Fatal("Unmarshal:", err)
+			}
+		}
+	})
+	b.SetBytes(int64(len(codeJSON)))
+}
+
+func BenchmarkCodeUnmarshalReuse(b *testing.B) {
+	b.ReportAllocs()
+	if codeJSON == nil {
+		b.StopTimer()
+		codeInit()
+		b.StartTimer()
+	}
+	b.RunParallel(func(pb *testing.PB) {
+		var r codeResponse
+		for pb.Next() {
+			if err := Unmarshal(codeJSON, &r); err != nil {
+				b.Fatal("Unmarshal:", err)
+			}
+		}
+	})
+	b.SetBytes(int64(len(codeJSON)))
+}
+
+func BenchmarkUnmarshalString(b *testing.B) {
+	b.ReportAllocs()
+	data := []byte(`"hello, world"`)
+	b.RunParallel(func(pb *testing.PB) {
+		var s string
+		for pb.Next() {
+			if err := Unmarshal(data, &s); err != nil {
+				b.Fatal("Unmarshal:", err)
+			}
+		}
+	})
+}
+
+func BenchmarkUnmarshalFloat64(b *testing.B) {
+	b.ReportAllocs()
+	data := []byte(`3.14`)
+	b.RunParallel(func(pb *testing.PB) {
+		var f float64
+		for pb.Next() {
+			if err := Unmarshal(data, &f); err != nil {
+				b.Fatal("Unmarshal:", err)
+			}
+		}
+	})
+}
+
+func BenchmarkUnmarshalInt64(b *testing.B) {
+	b.ReportAllocs()
+	data := []byte(`3`)
+	b.RunParallel(func(pb *testing.PB) {
+		var x int64
+		for pb.Next() {
+			if err := Unmarshal(data, &x); err != nil {
+				b.Fatal("Unmarshal:", err)
+			}
+		}
+	})
+}
+
+func BenchmarkIssue10335(b *testing.B) {
+	b.ReportAllocs()
+	j := []byte(`{"a":{ }}`)
+	b.RunParallel(func(pb *testing.PB) {
+		var s struct{}
+		for pb.Next() {
+			if err := Unmarshal(j, &s); err != nil {
+				b.Fatal(err)
+			}
+		}
+	})
+}
+
+func BenchmarkIssue34127(b *testing.B) {
+	b.ReportAllocs()
+	j := struct {
+		Bar string `json:"bar,string"`
+	}{
+		Bar: `foobar`,
+	}
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			if _, err := Marshal(&j); err != nil {
+				b.Fatal(err)
+			}
+		}
+	})
+}
+
+func BenchmarkUnmapped(b *testing.B) {
+	b.ReportAllocs()
+	j := []byte(`{"s": "hello", "y": 2, "o": {"x": 0}, "a": [1, 99, {"x": 1}]}`)
+	b.RunParallel(func(pb *testing.PB) {
+		var s struct{}
+		for pb.Next() {
+			if err := Unmarshal(j, &s); err != nil {
+				b.Fatal(err)
+			}
+		}
+	})
+}
+
+func BenchmarkTypeFieldsCache(b *testing.B) {
+	b.ReportAllocs()
+	var maxTypes int = 1e6
+	if testenv.Builder() != "" {
+		maxTypes = 1e3 // restrict cache sizes on builders
+	}
+
+	// Dynamically generate many new types.
+	types := make([]reflect.Type, maxTypes)
+	fs := []reflect.StructField{{
+		Type:  reflect.TypeOf(""),
+		Index: []int{0},
+	}}
+	for i := range types {
+		fs[0].Name = fmt.Sprintf("TypeFieldsCache%d", i)
+		types[i] = reflect.StructOf(fs)
+	}
+
+	// clearClear clears the cache. Other JSON operations, must not be running.
+	clearCache := func() {
+		fieldCache = sync.Map{}
+	}
+
+	// MissTypes tests the performance of repeated cache misses.
+	// This measures the time to rebuild a cache of size nt.
+	for nt := 1; nt <= maxTypes; nt *= 10 {
+		ts := types[:nt]
+		b.Run(fmt.Sprintf("MissTypes%d", nt), func(b *testing.B) {
+			nc := runtime.GOMAXPROCS(0)
+			for i := 0; i < b.N; i++ {
+				clearCache()
+				var wg sync.WaitGroup
+				for j := 0; j < nc; j++ {
+					wg.Add(1)
+					go func(j int) {
+						for _, t := range ts[(j*len(ts))/nc : ((j+1)*len(ts))/nc] {
+							cachedTypeFields(t)
+						}
+						wg.Done()
+					}(j)
+				}
+				wg.Wait()
+			}
+		})
+	}
+
+	// HitTypes tests the performance of repeated cache hits.
+	// This measures the average time of each cache lookup.
+	for nt := 1; nt <= maxTypes; nt *= 10 {
+		// Pre-warm a cache of size nt.
+		clearCache()
+		for _, t := range types[:nt] {
+			cachedTypeFields(t)
+		}
+		b.Run(fmt.Sprintf("HitTypes%d", nt), func(b *testing.B) {
+			b.RunParallel(func(pb *testing.PB) {
+				for pb.Next() {
+					cachedTypeFields(types[0])
+				}
+			})
+		})
+	}
+}
+
+func BenchmarkEncodeMarshaler(b *testing.B) {
+	b.ReportAllocs()
+
+	m := struct {
+		A int
+		B RawMessage
+	}{}
+
+	b.RunParallel(func(pb *testing.PB) {
+		enc := NewEncoder(io.Discard)
+
+		for pb.Next() {
+			if err := enc.Encode(&m); err != nil {
+				b.Fatal("Encode:", err)
+			}
+		}
+	})
+}
diff --git a/src/encoding/json/decode.go b/src/encoding/json/decode.go
new file mode 100644
index 0000000..555df0b
--- /dev/null
+++ b/src/encoding/json/decode.go
@@ -0,0 +1,1310 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Represents JSON data structure using native Go types: booleans, floats,
+// strings, arrays, and maps.
+
+package json
+
+import (
+	"encoding"
+	"encoding/base64"
+	"fmt"
+	"reflect"
+	"strconv"
+	"strings"
+	"unicode"
+	"unicode/utf16"
+	"unicode/utf8"
+)
+
+// Unmarshal parses the JSON-encoded data and stores the result
+// in the value pointed to by v. If v is nil or not a pointer,
+// Unmarshal returns an InvalidUnmarshalError.
+//
+// Unmarshal uses the inverse of the encodings that
+// Marshal uses, allocating maps, slices, and pointers as necessary,
+// with the following additional rules:
+//
+// To unmarshal JSON into a pointer, Unmarshal first handles the case of
+// the JSON being the JSON literal null. In that case, Unmarshal sets
+// the pointer to nil. Otherwise, Unmarshal unmarshals the JSON into
+// the value pointed at by the pointer. If the pointer is nil, Unmarshal
+// allocates a new value for it to point to.
+//
+// To unmarshal JSON into a value implementing the Unmarshaler interface,
+// Unmarshal calls that value's UnmarshalJSON method, including
+// when the input is a JSON null.
+// Otherwise, if the value implements encoding.TextUnmarshaler
+// and the input is a JSON quoted string, Unmarshal calls that value's
+// UnmarshalText method with the unquoted form of the string.
+//
+// To unmarshal JSON into a struct, Unmarshal matches incoming object
+// keys to the keys used by Marshal (either the struct field name or its tag),
+// preferring an exact match but also accepting a case-insensitive match. By
+// default, object keys which don't have a corresponding struct field are
+// ignored (see Decoder.DisallowUnknownFields for an alternative).
+//
+// To unmarshal JSON into an interface value,
+// Unmarshal stores one of these in the interface value:
+//
+//	bool, for JSON booleans
+//	float64, for JSON numbers
+//	string, for JSON strings
+//	[]interface{}, for JSON arrays
+//	map[string]interface{}, for JSON objects
+//	nil for JSON null
+//
+// To unmarshal a JSON array into a slice, Unmarshal resets the slice length
+// to zero and then appends each element to the slice.
+// As a special case, to unmarshal an empty JSON array into a slice,
+// Unmarshal replaces the slice with a new empty slice.
+//
+// To unmarshal a JSON array into a Go array, Unmarshal decodes
+// JSON array elements into corresponding Go array elements.
+// If the Go array is smaller than the JSON array,
+// the additional JSON array elements are discarded.
+// If the JSON array is smaller than the Go array,
+// the additional Go array elements are set to zero values.
+//
+// To unmarshal a JSON object into a map, Unmarshal first establishes a map to
+// use. If the map is nil, Unmarshal allocates a new map. Otherwise Unmarshal
+// reuses the existing map, keeping existing entries. Unmarshal then stores
+// key-value pairs from the JSON object into the map. The map's key type must
+// either be any string type, an integer, implement json.Unmarshaler, or
+// implement encoding.TextUnmarshaler.
+//
+// If a JSON value is not appropriate for a given target type,
+// or if a JSON number overflows the target type, Unmarshal
+// skips that field and completes the unmarshaling as best it can.
+// If no more serious errors are encountered, Unmarshal returns
+// an UnmarshalTypeError describing the earliest such error. In any
+// case, it's not guaranteed that all the remaining fields following
+// the problematic one will be unmarshaled into the target object.
+//
+// The JSON null value unmarshals into an interface, map, pointer, or slice
+// by setting that Go value to nil. Because null is often used in JSON to mean
+// ``not present,'' unmarshaling a JSON null into any other Go type has no effect
+// on the value and produces no error.
+//
+// When unmarshaling quoted strings, invalid UTF-8 or
+// invalid UTF-16 surrogate pairs are not treated as an error.
+// Instead, they are replaced by the Unicode replacement
+// character U+FFFD.
+//
+func Unmarshal(data []byte, v any) error {
+	// Check for well-formedness.
+	// Avoids filling out half a data structure
+	// before discovering a JSON syntax error.
+	var d decodeState
+	err := checkValid(data, &d.scan)
+	if err != nil {
+		return err
+	}
+
+	d.init(data)
+	return d.unmarshal(v)
+}
+
+// Unmarshaler is the interface implemented by types
+// that can unmarshal a JSON description of themselves.
+// The input can be assumed to be a valid encoding of
+// a JSON value. UnmarshalJSON must copy the JSON data
+// if it wishes to retain the data after returning.
+//
+// By convention, to approximate the behavior of Unmarshal itself,
+// Unmarshalers implement UnmarshalJSON([]byte("null")) as a no-op.
+type Unmarshaler interface {
+	UnmarshalJSON([]byte) error
+}
+
+// An UnmarshalTypeError describes a JSON value that was
+// not appropriate for a value of a specific Go type.
+type UnmarshalTypeError struct {
+	Value  string       // description of JSON value - "bool", "array", "number -5"
+	Type   reflect.Type // type of Go value it could not be assigned to
+	Offset int64        // error occurred after reading Offset bytes
+	Struct string       // name of the struct type containing the field
+	Field  string       // the full path from root node to the field
+}
+
+func (e *UnmarshalTypeError) Error() string {
+	if e.Struct != "" || e.Field != "" {
+		return "json: cannot unmarshal " + e.Value + " into Go struct field " + e.Struct + "." + e.Field + " of type " + e.Type.String()
+	}
+	return "json: cannot unmarshal " + e.Value + " into Go value of type " + e.Type.String()
+}
+
+// An UnmarshalFieldError describes a JSON object key that
+// led to an unexported (and therefore unwritable) struct field.
+//
+// Deprecated: No longer used; kept for compatibility.
+type UnmarshalFieldError struct {
+	Key   string
+	Type  reflect.Type
+	Field reflect.StructField
+}
+
+func (e *UnmarshalFieldError) Error() string {
+	return "json: cannot unmarshal object key " + strconv.Quote(e.Key) + " into unexported field " + e.Field.Name + " of type " + e.Type.String()
+}
+
+// An InvalidUnmarshalError describes an invalid argument passed to Unmarshal.
+// (The argument to Unmarshal must be a non-nil pointer.)
+type InvalidUnmarshalError struct {
+	Type reflect.Type
+}
+
+func (e *InvalidUnmarshalError) Error() string {
+	if e.Type == nil {
+		return "json: Unmarshal(nil)"
+	}
+
+	if e.Type.Kind() != reflect.Pointer {
+		return "json: Unmarshal(non-pointer " + e.Type.String() + ")"
+	}
+	return "json: Unmarshal(nil " + e.Type.String() + ")"
+}
+
+func (d *decodeState) unmarshal(v any) error {
+	rv := reflect.ValueOf(v)
+	if rv.Kind() != reflect.Pointer || rv.IsNil() {
+		return &InvalidUnmarshalError{reflect.TypeOf(v)}
+	}
+
+	d.scan.reset()
+	d.scanWhile(scanSkipSpace)
+	// We decode rv not rv.Elem because the Unmarshaler interface
+	// test must be applied at the top level of the value.
+	err := d.value(rv)
+	if err != nil {
+		return d.addErrorContext(err)
+	}
+	return d.savedError
+}
+
+// A Number represents a JSON number literal.
+type Number string
+
+// String returns the literal text of the number.
+func (n Number) String() string { return string(n) }
+
+// Float64 returns the number as a float64.
+func (n Number) Float64() (float64, error) {
+	return strconv.ParseFloat(string(n), 64)
+}
+
+// Int64 returns the number as an int64.
+func (n Number) Int64() (int64, error) {
+	return strconv.ParseInt(string(n), 10, 64)
+}
+
+// An errorContext provides context for type errors during decoding.
+type errorContext struct {
+	Struct     reflect.Type
+	FieldStack []string
+}
+
+// decodeState represents the state while decoding a JSON value.
+type decodeState struct {
+	data                  []byte
+	off                   int // next read offset in data
+	opcode                int // last read result
+	scan                  scanner
+	errorContext          *errorContext
+	savedError            error
+	useNumber             bool
+	disallowUnknownFields bool
+}
+
+// readIndex returns the position of the last byte read.
+func (d *decodeState) readIndex() int {
+	return d.off - 1
+}
+
+// phasePanicMsg is used as a panic message when we end up with something that
+// shouldn't happen. It can indicate a bug in the JSON decoder, or that
+// something is editing the data slice while the decoder executes.
+const phasePanicMsg = "JSON decoder out of sync - data changing underfoot?"
+
+func (d *decodeState) init(data []byte) *decodeState {
+	d.data = data
+	d.off = 0
+	d.savedError = nil
+	if d.errorContext != nil {
+		d.errorContext.Struct = nil
+		// Reuse the allocated space for the FieldStack slice.
+		d.errorContext.FieldStack = d.errorContext.FieldStack[:0]
+	}
+	return d
+}
+
+// saveError saves the first err it is called with,
+// for reporting at the end of the unmarshal.
+func (d *decodeState) saveError(err error) {
+	if d.savedError == nil {
+		d.savedError = d.addErrorContext(err)
+	}
+}
+
+// addErrorContext returns a new error enhanced with information from d.errorContext
+func (d *decodeState) addErrorContext(err error) error {
+	if d.errorContext != nil && (d.errorContext.Struct != nil || len(d.errorContext.FieldStack) > 0) {
+		switch err := err.(type) {
+		case *UnmarshalTypeError:
+			err.Struct = d.errorContext.Struct.Name()
+			err.Field = strings.Join(d.errorContext.FieldStack, ".")
+		}
+	}
+	return err
+}
+
+// skip scans to the end of what was started.
+func (d *decodeState) skip() {
+	s, data, i := &d.scan, d.data, d.off
+	depth := len(s.parseState)
+	for {
+		op := s.step(s, data[i])
+		i++
+		if len(s.parseState) < depth {
+			d.off = i
+			d.opcode = op
+			return
+		}
+	}
+}
+
+// scanNext processes the byte at d.data[d.off].
+func (d *decodeState) scanNext() {
+	if d.off < len(d.data) {
+		d.opcode = d.scan.step(&d.scan, d.data[d.off])
+		d.off++
+	} else {
+		d.opcode = d.scan.eof()
+		d.off = len(d.data) + 1 // mark processed EOF with len+1
+	}
+}
+
+// scanWhile processes bytes in d.data[d.off:] until it
+// receives a scan code not equal to op.
+func (d *decodeState) scanWhile(op int) {
+	s, data, i := &d.scan, d.data, d.off
+	for i < len(data) {
+		newOp := s.step(s, data[i])
+		i++
+		if newOp != op {
+			d.opcode = newOp
+			d.off = i
+			return
+		}
+	}
+
+	d.off = len(data) + 1 // mark processed EOF with len+1
+	d.opcode = d.scan.eof()
+}
+
+// rescanLiteral is similar to scanWhile(scanContinue), but it specialises the
+// common case where we're decoding a literal. The decoder scans the input
+// twice, once for syntax errors and to check the length of the value, and the
+// second to perform the decoding.
+//
+// Only in the second step do we use decodeState to tokenize literals, so we
+// know there aren't any syntax errors. We can take advantage of that knowledge,
+// and scan a literal's bytes much more quickly.
+func (d *decodeState) rescanLiteral() {
+	data, i := d.data, d.off
+Switch:
+	switch data[i-1] {
+	case '"': // string
+		for ; i < len(data); i++ {
+			switch data[i] {
+			case '\\':
+				i++ // escaped char
+			case '"':
+				i++ // tokenize the closing quote too
+				break Switch
+			}
+		}
+	case '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '-': // number
+		for ; i < len(data); i++ {
+			switch data[i] {
+			case '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
+				'.', 'e', 'E', '+', '-':
+			default:
+				break Switch
+			}
+		}
+	case 't': // true
+		i += len("rue")
+	case 'f': // false
+		i += len("alse")
+	case 'n': // null
+		i += len("ull")
+	}
+	if i < len(data) {
+		d.opcode = stateEndValue(&d.scan, data[i])
+	} else {
+		d.opcode = scanEnd
+	}
+	d.off = i + 1
+}
+
+// value consumes a JSON value from d.data[d.off-1:], decoding into v, and
+// reads the following byte ahead. If v is invalid, the value is discarded.
+// The first byte of the value has been read already.
+func (d *decodeState) value(v reflect.Value) error {
+	switch d.opcode {
+	default:
+		panic(phasePanicMsg)
+
+	case scanBeginArray:
+		if v.IsValid() {
+			if err := d.array(v); err != nil {
+				return err
+			}
+		} else {
+			d.skip()
+		}
+		d.scanNext()
+
+	case scanBeginObject:
+		if v.IsValid() {
+			if err := d.object(v); err != nil {
+				return err
+			}
+		} else {
+			d.skip()
+		}
+		d.scanNext()
+
+	case scanBeginLiteral:
+		// All bytes inside literal return scanContinue op code.
+		start := d.readIndex()
+		d.rescanLiteral()
+
+		if v.IsValid() {
+			if err := d.literalStore(d.data[start:d.readIndex()], v, false); err != nil {
+				return err
+			}
+		}
+	}
+	return nil
+}
+
+type unquotedValue struct{}
+
+// valueQuoted is like value but decodes a
+// quoted string literal or literal null into an interface value.
+// If it finds anything other than a quoted string literal or null,
+// valueQuoted returns unquotedValue{}.
+func (d *decodeState) valueQuoted() any {
+	switch d.opcode {
+	default:
+		panic(phasePanicMsg)
+
+	case scanBeginArray, scanBeginObject:
+		d.skip()
+		d.scanNext()
+
+	case scanBeginLiteral:
+		v := d.literalInterface()
+		switch v.(type) {
+		case nil, string:
+			return v
+		}
+	}
+	return unquotedValue{}
+}
+
+// indirect walks down v allocating pointers as needed,
+// until it gets to a non-pointer.
+// If it encounters an Unmarshaler, indirect stops and returns that.
+// If decodingNull is true, indirect stops at the first settable pointer so it
+// can be set to nil.
+func indirect(v reflect.Value, decodingNull bool) (Unmarshaler, encoding.TextUnmarshaler, reflect.Value) {
+	// Issue #24153 indicates that it is generally not a guaranteed property
+	// that you may round-trip a reflect.Value by calling Value.Addr().Elem()
+	// and expect the value to still be settable for values derived from
+	// unexported embedded struct fields.
+	//
+	// The logic below effectively does this when it first addresses the value
+	// (to satisfy possible pointer methods) and continues to dereference
+	// subsequent pointers as necessary.
+	//
+	// After the first round-trip, we set v back to the original value to
+	// preserve the original RW flags contained in reflect.Value.
+	v0 := v
+	haveAddr := false
+
+	// If v is a named type and is addressable,
+	// start with its address, so that if the type has pointer methods,
+	// we find them.
+	if v.Kind() != reflect.Pointer && v.Type().Name() != "" && v.CanAddr() {
+		haveAddr = true
+		v = v.Addr()
+	}
+	for {
+		// Load value from interface, but only if the result will be
+		// usefully addressable.
+		if v.Kind() == reflect.Interface && !v.IsNil() {
+			e := v.Elem()
+			if e.Kind() == reflect.Pointer && !e.IsNil() && (!decodingNull || e.Elem().Kind() == reflect.Pointer) {
+				haveAddr = false
+				v = e
+				continue
+			}
+		}
+
+		if v.Kind() != reflect.Pointer {
+			break
+		}
+
+		if decodingNull && v.CanSet() {
+			break
+		}
+
+		// Prevent infinite loop if v is an interface pointing to its own address:
+		//     var v interface{}
+		//     v = &v
+		if v.Elem().Kind() == reflect.Interface && v.Elem().Elem() == v {
+			v = v.Elem()
+			break
+		}
+		if v.IsNil() {
+			v.Set(reflect.New(v.Type().Elem()))
+		}
+		if v.Type().NumMethod() > 0 && v.CanInterface() {
+			if u, ok := v.Interface().(Unmarshaler); ok {
+				return u, nil, reflect.Value{}
+			}
+			if !decodingNull {
+				if u, ok := v.Interface().(encoding.TextUnmarshaler); ok {
+					return nil, u, reflect.Value{}
+				}
+			}
+		}
+
+		if haveAddr {
+			v = v0 // restore original value after round-trip Value.Addr().Elem()
+			haveAddr = false
+		} else {
+			v = v.Elem()
+		}
+	}
+	return nil, nil, v
+}
+
+// array consumes an array from d.data[d.off-1:], decoding into v.
+// The first byte of the array ('[') has been read already.
+func (d *decodeState) array(v reflect.Value) error {
+	// Check for unmarshaler.
+	u, ut, pv := indirect(v, false)
+	if u != nil {
+		start := d.readIndex()
+		d.skip()
+		return u.UnmarshalJSON(d.data[start:d.off])
+	}
+	if ut != nil {
+		d.saveError(&UnmarshalTypeError{Value: "array", Type: v.Type(), Offset: int64(d.off)})
+		d.skip()
+		return nil
+	}
+	v = pv
+
+	// Check type of target.
+	switch v.Kind() {
+	case reflect.Interface:
+		if v.NumMethod() == 0 {
+			// Decoding into nil interface? Switch to non-reflect code.
+			ai := d.arrayInterface()
+			v.Set(reflect.ValueOf(ai))
+			return nil
+		}
+		// Otherwise it's invalid.
+		fallthrough
+	default:
+		d.saveError(&UnmarshalTypeError{Value: "array", Type: v.Type(), Offset: int64(d.off)})
+		d.skip()
+		return nil
+	case reflect.Array, reflect.Slice:
+		break
+	}
+
+	i := 0
+	for {
+		// Look ahead for ] - can only happen on first iteration.
+		d.scanWhile(scanSkipSpace)
+		if d.opcode == scanEndArray {
+			break
+		}
+
+		// Get element of array, growing if necessary.
+		if v.Kind() == reflect.Slice {
+			// Grow slice if necessary
+			if i >= v.Cap() {
+				newcap := v.Cap() + v.Cap()/2
+				if newcap < 4 {
+					newcap = 4
+				}
+				newv := reflect.MakeSlice(v.Type(), v.Len(), newcap)
+				reflect.Copy(newv, v)
+				v.Set(newv)
+			}
+			if i >= v.Len() {
+				v.SetLen(i + 1)
+			}
+		}
+
+		if i < v.Len() {
+			// Decode into element.
+			if err := d.value(v.Index(i)); err != nil {
+				return err
+			}
+		} else {
+			// Ran out of fixed array: skip.
+			if err := d.value(reflect.Value{}); err != nil {
+				return err
+			}
+		}
+		i++
+
+		// Next token must be , or ].
+		if d.opcode == scanSkipSpace {
+			d.scanWhile(scanSkipSpace)
+		}
+		if d.opcode == scanEndArray {
+			break
+		}
+		if d.opcode != scanArrayValue {
+			panic(phasePanicMsg)
+		}
+	}
+
+	if i < v.Len() {
+		if v.Kind() == reflect.Array {
+			// Array. Zero the rest.
+			z := reflect.Zero(v.Type().Elem())
+			for ; i < v.Len(); i++ {
+				v.Index(i).Set(z)
+			}
+		} else {
+			v.SetLen(i)
+		}
+	}
+	if i == 0 && v.Kind() == reflect.Slice {
+		v.Set(reflect.MakeSlice(v.Type(), 0, 0))
+	}
+	return nil
+}
+
+var nullLiteral = []byte("null")
+var textUnmarshalerType = reflect.TypeOf((*encoding.TextUnmarshaler)(nil)).Elem()
+
+// object consumes an object from d.data[d.off-1:], decoding into v.
+// The first byte ('{') of the object has been read already.
+func (d *decodeState) object(v reflect.Value) error {
+	// Check for unmarshaler.
+	u, ut, pv := indirect(v, false)
+	if u != nil {
+		start := d.readIndex()
+		d.skip()
+		return u.UnmarshalJSON(d.data[start:d.off])
+	}
+	if ut != nil {
+		d.saveError(&UnmarshalTypeError{Value: "object", Type: v.Type(), Offset: int64(d.off)})
+		d.skip()
+		return nil
+	}
+	v = pv
+	t := v.Type()
+
+	// Decoding into nil interface? Switch to non-reflect code.
+	if v.Kind() == reflect.Interface && v.NumMethod() == 0 {
+		oi := d.objectInterface()
+		v.Set(reflect.ValueOf(oi))
+		return nil
+	}
+
+	var fields structFields
+
+	// Check type of target:
+	//   struct or
+	//   map[T1]T2 where T1 is string, an integer type,
+	//             or an encoding.TextUnmarshaler
+	switch v.Kind() {
+	case reflect.Map:
+		// Map key must either have string kind, have an integer kind,
+		// or be an encoding.TextUnmarshaler.
+		switch t.Key().Kind() {
+		case reflect.String,
+			reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
+			reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		default:
+			if !reflect.PointerTo(t.Key()).Implements(textUnmarshalerType) {
+				d.saveError(&UnmarshalTypeError{Value: "object", Type: t, Offset: int64(d.off)})
+				d.skip()
+				return nil
+			}
+		}
+		if v.IsNil() {
+			v.Set(reflect.MakeMap(t))
+		}
+	case reflect.Struct:
+		fields = cachedTypeFields(t)
+		// ok
+	default:
+		d.saveError(&UnmarshalTypeError{Value: "object", Type: t, Offset: int64(d.off)})
+		d.skip()
+		return nil
+	}
+
+	var mapElem reflect.Value
+	var origErrorContext errorContext
+	if d.errorContext != nil {
+		origErrorContext = *d.errorContext
+	}
+
+	for {
+		// Read opening " of string key or closing }.
+		d.scanWhile(scanSkipSpace)
+		if d.opcode == scanEndObject {
+			// closing } - can only happen on first iteration.
+			break
+		}
+		if d.opcode != scanBeginLiteral {
+			panic(phasePanicMsg)
+		}
+
+		// Read key.
+		start := d.readIndex()
+		d.rescanLiteral()
+		item := d.data[start:d.readIndex()]
+		key, ok := unquoteBytes(item)
+		if !ok {
+			panic(phasePanicMsg)
+		}
+
+		// Figure out field corresponding to key.
+		var subv reflect.Value
+		destring := false // whether the value is wrapped in a string to be decoded first
+
+		if v.Kind() == reflect.Map {
+			elemType := t.Elem()
+			if !mapElem.IsValid() {
+				mapElem = reflect.New(elemType).Elem()
+			} else {
+				mapElem.Set(reflect.Zero(elemType))
+			}
+			subv = mapElem
+		} else {
+			var f *field
+			if i, ok := fields.nameIndex[string(key)]; ok {
+				// Found an exact name match.
+				f = &fields.list[i]
+			} else {
+				// Fall back to the expensive case-insensitive
+				// linear search.
+				for i := range fields.list {
+					ff := &fields.list[i]
+					if ff.equalFold(ff.nameBytes, key) {
+						f = ff
+						break
+					}
+				}
+			}
+			if f != nil {
+				subv = v
+				destring = f.quoted
+				for _, i := range f.index {
+					if subv.Kind() == reflect.Pointer {
+						if subv.IsNil() {
+							// If a struct embeds a pointer to an unexported type,
+							// it is not possible to set a newly allocated value
+							// since the field is unexported.
+							//
+							// See https://golang.org/issue/21357
+							if !subv.CanSet() {
+								d.saveError(fmt.Errorf("json: cannot set embedded pointer to unexported struct: %v", subv.Type().Elem()))
+								// Invalidate subv to ensure d.value(subv) skips over
+								// the JSON value without assigning it to subv.
+								subv = reflect.Value{}
+								destring = false
+								break
+							}
+							subv.Set(reflect.New(subv.Type().Elem()))
+						}
+						subv = subv.Elem()
+					}
+					subv = subv.Field(i)
+				}
+				if d.errorContext == nil {
+					d.errorContext = new(errorContext)
+				}
+				d.errorContext.FieldStack = append(d.errorContext.FieldStack, f.name)
+				d.errorContext.Struct = t
+			} else if d.disallowUnknownFields {
+				d.saveError(fmt.Errorf("json: unknown field %q", key))
+			}
+		}
+
+		// Read : before value.
+		if d.opcode == scanSkipSpace {
+			d.scanWhile(scanSkipSpace)
+		}
+		if d.opcode != scanObjectKey {
+			panic(phasePanicMsg)
+		}
+		d.scanWhile(scanSkipSpace)
+
+		if destring {
+			switch qv := d.valueQuoted().(type) {
+			case nil:
+				if err := d.literalStore(nullLiteral, subv, false); err != nil {
+					return err
+				}
+			case string:
+				if err := d.literalStore([]byte(qv), subv, true); err != nil {
+					return err
+				}
+			default:
+				d.saveError(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal unquoted value into %v", subv.Type()))
+			}
+		} else {
+			if err := d.value(subv); err != nil {
+				return err
+			}
+		}
+
+		// Write value back to map;
+		// if using struct, subv points into struct already.
+		if v.Kind() == reflect.Map {
+			kt := t.Key()
+			var kv reflect.Value
+			switch {
+			case reflect.PointerTo(kt).Implements(textUnmarshalerType):
+				kv = reflect.New(kt)
+				if err := d.literalStore(item, kv, true); err != nil {
+					return err
+				}
+				kv = kv.Elem()
+			case kt.Kind() == reflect.String:
+				kv = reflect.ValueOf(key).Convert(kt)
+			default:
+				switch kt.Kind() {
+				case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+					s := string(key)
+					n, err := strconv.ParseInt(s, 10, 64)
+					if err != nil || reflect.Zero(kt).OverflowInt(n) {
+						d.saveError(&UnmarshalTypeError{Value: "number " + s, Type: kt, Offset: int64(start + 1)})
+						break
+					}
+					kv = reflect.ValueOf(n).Convert(kt)
+				case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+					s := string(key)
+					n, err := strconv.ParseUint(s, 10, 64)
+					if err != nil || reflect.Zero(kt).OverflowUint(n) {
+						d.saveError(&UnmarshalTypeError{Value: "number " + s, Type: kt, Offset: int64(start + 1)})
+						break
+					}
+					kv = reflect.ValueOf(n).Convert(kt)
+				default:
+					panic("json: Unexpected key type") // should never occur
+				}
+			}
+			if kv.IsValid() {
+				v.SetMapIndex(kv, subv)
+			}
+		}
+
+		// Next token must be , or }.
+		if d.opcode == scanSkipSpace {
+			d.scanWhile(scanSkipSpace)
+		}
+		if d.errorContext != nil {
+			// Reset errorContext to its original state.
+			// Keep the same underlying array for FieldStack, to reuse the
+			// space and avoid unnecessary allocs.
+			d.errorContext.FieldStack = d.errorContext.FieldStack[:len(origErrorContext.FieldStack)]
+			d.errorContext.Struct = origErrorContext.Struct
+		}
+		if d.opcode == scanEndObject {
+			break
+		}
+		if d.opcode != scanObjectValue {
+			panic(phasePanicMsg)
+		}
+	}
+	return nil
+}
+
+// convertNumber converts the number literal s to a float64 or a Number
+// depending on the setting of d.useNumber.
+func (d *decodeState) convertNumber(s string) (any, error) {
+	if d.useNumber {
+		return Number(s), nil
+	}
+	f, err := strconv.ParseFloat(s, 64)
+	if err != nil {
+		return nil, &UnmarshalTypeError{Value: "number " + s, Type: reflect.TypeOf(0.0), Offset: int64(d.off)}
+	}
+	return f, nil
+}
+
+var numberType = reflect.TypeOf(Number(""))
+
+// literalStore decodes a literal stored in item into v.
+//
+// fromQuoted indicates whether this literal came from unwrapping a
+// string from the ",string" struct tag option. this is used only to
+// produce more helpful error messages.
+func (d *decodeState) literalStore(item []byte, v reflect.Value, fromQuoted bool) error {
+	// Check for unmarshaler.
+	if len(item) == 0 {
+		//Empty string given
+		d.saveError(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type()))
+		return nil
+	}
+	isNull := item[0] == 'n' // null
+	u, ut, pv := indirect(v, isNull)
+	if u != nil {
+		return u.UnmarshalJSON(item)
+	}
+	if ut != nil {
+		if item[0] != '"' {
+			if fromQuoted {
+				d.saveError(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type()))
+				return nil
+			}
+			val := "number"
+			switch item[0] {
+			case 'n':
+				val = "null"
+			case 't', 'f':
+				val = "bool"
+			}
+			d.saveError(&UnmarshalTypeError{Value: val, Type: v.Type(), Offset: int64(d.readIndex())})
+			return nil
+		}
+		s, ok := unquoteBytes(item)
+		if !ok {
+			if fromQuoted {
+				return fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type())
+			}
+			panic(phasePanicMsg)
+		}
+		return ut.UnmarshalText(s)
+	}
+
+	v = pv
+
+	switch c := item[0]; c {
+	case 'n': // null
+		// The main parser checks that only true and false can reach here,
+		// but if this was a quoted string input, it could be anything.
+		if fromQuoted && string(item) != "null" {
+			d.saveError(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type()))
+			break
+		}
+		switch v.Kind() {
+		case reflect.Interface, reflect.Pointer, reflect.Map, reflect.Slice:
+			v.Set(reflect.Zero(v.Type()))
+			// otherwise, ignore null for primitives/string
+		}
+	case 't', 'f': // true, false
+		value := item[0] == 't'
+		// The main parser checks that only true and false can reach here,
+		// but if this was a quoted string input, it could be anything.
+		if fromQuoted && string(item) != "true" && string(item) != "false" {
+			d.saveError(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type()))
+			break
+		}
+		switch v.Kind() {
+		default:
+			if fromQuoted {
+				d.saveError(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type()))
+			} else {
+				d.saveError(&UnmarshalTypeError{Value: "bool", Type: v.Type(), Offset: int64(d.readIndex())})
+			}
+		case reflect.Bool:
+			v.SetBool(value)
+		case reflect.Interface:
+			if v.NumMethod() == 0 {
+				v.Set(reflect.ValueOf(value))
+			} else {
+				d.saveError(&UnmarshalTypeError{Value: "bool", Type: v.Type(), Offset: int64(d.readIndex())})
+			}
+		}
+
+	case '"': // string
+		s, ok := unquoteBytes(item)
+		if !ok {
+			if fromQuoted {
+				return fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type())
+			}
+			panic(phasePanicMsg)
+		}
+		switch v.Kind() {
+		default:
+			d.saveError(&UnmarshalTypeError{Value: "string", Type: v.Type(), Offset: int64(d.readIndex())})
+		case reflect.Slice:
+			if v.Type().Elem().Kind() != reflect.Uint8 {
+				d.saveError(&UnmarshalTypeError{Value: "string", Type: v.Type(), Offset: int64(d.readIndex())})
+				break
+			}
+			b := make([]byte, base64.StdEncoding.DecodedLen(len(s)))
+			n, err := base64.StdEncoding.Decode(b, s)
+			if err != nil {
+				d.saveError(err)
+				break
+			}
+			v.SetBytes(b[:n])
+		case reflect.String:
+			if v.Type() == numberType && !isValidNumber(string(s)) {
+				return fmt.Errorf("json: invalid number literal, trying to unmarshal %q into Number", item)
+			}
+			v.SetString(string(s))
+		case reflect.Interface:
+			if v.NumMethod() == 0 {
+				v.Set(reflect.ValueOf(string(s)))
+			} else {
+				d.saveError(&UnmarshalTypeError{Value: "string", Type: v.Type(), Offset: int64(d.readIndex())})
+			}
+		}
+
+	default: // number
+		if c != '-' && (c < '0' || c > '9') {
+			if fromQuoted {
+				return fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type())
+			}
+			panic(phasePanicMsg)
+		}
+		s := string(item)
+		switch v.Kind() {
+		default:
+			if v.Kind() == reflect.String && v.Type() == numberType {
+				// s must be a valid number, because it's
+				// already been tokenized.
+				v.SetString(s)
+				break
+			}
+			if fromQuoted {
+				return fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type())
+			}
+			d.saveError(&UnmarshalTypeError{Value: "number", Type: v.Type(), Offset: int64(d.readIndex())})
+		case reflect.Interface:
+			n, err := d.convertNumber(s)
+			if err != nil {
+				d.saveError(err)
+				break
+			}
+			if v.NumMethod() != 0 {
+				d.saveError(&UnmarshalTypeError{Value: "number", Type: v.Type(), Offset: int64(d.readIndex())})
+				break
+			}
+			v.Set(reflect.ValueOf(n))
+
+		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+			n, err := strconv.ParseInt(s, 10, 64)
+			if err != nil || v.OverflowInt(n) {
+				d.saveError(&UnmarshalTypeError{Value: "number " + s, Type: v.Type(), Offset: int64(d.readIndex())})
+				break
+			}
+			v.SetInt(n)
+
+		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+			n, err := strconv.ParseUint(s, 10, 64)
+			if err != nil || v.OverflowUint(n) {
+				d.saveError(&UnmarshalTypeError{Value: "number " + s, Type: v.Type(), Offset: int64(d.readIndex())})
+				break
+			}
+			v.SetUint(n)
+
+		case reflect.Float32, reflect.Float64:
+			n, err := strconv.ParseFloat(s, v.Type().Bits())
+			if err != nil || v.OverflowFloat(n) {
+				d.saveError(&UnmarshalTypeError{Value: "number " + s, Type: v.Type(), Offset: int64(d.readIndex())})
+				break
+			}
+			v.SetFloat(n)
+		}
+	}
+	return nil
+}
+
+// The xxxInterface routines build up a value to be stored
+// in an empty interface. They are not strictly necessary,
+// but they avoid the weight of reflection in this common case.
+
+// valueInterface is like value but returns interface{}
+func (d *decodeState) valueInterface() (val any) {
+	switch d.opcode {
+	default:
+		panic(phasePanicMsg)
+	case scanBeginArray:
+		val = d.arrayInterface()
+		d.scanNext()
+	case scanBeginObject:
+		val = d.objectInterface()
+		d.scanNext()
+	case scanBeginLiteral:
+		val = d.literalInterface()
+	}
+	return
+}
+
+// arrayInterface is like array but returns []interface{}.
+func (d *decodeState) arrayInterface() []any {
+	var v = make([]any, 0)
+	for {
+		// Look ahead for ] - can only happen on first iteration.
+		d.scanWhile(scanSkipSpace)
+		if d.opcode == scanEndArray {
+			break
+		}
+
+		v = append(v, d.valueInterface())
+
+		// Next token must be , or ].
+		if d.opcode == scanSkipSpace {
+			d.scanWhile(scanSkipSpace)
+		}
+		if d.opcode == scanEndArray {
+			break
+		}
+		if d.opcode != scanArrayValue {
+			panic(phasePanicMsg)
+		}
+	}
+	return v
+}
+
+// objectInterface is like object but returns map[string]interface{}.
+func (d *decodeState) objectInterface() map[string]any {
+	m := make(map[string]any)
+	for {
+		// Read opening " of string key or closing }.
+		d.scanWhile(scanSkipSpace)
+		if d.opcode == scanEndObject {
+			// closing } - can only happen on first iteration.
+			break
+		}
+		if d.opcode != scanBeginLiteral {
+			panic(phasePanicMsg)
+		}
+
+		// Read string key.
+		start := d.readIndex()
+		d.rescanLiteral()
+		item := d.data[start:d.readIndex()]
+		key, ok := unquote(item)
+		if !ok {
+			panic(phasePanicMsg)
+		}
+
+		// Read : before value.
+		if d.opcode == scanSkipSpace {
+			d.scanWhile(scanSkipSpace)
+		}
+		if d.opcode != scanObjectKey {
+			panic(phasePanicMsg)
+		}
+		d.scanWhile(scanSkipSpace)
+
+		// Read value.
+		m[key] = d.valueInterface()
+
+		// Next token must be , or }.
+		if d.opcode == scanSkipSpace {
+			d.scanWhile(scanSkipSpace)
+		}
+		if d.opcode == scanEndObject {
+			break
+		}
+		if d.opcode != scanObjectValue {
+			panic(phasePanicMsg)
+		}
+	}
+	return m
+}
+
+// literalInterface consumes and returns a literal from d.data[d.off-1:] and
+// it reads the following byte ahead. The first byte of the literal has been
+// read already (that's how the caller knows it's a literal).
+func (d *decodeState) literalInterface() any {
+	// All bytes inside literal return scanContinue op code.
+	start := d.readIndex()
+	d.rescanLiteral()
+
+	item := d.data[start:d.readIndex()]
+
+	switch c := item[0]; c {
+	case 'n': // null
+		return nil
+
+	case 't', 'f': // true, false
+		return c == 't'
+
+	case '"': // string
+		s, ok := unquote(item)
+		if !ok {
+			panic(phasePanicMsg)
+		}
+		return s
+
+	default: // number
+		if c != '-' && (c < '0' || c > '9') {
+			panic(phasePanicMsg)
+		}
+		n, err := d.convertNumber(string(item))
+		if err != nil {
+			d.saveError(err)
+		}
+		return n
+	}
+}
+
+// getu4 decodes \uXXXX from the beginning of s, returning the hex value,
+// or it returns -1.
+func getu4(s []byte) rune {
+	if len(s) < 6 || s[0] != '\\' || s[1] != 'u' {
+		return -1
+	}
+	var r rune
+	for _, c := range s[2:6] {
+		switch {
+		case '0' <= c && c <= '9':
+			c = c - '0'
+		case 'a' <= c && c <= 'f':
+			c = c - 'a' + 10
+		case 'A' <= c && c <= 'F':
+			c = c - 'A' + 10
+		default:
+			return -1
+		}
+		r = r*16 + rune(c)
+	}
+	return r
+}
+
+// unquote converts a quoted JSON string literal s into an actual string t.
+// The rules are different than for Go, so cannot use strconv.Unquote.
+func unquote(s []byte) (t string, ok bool) {
+	s, ok = unquoteBytes(s)
+	t = string(s)
+	return
+}
+
+func unquoteBytes(s []byte) (t []byte, ok bool) {
+	if len(s) < 2 || s[0] != '"' || s[len(s)-1] != '"' {
+		return
+	}
+	s = s[1 : len(s)-1]
+
+	// Check for unusual characters. If there are none,
+	// then no unquoting is needed, so return a slice of the
+	// original bytes.
+	r := 0
+	for r < len(s) {
+		c := s[r]
+		if c == '\\' || c == '"' || c < ' ' {
+			break
+		}
+		if c < utf8.RuneSelf {
+			r++
+			continue
+		}
+		rr, size := utf8.DecodeRune(s[r:])
+		if rr == utf8.RuneError && size == 1 {
+			break
+		}
+		r += size
+	}
+	if r == len(s) {
+		return s, true
+	}
+
+	b := make([]byte, len(s)+2*utf8.UTFMax)
+	w := copy(b, s[0:r])
+	for r < len(s) {
+		// Out of room? Can only happen if s is full of
+		// malformed UTF-8 and we're replacing each
+		// byte with RuneError.
+		if w >= len(b)-2*utf8.UTFMax {
+			nb := make([]byte, (len(b)+utf8.UTFMax)*2)
+			copy(nb, b[0:w])
+			b = nb
+		}
+		switch c := s[r]; {
+		case c == '\\':
+			r++
+			if r >= len(s) {
+				return
+			}
+			switch s[r] {
+			default:
+				return
+			case '"', '\\', '/', '\'':
+				b[w] = s[r]
+				r++
+				w++
+			case 'b':
+				b[w] = '\b'
+				r++
+				w++
+			case 'f':
+				b[w] = '\f'
+				r++
+				w++
+			case 'n':
+				b[w] = '\n'
+				r++
+				w++
+			case 'r':
+				b[w] = '\r'
+				r++
+				w++
+			case 't':
+				b[w] = '\t'
+				r++
+				w++
+			case 'u':
+				r--
+				rr := getu4(s[r:])
+				if rr < 0 {
+					return
+				}
+				r += 6
+				if utf16.IsSurrogate(rr) {
+					rr1 := getu4(s[r:])
+					if dec := utf16.DecodeRune(rr, rr1); dec != unicode.ReplacementChar {
+						// A valid pair; consume.
+						r += 6
+						w += utf8.EncodeRune(b[w:], dec)
+						break
+					}
+					// Invalid surrogate; fall back to replacement rune.
+					rr = unicode.ReplacementChar
+				}
+				w += utf8.EncodeRune(b[w:], rr)
+			}
+
+		// Quote, control characters are invalid.
+		case c == '"', c < ' ':
+			return
+
+		// ASCII
+		case c < utf8.RuneSelf:
+			b[w] = c
+			r++
+			w++
+
+		// Coerce to well-formed UTF-8.
+		default:
+			rr, size := utf8.DecodeRune(s[r:])
+			r += size
+			w += utf8.EncodeRune(b[w:], rr)
+		}
+	}
+	return b[0:w], true
+}
diff --git a/src/encoding/json/decode_test.go b/src/encoding/json/decode_test.go
new file mode 100644
index 0000000..c2c036b
--- /dev/null
+++ b/src/encoding/json/decode_test.go
@@ -0,0 +1,2574 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json
+
+import (
+	"bytes"
+	"encoding"
+	"errors"
+	"fmt"
+	"image"
+	"math"
+	"math/big"
+	"net"
+	"reflect"
+	"strconv"
+	"strings"
+	"testing"
+	"time"
+)
+
+type T struct {
+	X string
+	Y int
+	Z int `json:"-"`
+}
+
+type U struct {
+	Alphabet string `json:"alpha"`
+}
+
+type V struct {
+	F1 any
+	F2 int32
+	F3 Number
+	F4 *VOuter
+}
+
+type VOuter struct {
+	V V
+}
+
+type W struct {
+	S SS
+}
+
+type P struct {
+	PP PP
+}
+
+type PP struct {
+	T  T
+	Ts []T
+}
+
+type SS string
+
+func (*SS) UnmarshalJSON(data []byte) error {
+	return &UnmarshalTypeError{Value: "number", Type: reflect.TypeOf(SS(""))}
+}
+
+// ifaceNumAsFloat64/ifaceNumAsNumber are used to test unmarshaling with and
+// without UseNumber
+var ifaceNumAsFloat64 = map[string]any{
+	"k1": float64(1),
+	"k2": "s",
+	"k3": []any{float64(1), float64(2.0), float64(3e-3)},
+	"k4": map[string]any{"kk1": "s", "kk2": float64(2)},
+}
+
+var ifaceNumAsNumber = map[string]any{
+	"k1": Number("1"),
+	"k2": "s",
+	"k3": []any{Number("1"), Number("2.0"), Number("3e-3")},
+	"k4": map[string]any{"kk1": "s", "kk2": Number("2")},
+}
+
+type tx struct {
+	x int
+}
+
+type u8 uint8
+
+// A type that can unmarshal itself.
+
+type unmarshaler struct {
+	T bool
+}
+
+func (u *unmarshaler) UnmarshalJSON(b []byte) error {
+	*u = unmarshaler{true} // All we need to see that UnmarshalJSON is called.
+	return nil
+}
+
+type ustruct struct {
+	M unmarshaler
+}
+
+type unmarshalerText struct {
+	A, B string
+}
+
+// needed for re-marshaling tests
+func (u unmarshalerText) MarshalText() ([]byte, error) {
+	return []byte(u.A + ":" + u.B), nil
+}
+
+func (u *unmarshalerText) UnmarshalText(b []byte) error {
+	pos := bytes.IndexByte(b, ':')
+	if pos == -1 {
+		return errors.New("missing separator")
+	}
+	u.A, u.B = string(b[:pos]), string(b[pos+1:])
+	return nil
+}
+
+var _ encoding.TextUnmarshaler = (*unmarshalerText)(nil)
+
+type ustructText struct {
+	M unmarshalerText
+}
+
+// u8marshal is an integer type that can marshal/unmarshal itself.
+type u8marshal uint8
+
+func (u8 u8marshal) MarshalText() ([]byte, error) {
+	return []byte(fmt.Sprintf("u%d", u8)), nil
+}
+
+var errMissingU8Prefix = errors.New("missing 'u' prefix")
+
+func (u8 *u8marshal) UnmarshalText(b []byte) error {
+	if !bytes.HasPrefix(b, []byte{'u'}) {
+		return errMissingU8Prefix
+	}
+	n, err := strconv.Atoi(string(b[1:]))
+	if err != nil {
+		return err
+	}
+	*u8 = u8marshal(n)
+	return nil
+}
+
+var _ encoding.TextUnmarshaler = (*u8marshal)(nil)
+
+var (
+	umtrue   = unmarshaler{true}
+	umslice  = []unmarshaler{{true}}
+	umstruct = ustruct{unmarshaler{true}}
+
+	umtrueXY   = unmarshalerText{"x", "y"}
+	umsliceXY  = []unmarshalerText{{"x", "y"}}
+	umstructXY = ustructText{unmarshalerText{"x", "y"}}
+
+	ummapXY = map[unmarshalerText]bool{{"x", "y"}: true}
+)
+
+// Test data structures for anonymous fields.
+
+type Point struct {
+	Z int
+}
+
+type Top struct {
+	Level0 int
+	Embed0
+	*Embed0a
+	*Embed0b `json:"e,omitempty"` // treated as named
+	Embed0c  `json:"-"`           // ignored
+	Loop
+	Embed0p // has Point with X, Y, used
+	Embed0q // has Point with Z, used
+	embed   // contains exported field
+}
+
+type Embed0 struct {
+	Level1a int // overridden by Embed0a's Level1a with json tag
+	Level1b int // used because Embed0a's Level1b is renamed
+	Level1c int // used because Embed0a's Level1c is ignored
+	Level1d int // annihilated by Embed0a's Level1d
+	Level1e int `json:"x"` // annihilated by Embed0a.Level1e
+}
+
+type Embed0a struct {
+	Level1a int `json:"Level1a,omitempty"`
+	Level1b int `json:"LEVEL1B,omitempty"`
+	Level1c int `json:"-"`
+	Level1d int // annihilated by Embed0's Level1d
+	Level1f int `json:"x"` // annihilated by Embed0's Level1e
+}
+
+type Embed0b Embed0
+
+type Embed0c Embed0
+
+type Embed0p struct {
+	image.Point
+}
+
+type Embed0q struct {
+	Point
+}
+
+type embed struct {
+	Q int
+}
+
+type Loop struct {
+	Loop1 int `json:",omitempty"`
+	Loop2 int `json:",omitempty"`
+	*Loop
+}
+
+// From reflect test:
+// The X in S6 and S7 annihilate, but they also block the X in S8.S9.
+type S5 struct {
+	S6
+	S7
+	S8
+}
+
+type S6 struct {
+	X int
+}
+
+type S7 S6
+
+type S8 struct {
+	S9
+}
+
+type S9 struct {
+	X int
+	Y int
+}
+
+// From reflect test:
+// The X in S11.S6 and S12.S6 annihilate, but they also block the X in S13.S8.S9.
+type S10 struct {
+	S11
+	S12
+	S13
+}
+
+type S11 struct {
+	S6
+}
+
+type S12 struct {
+	S6
+}
+
+type S13 struct {
+	S8
+}
+
+type Ambig struct {
+	// Given "hello", the first match should win.
+	First  int `json:"HELLO"`
+	Second int `json:"Hello"`
+}
+
+type XYZ struct {
+	X any
+	Y any
+	Z any
+}
+
+type unexportedWithMethods struct{}
+
+func (unexportedWithMethods) F() {}
+
+type byteWithMarshalJSON byte
+
+func (b byteWithMarshalJSON) MarshalJSON() ([]byte, error) {
+	return []byte(fmt.Sprintf(`"Z%.2x"`, byte(b))), nil
+}
+
+func (b *byteWithMarshalJSON) UnmarshalJSON(data []byte) error {
+	if len(data) != 5 || data[0] != '"' || data[1] != 'Z' || data[4] != '"' {
+		return fmt.Errorf("bad quoted string")
+	}
+	i, err := strconv.ParseInt(string(data[2:4]), 16, 8)
+	if err != nil {
+		return fmt.Errorf("bad hex")
+	}
+	*b = byteWithMarshalJSON(i)
+	return nil
+}
+
+type byteWithPtrMarshalJSON byte
+
+func (b *byteWithPtrMarshalJSON) MarshalJSON() ([]byte, error) {
+	return byteWithMarshalJSON(*b).MarshalJSON()
+}
+
+func (b *byteWithPtrMarshalJSON) UnmarshalJSON(data []byte) error {
+	return (*byteWithMarshalJSON)(b).UnmarshalJSON(data)
+}
+
+type byteWithMarshalText byte
+
+func (b byteWithMarshalText) MarshalText() ([]byte, error) {
+	return []byte(fmt.Sprintf(`Z%.2x`, byte(b))), nil
+}
+
+func (b *byteWithMarshalText) UnmarshalText(data []byte) error {
+	if len(data) != 3 || data[0] != 'Z' {
+		return fmt.Errorf("bad quoted string")
+	}
+	i, err := strconv.ParseInt(string(data[1:3]), 16, 8)
+	if err != nil {
+		return fmt.Errorf("bad hex")
+	}
+	*b = byteWithMarshalText(i)
+	return nil
+}
+
+type byteWithPtrMarshalText byte
+
+func (b *byteWithPtrMarshalText) MarshalText() ([]byte, error) {
+	return byteWithMarshalText(*b).MarshalText()
+}
+
+func (b *byteWithPtrMarshalText) UnmarshalText(data []byte) error {
+	return (*byteWithMarshalText)(b).UnmarshalText(data)
+}
+
+type intWithMarshalJSON int
+
+func (b intWithMarshalJSON) MarshalJSON() ([]byte, error) {
+	return []byte(fmt.Sprintf(`"Z%.2x"`, int(b))), nil
+}
+
+func (b *intWithMarshalJSON) UnmarshalJSON(data []byte) error {
+	if len(data) != 5 || data[0] != '"' || data[1] != 'Z' || data[4] != '"' {
+		return fmt.Errorf("bad quoted string")
+	}
+	i, err := strconv.ParseInt(string(data[2:4]), 16, 8)
+	if err != nil {
+		return fmt.Errorf("bad hex")
+	}
+	*b = intWithMarshalJSON(i)
+	return nil
+}
+
+type intWithPtrMarshalJSON int
+
+func (b *intWithPtrMarshalJSON) MarshalJSON() ([]byte, error) {
+	return intWithMarshalJSON(*b).MarshalJSON()
+}
+
+func (b *intWithPtrMarshalJSON) UnmarshalJSON(data []byte) error {
+	return (*intWithMarshalJSON)(b).UnmarshalJSON(data)
+}
+
+type intWithMarshalText int
+
+func (b intWithMarshalText) MarshalText() ([]byte, error) {
+	return []byte(fmt.Sprintf(`Z%.2x`, int(b))), nil
+}
+
+func (b *intWithMarshalText) UnmarshalText(data []byte) error {
+	if len(data) != 3 || data[0] != 'Z' {
+		return fmt.Errorf("bad quoted string")
+	}
+	i, err := strconv.ParseInt(string(data[1:3]), 16, 8)
+	if err != nil {
+		return fmt.Errorf("bad hex")
+	}
+	*b = intWithMarshalText(i)
+	return nil
+}
+
+type intWithPtrMarshalText int
+
+func (b *intWithPtrMarshalText) MarshalText() ([]byte, error) {
+	return intWithMarshalText(*b).MarshalText()
+}
+
+func (b *intWithPtrMarshalText) UnmarshalText(data []byte) error {
+	return (*intWithMarshalText)(b).UnmarshalText(data)
+}
+
+type mapStringToStringData struct {
+	Data map[string]string `json:"data"`
+}
+
+type unmarshalTest struct {
+	in                    string
+	ptr                   any // new(type)
+	out                   any
+	err                   error
+	useNumber             bool
+	golden                bool
+	disallowUnknownFields bool
+}
+
+type B struct {
+	B bool `json:",string"`
+}
+
+type DoublePtr struct {
+	I **int
+	J **int
+}
+
+var unmarshalTests = []unmarshalTest{
+	// basic types
+	{in: `true`, ptr: new(bool), out: true},
+	{in: `1`, ptr: new(int), out: 1},
+	{in: `1.2`, ptr: new(float64), out: 1.2},
+	{in: `-5`, ptr: new(int16), out: int16(-5)},
+	{in: `2`, ptr: new(Number), out: Number("2"), useNumber: true},
+	{in: `2`, ptr: new(Number), out: Number("2")},
+	{in: `2`, ptr: new(any), out: float64(2.0)},
+	{in: `2`, ptr: new(any), out: Number("2"), useNumber: true},
+	{in: `"a\u1234"`, ptr: new(string), out: "a\u1234"},
+	{in: `"http:\/\/"`, ptr: new(string), out: "http://"},
+	{in: `"g-clef: \uD834\uDD1E"`, ptr: new(string), out: "g-clef: \U0001D11E"},
+	{in: `"invalid: \uD834x\uDD1E"`, ptr: new(string), out: "invalid: \uFFFDx\uFFFD"},
+	{in: "null", ptr: new(any), out: nil},
+	{in: `{"X": [1,2,3], "Y": 4}`, ptr: new(T), out: T{Y: 4}, err: &UnmarshalTypeError{"array", reflect.TypeOf(""), 7, "T", "X"}},
+	{in: `{"X": 23}`, ptr: new(T), out: T{}, err: &UnmarshalTypeError{"number", reflect.TypeOf(""), 8, "T", "X"}}, {in: `{"x": 1}`, ptr: new(tx), out: tx{}},
+	{in: `{"x": 1}`, ptr: new(tx), out: tx{}},
+	{in: `{"x": 1}`, ptr: new(tx), err: fmt.Errorf("json: unknown field \"x\""), disallowUnknownFields: true},
+	{in: `{"S": 23}`, ptr: new(W), out: W{}, err: &UnmarshalTypeError{"number", reflect.TypeOf(SS("")), 0, "W", "S"}},
+	{in: `{"F1":1,"F2":2,"F3":3}`, ptr: new(V), out: V{F1: float64(1), F2: int32(2), F3: Number("3")}},
+	{in: `{"F1":1,"F2":2,"F3":3}`, ptr: new(V), out: V{F1: Number("1"), F2: int32(2), F3: Number("3")}, useNumber: true},
+	{in: `{"k1":1,"k2":"s","k3":[1,2.0,3e-3],"k4":{"kk1":"s","kk2":2}}`, ptr: new(any), out: ifaceNumAsFloat64},
+	{in: `{"k1":1,"k2":"s","k3":[1,2.0,3e-3],"k4":{"kk1":"s","kk2":2}}`, ptr: new(any), out: ifaceNumAsNumber, useNumber: true},
+
+	// raw values with whitespace
+	{in: "\n true ", ptr: new(bool), out: true},
+	{in: "\t 1 ", ptr: new(int), out: 1},
+	{in: "\r 1.2 ", ptr: new(float64), out: 1.2},
+	{in: "\t -5 \n", ptr: new(int16), out: int16(-5)},
+	{in: "\t \"a\\u1234\" \n", ptr: new(string), out: "a\u1234"},
+
+	// Z has a "-" tag.
+	{in: `{"Y": 1, "Z": 2}`, ptr: new(T), out: T{Y: 1}},
+	{in: `{"Y": 1, "Z": 2}`, ptr: new(T), err: fmt.Errorf("json: unknown field \"Z\""), disallowUnknownFields: true},
+
+	{in: `{"alpha": "abc", "alphabet": "xyz"}`, ptr: new(U), out: U{Alphabet: "abc"}},
+	{in: `{"alpha": "abc", "alphabet": "xyz"}`, ptr: new(U), err: fmt.Errorf("json: unknown field \"alphabet\""), disallowUnknownFields: true},
+	{in: `{"alpha": "abc"}`, ptr: new(U), out: U{Alphabet: "abc"}},
+	{in: `{"alphabet": "xyz"}`, ptr: new(U), out: U{}},
+	{in: `{"alphabet": "xyz"}`, ptr: new(U), err: fmt.Errorf("json: unknown field \"alphabet\""), disallowUnknownFields: true},
+
+	// syntax errors
+	{in: `{"X": "foo", "Y"}`, err: &SyntaxError{"invalid character '}' after object key", 17}},
+	{in: `[1, 2, 3+]`, err: &SyntaxError{"invalid character '+' after array element", 9}},
+	{in: `{"X":12x}`, err: &SyntaxError{"invalid character 'x' after object key:value pair", 8}, useNumber: true},
+	{in: `[2, 3`, err: &SyntaxError{msg: "unexpected end of JSON input", Offset: 5}},
+	{in: `{"F3": -}`, ptr: new(V), out: V{F3: Number("-")}, err: &SyntaxError{msg: "invalid character '}' in numeric literal", Offset: 9}},
+
+	// raw value errors
+	{in: "\x01 42", err: &SyntaxError{"invalid character '\\x01' looking for beginning of value", 1}},
+	{in: " 42 \x01", err: &SyntaxError{"invalid character '\\x01' after top-level value", 5}},
+	{in: "\x01 true", err: &SyntaxError{"invalid character '\\x01' looking for beginning of value", 1}},
+	{in: " false \x01", err: &SyntaxError{"invalid character '\\x01' after top-level value", 8}},
+	{in: "\x01 1.2", err: &SyntaxError{"invalid character '\\x01' looking for beginning of value", 1}},
+	{in: " 3.4 \x01", err: &SyntaxError{"invalid character '\\x01' after top-level value", 6}},
+	{in: "\x01 \"string\"", err: &SyntaxError{"invalid character '\\x01' looking for beginning of value", 1}},
+	{in: " \"string\" \x01", err: &SyntaxError{"invalid character '\\x01' after top-level value", 11}},
+
+	// array tests
+	{in: `[1, 2, 3]`, ptr: new([3]int), out: [3]int{1, 2, 3}},
+	{in: `[1, 2, 3]`, ptr: new([1]int), out: [1]int{1}},
+	{in: `[1, 2, 3]`, ptr: new([5]int), out: [5]int{1, 2, 3, 0, 0}},
+	{in: `[1, 2, 3]`, ptr: new(MustNotUnmarshalJSON), err: errors.New("MustNotUnmarshalJSON was used")},
+
+	// empty array to interface test
+	{in: `[]`, ptr: new([]any), out: []any{}},
+	{in: `null`, ptr: new([]any), out: []any(nil)},
+	{in: `{"T":[]}`, ptr: new(map[string]any), out: map[string]any{"T": []any{}}},
+	{in: `{"T":null}`, ptr: new(map[string]any), out: map[string]any{"T": any(nil)}},
+
+	// composite tests
+	{in: allValueIndent, ptr: new(All), out: allValue},
+	{in: allValueCompact, ptr: new(All), out: allValue},
+	{in: allValueIndent, ptr: new(*All), out: &allValue},
+	{in: allValueCompact, ptr: new(*All), out: &allValue},
+	{in: pallValueIndent, ptr: new(All), out: pallValue},
+	{in: pallValueCompact, ptr: new(All), out: pallValue},
+	{in: pallValueIndent, ptr: new(*All), out: &pallValue},
+	{in: pallValueCompact, ptr: new(*All), out: &pallValue},
+
+	// unmarshal interface test
+	{in: `{"T":false}`, ptr: new(unmarshaler), out: umtrue}, // use "false" so test will fail if custom unmarshaler is not called
+	{in: `{"T":false}`, ptr: new(*unmarshaler), out: &umtrue},
+	{in: `[{"T":false}]`, ptr: new([]unmarshaler), out: umslice},
+	{in: `[{"T":false}]`, ptr: new(*[]unmarshaler), out: &umslice},
+	{in: `{"M":{"T":"x:y"}}`, ptr: new(ustruct), out: umstruct},
+
+	// UnmarshalText interface test
+	{in: `"x:y"`, ptr: new(unmarshalerText), out: umtrueXY},
+	{in: `"x:y"`, ptr: new(*unmarshalerText), out: &umtrueXY},
+	{in: `["x:y"]`, ptr: new([]unmarshalerText), out: umsliceXY},
+	{in: `["x:y"]`, ptr: new(*[]unmarshalerText), out: &umsliceXY},
+	{in: `{"M":"x:y"}`, ptr: new(ustructText), out: umstructXY},
+
+	// integer-keyed map test
+	{
+		in:  `{"-1":"a","0":"b","1":"c"}`,
+		ptr: new(map[int]string),
+		out: map[int]string{-1: "a", 0: "b", 1: "c"},
+	},
+	{
+		in:  `{"0":"a","10":"c","9":"b"}`,
+		ptr: new(map[u8]string),
+		out: map[u8]string{0: "a", 9: "b", 10: "c"},
+	},
+	{
+		in:  `{"-9223372036854775808":"min","9223372036854775807":"max"}`,
+		ptr: new(map[int64]string),
+		out: map[int64]string{math.MinInt64: "min", math.MaxInt64: "max"},
+	},
+	{
+		in:  `{"18446744073709551615":"max"}`,
+		ptr: new(map[uint64]string),
+		out: map[uint64]string{math.MaxUint64: "max"},
+	},
+	{
+		in:  `{"0":false,"10":true}`,
+		ptr: new(map[uintptr]bool),
+		out: map[uintptr]bool{0: false, 10: true},
+	},
+
+	// Check that MarshalText and UnmarshalText take precedence
+	// over default integer handling in map keys.
+	{
+		in:  `{"u2":4}`,
+		ptr: new(map[u8marshal]int),
+		out: map[u8marshal]int{2: 4},
+	},
+	{
+		in:  `{"2":4}`,
+		ptr: new(map[u8marshal]int),
+		err: errMissingU8Prefix,
+	},
+
+	// integer-keyed map errors
+	{
+		in:  `{"abc":"abc"}`,
+		ptr: new(map[int]string),
+		err: &UnmarshalTypeError{Value: "number abc", Type: reflect.TypeOf(0), Offset: 2},
+	},
+	{
+		in:  `{"256":"abc"}`,
+		ptr: new(map[uint8]string),
+		err: &UnmarshalTypeError{Value: "number 256", Type: reflect.TypeOf(uint8(0)), Offset: 2},
+	},
+	{
+		in:  `{"128":"abc"}`,
+		ptr: new(map[int8]string),
+		err: &UnmarshalTypeError{Value: "number 128", Type: reflect.TypeOf(int8(0)), Offset: 2},
+	},
+	{
+		in:  `{"-1":"abc"}`,
+		ptr: new(map[uint8]string),
+		err: &UnmarshalTypeError{Value: "number -1", Type: reflect.TypeOf(uint8(0)), Offset: 2},
+	},
+	{
+		in:  `{"F":{"a":2,"3":4}}`,
+		ptr: new(map[string]map[int]int),
+		err: &UnmarshalTypeError{Value: "number a", Type: reflect.TypeOf(int(0)), Offset: 7},
+	},
+	{
+		in:  `{"F":{"a":2,"3":4}}`,
+		ptr: new(map[string]map[uint]int),
+		err: &UnmarshalTypeError{Value: "number a", Type: reflect.TypeOf(uint(0)), Offset: 7},
+	},
+
+	// Map keys can be encoding.TextUnmarshalers.
+	{in: `{"x:y":true}`, ptr: new(map[unmarshalerText]bool), out: ummapXY},
+	// If multiple values for the same key exists, only the most recent value is used.
+	{in: `{"x:y":false,"x:y":true}`, ptr: new(map[unmarshalerText]bool), out: ummapXY},
+
+	{
+		in: `{
+			"Level0": 1,
+			"Level1b": 2,
+			"Level1c": 3,
+			"x": 4,
+			"Level1a": 5,
+			"LEVEL1B": 6,
+			"e": {
+				"Level1a": 8,
+				"Level1b": 9,
+				"Level1c": 10,
+				"Level1d": 11,
+				"x": 12
+			},
+			"Loop1": 13,
+			"Loop2": 14,
+			"X": 15,
+			"Y": 16,
+			"Z": 17,
+			"Q": 18
+		}`,
+		ptr: new(Top),
+		out: Top{
+			Level0: 1,
+			Embed0: Embed0{
+				Level1b: 2,
+				Level1c: 3,
+			},
+			Embed0a: &Embed0a{
+				Level1a: 5,
+				Level1b: 6,
+			},
+			Embed0b: &Embed0b{
+				Level1a: 8,
+				Level1b: 9,
+				Level1c: 10,
+				Level1d: 11,
+				Level1e: 12,
+			},
+			Loop: Loop{
+				Loop1: 13,
+				Loop2: 14,
+			},
+			Embed0p: Embed0p{
+				Point: image.Point{X: 15, Y: 16},
+			},
+			Embed0q: Embed0q{
+				Point: Point{Z: 17},
+			},
+			embed: embed{
+				Q: 18,
+			},
+		},
+	},
+	{
+		in:  `{"hello": 1}`,
+		ptr: new(Ambig),
+		out: Ambig{First: 1},
+	},
+
+	{
+		in:  `{"X": 1,"Y":2}`,
+		ptr: new(S5),
+		out: S5{S8: S8{S9: S9{Y: 2}}},
+	},
+	{
+		in:                    `{"X": 1,"Y":2}`,
+		ptr:                   new(S5),
+		err:                   fmt.Errorf("json: unknown field \"X\""),
+		disallowUnknownFields: true,
+	},
+	{
+		in:  `{"X": 1,"Y":2}`,
+		ptr: new(S10),
+		out: S10{S13: S13{S8: S8{S9: S9{Y: 2}}}},
+	},
+	{
+		in:                    `{"X": 1,"Y":2}`,
+		ptr:                   new(S10),
+		err:                   fmt.Errorf("json: unknown field \"X\""),
+		disallowUnknownFields: true,
+	},
+	{
+		in:  `{"I": 0, "I": null, "J": null}`,
+		ptr: new(DoublePtr),
+		out: DoublePtr{I: nil, J: nil},
+	},
+
+	// invalid UTF-8 is coerced to valid UTF-8.
+	{
+		in:  "\"hello\xffworld\"",
+		ptr: new(string),
+		out: "hello\ufffdworld",
+	},
+	{
+		in:  "\"hello\xc2\xc2world\"",
+		ptr: new(string),
+		out: "hello\ufffd\ufffdworld",
+	},
+	{
+		in:  "\"hello\xc2\xffworld\"",
+		ptr: new(string),
+		out: "hello\ufffd\ufffdworld",
+	},
+	{
+		in:  "\"hello\\ud800world\"",
+		ptr: new(string),
+		out: "hello\ufffdworld",
+	},
+	{
+		in:  "\"hello\\ud800\\ud800world\"",
+		ptr: new(string),
+		out: "hello\ufffd\ufffdworld",
+	},
+	{
+		in:  "\"hello\\ud800\\ud800world\"",
+		ptr: new(string),
+		out: "hello\ufffd\ufffdworld",
+	},
+	{
+		in:  "\"hello\xed\xa0\x80\xed\xb0\x80world\"",
+		ptr: new(string),
+		out: "hello\ufffd\ufffd\ufffd\ufffd\ufffd\ufffdworld",
+	},
+
+	// Used to be issue 8305, but time.Time implements encoding.TextUnmarshaler so this works now.
+	{
+		in:  `{"2009-11-10T23:00:00Z": "hello world"}`,
+		ptr: new(map[time.Time]string),
+		out: map[time.Time]string{time.Date(2009, 11, 10, 23, 0, 0, 0, time.UTC): "hello world"},
+	},
+
+	// issue 8305
+	{
+		in:  `{"2009-11-10T23:00:00Z": "hello world"}`,
+		ptr: new(map[Point]string),
+		err: &UnmarshalTypeError{Value: "object", Type: reflect.TypeOf(map[Point]string{}), Offset: 1},
+	},
+	{
+		in:  `{"asdf": "hello world"}`,
+		ptr: new(map[unmarshaler]string),
+		err: &UnmarshalTypeError{Value: "object", Type: reflect.TypeOf(map[unmarshaler]string{}), Offset: 1},
+	},
+
+	// related to issue 13783.
+	// Go 1.7 changed marshaling a slice of typed byte to use the methods on the byte type,
+	// similar to marshaling a slice of typed int.
+	// These tests check that, assuming the byte type also has valid decoding methods,
+	// either the old base64 string encoding or the new per-element encoding can be
+	// successfully unmarshaled. The custom unmarshalers were accessible in earlier
+	// versions of Go, even though the custom marshaler was not.
+	{
+		in:  `"AQID"`,
+		ptr: new([]byteWithMarshalJSON),
+		out: []byteWithMarshalJSON{1, 2, 3},
+	},
+	{
+		in:     `["Z01","Z02","Z03"]`,
+		ptr:    new([]byteWithMarshalJSON),
+		out:    []byteWithMarshalJSON{1, 2, 3},
+		golden: true,
+	},
+	{
+		in:  `"AQID"`,
+		ptr: new([]byteWithMarshalText),
+		out: []byteWithMarshalText{1, 2, 3},
+	},
+	{
+		in:     `["Z01","Z02","Z03"]`,
+		ptr:    new([]byteWithMarshalText),
+		out:    []byteWithMarshalText{1, 2, 3},
+		golden: true,
+	},
+	{
+		in:  `"AQID"`,
+		ptr: new([]byteWithPtrMarshalJSON),
+		out: []byteWithPtrMarshalJSON{1, 2, 3},
+	},
+	{
+		in:     `["Z01","Z02","Z03"]`,
+		ptr:    new([]byteWithPtrMarshalJSON),
+		out:    []byteWithPtrMarshalJSON{1, 2, 3},
+		golden: true,
+	},
+	{
+		in:  `"AQID"`,
+		ptr: new([]byteWithPtrMarshalText),
+		out: []byteWithPtrMarshalText{1, 2, 3},
+	},
+	{
+		in:     `["Z01","Z02","Z03"]`,
+		ptr:    new([]byteWithPtrMarshalText),
+		out:    []byteWithPtrMarshalText{1, 2, 3},
+		golden: true,
+	},
+
+	// ints work with the marshaler but not the base64 []byte case
+	{
+		in:     `["Z01","Z02","Z03"]`,
+		ptr:    new([]intWithMarshalJSON),
+		out:    []intWithMarshalJSON{1, 2, 3},
+		golden: true,
+	},
+	{
+		in:     `["Z01","Z02","Z03"]`,
+		ptr:    new([]intWithMarshalText),
+		out:    []intWithMarshalText{1, 2, 3},
+		golden: true,
+	},
+	{
+		in:     `["Z01","Z02","Z03"]`,
+		ptr:    new([]intWithPtrMarshalJSON),
+		out:    []intWithPtrMarshalJSON{1, 2, 3},
+		golden: true,
+	},
+	{
+		in:     `["Z01","Z02","Z03"]`,
+		ptr:    new([]intWithPtrMarshalText),
+		out:    []intWithPtrMarshalText{1, 2, 3},
+		golden: true,
+	},
+
+	{in: `0.000001`, ptr: new(float64), out: 0.000001, golden: true},
+	{in: `1e-7`, ptr: new(float64), out: 1e-7, golden: true},
+	{in: `100000000000000000000`, ptr: new(float64), out: 100000000000000000000.0, golden: true},
+	{in: `1e+21`, ptr: new(float64), out: 1e21, golden: true},
+	{in: `-0.000001`, ptr: new(float64), out: -0.000001, golden: true},
+	{in: `-1e-7`, ptr: new(float64), out: -1e-7, golden: true},
+	{in: `-100000000000000000000`, ptr: new(float64), out: -100000000000000000000.0, golden: true},
+	{in: `-1e+21`, ptr: new(float64), out: -1e21, golden: true},
+	{in: `999999999999999900000`, ptr: new(float64), out: 999999999999999900000.0, golden: true},
+	{in: `9007199254740992`, ptr: new(float64), out: 9007199254740992.0, golden: true},
+	{in: `9007199254740993`, ptr: new(float64), out: 9007199254740992.0, golden: false},
+
+	{
+		in:  `{"V": {"F2": "hello"}}`,
+		ptr: new(VOuter),
+		err: &UnmarshalTypeError{
+			Value:  "string",
+			Struct: "V",
+			Field:  "V.F2",
+			Type:   reflect.TypeOf(int32(0)),
+			Offset: 20,
+		},
+	},
+	{
+		in:  `{"V": {"F4": {}, "F2": "hello"}}`,
+		ptr: new(VOuter),
+		err: &UnmarshalTypeError{
+			Value:  "string",
+			Struct: "V",
+			Field:  "V.F2",
+			Type:   reflect.TypeOf(int32(0)),
+			Offset: 30,
+		},
+	},
+
+	// issue 15146.
+	// invalid inputs in wrongStringTests below.
+	{in: `{"B":"true"}`, ptr: new(B), out: B{true}, golden: true},
+	{in: `{"B":"false"}`, ptr: new(B), out: B{false}, golden: true},
+	{in: `{"B": "maybe"}`, ptr: new(B), err: errors.New(`json: invalid use of ,string struct tag, trying to unmarshal "maybe" into bool`)},
+	{in: `{"B": "tru"}`, ptr: new(B), err: errors.New(`json: invalid use of ,string struct tag, trying to unmarshal "tru" into bool`)},
+	{in: `{"B": "False"}`, ptr: new(B), err: errors.New(`json: invalid use of ,string struct tag, trying to unmarshal "False" into bool`)},
+	{in: `{"B": "null"}`, ptr: new(B), out: B{false}},
+	{in: `{"B": "nul"}`, ptr: new(B), err: errors.New(`json: invalid use of ,string struct tag, trying to unmarshal "nul" into bool`)},
+	{in: `{"B": [2, 3]}`, ptr: new(B), err: errors.New(`json: invalid use of ,string struct tag, trying to unmarshal unquoted value into bool`)},
+
+	// additional tests for disallowUnknownFields
+	{
+		in: `{
+			"Level0": 1,
+			"Level1b": 2,
+			"Level1c": 3,
+			"x": 4,
+			"Level1a": 5,
+			"LEVEL1B": 6,
+			"e": {
+				"Level1a": 8,
+				"Level1b": 9,
+				"Level1c": 10,
+				"Level1d": 11,
+				"x": 12
+			},
+			"Loop1": 13,
+			"Loop2": 14,
+			"X": 15,
+			"Y": 16,
+			"Z": 17,
+			"Q": 18,
+			"extra": true
+		}`,
+		ptr:                   new(Top),
+		err:                   fmt.Errorf("json: unknown field \"extra\""),
+		disallowUnknownFields: true,
+	},
+	{
+		in: `{
+			"Level0": 1,
+			"Level1b": 2,
+			"Level1c": 3,
+			"x": 4,
+			"Level1a": 5,
+			"LEVEL1B": 6,
+			"e": {
+				"Level1a": 8,
+				"Level1b": 9,
+				"Level1c": 10,
+				"Level1d": 11,
+				"x": 12,
+				"extra": null
+			},
+			"Loop1": 13,
+			"Loop2": 14,
+			"X": 15,
+			"Y": 16,
+			"Z": 17,
+			"Q": 18
+		}`,
+		ptr:                   new(Top),
+		err:                   fmt.Errorf("json: unknown field \"extra\""),
+		disallowUnknownFields: true,
+	},
+	// issue 26444
+	// UnmarshalTypeError without field & struct values
+	{
+		in:  `{"data":{"test1": "bob", "test2": 123}}`,
+		ptr: new(mapStringToStringData),
+		err: &UnmarshalTypeError{Value: "number", Type: reflect.TypeOf(""), Offset: 37, Struct: "mapStringToStringData", Field: "data"},
+	},
+	{
+		in:  `{"data":{"test1": 123, "test2": "bob"}}`,
+		ptr: new(mapStringToStringData),
+		err: &UnmarshalTypeError{Value: "number", Type: reflect.TypeOf(""), Offset: 21, Struct: "mapStringToStringData", Field: "data"},
+	},
+
+	// trying to decode JSON arrays or objects via TextUnmarshaler
+	{
+		in:  `[1, 2, 3]`,
+		ptr: new(MustNotUnmarshalText),
+		err: &UnmarshalTypeError{Value: "array", Type: reflect.TypeOf(&MustNotUnmarshalText{}), Offset: 1},
+	},
+	{
+		in:  `{"foo": "bar"}`,
+		ptr: new(MustNotUnmarshalText),
+		err: &UnmarshalTypeError{Value: "object", Type: reflect.TypeOf(&MustNotUnmarshalText{}), Offset: 1},
+	},
+	// #22369
+	{
+		in:  `{"PP": {"T": {"Y": "bad-type"}}}`,
+		ptr: new(P),
+		err: &UnmarshalTypeError{
+			Value:  "string",
+			Struct: "T",
+			Field:  "PP.T.Y",
+			Type:   reflect.TypeOf(int(0)),
+			Offset: 29,
+		},
+	},
+	{
+		in:  `{"Ts": [{"Y": 1}, {"Y": 2}, {"Y": "bad-type"}]}`,
+		ptr: new(PP),
+		err: &UnmarshalTypeError{
+			Value:  "string",
+			Struct: "T",
+			Field:  "Ts.Y",
+			Type:   reflect.TypeOf(int(0)),
+			Offset: 29,
+		},
+	},
+	// #14702
+	{
+		in:  `invalid`,
+		ptr: new(Number),
+		err: &SyntaxError{
+			msg:    "invalid character 'i' looking for beginning of value",
+			Offset: 1,
+		},
+	},
+	{
+		in:  `"invalid"`,
+		ptr: new(Number),
+		err: fmt.Errorf("json: invalid number literal, trying to unmarshal %q into Number", `"invalid"`),
+	},
+	{
+		in:  `{"A":"invalid"}`,
+		ptr: new(struct{ A Number }),
+		err: fmt.Errorf("json: invalid number literal, trying to unmarshal %q into Number", `"invalid"`),
+	},
+	{
+		in: `{"A":"invalid"}`,
+		ptr: new(struct {
+			A Number `json:",string"`
+		}),
+		err: fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into json.Number", `invalid`),
+	},
+	{
+		in:  `{"A":"invalid"}`,
+		ptr: new(map[string]Number),
+		err: fmt.Errorf("json: invalid number literal, trying to unmarshal %q into Number", `"invalid"`),
+	},
+}
+
+func TestMarshal(t *testing.T) {
+	b, err := Marshal(allValue)
+	if err != nil {
+		t.Fatalf("Marshal allValue: %v", err)
+	}
+	if string(b) != allValueCompact {
+		t.Errorf("Marshal allValueCompact")
+		diff(t, b, []byte(allValueCompact))
+		return
+	}
+
+	b, err = Marshal(pallValue)
+	if err != nil {
+		t.Fatalf("Marshal pallValue: %v", err)
+	}
+	if string(b) != pallValueCompact {
+		t.Errorf("Marshal pallValueCompact")
+		diff(t, b, []byte(pallValueCompact))
+		return
+	}
+}
+
+var badUTF8 = []struct {
+	in, out string
+}{
+	{"hello\xffworld", `"hello\ufffdworld"`},
+	{"", `""`},
+	{"\xff", `"\ufffd"`},
+	{"\xff\xff", `"\ufffd\ufffd"`},
+	{"a\xffb", `"a\ufffdb"`},
+	{"\xe6\x97\xa5\xe6\x9c\xac\xff\xaa\x9e", `"日本\ufffd\ufffd\ufffd"`},
+}
+
+func TestMarshalBadUTF8(t *testing.T) {
+	for _, tt := range badUTF8 {
+		b, err := Marshal(tt.in)
+		if string(b) != tt.out || err != nil {
+			t.Errorf("Marshal(%q) = %#q, %v, want %#q, nil", tt.in, b, err, tt.out)
+		}
+	}
+}
+
+func TestMarshalNumberZeroVal(t *testing.T) {
+	var n Number
+	out, err := Marshal(n)
+	if err != nil {
+		t.Fatal(err)
+	}
+	outStr := string(out)
+	if outStr != "0" {
+		t.Fatalf("Invalid zero val for Number: %q", outStr)
+	}
+}
+
+func TestMarshalEmbeds(t *testing.T) {
+	top := &Top{
+		Level0: 1,
+		Embed0: Embed0{
+			Level1b: 2,
+			Level1c: 3,
+		},
+		Embed0a: &Embed0a{
+			Level1a: 5,
+			Level1b: 6,
+		},
+		Embed0b: &Embed0b{
+			Level1a: 8,
+			Level1b: 9,
+			Level1c: 10,
+			Level1d: 11,
+			Level1e: 12,
+		},
+		Loop: Loop{
+			Loop1: 13,
+			Loop2: 14,
+		},
+		Embed0p: Embed0p{
+			Point: image.Point{X: 15, Y: 16},
+		},
+		Embed0q: Embed0q{
+			Point: Point{Z: 17},
+		},
+		embed: embed{
+			Q: 18,
+		},
+	}
+	b, err := Marshal(top)
+	if err != nil {
+		t.Fatal(err)
+	}
+	want := "{\"Level0\":1,\"Level1b\":2,\"Level1c\":3,\"Level1a\":5,\"LEVEL1B\":6,\"e\":{\"Level1a\":8,\"Level1b\":9,\"Level1c\":10,\"Level1d\":11,\"x\":12},\"Loop1\":13,\"Loop2\":14,\"X\":15,\"Y\":16,\"Z\":17,\"Q\":18}"
+	if string(b) != want {
+		t.Errorf("Wrong marshal result.\n got: %q\nwant: %q", b, want)
+	}
+}
+
+func equalError(a, b error) bool {
+	if a == nil {
+		return b == nil
+	}
+	if b == nil {
+		return a == nil
+	}
+	return a.Error() == b.Error()
+}
+
+func TestUnmarshal(t *testing.T) {
+	for i, tt := range unmarshalTests {
+		var scan scanner
+		in := []byte(tt.in)
+		if err := checkValid(in, &scan); err != nil {
+			if !equalError(err, tt.err) {
+				t.Errorf("#%d: checkValid: %#v", i, err)
+				continue
+			}
+		}
+		if tt.ptr == nil {
+			continue
+		}
+
+		typ := reflect.TypeOf(tt.ptr)
+		if typ.Kind() != reflect.Pointer {
+			t.Errorf("#%d: unmarshalTest.ptr %T is not a pointer type", i, tt.ptr)
+			continue
+		}
+		typ = typ.Elem()
+
+		// v = new(right-type)
+		v := reflect.New(typ)
+
+		if !reflect.DeepEqual(tt.ptr, v.Interface()) {
+			// There's no reason for ptr to point to non-zero data,
+			// as we decode into new(right-type), so the data is
+			// discarded.
+			// This can easily mean tests that silently don't test
+			// what they should. To test decoding into existing
+			// data, see TestPrefilled.
+			t.Errorf("#%d: unmarshalTest.ptr %#v is not a pointer to a zero value", i, tt.ptr)
+			continue
+		}
+
+		dec := NewDecoder(bytes.NewReader(in))
+		if tt.useNumber {
+			dec.UseNumber()
+		}
+		if tt.disallowUnknownFields {
+			dec.DisallowUnknownFields()
+		}
+		if err := dec.Decode(v.Interface()); !equalError(err, tt.err) {
+			t.Errorf("#%d: %v, want %v", i, err, tt.err)
+			continue
+		} else if err != nil {
+			continue
+		}
+		if !reflect.DeepEqual(v.Elem().Interface(), tt.out) {
+			t.Errorf("#%d: mismatch\nhave: %#+v\nwant: %#+v", i, v.Elem().Interface(), tt.out)
+			data, _ := Marshal(v.Elem().Interface())
+			println(string(data))
+			data, _ = Marshal(tt.out)
+			println(string(data))
+			continue
+		}
+
+		// Check round trip also decodes correctly.
+		if tt.err == nil {
+			enc, err := Marshal(v.Interface())
+			if err != nil {
+				t.Errorf("#%d: error re-marshaling: %v", i, err)
+				continue
+			}
+			if tt.golden && !bytes.Equal(enc, in) {
+				t.Errorf("#%d: remarshal mismatch:\nhave: %s\nwant: %s", i, enc, in)
+			}
+			vv := reflect.New(reflect.TypeOf(tt.ptr).Elem())
+			dec = NewDecoder(bytes.NewReader(enc))
+			if tt.useNumber {
+				dec.UseNumber()
+			}
+			if err := dec.Decode(vv.Interface()); err != nil {
+				t.Errorf("#%d: error re-unmarshaling %#q: %v", i, enc, err)
+				continue
+			}
+			if !reflect.DeepEqual(v.Elem().Interface(), vv.Elem().Interface()) {
+				t.Errorf("#%d: mismatch\nhave: %#+v\nwant: %#+v", i, v.Elem().Interface(), vv.Elem().Interface())
+				t.Errorf("     In: %q", strings.Map(noSpace, string(in)))
+				t.Errorf("Marshal: %q", strings.Map(noSpace, string(enc)))
+				continue
+			}
+		}
+	}
+}
+
+func TestUnmarshalMarshal(t *testing.T) {
+	initBig()
+	var v any
+	if err := Unmarshal(jsonBig, &v); err != nil {
+		t.Fatalf("Unmarshal: %v", err)
+	}
+	b, err := Marshal(v)
+	if err != nil {
+		t.Fatalf("Marshal: %v", err)
+	}
+	if !bytes.Equal(jsonBig, b) {
+		t.Errorf("Marshal jsonBig")
+		diff(t, b, jsonBig)
+		return
+	}
+}
+
+var numberTests = []struct {
+	in       string
+	i        int64
+	intErr   string
+	f        float64
+	floatErr string
+}{
+	{in: "-1.23e1", intErr: "strconv.ParseInt: parsing \"-1.23e1\": invalid syntax", f: -1.23e1},
+	{in: "-12", i: -12, f: -12.0},
+	{in: "1e1000", intErr: "strconv.ParseInt: parsing \"1e1000\": invalid syntax", floatErr: "strconv.ParseFloat: parsing \"1e1000\": value out of range"},
+}
+
+// Independent of Decode, basic coverage of the accessors in Number
+func TestNumberAccessors(t *testing.T) {
+	for _, tt := range numberTests {
+		n := Number(tt.in)
+		if s := n.String(); s != tt.in {
+			t.Errorf("Number(%q).String() is %q", tt.in, s)
+		}
+		if i, err := n.Int64(); err == nil && tt.intErr == "" && i != tt.i {
+			t.Errorf("Number(%q).Int64() is %d", tt.in, i)
+		} else if (err == nil && tt.intErr != "") || (err != nil && err.Error() != tt.intErr) {
+			t.Errorf("Number(%q).Int64() wanted error %q but got: %v", tt.in, tt.intErr, err)
+		}
+		if f, err := n.Float64(); err == nil && tt.floatErr == "" && f != tt.f {
+			t.Errorf("Number(%q).Float64() is %g", tt.in, f)
+		} else if (err == nil && tt.floatErr != "") || (err != nil && err.Error() != tt.floatErr) {
+			t.Errorf("Number(%q).Float64() wanted error %q but got: %v", tt.in, tt.floatErr, err)
+		}
+	}
+}
+
+func TestLargeByteSlice(t *testing.T) {
+	s0 := make([]byte, 2000)
+	for i := range s0 {
+		s0[i] = byte(i)
+	}
+	b, err := Marshal(s0)
+	if err != nil {
+		t.Fatalf("Marshal: %v", err)
+	}
+	var s1 []byte
+	if err := Unmarshal(b, &s1); err != nil {
+		t.Fatalf("Unmarshal: %v", err)
+	}
+	if !bytes.Equal(s0, s1) {
+		t.Errorf("Marshal large byte slice")
+		diff(t, s0, s1)
+	}
+}
+
+type Xint struct {
+	X int
+}
+
+func TestUnmarshalInterface(t *testing.T) {
+	var xint Xint
+	var i any = &xint
+	if err := Unmarshal([]byte(`{"X":1}`), &i); err != nil {
+		t.Fatalf("Unmarshal: %v", err)
+	}
+	if xint.X != 1 {
+		t.Fatalf("Did not write to xint")
+	}
+}
+
+func TestUnmarshalPtrPtr(t *testing.T) {
+	var xint Xint
+	pxint := &xint
+	if err := Unmarshal([]byte(`{"X":1}`), &pxint); err != nil {
+		t.Fatalf("Unmarshal: %v", err)
+	}
+	if xint.X != 1 {
+		t.Fatalf("Did not write to xint")
+	}
+}
+
+func TestEscape(t *testing.T) {
+	const input = `"foobar"<html>` + " [\u2028 \u2029]"
+	const expected = `"\"foobar\"\u003chtml\u003e [\u2028 \u2029]"`
+	b, err := Marshal(input)
+	if err != nil {
+		t.Fatalf("Marshal error: %v", err)
+	}
+	if s := string(b); s != expected {
+		t.Errorf("Encoding of [%s]:\n got [%s]\nwant [%s]", input, s, expected)
+	}
+}
+
+// WrongString is a struct that's misusing the ,string modifier.
+type WrongString struct {
+	Message string `json:"result,string"`
+}
+
+type wrongStringTest struct {
+	in, err string
+}
+
+var wrongStringTests = []wrongStringTest{
+	{`{"result":"x"}`, `json: invalid use of ,string struct tag, trying to unmarshal "x" into string`},
+	{`{"result":"foo"}`, `json: invalid use of ,string struct tag, trying to unmarshal "foo" into string`},
+	{`{"result":"123"}`, `json: invalid use of ,string struct tag, trying to unmarshal "123" into string`},
+	{`{"result":123}`, `json: invalid use of ,string struct tag, trying to unmarshal unquoted value into string`},
+	{`{"result":"\""}`, `json: invalid use of ,string struct tag, trying to unmarshal "\"" into string`},
+	{`{"result":"\"foo"}`, `json: invalid use of ,string struct tag, trying to unmarshal "\"foo" into string`},
+}
+
+// If people misuse the ,string modifier, the error message should be
+// helpful, telling the user that they're doing it wrong.
+func TestErrorMessageFromMisusedString(t *testing.T) {
+	for n, tt := range wrongStringTests {
+		r := strings.NewReader(tt.in)
+		var s WrongString
+		err := NewDecoder(r).Decode(&s)
+		got := fmt.Sprintf("%v", err)
+		if got != tt.err {
+			t.Errorf("%d. got err = %q, want %q", n, got, tt.err)
+		}
+	}
+}
+
+func noSpace(c rune) rune {
+	if isSpace(byte(c)) { //only used for ascii
+		return -1
+	}
+	return c
+}
+
+type All struct {
+	Bool    bool
+	Int     int
+	Int8    int8
+	Int16   int16
+	Int32   int32
+	Int64   int64
+	Uint    uint
+	Uint8   uint8
+	Uint16  uint16
+	Uint32  uint32
+	Uint64  uint64
+	Uintptr uintptr
+	Float32 float32
+	Float64 float64
+
+	Foo  string `json:"bar"`
+	Foo2 string `json:"bar2,dummyopt"`
+
+	IntStr     int64   `json:",string"`
+	UintptrStr uintptr `json:",string"`
+
+	PBool    *bool
+	PInt     *int
+	PInt8    *int8
+	PInt16   *int16
+	PInt32   *int32
+	PInt64   *int64
+	PUint    *uint
+	PUint8   *uint8
+	PUint16  *uint16
+	PUint32  *uint32
+	PUint64  *uint64
+	PUintptr *uintptr
+	PFloat32 *float32
+	PFloat64 *float64
+
+	String  string
+	PString *string
+
+	Map   map[string]Small
+	MapP  map[string]*Small
+	PMap  *map[string]Small
+	PMapP *map[string]*Small
+
+	EmptyMap map[string]Small
+	NilMap   map[string]Small
+
+	Slice   []Small
+	SliceP  []*Small
+	PSlice  *[]Small
+	PSliceP *[]*Small
+
+	EmptySlice []Small
+	NilSlice   []Small
+
+	StringSlice []string
+	ByteSlice   []byte
+
+	Small   Small
+	PSmall  *Small
+	PPSmall **Small
+
+	Interface  any
+	PInterface *any
+
+	unexported int
+}
+
+type Small struct {
+	Tag string
+}
+
+var allValue = All{
+	Bool:       true,
+	Int:        2,
+	Int8:       3,
+	Int16:      4,
+	Int32:      5,
+	Int64:      6,
+	Uint:       7,
+	Uint8:      8,
+	Uint16:     9,
+	Uint32:     10,
+	Uint64:     11,
+	Uintptr:    12,
+	Float32:    14.1,
+	Float64:    15.1,
+	Foo:        "foo",
+	Foo2:       "foo2",
+	IntStr:     42,
+	UintptrStr: 44,
+	String:     "16",
+	Map: map[string]Small{
+		"17": {Tag: "tag17"},
+		"18": {Tag: "tag18"},
+	},
+	MapP: map[string]*Small{
+		"19": {Tag: "tag19"},
+		"20": nil,
+	},
+	EmptyMap:    map[string]Small{},
+	Slice:       []Small{{Tag: "tag20"}, {Tag: "tag21"}},
+	SliceP:      []*Small{{Tag: "tag22"}, nil, {Tag: "tag23"}},
+	EmptySlice:  []Small{},
+	StringSlice: []string{"str24", "str25", "str26"},
+	ByteSlice:   []byte{27, 28, 29},
+	Small:       Small{Tag: "tag30"},
+	PSmall:      &Small{Tag: "tag31"},
+	Interface:   5.2,
+}
+
+var pallValue = All{
+	PBool:      &allValue.Bool,
+	PInt:       &allValue.Int,
+	PInt8:      &allValue.Int8,
+	PInt16:     &allValue.Int16,
+	PInt32:     &allValue.Int32,
+	PInt64:     &allValue.Int64,
+	PUint:      &allValue.Uint,
+	PUint8:     &allValue.Uint8,
+	PUint16:    &allValue.Uint16,
+	PUint32:    &allValue.Uint32,
+	PUint64:    &allValue.Uint64,
+	PUintptr:   &allValue.Uintptr,
+	PFloat32:   &allValue.Float32,
+	PFloat64:   &allValue.Float64,
+	PString:    &allValue.String,
+	PMap:       &allValue.Map,
+	PMapP:      &allValue.MapP,
+	PSlice:     &allValue.Slice,
+	PSliceP:    &allValue.SliceP,
+	PPSmall:    &allValue.PSmall,
+	PInterface: &allValue.Interface,
+}
+
+var allValueIndent = `{
+	"Bool": true,
+	"Int": 2,
+	"Int8": 3,
+	"Int16": 4,
+	"Int32": 5,
+	"Int64": 6,
+	"Uint": 7,
+	"Uint8": 8,
+	"Uint16": 9,
+	"Uint32": 10,
+	"Uint64": 11,
+	"Uintptr": 12,
+	"Float32": 14.1,
+	"Float64": 15.1,
+	"bar": "foo",
+	"bar2": "foo2",
+	"IntStr": "42",
+	"UintptrStr": "44",
+	"PBool": null,
+	"PInt": null,
+	"PInt8": null,
+	"PInt16": null,
+	"PInt32": null,
+	"PInt64": null,
+	"PUint": null,
+	"PUint8": null,
+	"PUint16": null,
+	"PUint32": null,
+	"PUint64": null,
+	"PUintptr": null,
+	"PFloat32": null,
+	"PFloat64": null,
+	"String": "16",
+	"PString": null,
+	"Map": {
+		"17": {
+			"Tag": "tag17"
+		},
+		"18": {
+			"Tag": "tag18"
+		}
+	},
+	"MapP": {
+		"19": {
+			"Tag": "tag19"
+		},
+		"20": null
+	},
+	"PMap": null,
+	"PMapP": null,
+	"EmptyMap": {},
+	"NilMap": null,
+	"Slice": [
+		{
+			"Tag": "tag20"
+		},
+		{
+			"Tag": "tag21"
+		}
+	],
+	"SliceP": [
+		{
+			"Tag": "tag22"
+		},
+		null,
+		{
+			"Tag": "tag23"
+		}
+	],
+	"PSlice": null,
+	"PSliceP": null,
+	"EmptySlice": [],
+	"NilSlice": null,
+	"StringSlice": [
+		"str24",
+		"str25",
+		"str26"
+	],
+	"ByteSlice": "Gxwd",
+	"Small": {
+		"Tag": "tag30"
+	},
+	"PSmall": {
+		"Tag": "tag31"
+	},
+	"PPSmall": null,
+	"Interface": 5.2,
+	"PInterface": null
+}`
+
+var allValueCompact = strings.Map(noSpace, allValueIndent)
+
+var pallValueIndent = `{
+	"Bool": false,
+	"Int": 0,
+	"Int8": 0,
+	"Int16": 0,
+	"Int32": 0,
+	"Int64": 0,
+	"Uint": 0,
+	"Uint8": 0,
+	"Uint16": 0,
+	"Uint32": 0,
+	"Uint64": 0,
+	"Uintptr": 0,
+	"Float32": 0,
+	"Float64": 0,
+	"bar": "",
+	"bar2": "",
+        "IntStr": "0",
+	"UintptrStr": "0",
+	"PBool": true,
+	"PInt": 2,
+	"PInt8": 3,
+	"PInt16": 4,
+	"PInt32": 5,
+	"PInt64": 6,
+	"PUint": 7,
+	"PUint8": 8,
+	"PUint16": 9,
+	"PUint32": 10,
+	"PUint64": 11,
+	"PUintptr": 12,
+	"PFloat32": 14.1,
+	"PFloat64": 15.1,
+	"String": "",
+	"PString": "16",
+	"Map": null,
+	"MapP": null,
+	"PMap": {
+		"17": {
+			"Tag": "tag17"
+		},
+		"18": {
+			"Tag": "tag18"
+		}
+	},
+	"PMapP": {
+		"19": {
+			"Tag": "tag19"
+		},
+		"20": null
+	},
+	"EmptyMap": null,
+	"NilMap": null,
+	"Slice": null,
+	"SliceP": null,
+	"PSlice": [
+		{
+			"Tag": "tag20"
+		},
+		{
+			"Tag": "tag21"
+		}
+	],
+	"PSliceP": [
+		{
+			"Tag": "tag22"
+		},
+		null,
+		{
+			"Tag": "tag23"
+		}
+	],
+	"EmptySlice": null,
+	"NilSlice": null,
+	"StringSlice": null,
+	"ByteSlice": null,
+	"Small": {
+		"Tag": ""
+	},
+	"PSmall": null,
+	"PPSmall": {
+		"Tag": "tag31"
+	},
+	"Interface": null,
+	"PInterface": 5.2
+}`
+
+var pallValueCompact = strings.Map(noSpace, pallValueIndent)
+
+func TestRefUnmarshal(t *testing.T) {
+	type S struct {
+		// Ref is defined in encode_test.go.
+		R0 Ref
+		R1 *Ref
+		R2 RefText
+		R3 *RefText
+	}
+	want := S{
+		R0: 12,
+		R1: new(Ref),
+		R2: 13,
+		R3: new(RefText),
+	}
+	*want.R1 = 12
+	*want.R3 = 13
+
+	var got S
+	if err := Unmarshal([]byte(`{"R0":"ref","R1":"ref","R2":"ref","R3":"ref"}`), &got); err != nil {
+		t.Fatalf("Unmarshal: %v", err)
+	}
+	if !reflect.DeepEqual(got, want) {
+		t.Errorf("got %+v, want %+v", got, want)
+	}
+}
+
+// Test that the empty string doesn't panic decoding when ,string is specified
+// Issue 3450
+func TestEmptyString(t *testing.T) {
+	type T2 struct {
+		Number1 int `json:",string"`
+		Number2 int `json:",string"`
+	}
+	data := `{"Number1":"1", "Number2":""}`
+	dec := NewDecoder(strings.NewReader(data))
+	var t2 T2
+	err := dec.Decode(&t2)
+	if err == nil {
+		t.Fatal("Decode: did not return error")
+	}
+	if t2.Number1 != 1 {
+		t.Fatal("Decode: did not set Number1")
+	}
+}
+
+// Test that a null for ,string is not replaced with the previous quoted string (issue 7046).
+// It should also not be an error (issue 2540, issue 8587).
+func TestNullString(t *testing.T) {
+	type T struct {
+		A int  `json:",string"`
+		B int  `json:",string"`
+		C *int `json:",string"`
+	}
+	data := []byte(`{"A": "1", "B": null, "C": null}`)
+	var s T
+	s.B = 1
+	s.C = new(int)
+	*s.C = 2
+	err := Unmarshal(data, &s)
+	if err != nil {
+		t.Fatalf("Unmarshal: %v", err)
+	}
+	if s.B != 1 || s.C != nil {
+		t.Fatalf("after Unmarshal, s.B=%d, s.C=%p, want 1, nil", s.B, s.C)
+	}
+}
+
+func intp(x int) *int {
+	p := new(int)
+	*p = x
+	return p
+}
+
+func intpp(x *int) **int {
+	pp := new(*int)
+	*pp = x
+	return pp
+}
+
+var interfaceSetTests = []struct {
+	pre  any
+	json string
+	post any
+}{
+	{"foo", `"bar"`, "bar"},
+	{"foo", `2`, 2.0},
+	{"foo", `true`, true},
+	{"foo", `null`, nil},
+
+	{nil, `null`, nil},
+	{new(int), `null`, nil},
+	{(*int)(nil), `null`, nil},
+	{new(*int), `null`, new(*int)},
+	{(**int)(nil), `null`, nil},
+	{intp(1), `null`, nil},
+	{intpp(nil), `null`, intpp(nil)},
+	{intpp(intp(1)), `null`, intpp(nil)},
+}
+
+func TestInterfaceSet(t *testing.T) {
+	for _, tt := range interfaceSetTests {
+		b := struct{ X any }{tt.pre}
+		blob := `{"X":` + tt.json + `}`
+		if err := Unmarshal([]byte(blob), &b); err != nil {
+			t.Errorf("Unmarshal %#q: %v", blob, err)
+			continue
+		}
+		if !reflect.DeepEqual(b.X, tt.post) {
+			t.Errorf("Unmarshal %#q into %#v: X=%#v, want %#v", blob, tt.pre, b.X, tt.post)
+		}
+	}
+}
+
+type NullTest struct {
+	Bool      bool
+	Int       int
+	Int8      int8
+	Int16     int16
+	Int32     int32
+	Int64     int64
+	Uint      uint
+	Uint8     uint8
+	Uint16    uint16
+	Uint32    uint32
+	Uint64    uint64
+	Float32   float32
+	Float64   float64
+	String    string
+	PBool     *bool
+	Map       map[string]string
+	Slice     []string
+	Interface any
+
+	PRaw    *RawMessage
+	PTime   *time.Time
+	PBigInt *big.Int
+	PText   *MustNotUnmarshalText
+	PBuffer *bytes.Buffer // has methods, just not relevant ones
+	PStruct *struct{}
+
+	Raw    RawMessage
+	Time   time.Time
+	BigInt big.Int
+	Text   MustNotUnmarshalText
+	Buffer bytes.Buffer
+	Struct struct{}
+}
+
+// JSON null values should be ignored for primitives and string values instead of resulting in an error.
+// Issue 2540
+func TestUnmarshalNulls(t *testing.T) {
+	// Unmarshal docs:
+	// The JSON null value unmarshals into an interface, map, pointer, or slice
+	// by setting that Go value to nil. Because null is often used in JSON to mean
+	// ``not present,'' unmarshaling a JSON null into any other Go type has no effect
+	// on the value and produces no error.
+
+	jsonData := []byte(`{
+				"Bool"    : null,
+				"Int"     : null,
+				"Int8"    : null,
+				"Int16"   : null,
+				"Int32"   : null,
+				"Int64"   : null,
+				"Uint"    : null,
+				"Uint8"   : null,
+				"Uint16"  : null,
+				"Uint32"  : null,
+				"Uint64"  : null,
+				"Float32" : null,
+				"Float64" : null,
+				"String"  : null,
+				"PBool": null,
+				"Map": null,
+				"Slice": null,
+				"Interface": null,
+				"PRaw": null,
+				"PTime": null,
+				"PBigInt": null,
+				"PText": null,
+				"PBuffer": null,
+				"PStruct": null,
+				"Raw": null,
+				"Time": null,
+				"BigInt": null,
+				"Text": null,
+				"Buffer": null,
+				"Struct": null
+			}`)
+	nulls := NullTest{
+		Bool:      true,
+		Int:       2,
+		Int8:      3,
+		Int16:     4,
+		Int32:     5,
+		Int64:     6,
+		Uint:      7,
+		Uint8:     8,
+		Uint16:    9,
+		Uint32:    10,
+		Uint64:    11,
+		Float32:   12.1,
+		Float64:   13.1,
+		String:    "14",
+		PBool:     new(bool),
+		Map:       map[string]string{},
+		Slice:     []string{},
+		Interface: new(MustNotUnmarshalJSON),
+		PRaw:      new(RawMessage),
+		PTime:     new(time.Time),
+		PBigInt:   new(big.Int),
+		PText:     new(MustNotUnmarshalText),
+		PStruct:   new(struct{}),
+		PBuffer:   new(bytes.Buffer),
+		Raw:       RawMessage("123"),
+		Time:      time.Unix(123456789, 0),
+		BigInt:    *big.NewInt(123),
+	}
+
+	before := nulls.Time.String()
+
+	err := Unmarshal(jsonData, &nulls)
+	if err != nil {
+		t.Errorf("Unmarshal of null values failed: %v", err)
+	}
+	if !nulls.Bool || nulls.Int != 2 || nulls.Int8 != 3 || nulls.Int16 != 4 || nulls.Int32 != 5 || nulls.Int64 != 6 ||
+		nulls.Uint != 7 || nulls.Uint8 != 8 || nulls.Uint16 != 9 || nulls.Uint32 != 10 || nulls.Uint64 != 11 ||
+		nulls.Float32 != 12.1 || nulls.Float64 != 13.1 || nulls.String != "14" {
+		t.Errorf("Unmarshal of null values affected primitives")
+	}
+
+	if nulls.PBool != nil {
+		t.Errorf("Unmarshal of null did not clear nulls.PBool")
+	}
+	if nulls.Map != nil {
+		t.Errorf("Unmarshal of null did not clear nulls.Map")
+	}
+	if nulls.Slice != nil {
+		t.Errorf("Unmarshal of null did not clear nulls.Slice")
+	}
+	if nulls.Interface != nil {
+		t.Errorf("Unmarshal of null did not clear nulls.Interface")
+	}
+	if nulls.PRaw != nil {
+		t.Errorf("Unmarshal of null did not clear nulls.PRaw")
+	}
+	if nulls.PTime != nil {
+		t.Errorf("Unmarshal of null did not clear nulls.PTime")
+	}
+	if nulls.PBigInt != nil {
+		t.Errorf("Unmarshal of null did not clear nulls.PBigInt")
+	}
+	if nulls.PText != nil {
+		t.Errorf("Unmarshal of null did not clear nulls.PText")
+	}
+	if nulls.PBuffer != nil {
+		t.Errorf("Unmarshal of null did not clear nulls.PBuffer")
+	}
+	if nulls.PStruct != nil {
+		t.Errorf("Unmarshal of null did not clear nulls.PStruct")
+	}
+
+	if string(nulls.Raw) != "null" {
+		t.Errorf("Unmarshal of RawMessage null did not record null: %v", string(nulls.Raw))
+	}
+	if nulls.Time.String() != before {
+		t.Errorf("Unmarshal of time.Time null set time to %v", nulls.Time.String())
+	}
+	if nulls.BigInt.String() != "123" {
+		t.Errorf("Unmarshal of big.Int null set int to %v", nulls.BigInt.String())
+	}
+}
+
+type MustNotUnmarshalJSON struct{}
+
+func (x MustNotUnmarshalJSON) UnmarshalJSON(data []byte) error {
+	return errors.New("MustNotUnmarshalJSON was used")
+}
+
+type MustNotUnmarshalText struct{}
+
+func (x MustNotUnmarshalText) UnmarshalText(text []byte) error {
+	return errors.New("MustNotUnmarshalText was used")
+}
+
+func TestStringKind(t *testing.T) {
+	type stringKind string
+
+	var m1, m2 map[stringKind]int
+	m1 = map[stringKind]int{
+		"foo": 42,
+	}
+
+	data, err := Marshal(m1)
+	if err != nil {
+		t.Errorf("Unexpected error marshaling: %v", err)
+	}
+
+	err = Unmarshal(data, &m2)
+	if err != nil {
+		t.Errorf("Unexpected error unmarshaling: %v", err)
+	}
+
+	if !reflect.DeepEqual(m1, m2) {
+		t.Error("Items should be equal after encoding and then decoding")
+	}
+}
+
+// Custom types with []byte as underlying type could not be marshaled
+// and then unmarshaled.
+// Issue 8962.
+func TestByteKind(t *testing.T) {
+	type byteKind []byte
+
+	a := byteKind("hello")
+
+	data, err := Marshal(a)
+	if err != nil {
+		t.Error(err)
+	}
+	var b byteKind
+	err = Unmarshal(data, &b)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !reflect.DeepEqual(a, b) {
+		t.Errorf("expected %v == %v", a, b)
+	}
+}
+
+// The fix for issue 8962 introduced a regression.
+// Issue 12921.
+func TestSliceOfCustomByte(t *testing.T) {
+	type Uint8 uint8
+
+	a := []Uint8("hello")
+
+	data, err := Marshal(a)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var b []Uint8
+	err = Unmarshal(data, &b)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !reflect.DeepEqual(a, b) {
+		t.Fatalf("expected %v == %v", a, b)
+	}
+}
+
+var decodeTypeErrorTests = []struct {
+	dest any
+	src  string
+}{
+	{new(string), `{"user": "name"}`}, // issue 4628.
+	{new(error), `{}`},                // issue 4222
+	{new(error), `[]`},
+	{new(error), `""`},
+	{new(error), `123`},
+	{new(error), `true`},
+}
+
+func TestUnmarshalTypeError(t *testing.T) {
+	for _, item := range decodeTypeErrorTests {
+		err := Unmarshal([]byte(item.src), item.dest)
+		if _, ok := err.(*UnmarshalTypeError); !ok {
+			t.Errorf("expected type error for Unmarshal(%q, type %T): got %T",
+				item.src, item.dest, err)
+		}
+	}
+}
+
+var unmarshalSyntaxTests = []string{
+	"tru",
+	"fals",
+	"nul",
+	"123e",
+	`"hello`,
+	`[1,2,3`,
+	`{"key":1`,
+	`{"key":1,`,
+}
+
+func TestUnmarshalSyntax(t *testing.T) {
+	var x any
+	for _, src := range unmarshalSyntaxTests {
+		err := Unmarshal([]byte(src), &x)
+		if _, ok := err.(*SyntaxError); !ok {
+			t.Errorf("expected syntax error for Unmarshal(%q): got %T", src, err)
+		}
+	}
+}
+
+// Test handling of unexported fields that should be ignored.
+// Issue 4660
+type unexportedFields struct {
+	Name string
+	m    map[string]any `json:"-"`
+	m2   map[string]any `json:"abcd"`
+
+	s []int `json:"-"`
+}
+
+func TestUnmarshalUnexported(t *testing.T) {
+	input := `{"Name": "Bob", "m": {"x": 123}, "m2": {"y": 456}, "abcd": {"z": 789}, "s": [2, 3]}`
+	want := &unexportedFields{Name: "Bob"}
+
+	out := &unexportedFields{}
+	err := Unmarshal([]byte(input), out)
+	if err != nil {
+		t.Errorf("got error %v, expected nil", err)
+	}
+	if !reflect.DeepEqual(out, want) {
+		t.Errorf("got %q, want %q", out, want)
+	}
+}
+
+// Time3339 is a time.Time which encodes to and from JSON
+// as an RFC 3339 time in UTC.
+type Time3339 time.Time
+
+func (t *Time3339) UnmarshalJSON(b []byte) error {
+	if len(b) < 2 || b[0] != '"' || b[len(b)-1] != '"' {
+		return fmt.Errorf("types: failed to unmarshal non-string value %q as an RFC 3339 time", b)
+	}
+	tm, err := time.Parse(time.RFC3339, string(b[1:len(b)-1]))
+	if err != nil {
+		return err
+	}
+	*t = Time3339(tm)
+	return nil
+}
+
+func TestUnmarshalJSONLiteralError(t *testing.T) {
+	var t3 Time3339
+	err := Unmarshal([]byte(`"0000-00-00T00:00:00Z"`), &t3)
+	if err == nil {
+		t.Fatalf("expected error; got time %v", time.Time(t3))
+	}
+	if !strings.Contains(err.Error(), "range") {
+		t.Errorf("got err = %v; want out of range error", err)
+	}
+}
+
+// Test that extra object elements in an array do not result in a
+// "data changing underfoot" error.
+// Issue 3717
+func TestSkipArrayObjects(t *testing.T) {
+	json := `[{}]`
+	var dest [0]any
+
+	err := Unmarshal([]byte(json), &dest)
+	if err != nil {
+		t.Errorf("got error %q, want nil", err)
+	}
+}
+
+// Test semantics of pre-filled data, such as struct fields, map elements,
+// slices, and arrays.
+// Issues 4900 and 8837, among others.
+func TestPrefilled(t *testing.T) {
+	// Values here change, cannot reuse table across runs.
+	var prefillTests = []struct {
+		in  string
+		ptr any
+		out any
+	}{
+		{
+			in:  `{"X": 1, "Y": 2}`,
+			ptr: &XYZ{X: float32(3), Y: int16(4), Z: 1.5},
+			out: &XYZ{X: float64(1), Y: float64(2), Z: 1.5},
+		},
+		{
+			in:  `{"X": 1, "Y": 2}`,
+			ptr: &map[string]any{"X": float32(3), "Y": int16(4), "Z": 1.5},
+			out: &map[string]any{"X": float64(1), "Y": float64(2), "Z": 1.5},
+		},
+		{
+			in:  `[2]`,
+			ptr: &[]int{1},
+			out: &[]int{2},
+		},
+		{
+			in:  `[2, 3]`,
+			ptr: &[]int{1},
+			out: &[]int{2, 3},
+		},
+		{
+			in:  `[2, 3]`,
+			ptr: &[...]int{1},
+			out: &[...]int{2},
+		},
+		{
+			in:  `[3]`,
+			ptr: &[...]int{1, 2},
+			out: &[...]int{3, 0},
+		},
+	}
+
+	for _, tt := range prefillTests {
+		ptrstr := fmt.Sprintf("%v", tt.ptr)
+		err := Unmarshal([]byte(tt.in), tt.ptr) // tt.ptr edited here
+		if err != nil {
+			t.Errorf("Unmarshal: %v", err)
+		}
+		if !reflect.DeepEqual(tt.ptr, tt.out) {
+			t.Errorf("Unmarshal(%#q, %s): have %v, want %v", tt.in, ptrstr, tt.ptr, tt.out)
+		}
+	}
+}
+
+var invalidUnmarshalTests = []struct {
+	v    any
+	want string
+}{
+	{nil, "json: Unmarshal(nil)"},
+	{struct{}{}, "json: Unmarshal(non-pointer struct {})"},
+	{(*int)(nil), "json: Unmarshal(nil *int)"},
+}
+
+func TestInvalidUnmarshal(t *testing.T) {
+	buf := []byte(`{"a":"1"}`)
+	for _, tt := range invalidUnmarshalTests {
+		err := Unmarshal(buf, tt.v)
+		if err == nil {
+			t.Errorf("Unmarshal expecting error, got nil")
+			continue
+		}
+		if got := err.Error(); got != tt.want {
+			t.Errorf("Unmarshal = %q; want %q", got, tt.want)
+		}
+	}
+}
+
+var invalidUnmarshalTextTests = []struct {
+	v    any
+	want string
+}{
+	{nil, "json: Unmarshal(nil)"},
+	{struct{}{}, "json: Unmarshal(non-pointer struct {})"},
+	{(*int)(nil), "json: Unmarshal(nil *int)"},
+	{new(net.IP), "json: cannot unmarshal number into Go value of type *net.IP"},
+}
+
+func TestInvalidUnmarshalText(t *testing.T) {
+	buf := []byte(`123`)
+	for _, tt := range invalidUnmarshalTextTests {
+		err := Unmarshal(buf, tt.v)
+		if err == nil {
+			t.Errorf("Unmarshal expecting error, got nil")
+			continue
+		}
+		if got := err.Error(); got != tt.want {
+			t.Errorf("Unmarshal = %q; want %q", got, tt.want)
+		}
+	}
+}
+
+// Test that string option is ignored for invalid types.
+// Issue 9812.
+func TestInvalidStringOption(t *testing.T) {
+	num := 0
+	item := struct {
+		T time.Time         `json:",string"`
+		M map[string]string `json:",string"`
+		S []string          `json:",string"`
+		A [1]string         `json:",string"`
+		I any               `json:",string"`
+		P *int              `json:",string"`
+	}{M: make(map[string]string), S: make([]string, 0), I: num, P: &num}
+
+	data, err := Marshal(item)
+	if err != nil {
+		t.Fatalf("Marshal: %v", err)
+	}
+
+	err = Unmarshal(data, &item)
+	if err != nil {
+		t.Fatalf("Unmarshal: %v", err)
+	}
+}
+
+// Test unmarshal behavior with regards to embedded unexported structs.
+//
+// (Issue 21357) If the embedded struct is a pointer and is unallocated,
+// this returns an error because unmarshal cannot set the field.
+//
+// (Issue 24152) If the embedded struct is given an explicit name,
+// ensure that the normal unmarshal logic does not panic in reflect.
+//
+// (Issue 28145) If the embedded struct is given an explicit name and has
+// exported methods, don't cause a panic trying to get its value.
+func TestUnmarshalEmbeddedUnexported(t *testing.T) {
+	type (
+		embed1 struct{ Q int }
+		embed2 struct{ Q int }
+		embed3 struct {
+			Q int64 `json:",string"`
+		}
+		S1 struct {
+			*embed1
+			R int
+		}
+		S2 struct {
+			*embed1
+			Q int
+		}
+		S3 struct {
+			embed1
+			R int
+		}
+		S4 struct {
+			*embed1
+			embed2
+		}
+		S5 struct {
+			*embed3
+			R int
+		}
+		S6 struct {
+			embed1 `json:"embed1"`
+		}
+		S7 struct {
+			embed1 `json:"embed1"`
+			embed2
+		}
+		S8 struct {
+			embed1 `json:"embed1"`
+			embed2 `json:"embed2"`
+			Q      int
+		}
+		S9 struct {
+			unexportedWithMethods `json:"embed"`
+		}
+	)
+
+	tests := []struct {
+		in  string
+		ptr any
+		out any
+		err error
+	}{{
+		// Error since we cannot set S1.embed1, but still able to set S1.R.
+		in:  `{"R":2,"Q":1}`,
+		ptr: new(S1),
+		out: &S1{R: 2},
+		err: fmt.Errorf("json: cannot set embedded pointer to unexported struct: json.embed1"),
+	}, {
+		// The top level Q field takes precedence.
+		in:  `{"Q":1}`,
+		ptr: new(S2),
+		out: &S2{Q: 1},
+	}, {
+		// No issue with non-pointer variant.
+		in:  `{"R":2,"Q":1}`,
+		ptr: new(S3),
+		out: &S3{embed1: embed1{Q: 1}, R: 2},
+	}, {
+		// No error since both embedded structs have field R, which annihilate each other.
+		// Thus, no attempt is made at setting S4.embed1.
+		in:  `{"R":2}`,
+		ptr: new(S4),
+		out: new(S4),
+	}, {
+		// Error since we cannot set S5.embed1, but still able to set S5.R.
+		in:  `{"R":2,"Q":1}`,
+		ptr: new(S5),
+		out: &S5{R: 2},
+		err: fmt.Errorf("json: cannot set embedded pointer to unexported struct: json.embed3"),
+	}, {
+		// Issue 24152, ensure decodeState.indirect does not panic.
+		in:  `{"embed1": {"Q": 1}}`,
+		ptr: new(S6),
+		out: &S6{embed1{1}},
+	}, {
+		// Issue 24153, check that we can still set forwarded fields even in
+		// the presence of a name conflict.
+		//
+		// This relies on obscure behavior of reflect where it is possible
+		// to set a forwarded exported field on an unexported embedded struct
+		// even though there is a name conflict, even when it would have been
+		// impossible to do so according to Go visibility rules.
+		// Go forbids this because it is ambiguous whether S7.Q refers to
+		// S7.embed1.Q or S7.embed2.Q. Since embed1 and embed2 are unexported,
+		// it should be impossible for an external package to set either Q.
+		//
+		// It is probably okay for a future reflect change to break this.
+		in:  `{"embed1": {"Q": 1}, "Q": 2}`,
+		ptr: new(S7),
+		out: &S7{embed1{1}, embed2{2}},
+	}, {
+		// Issue 24153, similar to the S7 case.
+		in:  `{"embed1": {"Q": 1}, "embed2": {"Q": 2}, "Q": 3}`,
+		ptr: new(S8),
+		out: &S8{embed1{1}, embed2{2}, 3},
+	}, {
+		// Issue 228145, similar to the cases above.
+		in:  `{"embed": {}}`,
+		ptr: new(S9),
+		out: &S9{},
+	}}
+
+	for i, tt := range tests {
+		err := Unmarshal([]byte(tt.in), tt.ptr)
+		if !equalError(err, tt.err) {
+			t.Errorf("#%d: %v, want %v", i, err, tt.err)
+		}
+		if !reflect.DeepEqual(tt.ptr, tt.out) {
+			t.Errorf("#%d: mismatch\ngot:  %#+v\nwant: %#+v", i, tt.ptr, tt.out)
+		}
+	}
+}
+
+func TestUnmarshalErrorAfterMultipleJSON(t *testing.T) {
+	tests := []struct {
+		in  string
+		err error
+	}{{
+		in:  `1 false null :`,
+		err: &SyntaxError{"invalid character ':' looking for beginning of value", 14},
+	}, {
+		in:  `1 [] [,]`,
+		err: &SyntaxError{"invalid character ',' looking for beginning of value", 7},
+	}, {
+		in:  `1 [] [true:]`,
+		err: &SyntaxError{"invalid character ':' after array element", 11},
+	}, {
+		in:  `1  {}    {"x"=}`,
+		err: &SyntaxError{"invalid character '=' after object key", 14},
+	}, {
+		in:  `falsetruenul#`,
+		err: &SyntaxError{"invalid character '#' in literal null (expecting 'l')", 13},
+	}}
+	for i, tt := range tests {
+		dec := NewDecoder(strings.NewReader(tt.in))
+		var err error
+		for {
+			var v any
+			if err = dec.Decode(&v); err != nil {
+				break
+			}
+		}
+		if !reflect.DeepEqual(err, tt.err) {
+			t.Errorf("#%d: got %#v, want %#v", i, err, tt.err)
+		}
+	}
+}
+
+type unmarshalPanic struct{}
+
+func (unmarshalPanic) UnmarshalJSON([]byte) error { panic(0xdead) }
+
+func TestUnmarshalPanic(t *testing.T) {
+	defer func() {
+		if got := recover(); !reflect.DeepEqual(got, 0xdead) {
+			t.Errorf("panic() = (%T)(%v), want 0xdead", got, got)
+		}
+	}()
+	Unmarshal([]byte("{}"), &unmarshalPanic{})
+	t.Fatalf("Unmarshal should have panicked")
+}
+
+// The decoder used to hang if decoding into an interface pointing to its own address.
+// See golang.org/issues/31740.
+func TestUnmarshalRecursivePointer(t *testing.T) {
+	var v any
+	v = &v
+	data := []byte(`{"a": "b"}`)
+
+	if err := Unmarshal(data, v); err != nil {
+		t.Fatal(err)
+	}
+}
+
+type textUnmarshalerString string
+
+func (m *textUnmarshalerString) UnmarshalText(text []byte) error {
+	*m = textUnmarshalerString(strings.ToLower(string(text)))
+	return nil
+}
+
+// Test unmarshal to a map, where the map key is a user defined type.
+// See golang.org/issues/34437.
+func TestUnmarshalMapWithTextUnmarshalerStringKey(t *testing.T) {
+	var p map[textUnmarshalerString]string
+	if err := Unmarshal([]byte(`{"FOO": "1"}`), &p); err != nil {
+		t.Fatalf("Unmarshal unexpected error: %v", err)
+	}
+
+	if _, ok := p["foo"]; !ok {
+		t.Errorf(`Key "foo" does not exist in map: %v`, p)
+	}
+}
+
+func TestUnmarshalRescanLiteralMangledUnquote(t *testing.T) {
+	// See golang.org/issues/38105.
+	var p map[textUnmarshalerString]string
+	if err := Unmarshal([]byte(`{"开源":"12345开源"}`), &p); err != nil {
+		t.Fatalf("Unmarshal unexpected error: %v", err)
+	}
+	if _, ok := p["开源"]; !ok {
+		t.Errorf(`Key "开源" does not exist in map: %v`, p)
+	}
+
+	// See golang.org/issues/38126.
+	type T struct {
+		F1 string `json:"F1,string"`
+	}
+	t1 := T{"aaa\tbbb"}
+
+	b, err := Marshal(t1)
+	if err != nil {
+		t.Fatalf("Marshal unexpected error: %v", err)
+	}
+	var t2 T
+	if err := Unmarshal(b, &t2); err != nil {
+		t.Fatalf("Unmarshal unexpected error: %v", err)
+	}
+	if t1 != t2 {
+		t.Errorf("Marshal and Unmarshal roundtrip mismatch: want %q got %q", t1, t2)
+	}
+
+	// See golang.org/issues/39555.
+	input := map[textUnmarshalerString]string{"FOO": "", `"`: ""}
+
+	encoded, err := Marshal(input)
+	if err != nil {
+		t.Fatalf("Marshal unexpected error: %v", err)
+	}
+	var got map[textUnmarshalerString]string
+	if err := Unmarshal(encoded, &got); err != nil {
+		t.Fatalf("Unmarshal unexpected error: %v", err)
+	}
+	want := map[textUnmarshalerString]string{"foo": "", `"`: ""}
+	if !reflect.DeepEqual(want, got) {
+		t.Fatalf("Unexpected roundtrip result:\nwant: %q\ngot:  %q", want, got)
+	}
+}
+
+func TestUnmarshalMaxDepth(t *testing.T) {
+	testcases := []struct {
+		name        string
+		data        string
+		errMaxDepth bool
+	}{
+		{
+			name:        "ArrayUnderMaxNestingDepth",
+			data:        `{"a":` + strings.Repeat(`[`, 10000-1) + strings.Repeat(`]`, 10000-1) + `}`,
+			errMaxDepth: false,
+		},
+		{
+			name:        "ArrayOverMaxNestingDepth",
+			data:        `{"a":` + strings.Repeat(`[`, 10000) + strings.Repeat(`]`, 10000) + `}`,
+			errMaxDepth: true,
+		},
+		{
+			name:        "ArrayOverStackDepth",
+			data:        `{"a":` + strings.Repeat(`[`, 3000000) + strings.Repeat(`]`, 3000000) + `}`,
+			errMaxDepth: true,
+		},
+		{
+			name:        "ObjectUnderMaxNestingDepth",
+			data:        `{"a":` + strings.Repeat(`{"a":`, 10000-1) + `0` + strings.Repeat(`}`, 10000-1) + `}`,
+			errMaxDepth: false,
+		},
+		{
+			name:        "ObjectOverMaxNestingDepth",
+			data:        `{"a":` + strings.Repeat(`{"a":`, 10000) + `0` + strings.Repeat(`}`, 10000) + `}`,
+			errMaxDepth: true,
+		},
+		{
+			name:        "ObjectOverStackDepth",
+			data:        `{"a":` + strings.Repeat(`{"a":`, 3000000) + `0` + strings.Repeat(`}`, 3000000) + `}`,
+			errMaxDepth: true,
+		},
+	}
+
+	targets := []struct {
+		name     string
+		newValue func() any
+	}{
+		{
+			name: "unstructured",
+			newValue: func() any {
+				var v any
+				return &v
+			},
+		},
+		{
+			name: "typed named field",
+			newValue: func() any {
+				v := struct {
+					A any `json:"a"`
+				}{}
+				return &v
+			},
+		},
+		{
+			name: "typed missing field",
+			newValue: func() any {
+				v := struct {
+					B any `json:"b"`
+				}{}
+				return &v
+			},
+		},
+		{
+			name: "custom unmarshaler",
+			newValue: func() any {
+				v := unmarshaler{}
+				return &v
+			},
+		},
+	}
+
+	for _, tc := range testcases {
+		for _, target := range targets {
+			t.Run(target.name+"-"+tc.name, func(t *testing.T) {
+				err := Unmarshal([]byte(tc.data), target.newValue())
+				if !tc.errMaxDepth {
+					if err != nil {
+						t.Errorf("unexpected error: %v", err)
+					}
+				} else {
+					if err == nil {
+						t.Errorf("expected error containing 'exceeded max depth', got none")
+					} else if !strings.Contains(err.Error(), "exceeded max depth") {
+						t.Errorf("expected error containing 'exceeded max depth', got: %v", err)
+					}
+				}
+			})
+		}
+	}
+}
diff --git a/src/encoding/json/encode.go b/src/encoding/json/encode.go
new file mode 100644
index 0000000..1f5e3e4
--- /dev/null
+++ b/src/encoding/json/encode.go
@@ -0,0 +1,1419 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package json implements encoding and decoding of JSON as defined in
+// RFC 7159. The mapping between JSON and Go values is described
+// in the documentation for the Marshal and Unmarshal functions.
+//
+// See "JSON and Go" for an introduction to this package:
+// https://golang.org/doc/articles/json_and_go.html
+package json
+
+import (
+	"bytes"
+	"encoding"
+	"encoding/base64"
+	"fmt"
+	"math"
+	"reflect"
+	"sort"
+	"strconv"
+	"strings"
+	"sync"
+	"unicode"
+	"unicode/utf8"
+)
+
+// Marshal returns the JSON encoding of v.
+//
+// Marshal traverses the value v recursively.
+// If an encountered value implements the Marshaler interface
+// and is not a nil pointer, Marshal calls its MarshalJSON method
+// to produce JSON. If no MarshalJSON method is present but the
+// value implements encoding.TextMarshaler instead, Marshal calls
+// its MarshalText method and encodes the result as a JSON string.
+// The nil pointer exception is not strictly necessary
+// but mimics a similar, necessary exception in the behavior of
+// UnmarshalJSON.
+//
+// Otherwise, Marshal uses the following type-dependent default encodings:
+//
+// Boolean values encode as JSON booleans.
+//
+// Floating point, integer, and Number values encode as JSON numbers.
+//
+// String values encode as JSON strings coerced to valid UTF-8,
+// replacing invalid bytes with the Unicode replacement rune.
+// So that the JSON will be safe to embed inside HTML <script> tags,
+// the string is encoded using HTMLEscape,
+// which replaces "<", ">", "&", U+2028, and U+2029 are escaped
+// to "\u003c","\u003e", "\u0026", "\u2028", and "\u2029".
+// This replacement can be disabled when using an Encoder,
+// by calling SetEscapeHTML(false).
+//
+// Array and slice values encode as JSON arrays, except that
+// []byte encodes as a base64-encoded string, and a nil slice
+// encodes as the null JSON value.
+//
+// Struct values encode as JSON objects.
+// Each exported struct field becomes a member of the object, using the
+// field name as the object key, unless the field is omitted for one of the
+// reasons given below.
+//
+// The encoding of each struct field can be customized by the format string
+// stored under the "json" key in the struct field's tag.
+// The format string gives the name of the field, possibly followed by a
+// comma-separated list of options. The name may be empty in order to
+// specify options without overriding the default field name.
+//
+// The "omitempty" option specifies that the field should be omitted
+// from the encoding if the field has an empty value, defined as
+// false, 0, a nil pointer, a nil interface value, and any empty array,
+// slice, map, or string.
+//
+// As a special case, if the field tag is "-", the field is always omitted.
+// Note that a field with name "-" can still be generated using the tag "-,".
+//
+// Examples of struct field tags and their meanings:
+//
+//   // Field appears in JSON as key "myName".
+//   Field int `json:"myName"`
+//
+//   // Field appears in JSON as key "myName" and
+//   // the field is omitted from the object if its value is empty,
+//   // as defined above.
+//   Field int `json:"myName,omitempty"`
+//
+//   // Field appears in JSON as key "Field" (the default), but
+//   // the field is skipped if empty.
+//   // Note the leading comma.
+//   Field int `json:",omitempty"`
+//
+//   // Field is ignored by this package.
+//   Field int `json:"-"`
+//
+//   // Field appears in JSON as key "-".
+//   Field int `json:"-,"`
+//
+// The "string" option signals that a field is stored as JSON inside a
+// JSON-encoded string. It applies only to fields of string, floating point,
+// integer, or boolean types. This extra level of encoding is sometimes used
+// when communicating with JavaScript programs:
+//
+//    Int64String int64 `json:",string"`
+//
+// The key name will be used if it's a non-empty string consisting of
+// only Unicode letters, digits, and ASCII punctuation except quotation
+// marks, backslash, and comma.
+//
+// Anonymous struct fields are usually marshaled as if their inner exported fields
+// were fields in the outer struct, subject to the usual Go visibility rules amended
+// as described in the next paragraph.
+// An anonymous struct field with a name given in its JSON tag is treated as
+// having that name, rather than being anonymous.
+// An anonymous struct field of interface type is treated the same as having
+// that type as its name, rather than being anonymous.
+//
+// The Go visibility rules for struct fields are amended for JSON when
+// deciding which field to marshal or unmarshal. If there are
+// multiple fields at the same level, and that level is the least
+// nested (and would therefore be the nesting level selected by the
+// usual Go rules), the following extra rules apply:
+//
+// 1) Of those fields, if any are JSON-tagged, only tagged fields are considered,
+// even if there are multiple untagged fields that would otherwise conflict.
+//
+// 2) If there is exactly one field (tagged or not according to the first rule), that is selected.
+//
+// 3) Otherwise there are multiple fields, and all are ignored; no error occurs.
+//
+// Handling of anonymous struct fields is new in Go 1.1.
+// Prior to Go 1.1, anonymous struct fields were ignored. To force ignoring of
+// an anonymous struct field in both current and earlier versions, give the field
+// a JSON tag of "-".
+//
+// Map values encode as JSON objects. The map's key type must either be a
+// string, an integer type, or implement encoding.TextMarshaler. The map keys
+// are sorted and used as JSON object keys by applying the following rules,
+// subject to the UTF-8 coercion described for string values above:
+//   - keys of any string type are used directly
+//   - encoding.TextMarshalers are marshaled
+//   - integer keys are converted to strings
+//
+// Pointer values encode as the value pointed to.
+// A nil pointer encodes as the null JSON value.
+//
+// Interface values encode as the value contained in the interface.
+// A nil interface value encodes as the null JSON value.
+//
+// Channel, complex, and function values cannot be encoded in JSON.
+// Attempting to encode such a value causes Marshal to return
+// an UnsupportedTypeError.
+//
+// JSON cannot represent cyclic data structures and Marshal does not
+// handle them. Passing cyclic structures to Marshal will result in
+// an error.
+//
+func Marshal(v any) ([]byte, error) {
+	e := newEncodeState()
+
+	err := e.marshal(v, encOpts{escapeHTML: true})
+	if err != nil {
+		return nil, err
+	}
+	buf := append([]byte(nil), e.Bytes()...)
+
+	encodeStatePool.Put(e)
+
+	return buf, nil
+}
+
+// MarshalIndent is like Marshal but applies Indent to format the output.
+// Each JSON element in the output will begin on a new line beginning with prefix
+// followed by one or more copies of indent according to the indentation nesting.
+func MarshalIndent(v any, prefix, indent string) ([]byte, error) {
+	b, err := Marshal(v)
+	if err != nil {
+		return nil, err
+	}
+	var buf bytes.Buffer
+	err = Indent(&buf, b, prefix, indent)
+	if err != nil {
+		return nil, err
+	}
+	return buf.Bytes(), nil
+}
+
+// HTMLEscape appends to dst the JSON-encoded src with <, >, &, U+2028 and U+2029
+// characters inside string literals changed to \u003c, \u003e, \u0026, \u2028, \u2029
+// so that the JSON will be safe to embed inside HTML <script> tags.
+// For historical reasons, web browsers don't honor standard HTML
+// escaping within <script> tags, so an alternative JSON encoding must
+// be used.
+func HTMLEscape(dst *bytes.Buffer, src []byte) {
+	// The characters can only appear in string literals,
+	// so just scan the string one byte at a time.
+	start := 0
+	for i, c := range src {
+		if c == '<' || c == '>' || c == '&' {
+			if start < i {
+				dst.Write(src[start:i])
+			}
+			dst.WriteString(`\u00`)
+			dst.WriteByte(hex[c>>4])
+			dst.WriteByte(hex[c&0xF])
+			start = i + 1
+		}
+		// Convert U+2028 and U+2029 (E2 80 A8 and E2 80 A9).
+		if c == 0xE2 && i+2 < len(src) && src[i+1] == 0x80 && src[i+2]&^1 == 0xA8 {
+			if start < i {
+				dst.Write(src[start:i])
+			}
+			dst.WriteString(`\u202`)
+			dst.WriteByte(hex[src[i+2]&0xF])
+			start = i + 3
+		}
+	}
+	if start < len(src) {
+		dst.Write(src[start:])
+	}
+}
+
+// Marshaler is the interface implemented by types that
+// can marshal themselves into valid JSON.
+type Marshaler interface {
+	MarshalJSON() ([]byte, error)
+}
+
+// An UnsupportedTypeError is returned by Marshal when attempting
+// to encode an unsupported value type.
+type UnsupportedTypeError struct {
+	Type reflect.Type
+}
+
+func (e *UnsupportedTypeError) Error() string {
+	return "json: unsupported type: " + e.Type.String()
+}
+
+// An UnsupportedValueError is returned by Marshal when attempting
+// to encode an unsupported value.
+type UnsupportedValueError struct {
+	Value reflect.Value
+	Str   string
+}
+
+func (e *UnsupportedValueError) Error() string {
+	return "json: unsupported value: " + e.Str
+}
+
+// Before Go 1.2, an InvalidUTF8Error was returned by Marshal when
+// attempting to encode a string value with invalid UTF-8 sequences.
+// As of Go 1.2, Marshal instead coerces the string to valid UTF-8 by
+// replacing invalid bytes with the Unicode replacement rune U+FFFD.
+//
+// Deprecated: No longer used; kept for compatibility.
+type InvalidUTF8Error struct {
+	S string // the whole string value that caused the error
+}
+
+func (e *InvalidUTF8Error) Error() string {
+	return "json: invalid UTF-8 in string: " + strconv.Quote(e.S)
+}
+
+// A MarshalerError represents an error from calling a MarshalJSON or MarshalText method.
+type MarshalerError struct {
+	Type       reflect.Type
+	Err        error
+	sourceFunc string
+}
+
+func (e *MarshalerError) Error() string {
+	srcFunc := e.sourceFunc
+	if srcFunc == "" {
+		srcFunc = "MarshalJSON"
+	}
+	return "json: error calling " + srcFunc +
+		" for type " + e.Type.String() +
+		": " + e.Err.Error()
+}
+
+// Unwrap returns the underlying error.
+func (e *MarshalerError) Unwrap() error { return e.Err }
+
+var hex = "0123456789abcdef"
+
+// An encodeState encodes JSON into a bytes.Buffer.
+type encodeState struct {
+	bytes.Buffer // accumulated output
+	scratch      [64]byte
+
+	// Keep track of what pointers we've seen in the current recursive call
+	// path, to avoid cycles that could lead to a stack overflow. Only do
+	// the relatively expensive map operations if ptrLevel is larger than
+	// startDetectingCyclesAfter, so that we skip the work if we're within a
+	// reasonable amount of nested pointers deep.
+	ptrLevel uint
+	ptrSeen  map[any]struct{}
+}
+
+const startDetectingCyclesAfter = 1000
+
+var encodeStatePool sync.Pool
+
+func newEncodeState() *encodeState {
+	if v := encodeStatePool.Get(); v != nil {
+		e := v.(*encodeState)
+		e.Reset()
+		if len(e.ptrSeen) > 0 {
+			panic("ptrEncoder.encode should have emptied ptrSeen via defers")
+		}
+		e.ptrLevel = 0
+		return e
+	}
+	return &encodeState{ptrSeen: make(map[any]struct{})}
+}
+
+// jsonError is an error wrapper type for internal use only.
+// Panics with errors are wrapped in jsonError so that the top-level recover
+// can distinguish intentional panics from this package.
+type jsonError struct{ error }
+
+func (e *encodeState) marshal(v any, opts encOpts) (err error) {
+	defer func() {
+		if r := recover(); r != nil {
+			if je, ok := r.(jsonError); ok {
+				err = je.error
+			} else {
+				panic(r)
+			}
+		}
+	}()
+	e.reflectValue(reflect.ValueOf(v), opts)
+	return nil
+}
+
+// error aborts the encoding by panicking with err wrapped in jsonError.
+func (e *encodeState) error(err error) {
+	panic(jsonError{err})
+}
+
+func isEmptyValue(v reflect.Value) bool {
+	switch v.Kind() {
+	case reflect.Array, reflect.Map, reflect.Slice, reflect.String:
+		return v.Len() == 0
+	case reflect.Bool:
+		return !v.Bool()
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return v.Int() == 0
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		return v.Uint() == 0
+	case reflect.Float32, reflect.Float64:
+		return v.Float() == 0
+	case reflect.Interface, reflect.Pointer:
+		return v.IsNil()
+	}
+	return false
+}
+
+func (e *encodeState) reflectValue(v reflect.Value, opts encOpts) {
+	valueEncoder(v)(e, v, opts)
+}
+
+type encOpts struct {
+	// quoted causes primitive fields to be encoded inside JSON strings.
+	quoted bool
+	// escapeHTML causes '<', '>', and '&' to be escaped in JSON strings.
+	escapeHTML bool
+}
+
+type encoderFunc func(e *encodeState, v reflect.Value, opts encOpts)
+
+var encoderCache sync.Map // map[reflect.Type]encoderFunc
+
+func valueEncoder(v reflect.Value) encoderFunc {
+	if !v.IsValid() {
+		return invalidValueEncoder
+	}
+	return typeEncoder(v.Type())
+}
+
+func typeEncoder(t reflect.Type) encoderFunc {
+	if fi, ok := encoderCache.Load(t); ok {
+		return fi.(encoderFunc)
+	}
+
+	// To deal with recursive types, populate the map with an
+	// indirect func before we build it. This type waits on the
+	// real func (f) to be ready and then calls it. This indirect
+	// func is only used for recursive types.
+	var (
+		wg sync.WaitGroup
+		f  encoderFunc
+	)
+	wg.Add(1)
+	fi, loaded := encoderCache.LoadOrStore(t, encoderFunc(func(e *encodeState, v reflect.Value, opts encOpts) {
+		wg.Wait()
+		f(e, v, opts)
+	}))
+	if loaded {
+		return fi.(encoderFunc)
+	}
+
+	// Compute the real encoder and replace the indirect func with it.
+	f = newTypeEncoder(t, true)
+	wg.Done()
+	encoderCache.Store(t, f)
+	return f
+}
+
+var (
+	marshalerType     = reflect.TypeOf((*Marshaler)(nil)).Elem()
+	textMarshalerType = reflect.TypeOf((*encoding.TextMarshaler)(nil)).Elem()
+)
+
+// newTypeEncoder constructs an encoderFunc for a type.
+// The returned encoder only checks CanAddr when allowAddr is true.
+func newTypeEncoder(t reflect.Type, allowAddr bool) encoderFunc {
+	// If we have a non-pointer value whose type implements
+	// Marshaler with a value receiver, then we're better off taking
+	// the address of the value - otherwise we end up with an
+	// allocation as we cast the value to an interface.
+	if t.Kind() != reflect.Pointer && allowAddr && reflect.PointerTo(t).Implements(marshalerType) {
+		return newCondAddrEncoder(addrMarshalerEncoder, newTypeEncoder(t, false))
+	}
+	if t.Implements(marshalerType) {
+		return marshalerEncoder
+	}
+	if t.Kind() != reflect.Pointer && allowAddr && reflect.PointerTo(t).Implements(textMarshalerType) {
+		return newCondAddrEncoder(addrTextMarshalerEncoder, newTypeEncoder(t, false))
+	}
+	if t.Implements(textMarshalerType) {
+		return textMarshalerEncoder
+	}
+
+	switch t.Kind() {
+	case reflect.Bool:
+		return boolEncoder
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return intEncoder
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		return uintEncoder
+	case reflect.Float32:
+		return float32Encoder
+	case reflect.Float64:
+		return float64Encoder
+	case reflect.String:
+		return stringEncoder
+	case reflect.Interface:
+		return interfaceEncoder
+	case reflect.Struct:
+		return newStructEncoder(t)
+	case reflect.Map:
+		return newMapEncoder(t)
+	case reflect.Slice:
+		return newSliceEncoder(t)
+	case reflect.Array:
+		return newArrayEncoder(t)
+	case reflect.Pointer:
+		return newPtrEncoder(t)
+	default:
+		return unsupportedTypeEncoder
+	}
+}
+
+func invalidValueEncoder(e *encodeState, v reflect.Value, _ encOpts) {
+	e.WriteString("null")
+}
+
+func marshalerEncoder(e *encodeState, v reflect.Value, opts encOpts) {
+	if v.Kind() == reflect.Pointer && v.IsNil() {
+		e.WriteString("null")
+		return
+	}
+	m, ok := v.Interface().(Marshaler)
+	if !ok {
+		e.WriteString("null")
+		return
+	}
+	b, err := m.MarshalJSON()
+	if err == nil {
+		// copy JSON into buffer, checking validity.
+		err = compact(&e.Buffer, b, opts.escapeHTML)
+	}
+	if err != nil {
+		e.error(&MarshalerError{v.Type(), err, "MarshalJSON"})
+	}
+}
+
+func addrMarshalerEncoder(e *encodeState, v reflect.Value, opts encOpts) {
+	va := v.Addr()
+	if va.IsNil() {
+		e.WriteString("null")
+		return
+	}
+	m := va.Interface().(Marshaler)
+	b, err := m.MarshalJSON()
+	if err == nil {
+		// copy JSON into buffer, checking validity.
+		err = compact(&e.Buffer, b, opts.escapeHTML)
+	}
+	if err != nil {
+		e.error(&MarshalerError{v.Type(), err, "MarshalJSON"})
+	}
+}
+
+func textMarshalerEncoder(e *encodeState, v reflect.Value, opts encOpts) {
+	if v.Kind() == reflect.Pointer && v.IsNil() {
+		e.WriteString("null")
+		return
+	}
+	m, ok := v.Interface().(encoding.TextMarshaler)
+	if !ok {
+		e.WriteString("null")
+		return
+	}
+	b, err := m.MarshalText()
+	if err != nil {
+		e.error(&MarshalerError{v.Type(), err, "MarshalText"})
+	}
+	e.stringBytes(b, opts.escapeHTML)
+}
+
+func addrTextMarshalerEncoder(e *encodeState, v reflect.Value, opts encOpts) {
+	va := v.Addr()
+	if va.IsNil() {
+		e.WriteString("null")
+		return
+	}
+	m := va.Interface().(encoding.TextMarshaler)
+	b, err := m.MarshalText()
+	if err != nil {
+		e.error(&MarshalerError{v.Type(), err, "MarshalText"})
+	}
+	e.stringBytes(b, opts.escapeHTML)
+}
+
+func boolEncoder(e *encodeState, v reflect.Value, opts encOpts) {
+	if opts.quoted {
+		e.WriteByte('"')
+	}
+	if v.Bool() {
+		e.WriteString("true")
+	} else {
+		e.WriteString("false")
+	}
+	if opts.quoted {
+		e.WriteByte('"')
+	}
+}
+
+func intEncoder(e *encodeState, v reflect.Value, opts encOpts) {
+	b := strconv.AppendInt(e.scratch[:0], v.Int(), 10)
+	if opts.quoted {
+		e.WriteByte('"')
+	}
+	e.Write(b)
+	if opts.quoted {
+		e.WriteByte('"')
+	}
+}
+
+func uintEncoder(e *encodeState, v reflect.Value, opts encOpts) {
+	b := strconv.AppendUint(e.scratch[:0], v.Uint(), 10)
+	if opts.quoted {
+		e.WriteByte('"')
+	}
+	e.Write(b)
+	if opts.quoted {
+		e.WriteByte('"')
+	}
+}
+
+type floatEncoder int // number of bits
+
+func (bits floatEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
+	f := v.Float()
+	if math.IsInf(f, 0) || math.IsNaN(f) {
+		e.error(&UnsupportedValueError{v, strconv.FormatFloat(f, 'g', -1, int(bits))})
+	}
+
+	// Convert as if by ES6 number to string conversion.
+	// This matches most other JSON generators.
+	// See golang.org/issue/6384 and golang.org/issue/14135.
+	// Like fmt %g, but the exponent cutoffs are different
+	// and exponents themselves are not padded to two digits.
+	b := e.scratch[:0]
+	abs := math.Abs(f)
+	fmt := byte('f')
+	// Note: Must use float32 comparisons for underlying float32 value to get precise cutoffs right.
+	if abs != 0 {
+		if bits == 64 && (abs < 1e-6 || abs >= 1e21) || bits == 32 && (float32(abs) < 1e-6 || float32(abs) >= 1e21) {
+			fmt = 'e'
+		}
+	}
+	b = strconv.AppendFloat(b, f, fmt, -1, int(bits))
+	if fmt == 'e' {
+		// clean up e-09 to e-9
+		n := len(b)
+		if n >= 4 && b[n-4] == 'e' && b[n-3] == '-' && b[n-2] == '0' {
+			b[n-2] = b[n-1]
+			b = b[:n-1]
+		}
+	}
+
+	if opts.quoted {
+		e.WriteByte('"')
+	}
+	e.Write(b)
+	if opts.quoted {
+		e.WriteByte('"')
+	}
+}
+
+var (
+	float32Encoder = (floatEncoder(32)).encode
+	float64Encoder = (floatEncoder(64)).encode
+)
+
+func stringEncoder(e *encodeState, v reflect.Value, opts encOpts) {
+	if v.Type() == numberType {
+		numStr := v.String()
+		// In Go1.5 the empty string encodes to "0", while this is not a valid number literal
+		// we keep compatibility so check validity after this.
+		if numStr == "" {
+			numStr = "0" // Number's zero-val
+		}
+		if !isValidNumber(numStr) {
+			e.error(fmt.Errorf("json: invalid number literal %q", numStr))
+		}
+		if opts.quoted {
+			e.WriteByte('"')
+		}
+		e.WriteString(numStr)
+		if opts.quoted {
+			e.WriteByte('"')
+		}
+		return
+	}
+	if opts.quoted {
+		e2 := newEncodeState()
+		// Since we encode the string twice, we only need to escape HTML
+		// the first time.
+		e2.string(v.String(), opts.escapeHTML)
+		e.stringBytes(e2.Bytes(), false)
+		encodeStatePool.Put(e2)
+	} else {
+		e.string(v.String(), opts.escapeHTML)
+	}
+}
+
+// isValidNumber reports whether s is a valid JSON number literal.
+func isValidNumber(s string) bool {
+	// This function implements the JSON numbers grammar.
+	// See https://tools.ietf.org/html/rfc7159#section-6
+	// and https://www.json.org/img/number.png
+
+	if s == "" {
+		return false
+	}
+
+	// Optional -
+	if s[0] == '-' {
+		s = s[1:]
+		if s == "" {
+			return false
+		}
+	}
+
+	// Digits
+	switch {
+	default:
+		return false
+
+	case s[0] == '0':
+		s = s[1:]
+
+	case '1' <= s[0] && s[0] <= '9':
+		s = s[1:]
+		for len(s) > 0 && '0' <= s[0] && s[0] <= '9' {
+			s = s[1:]
+		}
+	}
+
+	// . followed by 1 or more digits.
+	if len(s) >= 2 && s[0] == '.' && '0' <= s[1] && s[1] <= '9' {
+		s = s[2:]
+		for len(s) > 0 && '0' <= s[0] && s[0] <= '9' {
+			s = s[1:]
+		}
+	}
+
+	// e or E followed by an optional - or + and
+	// 1 or more digits.
+	if len(s) >= 2 && (s[0] == 'e' || s[0] == 'E') {
+		s = s[1:]
+		if s[0] == '+' || s[0] == '-' {
+			s = s[1:]
+			if s == "" {
+				return false
+			}
+		}
+		for len(s) > 0 && '0' <= s[0] && s[0] <= '9' {
+			s = s[1:]
+		}
+	}
+
+	// Make sure we are at the end.
+	return s == ""
+}
+
+func interfaceEncoder(e *encodeState, v reflect.Value, opts encOpts) {
+	if v.IsNil() {
+		e.WriteString("null")
+		return
+	}
+	e.reflectValue(v.Elem(), opts)
+}
+
+func unsupportedTypeEncoder(e *encodeState, v reflect.Value, _ encOpts) {
+	e.error(&UnsupportedTypeError{v.Type()})
+}
+
+type structEncoder struct {
+	fields structFields
+}
+
+type structFields struct {
+	list      []field
+	nameIndex map[string]int
+}
+
+func (se structEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
+	next := byte('{')
+FieldLoop:
+	for i := range se.fields.list {
+		f := &se.fields.list[i]
+
+		// Find the nested struct field by following f.index.
+		fv := v
+		for _, i := range f.index {
+			if fv.Kind() == reflect.Pointer {
+				if fv.IsNil() {
+					continue FieldLoop
+				}
+				fv = fv.Elem()
+			}
+			fv = fv.Field(i)
+		}
+
+		if f.omitEmpty && isEmptyValue(fv) {
+			continue
+		}
+		e.WriteByte(next)
+		next = ','
+		if opts.escapeHTML {
+			e.WriteString(f.nameEscHTML)
+		} else {
+			e.WriteString(f.nameNonEsc)
+		}
+		opts.quoted = f.quoted
+		f.encoder(e, fv, opts)
+	}
+	if next == '{' {
+		e.WriteString("{}")
+	} else {
+		e.WriteByte('}')
+	}
+}
+
+func newStructEncoder(t reflect.Type) encoderFunc {
+	se := structEncoder{fields: cachedTypeFields(t)}
+	return se.encode
+}
+
+type mapEncoder struct {
+	elemEnc encoderFunc
+}
+
+func (me mapEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
+	if v.IsNil() {
+		e.WriteString("null")
+		return
+	}
+	if e.ptrLevel++; e.ptrLevel > startDetectingCyclesAfter {
+		// We're a large number of nested ptrEncoder.encode calls deep;
+		// start checking if we've run into a pointer cycle.
+		ptr := v.Pointer()
+		if _, ok := e.ptrSeen[ptr]; ok {
+			e.error(&UnsupportedValueError{v, fmt.Sprintf("encountered a cycle via %s", v.Type())})
+		}
+		e.ptrSeen[ptr] = struct{}{}
+		defer delete(e.ptrSeen, ptr)
+	}
+	e.WriteByte('{')
+
+	// Extract and sort the keys.
+	sv := make([]reflectWithString, v.Len())
+	mi := v.MapRange()
+	for i := 0; mi.Next(); i++ {
+		sv[i].k = mi.Key()
+		sv[i].v = mi.Value()
+		if err := sv[i].resolve(); err != nil {
+			e.error(fmt.Errorf("json: encoding error for type %q: %q", v.Type().String(), err.Error()))
+		}
+	}
+	sort.Slice(sv, func(i, j int) bool { return sv[i].ks < sv[j].ks })
+
+	for i, kv := range sv {
+		if i > 0 {
+			e.WriteByte(',')
+		}
+		e.string(kv.ks, opts.escapeHTML)
+		e.WriteByte(':')
+		me.elemEnc(e, kv.v, opts)
+	}
+	e.WriteByte('}')
+	e.ptrLevel--
+}
+
+func newMapEncoder(t reflect.Type) encoderFunc {
+	switch t.Key().Kind() {
+	case reflect.String,
+		reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
+		reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+	default:
+		if !t.Key().Implements(textMarshalerType) {
+			return unsupportedTypeEncoder
+		}
+	}
+	me := mapEncoder{typeEncoder(t.Elem())}
+	return me.encode
+}
+
+func encodeByteSlice(e *encodeState, v reflect.Value, _ encOpts) {
+	if v.IsNil() {
+		e.WriteString("null")
+		return
+	}
+	s := v.Bytes()
+	e.WriteByte('"')
+	encodedLen := base64.StdEncoding.EncodedLen(len(s))
+	if encodedLen <= len(e.scratch) {
+		// If the encoded bytes fit in e.scratch, avoid an extra
+		// allocation and use the cheaper Encoding.Encode.
+		dst := e.scratch[:encodedLen]
+		base64.StdEncoding.Encode(dst, s)
+		e.Write(dst)
+	} else if encodedLen <= 1024 {
+		// The encoded bytes are short enough to allocate for, and
+		// Encoding.Encode is still cheaper.
+		dst := make([]byte, encodedLen)
+		base64.StdEncoding.Encode(dst, s)
+		e.Write(dst)
+	} else {
+		// The encoded bytes are too long to cheaply allocate, and
+		// Encoding.Encode is no longer noticeably cheaper.
+		enc := base64.NewEncoder(base64.StdEncoding, e)
+		enc.Write(s)
+		enc.Close()
+	}
+	e.WriteByte('"')
+}
+
+// sliceEncoder just wraps an arrayEncoder, checking to make sure the value isn't nil.
+type sliceEncoder struct {
+	arrayEnc encoderFunc
+}
+
+func (se sliceEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
+	if v.IsNil() {
+		e.WriteString("null")
+		return
+	}
+	if e.ptrLevel++; e.ptrLevel > startDetectingCyclesAfter {
+		// We're a large number of nested ptrEncoder.encode calls deep;
+		// start checking if we've run into a pointer cycle.
+		// Here we use a struct to memorize the pointer to the first element of the slice
+		// and its length.
+		ptr := struct {
+			ptr uintptr
+			len int
+		}{v.Pointer(), v.Len()}
+		if _, ok := e.ptrSeen[ptr]; ok {
+			e.error(&UnsupportedValueError{v, fmt.Sprintf("encountered a cycle via %s", v.Type())})
+		}
+		e.ptrSeen[ptr] = struct{}{}
+		defer delete(e.ptrSeen, ptr)
+	}
+	se.arrayEnc(e, v, opts)
+	e.ptrLevel--
+}
+
+func newSliceEncoder(t reflect.Type) encoderFunc {
+	// Byte slices get special treatment; arrays don't.
+	if t.Elem().Kind() == reflect.Uint8 {
+		p := reflect.PointerTo(t.Elem())
+		if !p.Implements(marshalerType) && !p.Implements(textMarshalerType) {
+			return encodeByteSlice
+		}
+	}
+	enc := sliceEncoder{newArrayEncoder(t)}
+	return enc.encode
+}
+
+type arrayEncoder struct {
+	elemEnc encoderFunc
+}
+
+func (ae arrayEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
+	e.WriteByte('[')
+	n := v.Len()
+	for i := 0; i < n; i++ {
+		if i > 0 {
+			e.WriteByte(',')
+		}
+		ae.elemEnc(e, v.Index(i), opts)
+	}
+	e.WriteByte(']')
+}
+
+func newArrayEncoder(t reflect.Type) encoderFunc {
+	enc := arrayEncoder{typeEncoder(t.Elem())}
+	return enc.encode
+}
+
+type ptrEncoder struct {
+	elemEnc encoderFunc
+}
+
+func (pe ptrEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
+	if v.IsNil() {
+		e.WriteString("null")
+		return
+	}
+	if e.ptrLevel++; e.ptrLevel > startDetectingCyclesAfter {
+		// We're a large number of nested ptrEncoder.encode calls deep;
+		// start checking if we've run into a pointer cycle.
+		ptr := v.Interface()
+		if _, ok := e.ptrSeen[ptr]; ok {
+			e.error(&UnsupportedValueError{v, fmt.Sprintf("encountered a cycle via %s", v.Type())})
+		}
+		e.ptrSeen[ptr] = struct{}{}
+		defer delete(e.ptrSeen, ptr)
+	}
+	pe.elemEnc(e, v.Elem(), opts)
+	e.ptrLevel--
+}
+
+func newPtrEncoder(t reflect.Type) encoderFunc {
+	enc := ptrEncoder{typeEncoder(t.Elem())}
+	return enc.encode
+}
+
+type condAddrEncoder struct {
+	canAddrEnc, elseEnc encoderFunc
+}
+
+func (ce condAddrEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
+	if v.CanAddr() {
+		ce.canAddrEnc(e, v, opts)
+	} else {
+		ce.elseEnc(e, v, opts)
+	}
+}
+
+// newCondAddrEncoder returns an encoder that checks whether its value
+// CanAddr and delegates to canAddrEnc if so, else to elseEnc.
+func newCondAddrEncoder(canAddrEnc, elseEnc encoderFunc) encoderFunc {
+	enc := condAddrEncoder{canAddrEnc: canAddrEnc, elseEnc: elseEnc}
+	return enc.encode
+}
+
+func isValidTag(s string) bool {
+	if s == "" {
+		return false
+	}
+	for _, c := range s {
+		switch {
+		case strings.ContainsRune("!#$%&()*+-./:;<=>?@[]^_{|}~ ", c):
+			// Backslash and quote chars are reserved, but
+			// otherwise any punctuation chars are allowed
+			// in a tag name.
+		case !unicode.IsLetter(c) && !unicode.IsDigit(c):
+			return false
+		}
+	}
+	return true
+}
+
+func typeByIndex(t reflect.Type, index []int) reflect.Type {
+	for _, i := range index {
+		if t.Kind() == reflect.Pointer {
+			t = t.Elem()
+		}
+		t = t.Field(i).Type
+	}
+	return t
+}
+
+type reflectWithString struct {
+	k  reflect.Value
+	v  reflect.Value
+	ks string
+}
+
+func (w *reflectWithString) resolve() error {
+	if w.k.Kind() == reflect.String {
+		w.ks = w.k.String()
+		return nil
+	}
+	if tm, ok := w.k.Interface().(encoding.TextMarshaler); ok {
+		if w.k.Kind() == reflect.Pointer && w.k.IsNil() {
+			return nil
+		}
+		buf, err := tm.MarshalText()
+		w.ks = string(buf)
+		return err
+	}
+	switch w.k.Kind() {
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		w.ks = strconv.FormatInt(w.k.Int(), 10)
+		return nil
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		w.ks = strconv.FormatUint(w.k.Uint(), 10)
+		return nil
+	}
+	panic("unexpected map key type")
+}
+
+// NOTE: keep in sync with stringBytes below.
+func (e *encodeState) string(s string, escapeHTML bool) {
+	e.WriteByte('"')
+	start := 0
+	for i := 0; i < len(s); {
+		if b := s[i]; b < utf8.RuneSelf {
+			if htmlSafeSet[b] || (!escapeHTML && safeSet[b]) {
+				i++
+				continue
+			}
+			if start < i {
+				e.WriteString(s[start:i])
+			}
+			e.WriteByte('\\')
+			switch b {
+			case '\\', '"':
+				e.WriteByte(b)
+			case '\n':
+				e.WriteByte('n')
+			case '\r':
+				e.WriteByte('r')
+			case '\t':
+				e.WriteByte('t')
+			default:
+				// This encodes bytes < 0x20 except for \t, \n and \r.
+				// If escapeHTML is set, it also escapes <, >, and &
+				// because they can lead to security holes when
+				// user-controlled strings are rendered into JSON
+				// and served to some browsers.
+				e.WriteString(`u00`)
+				e.WriteByte(hex[b>>4])
+				e.WriteByte(hex[b&0xF])
+			}
+			i++
+			start = i
+			continue
+		}
+		c, size := utf8.DecodeRuneInString(s[i:])
+		if c == utf8.RuneError && size == 1 {
+			if start < i {
+				e.WriteString(s[start:i])
+			}
+			e.WriteString(`\ufffd`)
+			i += size
+			start = i
+			continue
+		}
+		// U+2028 is LINE SEPARATOR.
+		// U+2029 is PARAGRAPH SEPARATOR.
+		// They are both technically valid characters in JSON strings,
+		// but don't work in JSONP, which has to be evaluated as JavaScript,
+		// and can lead to security holes there. It is valid JSON to
+		// escape them, so we do so unconditionally.
+		// See http://timelessrepo.com/json-isnt-a-javascript-subset for discussion.
+		if c == '\u2028' || c == '\u2029' {
+			if start < i {
+				e.WriteString(s[start:i])
+			}
+			e.WriteString(`\u202`)
+			e.WriteByte(hex[c&0xF])
+			i += size
+			start = i
+			continue
+		}
+		i += size
+	}
+	if start < len(s) {
+		e.WriteString(s[start:])
+	}
+	e.WriteByte('"')
+}
+
+// NOTE: keep in sync with string above.
+func (e *encodeState) stringBytes(s []byte, escapeHTML bool) {
+	e.WriteByte('"')
+	start := 0
+	for i := 0; i < len(s); {
+		if b := s[i]; b < utf8.RuneSelf {
+			if htmlSafeSet[b] || (!escapeHTML && safeSet[b]) {
+				i++
+				continue
+			}
+			if start < i {
+				e.Write(s[start:i])
+			}
+			e.WriteByte('\\')
+			switch b {
+			case '\\', '"':
+				e.WriteByte(b)
+			case '\n':
+				e.WriteByte('n')
+			case '\r':
+				e.WriteByte('r')
+			case '\t':
+				e.WriteByte('t')
+			default:
+				// This encodes bytes < 0x20 except for \t, \n and \r.
+				// If escapeHTML is set, it also escapes <, >, and &
+				// because they can lead to security holes when
+				// user-controlled strings are rendered into JSON
+				// and served to some browsers.
+				e.WriteString(`u00`)
+				e.WriteByte(hex[b>>4])
+				e.WriteByte(hex[b&0xF])
+			}
+			i++
+			start = i
+			continue
+		}
+		c, size := utf8.DecodeRune(s[i:])
+		if c == utf8.RuneError && size == 1 {
+			if start < i {
+				e.Write(s[start:i])
+			}
+			e.WriteString(`\ufffd`)
+			i += size
+			start = i
+			continue
+		}
+		// U+2028 is LINE SEPARATOR.
+		// U+2029 is PARAGRAPH SEPARATOR.
+		// They are both technically valid characters in JSON strings,
+		// but don't work in JSONP, which has to be evaluated as JavaScript,
+		// and can lead to security holes there. It is valid JSON to
+		// escape them, so we do so unconditionally.
+		// See http://timelessrepo.com/json-isnt-a-javascript-subset for discussion.
+		if c == '\u2028' || c == '\u2029' {
+			if start < i {
+				e.Write(s[start:i])
+			}
+			e.WriteString(`\u202`)
+			e.WriteByte(hex[c&0xF])
+			i += size
+			start = i
+			continue
+		}
+		i += size
+	}
+	if start < len(s) {
+		e.Write(s[start:])
+	}
+	e.WriteByte('"')
+}
+
+// A field represents a single field found in a struct.
+type field struct {
+	name      string
+	nameBytes []byte                 // []byte(name)
+	equalFold func(s, t []byte) bool // bytes.EqualFold or equivalent
+
+	nameNonEsc  string // `"` + name + `":`
+	nameEscHTML string // `"` + HTMLEscape(name) + `":`
+
+	tag       bool
+	index     []int
+	typ       reflect.Type
+	omitEmpty bool
+	quoted    bool
+
+	encoder encoderFunc
+}
+
+// byIndex sorts field by index sequence.
+type byIndex []field
+
+func (x byIndex) Len() int { return len(x) }
+
+func (x byIndex) Swap(i, j int) { x[i], x[j] = x[j], x[i] }
+
+func (x byIndex) Less(i, j int) bool {
+	for k, xik := range x[i].index {
+		if k >= len(x[j].index) {
+			return false
+		}
+		if xik != x[j].index[k] {
+			return xik < x[j].index[k]
+		}
+	}
+	return len(x[i].index) < len(x[j].index)
+}
+
+// typeFields returns a list of fields that JSON should recognize for the given type.
+// The algorithm is breadth-first search over the set of structs to include - the top struct
+// and then any reachable anonymous structs.
+func typeFields(t reflect.Type) structFields {
+	// Anonymous fields to explore at the current level and the next.
+	current := []field{}
+	next := []field{{typ: t}}
+
+	// Count of queued names for current level and the next.
+	var count, nextCount map[reflect.Type]int
+
+	// Types already visited at an earlier level.
+	visited := map[reflect.Type]bool{}
+
+	// Fields found.
+	var fields []field
+
+	// Buffer to run HTMLEscape on field names.
+	var nameEscBuf bytes.Buffer
+
+	for len(next) > 0 {
+		current, next = next, current[:0]
+		count, nextCount = nextCount, map[reflect.Type]int{}
+
+		for _, f := range current {
+			if visited[f.typ] {
+				continue
+			}
+			visited[f.typ] = true
+
+			// Scan f.typ for fields to include.
+			for i := 0; i < f.typ.NumField(); i++ {
+				sf := f.typ.Field(i)
+				if sf.Anonymous {
+					t := sf.Type
+					if t.Kind() == reflect.Pointer {
+						t = t.Elem()
+					}
+					if !sf.IsExported() && t.Kind() != reflect.Struct {
+						// Ignore embedded fields of unexported non-struct types.
+						continue
+					}
+					// Do not ignore embedded fields of unexported struct types
+					// since they may have exported fields.
+				} else if !sf.IsExported() {
+					// Ignore unexported non-embedded fields.
+					continue
+				}
+				tag := sf.Tag.Get("json")
+				if tag == "-" {
+					continue
+				}
+				name, opts := parseTag(tag)
+				if !isValidTag(name) {
+					name = ""
+				}
+				index := make([]int, len(f.index)+1)
+				copy(index, f.index)
+				index[len(f.index)] = i
+
+				ft := sf.Type
+				if ft.Name() == "" && ft.Kind() == reflect.Pointer {
+					// Follow pointer.
+					ft = ft.Elem()
+				}
+
+				// Only strings, floats, integers, and booleans can be quoted.
+				quoted := false
+				if opts.Contains("string") {
+					switch ft.Kind() {
+					case reflect.Bool,
+						reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
+						reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr,
+						reflect.Float32, reflect.Float64,
+						reflect.String:
+						quoted = true
+					}
+				}
+
+				// Record found field and index sequence.
+				if name != "" || !sf.Anonymous || ft.Kind() != reflect.Struct {
+					tagged := name != ""
+					if name == "" {
+						name = sf.Name
+					}
+					field := field{
+						name:      name,
+						tag:       tagged,
+						index:     index,
+						typ:       ft,
+						omitEmpty: opts.Contains("omitempty"),
+						quoted:    quoted,
+					}
+					field.nameBytes = []byte(field.name)
+					field.equalFold = foldFunc(field.nameBytes)
+
+					// Build nameEscHTML and nameNonEsc ahead of time.
+					nameEscBuf.Reset()
+					nameEscBuf.WriteString(`"`)
+					HTMLEscape(&nameEscBuf, field.nameBytes)
+					nameEscBuf.WriteString(`":`)
+					field.nameEscHTML = nameEscBuf.String()
+					field.nameNonEsc = `"` + field.name + `":`
+
+					fields = append(fields, field)
+					if count[f.typ] > 1 {
+						// If there were multiple instances, add a second,
+						// so that the annihilation code will see a duplicate.
+						// It only cares about the distinction between 1 or 2,
+						// so don't bother generating any more copies.
+						fields = append(fields, fields[len(fields)-1])
+					}
+					continue
+				}
+
+				// Record new anonymous struct to explore in next round.
+				nextCount[ft]++
+				if nextCount[ft] == 1 {
+					next = append(next, field{name: ft.Name(), index: index, typ: ft})
+				}
+			}
+		}
+	}
+
+	sort.Slice(fields, func(i, j int) bool {
+		x := fields
+		// sort field by name, breaking ties with depth, then
+		// breaking ties with "name came from json tag", then
+		// breaking ties with index sequence.
+		if x[i].name != x[j].name {
+			return x[i].name < x[j].name
+		}
+		if len(x[i].index) != len(x[j].index) {
+			return len(x[i].index) < len(x[j].index)
+		}
+		if x[i].tag != x[j].tag {
+			return x[i].tag
+		}
+		return byIndex(x).Less(i, j)
+	})
+
+	// Delete all fields that are hidden by the Go rules for embedded fields,
+	// except that fields with JSON tags are promoted.
+
+	// The fields are sorted in primary order of name, secondary order
+	// of field index length. Loop over names; for each name, delete
+	// hidden fields by choosing the one dominant field that survives.
+	out := fields[:0]
+	for advance, i := 0, 0; i < len(fields); i += advance {
+		// One iteration per name.
+		// Find the sequence of fields with the name of this first field.
+		fi := fields[i]
+		name := fi.name
+		for advance = 1; i+advance < len(fields); advance++ {
+			fj := fields[i+advance]
+			if fj.name != name {
+				break
+			}
+		}
+		if advance == 1 { // Only one field with this name
+			out = append(out, fi)
+			continue
+		}
+		dominant, ok := dominantField(fields[i : i+advance])
+		if ok {
+			out = append(out, dominant)
+		}
+	}
+
+	fields = out
+	sort.Sort(byIndex(fields))
+
+	for i := range fields {
+		f := &fields[i]
+		f.encoder = typeEncoder(typeByIndex(t, f.index))
+	}
+	nameIndex := make(map[string]int, len(fields))
+	for i, field := range fields {
+		nameIndex[field.name] = i
+	}
+	return structFields{fields, nameIndex}
+}
+
+// dominantField looks through the fields, all of which are known to
+// have the same name, to find the single field that dominates the
+// others using Go's embedding rules, modified by the presence of
+// JSON tags. If there are multiple top-level fields, the boolean
+// will be false: This condition is an error in Go and we skip all
+// the fields.
+func dominantField(fields []field) (field, bool) {
+	// The fields are sorted in increasing index-length order, then by presence of tag.
+	// That means that the first field is the dominant one. We need only check
+	// for error cases: two fields at top level, either both tagged or neither tagged.
+	if len(fields) > 1 && len(fields[0].index) == len(fields[1].index) && fields[0].tag == fields[1].tag {
+		return field{}, false
+	}
+	return fields[0], true
+}
+
+var fieldCache sync.Map // map[reflect.Type]structFields
+
+// cachedTypeFields is like typeFields but uses a cache to avoid repeated work.
+func cachedTypeFields(t reflect.Type) structFields {
+	if f, ok := fieldCache.Load(t); ok {
+		return f.(structFields)
+	}
+	f, _ := fieldCache.LoadOrStore(t, typeFields(t))
+	return f.(structFields)
+}
diff --git a/src/encoding/json/encode_test.go b/src/encoding/json/encode_test.go
new file mode 100644
index 0000000..0b021f0
--- /dev/null
+++ b/src/encoding/json/encode_test.go
@@ -0,0 +1,1203 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json
+
+import (
+	"bytes"
+	"encoding"
+	"fmt"
+	"log"
+	"math"
+	"reflect"
+	"regexp"
+	"strconv"
+	"testing"
+	"unicode"
+)
+
+type Optionals struct {
+	Sr string `json:"sr"`
+	So string `json:"so,omitempty"`
+	Sw string `json:"-"`
+
+	Ir int `json:"omitempty"` // actually named omitempty, not an option
+	Io int `json:"io,omitempty"`
+
+	Slr []string `json:"slr,random"`
+	Slo []string `json:"slo,omitempty"`
+
+	Mr map[string]any `json:"mr"`
+	Mo map[string]any `json:",omitempty"`
+
+	Fr float64 `json:"fr"`
+	Fo float64 `json:"fo,omitempty"`
+
+	Br bool `json:"br"`
+	Bo bool `json:"bo,omitempty"`
+
+	Ur uint `json:"ur"`
+	Uo uint `json:"uo,omitempty"`
+
+	Str struct{} `json:"str"`
+	Sto struct{} `json:"sto,omitempty"`
+}
+
+var optionalsExpected = `{
+ "sr": "",
+ "omitempty": 0,
+ "slr": null,
+ "mr": {},
+ "fr": 0,
+ "br": false,
+ "ur": 0,
+ "str": {},
+ "sto": {}
+}`
+
+func TestOmitEmpty(t *testing.T) {
+	var o Optionals
+	o.Sw = "something"
+	o.Mr = map[string]any{}
+	o.Mo = map[string]any{}
+
+	got, err := MarshalIndent(&o, "", " ")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got := string(got); got != optionalsExpected {
+		t.Errorf(" got: %s\nwant: %s\n", got, optionalsExpected)
+	}
+}
+
+type StringTag struct {
+	BoolStr    bool    `json:",string"`
+	IntStr     int64   `json:",string"`
+	UintptrStr uintptr `json:",string"`
+	StrStr     string  `json:",string"`
+	NumberStr  Number  `json:",string"`
+}
+
+func TestRoundtripStringTag(t *testing.T) {
+	tests := []struct {
+		name string
+		in   StringTag
+		want string // empty to just test that we roundtrip
+	}{
+		{
+			name: "AllTypes",
+			in: StringTag{
+				BoolStr:    true,
+				IntStr:     42,
+				UintptrStr: 44,
+				StrStr:     "xzbit",
+				NumberStr:  "46",
+			},
+			want: `{
+				"BoolStr": "true",
+				"IntStr": "42",
+				"UintptrStr": "44",
+				"StrStr": "\"xzbit\"",
+				"NumberStr": "46"
+			}`,
+		},
+		{
+			// See golang.org/issues/38173.
+			name: "StringDoubleEscapes",
+			in: StringTag{
+				StrStr:    "\b\f\n\r\t\"\\",
+				NumberStr: "0", // just to satisfy the roundtrip
+			},
+			want: `{
+				"BoolStr": "false",
+				"IntStr": "0",
+				"UintptrStr": "0",
+				"StrStr": "\"\\u0008\\u000c\\n\\r\\t\\\"\\\\\"",
+				"NumberStr": "0"
+			}`,
+		},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			// Indent with a tab prefix to make the multi-line string
+			// literals in the table nicer to read.
+			got, err := MarshalIndent(&test.in, "\t\t\t", "\t")
+			if err != nil {
+				t.Fatal(err)
+			}
+			if got := string(got); got != test.want {
+				t.Fatalf(" got: %s\nwant: %s\n", got, test.want)
+			}
+
+			// Verify that it round-trips.
+			var s2 StringTag
+			if err := Unmarshal(got, &s2); err != nil {
+				t.Fatalf("Decode: %v", err)
+			}
+			if !reflect.DeepEqual(test.in, s2) {
+				t.Fatalf("decode didn't match.\nsource: %#v\nEncoded as:\n%s\ndecode: %#v", test.in, string(got), s2)
+			}
+		})
+	}
+}
+
+// byte slices are special even if they're renamed types.
+type renamedByte byte
+type renamedByteSlice []byte
+type renamedRenamedByteSlice []renamedByte
+
+func TestEncodeRenamedByteSlice(t *testing.T) {
+	s := renamedByteSlice("abc")
+	result, err := Marshal(s)
+	if err != nil {
+		t.Fatal(err)
+	}
+	expect := `"YWJj"`
+	if string(result) != expect {
+		t.Errorf(" got %s want %s", result, expect)
+	}
+	r := renamedRenamedByteSlice("abc")
+	result, err = Marshal(r)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if string(result) != expect {
+		t.Errorf(" got %s want %s", result, expect)
+	}
+}
+
+type SamePointerNoCycle struct {
+	Ptr1, Ptr2 *SamePointerNoCycle
+}
+
+var samePointerNoCycle = &SamePointerNoCycle{}
+
+type PointerCycle struct {
+	Ptr *PointerCycle
+}
+
+var pointerCycle = &PointerCycle{}
+
+type PointerCycleIndirect struct {
+	Ptrs []any
+}
+
+type RecursiveSlice []RecursiveSlice
+
+var (
+	pointerCycleIndirect = &PointerCycleIndirect{}
+	mapCycle             = make(map[string]any)
+	sliceCycle           = []any{nil}
+	sliceNoCycle         = []any{nil, nil}
+	recursiveSliceCycle  = []RecursiveSlice{nil}
+)
+
+func init() {
+	ptr := &SamePointerNoCycle{}
+	samePointerNoCycle.Ptr1 = ptr
+	samePointerNoCycle.Ptr2 = ptr
+
+	pointerCycle.Ptr = pointerCycle
+	pointerCycleIndirect.Ptrs = []any{pointerCycleIndirect}
+
+	mapCycle["x"] = mapCycle
+	sliceCycle[0] = sliceCycle
+	sliceNoCycle[1] = sliceNoCycle[:1]
+	for i := startDetectingCyclesAfter; i > 0; i-- {
+		sliceNoCycle = []any{sliceNoCycle}
+	}
+	recursiveSliceCycle[0] = recursiveSliceCycle
+}
+
+func TestSamePointerNoCycle(t *testing.T) {
+	if _, err := Marshal(samePointerNoCycle); err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+}
+
+func TestSliceNoCycle(t *testing.T) {
+	if _, err := Marshal(sliceNoCycle); err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+}
+
+var unsupportedValues = []any{
+	math.NaN(),
+	math.Inf(-1),
+	math.Inf(1),
+	pointerCycle,
+	pointerCycleIndirect,
+	mapCycle,
+	sliceCycle,
+	recursiveSliceCycle,
+}
+
+func TestUnsupportedValues(t *testing.T) {
+	for _, v := range unsupportedValues {
+		if _, err := Marshal(v); err != nil {
+			if _, ok := err.(*UnsupportedValueError); !ok {
+				t.Errorf("for %v, got %T want UnsupportedValueError", v, err)
+			}
+		} else {
+			t.Errorf("for %v, expected error", v)
+		}
+	}
+}
+
+// Issue 43207
+func TestMarshalTextFloatMap(t *testing.T) {
+	m := map[textfloat]string{
+		textfloat(math.NaN()): "1",
+		textfloat(math.NaN()): "1",
+	}
+	got, err := Marshal(m)
+	if err != nil {
+		t.Errorf("Marshal() error: %v", err)
+	}
+	want := `{"TF:NaN":"1","TF:NaN":"1"}`
+	if string(got) != want {
+		t.Errorf("Marshal() = %s, want %s", got, want)
+	}
+}
+
+// Ref has Marshaler and Unmarshaler methods with pointer receiver.
+type Ref int
+
+func (*Ref) MarshalJSON() ([]byte, error) {
+	return []byte(`"ref"`), nil
+}
+
+func (r *Ref) UnmarshalJSON([]byte) error {
+	*r = 12
+	return nil
+}
+
+// Val has Marshaler methods with value receiver.
+type Val int
+
+func (Val) MarshalJSON() ([]byte, error) {
+	return []byte(`"val"`), nil
+}
+
+// RefText has Marshaler and Unmarshaler methods with pointer receiver.
+type RefText int
+
+func (*RefText) MarshalText() ([]byte, error) {
+	return []byte(`"ref"`), nil
+}
+
+func (r *RefText) UnmarshalText([]byte) error {
+	*r = 13
+	return nil
+}
+
+// ValText has Marshaler methods with value receiver.
+type ValText int
+
+func (ValText) MarshalText() ([]byte, error) {
+	return []byte(`"val"`), nil
+}
+
+func TestRefValMarshal(t *testing.T) {
+	var s = struct {
+		R0 Ref
+		R1 *Ref
+		R2 RefText
+		R3 *RefText
+		V0 Val
+		V1 *Val
+		V2 ValText
+		V3 *ValText
+	}{
+		R0: 12,
+		R1: new(Ref),
+		R2: 14,
+		R3: new(RefText),
+		V0: 13,
+		V1: new(Val),
+		V2: 15,
+		V3: new(ValText),
+	}
+	const want = `{"R0":"ref","R1":"ref","R2":"\"ref\"","R3":"\"ref\"","V0":"val","V1":"val","V2":"\"val\"","V3":"\"val\""}`
+	b, err := Marshal(&s)
+	if err != nil {
+		t.Fatalf("Marshal: %v", err)
+	}
+	if got := string(b); got != want {
+		t.Errorf("got %q, want %q", got, want)
+	}
+}
+
+// C implements Marshaler and returns unescaped JSON.
+type C int
+
+func (C) MarshalJSON() ([]byte, error) {
+	return []byte(`"<&>"`), nil
+}
+
+// CText implements Marshaler and returns unescaped text.
+type CText int
+
+func (CText) MarshalText() ([]byte, error) {
+	return []byte(`"<&>"`), nil
+}
+
+func TestMarshalerEscaping(t *testing.T) {
+	var c C
+	want := `"\u003c\u0026\u003e"`
+	b, err := Marshal(c)
+	if err != nil {
+		t.Fatalf("Marshal(c): %v", err)
+	}
+	if got := string(b); got != want {
+		t.Errorf("Marshal(c) = %#q, want %#q", got, want)
+	}
+
+	var ct CText
+	want = `"\"\u003c\u0026\u003e\""`
+	b, err = Marshal(ct)
+	if err != nil {
+		t.Fatalf("Marshal(ct): %v", err)
+	}
+	if got := string(b); got != want {
+		t.Errorf("Marshal(ct) = %#q, want %#q", got, want)
+	}
+}
+
+func TestAnonymousFields(t *testing.T) {
+	tests := []struct {
+		label     string     // Test name
+		makeInput func() any // Function to create input value
+		want      string     // Expected JSON output
+	}{{
+		// Both S1 and S2 have a field named X. From the perspective of S,
+		// it is ambiguous which one X refers to.
+		// This should not serialize either field.
+		label: "AmbiguousField",
+		makeInput: func() any {
+			type (
+				S1 struct{ x, X int }
+				S2 struct{ x, X int }
+				S  struct {
+					S1
+					S2
+				}
+			)
+			return S{S1{1, 2}, S2{3, 4}}
+		},
+		want: `{}`,
+	}, {
+		label: "DominantField",
+		// Both S1 and S2 have a field named X, but since S has an X field as
+		// well, it takes precedence over S1.X and S2.X.
+		makeInput: func() any {
+			type (
+				S1 struct{ x, X int }
+				S2 struct{ x, X int }
+				S  struct {
+					S1
+					S2
+					x, X int
+				}
+			)
+			return S{S1{1, 2}, S2{3, 4}, 5, 6}
+		},
+		want: `{"X":6}`,
+	}, {
+		// Unexported embedded field of non-struct type should not be serialized.
+		label: "UnexportedEmbeddedInt",
+		makeInput: func() any {
+			type (
+				myInt int
+				S     struct{ myInt }
+			)
+			return S{5}
+		},
+		want: `{}`,
+	}, {
+		// Exported embedded field of non-struct type should be serialized.
+		label: "ExportedEmbeddedInt",
+		makeInput: func() any {
+			type (
+				MyInt int
+				S     struct{ MyInt }
+			)
+			return S{5}
+		},
+		want: `{"MyInt":5}`,
+	}, {
+		// Unexported embedded field of pointer to non-struct type
+		// should not be serialized.
+		label: "UnexportedEmbeddedIntPointer",
+		makeInput: func() any {
+			type (
+				myInt int
+				S     struct{ *myInt }
+			)
+			s := S{new(myInt)}
+			*s.myInt = 5
+			return s
+		},
+		want: `{}`,
+	}, {
+		// Exported embedded field of pointer to non-struct type
+		// should be serialized.
+		label: "ExportedEmbeddedIntPointer",
+		makeInput: func() any {
+			type (
+				MyInt int
+				S     struct{ *MyInt }
+			)
+			s := S{new(MyInt)}
+			*s.MyInt = 5
+			return s
+		},
+		want: `{"MyInt":5}`,
+	}, {
+		// Exported fields of embedded structs should have their
+		// exported fields be serialized regardless of whether the struct types
+		// themselves are exported.
+		label: "EmbeddedStruct",
+		makeInput: func() any {
+			type (
+				s1 struct{ x, X int }
+				S2 struct{ y, Y int }
+				S  struct {
+					s1
+					S2
+				}
+			)
+			return S{s1{1, 2}, S2{3, 4}}
+		},
+		want: `{"X":2,"Y":4}`,
+	}, {
+		// Exported fields of pointers to embedded structs should have their
+		// exported fields be serialized regardless of whether the struct types
+		// themselves are exported.
+		label: "EmbeddedStructPointer",
+		makeInput: func() any {
+			type (
+				s1 struct{ x, X int }
+				S2 struct{ y, Y int }
+				S  struct {
+					*s1
+					*S2
+				}
+			)
+			return S{&s1{1, 2}, &S2{3, 4}}
+		},
+		want: `{"X":2,"Y":4}`,
+	}, {
+		// Exported fields on embedded unexported structs at multiple levels
+		// of nesting should still be serialized.
+		label: "NestedStructAndInts",
+		makeInput: func() any {
+			type (
+				MyInt1 int
+				MyInt2 int
+				myInt  int
+				s2     struct {
+					MyInt2
+					myInt
+				}
+				s1 struct {
+					MyInt1
+					myInt
+					s2
+				}
+				S struct {
+					s1
+					myInt
+				}
+			)
+			return S{s1{1, 2, s2{3, 4}}, 6}
+		},
+		want: `{"MyInt1":1,"MyInt2":3}`,
+	}, {
+		// If an anonymous struct pointer field is nil, we should ignore
+		// the embedded fields behind it. Not properly doing so may
+		// result in the wrong output or reflect panics.
+		label: "EmbeddedFieldBehindNilPointer",
+		makeInput: func() any {
+			type (
+				S2 struct{ Field string }
+				S  struct{ *S2 }
+			)
+			return S{}
+		},
+		want: `{}`,
+	}}
+
+	for _, tt := range tests {
+		t.Run(tt.label, func(t *testing.T) {
+			b, err := Marshal(tt.makeInput())
+			if err != nil {
+				t.Fatalf("Marshal() = %v, want nil error", err)
+			}
+			if string(b) != tt.want {
+				t.Fatalf("Marshal() = %q, want %q", b, tt.want)
+			}
+		})
+	}
+}
+
+type BugA struct {
+	S string
+}
+
+type BugB struct {
+	BugA
+	S string
+}
+
+type BugC struct {
+	S string
+}
+
+// Legal Go: We never use the repeated embedded field (S).
+type BugX struct {
+	A int
+	BugA
+	BugB
+}
+
+// golang.org/issue/16042.
+// Even if a nil interface value is passed in, as long as
+// it implements Marshaler, it should be marshaled.
+type nilJSONMarshaler string
+
+func (nm *nilJSONMarshaler) MarshalJSON() ([]byte, error) {
+	if nm == nil {
+		return Marshal("0zenil0")
+	}
+	return Marshal("zenil:" + string(*nm))
+}
+
+// golang.org/issue/34235.
+// Even if a nil interface value is passed in, as long as
+// it implements encoding.TextMarshaler, it should be marshaled.
+type nilTextMarshaler string
+
+func (nm *nilTextMarshaler) MarshalText() ([]byte, error) {
+	if nm == nil {
+		return []byte("0zenil0"), nil
+	}
+	return []byte("zenil:" + string(*nm)), nil
+}
+
+// See golang.org/issue/16042 and golang.org/issue/34235.
+func TestNilMarshal(t *testing.T) {
+	testCases := []struct {
+		v    any
+		want string
+	}{
+		{v: nil, want: `null`},
+		{v: new(float64), want: `0`},
+		{v: []any(nil), want: `null`},
+		{v: []string(nil), want: `null`},
+		{v: map[string]string(nil), want: `null`},
+		{v: []byte(nil), want: `null`},
+		{v: struct{ M string }{"gopher"}, want: `{"M":"gopher"}`},
+		{v: struct{ M Marshaler }{}, want: `{"M":null}`},
+		{v: struct{ M Marshaler }{(*nilJSONMarshaler)(nil)}, want: `{"M":"0zenil0"}`},
+		{v: struct{ M any }{(*nilJSONMarshaler)(nil)}, want: `{"M":null}`},
+		{v: struct{ M encoding.TextMarshaler }{}, want: `{"M":null}`},
+		{v: struct{ M encoding.TextMarshaler }{(*nilTextMarshaler)(nil)}, want: `{"M":"0zenil0"}`},
+		{v: struct{ M any }{(*nilTextMarshaler)(nil)}, want: `{"M":null}`},
+	}
+
+	for _, tt := range testCases {
+		out, err := Marshal(tt.v)
+		if err != nil || string(out) != tt.want {
+			t.Errorf("Marshal(%#v) = %#q, %#v, want %#q, nil", tt.v, out, err, tt.want)
+			continue
+		}
+	}
+}
+
+// Issue 5245.
+func TestEmbeddedBug(t *testing.T) {
+	v := BugB{
+		BugA{"A"},
+		"B",
+	}
+	b, err := Marshal(v)
+	if err != nil {
+		t.Fatal("Marshal:", err)
+	}
+	want := `{"S":"B"}`
+	got := string(b)
+	if got != want {
+		t.Fatalf("Marshal: got %s want %s", got, want)
+	}
+	// Now check that the duplicate field, S, does not appear.
+	x := BugX{
+		A: 23,
+	}
+	b, err = Marshal(x)
+	if err != nil {
+		t.Fatal("Marshal:", err)
+	}
+	want = `{"A":23}`
+	got = string(b)
+	if got != want {
+		t.Fatalf("Marshal: got %s want %s", got, want)
+	}
+}
+
+type BugD struct { // Same as BugA after tagging.
+	XXX string `json:"S"`
+}
+
+// BugD's tagged S field should dominate BugA's.
+type BugY struct {
+	BugA
+	BugD
+}
+
+// Test that a field with a tag dominates untagged fields.
+func TestTaggedFieldDominates(t *testing.T) {
+	v := BugY{
+		BugA{"BugA"},
+		BugD{"BugD"},
+	}
+	b, err := Marshal(v)
+	if err != nil {
+		t.Fatal("Marshal:", err)
+	}
+	want := `{"S":"BugD"}`
+	got := string(b)
+	if got != want {
+		t.Fatalf("Marshal: got %s want %s", got, want)
+	}
+}
+
+// There are no tags here, so S should not appear.
+type BugZ struct {
+	BugA
+	BugC
+	BugY // Contains a tagged S field through BugD; should not dominate.
+}
+
+func TestDuplicatedFieldDisappears(t *testing.T) {
+	v := BugZ{
+		BugA{"BugA"},
+		BugC{"BugC"},
+		BugY{
+			BugA{"nested BugA"},
+			BugD{"nested BugD"},
+		},
+	}
+	b, err := Marshal(v)
+	if err != nil {
+		t.Fatal("Marshal:", err)
+	}
+	want := `{}`
+	got := string(b)
+	if got != want {
+		t.Fatalf("Marshal: got %s want %s", got, want)
+	}
+}
+
+func TestStringBytes(t *testing.T) {
+	t.Parallel()
+	// Test that encodeState.stringBytes and encodeState.string use the same encoding.
+	var r []rune
+	for i := '\u0000'; i <= unicode.MaxRune; i++ {
+		if testing.Short() && i > 1000 {
+			i = unicode.MaxRune
+		}
+		r = append(r, i)
+	}
+	s := string(r) + "\xff\xff\xffhello" // some invalid UTF-8 too
+
+	for _, escapeHTML := range []bool{true, false} {
+		es := &encodeState{}
+		es.string(s, escapeHTML)
+
+		esBytes := &encodeState{}
+		esBytes.stringBytes([]byte(s), escapeHTML)
+
+		enc := es.Buffer.String()
+		encBytes := esBytes.Buffer.String()
+		if enc != encBytes {
+			i := 0
+			for i < len(enc) && i < len(encBytes) && enc[i] == encBytes[i] {
+				i++
+			}
+			enc = enc[i:]
+			encBytes = encBytes[i:]
+			i = 0
+			for i < len(enc) && i < len(encBytes) && enc[len(enc)-i-1] == encBytes[len(encBytes)-i-1] {
+				i++
+			}
+			enc = enc[:len(enc)-i]
+			encBytes = encBytes[:len(encBytes)-i]
+
+			if len(enc) > 20 {
+				enc = enc[:20] + "..."
+			}
+			if len(encBytes) > 20 {
+				encBytes = encBytes[:20] + "..."
+			}
+
+			t.Errorf("with escapeHTML=%t, encodings differ at %#q vs %#q",
+				escapeHTML, enc, encBytes)
+		}
+	}
+}
+
+func TestIssue10281(t *testing.T) {
+	type Foo struct {
+		N Number
+	}
+	x := Foo{Number(`invalid`)}
+
+	b, err := Marshal(&x)
+	if err == nil {
+		t.Errorf("Marshal(&x) = %#q; want error", b)
+	}
+}
+
+func TestHTMLEscape(t *testing.T) {
+	var b, want bytes.Buffer
+	m := `{"M":"<html>foo &` + "\xe2\x80\xa8 \xe2\x80\xa9" + `</html>"}`
+	want.Write([]byte(`{"M":"\u003chtml\u003efoo \u0026\u2028 \u2029\u003c/html\u003e"}`))
+	HTMLEscape(&b, []byte(m))
+	if !bytes.Equal(b.Bytes(), want.Bytes()) {
+		t.Errorf("HTMLEscape(&b, []byte(m)) = %s; want %s", b.Bytes(), want.Bytes())
+	}
+}
+
+// golang.org/issue/8582
+func TestEncodePointerString(t *testing.T) {
+	type stringPointer struct {
+		N *int64 `json:"n,string"`
+	}
+	var n int64 = 42
+	b, err := Marshal(stringPointer{N: &n})
+	if err != nil {
+		t.Fatalf("Marshal: %v", err)
+	}
+	if got, want := string(b), `{"n":"42"}`; got != want {
+		t.Errorf("Marshal = %s, want %s", got, want)
+	}
+	var back stringPointer
+	err = Unmarshal(b, &back)
+	if err != nil {
+		t.Fatalf("Unmarshal: %v", err)
+	}
+	if back.N == nil {
+		t.Fatalf("Unmarshaled nil N field")
+	}
+	if *back.N != 42 {
+		t.Fatalf("*N = %d; want 42", *back.N)
+	}
+}
+
+var encodeStringTests = []struct {
+	in  string
+	out string
+}{
+	{"\x00", `"\u0000"`},
+	{"\x01", `"\u0001"`},
+	{"\x02", `"\u0002"`},
+	{"\x03", `"\u0003"`},
+	{"\x04", `"\u0004"`},
+	{"\x05", `"\u0005"`},
+	{"\x06", `"\u0006"`},
+	{"\x07", `"\u0007"`},
+	{"\x08", `"\u0008"`},
+	{"\x09", `"\t"`},
+	{"\x0a", `"\n"`},
+	{"\x0b", `"\u000b"`},
+	{"\x0c", `"\u000c"`},
+	{"\x0d", `"\r"`},
+	{"\x0e", `"\u000e"`},
+	{"\x0f", `"\u000f"`},
+	{"\x10", `"\u0010"`},
+	{"\x11", `"\u0011"`},
+	{"\x12", `"\u0012"`},
+	{"\x13", `"\u0013"`},
+	{"\x14", `"\u0014"`},
+	{"\x15", `"\u0015"`},
+	{"\x16", `"\u0016"`},
+	{"\x17", `"\u0017"`},
+	{"\x18", `"\u0018"`},
+	{"\x19", `"\u0019"`},
+	{"\x1a", `"\u001a"`},
+	{"\x1b", `"\u001b"`},
+	{"\x1c", `"\u001c"`},
+	{"\x1d", `"\u001d"`},
+	{"\x1e", `"\u001e"`},
+	{"\x1f", `"\u001f"`},
+}
+
+func TestEncodeString(t *testing.T) {
+	for _, tt := range encodeStringTests {
+		b, err := Marshal(tt.in)
+		if err != nil {
+			t.Errorf("Marshal(%q): %v", tt.in, err)
+			continue
+		}
+		out := string(b)
+		if out != tt.out {
+			t.Errorf("Marshal(%q) = %#q, want %#q", tt.in, out, tt.out)
+		}
+	}
+}
+
+type jsonbyte byte
+
+func (b jsonbyte) MarshalJSON() ([]byte, error) { return tenc(`{"JB":%d}`, b) }
+
+type textbyte byte
+
+func (b textbyte) MarshalText() ([]byte, error) { return tenc(`TB:%d`, b) }
+
+type jsonint int
+
+func (i jsonint) MarshalJSON() ([]byte, error) { return tenc(`{"JI":%d}`, i) }
+
+type textint int
+
+func (i textint) MarshalText() ([]byte, error) { return tenc(`TI:%d`, i) }
+
+func tenc(format string, a ...any) ([]byte, error) {
+	var buf bytes.Buffer
+	fmt.Fprintf(&buf, format, a...)
+	return buf.Bytes(), nil
+}
+
+type textfloat float64
+
+func (f textfloat) MarshalText() ([]byte, error) { return tenc(`TF:%0.2f`, f) }
+
+// Issue 13783
+func TestEncodeBytekind(t *testing.T) {
+	testdata := []struct {
+		data any
+		want string
+	}{
+		{byte(7), "7"},
+		{jsonbyte(7), `{"JB":7}`},
+		{textbyte(4), `"TB:4"`},
+		{jsonint(5), `{"JI":5}`},
+		{textint(1), `"TI:1"`},
+		{[]byte{0, 1}, `"AAE="`},
+		{[]jsonbyte{0, 1}, `[{"JB":0},{"JB":1}]`},
+		{[][]jsonbyte{{0, 1}, {3}}, `[[{"JB":0},{"JB":1}],[{"JB":3}]]`},
+		{[]textbyte{2, 3}, `["TB:2","TB:3"]`},
+		{[]jsonint{5, 4}, `[{"JI":5},{"JI":4}]`},
+		{[]textint{9, 3}, `["TI:9","TI:3"]`},
+		{[]int{9, 3}, `[9,3]`},
+		{[]textfloat{12, 3}, `["TF:12.00","TF:3.00"]`},
+	}
+	for _, d := range testdata {
+		js, err := Marshal(d.data)
+		if err != nil {
+			t.Error(err)
+			continue
+		}
+		got, want := string(js), d.want
+		if got != want {
+			t.Errorf("got %s, want %s", got, want)
+		}
+	}
+}
+
+func TestTextMarshalerMapKeysAreSorted(t *testing.T) {
+	b, err := Marshal(map[unmarshalerText]int{
+		{"x", "y"}: 1,
+		{"y", "x"}: 2,
+		{"a", "z"}: 3,
+		{"z", "a"}: 4,
+	})
+	if err != nil {
+		t.Fatalf("Failed to Marshal text.Marshaler: %v", err)
+	}
+	const want = `{"a:z":3,"x:y":1,"y:x":2,"z:a":4}`
+	if string(b) != want {
+		t.Errorf("Marshal map with text.Marshaler keys: got %#q, want %#q", b, want)
+	}
+}
+
+// https://golang.org/issue/33675
+func TestNilMarshalerTextMapKey(t *testing.T) {
+	b, err := Marshal(map[*unmarshalerText]int{
+		(*unmarshalerText)(nil): 1,
+		{"A", "B"}:              2,
+	})
+	if err != nil {
+		t.Fatalf("Failed to Marshal *text.Marshaler: %v", err)
+	}
+	const want = `{"":1,"A:B":2}`
+	if string(b) != want {
+		t.Errorf("Marshal map with *text.Marshaler keys: got %#q, want %#q", b, want)
+	}
+}
+
+var re = regexp.MustCompile
+
+// syntactic checks on form of marshaled floating point numbers.
+var badFloatREs = []*regexp.Regexp{
+	re(`p`),                     // no binary exponential notation
+	re(`^\+`),                   // no leading + sign
+	re(`^-?0[^.]`),              // no unnecessary leading zeros
+	re(`^-?\.`),                 // leading zero required before decimal point
+	re(`\.(e|$)`),               // no trailing decimal
+	re(`\.[0-9]+0(e|$)`),        // no trailing zero in fraction
+	re(`^-?(0|[0-9]{2,})\..*e`), // exponential notation must have normalized mantissa
+	re(`e[0-9]`),                // positive exponent must be signed
+	re(`e[+-]0`),                // exponent must not have leading zeros
+	re(`e-[1-6]$`),              // not tiny enough for exponential notation
+	re(`e+(.|1.|20)$`),          // not big enough for exponential notation
+	re(`^-?0\.0000000`),         // too tiny, should use exponential notation
+	re(`^-?[0-9]{22}`),          // too big, should use exponential notation
+	re(`[1-9][0-9]{16}[1-9]`),   // too many significant digits in integer
+	re(`[1-9][0-9.]{17}[1-9]`),  // too many significant digits in decimal
+	// below here for float32 only
+	re(`[1-9][0-9]{8}[1-9]`),  // too many significant digits in integer
+	re(`[1-9][0-9.]{9}[1-9]`), // too many significant digits in decimal
+}
+
+func TestMarshalFloat(t *testing.T) {
+	t.Parallel()
+	nfail := 0
+	test := func(f float64, bits int) {
+		vf := any(f)
+		if bits == 32 {
+			f = float64(float32(f)) // round
+			vf = float32(f)
+		}
+		bout, err := Marshal(vf)
+		if err != nil {
+			t.Errorf("Marshal(%T(%g)): %v", vf, vf, err)
+			nfail++
+			return
+		}
+		out := string(bout)
+
+		// result must convert back to the same float
+		g, err := strconv.ParseFloat(out, bits)
+		if err != nil {
+			t.Errorf("Marshal(%T(%g)) = %q, cannot parse back: %v", vf, vf, out, err)
+			nfail++
+			return
+		}
+		if f != g || fmt.Sprint(f) != fmt.Sprint(g) { // fmt.Sprint handles ±0
+			t.Errorf("Marshal(%T(%g)) = %q (is %g, not %g)", vf, vf, out, float32(g), vf)
+			nfail++
+			return
+		}
+
+		bad := badFloatREs
+		if bits == 64 {
+			bad = bad[:len(bad)-2]
+		}
+		for _, re := range bad {
+			if re.MatchString(out) {
+				t.Errorf("Marshal(%T(%g)) = %q, must not match /%s/", vf, vf, out, re)
+				nfail++
+				return
+			}
+		}
+	}
+
+	var (
+		bigger  = math.Inf(+1)
+		smaller = math.Inf(-1)
+	)
+
+	var digits = "1.2345678901234567890123"
+	for i := len(digits); i >= 2; i-- {
+		if testing.Short() && i < len(digits)-4 {
+			break
+		}
+		for exp := -30; exp <= 30; exp++ {
+			for _, sign := range "+-" {
+				for bits := 32; bits <= 64; bits += 32 {
+					s := fmt.Sprintf("%c%se%d", sign, digits[:i], exp)
+					f, err := strconv.ParseFloat(s, bits)
+					if err != nil {
+						log.Fatal(err)
+					}
+					next := math.Nextafter
+					if bits == 32 {
+						next = func(g, h float64) float64 {
+							return float64(math.Nextafter32(float32(g), float32(h)))
+						}
+					}
+					test(f, bits)
+					test(next(f, bigger), bits)
+					test(next(f, smaller), bits)
+					if nfail > 50 {
+						t.Fatalf("stopping test early")
+					}
+				}
+			}
+		}
+	}
+	test(0, 64)
+	test(math.Copysign(0, -1), 64)
+	test(0, 32)
+	test(math.Copysign(0, -1), 32)
+}
+
+func TestMarshalRawMessageValue(t *testing.T) {
+	type (
+		T1 struct {
+			M RawMessage `json:",omitempty"`
+		}
+		T2 struct {
+			M *RawMessage `json:",omitempty"`
+		}
+	)
+
+	var (
+		rawNil   = RawMessage(nil)
+		rawEmpty = RawMessage([]byte{})
+		rawText  = RawMessage([]byte(`"foo"`))
+	)
+
+	tests := []struct {
+		in   any
+		want string
+		ok   bool
+	}{
+		// Test with nil RawMessage.
+		{rawNil, "null", true},
+		{&rawNil, "null", true},
+		{[]any{rawNil}, "[null]", true},
+		{&[]any{rawNil}, "[null]", true},
+		{[]any{&rawNil}, "[null]", true},
+		{&[]any{&rawNil}, "[null]", true},
+		{struct{ M RawMessage }{rawNil}, `{"M":null}`, true},
+		{&struct{ M RawMessage }{rawNil}, `{"M":null}`, true},
+		{struct{ M *RawMessage }{&rawNil}, `{"M":null}`, true},
+		{&struct{ M *RawMessage }{&rawNil}, `{"M":null}`, true},
+		{map[string]any{"M": rawNil}, `{"M":null}`, true},
+		{&map[string]any{"M": rawNil}, `{"M":null}`, true},
+		{map[string]any{"M": &rawNil}, `{"M":null}`, true},
+		{&map[string]any{"M": &rawNil}, `{"M":null}`, true},
+		{T1{rawNil}, "{}", true},
+		{T2{&rawNil}, `{"M":null}`, true},
+		{&T1{rawNil}, "{}", true},
+		{&T2{&rawNil}, `{"M":null}`, true},
+
+		// Test with empty, but non-nil, RawMessage.
+		{rawEmpty, "", false},
+		{&rawEmpty, "", false},
+		{[]any{rawEmpty}, "", false},
+		{&[]any{rawEmpty}, "", false},
+		{[]any{&rawEmpty}, "", false},
+		{&[]any{&rawEmpty}, "", false},
+		{struct{ X RawMessage }{rawEmpty}, "", false},
+		{&struct{ X RawMessage }{rawEmpty}, "", false},
+		{struct{ X *RawMessage }{&rawEmpty}, "", false},
+		{&struct{ X *RawMessage }{&rawEmpty}, "", false},
+		{map[string]any{"nil": rawEmpty}, "", false},
+		{&map[string]any{"nil": rawEmpty}, "", false},
+		{map[string]any{"nil": &rawEmpty}, "", false},
+		{&map[string]any{"nil": &rawEmpty}, "", false},
+		{T1{rawEmpty}, "{}", true},
+		{T2{&rawEmpty}, "", false},
+		{&T1{rawEmpty}, "{}", true},
+		{&T2{&rawEmpty}, "", false},
+
+		// Test with RawMessage with some text.
+		//
+		// The tests below marked with Issue6458 used to generate "ImZvbyI=" instead "foo".
+		// This behavior was intentionally changed in Go 1.8.
+		// See https://golang.org/issues/14493#issuecomment-255857318
+		{rawText, `"foo"`, true}, // Issue6458
+		{&rawText, `"foo"`, true},
+		{[]any{rawText}, `["foo"]`, true},  // Issue6458
+		{&[]any{rawText}, `["foo"]`, true}, // Issue6458
+		{[]any{&rawText}, `["foo"]`, true},
+		{&[]any{&rawText}, `["foo"]`, true},
+		{struct{ M RawMessage }{rawText}, `{"M":"foo"}`, true}, // Issue6458
+		{&struct{ M RawMessage }{rawText}, `{"M":"foo"}`, true},
+		{struct{ M *RawMessage }{&rawText}, `{"M":"foo"}`, true},
+		{&struct{ M *RawMessage }{&rawText}, `{"M":"foo"}`, true},
+		{map[string]any{"M": rawText}, `{"M":"foo"}`, true},  // Issue6458
+		{&map[string]any{"M": rawText}, `{"M":"foo"}`, true}, // Issue6458
+		{map[string]any{"M": &rawText}, `{"M":"foo"}`, true},
+		{&map[string]any{"M": &rawText}, `{"M":"foo"}`, true},
+		{T1{rawText}, `{"M":"foo"}`, true}, // Issue6458
+		{T2{&rawText}, `{"M":"foo"}`, true},
+		{&T1{rawText}, `{"M":"foo"}`, true},
+		{&T2{&rawText}, `{"M":"foo"}`, true},
+	}
+
+	for i, tt := range tests {
+		b, err := Marshal(tt.in)
+		if ok := (err == nil); ok != tt.ok {
+			if err != nil {
+				t.Errorf("test %d, unexpected failure: %v", i, err)
+			} else {
+				t.Errorf("test %d, unexpected success", i)
+			}
+		}
+		if got := string(b); got != tt.want {
+			t.Errorf("test %d, Marshal(%#v) = %q, want %q", i, tt.in, got, tt.want)
+		}
+	}
+}
+
+type marshalPanic struct{}
+
+func (marshalPanic) MarshalJSON() ([]byte, error) { panic(0xdead) }
+
+func TestMarshalPanic(t *testing.T) {
+	defer func() {
+		if got := recover(); !reflect.DeepEqual(got, 0xdead) {
+			t.Errorf("panic() = (%T)(%v), want 0xdead", got, got)
+		}
+	}()
+	Marshal(&marshalPanic{})
+	t.Error("Marshal should have panicked")
+}
+
+func TestMarshalUncommonFieldNames(t *testing.T) {
+	v := struct {
+		A0, À, Aβ int
+	}{}
+	b, err := Marshal(v)
+	if err != nil {
+		t.Fatal("Marshal:", err)
+	}
+	want := `{"A0":0,"À":0,"Aβ":0}`
+	got := string(b)
+	if got != want {
+		t.Fatalf("Marshal: got %s want %s", got, want)
+	}
+}
+
+func TestMarshalerError(t *testing.T) {
+	s := "test variable"
+	st := reflect.TypeOf(s)
+	errText := "json: test error"
+
+	tests := []struct {
+		err  *MarshalerError
+		want string
+	}{
+		{
+			&MarshalerError{st, fmt.Errorf(errText), ""},
+			"json: error calling MarshalJSON for type " + st.String() + ": " + errText,
+		},
+		{
+			&MarshalerError{st, fmt.Errorf(errText), "TestMarshalerError"},
+			"json: error calling TestMarshalerError for type " + st.String() + ": " + errText,
+		},
+	}
+
+	for i, tt := range tests {
+		got := tt.err.Error()
+		if got != tt.want {
+			t.Errorf("MarshalerError test %d, got: %s, want: %s", i, got, tt.want)
+		}
+	}
+}
diff --git a/src/encoding/json/example_marshaling_test.go b/src/encoding/json/example_marshaling_test.go
new file mode 100644
index 0000000..7f15c74
--- /dev/null
+++ b/src/encoding/json/example_marshaling_test.go
@@ -0,0 +1,73 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json_test
+
+import (
+	"encoding/json"
+	"fmt"
+	"log"
+	"strings"
+)
+
+type Animal int
+
+const (
+	Unknown Animal = iota
+	Gopher
+	Zebra
+)
+
+func (a *Animal) UnmarshalJSON(b []byte) error {
+	var s string
+	if err := json.Unmarshal(b, &s); err != nil {
+		return err
+	}
+	switch strings.ToLower(s) {
+	default:
+		*a = Unknown
+	case "gopher":
+		*a = Gopher
+	case "zebra":
+		*a = Zebra
+	}
+
+	return nil
+}
+
+func (a Animal) MarshalJSON() ([]byte, error) {
+	var s string
+	switch a {
+	default:
+		s = "unknown"
+	case Gopher:
+		s = "gopher"
+	case Zebra:
+		s = "zebra"
+	}
+
+	return json.Marshal(s)
+}
+
+func Example_customMarshalJSON() {
+	blob := `["gopher","armadillo","zebra","unknown","gopher","bee","gopher","zebra"]`
+	var zoo []Animal
+	if err := json.Unmarshal([]byte(blob), &zoo); err != nil {
+		log.Fatal(err)
+	}
+
+	census := make(map[Animal]int)
+	for _, animal := range zoo {
+		census[animal] += 1
+	}
+
+	fmt.Printf("Zoo Census:\n* Gophers: %d\n* Zebras:  %d\n* Unknown: %d\n",
+		census[Gopher], census[Zebra], census[Unknown])
+
+	// Output:
+	// Zoo Census:
+	// * Gophers: 3
+	// * Zebras:  2
+	// * Unknown: 3
+}
diff --git a/src/encoding/json/example_test.go b/src/encoding/json/example_test.go
new file mode 100644
index 0000000..2261c77
--- /dev/null
+++ b/src/encoding/json/example_test.go
@@ -0,0 +1,310 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json_test
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io"
+	"log"
+	"os"
+	"strings"
+)
+
+func ExampleMarshal() {
+	type ColorGroup struct {
+		ID     int
+		Name   string
+		Colors []string
+	}
+	group := ColorGroup{
+		ID:     1,
+		Name:   "Reds",
+		Colors: []string{"Crimson", "Red", "Ruby", "Maroon"},
+	}
+	b, err := json.Marshal(group)
+	if err != nil {
+		fmt.Println("error:", err)
+	}
+	os.Stdout.Write(b)
+	// Output:
+	// {"ID":1,"Name":"Reds","Colors":["Crimson","Red","Ruby","Maroon"]}
+}
+
+func ExampleUnmarshal() {
+	var jsonBlob = []byte(`[
+	{"Name": "Platypus", "Order": "Monotremata"},
+	{"Name": "Quoll",    "Order": "Dasyuromorphia"}
+]`)
+	type Animal struct {
+		Name  string
+		Order string
+	}
+	var animals []Animal
+	err := json.Unmarshal(jsonBlob, &animals)
+	if err != nil {
+		fmt.Println("error:", err)
+	}
+	fmt.Printf("%+v", animals)
+	// Output:
+	// [{Name:Platypus Order:Monotremata} {Name:Quoll Order:Dasyuromorphia}]
+}
+
+// This example uses a Decoder to decode a stream of distinct JSON values.
+func ExampleDecoder() {
+	const jsonStream = `
+	{"Name": "Ed", "Text": "Knock knock."}
+	{"Name": "Sam", "Text": "Who's there?"}
+	{"Name": "Ed", "Text": "Go fmt."}
+	{"Name": "Sam", "Text": "Go fmt who?"}
+	{"Name": "Ed", "Text": "Go fmt yourself!"}
+`
+	type Message struct {
+		Name, Text string
+	}
+	dec := json.NewDecoder(strings.NewReader(jsonStream))
+	for {
+		var m Message
+		if err := dec.Decode(&m); err == io.EOF {
+			break
+		} else if err != nil {
+			log.Fatal(err)
+		}
+		fmt.Printf("%s: %s\n", m.Name, m.Text)
+	}
+	// Output:
+	// Ed: Knock knock.
+	// Sam: Who's there?
+	// Ed: Go fmt.
+	// Sam: Go fmt who?
+	// Ed: Go fmt yourself!
+}
+
+// This example uses a Decoder to decode a stream of distinct JSON values.
+func ExampleDecoder_Token() {
+	const jsonStream = `
+	{"Message": "Hello", "Array": [1, 2, 3], "Null": null, "Number": 1.234}
+`
+	dec := json.NewDecoder(strings.NewReader(jsonStream))
+	for {
+		t, err := dec.Token()
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			log.Fatal(err)
+		}
+		fmt.Printf("%T: %v", t, t)
+		if dec.More() {
+			fmt.Printf(" (more)")
+		}
+		fmt.Printf("\n")
+	}
+	// Output:
+	// json.Delim: { (more)
+	// string: Message (more)
+	// string: Hello (more)
+	// string: Array (more)
+	// json.Delim: [ (more)
+	// float64: 1 (more)
+	// float64: 2 (more)
+	// float64: 3
+	// json.Delim: ] (more)
+	// string: Null (more)
+	// <nil>: <nil> (more)
+	// string: Number (more)
+	// float64: 1.234
+	// json.Delim: }
+}
+
+// This example uses a Decoder to decode a streaming array of JSON objects.
+func ExampleDecoder_Decode_stream() {
+	const jsonStream = `
+	[
+		{"Name": "Ed", "Text": "Knock knock."},
+		{"Name": "Sam", "Text": "Who's there?"},
+		{"Name": "Ed", "Text": "Go fmt."},
+		{"Name": "Sam", "Text": "Go fmt who?"},
+		{"Name": "Ed", "Text": "Go fmt yourself!"}
+	]
+`
+	type Message struct {
+		Name, Text string
+	}
+	dec := json.NewDecoder(strings.NewReader(jsonStream))
+
+	// read open bracket
+	t, err := dec.Token()
+	if err != nil {
+		log.Fatal(err)
+	}
+	fmt.Printf("%T: %v\n", t, t)
+
+	// while the array contains values
+	for dec.More() {
+		var m Message
+		// decode an array value (Message)
+		err := dec.Decode(&m)
+		if err != nil {
+			log.Fatal(err)
+		}
+
+		fmt.Printf("%v: %v\n", m.Name, m.Text)
+	}
+
+	// read closing bracket
+	t, err = dec.Token()
+	if err != nil {
+		log.Fatal(err)
+	}
+	fmt.Printf("%T: %v\n", t, t)
+
+	// Output:
+	// json.Delim: [
+	// Ed: Knock knock.
+	// Sam: Who's there?
+	// Ed: Go fmt.
+	// Sam: Go fmt who?
+	// Ed: Go fmt yourself!
+	// json.Delim: ]
+}
+
+// This example uses RawMessage to delay parsing part of a JSON message.
+func ExampleRawMessage_unmarshal() {
+	type Color struct {
+		Space string
+		Point json.RawMessage // delay parsing until we know the color space
+	}
+	type RGB struct {
+		R uint8
+		G uint8
+		B uint8
+	}
+	type YCbCr struct {
+		Y  uint8
+		Cb int8
+		Cr int8
+	}
+
+	var j = []byte(`[
+	{"Space": "YCbCr", "Point": {"Y": 255, "Cb": 0, "Cr": -10}},
+	{"Space": "RGB",   "Point": {"R": 98, "G": 218, "B": 255}}
+]`)
+	var colors []Color
+	err := json.Unmarshal(j, &colors)
+	if err != nil {
+		log.Fatalln("error:", err)
+	}
+
+	for _, c := range colors {
+		var dst any
+		switch c.Space {
+		case "RGB":
+			dst = new(RGB)
+		case "YCbCr":
+			dst = new(YCbCr)
+		}
+		err := json.Unmarshal(c.Point, dst)
+		if err != nil {
+			log.Fatalln("error:", err)
+		}
+		fmt.Println(c.Space, dst)
+	}
+	// Output:
+	// YCbCr &{255 0 -10}
+	// RGB &{98 218 255}
+}
+
+// This example uses RawMessage to use a precomputed JSON during marshal.
+func ExampleRawMessage_marshal() {
+	h := json.RawMessage(`{"precomputed": true}`)
+
+	c := struct {
+		Header *json.RawMessage `json:"header"`
+		Body   string           `json:"body"`
+	}{Header: &h, Body: "Hello Gophers!"}
+
+	b, err := json.MarshalIndent(&c, "", "\t")
+	if err != nil {
+		fmt.Println("error:", err)
+	}
+	os.Stdout.Write(b)
+
+	// Output:
+	// {
+	// 	"header": {
+	// 		"precomputed": true
+	// 	},
+	// 	"body": "Hello Gophers!"
+	// }
+}
+
+func ExampleIndent() {
+	type Road struct {
+		Name   string
+		Number int
+	}
+	roads := []Road{
+		{"Diamond Fork", 29},
+		{"Sheep Creek", 51},
+	}
+
+	b, err := json.Marshal(roads)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	var out bytes.Buffer
+	json.Indent(&out, b, "=", "\t")
+	out.WriteTo(os.Stdout)
+	// Output:
+	// [
+	// =	{
+	// =		"Name": "Diamond Fork",
+	// =		"Number": 29
+	// =	},
+	// =	{
+	// =		"Name": "Sheep Creek",
+	// =		"Number": 51
+	// =	}
+	// =]
+}
+
+func ExampleMarshalIndent() {
+	data := map[string]int{
+		"a": 1,
+		"b": 2,
+	}
+
+	b, err := json.MarshalIndent(data, "<prefix>", "<indent>")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	fmt.Println(string(b))
+	// Output:
+	// {
+	// <prefix><indent>"a": 1,
+	// <prefix><indent>"b": 2
+	// <prefix>}
+}
+
+func ExampleValid() {
+	goodJSON := `{"example": 1}`
+	badJSON := `{"example":2:]}}`
+
+	fmt.Println(json.Valid([]byte(goodJSON)), json.Valid([]byte(badJSON)))
+	// Output:
+	// true false
+}
+
+func ExampleHTMLEscape() {
+	var out bytes.Buffer
+	json.HTMLEscape(&out, []byte(`{"Name":"<b>HTML content</b>"}`))
+	out.WriteTo(os.Stdout)
+	// Output:
+	//{"Name":"\u003cb\u003eHTML content\u003c/b\u003e"}
+}
diff --git a/src/encoding/json/example_text_marshaling_test.go b/src/encoding/json/example_text_marshaling_test.go
new file mode 100644
index 0000000..04c7813
--- /dev/null
+++ b/src/encoding/json/example_text_marshaling_test.go
@@ -0,0 +1,67 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json_test
+
+import (
+	"encoding/json"
+	"fmt"
+	"log"
+	"strings"
+)
+
+type Size int
+
+const (
+	Unrecognized Size = iota
+	Small
+	Large
+)
+
+func (s *Size) UnmarshalText(text []byte) error {
+	switch strings.ToLower(string(text)) {
+	default:
+		*s = Unrecognized
+	case "small":
+		*s = Small
+	case "large":
+		*s = Large
+	}
+	return nil
+}
+
+func (s Size) MarshalText() ([]byte, error) {
+	var name string
+	switch s {
+	default:
+		name = "unrecognized"
+	case Small:
+		name = "small"
+	case Large:
+		name = "large"
+	}
+	return []byte(name), nil
+}
+
+func Example_textMarshalJSON() {
+	blob := `["small","regular","large","unrecognized","small","normal","small","large"]`
+	var inventory []Size
+	if err := json.Unmarshal([]byte(blob), &inventory); err != nil {
+		log.Fatal(err)
+	}
+
+	counts := make(map[Size]int)
+	for _, size := range inventory {
+		counts[size] += 1
+	}
+
+	fmt.Printf("Inventory Counts:\n* Small:        %d\n* Large:        %d\n* Unrecognized: %d\n",
+		counts[Small], counts[Large], counts[Unrecognized])
+
+	// Output:
+	// Inventory Counts:
+	// * Small:        3
+	// * Large:        2
+	// * Unrecognized: 3
+}
diff --git a/src/encoding/json/fold.go b/src/encoding/json/fold.go
new file mode 100644
index 0000000..9e17012
--- /dev/null
+++ b/src/encoding/json/fold.go
@@ -0,0 +1,143 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json
+
+import (
+	"bytes"
+	"unicode/utf8"
+)
+
+const (
+	caseMask     = ^byte(0x20) // Mask to ignore case in ASCII.
+	kelvin       = '\u212a'
+	smallLongEss = '\u017f'
+)
+
+// foldFunc returns one of four different case folding equivalence
+// functions, from most general (and slow) to fastest:
+//
+// 1) bytes.EqualFold, if the key s contains any non-ASCII UTF-8
+// 2) equalFoldRight, if s contains special folding ASCII ('k', 'K', 's', 'S')
+// 3) asciiEqualFold, no special, but includes non-letters (including _)
+// 4) simpleLetterEqualFold, no specials, no non-letters.
+//
+// The letters S and K are special because they map to 3 runes, not just 2:
+//  * S maps to s and to U+017F 'ſ' Latin small letter long s
+//  * k maps to K and to U+212A 'K' Kelvin sign
+// See https://play.golang.org/p/tTxjOc0OGo
+//
+// The returned function is specialized for matching against s and
+// should only be given s. It's not curried for performance reasons.
+func foldFunc(s []byte) func(s, t []byte) bool {
+	nonLetter := false
+	special := false // special letter
+	for _, b := range s {
+		if b >= utf8.RuneSelf {
+			return bytes.EqualFold
+		}
+		upper := b & caseMask
+		if upper < 'A' || upper > 'Z' {
+			nonLetter = true
+		} else if upper == 'K' || upper == 'S' {
+			// See above for why these letters are special.
+			special = true
+		}
+	}
+	if special {
+		return equalFoldRight
+	}
+	if nonLetter {
+		return asciiEqualFold
+	}
+	return simpleLetterEqualFold
+}
+
+// equalFoldRight is a specialization of bytes.EqualFold when s is
+// known to be all ASCII (including punctuation), but contains an 's',
+// 'S', 'k', or 'K', requiring a Unicode fold on the bytes in t.
+// See comments on foldFunc.
+func equalFoldRight(s, t []byte) bool {
+	for _, sb := range s {
+		if len(t) == 0 {
+			return false
+		}
+		tb := t[0]
+		if tb < utf8.RuneSelf {
+			if sb != tb {
+				sbUpper := sb & caseMask
+				if 'A' <= sbUpper && sbUpper <= 'Z' {
+					if sbUpper != tb&caseMask {
+						return false
+					}
+				} else {
+					return false
+				}
+			}
+			t = t[1:]
+			continue
+		}
+		// sb is ASCII and t is not. t must be either kelvin
+		// sign or long s; sb must be s, S, k, or K.
+		tr, size := utf8.DecodeRune(t)
+		switch sb {
+		case 's', 'S':
+			if tr != smallLongEss {
+				return false
+			}
+		case 'k', 'K':
+			if tr != kelvin {
+				return false
+			}
+		default:
+			return false
+		}
+		t = t[size:]
+
+	}
+	if len(t) > 0 {
+		return false
+	}
+	return true
+}
+
+// asciiEqualFold is a specialization of bytes.EqualFold for use when
+// s is all ASCII (but may contain non-letters) and contains no
+// special-folding letters.
+// See comments on foldFunc.
+func asciiEqualFold(s, t []byte) bool {
+	if len(s) != len(t) {
+		return false
+	}
+	for i, sb := range s {
+		tb := t[i]
+		if sb == tb {
+			continue
+		}
+		if ('a' <= sb && sb <= 'z') || ('A' <= sb && sb <= 'Z') {
+			if sb&caseMask != tb&caseMask {
+				return false
+			}
+		} else {
+			return false
+		}
+	}
+	return true
+}
+
+// simpleLetterEqualFold is a specialization of bytes.EqualFold for
+// use when s is all ASCII letters (no underscores, etc) and also
+// doesn't contain 'k', 'K', 's', or 'S'.
+// See comments on foldFunc.
+func simpleLetterEqualFold(s, t []byte) bool {
+	if len(s) != len(t) {
+		return false
+	}
+	for i, b := range s {
+		if b&caseMask != t[i]&caseMask {
+			return false
+		}
+	}
+	return true
+}
diff --git a/src/encoding/json/fold_test.go b/src/encoding/json/fold_test.go
new file mode 100644
index 0000000..9fb9464
--- /dev/null
+++ b/src/encoding/json/fold_test.go
@@ -0,0 +1,116 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json
+
+import (
+	"bytes"
+	"strings"
+	"testing"
+	"unicode/utf8"
+)
+
+var foldTests = []struct {
+	fn   func(s, t []byte) bool
+	s, t string
+	want bool
+}{
+	{equalFoldRight, "", "", true},
+	{equalFoldRight, "a", "a", true},
+	{equalFoldRight, "", "a", false},
+	{equalFoldRight, "a", "", false},
+	{equalFoldRight, "a", "A", true},
+	{equalFoldRight, "AB", "ab", true},
+	{equalFoldRight, "AB", "ac", false},
+	{equalFoldRight, "sbkKc", "ſbKKc", true},
+	{equalFoldRight, "SbKkc", "ſbKKc", true},
+	{equalFoldRight, "SbKkc", "ſbKK", false},
+	{equalFoldRight, "e", "é", false},
+	{equalFoldRight, "s", "S", true},
+
+	{simpleLetterEqualFold, "", "", true},
+	{simpleLetterEqualFold, "abc", "abc", true},
+	{simpleLetterEqualFold, "abc", "ABC", true},
+	{simpleLetterEqualFold, "abc", "ABCD", false},
+	{simpleLetterEqualFold, "abc", "xxx", false},
+
+	{asciiEqualFold, "a_B", "A_b", true},
+	{asciiEqualFold, "aa@", "aa`", false}, // verify 0x40 and 0x60 aren't case-equivalent
+}
+
+func TestFold(t *testing.T) {
+	for i, tt := range foldTests {
+		if got := tt.fn([]byte(tt.s), []byte(tt.t)); got != tt.want {
+			t.Errorf("%d. %q, %q = %v; want %v", i, tt.s, tt.t, got, tt.want)
+		}
+		truth := strings.EqualFold(tt.s, tt.t)
+		if truth != tt.want {
+			t.Errorf("strings.EqualFold doesn't agree with case %d", i)
+		}
+	}
+}
+
+func TestFoldAgainstUnicode(t *testing.T) {
+	const bufSize = 5
+	buf1 := make([]byte, 0, bufSize)
+	buf2 := make([]byte, 0, bufSize)
+	var runes []rune
+	for i := 0x20; i <= 0x7f; i++ {
+		runes = append(runes, rune(i))
+	}
+	runes = append(runes, kelvin, smallLongEss)
+
+	funcs := []struct {
+		name   string
+		fold   func(s, t []byte) bool
+		letter bool // must be ASCII letter
+		simple bool // must be simple ASCII letter (not 'S' or 'K')
+	}{
+		{
+			name: "equalFoldRight",
+			fold: equalFoldRight,
+		},
+		{
+			name:   "asciiEqualFold",
+			fold:   asciiEqualFold,
+			simple: true,
+		},
+		{
+			name:   "simpleLetterEqualFold",
+			fold:   simpleLetterEqualFold,
+			simple: true,
+			letter: true,
+		},
+	}
+
+	for _, ff := range funcs {
+		for _, r := range runes {
+			if r >= utf8.RuneSelf {
+				continue
+			}
+			if ff.letter && !isASCIILetter(byte(r)) {
+				continue
+			}
+			if ff.simple && (r == 's' || r == 'S' || r == 'k' || r == 'K') {
+				continue
+			}
+			for _, r2 := range runes {
+				buf1 := append(buf1[:0], 'x')
+				buf2 := append(buf2[:0], 'x')
+				buf1 = buf1[:1+utf8.EncodeRune(buf1[1:bufSize], r)]
+				buf2 = buf2[:1+utf8.EncodeRune(buf2[1:bufSize], r2)]
+				buf1 = append(buf1, 'x')
+				buf2 = append(buf2, 'x')
+				want := bytes.EqualFold(buf1, buf2)
+				if got := ff.fold(buf1, buf2); got != want {
+					t.Errorf("%s(%q, %q) = %v; want %v", ff.name, buf1, buf2, got, want)
+				}
+			}
+		}
+	}
+}
+
+func isASCIILetter(b byte) bool {
+	return ('A' <= b && b <= 'Z') || ('a' <= b && b <= 'z')
+}
diff --git a/src/encoding/json/fuzz.go b/src/encoding/json/fuzz.go
new file mode 100644
index 0000000..b8f4ff2
--- /dev/null
+++ b/src/encoding/json/fuzz.go
@@ -0,0 +1,42 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build gofuzz
+
+package json
+
+import (
+	"fmt"
+)
+
+func Fuzz(data []byte) (score int) {
+	for _, ctor := range []func() any{
+		func() any { return new(any) },
+		func() any { return new(map[string]any) },
+		func() any { return new([]any) },
+	} {
+		v := ctor()
+		err := Unmarshal(data, v)
+		if err != nil {
+			continue
+		}
+		score = 1
+
+		m, err := Marshal(v)
+		if err != nil {
+			fmt.Printf("v=%#v\n", v)
+			panic(err)
+		}
+
+		u := ctor()
+		err = Unmarshal(m, u)
+		if err != nil {
+			fmt.Printf("v=%#v\n", v)
+			fmt.Printf("m=%s\n", m)
+			panic(err)
+		}
+	}
+
+	return
+}
diff --git a/src/encoding/json/fuzz_test.go b/src/encoding/json/fuzz_test.go
new file mode 100644
index 0000000..778664c
--- /dev/null
+++ b/src/encoding/json/fuzz_test.go
@@ -0,0 +1,83 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json
+
+import (
+	"bytes"
+	"io"
+	"testing"
+)
+
+func FuzzUnmarshalJSON(f *testing.F) {
+	f.Add([]byte(`{
+"object": {
+	"slice": [
+		1,
+		2.0,
+		"3",
+		[4],
+		{5: {}}
+	]
+},
+"slice": [[]],
+"string": ":)",
+"int": 1e5,
+"float": 3e-9"
+}`))
+
+	f.Fuzz(func(t *testing.T, b []byte) {
+		for _, typ := range []func() interface{}{
+			func() interface{} { return new(interface{}) },
+			func() interface{} { return new(map[string]interface{}) },
+			func() interface{} { return new([]interface{}) },
+		} {
+			i := typ()
+			if err := Unmarshal(b, i); err != nil {
+				return
+			}
+
+			encoded, err := Marshal(i)
+			if err != nil {
+				t.Fatalf("failed to marshal: %s", err)
+			}
+
+			if err := Unmarshal(encoded, i); err != nil {
+				t.Fatalf("failed to roundtrip: %s", err)
+			}
+		}
+	})
+}
+
+func FuzzDecoderToken(f *testing.F) {
+	f.Add([]byte(`{
+"object": {
+	"slice": [
+		1,
+		2.0,
+		"3",
+		[4],
+		{5: {}}
+	]
+},
+"slice": [[]],
+"string": ":)",
+"int": 1e5,
+"float": 3e-9"
+}`))
+
+	f.Fuzz(func(t *testing.T, b []byte) {
+		r := bytes.NewReader(b)
+		d := NewDecoder(r)
+		for {
+			_, err := d.Token()
+			if err != nil {
+				if err == io.EOF {
+					break
+				}
+				return
+			}
+		}
+	})
+}
diff --git a/src/encoding/json/indent.go b/src/encoding/json/indent.go
new file mode 100644
index 0000000..2924d3b
--- /dev/null
+++ b/src/encoding/json/indent.go
@@ -0,0 +1,143 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json
+
+import (
+	"bytes"
+)
+
+// Compact appends to dst the JSON-encoded src with
+// insignificant space characters elided.
+func Compact(dst *bytes.Buffer, src []byte) error {
+	return compact(dst, src, false)
+}
+
+func compact(dst *bytes.Buffer, src []byte, escape bool) error {
+	origLen := dst.Len()
+	scan := newScanner()
+	defer freeScanner(scan)
+	start := 0
+	for i, c := range src {
+		if escape && (c == '<' || c == '>' || c == '&') {
+			if start < i {
+				dst.Write(src[start:i])
+			}
+			dst.WriteString(`\u00`)
+			dst.WriteByte(hex[c>>4])
+			dst.WriteByte(hex[c&0xF])
+			start = i + 1
+		}
+		// Convert U+2028 and U+2029 (E2 80 A8 and E2 80 A9).
+		if escape && c == 0xE2 && i+2 < len(src) && src[i+1] == 0x80 && src[i+2]&^1 == 0xA8 {
+			if start < i {
+				dst.Write(src[start:i])
+			}
+			dst.WriteString(`\u202`)
+			dst.WriteByte(hex[src[i+2]&0xF])
+			start = i + 3
+		}
+		v := scan.step(scan, c)
+		if v >= scanSkipSpace {
+			if v == scanError {
+				break
+			}
+			if start < i {
+				dst.Write(src[start:i])
+			}
+			start = i + 1
+		}
+	}
+	if scan.eof() == scanError {
+		dst.Truncate(origLen)
+		return scan.err
+	}
+	if start < len(src) {
+		dst.Write(src[start:])
+	}
+	return nil
+}
+
+func newline(dst *bytes.Buffer, prefix, indent string, depth int) {
+	dst.WriteByte('\n')
+	dst.WriteString(prefix)
+	for i := 0; i < depth; i++ {
+		dst.WriteString(indent)
+	}
+}
+
+// Indent appends to dst an indented form of the JSON-encoded src.
+// Each element in a JSON object or array begins on a new,
+// indented line beginning with prefix followed by one or more
+// copies of indent according to the indentation nesting.
+// The data appended to dst does not begin with the prefix nor
+// any indentation, to make it easier to embed inside other formatted JSON data.
+// Although leading space characters (space, tab, carriage return, newline)
+// at the beginning of src are dropped, trailing space characters
+// at the end of src are preserved and copied to dst.
+// For example, if src has no trailing spaces, neither will dst;
+// if src ends in a trailing newline, so will dst.
+func Indent(dst *bytes.Buffer, src []byte, prefix, indent string) error {
+	origLen := dst.Len()
+	scan := newScanner()
+	defer freeScanner(scan)
+	needIndent := false
+	depth := 0
+	for _, c := range src {
+		scan.bytes++
+		v := scan.step(scan, c)
+		if v == scanSkipSpace {
+			continue
+		}
+		if v == scanError {
+			break
+		}
+		if needIndent && v != scanEndObject && v != scanEndArray {
+			needIndent = false
+			depth++
+			newline(dst, prefix, indent, depth)
+		}
+
+		// Emit semantically uninteresting bytes
+		// (in particular, punctuation in strings) unmodified.
+		if v == scanContinue {
+			dst.WriteByte(c)
+			continue
+		}
+
+		// Add spacing around real punctuation.
+		switch c {
+		case '{', '[':
+			// delay indent so that empty object and array are formatted as {} and [].
+			needIndent = true
+			dst.WriteByte(c)
+
+		case ',':
+			dst.WriteByte(c)
+			newline(dst, prefix, indent, depth)
+
+		case ':':
+			dst.WriteByte(c)
+			dst.WriteByte(' ')
+
+		case '}', ']':
+			if needIndent {
+				// suppress indent in empty object/array
+				needIndent = false
+			} else {
+				depth--
+				newline(dst, prefix, indent, depth)
+			}
+			dst.WriteByte(c)
+
+		default:
+			dst.WriteByte(c)
+		}
+	}
+	if scan.eof() == scanError {
+		dst.Truncate(origLen)
+		return scan.err
+	}
+	return nil
+}
diff --git a/src/encoding/json/number_test.go b/src/encoding/json/number_test.go
new file mode 100644
index 0000000..cc67018
--- /dev/null
+++ b/src/encoding/json/number_test.go
@@ -0,0 +1,133 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json
+
+import (
+	"regexp"
+	"testing"
+)
+
+func TestNumberIsValid(t *testing.T) {
+	// From: https://stackoverflow.com/a/13340826
+	var jsonNumberRegexp = regexp.MustCompile(`^-?(?:0|[1-9]\d*)(?:\.\d+)?(?:[eE][+-]?\d+)?$`)
+
+	validTests := []string{
+		"0",
+		"-0",
+		"1",
+		"-1",
+		"0.1",
+		"-0.1",
+		"1234",
+		"-1234",
+		"12.34",
+		"-12.34",
+		"12E0",
+		"12E1",
+		"12e34",
+		"12E-0",
+		"12e+1",
+		"12e-34",
+		"-12E0",
+		"-12E1",
+		"-12e34",
+		"-12E-0",
+		"-12e+1",
+		"-12e-34",
+		"1.2E0",
+		"1.2E1",
+		"1.2e34",
+		"1.2E-0",
+		"1.2e+1",
+		"1.2e-34",
+		"-1.2E0",
+		"-1.2E1",
+		"-1.2e34",
+		"-1.2E-0",
+		"-1.2e+1",
+		"-1.2e-34",
+		"0E0",
+		"0E1",
+		"0e34",
+		"0E-0",
+		"0e+1",
+		"0e-34",
+		"-0E0",
+		"-0E1",
+		"-0e34",
+		"-0E-0",
+		"-0e+1",
+		"-0e-34",
+	}
+
+	for _, test := range validTests {
+		if !isValidNumber(test) {
+			t.Errorf("%s should be valid", test)
+		}
+
+		var f float64
+		if err := Unmarshal([]byte(test), &f); err != nil {
+			t.Errorf("%s should be valid but Unmarshal failed: %v", test, err)
+		}
+
+		if !jsonNumberRegexp.MatchString(test) {
+			t.Errorf("%s should be valid but regexp does not match", test)
+		}
+	}
+
+	invalidTests := []string{
+		"",
+		"invalid",
+		"1.0.1",
+		"1..1",
+		"-1-2",
+		"012a42",
+		"01.2",
+		"012",
+		"12E12.12",
+		"1e2e3",
+		"1e+-2",
+		"1e--23",
+		"1e",
+		"e1",
+		"1e+",
+		"1ea",
+		"1a",
+		"1.a",
+		"1.",
+		"01",
+		"1.e1",
+	}
+
+	for _, test := range invalidTests {
+		if isValidNumber(test) {
+			t.Errorf("%s should be invalid", test)
+		}
+
+		var f float64
+		if err := Unmarshal([]byte(test), &f); err == nil {
+			t.Errorf("%s should be invalid but unmarshal wrote %v", test, f)
+		}
+
+		if jsonNumberRegexp.MatchString(test) {
+			t.Errorf("%s should be invalid but matches regexp", test)
+		}
+	}
+}
+
+func BenchmarkNumberIsValid(b *testing.B) {
+	s := "-61657.61667E+61673"
+	for i := 0; i < b.N; i++ {
+		isValidNumber(s)
+	}
+}
+
+func BenchmarkNumberIsValidRegexp(b *testing.B) {
+	var jsonNumberRegexp = regexp.MustCompile(`^-?(?:0|[1-9]\d*)(?:\.\d+)?(?:[eE][+-]?\d+)?$`)
+	s := "-61657.61667E+61673"
+	for i := 0; i < b.N; i++ {
+		jsonNumberRegexp.MatchString(s)
+	}
+}
diff --git a/src/encoding/json/scanner.go b/src/encoding/json/scanner.go
new file mode 100644
index 0000000..dbaa821
--- /dev/null
+++ b/src/encoding/json/scanner.go
@@ -0,0 +1,608 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json
+
+// JSON value parser state machine.
+// Just about at the limit of what is reasonable to write by hand.
+// Some parts are a bit tedious, but overall it nicely factors out the
+// otherwise common code from the multiple scanning functions
+// in this package (Compact, Indent, checkValid, etc).
+//
+// This file starts with two simple examples using the scanner
+// before diving into the scanner itself.
+
+import (
+	"strconv"
+	"sync"
+)
+
+// Valid reports whether data is a valid JSON encoding.
+func Valid(data []byte) bool {
+	scan := newScanner()
+	defer freeScanner(scan)
+	return checkValid(data, scan) == nil
+}
+
+// checkValid verifies that data is valid JSON-encoded data.
+// scan is passed in for use by checkValid to avoid an allocation.
+func checkValid(data []byte, scan *scanner) error {
+	scan.reset()
+	for _, c := range data {
+		scan.bytes++
+		if scan.step(scan, c) == scanError {
+			return scan.err
+		}
+	}
+	if scan.eof() == scanError {
+		return scan.err
+	}
+	return nil
+}
+
+// A SyntaxError is a description of a JSON syntax error.
+type SyntaxError struct {
+	msg    string // description of error
+	Offset int64  // error occurred after reading Offset bytes
+}
+
+func (e *SyntaxError) Error() string { return e.msg }
+
+// A scanner is a JSON scanning state machine.
+// Callers call scan.reset and then pass bytes in one at a time
+// by calling scan.step(&scan, c) for each byte.
+// The return value, referred to as an opcode, tells the
+// caller about significant parsing events like beginning
+// and ending literals, objects, and arrays, so that the
+// caller can follow along if it wishes.
+// The return value scanEnd indicates that a single top-level
+// JSON value has been completed, *before* the byte that
+// just got passed in.  (The indication must be delayed in order
+// to recognize the end of numbers: is 123 a whole value or
+// the beginning of 12345e+6?).
+type scanner struct {
+	// The step is a func to be called to execute the next transition.
+	// Also tried using an integer constant and a single func
+	// with a switch, but using the func directly was 10% faster
+	// on a 64-bit Mac Mini, and it's nicer to read.
+	step func(*scanner, byte) int
+
+	// Reached end of top-level value.
+	endTop bool
+
+	// Stack of what we're in the middle of - array values, object keys, object values.
+	parseState []int
+
+	// Error that happened, if any.
+	err error
+
+	// total bytes consumed, updated by decoder.Decode (and deliberately
+	// not set to zero by scan.reset)
+	bytes int64
+}
+
+var scannerPool = sync.Pool{
+	New: func() any {
+		return &scanner{}
+	},
+}
+
+func newScanner() *scanner {
+	scan := scannerPool.Get().(*scanner)
+	// scan.reset by design doesn't set bytes to zero
+	scan.bytes = 0
+	scan.reset()
+	return scan
+}
+
+func freeScanner(scan *scanner) {
+	// Avoid hanging on to too much memory in extreme cases.
+	if len(scan.parseState) > 1024 {
+		scan.parseState = nil
+	}
+	scannerPool.Put(scan)
+}
+
+// These values are returned by the state transition functions
+// assigned to scanner.state and the method scanner.eof.
+// They give details about the current state of the scan that
+// callers might be interested to know about.
+// It is okay to ignore the return value of any particular
+// call to scanner.state: if one call returns scanError,
+// every subsequent call will return scanError too.
+const (
+	// Continue.
+	scanContinue     = iota // uninteresting byte
+	scanBeginLiteral        // end implied by next result != scanContinue
+	scanBeginObject         // begin object
+	scanObjectKey           // just finished object key (string)
+	scanObjectValue         // just finished non-last object value
+	scanEndObject           // end object (implies scanObjectValue if possible)
+	scanBeginArray          // begin array
+	scanArrayValue          // just finished array value
+	scanEndArray            // end array (implies scanArrayValue if possible)
+	scanSkipSpace           // space byte; can skip; known to be last "continue" result
+
+	// Stop.
+	scanEnd   // top-level value ended *before* this byte; known to be first "stop" result
+	scanError // hit an error, scanner.err.
+)
+
+// These values are stored in the parseState stack.
+// They give the current state of a composite value
+// being scanned. If the parser is inside a nested value
+// the parseState describes the nested state, outermost at entry 0.
+const (
+	parseObjectKey   = iota // parsing object key (before colon)
+	parseObjectValue        // parsing object value (after colon)
+	parseArrayValue         // parsing array value
+)
+
+// This limits the max nesting depth to prevent stack overflow.
+// This is permitted by https://tools.ietf.org/html/rfc7159#section-9
+const maxNestingDepth = 10000
+
+// reset prepares the scanner for use.
+// It must be called before calling s.step.
+func (s *scanner) reset() {
+	s.step = stateBeginValue
+	s.parseState = s.parseState[0:0]
+	s.err = nil
+	s.endTop = false
+}
+
+// eof tells the scanner that the end of input has been reached.
+// It returns a scan status just as s.step does.
+func (s *scanner) eof() int {
+	if s.err != nil {
+		return scanError
+	}
+	if s.endTop {
+		return scanEnd
+	}
+	s.step(s, ' ')
+	if s.endTop {
+		return scanEnd
+	}
+	if s.err == nil {
+		s.err = &SyntaxError{"unexpected end of JSON input", s.bytes}
+	}
+	return scanError
+}
+
+// pushParseState pushes a new parse state p onto the parse stack.
+// an error state is returned if maxNestingDepth was exceeded, otherwise successState is returned.
+func (s *scanner) pushParseState(c byte, newParseState int, successState int) int {
+	s.parseState = append(s.parseState, newParseState)
+	if len(s.parseState) <= maxNestingDepth {
+		return successState
+	}
+	return s.error(c, "exceeded max depth")
+}
+
+// popParseState pops a parse state (already obtained) off the stack
+// and updates s.step accordingly.
+func (s *scanner) popParseState() {
+	n := len(s.parseState) - 1
+	s.parseState = s.parseState[0:n]
+	if n == 0 {
+		s.step = stateEndTop
+		s.endTop = true
+	} else {
+		s.step = stateEndValue
+	}
+}
+
+func isSpace(c byte) bool {
+	return c <= ' ' && (c == ' ' || c == '\t' || c == '\r' || c == '\n')
+}
+
+// stateBeginValueOrEmpty is the state after reading `[`.
+func stateBeginValueOrEmpty(s *scanner, c byte) int {
+	if isSpace(c) {
+		return scanSkipSpace
+	}
+	if c == ']' {
+		return stateEndValue(s, c)
+	}
+	return stateBeginValue(s, c)
+}
+
+// stateBeginValue is the state at the beginning of the input.
+func stateBeginValue(s *scanner, c byte) int {
+	if isSpace(c) {
+		return scanSkipSpace
+	}
+	switch c {
+	case '{':
+		s.step = stateBeginStringOrEmpty
+		return s.pushParseState(c, parseObjectKey, scanBeginObject)
+	case '[':
+		s.step = stateBeginValueOrEmpty
+		return s.pushParseState(c, parseArrayValue, scanBeginArray)
+	case '"':
+		s.step = stateInString
+		return scanBeginLiteral
+	case '-':
+		s.step = stateNeg
+		return scanBeginLiteral
+	case '0': // beginning of 0.123
+		s.step = state0
+		return scanBeginLiteral
+	case 't': // beginning of true
+		s.step = stateT
+		return scanBeginLiteral
+	case 'f': // beginning of false
+		s.step = stateF
+		return scanBeginLiteral
+	case 'n': // beginning of null
+		s.step = stateN
+		return scanBeginLiteral
+	}
+	if '1' <= c && c <= '9' { // beginning of 1234.5
+		s.step = state1
+		return scanBeginLiteral
+	}
+	return s.error(c, "looking for beginning of value")
+}
+
+// stateBeginStringOrEmpty is the state after reading `{`.
+func stateBeginStringOrEmpty(s *scanner, c byte) int {
+	if isSpace(c) {
+		return scanSkipSpace
+	}
+	if c == '}' {
+		n := len(s.parseState)
+		s.parseState[n-1] = parseObjectValue
+		return stateEndValue(s, c)
+	}
+	return stateBeginString(s, c)
+}
+
+// stateBeginString is the state after reading `{"key": value,`.
+func stateBeginString(s *scanner, c byte) int {
+	if isSpace(c) {
+		return scanSkipSpace
+	}
+	if c == '"' {
+		s.step = stateInString
+		return scanBeginLiteral
+	}
+	return s.error(c, "looking for beginning of object key string")
+}
+
+// stateEndValue is the state after completing a value,
+// such as after reading `{}` or `true` or `["x"`.
+func stateEndValue(s *scanner, c byte) int {
+	n := len(s.parseState)
+	if n == 0 {
+		// Completed top-level before the current byte.
+		s.step = stateEndTop
+		s.endTop = true
+		return stateEndTop(s, c)
+	}
+	if isSpace(c) {
+		s.step = stateEndValue
+		return scanSkipSpace
+	}
+	ps := s.parseState[n-1]
+	switch ps {
+	case parseObjectKey:
+		if c == ':' {
+			s.parseState[n-1] = parseObjectValue
+			s.step = stateBeginValue
+			return scanObjectKey
+		}
+		return s.error(c, "after object key")
+	case parseObjectValue:
+		if c == ',' {
+			s.parseState[n-1] = parseObjectKey
+			s.step = stateBeginString
+			return scanObjectValue
+		}
+		if c == '}' {
+			s.popParseState()
+			return scanEndObject
+		}
+		return s.error(c, "after object key:value pair")
+	case parseArrayValue:
+		if c == ',' {
+			s.step = stateBeginValue
+			return scanArrayValue
+		}
+		if c == ']' {
+			s.popParseState()
+			return scanEndArray
+		}
+		return s.error(c, "after array element")
+	}
+	return s.error(c, "")
+}
+
+// stateEndTop is the state after finishing the top-level value,
+// such as after reading `{}` or `[1,2,3]`.
+// Only space characters should be seen now.
+func stateEndTop(s *scanner, c byte) int {
+	if !isSpace(c) {
+		// Complain about non-space byte on next call.
+		s.error(c, "after top-level value")
+	}
+	return scanEnd
+}
+
+// stateInString is the state after reading `"`.
+func stateInString(s *scanner, c byte) int {
+	if c == '"' {
+		s.step = stateEndValue
+		return scanContinue
+	}
+	if c == '\\' {
+		s.step = stateInStringEsc
+		return scanContinue
+	}
+	if c < 0x20 {
+		return s.error(c, "in string literal")
+	}
+	return scanContinue
+}
+
+// stateInStringEsc is the state after reading `"\` during a quoted string.
+func stateInStringEsc(s *scanner, c byte) int {
+	switch c {
+	case 'b', 'f', 'n', 'r', 't', '\\', '/', '"':
+		s.step = stateInString
+		return scanContinue
+	case 'u':
+		s.step = stateInStringEscU
+		return scanContinue
+	}
+	return s.error(c, "in string escape code")
+}
+
+// stateInStringEscU is the state after reading `"\u` during a quoted string.
+func stateInStringEscU(s *scanner, c byte) int {
+	if '0' <= c && c <= '9' || 'a' <= c && c <= 'f' || 'A' <= c && c <= 'F' {
+		s.step = stateInStringEscU1
+		return scanContinue
+	}
+	// numbers
+	return s.error(c, "in \\u hexadecimal character escape")
+}
+
+// stateInStringEscU1 is the state after reading `"\u1` during a quoted string.
+func stateInStringEscU1(s *scanner, c byte) int {
+	if '0' <= c && c <= '9' || 'a' <= c && c <= 'f' || 'A' <= c && c <= 'F' {
+		s.step = stateInStringEscU12
+		return scanContinue
+	}
+	// numbers
+	return s.error(c, "in \\u hexadecimal character escape")
+}
+
+// stateInStringEscU12 is the state after reading `"\u12` during a quoted string.
+func stateInStringEscU12(s *scanner, c byte) int {
+	if '0' <= c && c <= '9' || 'a' <= c && c <= 'f' || 'A' <= c && c <= 'F' {
+		s.step = stateInStringEscU123
+		return scanContinue
+	}
+	// numbers
+	return s.error(c, "in \\u hexadecimal character escape")
+}
+
+// stateInStringEscU123 is the state after reading `"\u123` during a quoted string.
+func stateInStringEscU123(s *scanner, c byte) int {
+	if '0' <= c && c <= '9' || 'a' <= c && c <= 'f' || 'A' <= c && c <= 'F' {
+		s.step = stateInString
+		return scanContinue
+	}
+	// numbers
+	return s.error(c, "in \\u hexadecimal character escape")
+}
+
+// stateNeg is the state after reading `-` during a number.
+func stateNeg(s *scanner, c byte) int {
+	if c == '0' {
+		s.step = state0
+		return scanContinue
+	}
+	if '1' <= c && c <= '9' {
+		s.step = state1
+		return scanContinue
+	}
+	return s.error(c, "in numeric literal")
+}
+
+// state1 is the state after reading a non-zero integer during a number,
+// such as after reading `1` or `100` but not `0`.
+func state1(s *scanner, c byte) int {
+	if '0' <= c && c <= '9' {
+		s.step = state1
+		return scanContinue
+	}
+	return state0(s, c)
+}
+
+// state0 is the state after reading `0` during a number.
+func state0(s *scanner, c byte) int {
+	if c == '.' {
+		s.step = stateDot
+		return scanContinue
+	}
+	if c == 'e' || c == 'E' {
+		s.step = stateE
+		return scanContinue
+	}
+	return stateEndValue(s, c)
+}
+
+// stateDot is the state after reading the integer and decimal point in a number,
+// such as after reading `1.`.
+func stateDot(s *scanner, c byte) int {
+	if '0' <= c && c <= '9' {
+		s.step = stateDot0
+		return scanContinue
+	}
+	return s.error(c, "after decimal point in numeric literal")
+}
+
+// stateDot0 is the state after reading the integer, decimal point, and subsequent
+// digits of a number, such as after reading `3.14`.
+func stateDot0(s *scanner, c byte) int {
+	if '0' <= c && c <= '9' {
+		return scanContinue
+	}
+	if c == 'e' || c == 'E' {
+		s.step = stateE
+		return scanContinue
+	}
+	return stateEndValue(s, c)
+}
+
+// stateE is the state after reading the mantissa and e in a number,
+// such as after reading `314e` or `0.314e`.
+func stateE(s *scanner, c byte) int {
+	if c == '+' || c == '-' {
+		s.step = stateESign
+		return scanContinue
+	}
+	return stateESign(s, c)
+}
+
+// stateESign is the state after reading the mantissa, e, and sign in a number,
+// such as after reading `314e-` or `0.314e+`.
+func stateESign(s *scanner, c byte) int {
+	if '0' <= c && c <= '9' {
+		s.step = stateE0
+		return scanContinue
+	}
+	return s.error(c, "in exponent of numeric literal")
+}
+
+// stateE0 is the state after reading the mantissa, e, optional sign,
+// and at least one digit of the exponent in a number,
+// such as after reading `314e-2` or `0.314e+1` or `3.14e0`.
+func stateE0(s *scanner, c byte) int {
+	if '0' <= c && c <= '9' {
+		return scanContinue
+	}
+	return stateEndValue(s, c)
+}
+
+// stateT is the state after reading `t`.
+func stateT(s *scanner, c byte) int {
+	if c == 'r' {
+		s.step = stateTr
+		return scanContinue
+	}
+	return s.error(c, "in literal true (expecting 'r')")
+}
+
+// stateTr is the state after reading `tr`.
+func stateTr(s *scanner, c byte) int {
+	if c == 'u' {
+		s.step = stateTru
+		return scanContinue
+	}
+	return s.error(c, "in literal true (expecting 'u')")
+}
+
+// stateTru is the state after reading `tru`.
+func stateTru(s *scanner, c byte) int {
+	if c == 'e' {
+		s.step = stateEndValue
+		return scanContinue
+	}
+	return s.error(c, "in literal true (expecting 'e')")
+}
+
+// stateF is the state after reading `f`.
+func stateF(s *scanner, c byte) int {
+	if c == 'a' {
+		s.step = stateFa
+		return scanContinue
+	}
+	return s.error(c, "in literal false (expecting 'a')")
+}
+
+// stateFa is the state after reading `fa`.
+func stateFa(s *scanner, c byte) int {
+	if c == 'l' {
+		s.step = stateFal
+		return scanContinue
+	}
+	return s.error(c, "in literal false (expecting 'l')")
+}
+
+// stateFal is the state after reading `fal`.
+func stateFal(s *scanner, c byte) int {
+	if c == 's' {
+		s.step = stateFals
+		return scanContinue
+	}
+	return s.error(c, "in literal false (expecting 's')")
+}
+
+// stateFals is the state after reading `fals`.
+func stateFals(s *scanner, c byte) int {
+	if c == 'e' {
+		s.step = stateEndValue
+		return scanContinue
+	}
+	return s.error(c, "in literal false (expecting 'e')")
+}
+
+// stateN is the state after reading `n`.
+func stateN(s *scanner, c byte) int {
+	if c == 'u' {
+		s.step = stateNu
+		return scanContinue
+	}
+	return s.error(c, "in literal null (expecting 'u')")
+}
+
+// stateNu is the state after reading `nu`.
+func stateNu(s *scanner, c byte) int {
+	if c == 'l' {
+		s.step = stateNul
+		return scanContinue
+	}
+	return s.error(c, "in literal null (expecting 'l')")
+}
+
+// stateNul is the state after reading `nul`.
+func stateNul(s *scanner, c byte) int {
+	if c == 'l' {
+		s.step = stateEndValue
+		return scanContinue
+	}
+	return s.error(c, "in literal null (expecting 'l')")
+}
+
+// stateError is the state after reaching a syntax error,
+// such as after reading `[1}` or `5.1.2`.
+func stateError(s *scanner, c byte) int {
+	return scanError
+}
+
+// error records an error and switches to the error state.
+func (s *scanner) error(c byte, context string) int {
+	s.step = stateError
+	s.err = &SyntaxError{"invalid character " + quoteChar(c) + " " + context, s.bytes}
+	return scanError
+}
+
+// quoteChar formats c as a quoted character literal
+func quoteChar(c byte) string {
+	// special cases - different from quoted strings
+	if c == '\'' {
+		return `'\''`
+	}
+	if c == '"' {
+		return `'"'`
+	}
+
+	// use quoted string with different quotation marks
+	s := strconv.Quote(string(c))
+	return "'" + s[1:len(s)-1] + "'"
+}
diff --git a/src/encoding/json/scanner_test.go b/src/encoding/json/scanner_test.go
new file mode 100644
index 0000000..3474b3e
--- /dev/null
+++ b/src/encoding/json/scanner_test.go
@@ -0,0 +1,301 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json
+
+import (
+	"bytes"
+	"math"
+	"math/rand"
+	"reflect"
+	"testing"
+)
+
+var validTests = []struct {
+	data string
+	ok   bool
+}{
+	{`foo`, false},
+	{`}{`, false},
+	{`{]`, false},
+	{`{}`, true},
+	{`{"foo":"bar"}`, true},
+	{`{"foo":"bar","bar":{"baz":["qux"]}}`, true},
+}
+
+func TestValid(t *testing.T) {
+	for _, tt := range validTests {
+		if ok := Valid([]byte(tt.data)); ok != tt.ok {
+			t.Errorf("Valid(%#q) = %v, want %v", tt.data, ok, tt.ok)
+		}
+	}
+}
+
+// Tests of simple examples.
+
+type example struct {
+	compact string
+	indent  string
+}
+
+var examples = []example{
+	{`1`, `1`},
+	{`{}`, `{}`},
+	{`[]`, `[]`},
+	{`{"":2}`, "{\n\t\"\": 2\n}"},
+	{`[3]`, "[\n\t3\n]"},
+	{`[1,2,3]`, "[\n\t1,\n\t2,\n\t3\n]"},
+	{`{"x":1}`, "{\n\t\"x\": 1\n}"},
+	{ex1, ex1i},
+	{"{\"\":\"<>&\u2028\u2029\"}", "{\n\t\"\": \"<>&\u2028\u2029\"\n}"}, // See golang.org/issue/34070
+}
+
+var ex1 = `[true,false,null,"x",1,1.5,0,-5e+2]`
+
+var ex1i = `[
+	true,
+	false,
+	null,
+	"x",
+	1,
+	1.5,
+	0,
+	-5e+2
+]`
+
+func TestCompact(t *testing.T) {
+	var buf bytes.Buffer
+	for _, tt := range examples {
+		buf.Reset()
+		if err := Compact(&buf, []byte(tt.compact)); err != nil {
+			t.Errorf("Compact(%#q): %v", tt.compact, err)
+		} else if s := buf.String(); s != tt.compact {
+			t.Errorf("Compact(%#q) = %#q, want original", tt.compact, s)
+		}
+
+		buf.Reset()
+		if err := Compact(&buf, []byte(tt.indent)); err != nil {
+			t.Errorf("Compact(%#q): %v", tt.indent, err)
+			continue
+		} else if s := buf.String(); s != tt.compact {
+			t.Errorf("Compact(%#q) = %#q, want %#q", tt.indent, s, tt.compact)
+		}
+	}
+}
+
+func TestCompactSeparators(t *testing.T) {
+	// U+2028 and U+2029 should be escaped inside strings.
+	// They should not appear outside strings.
+	tests := []struct {
+		in, compact string
+	}{
+		{"{\"\u2028\": 1}", "{\"\u2028\":1}"},
+		{"{\"\u2029\" :2}", "{\"\u2029\":2}"},
+	}
+	for _, tt := range tests {
+		var buf bytes.Buffer
+		if err := Compact(&buf, []byte(tt.in)); err != nil {
+			t.Errorf("Compact(%q): %v", tt.in, err)
+		} else if s := buf.String(); s != tt.compact {
+			t.Errorf("Compact(%q) = %q, want %q", tt.in, s, tt.compact)
+		}
+	}
+}
+
+func TestIndent(t *testing.T) {
+	var buf bytes.Buffer
+	for _, tt := range examples {
+		buf.Reset()
+		if err := Indent(&buf, []byte(tt.indent), "", "\t"); err != nil {
+			t.Errorf("Indent(%#q): %v", tt.indent, err)
+		} else if s := buf.String(); s != tt.indent {
+			t.Errorf("Indent(%#q) = %#q, want original", tt.indent, s)
+		}
+
+		buf.Reset()
+		if err := Indent(&buf, []byte(tt.compact), "", "\t"); err != nil {
+			t.Errorf("Indent(%#q): %v", tt.compact, err)
+			continue
+		} else if s := buf.String(); s != tt.indent {
+			t.Errorf("Indent(%#q) = %#q, want %#q", tt.compact, s, tt.indent)
+		}
+	}
+}
+
+// Tests of a large random structure.
+
+func TestCompactBig(t *testing.T) {
+	initBig()
+	var buf bytes.Buffer
+	if err := Compact(&buf, jsonBig); err != nil {
+		t.Fatalf("Compact: %v", err)
+	}
+	b := buf.Bytes()
+	if !bytes.Equal(b, jsonBig) {
+		t.Error("Compact(jsonBig) != jsonBig")
+		diff(t, b, jsonBig)
+		return
+	}
+}
+
+func TestIndentBig(t *testing.T) {
+	t.Parallel()
+	initBig()
+	var buf bytes.Buffer
+	if err := Indent(&buf, jsonBig, "", "\t"); err != nil {
+		t.Fatalf("Indent1: %v", err)
+	}
+	b := buf.Bytes()
+	if len(b) == len(jsonBig) {
+		// jsonBig is compact (no unnecessary spaces);
+		// indenting should make it bigger
+		t.Fatalf("Indent(jsonBig) did not get bigger")
+	}
+
+	// should be idempotent
+	var buf1 bytes.Buffer
+	if err := Indent(&buf1, b, "", "\t"); err != nil {
+		t.Fatalf("Indent2: %v", err)
+	}
+	b1 := buf1.Bytes()
+	if !bytes.Equal(b1, b) {
+		t.Error("Indent(Indent(jsonBig)) != Indent(jsonBig)")
+		diff(t, b1, b)
+		return
+	}
+
+	// should get back to original
+	buf1.Reset()
+	if err := Compact(&buf1, b); err != nil {
+		t.Fatalf("Compact: %v", err)
+	}
+	b1 = buf1.Bytes()
+	if !bytes.Equal(b1, jsonBig) {
+		t.Error("Compact(Indent(jsonBig)) != jsonBig")
+		diff(t, b1, jsonBig)
+		return
+	}
+}
+
+type indentErrorTest struct {
+	in  string
+	err error
+}
+
+var indentErrorTests = []indentErrorTest{
+	{`{"X": "foo", "Y"}`, &SyntaxError{"invalid character '}' after object key", 17}},
+	{`{"X": "foo" "Y": "bar"}`, &SyntaxError{"invalid character '\"' after object key:value pair", 13}},
+}
+
+func TestIndentErrors(t *testing.T) {
+	for i, tt := range indentErrorTests {
+		slice := make([]uint8, 0)
+		buf := bytes.NewBuffer(slice)
+		if err := Indent(buf, []uint8(tt.in), "", ""); err != nil {
+			if !reflect.DeepEqual(err, tt.err) {
+				t.Errorf("#%d: Indent: %#v", i, err)
+				continue
+			}
+		}
+	}
+}
+
+func diff(t *testing.T, a, b []byte) {
+	for i := 0; ; i++ {
+		if i >= len(a) || i >= len(b) || a[i] != b[i] {
+			j := i - 10
+			if j < 0 {
+				j = 0
+			}
+			t.Errorf("diverge at %d: «%s» vs «%s»", i, trim(a[j:]), trim(b[j:]))
+			return
+		}
+	}
+}
+
+func trim(b []byte) []byte {
+	if len(b) > 20 {
+		return b[0:20]
+	}
+	return b
+}
+
+// Generate a random JSON object.
+
+var jsonBig []byte
+
+func initBig() {
+	n := 10000
+	if testing.Short() {
+		n = 100
+	}
+	b, err := Marshal(genValue(n))
+	if err != nil {
+		panic(err)
+	}
+	jsonBig = b
+}
+
+func genValue(n int) any {
+	if n > 1 {
+		switch rand.Intn(2) {
+		case 0:
+			return genArray(n)
+		case 1:
+			return genMap(n)
+		}
+	}
+	switch rand.Intn(3) {
+	case 0:
+		return rand.Intn(2) == 0
+	case 1:
+		return rand.NormFloat64()
+	case 2:
+		return genString(30)
+	}
+	panic("unreachable")
+}
+
+func genString(stddev float64) string {
+	n := int(math.Abs(rand.NormFloat64()*stddev + stddev/2))
+	c := make([]rune, n)
+	for i := range c {
+		f := math.Abs(rand.NormFloat64()*64 + 32)
+		if f > 0x10ffff {
+			f = 0x10ffff
+		}
+		c[i] = rune(f)
+	}
+	return string(c)
+}
+
+func genArray(n int) []any {
+	f := int(math.Abs(rand.NormFloat64()) * math.Min(10, float64(n/2)))
+	if f > n {
+		f = n
+	}
+	if f < 1 {
+		f = 1
+	}
+	x := make([]any, f)
+	for i := range x {
+		x[i] = genValue(((i+1)*n)/f - (i*n)/f)
+	}
+	return x
+}
+
+func genMap(n int) map[string]any {
+	f := int(math.Abs(rand.NormFloat64()) * math.Min(10, float64(n/2)))
+	if f > n {
+		f = n
+	}
+	if n > 0 && f == 0 {
+		f = 1
+	}
+	x := make(map[string]any)
+	for i := 0; i < f; i++ {
+		x[genString(10)] = genValue(((i+1)*n)/f - (i*n)/f)
+	}
+	return x
+}
diff --git a/src/encoding/json/stream.go b/src/encoding/json/stream.go
new file mode 100644
index 0000000..6362170
--- /dev/null
+++ b/src/encoding/json/stream.go
@@ -0,0 +1,514 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json
+
+import (
+	"bytes"
+	"errors"
+	"io"
+)
+
+// A Decoder reads and decodes JSON values from an input stream.
+type Decoder struct {
+	r       io.Reader
+	buf     []byte
+	d       decodeState
+	scanp   int   // start of unread data in buf
+	scanned int64 // amount of data already scanned
+	scan    scanner
+	err     error
+
+	tokenState int
+	tokenStack []int
+}
+
+// NewDecoder returns a new decoder that reads from r.
+//
+// The decoder introduces its own buffering and may
+// read data from r beyond the JSON values requested.
+func NewDecoder(r io.Reader) *Decoder {
+	return &Decoder{r: r}
+}
+
+// UseNumber causes the Decoder to unmarshal a number into an interface{} as a
+// Number instead of as a float64.
+func (dec *Decoder) UseNumber() { dec.d.useNumber = true }
+
+// DisallowUnknownFields causes the Decoder to return an error when the destination
+// is a struct and the input contains object keys which do not match any
+// non-ignored, exported fields in the destination.
+func (dec *Decoder) DisallowUnknownFields() { dec.d.disallowUnknownFields = true }
+
+// Decode reads the next JSON-encoded value from its
+// input and stores it in the value pointed to by v.
+//
+// See the documentation for Unmarshal for details about
+// the conversion of JSON into a Go value.
+func (dec *Decoder) Decode(v any) error {
+	if dec.err != nil {
+		return dec.err
+	}
+
+	if err := dec.tokenPrepareForDecode(); err != nil {
+		return err
+	}
+
+	if !dec.tokenValueAllowed() {
+		return &SyntaxError{msg: "not at beginning of value", Offset: dec.InputOffset()}
+	}
+
+	// Read whole value into buffer.
+	n, err := dec.readValue()
+	if err != nil {
+		return err
+	}
+	dec.d.init(dec.buf[dec.scanp : dec.scanp+n])
+	dec.scanp += n
+
+	// Don't save err from unmarshal into dec.err:
+	// the connection is still usable since we read a complete JSON
+	// object from it before the error happened.
+	err = dec.d.unmarshal(v)
+
+	// fixup token streaming state
+	dec.tokenValueEnd()
+
+	return err
+}
+
+// Buffered returns a reader of the data remaining in the Decoder's
+// buffer. The reader is valid until the next call to Decode.
+func (dec *Decoder) Buffered() io.Reader {
+	return bytes.NewReader(dec.buf[dec.scanp:])
+}
+
+// readValue reads a JSON value into dec.buf.
+// It returns the length of the encoding.
+func (dec *Decoder) readValue() (int, error) {
+	dec.scan.reset()
+
+	scanp := dec.scanp
+	var err error
+Input:
+	// help the compiler see that scanp is never negative, so it can remove
+	// some bounds checks below.
+	for scanp >= 0 {
+
+		// Look in the buffer for a new value.
+		for ; scanp < len(dec.buf); scanp++ {
+			c := dec.buf[scanp]
+			dec.scan.bytes++
+			switch dec.scan.step(&dec.scan, c) {
+			case scanEnd:
+				// scanEnd is delayed one byte so we decrement
+				// the scanner bytes count by 1 to ensure that
+				// this value is correct in the next call of Decode.
+				dec.scan.bytes--
+				break Input
+			case scanEndObject, scanEndArray:
+				// scanEnd is delayed one byte.
+				// We might block trying to get that byte from src,
+				// so instead invent a space byte.
+				if stateEndValue(&dec.scan, ' ') == scanEnd {
+					scanp++
+					break Input
+				}
+			case scanError:
+				dec.err = dec.scan.err
+				return 0, dec.scan.err
+			}
+		}
+
+		// Did the last read have an error?
+		// Delayed until now to allow buffer scan.
+		if err != nil {
+			if err == io.EOF {
+				if dec.scan.step(&dec.scan, ' ') == scanEnd {
+					break Input
+				}
+				if nonSpace(dec.buf) {
+					err = io.ErrUnexpectedEOF
+				}
+			}
+			dec.err = err
+			return 0, err
+		}
+
+		n := scanp - dec.scanp
+		err = dec.refill()
+		scanp = dec.scanp + n
+	}
+	return scanp - dec.scanp, nil
+}
+
+func (dec *Decoder) refill() error {
+	// Make room to read more into the buffer.
+	// First slide down data already consumed.
+	if dec.scanp > 0 {
+		dec.scanned += int64(dec.scanp)
+		n := copy(dec.buf, dec.buf[dec.scanp:])
+		dec.buf = dec.buf[:n]
+		dec.scanp = 0
+	}
+
+	// Grow buffer if not large enough.
+	const minRead = 512
+	if cap(dec.buf)-len(dec.buf) < minRead {
+		newBuf := make([]byte, len(dec.buf), 2*cap(dec.buf)+minRead)
+		copy(newBuf, dec.buf)
+		dec.buf = newBuf
+	}
+
+	// Read. Delay error for next iteration (after scan).
+	n, err := dec.r.Read(dec.buf[len(dec.buf):cap(dec.buf)])
+	dec.buf = dec.buf[0 : len(dec.buf)+n]
+
+	return err
+}
+
+func nonSpace(b []byte) bool {
+	for _, c := range b {
+		if !isSpace(c) {
+			return true
+		}
+	}
+	return false
+}
+
+// An Encoder writes JSON values to an output stream.
+type Encoder struct {
+	w          io.Writer
+	err        error
+	escapeHTML bool
+
+	indentBuf    *bytes.Buffer
+	indentPrefix string
+	indentValue  string
+}
+
+// NewEncoder returns a new encoder that writes to w.
+func NewEncoder(w io.Writer) *Encoder {
+	return &Encoder{w: w, escapeHTML: true}
+}
+
+// Encode writes the JSON encoding of v to the stream,
+// followed by a newline character.
+//
+// See the documentation for Marshal for details about the
+// conversion of Go values to JSON.
+func (enc *Encoder) Encode(v any) error {
+	if enc.err != nil {
+		return enc.err
+	}
+	e := newEncodeState()
+	err := e.marshal(v, encOpts{escapeHTML: enc.escapeHTML})
+	if err != nil {
+		return err
+	}
+
+	// Terminate each value with a newline.
+	// This makes the output look a little nicer
+	// when debugging, and some kind of space
+	// is required if the encoded value was a number,
+	// so that the reader knows there aren't more
+	// digits coming.
+	e.WriteByte('\n')
+
+	b := e.Bytes()
+	if enc.indentPrefix != "" || enc.indentValue != "" {
+		if enc.indentBuf == nil {
+			enc.indentBuf = new(bytes.Buffer)
+		}
+		enc.indentBuf.Reset()
+		err = Indent(enc.indentBuf, b, enc.indentPrefix, enc.indentValue)
+		if err != nil {
+			return err
+		}
+		b = enc.indentBuf.Bytes()
+	}
+	if _, err = enc.w.Write(b); err != nil {
+		enc.err = err
+	}
+	encodeStatePool.Put(e)
+	return err
+}
+
+// SetIndent instructs the encoder to format each subsequent encoded
+// value as if indented by the package-level function Indent(dst, src, prefix, indent).
+// Calling SetIndent("", "") disables indentation.
+func (enc *Encoder) SetIndent(prefix, indent string) {
+	enc.indentPrefix = prefix
+	enc.indentValue = indent
+}
+
+// SetEscapeHTML specifies whether problematic HTML characters
+// should be escaped inside JSON quoted strings.
+// The default behavior is to escape &, <, and > to \u0026, \u003c, and \u003e
+// to avoid certain safety problems that can arise when embedding JSON in HTML.
+//
+// In non-HTML settings where the escaping interferes with the readability
+// of the output, SetEscapeHTML(false) disables this behavior.
+func (enc *Encoder) SetEscapeHTML(on bool) {
+	enc.escapeHTML = on
+}
+
+// RawMessage is a raw encoded JSON value.
+// It implements Marshaler and Unmarshaler and can
+// be used to delay JSON decoding or precompute a JSON encoding.
+type RawMessage []byte
+
+// MarshalJSON returns m as the JSON encoding of m.
+func (m RawMessage) MarshalJSON() ([]byte, error) {
+	if m == nil {
+		return []byte("null"), nil
+	}
+	return m, nil
+}
+
+// UnmarshalJSON sets *m to a copy of data.
+func (m *RawMessage) UnmarshalJSON(data []byte) error {
+	if m == nil {
+		return errors.New("json.RawMessage: UnmarshalJSON on nil pointer")
+	}
+	*m = append((*m)[0:0], data...)
+	return nil
+}
+
+var _ Marshaler = (*RawMessage)(nil)
+var _ Unmarshaler = (*RawMessage)(nil)
+
+// A Token holds a value of one of these types:
+//
+//	Delim, for the four JSON delimiters [ ] { }
+//	bool, for JSON booleans
+//	float64, for JSON numbers
+//	Number, for JSON numbers
+//	string, for JSON string literals
+//	nil, for JSON null
+//
+type Token any
+
+const (
+	tokenTopValue = iota
+	tokenArrayStart
+	tokenArrayValue
+	tokenArrayComma
+	tokenObjectStart
+	tokenObjectKey
+	tokenObjectColon
+	tokenObjectValue
+	tokenObjectComma
+)
+
+// advance tokenstate from a separator state to a value state
+func (dec *Decoder) tokenPrepareForDecode() error {
+	// Note: Not calling peek before switch, to avoid
+	// putting peek into the standard Decode path.
+	// peek is only called when using the Token API.
+	switch dec.tokenState {
+	case tokenArrayComma:
+		c, err := dec.peek()
+		if err != nil {
+			return err
+		}
+		if c != ',' {
+			return &SyntaxError{"expected comma after array element", dec.InputOffset()}
+		}
+		dec.scanp++
+		dec.tokenState = tokenArrayValue
+	case tokenObjectColon:
+		c, err := dec.peek()
+		if err != nil {
+			return err
+		}
+		if c != ':' {
+			return &SyntaxError{"expected colon after object key", dec.InputOffset()}
+		}
+		dec.scanp++
+		dec.tokenState = tokenObjectValue
+	}
+	return nil
+}
+
+func (dec *Decoder) tokenValueAllowed() bool {
+	switch dec.tokenState {
+	case tokenTopValue, tokenArrayStart, tokenArrayValue, tokenObjectValue:
+		return true
+	}
+	return false
+}
+
+func (dec *Decoder) tokenValueEnd() {
+	switch dec.tokenState {
+	case tokenArrayStart, tokenArrayValue:
+		dec.tokenState = tokenArrayComma
+	case tokenObjectValue:
+		dec.tokenState = tokenObjectComma
+	}
+}
+
+// A Delim is a JSON array or object delimiter, one of [ ] { or }.
+type Delim rune
+
+func (d Delim) String() string {
+	return string(d)
+}
+
+// Token returns the next JSON token in the input stream.
+// At the end of the input stream, Token returns nil, io.EOF.
+//
+// Token guarantees that the delimiters [ ] { } it returns are
+// properly nested and matched: if Token encounters an unexpected
+// delimiter in the input, it will return an error.
+//
+// The input stream consists of basic JSON values—bool, string,
+// number, and null—along with delimiters [ ] { } of type Delim
+// to mark the start and end of arrays and objects.
+// Commas and colons are elided.
+func (dec *Decoder) Token() (Token, error) {
+	for {
+		c, err := dec.peek()
+		if err != nil {
+			return nil, err
+		}
+		switch c {
+		case '[':
+			if !dec.tokenValueAllowed() {
+				return dec.tokenError(c)
+			}
+			dec.scanp++
+			dec.tokenStack = append(dec.tokenStack, dec.tokenState)
+			dec.tokenState = tokenArrayStart
+			return Delim('['), nil
+
+		case ']':
+			if dec.tokenState != tokenArrayStart && dec.tokenState != tokenArrayComma {
+				return dec.tokenError(c)
+			}
+			dec.scanp++
+			dec.tokenState = dec.tokenStack[len(dec.tokenStack)-1]
+			dec.tokenStack = dec.tokenStack[:len(dec.tokenStack)-1]
+			dec.tokenValueEnd()
+			return Delim(']'), nil
+
+		case '{':
+			if !dec.tokenValueAllowed() {
+				return dec.tokenError(c)
+			}
+			dec.scanp++
+			dec.tokenStack = append(dec.tokenStack, dec.tokenState)
+			dec.tokenState = tokenObjectStart
+			return Delim('{'), nil
+
+		case '}':
+			if dec.tokenState != tokenObjectStart && dec.tokenState != tokenObjectComma {
+				return dec.tokenError(c)
+			}
+			dec.scanp++
+			dec.tokenState = dec.tokenStack[len(dec.tokenStack)-1]
+			dec.tokenStack = dec.tokenStack[:len(dec.tokenStack)-1]
+			dec.tokenValueEnd()
+			return Delim('}'), nil
+
+		case ':':
+			if dec.tokenState != tokenObjectColon {
+				return dec.tokenError(c)
+			}
+			dec.scanp++
+			dec.tokenState = tokenObjectValue
+			continue
+
+		case ',':
+			if dec.tokenState == tokenArrayComma {
+				dec.scanp++
+				dec.tokenState = tokenArrayValue
+				continue
+			}
+			if dec.tokenState == tokenObjectComma {
+				dec.scanp++
+				dec.tokenState = tokenObjectKey
+				continue
+			}
+			return dec.tokenError(c)
+
+		case '"':
+			if dec.tokenState == tokenObjectStart || dec.tokenState == tokenObjectKey {
+				var x string
+				old := dec.tokenState
+				dec.tokenState = tokenTopValue
+				err := dec.Decode(&x)
+				dec.tokenState = old
+				if err != nil {
+					return nil, err
+				}
+				dec.tokenState = tokenObjectColon
+				return x, nil
+			}
+			fallthrough
+
+		default:
+			if !dec.tokenValueAllowed() {
+				return dec.tokenError(c)
+			}
+			var x any
+			if err := dec.Decode(&x); err != nil {
+				return nil, err
+			}
+			return x, nil
+		}
+	}
+}
+
+func (dec *Decoder) tokenError(c byte) (Token, error) {
+	var context string
+	switch dec.tokenState {
+	case tokenTopValue:
+		context = " looking for beginning of value"
+	case tokenArrayStart, tokenArrayValue, tokenObjectValue:
+		context = " looking for beginning of value"
+	case tokenArrayComma:
+		context = " after array element"
+	case tokenObjectKey:
+		context = " looking for beginning of object key string"
+	case tokenObjectColon:
+		context = " after object key"
+	case tokenObjectComma:
+		context = " after object key:value pair"
+	}
+	return nil, &SyntaxError{"invalid character " + quoteChar(c) + context, dec.InputOffset()}
+}
+
+// More reports whether there is another element in the
+// current array or object being parsed.
+func (dec *Decoder) More() bool {
+	c, err := dec.peek()
+	return err == nil && c != ']' && c != '}'
+}
+
+func (dec *Decoder) peek() (byte, error) {
+	var err error
+	for {
+		for i := dec.scanp; i < len(dec.buf); i++ {
+			c := dec.buf[i]
+			if isSpace(c) {
+				continue
+			}
+			dec.scanp = i
+			return c, nil
+		}
+		// buffer has been scanned, now report any error
+		if err != nil {
+			return 0, err
+		}
+		err = dec.refill()
+	}
+}
+
+// InputOffset returns the input stream byte offset of the current decoder position.
+// The offset gives the location of the end of the most recently returned token
+// and the beginning of the next token.
+func (dec *Decoder) InputOffset() int64 {
+	return dec.scanned + int64(dec.scanp)
+}
diff --git a/src/encoding/json/stream_test.go b/src/encoding/json/stream_test.go
new file mode 100644
index 0000000..0e156d9
--- /dev/null
+++ b/src/encoding/json/stream_test.go
@@ -0,0 +1,474 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json
+
+import (
+	"bytes"
+	"io"
+	"log"
+	"net"
+	"net/http"
+	"net/http/httptest"
+	"reflect"
+	"strings"
+	"testing"
+)
+
+// Test values for the stream test.
+// One of each JSON kind.
+var streamTest = []any{
+	0.1,
+	"hello",
+	nil,
+	true,
+	false,
+	[]any{"a", "b", "c"},
+	map[string]any{"K": "Kelvin", "ß": "long s"},
+	3.14, // another value to make sure something can follow map
+}
+
+var streamEncoded = `0.1
+"hello"
+null
+true
+false
+["a","b","c"]
+{"ß":"long s","K":"Kelvin"}
+3.14
+`
+
+func TestEncoder(t *testing.T) {
+	for i := 0; i <= len(streamTest); i++ {
+		var buf bytes.Buffer
+		enc := NewEncoder(&buf)
+		// Check that enc.SetIndent("", "") turns off indentation.
+		enc.SetIndent(">", ".")
+		enc.SetIndent("", "")
+		for j, v := range streamTest[0:i] {
+			if err := enc.Encode(v); err != nil {
+				t.Fatalf("encode #%d: %v", j, err)
+			}
+		}
+		if have, want := buf.String(), nlines(streamEncoded, i); have != want {
+			t.Errorf("encoding %d items: mismatch", i)
+			diff(t, []byte(have), []byte(want))
+			break
+		}
+	}
+}
+
+var streamEncodedIndent = `0.1
+"hello"
+null
+true
+false
+[
+>."a",
+>."b",
+>."c"
+>]
+{
+>."ß": "long s",
+>."K": "Kelvin"
+>}
+3.14
+`
+
+func TestEncoderIndent(t *testing.T) {
+	var buf bytes.Buffer
+	enc := NewEncoder(&buf)
+	enc.SetIndent(">", ".")
+	for _, v := range streamTest {
+		enc.Encode(v)
+	}
+	if have, want := buf.String(), streamEncodedIndent; have != want {
+		t.Error("indented encoding mismatch")
+		diff(t, []byte(have), []byte(want))
+	}
+}
+
+type strMarshaler string
+
+func (s strMarshaler) MarshalJSON() ([]byte, error) {
+	return []byte(s), nil
+}
+
+type strPtrMarshaler string
+
+func (s *strPtrMarshaler) MarshalJSON() ([]byte, error) {
+	return []byte(*s), nil
+}
+
+func TestEncoderSetEscapeHTML(t *testing.T) {
+	var c C
+	var ct CText
+	var tagStruct struct {
+		Valid   int `json:"<>&#! "`
+		Invalid int `json:"\\"`
+	}
+
+	// This case is particularly interesting, as we force the encoder to
+	// take the address of the Ptr field to use its MarshalJSON method. This
+	// is why the '&' is important.
+	marshalerStruct := &struct {
+		NonPtr strMarshaler
+		Ptr    strPtrMarshaler
+	}{`"<str>"`, `"<str>"`}
+
+	// https://golang.org/issue/34154
+	stringOption := struct {
+		Bar string `json:"bar,string"`
+	}{`<html>foobar</html>`}
+
+	for _, tt := range []struct {
+		name       string
+		v          any
+		wantEscape string
+		want       string
+	}{
+		{"c", c, `"\u003c\u0026\u003e"`, `"<&>"`},
+		{"ct", ct, `"\"\u003c\u0026\u003e\""`, `"\"<&>\""`},
+		{`"<&>"`, "<&>", `"\u003c\u0026\u003e"`, `"<&>"`},
+		{
+			"tagStruct", tagStruct,
+			`{"\u003c\u003e\u0026#! ":0,"Invalid":0}`,
+			`{"<>&#! ":0,"Invalid":0}`,
+		},
+		{
+			`"<str>"`, marshalerStruct,
+			`{"NonPtr":"\u003cstr\u003e","Ptr":"\u003cstr\u003e"}`,
+			`{"NonPtr":"<str>","Ptr":"<str>"}`,
+		},
+		{
+			"stringOption", stringOption,
+			`{"bar":"\"\\u003chtml\\u003efoobar\\u003c/html\\u003e\""}`,
+			`{"bar":"\"<html>foobar</html>\""}`,
+		},
+	} {
+		var buf bytes.Buffer
+		enc := NewEncoder(&buf)
+		if err := enc.Encode(tt.v); err != nil {
+			t.Errorf("Encode(%s): %s", tt.name, err)
+			continue
+		}
+		if got := strings.TrimSpace(buf.String()); got != tt.wantEscape {
+			t.Errorf("Encode(%s) = %#q, want %#q", tt.name, got, tt.wantEscape)
+		}
+		buf.Reset()
+		enc.SetEscapeHTML(false)
+		if err := enc.Encode(tt.v); err != nil {
+			t.Errorf("SetEscapeHTML(false) Encode(%s): %s", tt.name, err)
+			continue
+		}
+		if got := strings.TrimSpace(buf.String()); got != tt.want {
+			t.Errorf("SetEscapeHTML(false) Encode(%s) = %#q, want %#q",
+				tt.name, got, tt.want)
+		}
+	}
+}
+
+func TestDecoder(t *testing.T) {
+	for i := 0; i <= len(streamTest); i++ {
+		// Use stream without newlines as input,
+		// just to stress the decoder even more.
+		// Our test input does not include back-to-back numbers.
+		// Otherwise stripping the newlines would
+		// merge two adjacent JSON values.
+		var buf bytes.Buffer
+		for _, c := range nlines(streamEncoded, i) {
+			if c != '\n' {
+				buf.WriteRune(c)
+			}
+		}
+		out := make([]any, i)
+		dec := NewDecoder(&buf)
+		for j := range out {
+			if err := dec.Decode(&out[j]); err != nil {
+				t.Fatalf("decode #%d/%d: %v", j, i, err)
+			}
+		}
+		if !reflect.DeepEqual(out, streamTest[0:i]) {
+			t.Errorf("decoding %d items: mismatch", i)
+			for j := range out {
+				if !reflect.DeepEqual(out[j], streamTest[j]) {
+					t.Errorf("#%d: have %v want %v", j, out[j], streamTest[j])
+				}
+			}
+			break
+		}
+	}
+}
+
+func TestDecoderBuffered(t *testing.T) {
+	r := strings.NewReader(`{"Name": "Gopher"} extra `)
+	var m struct {
+		Name string
+	}
+	d := NewDecoder(r)
+	err := d.Decode(&m)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if m.Name != "Gopher" {
+		t.Errorf("Name = %q; want Gopher", m.Name)
+	}
+	rest, err := io.ReadAll(d.Buffered())
+	if err != nil {
+		t.Fatal(err)
+	}
+	if g, w := string(rest), " extra "; g != w {
+		t.Errorf("Remaining = %q; want %q", g, w)
+	}
+}
+
+func nlines(s string, n int) string {
+	if n <= 0 {
+		return ""
+	}
+	for i, c := range s {
+		if c == '\n' {
+			if n--; n == 0 {
+				return s[0 : i+1]
+			}
+		}
+	}
+	return s
+}
+
+func TestRawMessage(t *testing.T) {
+	var data struct {
+		X  float64
+		Id RawMessage
+		Y  float32
+	}
+	const raw = `["\u0056",null]`
+	const msg = `{"X":0.1,"Id":["\u0056",null],"Y":0.2}`
+	err := Unmarshal([]byte(msg), &data)
+	if err != nil {
+		t.Fatalf("Unmarshal: %v", err)
+	}
+	if string([]byte(data.Id)) != raw {
+		t.Fatalf("Raw mismatch: have %#q want %#q", []byte(data.Id), raw)
+	}
+	b, err := Marshal(&data)
+	if err != nil {
+		t.Fatalf("Marshal: %v", err)
+	}
+	if string(b) != msg {
+		t.Fatalf("Marshal: have %#q want %#q", b, msg)
+	}
+}
+
+func TestNullRawMessage(t *testing.T) {
+	var data struct {
+		X     float64
+		Id    RawMessage
+		IdPtr *RawMessage
+		Y     float32
+	}
+	const msg = `{"X":0.1,"Id":null,"IdPtr":null,"Y":0.2}`
+	err := Unmarshal([]byte(msg), &data)
+	if err != nil {
+		t.Fatalf("Unmarshal: %v", err)
+	}
+	if want, got := "null", string(data.Id); want != got {
+		t.Fatalf("Raw mismatch: have %q, want %q", got, want)
+	}
+	if data.IdPtr != nil {
+		t.Fatalf("Raw pointer mismatch: have non-nil, want nil")
+	}
+	b, err := Marshal(&data)
+	if err != nil {
+		t.Fatalf("Marshal: %v", err)
+	}
+	if string(b) != msg {
+		t.Fatalf("Marshal: have %#q want %#q", b, msg)
+	}
+}
+
+var blockingTests = []string{
+	`{"x": 1}`,
+	`[1, 2, 3]`,
+}
+
+func TestBlocking(t *testing.T) {
+	for _, enc := range blockingTests {
+		r, w := net.Pipe()
+		go w.Write([]byte(enc))
+		var val any
+
+		// If Decode reads beyond what w.Write writes above,
+		// it will block, and the test will deadlock.
+		if err := NewDecoder(r).Decode(&val); err != nil {
+			t.Errorf("decoding %s: %v", enc, err)
+		}
+		r.Close()
+		w.Close()
+	}
+}
+
+func BenchmarkEncoderEncode(b *testing.B) {
+	b.ReportAllocs()
+	type T struct {
+		X, Y string
+	}
+	v := &T{"foo", "bar"}
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			if err := NewEncoder(io.Discard).Encode(v); err != nil {
+				b.Fatal(err)
+			}
+		}
+	})
+}
+
+type tokenStreamCase struct {
+	json      string
+	expTokens []any
+}
+
+type decodeThis struct {
+	v any
+}
+
+var tokenStreamCases = []tokenStreamCase{
+	// streaming token cases
+	{json: `10`, expTokens: []any{float64(10)}},
+	{json: ` [10] `, expTokens: []any{
+		Delim('['), float64(10), Delim(']')}},
+	{json: ` [false,10,"b"] `, expTokens: []any{
+		Delim('['), false, float64(10), "b", Delim(']')}},
+	{json: `{ "a": 1 }`, expTokens: []any{
+		Delim('{'), "a", float64(1), Delim('}')}},
+	{json: `{"a": 1, "b":"3"}`, expTokens: []any{
+		Delim('{'), "a", float64(1), "b", "3", Delim('}')}},
+	{json: ` [{"a": 1},{"a": 2}] `, expTokens: []any{
+		Delim('['),
+		Delim('{'), "a", float64(1), Delim('}'),
+		Delim('{'), "a", float64(2), Delim('}'),
+		Delim(']')}},
+	{json: `{"obj": {"a": 1}}`, expTokens: []any{
+		Delim('{'), "obj", Delim('{'), "a", float64(1), Delim('}'),
+		Delim('}')}},
+	{json: `{"obj": [{"a": 1}]}`, expTokens: []any{
+		Delim('{'), "obj", Delim('['),
+		Delim('{'), "a", float64(1), Delim('}'),
+		Delim(']'), Delim('}')}},
+
+	// streaming tokens with intermittent Decode()
+	{json: `{ "a": 1 }`, expTokens: []any{
+		Delim('{'), "a",
+		decodeThis{float64(1)},
+		Delim('}')}},
+	{json: ` [ { "a" : 1 } ] `, expTokens: []any{
+		Delim('['),
+		decodeThis{map[string]any{"a": float64(1)}},
+		Delim(']')}},
+	{json: ` [{"a": 1},{"a": 2}] `, expTokens: []any{
+		Delim('['),
+		decodeThis{map[string]any{"a": float64(1)}},
+		decodeThis{map[string]any{"a": float64(2)}},
+		Delim(']')}},
+	{json: `{ "obj" : [ { "a" : 1 } ] }`, expTokens: []any{
+		Delim('{'), "obj", Delim('['),
+		decodeThis{map[string]any{"a": float64(1)}},
+		Delim(']'), Delim('}')}},
+
+	{json: `{"obj": {"a": 1}}`, expTokens: []any{
+		Delim('{'), "obj",
+		decodeThis{map[string]any{"a": float64(1)}},
+		Delim('}')}},
+	{json: `{"obj": [{"a": 1}]}`, expTokens: []any{
+		Delim('{'), "obj",
+		decodeThis{[]any{
+			map[string]any{"a": float64(1)},
+		}},
+		Delim('}')}},
+	{json: ` [{"a": 1} {"a": 2}] `, expTokens: []any{
+		Delim('['),
+		decodeThis{map[string]any{"a": float64(1)}},
+		decodeThis{&SyntaxError{"expected comma after array element", 11}},
+	}},
+	{json: `{ "` + strings.Repeat("a", 513) + `" 1 }`, expTokens: []any{
+		Delim('{'), strings.Repeat("a", 513),
+		decodeThis{&SyntaxError{"expected colon after object key", 518}},
+	}},
+	{json: `{ "\a" }`, expTokens: []any{
+		Delim('{'),
+		&SyntaxError{"invalid character 'a' in string escape code", 3},
+	}},
+	{json: ` \a`, expTokens: []any{
+		&SyntaxError{"invalid character '\\\\' looking for beginning of value", 1},
+	}},
+}
+
+func TestDecodeInStream(t *testing.T) {
+	for ci, tcase := range tokenStreamCases {
+
+		dec := NewDecoder(strings.NewReader(tcase.json))
+		for i, etk := range tcase.expTokens {
+
+			var tk any
+			var err error
+
+			if dt, ok := etk.(decodeThis); ok {
+				etk = dt.v
+				err = dec.Decode(&tk)
+			} else {
+				tk, err = dec.Token()
+			}
+			if experr, ok := etk.(error); ok {
+				if err == nil || !reflect.DeepEqual(err, experr) {
+					t.Errorf("case %v: Expected error %#v in %q, but was %#v", ci, experr, tcase.json, err)
+				}
+				break
+			} else if err == io.EOF {
+				t.Errorf("case %v: Unexpected EOF in %q", ci, tcase.json)
+				break
+			} else if err != nil {
+				t.Errorf("case %v: Unexpected error '%#v' in %q", ci, err, tcase.json)
+				break
+			}
+			if !reflect.DeepEqual(tk, etk) {
+				t.Errorf(`case %v: %q @ %v expected %T(%v) was %T(%v)`, ci, tcase.json, i, etk, etk, tk, tk)
+				break
+			}
+		}
+	}
+}
+
+// Test from golang.org/issue/11893
+func TestHTTPDecoding(t *testing.T) {
+	const raw = `{ "foo": "bar" }`
+
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Write([]byte(raw))
+	}))
+	defer ts.Close()
+	res, err := http.Get(ts.URL)
+	if err != nil {
+		log.Fatalf("GET failed: %v", err)
+	}
+	defer res.Body.Close()
+
+	foo := struct {
+		Foo string
+	}{}
+
+	d := NewDecoder(res.Body)
+	err = d.Decode(&foo)
+	if err != nil {
+		t.Fatalf("Decode: %v", err)
+	}
+	if foo.Foo != "bar" {
+		t.Errorf("decoded %q; want \"bar\"", foo.Foo)
+	}
+
+	// make sure we get the EOF the second time
+	err = d.Decode(&foo)
+	if err != io.EOF {
+		t.Errorf("err = %v; want io.EOF", err)
+	}
+}
diff --git a/src/encoding/json/tables.go b/src/encoding/json/tables.go
new file mode 100644
index 0000000..10acdc1
--- /dev/null
+++ b/src/encoding/json/tables.go
@@ -0,0 +1,218 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json
+
+import "unicode/utf8"
+
+// safeSet holds the value true if the ASCII character with the given array
+// position can be represented inside a JSON string without any further
+// escaping.
+//
+// All values are true except for the ASCII control characters (0-31), the
+// double quote ("), and the backslash character ("\").
+var safeSet = [utf8.RuneSelf]bool{
+	' ':      true,
+	'!':      true,
+	'"':      false,
+	'#':      true,
+	'$':      true,
+	'%':      true,
+	'&':      true,
+	'\'':     true,
+	'(':      true,
+	')':      true,
+	'*':      true,
+	'+':      true,
+	',':      true,
+	'-':      true,
+	'.':      true,
+	'/':      true,
+	'0':      true,
+	'1':      true,
+	'2':      true,
+	'3':      true,
+	'4':      true,
+	'5':      true,
+	'6':      true,
+	'7':      true,
+	'8':      true,
+	'9':      true,
+	':':      true,
+	';':      true,
+	'<':      true,
+	'=':      true,
+	'>':      true,
+	'?':      true,
+	'@':      true,
+	'A':      true,
+	'B':      true,
+	'C':      true,
+	'D':      true,
+	'E':      true,
+	'F':      true,
+	'G':      true,
+	'H':      true,
+	'I':      true,
+	'J':      true,
+	'K':      true,
+	'L':      true,
+	'M':      true,
+	'N':      true,
+	'O':      true,
+	'P':      true,
+	'Q':      true,
+	'R':      true,
+	'S':      true,
+	'T':      true,
+	'U':      true,
+	'V':      true,
+	'W':      true,
+	'X':      true,
+	'Y':      true,
+	'Z':      true,
+	'[':      true,
+	'\\':     false,
+	']':      true,
+	'^':      true,
+	'_':      true,
+	'`':      true,
+	'a':      true,
+	'b':      true,
+	'c':      true,
+	'd':      true,
+	'e':      true,
+	'f':      true,
+	'g':      true,
+	'h':      true,
+	'i':      true,
+	'j':      true,
+	'k':      true,
+	'l':      true,
+	'm':      true,
+	'n':      true,
+	'o':      true,
+	'p':      true,
+	'q':      true,
+	'r':      true,
+	's':      true,
+	't':      true,
+	'u':      true,
+	'v':      true,
+	'w':      true,
+	'x':      true,
+	'y':      true,
+	'z':      true,
+	'{':      true,
+	'|':      true,
+	'}':      true,
+	'~':      true,
+	'\u007f': true,
+}
+
+// htmlSafeSet holds the value true if the ASCII character with the given
+// array position can be safely represented inside a JSON string, embedded
+// inside of HTML <script> tags, without any additional escaping.
+//
+// All values are true except for the ASCII control characters (0-31), the
+// double quote ("), the backslash character ("\"), HTML opening and closing
+// tags ("<" and ">"), and the ampersand ("&").
+var htmlSafeSet = [utf8.RuneSelf]bool{
+	' ':      true,
+	'!':      true,
+	'"':      false,
+	'#':      true,
+	'$':      true,
+	'%':      true,
+	'&':      false,
+	'\'':     true,
+	'(':      true,
+	')':      true,
+	'*':      true,
+	'+':      true,
+	',':      true,
+	'-':      true,
+	'.':      true,
+	'/':      true,
+	'0':      true,
+	'1':      true,
+	'2':      true,
+	'3':      true,
+	'4':      true,
+	'5':      true,
+	'6':      true,
+	'7':      true,
+	'8':      true,
+	'9':      true,
+	':':      true,
+	';':      true,
+	'<':      false,
+	'=':      true,
+	'>':      false,
+	'?':      true,
+	'@':      true,
+	'A':      true,
+	'B':      true,
+	'C':      true,
+	'D':      true,
+	'E':      true,
+	'F':      true,
+	'G':      true,
+	'H':      true,
+	'I':      true,
+	'J':      true,
+	'K':      true,
+	'L':      true,
+	'M':      true,
+	'N':      true,
+	'O':      true,
+	'P':      true,
+	'Q':      true,
+	'R':      true,
+	'S':      true,
+	'T':      true,
+	'U':      true,
+	'V':      true,
+	'W':      true,
+	'X':      true,
+	'Y':      true,
+	'Z':      true,
+	'[':      true,
+	'\\':     false,
+	']':      true,
+	'^':      true,
+	'_':      true,
+	'`':      true,
+	'a':      true,
+	'b':      true,
+	'c':      true,
+	'd':      true,
+	'e':      true,
+	'f':      true,
+	'g':      true,
+	'h':      true,
+	'i':      true,
+	'j':      true,
+	'k':      true,
+	'l':      true,
+	'm':      true,
+	'n':      true,
+	'o':      true,
+	'p':      true,
+	'q':      true,
+	'r':      true,
+	's':      true,
+	't':      true,
+	'u':      true,
+	'v':      true,
+	'w':      true,
+	'x':      true,
+	'y':      true,
+	'z':      true,
+	'{':      true,
+	'|':      true,
+	'}':      true,
+	'~':      true,
+	'\u007f': true,
+}
diff --git a/src/encoding/json/tagkey_test.go b/src/encoding/json/tagkey_test.go
new file mode 100644
index 0000000..6330efd
--- /dev/null
+++ b/src/encoding/json/tagkey_test.go
@@ -0,0 +1,120 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json
+
+import (
+	"testing"
+)
+
+type basicLatin2xTag struct {
+	V string `json:"$%-/"`
+}
+
+type basicLatin3xTag struct {
+	V string `json:"0123456789"`
+}
+
+type basicLatin4xTag struct {
+	V string `json:"ABCDEFGHIJKLMO"`
+}
+
+type basicLatin5xTag struct {
+	V string `json:"PQRSTUVWXYZ_"`
+}
+
+type basicLatin6xTag struct {
+	V string `json:"abcdefghijklmno"`
+}
+
+type basicLatin7xTag struct {
+	V string `json:"pqrstuvwxyz"`
+}
+
+type miscPlaneTag struct {
+	V string `json:"色は匂へど"`
+}
+
+type percentSlashTag struct {
+	V string `json:"text/html%"` // https://golang.org/issue/2718
+}
+
+type punctuationTag struct {
+	V string `json:"!#$%&()*+-./:;<=>?@[]^_{|}~ "` // https://golang.org/issue/3546
+}
+
+type dashTag struct {
+	V string `json:"-,"`
+}
+
+type emptyTag struct {
+	W string
+}
+
+type misnamedTag struct {
+	X string `jsom:"Misnamed"`
+}
+
+type badFormatTag struct {
+	Y string `:"BadFormat"`
+}
+
+type badCodeTag struct {
+	Z string `json:" !\"#&'()*+,."`
+}
+
+type spaceTag struct {
+	Q string `json:"With space"`
+}
+
+type unicodeTag struct {
+	W string `json:"Ελλάδα"`
+}
+
+var structTagObjectKeyTests = []struct {
+	raw   any
+	value string
+	key   string
+}{
+	{basicLatin2xTag{"2x"}, "2x", "$%-/"},
+	{basicLatin3xTag{"3x"}, "3x", "0123456789"},
+	{basicLatin4xTag{"4x"}, "4x", "ABCDEFGHIJKLMO"},
+	{basicLatin5xTag{"5x"}, "5x", "PQRSTUVWXYZ_"},
+	{basicLatin6xTag{"6x"}, "6x", "abcdefghijklmno"},
+	{basicLatin7xTag{"7x"}, "7x", "pqrstuvwxyz"},
+	{miscPlaneTag{"いろはにほへと"}, "いろはにほへと", "色は匂へど"},
+	{dashTag{"foo"}, "foo", "-"},
+	{emptyTag{"Pour Moi"}, "Pour Moi", "W"},
+	{misnamedTag{"Animal Kingdom"}, "Animal Kingdom", "X"},
+	{badFormatTag{"Orfevre"}, "Orfevre", "Y"},
+	{badCodeTag{"Reliable Man"}, "Reliable Man", "Z"},
+	{percentSlashTag{"brut"}, "brut", "text/html%"},
+	{punctuationTag{"Union Rags"}, "Union Rags", "!#$%&()*+-./:;<=>?@[]^_{|}~ "},
+	{spaceTag{"Perreddu"}, "Perreddu", "With space"},
+	{unicodeTag{"Loukanikos"}, "Loukanikos", "Ελλάδα"},
+}
+
+func TestStructTagObjectKey(t *testing.T) {
+	for _, tt := range structTagObjectKeyTests {
+		b, err := Marshal(tt.raw)
+		if err != nil {
+			t.Fatalf("Marshal(%#q) failed: %v", tt.raw, err)
+		}
+		var f any
+		err = Unmarshal(b, &f)
+		if err != nil {
+			t.Fatalf("Unmarshal(%#q) failed: %v", b, err)
+		}
+		for i, v := range f.(map[string]any) {
+			switch i {
+			case tt.key:
+				if s, ok := v.(string); !ok || s != tt.value {
+					t.Fatalf("Unexpected value: %#q, want %v", s, tt.value)
+				}
+			default:
+				t.Fatalf("Unexpected key: %#q, from %#q", i, b)
+			}
+		}
+	}
+}
diff --git a/src/encoding/json/tags.go b/src/encoding/json/tags.go
new file mode 100644
index 0000000..b490328
--- /dev/null
+++ b/src/encoding/json/tags.go
@@ -0,0 +1,38 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json
+
+import (
+	"strings"
+)
+
+// tagOptions is the string following a comma in a struct field's "json"
+// tag, or the empty string. It does not include the leading comma.
+type tagOptions string
+
+// parseTag splits a struct field's json tag into its name and
+// comma-separated options.
+func parseTag(tag string) (string, tagOptions) {
+	tag, opt, _ := strings.Cut(tag, ",")
+	return tag, tagOptions(opt)
+}
+
+// Contains reports whether a comma-separated list of options
+// contains a particular substr flag. substr must be surrounded by a
+// string boundary or commas.
+func (o tagOptions) Contains(optionName string) bool {
+	if len(o) == 0 {
+		return false
+	}
+	s := string(o)
+	for s != "" {
+		var name string
+		name, s, _ = strings.Cut(s, ",")
+		if name == optionName {
+			return true
+		}
+	}
+	return false
+}
diff --git a/src/encoding/json/tags_test.go b/src/encoding/json/tags_test.go
new file mode 100644
index 0000000..8ba8ddd
--- /dev/null
+++ b/src/encoding/json/tags_test.go
@@ -0,0 +1,28 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json
+
+import (
+	"testing"
+)
+
+func TestTagParsing(t *testing.T) {
+	name, opts := parseTag("field,foobar,foo")
+	if name != "field" {
+		t.Fatalf("name = %q, want field", name)
+	}
+	for _, tt := range []struct {
+		opt  string
+		want bool
+	}{
+		{"foobar", true},
+		{"foo", true},
+		{"bar", false},
+	} {
+		if opts.Contains(tt.opt) != tt.want {
+			t.Errorf("Contains(%q) = %v", tt.opt, !tt.want)
+		}
+	}
+}
diff --git a/src/encoding/json/testdata/code.json.gz b/src/encoding/json/testdata/code.json.gz
new file mode 100644
index 0000000..1572a92
--- /dev/null
+++ b/src/encoding/json/testdata/code.json.gz
diff --git a/src/encoding/pem/example_test.go b/src/encoding/pem/example_test.go
new file mode 100644
index 0000000..806e7bb
--- /dev/null
+++ b/src/encoding/pem/example_test.go
@@ -0,0 +1,65 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package pem_test
+
+import (
+	"crypto/x509"
+	"encoding/pem"
+	"fmt"
+	"log"
+	"os"
+)
+
+func ExampleDecode() {
+	var pubPEMData = []byte(`
+-----BEGIN PUBLIC KEY-----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+-----END PUBLIC KEY-----
+and some more`)
+
+	block, rest := pem.Decode(pubPEMData)
+	if block == nil || block.Type != "PUBLIC KEY" {
+		log.Fatal("failed to decode PEM block containing public key")
+	}
+
+	pub, err := x509.ParsePKIXPublicKey(block.Bytes)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	fmt.Printf("Got a %T, with remaining data: %q", pub, rest)
+	// Output: Got a *rsa.PublicKey, with remaining data: "and some more"
+}
+
+func ExampleEncode() {
+	block := &pem.Block{
+		Type: "MESSAGE",
+		Headers: map[string]string{
+			"Animal": "Gopher",
+		},
+		Bytes: []byte("test"),
+	}
+
+	if err := pem.Encode(os.Stdout, block); err != nil {
+		log.Fatal(err)
+	}
+	// Output:
+	// -----BEGIN MESSAGE-----
+	// Animal: Gopher
+	//
+	// dGVzdA==
+	// -----END MESSAGE-----
+}
diff --git a/src/encoding/pem/pem.go b/src/encoding/pem/pem.go
new file mode 100644
index 0000000..743876c
--- /dev/null
+++ b/src/encoding/pem/pem.go
@@ -0,0 +1,314 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package pem implements the PEM data encoding, which originated in Privacy
+// Enhanced Mail. The most common use of PEM encoding today is in TLS keys and
+// certificates. See RFC 1421.
+package pem
+
+import (
+	"bytes"
+	"encoding/base64"
+	"errors"
+	"io"
+	"sort"
+	"strings"
+)
+
+// A Block represents a PEM encoded structure.
+//
+// The encoded form is:
+//    -----BEGIN Type-----
+//    Headers
+//    base64-encoded Bytes
+//    -----END Type-----
+// where Headers is a possibly empty sequence of Key: Value lines.
+type Block struct {
+	Type    string            // The type, taken from the preamble (i.e. "RSA PRIVATE KEY").
+	Headers map[string]string // Optional headers.
+	Bytes   []byte            // The decoded bytes of the contents. Typically a DER encoded ASN.1 structure.
+}
+
+// getLine results the first \r\n or \n delineated line from the given byte
+// array. The line does not include trailing whitespace or the trailing new
+// line bytes. The remainder of the byte array (also not including the new line
+// bytes) is also returned and this will always be smaller than the original
+// argument.
+func getLine(data []byte) (line, rest []byte) {
+	i := bytes.IndexByte(data, '\n')
+	var j int
+	if i < 0 {
+		i = len(data)
+		j = i
+	} else {
+		j = i + 1
+		if i > 0 && data[i-1] == '\r' {
+			i--
+		}
+	}
+	return bytes.TrimRight(data[0:i], " \t"), data[j:]
+}
+
+// removeSpacesAndTabs returns a copy of its input with all spaces and tabs
+// removed, if there were any. Otherwise, the input is returned unchanged.
+//
+// The base64 decoder already skips newline characters, so we don't need to
+// filter them out here.
+func removeSpacesAndTabs(data []byte) []byte {
+	if !bytes.ContainsAny(data, " \t") {
+		// Fast path; most base64 data within PEM contains newlines, but
+		// no spaces nor tabs. Skip the extra alloc and work.
+		return data
+	}
+	result := make([]byte, len(data))
+	n := 0
+
+	for _, b := range data {
+		if b == ' ' || b == '\t' {
+			continue
+		}
+		result[n] = b
+		n++
+	}
+
+	return result[0:n]
+}
+
+var pemStart = []byte("\n-----BEGIN ")
+var pemEnd = []byte("\n-----END ")
+var pemEndOfLine = []byte("-----")
+var colon = []byte(":")
+
+// Decode will find the next PEM formatted block (certificate, private key
+// etc) in the input. It returns that block and the remainder of the input. If
+// no PEM data is found, p is nil and the whole of the input is returned in
+// rest.
+func Decode(data []byte) (p *Block, rest []byte) {
+	// pemStart begins with a newline. However, at the very beginning of
+	// the byte array, we'll accept the start string without it.
+	rest = data
+	for {
+		if bytes.HasPrefix(rest, pemStart[1:]) {
+			rest = rest[len(pemStart)-1:]
+		} else if _, after, ok := bytes.Cut(rest, pemStart); ok {
+			rest = after
+		} else {
+			return nil, data
+		}
+
+		var typeLine []byte
+		typeLine, rest = getLine(rest)
+		if !bytes.HasSuffix(typeLine, pemEndOfLine) {
+			continue
+		}
+		typeLine = typeLine[0 : len(typeLine)-len(pemEndOfLine)]
+
+		p = &Block{
+			Headers: make(map[string]string),
+			Type:    string(typeLine),
+		}
+
+		for {
+			// This loop terminates because getLine's second result is
+			// always smaller than its argument.
+			if len(rest) == 0 {
+				return nil, data
+			}
+			line, next := getLine(rest)
+
+			key, val, ok := bytes.Cut(line, colon)
+			if !ok {
+				break
+			}
+
+			// TODO(agl): need to cope with values that spread across lines.
+			key = bytes.TrimSpace(key)
+			val = bytes.TrimSpace(val)
+			p.Headers[string(key)] = string(val)
+			rest = next
+		}
+
+		var endIndex, endTrailerIndex int
+
+		// If there were no headers, the END line might occur
+		// immediately, without a leading newline.
+		if len(p.Headers) == 0 && bytes.HasPrefix(rest, pemEnd[1:]) {
+			endIndex = 0
+			endTrailerIndex = len(pemEnd) - 1
+		} else {
+			endIndex = bytes.Index(rest, pemEnd)
+			endTrailerIndex = endIndex + len(pemEnd)
+		}
+
+		if endIndex < 0 {
+			continue
+		}
+
+		// After the "-----" of the ending line, there should be the same type
+		// and then a final five dashes.
+		endTrailer := rest[endTrailerIndex:]
+		endTrailerLen := len(typeLine) + len(pemEndOfLine)
+		if len(endTrailer) < endTrailerLen {
+			continue
+		}
+
+		restOfEndLine := endTrailer[endTrailerLen:]
+		endTrailer = endTrailer[:endTrailerLen]
+		if !bytes.HasPrefix(endTrailer, typeLine) ||
+			!bytes.HasSuffix(endTrailer, pemEndOfLine) {
+			continue
+		}
+
+		// The line must end with only whitespace.
+		if s, _ := getLine(restOfEndLine); len(s) != 0 {
+			continue
+		}
+
+		base64Data := removeSpacesAndTabs(rest[:endIndex])
+		p.Bytes = make([]byte, base64.StdEncoding.DecodedLen(len(base64Data)))
+		n, err := base64.StdEncoding.Decode(p.Bytes, base64Data)
+		if err != nil {
+			continue
+		}
+		p.Bytes = p.Bytes[:n]
+
+		// the -1 is because we might have only matched pemEnd without the
+		// leading newline if the PEM block was empty.
+		_, rest = getLine(rest[endIndex+len(pemEnd)-1:])
+		return p, rest
+	}
+}
+
+const pemLineLength = 64
+
+type lineBreaker struct {
+	line [pemLineLength]byte
+	used int
+	out  io.Writer
+}
+
+var nl = []byte{'\n'}
+
+func (l *lineBreaker) Write(b []byte) (n int, err error) {
+	if l.used+len(b) < pemLineLength {
+		copy(l.line[l.used:], b)
+		l.used += len(b)
+		return len(b), nil
+	}
+
+	n, err = l.out.Write(l.line[0:l.used])
+	if err != nil {
+		return
+	}
+	excess := pemLineLength - l.used
+	l.used = 0
+
+	n, err = l.out.Write(b[0:excess])
+	if err != nil {
+		return
+	}
+
+	n, err = l.out.Write(nl)
+	if err != nil {
+		return
+	}
+
+	return l.Write(b[excess:])
+}
+
+func (l *lineBreaker) Close() (err error) {
+	if l.used > 0 {
+		_, err = l.out.Write(l.line[0:l.used])
+		if err != nil {
+			return
+		}
+		_, err = l.out.Write(nl)
+	}
+
+	return
+}
+
+func writeHeader(out io.Writer, k, v string) error {
+	_, err := out.Write([]byte(k + ": " + v + "\n"))
+	return err
+}
+
+// Encode writes the PEM encoding of b to out.
+func Encode(out io.Writer, b *Block) error {
+	// Check for invalid block before writing any output.
+	for k := range b.Headers {
+		if strings.Contains(k, ":") {
+			return errors.New("pem: cannot encode a header key that contains a colon")
+		}
+	}
+
+	// All errors below are relayed from underlying io.Writer,
+	// so it is now safe to write data.
+
+	if _, err := out.Write(pemStart[1:]); err != nil {
+		return err
+	}
+	if _, err := out.Write([]byte(b.Type + "-----\n")); err != nil {
+		return err
+	}
+
+	if len(b.Headers) > 0 {
+		const procType = "Proc-Type"
+		h := make([]string, 0, len(b.Headers))
+		hasProcType := false
+		for k := range b.Headers {
+			if k == procType {
+				hasProcType = true
+				continue
+			}
+			h = append(h, k)
+		}
+		// The Proc-Type header must be written first.
+		// See RFC 1421, section 4.6.1.1
+		if hasProcType {
+			if err := writeHeader(out, procType, b.Headers[procType]); err != nil {
+				return err
+			}
+		}
+		// For consistency of output, write other headers sorted by key.
+		sort.Strings(h)
+		for _, k := range h {
+			if err := writeHeader(out, k, b.Headers[k]); err != nil {
+				return err
+			}
+		}
+		if _, err := out.Write(nl); err != nil {
+			return err
+		}
+	}
+
+	var breaker lineBreaker
+	breaker.out = out
+
+	b64 := base64.NewEncoder(base64.StdEncoding, &breaker)
+	if _, err := b64.Write(b.Bytes); err != nil {
+		return err
+	}
+	b64.Close()
+	breaker.Close()
+
+	if _, err := out.Write(pemEnd[1:]); err != nil {
+		return err
+	}
+	_, err := out.Write([]byte(b.Type + "-----\n"))
+	return err
+}
+
+// EncodeToMemory returns the PEM encoding of b.
+//
+// If b has invalid headers and cannot be encoded,
+// EncodeToMemory returns nil. If it is important to
+// report details about this error case, use Encode instead.
+func EncodeToMemory(b *Block) []byte {
+	var buf bytes.Buffer
+	if err := Encode(&buf, b); err != nil {
+		return nil
+	}
+	return buf.Bytes()
+}
diff --git a/src/encoding/pem/pem_test.go b/src/encoding/pem/pem_test.go
new file mode 100644
index 0000000..c94b5ca
--- /dev/null
+++ b/src/encoding/pem/pem_test.go
@@ -0,0 +1,640 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package pem
+
+import (
+	"bytes"
+	"io"
+	"reflect"
+	"strings"
+	"testing"
+	"testing/quick"
+)
+
+type GetLineTest struct {
+	in, out1, out2 string
+}
+
+var getLineTests = []GetLineTest{
+	{"abc", "abc", ""},
+	{"abc\r", "abc\r", ""},
+	{"abc\n", "abc", ""},
+	{"abc\r\n", "abc", ""},
+	{"abc\nd", "abc", "d"},
+	{"abc\r\nd", "abc", "d"},
+	{"\nabc", "", "abc"},
+	{"\r\nabc", "", "abc"},
+	{"abc\t \nd", "abc", "d"},
+	{"\t abc\nd", "\t abc", "d"},
+	{"abc\n\t d", "abc", "\t d"},
+	{"abc\nd\t ", "abc", "d\t "},
+}
+
+func TestGetLine(t *testing.T) {
+	for i, test := range getLineTests {
+		x, y := getLine([]byte(test.in))
+		if string(x) != test.out1 || string(y) != test.out2 {
+			t.Errorf("#%d got:%+v,%+v want:%s,%s", i, x, y, test.out1, test.out2)
+		}
+	}
+}
+
+func TestDecode(t *testing.T) {
+	result, remainder := Decode([]byte(pemData))
+	if !reflect.DeepEqual(result, certificate) {
+		t.Errorf("#0 got:%#v want:%#v", result, certificate)
+	}
+	result, remainder = Decode(remainder)
+	if !reflect.DeepEqual(result, privateKey) {
+		t.Errorf("#1 got:%#v want:%#v", result, privateKey)
+	}
+
+	isEmpty := func(block *Block) bool {
+		return block != nil && block.Type == "EMPTY" && len(block.Headers) == 0 && len(block.Bytes) == 0
+	}
+	result, remainder = Decode(remainder)
+	if !isEmpty(result) {
+		t.Errorf("#2 should be empty but got:%#v", result)
+	}
+	result, remainder = Decode(remainder)
+	if !isEmpty(result) {
+		t.Errorf("#3 should be empty but got:%#v", result)
+	}
+	result, remainder = Decode(remainder)
+	if !isEmpty(result) {
+		t.Errorf("#4 should be empty but got:%#v", result)
+	}
+
+	result, remainder = Decode(remainder)
+	if result == nil || result.Type != "HEADERS" || len(result.Headers) != 1 {
+		t.Errorf("#5 expected single header block but got :%v", result)
+	}
+
+	if len(remainder) != 0 {
+		t.Errorf("expected nothing remaining of pemData, but found %s", string(remainder))
+	}
+
+	result, _ = Decode([]byte(pemPrivateKey2))
+	if !reflect.DeepEqual(result, privateKey2) {
+		t.Errorf("#2 got:%#v want:%#v", result, privateKey2)
+	}
+}
+
+const pemTooFewEndingDashes = `
+-----BEGIN FOO-----
+dGVzdA==
+-----END FOO----`
+
+const pemTooManyEndingDashes = `
+-----BEGIN FOO-----
+dGVzdA==
+-----END FOO------`
+
+const pemTrailingNonWhitespace = `
+-----BEGIN FOO-----
+dGVzdA==
+-----END FOO----- .`
+
+const pemWrongEndingType = `
+-----BEGIN FOO-----
+dGVzdA==
+-----END BAR-----`
+
+const pemMissingEndingSpace = `
+-----BEGIN FOO-----
+dGVzdA==
+-----ENDBAR-----`
+
+const pemMissingEndLine = `
+-----BEGIN FOO-----
+Header: 1`
+
+var pemRepeatingBegin = strings.Repeat("-----BEGIN \n", 10)
+
+var badPEMTests = []struct {
+	name  string
+	input string
+}{
+	{
+		"too few trailing dashes",
+		pemTooFewEndingDashes,
+	},
+	{
+		"too many trailing dashes",
+		pemTooManyEndingDashes,
+	},
+	{
+		"trailing non-whitespace",
+		pemTrailingNonWhitespace,
+	},
+	{
+		"incorrect ending type",
+		pemWrongEndingType,
+	},
+	{
+		"missing ending space",
+		pemMissingEndingSpace,
+	},
+	{
+		"repeating begin",
+		pemRepeatingBegin,
+	},
+	{
+		"missing end line",
+		pemMissingEndLine,
+	},
+}
+
+func TestBadDecode(t *testing.T) {
+	for _, test := range badPEMTests {
+		result, rest := Decode([]byte(test.input))
+		if result != nil {
+			t.Errorf("unexpected success while parsing %q", test.name)
+		}
+		if string(rest) != test.input {
+			t.Errorf("unexpected rest: %q; want = %q", rest, test.input)
+		}
+	}
+}
+
+func TestCVE202224675(t *testing.T) {
+	// Prior to CVE-2022-24675, this input would cause a stack overflow.
+	input := []byte(strings.Repeat("-----BEGIN \n", 10000000))
+	result, rest := Decode(input)
+	if result != nil || !reflect.DeepEqual(rest, input) {
+		t.Errorf("Encode of %#v decoded as %#v", input, rest)
+	}
+}
+
+func TestEncode(t *testing.T) {
+	r := EncodeToMemory(privateKey2)
+	if string(r) != pemPrivateKey2 {
+		t.Errorf("got:%s want:%s", r, pemPrivateKey2)
+	}
+}
+
+type lineBreakerTest struct {
+	in, out string
+}
+
+const sixtyFourCharString = "0123456789012345678901234567890123456789012345678901234567890123"
+
+var lineBreakerTests = []lineBreakerTest{
+	{"", ""},
+	{"a", "a\n"},
+	{"ab", "ab\n"},
+	{sixtyFourCharString, sixtyFourCharString + "\n"},
+	{sixtyFourCharString + "X", sixtyFourCharString + "\nX\n"},
+	{sixtyFourCharString + sixtyFourCharString, sixtyFourCharString + "\n" + sixtyFourCharString + "\n"},
+}
+
+func TestLineBreaker(t *testing.T) {
+	for i, test := range lineBreakerTests {
+		buf := new(bytes.Buffer)
+		var breaker lineBreaker
+		breaker.out = buf
+		_, err := breaker.Write([]byte(test.in))
+		if err != nil {
+			t.Errorf("#%d: error from Write: %s", i, err)
+			continue
+		}
+		err = breaker.Close()
+		if err != nil {
+			t.Errorf("#%d: error from Close: %s", i, err)
+			continue
+		}
+
+		if string(buf.Bytes()) != test.out {
+			t.Errorf("#%d: got:%s want:%s", i, string(buf.Bytes()), test.out)
+		}
+	}
+
+	for i, test := range lineBreakerTests {
+		buf := new(bytes.Buffer)
+		var breaker lineBreaker
+		breaker.out = buf
+
+		for i := 0; i < len(test.in); i++ {
+			_, err := breaker.Write([]byte(test.in[i : i+1]))
+			if err != nil {
+				t.Errorf("#%d: error from Write (byte by byte): %s", i, err)
+				continue
+			}
+		}
+		err := breaker.Close()
+		if err != nil {
+			t.Errorf("#%d: error from Close (byte by byte): %s", i, err)
+			continue
+		}
+
+		if string(buf.Bytes()) != test.out {
+			t.Errorf("#%d: (byte by byte) got:%s want:%s", i, string(buf.Bytes()), test.out)
+		}
+	}
+}
+
+func TestFuzz(t *testing.T) {
+	// PEM is a text-based format. Assume header fields with leading/trailing spaces
+	// or embedded newlines will not round trip correctly and don't need to be tested.
+	isBad := func(s string) bool {
+		return strings.ContainsAny(s, "\r\n") || strings.TrimSpace(s) != s
+	}
+
+	testRoundtrip := func(block Block) bool {
+		// Reject bad Type
+		// Type with colons will proceed as key/val pair and cause an error.
+		if isBad(block.Type) || strings.Contains(block.Type, ":") {
+			return true
+		}
+		for key, val := range block.Headers {
+			// Reject bad key/val.
+			// Also, keys with colons cannot be encoded, because : is the key: val separator.
+			if isBad(key) || isBad(val) || strings.Contains(key, ":") {
+				return true
+			}
+		}
+
+		var buf bytes.Buffer
+		if err := Encode(&buf, &block); err != nil {
+			t.Errorf("Encode of %#v resulted in error: %s", &block, err)
+			return false
+		}
+		decoded, rest := Decode(buf.Bytes())
+		if block.Headers == nil {
+			// Encoder supports nil Headers but decoder returns initialized.
+			block.Headers = make(map[string]string)
+		}
+		if block.Bytes == nil {
+			// Encoder supports nil Bytes but decoder returns initialized.
+			block.Bytes = make([]byte, 0)
+		}
+		if !reflect.DeepEqual(decoded, &block) {
+			t.Errorf("Encode of %#v decoded as %#v", &block, decoded)
+			return false
+		}
+		if len(rest) != 0 {
+			t.Errorf("Encode of %#v decoded correctly, but with %x left over", block, rest)
+			return false
+		}
+		return true
+	}
+
+	// Explicitly test the empty block.
+	if !testRoundtrip(Block{
+		Type:    "EMPTY",
+		Headers: make(map[string]string),
+		Bytes:   []byte{},
+	}) {
+		return
+	}
+
+	quick.Check(testRoundtrip, nil)
+}
+
+func BenchmarkEncode(b *testing.B) {
+	data := &Block{Bytes: make([]byte, 65536)}
+	b.SetBytes(int64(len(data.Bytes)))
+	for i := 0; i < b.N; i++ {
+		Encode(io.Discard, data)
+	}
+}
+
+func BenchmarkDecode(b *testing.B) {
+	block := &Block{Bytes: make([]byte, 65536)}
+	data := EncodeToMemory(block)
+	b.SetBytes(int64(len(data)))
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		Decode(data)
+	}
+}
+
+var pemData = testingKey(`verify return:0
+-----BEGIN CERTIFICATE-----
+sdlfkjskldfj
+  -----BEGIN CERTIFICATE-----
+---
+Certificate chain
+ 0 s:/C=AU/ST=Somewhere/L=Someplace/O=Foo Bar/CN=foo.example.com
+   i:/C=ZA/O=CA Inc./CN=CA Inc
+-----BEGIN CERTIFICATE-----
+testing
+-----BEGIN CERTIFICATE-----
+-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
+ 1 s:/C=ZA/O=Ca Inc./CN=CA Inc
+
+-----BEGIN RSA TESTING KEY-----
+Proc-Type: 4,ENCRYPTED
+DEK-Info: DES-EDE3-CBC,80C7C7A09690757A
+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+-----END RSA TESTING KEY-----
+
+
+-----BEGIN EMPTY-----
+-----END EMPTY-----
+
+-----BEGIN EMPTY-----
+
+-----END EMPTY-----
+
+-----BEGIN EMPTY-----
+
+
+-----END EMPTY-----
+
+# This shouldn't be recognised because of the missing newline after the
+headers.
+-----BEGIN HEADERS-----
+Header: 1
+-----END HEADERS-----
+
+# This should be valid, however.
+-----BEGIN HEADERS-----
+Header: 1
+
+-----END HEADERS-----`)
+
+var certificate = &Block{Type: "CERTIFICATE",
+	Headers: map[string]string{},
+	Bytes: []uint8{0x30, 0x82, 0x3, 0xe9, 0x30, 0x82, 0x3, 0x52, 0x2, 0x1,
+		0x1, 0x30, 0xd, 0x6, 0x9, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0xd,
+		0x1, 0x1, 0x5, 0x5, 0x0, 0x30, 0x81, 0x8b, 0x31, 0xb, 0x30,
+		0x9, 0x6, 0x3, 0x55, 0x4, 0x6, 0x13, 0x2, 0x55, 0x53, 0x31,
+		0x13, 0x30, 0x11, 0x6, 0x3, 0x55, 0x4, 0x8, 0x13, 0xa, 0x43,
+		0x61, 0x6c, 0x69, 0x66, 0x6f, 0x72, 0x6e, 0x69, 0x61, 0x31,
+		0x16, 0x30, 0x14, 0x6, 0x3, 0x55, 0x4, 0x7, 0x13, 0xd, 0x53,
+		0x61, 0x6e, 0x20, 0x46, 0x72, 0x61, 0x6e, 0x63, 0x69, 0x73,
+		0x63, 0x6f, 0x31, 0x14, 0x30, 0x12, 0x6, 0x3, 0x55, 0x4, 0xa,
+		0x13, 0xb, 0x47, 0x6f, 0x6f, 0x67, 0x6c, 0x65, 0x20, 0x49,
+		0x6e, 0x63, 0x2e, 0x31, 0xc, 0x30, 0xa, 0x6, 0x3, 0x55, 0x4,
+		0xb, 0x13, 0x3, 0x45, 0x6e, 0x67, 0x31, 0xc, 0x30, 0xa, 0x6,
+		0x3, 0x55, 0x4, 0x3, 0x13, 0x3, 0x61, 0x67, 0x6c, 0x31, 0x1d,
+		0x30, 0x1b, 0x6, 0x9, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0xd, 0x1,
+		0x9, 0x1, 0x16, 0xe, 0x61, 0x67, 0x6c, 0x40, 0x67, 0x6f, 0x6f,
+		0x67, 0x6c, 0x65, 0x2e, 0x63, 0x6f, 0x6d, 0x30, 0x1e, 0x17,
+		0xd, 0x30, 0x39, 0x30, 0x39, 0x30, 0x39, 0x32, 0x32, 0x30,
+		0x35, 0x34, 0x33, 0x5a, 0x17, 0xd, 0x31, 0x30, 0x30, 0x39,
+		0x30, 0x39, 0x32, 0x32, 0x30, 0x35, 0x34, 0x33, 0x5a, 0x30,
+		0x6a, 0x31, 0xb, 0x30, 0x9, 0x6, 0x3, 0x55, 0x4, 0x6, 0x13,
+		0x2, 0x41, 0x55, 0x31, 0x13, 0x30, 0x11, 0x6, 0x3, 0x55, 0x4,
+		0x8, 0x13, 0xa, 0x53, 0x6f, 0x6d, 0x65, 0x2d, 0x53, 0x74, 0x61,
+		0x74, 0x65, 0x31, 0x21, 0x30, 0x1f, 0x6, 0x3, 0x55, 0x4, 0xa,
+		0x13, 0x18, 0x49, 0x6e, 0x74, 0x65, 0x72, 0x6e, 0x65, 0x74,
+		0x20, 0x57, 0x69, 0x64, 0x67, 0x69, 0x74, 0x73, 0x20, 0x50,
+		0x74, 0x79, 0x20, 0x4c, 0x74, 0x64, 0x31, 0x23, 0x30, 0x21,
+		0x6, 0x3, 0x55, 0x4, 0x3, 0x13, 0x1a, 0x65, 0x75, 0x72, 0x6f,
+		0x70, 0x61, 0x2e, 0x73, 0x66, 0x6f, 0x2e, 0x63, 0x6f, 0x72,
+		0x70, 0x2e, 0x67, 0x6f, 0x6f, 0x67, 0x6c, 0x65, 0x2e, 0x63,
+		0x6f, 0x6d, 0x30, 0x82, 0x2, 0x22, 0x30, 0xd, 0x6, 0x9, 0x2a,
+		0x86, 0x48, 0x86, 0xf7, 0xd, 0x1, 0x1, 0x1, 0x5, 0x0, 0x3,
+		0x82, 0x2, 0xf, 0x0, 0x30, 0x82, 0x2, 0xa, 0x2, 0x82, 0x2, 0x1,
+		0x0, 0xba, 0xa6, 0x6, 0x2d, 0xef, 0xf1, 0x22, 0x6c, 0x10, 0xee,
+		0x98, 0x4, 0x85, 0xf9, 0x2d, 0x2a, 0xbe, 0xa7, 0x4b, 0xfd,
+		0xff, 0xa7, 0xa2, 0xe2, 0x70, 0xd9, 0x3d, 0x50, 0x73, 0xc1,
+		0xa6, 0x5c, 0x5f, 0xe2, 0x89, 0x47, 0x2b, 0xb2, 0xc, 0xe1,
+		0xfc, 0x57, 0x7c, 0xa4, 0x38, 0x73, 0xfd, 0x3f, 0x7a, 0x42,
+		0xf, 0x48, 0xc9, 0x1e, 0x33, 0xb6, 0xe7, 0x36, 0x31, 0x7a,
+		0xe6, 0x3e, 0xb6, 0xbe, 0xcc, 0xb, 0x92, 0x7f, 0x96, 0xde,
+		0xbc, 0x54, 0x5e, 0x4a, 0xab, 0xe9, 0x22, 0xdf, 0x3, 0xba,
+		0xfd, 0x7, 0x6c, 0x36, 0xdc, 0xaa, 0xcf, 0xd7, 0x28, 0xf7,
+		0xc1, 0xb8, 0xc0, 0xde, 0xfa, 0x87, 0xfb, 0x6b, 0xd1, 0x82,
+		0xcb, 0xb, 0xc0, 0x67, 0x86, 0x54, 0x25, 0xca, 0x74, 0xb6,
+		0x1a, 0x83, 0xf5, 0xf2, 0x93, 0x4e, 0x35, 0x16, 0x38, 0x1c,
+		0xc7, 0x63, 0x5b, 0x8d, 0x13, 0x84, 0x62, 0xb6, 0xb8, 0x66,
+		0x24, 0x2a, 0xdb, 0x4, 0x65, 0xdb, 0x27, 0x6e, 0x3d, 0x6e,
+		0xf8, 0x26, 0x6f, 0xb8, 0xe0, 0x74, 0x89, 0xc7, 0xd8, 0xf5,
+		0x3b, 0x3d, 0x3e, 0x79, 0x86, 0xe8, 0xef, 0x3a, 0x82, 0x2c,
+		0x41, 0x6d, 0xa8, 0xb1, 0x70, 0x45, 0x46, 0xea, 0xf8, 0xa4,
+		0x5d, 0x70, 0x99, 0x58, 0x78, 0x5b, 0x89, 0x53, 0x2c, 0x3e,
+		0xa9, 0x8d, 0xf2, 0xc, 0x51, 0xc3, 0xb, 0x20, 0x21, 0xc4, 0x5c,
+		0x43, 0x7b, 0xdc, 0xf0, 0xe2, 0x73, 0xc2, 0x92, 0xdc, 0x4b,
+		0x4d, 0x60, 0x2c, 0x28, 0x22, 0x57, 0x7e, 0xb6, 0x92, 0x1,
+		0x8c, 0x4d, 0x50, 0x39, 0xbd, 0x4a, 0x3b, 0x2b, 0x89, 0x4,
+		0xd5, 0xba, 0x12, 0xcc, 0x3d, 0x0, 0xb6, 0x67, 0xee, 0xcb,
+		0x56, 0x75, 0x87, 0x4, 0xa8, 0xc, 0x2f, 0xbf, 0x6d, 0x1e, 0x80,
+		0xdd, 0xad, 0x11, 0x7a, 0xa3, 0xed, 0xe, 0x3f, 0xd5, 0xc7,
+		0x32, 0x3d, 0x97, 0x37, 0x3d, 0x8, 0x2, 0xdc, 0x52, 0x7c, 0x5,
+		0xed, 0xa6, 0xb6, 0x59, 0x4c, 0xfb, 0xcd, 0x2a, 0x7f, 0x87,
+		0x40, 0x69, 0xf, 0xdf, 0x5a, 0xf0, 0xad, 0x3a, 0xb4, 0x39,
+		0xa6, 0x77, 0xde, 0xf6, 0x3b, 0x90, 0xbc, 0x2a, 0x3c, 0x63,
+		0x45, 0x46, 0x94, 0x57, 0x2b, 0x4b, 0x2b, 0x3f, 0x33, 0x34,
+		0xa0, 0xf4, 0xb2, 0x7f, 0xdb, 0x88, 0xd9, 0x56, 0xc, 0xd0,
+		0xbd, 0xe7, 0x7f, 0x42, 0xea, 0x6c, 0xa7, 0xcf, 0x70, 0x56,
+		0x27, 0x70, 0x23, 0x38, 0xed, 0xf9, 0x67, 0x52, 0x7f, 0x25,
+		0x9f, 0x1f, 0x4f, 0xef, 0xd5, 0xa4, 0xb, 0xbe, 0xee, 0x5c,
+		0x31, 0x8b, 0x96, 0xff, 0xf0, 0xb4, 0x5b, 0x69, 0xe5, 0x63,
+		0x38, 0x8b, 0xe5, 0xb9, 0x44, 0x4e, 0x7b, 0x4c, 0xf0, 0xcc,
+		0xb6, 0xc9, 0xb3, 0x40, 0x47, 0x2d, 0xc8, 0x8, 0x7c, 0x42, 0x6,
+		0xfd, 0x91, 0x36, 0xd3, 0xc8, 0x59, 0x5, 0x66, 0xf8, 0x4f,
+		0x7f, 0x5b, 0x9a, 0xf0, 0x87, 0x62, 0x9, 0x47, 0x80, 0xc7,
+		0x9f, 0x62, 0xc7, 0xc1, 0x45, 0x66, 0x4f, 0xf8, 0x47, 0x35,
+		0x37, 0x41, 0x2e, 0x5e, 0x54, 0x87, 0xa, 0xf8, 0x59, 0xce,
+		0xc9, 0x84, 0x4e, 0xc0, 0x56, 0xa6, 0xf5, 0xe2, 0x95, 0x4d,
+		0xcf, 0x59, 0x6b, 0xe6, 0x3c, 0x6c, 0xa7, 0xff, 0xe7, 0x70,
+		0x8c, 0x1f, 0xb5, 0xbe, 0xe6, 0x65, 0xd, 0xc3, 0x17, 0x4d,
+		0xd8, 0x9d, 0xaf, 0xa3, 0x26, 0x1a, 0x73, 0xc7, 0xc0, 0x90,
+		0xa1, 0xe2, 0xd3, 0xe9, 0xa4, 0x2, 0x1f, 0x2c, 0xe6, 0x1f,
+		0xaf, 0xc, 0xac, 0x71, 0xd3, 0xe0, 0xc0, 0xb, 0x3f, 0x25, 0x2c,
+		0x3e, 0x89, 0xa3, 0x9f, 0xbd, 0x46, 0x35, 0x3b, 0x43, 0x79,
+		0x60, 0x17, 0x89, 0xb8, 0xc2, 0x81, 0xd2, 0xfa, 0x88, 0x70,
+		0x2, 0x8, 0x5e, 0x87, 0xb5, 0xb9, 0x74, 0xcc, 0x69, 0x46, 0xd0,
+		0xe0, 0xa, 0xf9, 0xb7, 0x67, 0xd1, 0x2, 0x3, 0x1, 0x0, 0x1,
+		0x30, 0xd, 0x6, 0x9, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0xd, 0x1,
+		0x1, 0x5, 0x5, 0x0, 0x3, 0x81, 0x81, 0x0, 0xe2, 0xa7, 0x40,
+		0x3b, 0x6a, 0x5, 0x5d, 0xb8, 0xbd, 0x5a, 0xaf, 0x7a, 0xc2,
+		0xf9, 0x76, 0x79, 0xb2, 0x16, 0x91, 0x4f, 0x5c, 0x19, 0xf7,
+		0x59, 0xd1, 0x5f, 0xc0, 0x3e, 0x83, 0xcc, 0x46, 0xf6, 0xd5,
+		0x45, 0x46, 0xe6, 0x4a, 0xe6, 0x26, 0x2b, 0xbe, 0x56, 0x28,
+		0xa9, 0x39, 0x12, 0x4f, 0x18, 0xc9, 0x20, 0xa0, 0xbe, 0x81,
+		0x8d, 0x4d, 0xb5, 0x5c, 0x8f, 0x79, 0x55, 0x6, 0xee, 0x9f,
+		0x93, 0xfc, 0xbe, 0xf8, 0x3c, 0x67, 0xe1, 0x67, 0x16, 0xcb,
+		0xd1, 0x15, 0x8d, 0xde, 0xd4, 0x20, 0xb3, 0x1, 0x54, 0x18,
+		0x66, 0xc5, 0x24, 0x2f, 0xd, 0x88, 0xef, 0x32, 0x3f, 0x74,
+		0xd9, 0x56, 0x74, 0x1f, 0x17, 0xa7, 0xbb, 0xfe, 0xdf, 0xf,
+		0x6c, 0x5f, 0x93, 0x77, 0x27, 0xf5, 0xae, 0x27, 0x52, 0x8e,
+		0x3b, 0x99, 0xb6, 0xea, 0x44, 0x65, 0x1d, 0xa, 0x3b, 0x13,
+		0x34, 0xf7, 0xf7, 0xbe, 0x20,
+	},
+}
+
+var privateKey = &Block{Type: "RSA PRIVATE KEY",
+	Headers: map[string]string{"DEK-Info": "DES-EDE3-CBC,80C7C7A09690757A", "Proc-Type": "4,ENCRYPTED"},
+	Bytes: []uint8{0x79, 0xa, 0x79, 0x66, 0x41, 0xfa, 0xb,
+		0x21, 0xc1, 0xcf, 0xb0, 0x59, 0x7d, 0x43, 0xf1, 0xc8, 0xb0,
+		0x82, 0x99, 0xfb, 0x6c, 0x4, 0x9e, 0xc7, 0x96, 0xa1, 0x9b,
+		0xf0, 0xb7, 0x76, 0xd5, 0xc4, 0xb0, 0x9f, 0x35, 0x99, 0xe3,
+		0xf4, 0x88, 0x96, 0x1c, 0xab, 0x52, 0xdb, 0x1f, 0xc3, 0xb5,
+		0x51, 0xd9, 0x34, 0xf0, 0x3, 0xea, 0x1d, 0xa3, 0xd7, 0xb1,
+		0xec, 0x67, 0x71, 0x39, 0x36, 0x87, 0xf2, 0x86, 0x45, 0xba,
+		0x62, 0x11, 0xa2, 0x21, 0x23, 0x1e, 0xc9, 0x3c, 0x53, 0xb0,
+		0x61, 0x9e, 0xda, 0x7e, 0x7a, 0x49, 0xf, 0x3f, 0xbf, 0x71,
+		0xba, 0x79, 0xcd, 0xee, 0x16, 0xfb, 0x86, 0x48, 0x6b, 0xc8,
+		0x60, 0xd0, 0x66, 0x0, 0x3b, 0xb3, 0x67, 0x10, 0x1d, 0xe,
+		0xf5, 0xbf, 0x78, 0x30, 0x4f, 0x60, 0x40, 0x8, 0x7, 0xed,
+		0xdb, 0xa8, 0xc2, 0x8d, 0xb3, 0x35, 0xc2, 0x3, 0x73, 0x6,
+		0x72, 0x7c, 0x33, 0x44, 0x73, 0x9f, 0xaf, 0x18, 0x5a, 0xa6,
+		0x8f, 0xb5, 0xd0, 0x6e, 0xf2, 0xa6, 0xff, 0xcd, 0x54, 0x79,
+		0x24, 0x1d, 0x66, 0x9e, 0xab, 0xd3, 0x49, 0xb1, 0x6c, 0x7c,
+		0x5e, 0x72, 0x31, 0xce, 0xa8, 0xd9, 0x64, 0x3d, 0x8c, 0x90,
+		0xa5, 0xe8, 0xac, 0xa9, 0x9c, 0xc9, 0x7e, 0x6, 0x92, 0xfe,
+		0x76, 0x5b, 0xdd, 0x8d, 0x85, 0x4a, 0xe2, 0x5f, 0x65, 0x62,
+		0xc0, 0x75, 0x1e, 0xcd, 0xdd, 0xfb, 0x30, 0xc1, 0x6d, 0x6c,
+		0x68, 0xb3, 0xcd, 0x7c, 0xcf, 0x38, 0x52, 0xf3, 0xfc, 0xba,
+		0x78, 0x87, 0xe2, 0x48, 0x6d, 0xbb, 0x72, 0xaa, 0xdb, 0x85,
+		0x44, 0x5b, 0x9a, 0x8, 0x92, 0x7c, 0x35, 0xe3, 0x9d, 0xc2,
+		0xb8, 0x9b, 0xfa, 0x4b, 0x71, 0xe, 0xe6, 0x98, 0x12, 0xfa,
+		0x98, 0x53, 0xab, 0xdc, 0xf8, 0xf8, 0x8d, 0xea, 0x73, 0x80,
+		0xe8, 0x85, 0x44, 0xbe, 0x8c, 0x28, 0x4f, 0xff, 0x87, 0xad,
+		0x9f, 0x66, 0xf2, 0x35, 0x12, 0xb6, 0x2b, 0xf1, 0x5b, 0xa7,
+		0x1c, 0x4c, 0xa4, 0x80, 0xa3, 0x61, 0xa, 0x10, 0xef, 0x6f,
+		0x54, 0x4e, 0xe8, 0xb1, 0x1f, 0xa8, 0xa0, 0x6e, 0xf8, 0x8b,
+		0xf0, 0x4c, 0x1e, 0x9f, 0x6, 0x15, 0xb7, 0x4c, 0x22, 0xcc,
+		0x9d, 0x53, 0xd8, 0x56, 0x86, 0x30, 0x3, 0xe7, 0xc7, 0x35,
+		0x39, 0x99, 0x66, 0x6f, 0x1, 0x12, 0x89, 0xe5, 0x20, 0xc7,
+		0xc8, 0xf8, 0xa9, 0x2d, 0x8d, 0x65, 0x20, 0xe0, 0xe8, 0x9a,
+		0xf8, 0xd2, 0x3a, 0xbc, 0xa7, 0xf, 0xa4, 0x5a, 0x31, 0x85,
+		0x29, 0xe5, 0x1a, 0x0, 0xad, 0xbd, 0xf1, 0x1a, 0xab, 0x9f,
+		0xc7, 0xe2, 0x41, 0xc9, 0xa7, 0xde, 0x5e, 0x3a, 0x99, 0xc5,
+		0xb0, 0xbb, 0xe2, 0xc3, 0x6b, 0x1e, 0x1c, 0xd9, 0x33, 0xfc,
+		0xbc, 0x49, 0x31, 0x13, 0xf5, 0x5f, 0x8d, 0xbc, 0xf8, 0x3a,
+		0x58, 0x5b, 0xf4, 0x3, 0xff, 0x42, 0x54, 0xb4, 0x94, 0xae,
+		0xb, 0xfa, 0xbd, 0x15, 0x41, 0xcb, 0xe9, 0x12, 0x37, 0xbb,
+		0xf0, 0x2c, 0xae, 0xff, 0x29, 0x9, 0xbe, 0x3e, 0xf, 0xb8,
+		0xb5, 0x8d, 0x6f, 0xc0, 0x30, 0x87, 0x49, 0x4e, 0xdc, 0x9c,
+		0x38, 0x6b, 0x1b, 0x3f, 0x14, 0x0, 0xef, 0x21, 0xcc, 0x5a,
+		0xe8, 0xc7, 0x99, 0xe6, 0xf5, 0x5, 0x38, 0x87, 0x70, 0xbd,
+		0xec, 0xdc, 0xaa, 0xc9, 0xbb, 0x5b, 0xc3, 0x56, 0xbb, 0x21,
+		0xbf, 0x17, 0xe7, 0xcf, 0xbd, 0x4a, 0x4d, 0xe3, 0x67, 0x64,
+		0x7f, 0x14, 0x6c, 0xea, 0x93, 0xe6, 0x2e, 0xdf, 0x3c, 0x6c,
+		0x97, 0xb5, 0x8d, 0x57, 0x25, 0xd7, 0x5c, 0x6c, 0x8f, 0xd0,
+		0xea, 0xd5, 0xdf, 0xc0, 0x71, 0x6c, 0x65, 0xcd, 0xb4, 0x4f,
+		0x34, 0x9d, 0xb1, 0x52, 0xc1, 0xb7, 0x9, 0x2c, 0x51, 0xa7,
+		0x29, 0x6c, 0x3a, 0x20, 0x70, 0x45, 0x4c, 0x72, 0xd9, 0xcd,
+		0xac, 0x1f, 0x5, 0x22, 0xb0, 0x77, 0xbd, 0x91, 0x2f, 0xf5,
+		0xd, 0x19, 0xd5, 0x57, 0x98, 0xee, 0x79, 0x93, 0xa4, 0x5f,
+		0xba, 0x6b, 0xec, 0xf6, 0x3f, 0xb6, 0x9c, 0x2f, 0xb8, 0xfa,
+		0x3, 0xa3, 0xeb, 0xdf, 0xea, 0xbc, 0x3f, 0xd0, 0x8f, 0x88,
+		0xf0, 0xbb, 0xcc, 0x5a, 0x27, 0x57, 0x3b, 0x95, 0x3f, 0x20,
+		0x7c, 0x19, 0xc8, 0x46, 0x47, 0x68, 0x72, 0xb7, 0x28, 0x8e,
+		0x56, 0x9b, 0x83, 0xf7, 0xe9, 0x3c, 0x85, 0xcb, 0xb0, 0x65,
+		0x60, 0x1a, 0x52, 0x85, 0x6d, 0x58, 0x84, 0x39, 0xd9, 0xa2,
+		0x92, 0xd2, 0x9d, 0x7d, 0x1b, 0xdf, 0x61, 0x85, 0xbf, 0x88,
+		0x54, 0x3, 0x42, 0xe1, 0xa9, 0x24, 0x74, 0x75, 0x78, 0x48,
+		0xff, 0x22, 0xec, 0xc5, 0x4d, 0x66, 0x17, 0xd4, 0x9a,
+	},
+}
+
+var privateKey2 = &Block{
+	Type: "RSA PRIVATE KEY",
+	Headers: map[string]string{
+		"Proc-Type":      "4,ENCRYPTED",
+		"DEK-Info":       "AES-128-CBC,BFCD243FEDBB40A4AA6DDAA1335473A4",
+		"Content-Domain": "RFC822",
+	},
+	Bytes: []uint8{
+		0xa8, 0x35, 0xcc, 0x2b, 0xb9, 0xcb, 0x21, 0xab, 0xc0,
+		0x9d, 0x76, 0x61, 0x0, 0xf4, 0x81, 0xad, 0x69, 0xd2,
+		0xc0, 0x42, 0x41, 0x3b, 0xe4, 0x3c, 0xaf, 0x59, 0x5e,
+		0x6d, 0x2a, 0x3c, 0x9c, 0xa1, 0xa4, 0x5e, 0x68, 0x37,
+		0xc4, 0x8c, 0x70, 0x1c, 0xa9, 0x18, 0xe6, 0xc2, 0x2b,
+		0x8a, 0x91, 0xdc, 0x2d, 0x1f, 0x8, 0x23, 0x39, 0xf1,
+		0x4b, 0x8b, 0x1b, 0x2f, 0x46, 0xb, 0xb2, 0x26, 0xba,
+		0x4f, 0x40, 0x80, 0x39, 0xc4, 0xb1, 0xcb, 0x3b, 0xb4,
+		0x65, 0x3f, 0x1b, 0xb2, 0xf7, 0x8, 0xd2, 0xc6, 0xd5,
+		0xa8, 0x9f, 0x23, 0x69, 0xb6, 0x3d, 0xf9, 0xac, 0x1c,
+		0xb3, 0x13, 0x87, 0x64, 0x4, 0x37, 0xdb, 0x40, 0xc8,
+		0x82, 0xc, 0xd0, 0xf8, 0x21, 0x7c, 0xdc, 0xbd, 0x9, 0x4,
+		0x20, 0x16, 0xb0, 0x97, 0xe2, 0x6d, 0x56, 0x1d, 0xe3,
+		0xec, 0xf0, 0xfc, 0xe2, 0x56, 0xad, 0xa4, 0x3, 0x70,
+		0x6d, 0x63, 0x3c, 0x1, 0xbe, 0x3e, 0x28, 0x38, 0x6f,
+		0xc0, 0xe6, 0xfd, 0x85, 0xd1, 0x53, 0xa8, 0x9b, 0xcb,
+		0xd4, 0x4, 0xb1, 0x73, 0xb9, 0x73, 0x32, 0xd6, 0x7a,
+		0xc6, 0x29, 0x25, 0xa5, 0xda, 0x17, 0x93, 0x7a, 0x10,
+		0xe8, 0x41, 0xfb, 0xa5, 0x17, 0x20, 0xf8, 0x4e, 0xe9,
+		0xe3, 0x8f, 0x51, 0x20, 0x13, 0xbb, 0xde, 0xb7, 0x93,
+		0xae, 0x13, 0x8a, 0xf6, 0x9, 0xf4, 0xa6, 0x41, 0xe0,
+		0x2b, 0x51, 0x1a, 0x30, 0x38, 0xd, 0xb1, 0x3b, 0x67,
+		0x87, 0x64, 0xf5, 0xca, 0x32, 0x67, 0xd1, 0xc8, 0xa5,
+		0x3d, 0x23, 0x72, 0xc4, 0x6, 0xaf, 0x8f, 0x7b, 0x26,
+		0xac, 0x3c, 0x75, 0x91, 0xa1, 0x0, 0x13, 0xc6, 0x5c,
+		0x49, 0xd5, 0x3c, 0xe7, 0xb2, 0xb2, 0x99, 0xe0, 0xd5,
+		0x25, 0xfa, 0xe2, 0x12, 0x80, 0x37, 0x85, 0xcf, 0x92,
+		0xca, 0x1b, 0x9f, 0xf3, 0x4e, 0xd8, 0x80, 0xef, 0x3c,
+		0xce, 0xcd, 0xf5, 0x90, 0x9e, 0xf9, 0xa7, 0xb2, 0xc,
+		0x49, 0x4, 0xf1, 0x9, 0x8f, 0xea, 0x63, 0xd2, 0x70,
+		0xbb, 0x86, 0xbf, 0x34, 0xab, 0xb2, 0x3, 0xb1, 0x59,
+		0x33, 0x16, 0x17, 0xb0, 0xdb, 0x77, 0x38, 0xf4, 0xb4,
+		0x94, 0xb, 0x25, 0x16, 0x7e, 0x22, 0xd4, 0xf9, 0x22,
+		0xb9, 0x78, 0xa3, 0x4, 0x84, 0x4, 0xd2, 0xda, 0x84,
+		0x2d, 0x63, 0xdd, 0xf8, 0x50, 0x6a, 0xf6, 0xe3, 0xf5,
+		0x65, 0x40, 0x7c, 0xa9,
+	},
+}
+
+var pemPrivateKey2 = testingKey(`-----BEGIN RSA TESTING KEY-----
+Proc-Type: 4,ENCRYPTED
+Content-Domain: RFC822
+DEK-Info: AES-128-CBC,BFCD243FEDBB40A4AA6DDAA1335473A4
+
+qDXMK7nLIavAnXZhAPSBrWnSwEJBO+Q8r1lebSo8nKGkXmg3xIxwHKkY5sIripHc
+LR8IIznxS4sbL0YLsia6T0CAOcSxyzu0ZT8bsvcI0sbVqJ8jabY9+awcsxOHZAQ3
+20DIggzQ+CF83L0JBCAWsJfibVYd4+zw/OJWraQDcG1jPAG+Pig4b8Dm/YXRU6ib
+y9QEsXO5czLWesYpJaXaF5N6EOhB+6UXIPhO6eOPUSATu963k64TivYJ9KZB4CtR
+GjA4DbE7Z4dk9coyZ9HIpT0jcsQGr497Jqw8dZGhABPGXEnVPOeyspng1SX64hKA
+N4XPksobn/NO2IDvPM7N9ZCe+aeyDEkE8QmP6mPScLuGvzSrsgOxWTMWF7Dbdzj0
+tJQLJRZ+ItT5Irl4owSEBNLahC1j3fhQavbj9WVAfKk=
+-----END RSA TESTING KEY-----
+`)
+
+func TestBadEncode(t *testing.T) {
+	b := &Block{Type: "BAD", Headers: map[string]string{"X:Y": "Z"}}
+	var buf bytes.Buffer
+	if err := Encode(&buf, b); err == nil {
+		t.Fatalf("Encode did not report invalid header")
+	}
+	if buf.Len() != 0 {
+		t.Fatalf("Encode wrote data before reporting invalid header")
+	}
+	if data := EncodeToMemory(b); data != nil {
+		t.Fatalf("EncodeToMemory returned non-nil data")
+	}
+}
+
+func testingKey(s string) string { return strings.ReplaceAll(s, "TESTING KEY", "PRIVATE KEY") }
diff --git a/src/encoding/xml/atom_test.go b/src/encoding/xml/atom_test.go
new file mode 100644
index 0000000..f394dab
--- /dev/null
+++ b/src/encoding/xml/atom_test.go
@@ -0,0 +1,56 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package xml
+
+import "time"
+
+var atomValue = &Feed{
+	XMLName: Name{"http://www.w3.org/2005/Atom", "feed"},
+	Title:   "Example Feed",
+	Link:    []Link{{Href: "http://example.org/"}},
+	Updated: ParseTime("2003-12-13T18:30:02Z"),
+	Author:  Person{Name: "John Doe"},
+	ID:      "urn:uuid:60a76c80-d399-11d9-b93C-0003939e0af6",
+
+	Entry: []Entry{
+		{
+			Title:   "Atom-Powered Robots Run Amok",
+			Link:    []Link{{Href: "http://example.org/2003/12/13/atom03"}},
+			ID:      "urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a",
+			Updated: ParseTime("2003-12-13T18:30:02Z"),
+			Summary: NewText("Some text."),
+		},
+	},
+}
+
+var atomXML = `` +
+	`<feed xmlns="http://www.w3.org/2005/Atom" updated="2003-12-13T18:30:02Z">` +
+	`<title>Example Feed</title>` +
+	`<id>urn:uuid:60a76c80-d399-11d9-b93C-0003939e0af6</id>` +
+	`<link href="http://example.org/"></link>` +
+	`<author><name>John Doe</name><uri></uri><email></email></author>` +
+	`<entry>` +
+	`<title>Atom-Powered Robots Run Amok</title>` +
+	`<id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a</id>` +
+	`<link href="http://example.org/2003/12/13/atom03"></link>` +
+	`<updated>2003-12-13T18:30:02Z</updated>` +
+	`<author><name></name><uri></uri><email></email></author>` +
+	`<summary>Some text.</summary>` +
+	`</entry>` +
+	`</feed>`
+
+func ParseTime(str string) time.Time {
+	t, err := time.Parse(time.RFC3339, str)
+	if err != nil {
+		panic(err)
+	}
+	return t
+}
+
+func NewText(text string) Text {
+	return Text{
+		Body: text,
+	}
+}
diff --git a/src/encoding/xml/example_marshaling_test.go b/src/encoding/xml/example_marshaling_test.go
new file mode 100644
index 0000000..9f9e801
--- /dev/null
+++ b/src/encoding/xml/example_marshaling_test.go
@@ -0,0 +1,84 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package xml_test
+
+import (
+	"encoding/xml"
+	"fmt"
+	"log"
+	"strings"
+)
+
+type Animal int
+
+const (
+	Unknown Animal = iota
+	Gopher
+	Zebra
+)
+
+func (a *Animal) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {
+	var s string
+	if err := d.DecodeElement(&s, &start); err != nil {
+		return err
+	}
+	switch strings.ToLower(s) {
+	default:
+		*a = Unknown
+	case "gopher":
+		*a = Gopher
+	case "zebra":
+		*a = Zebra
+	}
+
+	return nil
+}
+
+func (a Animal) MarshalXML(e *xml.Encoder, start xml.StartElement) error {
+	var s string
+	switch a {
+	default:
+		s = "unknown"
+	case Gopher:
+		s = "gopher"
+	case Zebra:
+		s = "zebra"
+	}
+	return e.EncodeElement(s, start)
+}
+
+func Example_customMarshalXML() {
+	blob := `
+	<animals>
+		<animal>gopher</animal>
+		<animal>armadillo</animal>
+		<animal>zebra</animal>
+		<animal>unknown</animal>
+		<animal>gopher</animal>
+		<animal>bee</animal>
+		<animal>gopher</animal>
+		<animal>zebra</animal>
+	</animals>`
+	var zoo struct {
+		Animals []Animal `xml:"animal"`
+	}
+	if err := xml.Unmarshal([]byte(blob), &zoo); err != nil {
+		log.Fatal(err)
+	}
+
+	census := make(map[Animal]int)
+	for _, animal := range zoo.Animals {
+		census[animal] += 1
+	}
+
+	fmt.Printf("Zoo Census:\n* Gophers: %d\n* Zebras:  %d\n* Unknown: %d\n",
+		census[Gopher], census[Zebra], census[Unknown])
+
+	// Output:
+	// Zoo Census:
+	// * Gophers: 3
+	// * Zebras:  2
+	// * Unknown: 3
+}
diff --git a/src/encoding/xml/example_test.go b/src/encoding/xml/example_test.go
new file mode 100644
index 0000000..21b48de
--- /dev/null
+++ b/src/encoding/xml/example_test.go
@@ -0,0 +1,151 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package xml_test
+
+import (
+	"encoding/xml"
+	"fmt"
+	"os"
+)
+
+func ExampleMarshalIndent() {
+	type Address struct {
+		City, State string
+	}
+	type Person struct {
+		XMLName   xml.Name `xml:"person"`
+		Id        int      `xml:"id,attr"`
+		FirstName string   `xml:"name>first"`
+		LastName  string   `xml:"name>last"`
+		Age       int      `xml:"age"`
+		Height    float32  `xml:"height,omitempty"`
+		Married   bool
+		Address
+		Comment string `xml:",comment"`
+	}
+
+	v := &Person{Id: 13, FirstName: "John", LastName: "Doe", Age: 42}
+	v.Comment = " Need more details. "
+	v.Address = Address{"Hanga Roa", "Easter Island"}
+
+	output, err := xml.MarshalIndent(v, "  ", "    ")
+	if err != nil {
+		fmt.Printf("error: %v\n", err)
+	}
+
+	os.Stdout.Write(output)
+	// Output:
+	//   <person id="13">
+	//       <name>
+	//           <first>John</first>
+	//           <last>Doe</last>
+	//       </name>
+	//       <age>42</age>
+	//       <Married>false</Married>
+	//       <City>Hanga Roa</City>
+	//       <State>Easter Island</State>
+	//       <!-- Need more details. -->
+	//   </person>
+}
+
+func ExampleEncoder() {
+	type Address struct {
+		City, State string
+	}
+	type Person struct {
+		XMLName   xml.Name `xml:"person"`
+		Id        int      `xml:"id,attr"`
+		FirstName string   `xml:"name>first"`
+		LastName  string   `xml:"name>last"`
+		Age       int      `xml:"age"`
+		Height    float32  `xml:"height,omitempty"`
+		Married   bool
+		Address
+		Comment string `xml:",comment"`
+	}
+
+	v := &Person{Id: 13, FirstName: "John", LastName: "Doe", Age: 42}
+	v.Comment = " Need more details. "
+	v.Address = Address{"Hanga Roa", "Easter Island"}
+
+	enc := xml.NewEncoder(os.Stdout)
+	enc.Indent("  ", "    ")
+	if err := enc.Encode(v); err != nil {
+		fmt.Printf("error: %v\n", err)
+	}
+
+	// Output:
+	//   <person id="13">
+	//       <name>
+	//           <first>John</first>
+	//           <last>Doe</last>
+	//       </name>
+	//       <age>42</age>
+	//       <Married>false</Married>
+	//       <City>Hanga Roa</City>
+	//       <State>Easter Island</State>
+	//       <!-- Need more details. -->
+	//   </person>
+}
+
+// This example demonstrates unmarshaling an XML excerpt into a value with
+// some preset fields. Note that the Phone field isn't modified and that
+// the XML <Company> element is ignored. Also, the Groups field is assigned
+// considering the element path provided in its tag.
+func ExampleUnmarshal() {
+	type Email struct {
+		Where string `xml:"where,attr"`
+		Addr  string
+	}
+	type Address struct {
+		City, State string
+	}
+	type Result struct {
+		XMLName xml.Name `xml:"Person"`
+		Name    string   `xml:"FullName"`
+		Phone   string
+		Email   []Email
+		Groups  []string `xml:"Group>Value"`
+		Address
+	}
+	v := Result{Name: "none", Phone: "none"}
+
+	data := `
+		<Person>
+			<FullName>Grace R. Emlin</FullName>
+			<Company>Example Inc.</Company>
+			<Email where="home">
+				<Addr>gre@example.com</Addr>
+			</Email>
+			<Email where='work'>
+				<Addr>gre@work.com</Addr>
+			</Email>
+			<Group>
+				<Value>Friends</Value>
+				<Value>Squash</Value>
+			</Group>
+			<City>Hanga Roa</City>
+			<State>Easter Island</State>
+		</Person>
+	`
+	err := xml.Unmarshal([]byte(data), &v)
+	if err != nil {
+		fmt.Printf("error: %v", err)
+		return
+	}
+	fmt.Printf("XMLName: %#v\n", v.XMLName)
+	fmt.Printf("Name: %q\n", v.Name)
+	fmt.Printf("Phone: %q\n", v.Phone)
+	fmt.Printf("Email: %v\n", v.Email)
+	fmt.Printf("Groups: %v\n", v.Groups)
+	fmt.Printf("Address: %v\n", v.Address)
+	// Output:
+	// XMLName: xml.Name{Space:"", Local:"Person"}
+	// Name: "Grace R. Emlin"
+	// Phone: "none"
+	// Email: [{home gre@example.com} {work gre@work.com}]
+	// Groups: [Friends Squash]
+	// Address: {Hanga Roa Easter Island}
+}
diff --git a/src/encoding/xml/example_text_marshaling_test.go b/src/encoding/xml/example_text_marshaling_test.go
new file mode 100644
index 0000000..2549cb1
--- /dev/null
+++ b/src/encoding/xml/example_text_marshaling_test.go
@@ -0,0 +1,79 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package xml_test
+
+import (
+	"encoding/xml"
+	"fmt"
+	"log"
+	"strings"
+)
+
+type Size int
+
+const (
+	Unrecognized Size = iota
+	Small
+	Large
+)
+
+func (s *Size) UnmarshalText(text []byte) error {
+	switch strings.ToLower(string(text)) {
+	default:
+		*s = Unrecognized
+	case "small":
+		*s = Small
+	case "large":
+		*s = Large
+	}
+	return nil
+}
+
+func (s Size) MarshalText() ([]byte, error) {
+	var name string
+	switch s {
+	default:
+		name = "unrecognized"
+	case Small:
+		name = "small"
+	case Large:
+		name = "large"
+	}
+	return []byte(name), nil
+}
+
+func Example_textMarshalXML() {
+	blob := `
+	<sizes>
+		<size>small</size>
+		<size>regular</size>
+		<size>large</size>
+		<size>unrecognized</size>
+		<size>small</size>
+		<size>normal</size>
+		<size>small</size>
+		<size>large</size>
+	</sizes>`
+	var inventory struct {
+		Sizes []Size `xml:"size"`
+	}
+	if err := xml.Unmarshal([]byte(blob), &inventory); err != nil {
+		log.Fatal(err)
+	}
+
+	counts := make(map[Size]int)
+	for _, size := range inventory.Sizes {
+		counts[size] += 1
+	}
+
+	fmt.Printf("Inventory Counts:\n* Small:        %d\n* Large:        %d\n* Unrecognized: %d\n",
+		counts[Small], counts[Large], counts[Unrecognized])
+
+	// Output:
+	// Inventory Counts:
+	// * Small:        3
+	// * Large:        2
+	// * Unrecognized: 3
+}
diff --git a/src/encoding/xml/marshal.go b/src/encoding/xml/marshal.go
new file mode 100644
index 0000000..7792ac7
--- /dev/null
+++ b/src/encoding/xml/marshal.go
@@ -0,0 +1,1062 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package xml
+
+import (
+	"bufio"
+	"bytes"
+	"encoding"
+	"fmt"
+	"io"
+	"reflect"
+	"strconv"
+	"strings"
+)
+
+const (
+	// Header is a generic XML header suitable for use with the output of Marshal.
+	// This is not automatically added to any output of this package,
+	// it is provided as a convenience.
+	Header = `<?xml version="1.0" encoding="UTF-8"?>` + "\n"
+)
+
+// Marshal returns the XML encoding of v.
+//
+// Marshal handles an array or slice by marshaling each of the elements.
+// Marshal handles a pointer by marshaling the value it points at or, if the
+// pointer is nil, by writing nothing. Marshal handles an interface value by
+// marshaling the value it contains or, if the interface value is nil, by
+// writing nothing. Marshal handles all other data by writing one or more XML
+// elements containing the data.
+//
+// The name for the XML elements is taken from, in order of preference:
+//     - the tag on the XMLName field, if the data is a struct
+//     - the value of the XMLName field of type Name
+//     - the tag of the struct field used to obtain the data
+//     - the name of the struct field used to obtain the data
+//     - the name of the marshaled type
+//
+// The XML element for a struct contains marshaled elements for each of the
+// exported fields of the struct, with these exceptions:
+//     - the XMLName field, described above, is omitted.
+//     - a field with tag "-" is omitted.
+//     - a field with tag "name,attr" becomes an attribute with
+//       the given name in the XML element.
+//     - a field with tag ",attr" becomes an attribute with the
+//       field name in the XML element.
+//     - a field with tag ",chardata" is written as character data,
+//       not as an XML element.
+//     - a field with tag ",cdata" is written as character data
+//       wrapped in one or more <![CDATA[ ... ]]> tags, not as an XML element.
+//     - a field with tag ",innerxml" is written verbatim, not subject
+//       to the usual marshaling procedure.
+//     - a field with tag ",comment" is written as an XML comment, not
+//       subject to the usual marshaling procedure. It must not contain
+//       the "--" string within it.
+//     - a field with a tag including the "omitempty" option is omitted
+//       if the field value is empty. The empty values are false, 0, any
+//       nil pointer or interface value, and any array, slice, map, or
+//       string of length zero.
+//     - an anonymous struct field is handled as if the fields of its
+//       value were part of the outer struct.
+//     - a field implementing Marshaler is written by calling its MarshalXML
+//       method.
+//     - a field implementing encoding.TextMarshaler is written by encoding the
+//       result of its MarshalText method as text.
+//
+// If a field uses a tag "a>b>c", then the element c will be nested inside
+// parent elements a and b. Fields that appear next to each other that name
+// the same parent will be enclosed in one XML element.
+//
+// If the XML name for a struct field is defined by both the field tag and the
+// struct's XMLName field, the names must match.
+//
+// See MarshalIndent for an example.
+//
+// Marshal will return an error if asked to marshal a channel, function, or map.
+func Marshal(v any) ([]byte, error) {
+	var b bytes.Buffer
+	if err := NewEncoder(&b).Encode(v); err != nil {
+		return nil, err
+	}
+	return b.Bytes(), nil
+}
+
+// Marshaler is the interface implemented by objects that can marshal
+// themselves into valid XML elements.
+//
+// MarshalXML encodes the receiver as zero or more XML elements.
+// By convention, arrays or slices are typically encoded as a sequence
+// of elements, one per entry.
+// Using start as the element tag is not required, but doing so
+// will enable Unmarshal to match the XML elements to the correct
+// struct field.
+// One common implementation strategy is to construct a separate
+// value with a layout corresponding to the desired XML and then
+// to encode it using e.EncodeElement.
+// Another common strategy is to use repeated calls to e.EncodeToken
+// to generate the XML output one token at a time.
+// The sequence of encoded tokens must make up zero or more valid
+// XML elements.
+type Marshaler interface {
+	MarshalXML(e *Encoder, start StartElement) error
+}
+
+// MarshalerAttr is the interface implemented by objects that can marshal
+// themselves into valid XML attributes.
+//
+// MarshalXMLAttr returns an XML attribute with the encoded value of the receiver.
+// Using name as the attribute name is not required, but doing so
+// will enable Unmarshal to match the attribute to the correct
+// struct field.
+// If MarshalXMLAttr returns the zero attribute Attr{}, no attribute
+// will be generated in the output.
+// MarshalXMLAttr is used only for struct fields with the
+// "attr" option in the field tag.
+type MarshalerAttr interface {
+	MarshalXMLAttr(name Name) (Attr, error)
+}
+
+// MarshalIndent works like Marshal, but each XML element begins on a new
+// indented line that starts with prefix and is followed by one or more
+// copies of indent according to the nesting depth.
+func MarshalIndent(v any, prefix, indent string) ([]byte, error) {
+	var b bytes.Buffer
+	enc := NewEncoder(&b)
+	enc.Indent(prefix, indent)
+	if err := enc.Encode(v); err != nil {
+		return nil, err
+	}
+	return b.Bytes(), nil
+}
+
+// An Encoder writes XML data to an output stream.
+type Encoder struct {
+	p printer
+}
+
+// NewEncoder returns a new encoder that writes to w.
+func NewEncoder(w io.Writer) *Encoder {
+	e := &Encoder{printer{Writer: bufio.NewWriter(w)}}
+	e.p.encoder = e
+	return e
+}
+
+// Indent sets the encoder to generate XML in which each element
+// begins on a new indented line that starts with prefix and is followed by
+// one or more copies of indent according to the nesting depth.
+func (enc *Encoder) Indent(prefix, indent string) {
+	enc.p.prefix = prefix
+	enc.p.indent = indent
+}
+
+// Encode writes the XML encoding of v to the stream.
+//
+// See the documentation for Marshal for details about the conversion
+// of Go values to XML.
+//
+// Encode calls Flush before returning.
+func (enc *Encoder) Encode(v any) error {
+	err := enc.p.marshalValue(reflect.ValueOf(v), nil, nil)
+	if err != nil {
+		return err
+	}
+	return enc.p.Flush()
+}
+
+// EncodeElement writes the XML encoding of v to the stream,
+// using start as the outermost tag in the encoding.
+//
+// See the documentation for Marshal for details about the conversion
+// of Go values to XML.
+//
+// EncodeElement calls Flush before returning.
+func (enc *Encoder) EncodeElement(v any, start StartElement) error {
+	err := enc.p.marshalValue(reflect.ValueOf(v), nil, &start)
+	if err != nil {
+		return err
+	}
+	return enc.p.Flush()
+}
+
+var (
+	begComment  = []byte("<!--")
+	endComment  = []byte("-->")
+	endProcInst = []byte("?>")
+)
+
+// EncodeToken writes the given XML token to the stream.
+// It returns an error if StartElement and EndElement tokens are not properly matched.
+//
+// EncodeToken does not call Flush, because usually it is part of a larger operation
+// such as Encode or EncodeElement (or a custom Marshaler's MarshalXML invoked
+// during those), and those will call Flush when finished.
+// Callers that create an Encoder and then invoke EncodeToken directly, without
+// using Encode or EncodeElement, need to call Flush when finished to ensure
+// that the XML is written to the underlying writer.
+//
+// EncodeToken allows writing a ProcInst with Target set to "xml" only as the first token
+// in the stream.
+func (enc *Encoder) EncodeToken(t Token) error {
+
+	p := &enc.p
+	switch t := t.(type) {
+	case StartElement:
+		if err := p.writeStart(&t); err != nil {
+			return err
+		}
+	case EndElement:
+		if err := p.writeEnd(t.Name); err != nil {
+			return err
+		}
+	case CharData:
+		escapeText(p, t, false)
+	case Comment:
+		if bytes.Contains(t, endComment) {
+			return fmt.Errorf("xml: EncodeToken of Comment containing --> marker")
+		}
+		p.WriteString("<!--")
+		p.Write(t)
+		p.WriteString("-->")
+		return p.cachedWriteError()
+	case ProcInst:
+		// First token to be encoded which is also a ProcInst with target of xml
+		// is the xml declaration. The only ProcInst where target of xml is allowed.
+		if t.Target == "xml" && p.Buffered() != 0 {
+			return fmt.Errorf("xml: EncodeToken of ProcInst xml target only valid for xml declaration, first token encoded")
+		}
+		if !isNameString(t.Target) {
+			return fmt.Errorf("xml: EncodeToken of ProcInst with invalid Target")
+		}
+		if bytes.Contains(t.Inst, endProcInst) {
+			return fmt.Errorf("xml: EncodeToken of ProcInst containing ?> marker")
+		}
+		p.WriteString("<?")
+		p.WriteString(t.Target)
+		if len(t.Inst) > 0 {
+			p.WriteByte(' ')
+			p.Write(t.Inst)
+		}
+		p.WriteString("?>")
+	case Directive:
+		if !isValidDirective(t) {
+			return fmt.Errorf("xml: EncodeToken of Directive containing wrong < or > markers")
+		}
+		p.WriteString("<!")
+		p.Write(t)
+		p.WriteString(">")
+	default:
+		return fmt.Errorf("xml: EncodeToken of invalid token type")
+
+	}
+	return p.cachedWriteError()
+}
+
+// isValidDirective reports whether dir is a valid directive text,
+// meaning angle brackets are matched, ignoring comments and strings.
+func isValidDirective(dir Directive) bool {
+	var (
+		depth     int
+		inquote   uint8
+		incomment bool
+	)
+	for i, c := range dir {
+		switch {
+		case incomment:
+			if c == '>' {
+				if n := 1 + i - len(endComment); n >= 0 && bytes.Equal(dir[n:i+1], endComment) {
+					incomment = false
+				}
+			}
+			// Just ignore anything in comment
+		case inquote != 0:
+			if c == inquote {
+				inquote = 0
+			}
+			// Just ignore anything within quotes
+		case c == '\'' || c == '"':
+			inquote = c
+		case c == '<':
+			if i+len(begComment) < len(dir) && bytes.Equal(dir[i:i+len(begComment)], begComment) {
+				incomment = true
+			} else {
+				depth++
+			}
+		case c == '>':
+			if depth == 0 {
+				return false
+			}
+			depth--
+		}
+	}
+	return depth == 0 && inquote == 0 && !incomment
+}
+
+// Flush flushes any buffered XML to the underlying writer.
+// See the EncodeToken documentation for details about when it is necessary.
+func (enc *Encoder) Flush() error {
+	return enc.p.Flush()
+}
+
+type printer struct {
+	*bufio.Writer
+	encoder    *Encoder
+	seq        int
+	indent     string
+	prefix     string
+	depth      int
+	indentedIn bool
+	putNewline bool
+	attrNS     map[string]string // map prefix -> name space
+	attrPrefix map[string]string // map name space -> prefix
+	prefixes   []string
+	tags       []Name
+}
+
+// createAttrPrefix finds the name space prefix attribute to use for the given name space,
+// defining a new prefix if necessary. It returns the prefix.
+func (p *printer) createAttrPrefix(url string) string {
+	if prefix := p.attrPrefix[url]; prefix != "" {
+		return prefix
+	}
+
+	// The "http://www.w3.org/XML/1998/namespace" name space is predefined as "xml"
+	// and must be referred to that way.
+	// (The "http://www.w3.org/2000/xmlns/" name space is also predefined as "xmlns",
+	// but users should not be trying to use that one directly - that's our job.)
+	if url == xmlURL {
+		return xmlPrefix
+	}
+
+	// Need to define a new name space.
+	if p.attrPrefix == nil {
+		p.attrPrefix = make(map[string]string)
+		p.attrNS = make(map[string]string)
+	}
+
+	// Pick a name. We try to use the final element of the path
+	// but fall back to _.
+	prefix := strings.TrimRight(url, "/")
+	if i := strings.LastIndex(prefix, "/"); i >= 0 {
+		prefix = prefix[i+1:]
+	}
+	if prefix == "" || !isName([]byte(prefix)) || strings.Contains(prefix, ":") {
+		prefix = "_"
+	}
+	// xmlanything is reserved and any variant of it regardless of
+	// case should be matched, so:
+	//    (('X'|'x') ('M'|'m') ('L'|'l'))
+	// See Section 2.3 of https://www.w3.org/TR/REC-xml/
+	if len(prefix) >= 3 && strings.EqualFold(prefix[:3], "xml") {
+		prefix = "_" + prefix
+	}
+	if p.attrNS[prefix] != "" {
+		// Name is taken. Find a better one.
+		for p.seq++; ; p.seq++ {
+			if id := prefix + "_" + strconv.Itoa(p.seq); p.attrNS[id] == "" {
+				prefix = id
+				break
+			}
+		}
+	}
+
+	p.attrPrefix[url] = prefix
+	p.attrNS[prefix] = url
+
+	p.WriteString(`xmlns:`)
+	p.WriteString(prefix)
+	p.WriteString(`="`)
+	EscapeText(p, []byte(url))
+	p.WriteString(`" `)
+
+	p.prefixes = append(p.prefixes, prefix)
+
+	return prefix
+}
+
+// deleteAttrPrefix removes an attribute name space prefix.
+func (p *printer) deleteAttrPrefix(prefix string) {
+	delete(p.attrPrefix, p.attrNS[prefix])
+	delete(p.attrNS, prefix)
+}
+
+func (p *printer) markPrefix() {
+	p.prefixes = append(p.prefixes, "")
+}
+
+func (p *printer) popPrefix() {
+	for len(p.prefixes) > 0 {
+		prefix := p.prefixes[len(p.prefixes)-1]
+		p.prefixes = p.prefixes[:len(p.prefixes)-1]
+		if prefix == "" {
+			break
+		}
+		p.deleteAttrPrefix(prefix)
+	}
+}
+
+var (
+	marshalerType     = reflect.TypeOf((*Marshaler)(nil)).Elem()
+	marshalerAttrType = reflect.TypeOf((*MarshalerAttr)(nil)).Elem()
+	textMarshalerType = reflect.TypeOf((*encoding.TextMarshaler)(nil)).Elem()
+)
+
+// marshalValue writes one or more XML elements representing val.
+// If val was obtained from a struct field, finfo must have its details.
+func (p *printer) marshalValue(val reflect.Value, finfo *fieldInfo, startTemplate *StartElement) error {
+	if startTemplate != nil && startTemplate.Name.Local == "" {
+		return fmt.Errorf("xml: EncodeElement of StartElement with missing name")
+	}
+
+	if !val.IsValid() {
+		return nil
+	}
+	if finfo != nil && finfo.flags&fOmitEmpty != 0 && isEmptyValue(val) {
+		return nil
+	}
+
+	// Drill into interfaces and pointers.
+	// This can turn into an infinite loop given a cyclic chain,
+	// but it matches the Go 1 behavior.
+	for val.Kind() == reflect.Interface || val.Kind() == reflect.Pointer {
+		if val.IsNil() {
+			return nil
+		}
+		val = val.Elem()
+	}
+
+	kind := val.Kind()
+	typ := val.Type()
+
+	// Check for marshaler.
+	if val.CanInterface() && typ.Implements(marshalerType) {
+		return p.marshalInterface(val.Interface().(Marshaler), defaultStart(typ, finfo, startTemplate))
+	}
+	if val.CanAddr() {
+		pv := val.Addr()
+		if pv.CanInterface() && pv.Type().Implements(marshalerType) {
+			return p.marshalInterface(pv.Interface().(Marshaler), defaultStart(pv.Type(), finfo, startTemplate))
+		}
+	}
+
+	// Check for text marshaler.
+	if val.CanInterface() && typ.Implements(textMarshalerType) {
+		return p.marshalTextInterface(val.Interface().(encoding.TextMarshaler), defaultStart(typ, finfo, startTemplate))
+	}
+	if val.CanAddr() {
+		pv := val.Addr()
+		if pv.CanInterface() && pv.Type().Implements(textMarshalerType) {
+			return p.marshalTextInterface(pv.Interface().(encoding.TextMarshaler), defaultStart(pv.Type(), finfo, startTemplate))
+		}
+	}
+
+	// Slices and arrays iterate over the elements. They do not have an enclosing tag.
+	if (kind == reflect.Slice || kind == reflect.Array) && typ.Elem().Kind() != reflect.Uint8 {
+		for i, n := 0, val.Len(); i < n; i++ {
+			if err := p.marshalValue(val.Index(i), finfo, startTemplate); err != nil {
+				return err
+			}
+		}
+		return nil
+	}
+
+	tinfo, err := getTypeInfo(typ)
+	if err != nil {
+		return err
+	}
+
+	// Create start element.
+	// Precedence for the XML element name is:
+	// 0. startTemplate
+	// 1. XMLName field in underlying struct;
+	// 2. field name/tag in the struct field; and
+	// 3. type name
+	var start StartElement
+
+	if startTemplate != nil {
+		start.Name = startTemplate.Name
+		start.Attr = append(start.Attr, startTemplate.Attr...)
+	} else if tinfo.xmlname != nil {
+		xmlname := tinfo.xmlname
+		if xmlname.name != "" {
+			start.Name.Space, start.Name.Local = xmlname.xmlns, xmlname.name
+		} else {
+			fv := xmlname.value(val, dontInitNilPointers)
+			if v, ok := fv.Interface().(Name); ok && v.Local != "" {
+				start.Name = v
+			}
+		}
+	}
+	if start.Name.Local == "" && finfo != nil {
+		start.Name.Space, start.Name.Local = finfo.xmlns, finfo.name
+	}
+	if start.Name.Local == "" {
+		name := typ.Name()
+		if i := strings.IndexByte(name, '['); i >= 0 {
+			// Truncate generic instantiation name. See issue 48318.
+			name = name[:i]
+		}
+		if name == "" {
+			return &UnsupportedTypeError{typ}
+		}
+		start.Name.Local = name
+	}
+
+	// Attributes
+	for i := range tinfo.fields {
+		finfo := &tinfo.fields[i]
+		if finfo.flags&fAttr == 0 {
+			continue
+		}
+		fv := finfo.value(val, dontInitNilPointers)
+
+		if finfo.flags&fOmitEmpty != 0 && (!fv.IsValid() || isEmptyValue(fv)) {
+			continue
+		}
+
+		if fv.Kind() == reflect.Interface && fv.IsNil() {
+			continue
+		}
+
+		name := Name{Space: finfo.xmlns, Local: finfo.name}
+		if err := p.marshalAttr(&start, name, fv); err != nil {
+			return err
+		}
+	}
+
+	if err := p.writeStart(&start); err != nil {
+		return err
+	}
+
+	if val.Kind() == reflect.Struct {
+		err = p.marshalStruct(tinfo, val)
+	} else {
+		s, b, err1 := p.marshalSimple(typ, val)
+		if err1 != nil {
+			err = err1
+		} else if b != nil {
+			EscapeText(p, b)
+		} else {
+			p.EscapeString(s)
+		}
+	}
+	if err != nil {
+		return err
+	}
+
+	if err := p.writeEnd(start.Name); err != nil {
+		return err
+	}
+
+	return p.cachedWriteError()
+}
+
+// marshalAttr marshals an attribute with the given name and value, adding to start.Attr.
+func (p *printer) marshalAttr(start *StartElement, name Name, val reflect.Value) error {
+	if val.CanInterface() && val.Type().Implements(marshalerAttrType) {
+		attr, err := val.Interface().(MarshalerAttr).MarshalXMLAttr(name)
+		if err != nil {
+			return err
+		}
+		if attr.Name.Local != "" {
+			start.Attr = append(start.Attr, attr)
+		}
+		return nil
+	}
+
+	if val.CanAddr() {
+		pv := val.Addr()
+		if pv.CanInterface() && pv.Type().Implements(marshalerAttrType) {
+			attr, err := pv.Interface().(MarshalerAttr).MarshalXMLAttr(name)
+			if err != nil {
+				return err
+			}
+			if attr.Name.Local != "" {
+				start.Attr = append(start.Attr, attr)
+			}
+			return nil
+		}
+	}
+
+	if val.CanInterface() && val.Type().Implements(textMarshalerType) {
+		text, err := val.Interface().(encoding.TextMarshaler).MarshalText()
+		if err != nil {
+			return err
+		}
+		start.Attr = append(start.Attr, Attr{name, string(text)})
+		return nil
+	}
+
+	if val.CanAddr() {
+		pv := val.Addr()
+		if pv.CanInterface() && pv.Type().Implements(textMarshalerType) {
+			text, err := pv.Interface().(encoding.TextMarshaler).MarshalText()
+			if err != nil {
+				return err
+			}
+			start.Attr = append(start.Attr, Attr{name, string(text)})
+			return nil
+		}
+	}
+
+	// Dereference or skip nil pointer, interface values.
+	switch val.Kind() {
+	case reflect.Pointer, reflect.Interface:
+		if val.IsNil() {
+			return nil
+		}
+		val = val.Elem()
+	}
+
+	// Walk slices.
+	if val.Kind() == reflect.Slice && val.Type().Elem().Kind() != reflect.Uint8 {
+		n := val.Len()
+		for i := 0; i < n; i++ {
+			if err := p.marshalAttr(start, name, val.Index(i)); err != nil {
+				return err
+			}
+		}
+		return nil
+	}
+
+	if val.Type() == attrType {
+		start.Attr = append(start.Attr, val.Interface().(Attr))
+		return nil
+	}
+
+	s, b, err := p.marshalSimple(val.Type(), val)
+	if err != nil {
+		return err
+	}
+	if b != nil {
+		s = string(b)
+	}
+	start.Attr = append(start.Attr, Attr{name, s})
+	return nil
+}
+
+// defaultStart returns the default start element to use,
+// given the reflect type, field info, and start template.
+func defaultStart(typ reflect.Type, finfo *fieldInfo, startTemplate *StartElement) StartElement {
+	var start StartElement
+	// Precedence for the XML element name is as above,
+	// except that we do not look inside structs for the first field.
+	if startTemplate != nil {
+		start.Name = startTemplate.Name
+		start.Attr = append(start.Attr, startTemplate.Attr...)
+	} else if finfo != nil && finfo.name != "" {
+		start.Name.Local = finfo.name
+		start.Name.Space = finfo.xmlns
+	} else if typ.Name() != "" {
+		start.Name.Local = typ.Name()
+	} else {
+		// Must be a pointer to a named type,
+		// since it has the Marshaler methods.
+		start.Name.Local = typ.Elem().Name()
+	}
+	return start
+}
+
+// marshalInterface marshals a Marshaler interface value.
+func (p *printer) marshalInterface(val Marshaler, start StartElement) error {
+	// Push a marker onto the tag stack so that MarshalXML
+	// cannot close the XML tags that it did not open.
+	p.tags = append(p.tags, Name{})
+	n := len(p.tags)
+
+	err := val.MarshalXML(p.encoder, start)
+	if err != nil {
+		return err
+	}
+
+	// Make sure MarshalXML closed all its tags. p.tags[n-1] is the mark.
+	if len(p.tags) > n {
+		return fmt.Errorf("xml: %s.MarshalXML wrote invalid XML: <%s> not closed", receiverType(val), p.tags[len(p.tags)-1].Local)
+	}
+	p.tags = p.tags[:n-1]
+	return nil
+}
+
+// marshalTextInterface marshals a TextMarshaler interface value.
+func (p *printer) marshalTextInterface(val encoding.TextMarshaler, start StartElement) error {
+	if err := p.writeStart(&start); err != nil {
+		return err
+	}
+	text, err := val.MarshalText()
+	if err != nil {
+		return err
+	}
+	EscapeText(p, text)
+	return p.writeEnd(start.Name)
+}
+
+// writeStart writes the given start element.
+func (p *printer) writeStart(start *StartElement) error {
+	if start.Name.Local == "" {
+		return fmt.Errorf("xml: start tag with no name")
+	}
+
+	p.tags = append(p.tags, start.Name)
+	p.markPrefix()
+
+	p.writeIndent(1)
+	p.WriteByte('<')
+	p.WriteString(start.Name.Local)
+
+	if start.Name.Space != "" {
+		p.WriteString(` xmlns="`)
+		p.EscapeString(start.Name.Space)
+		p.WriteByte('"')
+	}
+
+	// Attributes
+	for _, attr := range start.Attr {
+		name := attr.Name
+		if name.Local == "" {
+			continue
+		}
+		p.WriteByte(' ')
+		if name.Space != "" {
+			p.WriteString(p.createAttrPrefix(name.Space))
+			p.WriteByte(':')
+		}
+		p.WriteString(name.Local)
+		p.WriteString(`="`)
+		p.EscapeString(attr.Value)
+		p.WriteByte('"')
+	}
+	p.WriteByte('>')
+	return nil
+}
+
+func (p *printer) writeEnd(name Name) error {
+	if name.Local == "" {
+		return fmt.Errorf("xml: end tag with no name")
+	}
+	if len(p.tags) == 0 || p.tags[len(p.tags)-1].Local == "" {
+		return fmt.Errorf("xml: end tag </%s> without start tag", name.Local)
+	}
+	if top := p.tags[len(p.tags)-1]; top != name {
+		if top.Local != name.Local {
+			return fmt.Errorf("xml: end tag </%s> does not match start tag <%s>", name.Local, top.Local)
+		}
+		return fmt.Errorf("xml: end tag </%s> in namespace %s does not match start tag <%s> in namespace %s", name.Local, name.Space, top.Local, top.Space)
+	}
+	p.tags = p.tags[:len(p.tags)-1]
+
+	p.writeIndent(-1)
+	p.WriteByte('<')
+	p.WriteByte('/')
+	p.WriteString(name.Local)
+	p.WriteByte('>')
+	p.popPrefix()
+	return nil
+}
+
+func (p *printer) marshalSimple(typ reflect.Type, val reflect.Value) (string, []byte, error) {
+	switch val.Kind() {
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return strconv.FormatInt(val.Int(), 10), nil, nil
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		return strconv.FormatUint(val.Uint(), 10), nil, nil
+	case reflect.Float32, reflect.Float64:
+		return strconv.FormatFloat(val.Float(), 'g', -1, val.Type().Bits()), nil, nil
+	case reflect.String:
+		return val.String(), nil, nil
+	case reflect.Bool:
+		return strconv.FormatBool(val.Bool()), nil, nil
+	case reflect.Array:
+		if typ.Elem().Kind() != reflect.Uint8 {
+			break
+		}
+		// [...]byte
+		var bytes []byte
+		if val.CanAddr() {
+			bytes = val.Slice(0, val.Len()).Bytes()
+		} else {
+			bytes = make([]byte, val.Len())
+			reflect.Copy(reflect.ValueOf(bytes), val)
+		}
+		return "", bytes, nil
+	case reflect.Slice:
+		if typ.Elem().Kind() != reflect.Uint8 {
+			break
+		}
+		// []byte
+		return "", val.Bytes(), nil
+	}
+	return "", nil, &UnsupportedTypeError{typ}
+}
+
+var ddBytes = []byte("--")
+
+// indirect drills into interfaces and pointers, returning the pointed-at value.
+// If it encounters a nil interface or pointer, indirect returns that nil value.
+// This can turn into an infinite loop given a cyclic chain,
+// but it matches the Go 1 behavior.
+func indirect(vf reflect.Value) reflect.Value {
+	for vf.Kind() == reflect.Interface || vf.Kind() == reflect.Pointer {
+		if vf.IsNil() {
+			return vf
+		}
+		vf = vf.Elem()
+	}
+	return vf
+}
+
+func (p *printer) marshalStruct(tinfo *typeInfo, val reflect.Value) error {
+	s := parentStack{p: p}
+	for i := range tinfo.fields {
+		finfo := &tinfo.fields[i]
+		if finfo.flags&fAttr != 0 {
+			continue
+		}
+		vf := finfo.value(val, dontInitNilPointers)
+		if !vf.IsValid() {
+			// The field is behind an anonymous struct field that's
+			// nil. Skip it.
+			continue
+		}
+
+		switch finfo.flags & fMode {
+		case fCDATA, fCharData:
+			emit := EscapeText
+			if finfo.flags&fMode == fCDATA {
+				emit = emitCDATA
+			}
+			if err := s.trim(finfo.parents); err != nil {
+				return err
+			}
+			if vf.CanInterface() && vf.Type().Implements(textMarshalerType) {
+				data, err := vf.Interface().(encoding.TextMarshaler).MarshalText()
+				if err != nil {
+					return err
+				}
+				if err := emit(p, data); err != nil {
+					return err
+				}
+				continue
+			}
+			if vf.CanAddr() {
+				pv := vf.Addr()
+				if pv.CanInterface() && pv.Type().Implements(textMarshalerType) {
+					data, err := pv.Interface().(encoding.TextMarshaler).MarshalText()
+					if err != nil {
+						return err
+					}
+					if err := emit(p, data); err != nil {
+						return err
+					}
+					continue
+				}
+			}
+
+			var scratch [64]byte
+			vf = indirect(vf)
+			switch vf.Kind() {
+			case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+				if err := emit(p, strconv.AppendInt(scratch[:0], vf.Int(), 10)); err != nil {
+					return err
+				}
+			case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+				if err := emit(p, strconv.AppendUint(scratch[:0], vf.Uint(), 10)); err != nil {
+					return err
+				}
+			case reflect.Float32, reflect.Float64:
+				if err := emit(p, strconv.AppendFloat(scratch[:0], vf.Float(), 'g', -1, vf.Type().Bits())); err != nil {
+					return err
+				}
+			case reflect.Bool:
+				if err := emit(p, strconv.AppendBool(scratch[:0], vf.Bool())); err != nil {
+					return err
+				}
+			case reflect.String:
+				if err := emit(p, []byte(vf.String())); err != nil {
+					return err
+				}
+			case reflect.Slice:
+				if elem, ok := vf.Interface().([]byte); ok {
+					if err := emit(p, elem); err != nil {
+						return err
+					}
+				}
+			}
+			continue
+
+		case fComment:
+			if err := s.trim(finfo.parents); err != nil {
+				return err
+			}
+			vf = indirect(vf)
+			k := vf.Kind()
+			if !(k == reflect.String || k == reflect.Slice && vf.Type().Elem().Kind() == reflect.Uint8) {
+				return fmt.Errorf("xml: bad type for comment field of %s", val.Type())
+			}
+			if vf.Len() == 0 {
+				continue
+			}
+			p.writeIndent(0)
+			p.WriteString("<!--")
+			dashDash := false
+			dashLast := false
+			switch k {
+			case reflect.String:
+				s := vf.String()
+				dashDash = strings.Contains(s, "--")
+				dashLast = s[len(s)-1] == '-'
+				if !dashDash {
+					p.WriteString(s)
+				}
+			case reflect.Slice:
+				b := vf.Bytes()
+				dashDash = bytes.Contains(b, ddBytes)
+				dashLast = b[len(b)-1] == '-'
+				if !dashDash {
+					p.Write(b)
+				}
+			default:
+				panic("can't happen")
+			}
+			if dashDash {
+				return fmt.Errorf(`xml: comments must not contain "--"`)
+			}
+			if dashLast {
+				// "--->" is invalid grammar. Make it "- -->"
+				p.WriteByte(' ')
+			}
+			p.WriteString("-->")
+			continue
+
+		case fInnerXML:
+			vf = indirect(vf)
+			iface := vf.Interface()
+			switch raw := iface.(type) {
+			case []byte:
+				p.Write(raw)
+				continue
+			case string:
+				p.WriteString(raw)
+				continue
+			}
+
+		case fElement, fElement | fAny:
+			if err := s.trim(finfo.parents); err != nil {
+				return err
+			}
+			if len(finfo.parents) > len(s.stack) {
+				if vf.Kind() != reflect.Pointer && vf.Kind() != reflect.Interface || !vf.IsNil() {
+					if err := s.push(finfo.parents[len(s.stack):]); err != nil {
+						return err
+					}
+				}
+			}
+		}
+		if err := p.marshalValue(vf, finfo, nil); err != nil {
+			return err
+		}
+	}
+	s.trim(nil)
+	return p.cachedWriteError()
+}
+
+// return the bufio Writer's cached write error
+func (p *printer) cachedWriteError() error {
+	_, err := p.Write(nil)
+	return err
+}
+
+func (p *printer) writeIndent(depthDelta int) {
+	if len(p.prefix) == 0 && len(p.indent) == 0 {
+		return
+	}
+	if depthDelta < 0 {
+		p.depth--
+		if p.indentedIn {
+			p.indentedIn = false
+			return
+		}
+		p.indentedIn = false
+	}
+	if p.putNewline {
+		p.WriteByte('\n')
+	} else {
+		p.putNewline = true
+	}
+	if len(p.prefix) > 0 {
+		p.WriteString(p.prefix)
+	}
+	if len(p.indent) > 0 {
+		for i := 0; i < p.depth; i++ {
+			p.WriteString(p.indent)
+		}
+	}
+	if depthDelta > 0 {
+		p.depth++
+		p.indentedIn = true
+	}
+}
+
+type parentStack struct {
+	p     *printer
+	stack []string
+}
+
+// trim updates the XML context to match the longest common prefix of the stack
+// and the given parents. A closing tag will be written for every parent
+// popped. Passing a zero slice or nil will close all the elements.
+func (s *parentStack) trim(parents []string) error {
+	split := 0
+	for ; split < len(parents) && split < len(s.stack); split++ {
+		if parents[split] != s.stack[split] {
+			break
+		}
+	}
+	for i := len(s.stack) - 1; i >= split; i-- {
+		if err := s.p.writeEnd(Name{Local: s.stack[i]}); err != nil {
+			return err
+		}
+	}
+	s.stack = s.stack[:split]
+	return nil
+}
+
+// push adds parent elements to the stack and writes open tags.
+func (s *parentStack) push(parents []string) error {
+	for i := 0; i < len(parents); i++ {
+		if err := s.p.writeStart(&StartElement{Name: Name{Local: parents[i]}}); err != nil {
+			return err
+		}
+	}
+	s.stack = append(s.stack, parents...)
+	return nil
+}
+
+// UnsupportedTypeError is returned when Marshal encounters a type
+// that cannot be converted into XML.
+type UnsupportedTypeError struct {
+	Type reflect.Type
+}
+
+func (e *UnsupportedTypeError) Error() string {
+	return "xml: unsupported type: " + e.Type.String()
+}
+
+func isEmptyValue(v reflect.Value) bool {
+	switch v.Kind() {
+	case reflect.Array, reflect.Map, reflect.Slice, reflect.String:
+		return v.Len() == 0
+	case reflect.Bool:
+		return !v.Bool()
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return v.Int() == 0
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		return v.Uint() == 0
+	case reflect.Float32, reflect.Float64:
+		return v.Float() == 0
+	case reflect.Interface, reflect.Pointer:
+		return v.IsNil()
+	}
+	return false
+}
diff --git a/src/encoding/xml/marshal_test.go b/src/encoding/xml/marshal_test.go
new file mode 100644
index 0000000..3fe7e2d
--- /dev/null
+++ b/src/encoding/xml/marshal_test.go
@@ -0,0 +1,2533 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package xml
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"reflect"
+	"strconv"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+)
+
+type DriveType int
+
+const (
+	HyperDrive DriveType = iota
+	ImprobabilityDrive
+)
+
+type Passenger struct {
+	Name   []string `xml:"name"`
+	Weight float32  `xml:"weight"`
+}
+
+type Ship struct {
+	XMLName struct{} `xml:"spaceship"`
+
+	Name      string       `xml:"name,attr"`
+	Pilot     string       `xml:"pilot,attr"`
+	Drive     DriveType    `xml:"drive"`
+	Age       uint         `xml:"age"`
+	Passenger []*Passenger `xml:"passenger"`
+	secret    string
+}
+
+type NamedType string
+
+type Port struct {
+	XMLName struct{} `xml:"port"`
+	Type    string   `xml:"type,attr,omitempty"`
+	Comment string   `xml:",comment"`
+	Number  string   `xml:",chardata"`
+}
+
+type Domain struct {
+	XMLName struct{} `xml:"domain"`
+	Country string   `xml:",attr,omitempty"`
+	Name    []byte   `xml:",chardata"`
+	Comment []byte   `xml:",comment"`
+}
+
+type Book struct {
+	XMLName struct{} `xml:"book"`
+	Title   string   `xml:",chardata"`
+}
+
+type Event struct {
+	XMLName struct{} `xml:"event"`
+	Year    int      `xml:",chardata"`
+}
+
+type Movie struct {
+	XMLName struct{} `xml:"movie"`
+	Length  uint     `xml:",chardata"`
+}
+
+type Pi struct {
+	XMLName       struct{} `xml:"pi"`
+	Approximation float32  `xml:",chardata"`
+}
+
+type Universe struct {
+	XMLName struct{} `xml:"universe"`
+	Visible float64  `xml:",chardata"`
+}
+
+type Particle struct {
+	XMLName struct{} `xml:"particle"`
+	HasMass bool     `xml:",chardata"`
+}
+
+type Departure struct {
+	XMLName struct{}  `xml:"departure"`
+	When    time.Time `xml:",chardata"`
+}
+
+type SecretAgent struct {
+	XMLName   struct{} `xml:"agent"`
+	Handle    string   `xml:"handle,attr"`
+	Identity  string
+	Obfuscate string `xml:",innerxml"`
+}
+
+type NestedItems struct {
+	XMLName struct{} `xml:"result"`
+	Items   []string `xml:">item"`
+	Item1   []string `xml:"Items>item1"`
+}
+
+type NestedOrder struct {
+	XMLName struct{} `xml:"result"`
+	Field1  string   `xml:"parent>c"`
+	Field2  string   `xml:"parent>b"`
+	Field3  string   `xml:"parent>a"`
+}
+
+type MixedNested struct {
+	XMLName struct{} `xml:"result"`
+	A       string   `xml:"parent1>a"`
+	B       string   `xml:"b"`
+	C       string   `xml:"parent1>parent2>c"`
+	D       string   `xml:"parent1>d"`
+}
+
+type NilTest struct {
+	A any `xml:"parent1>parent2>a"`
+	B any `xml:"parent1>b"`
+	C any `xml:"parent1>parent2>c"`
+}
+
+type Service struct {
+	XMLName struct{} `xml:"service"`
+	Domain  *Domain  `xml:"host>domain"`
+	Port    *Port    `xml:"host>port"`
+	Extra1  any
+	Extra2  any `xml:"host>extra2"`
+}
+
+var nilStruct *Ship
+
+type EmbedA struct {
+	EmbedC
+	EmbedB EmbedB
+	FieldA string
+	embedD
+}
+
+type EmbedB struct {
+	FieldB string
+	*EmbedC
+}
+
+type EmbedC struct {
+	FieldA1 string `xml:"FieldA>A1"`
+	FieldA2 string `xml:"FieldA>A2"`
+	FieldB  string
+	FieldC  string
+}
+
+type embedD struct {
+	fieldD string
+	FieldE string // Promoted and visible when embedD is embedded.
+}
+
+type NameCasing struct {
+	XMLName struct{} `xml:"casing"`
+	Xy      string
+	XY      string
+	XyA     string `xml:"Xy,attr"`
+	XYA     string `xml:"XY,attr"`
+}
+
+type NamePrecedence struct {
+	XMLName     Name              `xml:"Parent"`
+	FromTag     XMLNameWithoutTag `xml:"InTag"`
+	FromNameVal XMLNameWithoutTag
+	FromNameTag XMLNameWithTag
+	InFieldName string
+}
+
+type XMLNameWithTag struct {
+	XMLName Name   `xml:"InXMLNameTag"`
+	Value   string `xml:",chardata"`
+}
+
+type XMLNameWithoutTag struct {
+	XMLName Name
+	Value   string `xml:",chardata"`
+}
+
+type NameInField struct {
+	Foo Name `xml:"ns foo"`
+}
+
+type AttrTest struct {
+	Int   int     `xml:",attr"`
+	Named int     `xml:"int,attr"`
+	Float float64 `xml:",attr"`
+	Uint8 uint8   `xml:",attr"`
+	Bool  bool    `xml:",attr"`
+	Str   string  `xml:",attr"`
+	Bytes []byte  `xml:",attr"`
+}
+
+type AttrsTest struct {
+	Attrs []Attr  `xml:",any,attr"`
+	Int   int     `xml:",attr"`
+	Named int     `xml:"int,attr"`
+	Float float64 `xml:",attr"`
+	Uint8 uint8   `xml:",attr"`
+	Bool  bool    `xml:",attr"`
+	Str   string  `xml:",attr"`
+	Bytes []byte  `xml:",attr"`
+}
+
+type OmitAttrTest struct {
+	Int   int     `xml:",attr,omitempty"`
+	Named int     `xml:"int,attr,omitempty"`
+	Float float64 `xml:",attr,omitempty"`
+	Uint8 uint8   `xml:",attr,omitempty"`
+	Bool  bool    `xml:",attr,omitempty"`
+	Str   string  `xml:",attr,omitempty"`
+	Bytes []byte  `xml:",attr,omitempty"`
+	PStr  *string `xml:",attr,omitempty"`
+}
+
+type OmitFieldTest struct {
+	Int   int           `xml:",omitempty"`
+	Named int           `xml:"int,omitempty"`
+	Float float64       `xml:",omitempty"`
+	Uint8 uint8         `xml:",omitempty"`
+	Bool  bool          `xml:",omitempty"`
+	Str   string        `xml:",omitempty"`
+	Bytes []byte        `xml:",omitempty"`
+	PStr  *string       `xml:",omitempty"`
+	Ptr   *PresenceTest `xml:",omitempty"`
+}
+
+type AnyTest struct {
+	XMLName  struct{}  `xml:"a"`
+	Nested   string    `xml:"nested>value"`
+	AnyField AnyHolder `xml:",any"`
+}
+
+type AnyOmitTest struct {
+	XMLName  struct{}   `xml:"a"`
+	Nested   string     `xml:"nested>value"`
+	AnyField *AnyHolder `xml:",any,omitempty"`
+}
+
+type AnySliceTest struct {
+	XMLName  struct{}    `xml:"a"`
+	Nested   string      `xml:"nested>value"`
+	AnyField []AnyHolder `xml:",any"`
+}
+
+type AnyHolder struct {
+	XMLName Name
+	XML     string `xml:",innerxml"`
+}
+
+type RecurseA struct {
+	A string
+	B *RecurseB
+}
+
+type RecurseB struct {
+	A *RecurseA
+	B string
+}
+
+type PresenceTest struct {
+	Exists *struct{}
+}
+
+type IgnoreTest struct {
+	PublicSecret string `xml:"-"`
+}
+
+type MyBytes []byte
+
+type Data struct {
+	Bytes  []byte
+	Attr   []byte `xml:",attr"`
+	Custom MyBytes
+}
+
+type Plain struct {
+	V any
+}
+
+type MyInt int
+
+type EmbedInt struct {
+	MyInt
+}
+
+type Strings struct {
+	X []string `xml:"A>B,omitempty"`
+}
+
+type PointerFieldsTest struct {
+	XMLName  Name    `xml:"dummy"`
+	Name     *string `xml:"name,attr"`
+	Age      *uint   `xml:"age,attr"`
+	Empty    *string `xml:"empty,attr"`
+	Contents *string `xml:",chardata"`
+}
+
+type ChardataEmptyTest struct {
+	XMLName  Name    `xml:"test"`
+	Contents *string `xml:",chardata"`
+}
+
+type PointerAnonFields struct {
+	*MyInt
+	*NamedType
+}
+
+type MyMarshalerTest struct {
+}
+
+var _ Marshaler = (*MyMarshalerTest)(nil)
+
+func (m *MyMarshalerTest) MarshalXML(e *Encoder, start StartElement) error {
+	e.EncodeToken(start)
+	e.EncodeToken(CharData([]byte("hello world")))
+	e.EncodeToken(EndElement{start.Name})
+	return nil
+}
+
+type MyMarshalerAttrTest struct {
+}
+
+var _ MarshalerAttr = (*MyMarshalerAttrTest)(nil)
+
+func (m *MyMarshalerAttrTest) MarshalXMLAttr(name Name) (Attr, error) {
+	return Attr{name, "hello world"}, nil
+}
+
+func (m *MyMarshalerAttrTest) UnmarshalXMLAttr(attr Attr) error {
+	return nil
+}
+
+type MarshalerStruct struct {
+	Foo MyMarshalerAttrTest `xml:",attr"`
+}
+
+type InnerStruct struct {
+	XMLName Name `xml:"testns outer"`
+}
+
+type OuterStruct struct {
+	InnerStruct
+	IntAttr int `xml:"int,attr"`
+}
+
+type OuterNamedStruct struct {
+	InnerStruct
+	XMLName Name `xml:"outerns test"`
+	IntAttr int  `xml:"int,attr"`
+}
+
+type OuterNamedOrderedStruct struct {
+	XMLName Name `xml:"outerns test"`
+	InnerStruct
+	IntAttr int `xml:"int,attr"`
+}
+
+type OuterOuterStruct struct {
+	OuterStruct
+}
+
+type NestedAndChardata struct {
+	AB       []string `xml:"A>B"`
+	Chardata string   `xml:",chardata"`
+}
+
+type NestedAndComment struct {
+	AB      []string `xml:"A>B"`
+	Comment string   `xml:",comment"`
+}
+
+type CDataTest struct {
+	Chardata string `xml:",cdata"`
+}
+
+type NestedAndCData struct {
+	AB    []string `xml:"A>B"`
+	CDATA string   `xml:",cdata"`
+}
+
+func ifaceptr(x any) any {
+	return &x
+}
+
+func stringptr(x string) *string {
+	return &x
+}
+
+type T1 struct{}
+type T2 struct{}
+
+type IndirComment struct {
+	T1      T1
+	Comment *string `xml:",comment"`
+	T2      T2
+}
+
+type DirectComment struct {
+	T1      T1
+	Comment string `xml:",comment"`
+	T2      T2
+}
+
+type IfaceComment struct {
+	T1      T1
+	Comment any `xml:",comment"`
+	T2      T2
+}
+
+type IndirChardata struct {
+	T1       T1
+	Chardata *string `xml:",chardata"`
+	T2       T2
+}
+
+type DirectChardata struct {
+	T1       T1
+	Chardata string `xml:",chardata"`
+	T2       T2
+}
+
+type IfaceChardata struct {
+	T1       T1
+	Chardata any `xml:",chardata"`
+	T2       T2
+}
+
+type IndirCDATA struct {
+	T1    T1
+	CDATA *string `xml:",cdata"`
+	T2    T2
+}
+
+type DirectCDATA struct {
+	T1    T1
+	CDATA string `xml:",cdata"`
+	T2    T2
+}
+
+type IfaceCDATA struct {
+	T1    T1
+	CDATA any `xml:",cdata"`
+	T2    T2
+}
+
+type IndirInnerXML struct {
+	T1       T1
+	InnerXML *string `xml:",innerxml"`
+	T2       T2
+}
+
+type DirectInnerXML struct {
+	T1       T1
+	InnerXML string `xml:",innerxml"`
+	T2       T2
+}
+
+type IfaceInnerXML struct {
+	T1       T1
+	InnerXML any `xml:",innerxml"`
+	T2       T2
+}
+
+type IndirElement struct {
+	T1      T1
+	Element *string
+	T2      T2
+}
+
+type DirectElement struct {
+	T1      T1
+	Element string
+	T2      T2
+}
+
+type IfaceElement struct {
+	T1      T1
+	Element any
+	T2      T2
+}
+
+type IndirOmitEmpty struct {
+	T1        T1
+	OmitEmpty *string `xml:",omitempty"`
+	T2        T2
+}
+
+type DirectOmitEmpty struct {
+	T1        T1
+	OmitEmpty string `xml:",omitempty"`
+	T2        T2
+}
+
+type IfaceOmitEmpty struct {
+	T1        T1
+	OmitEmpty any `xml:",omitempty"`
+	T2        T2
+}
+
+type IndirAny struct {
+	T1  T1
+	Any *string `xml:",any"`
+	T2  T2
+}
+
+type DirectAny struct {
+	T1  T1
+	Any string `xml:",any"`
+	T2  T2
+}
+
+type IfaceAny struct {
+	T1  T1
+	Any any `xml:",any"`
+	T2  T2
+}
+
+type Generic[T any] struct {
+	X T
+}
+
+var (
+	nameAttr     = "Sarah"
+	ageAttr      = uint(12)
+	contentsAttr = "lorem ipsum"
+	empty        = ""
+)
+
+// Unless explicitly stated as such (or *Plain), all of the
+// tests below are two-way tests. When introducing new tests,
+// please try to make them two-way as well to ensure that
+// marshaling and unmarshaling are as symmetrical as feasible.
+var marshalTests = []struct {
+	Value          any
+	ExpectXML      string
+	MarshalOnly    bool
+	MarshalError   string
+	UnmarshalOnly  bool
+	UnmarshalError string
+}{
+	// Test nil marshals to nothing
+	{Value: nil, ExpectXML: ``, MarshalOnly: true},
+	{Value: nilStruct, ExpectXML: ``, MarshalOnly: true},
+
+	// Test value types
+	{Value: &Plain{true}, ExpectXML: `<Plain><V>true</V></Plain>`},
+	{Value: &Plain{false}, ExpectXML: `<Plain><V>false</V></Plain>`},
+	{Value: &Plain{int(42)}, ExpectXML: `<Plain><V>42</V></Plain>`},
+	{Value: &Plain{int8(42)}, ExpectXML: `<Plain><V>42</V></Plain>`},
+	{Value: &Plain{int16(42)}, ExpectXML: `<Plain><V>42</V></Plain>`},
+	{Value: &Plain{int32(42)}, ExpectXML: `<Plain><V>42</V></Plain>`},
+	{Value: &Plain{uint(42)}, ExpectXML: `<Plain><V>42</V></Plain>`},
+	{Value: &Plain{uint8(42)}, ExpectXML: `<Plain><V>42</V></Plain>`},
+	{Value: &Plain{uint16(42)}, ExpectXML: `<Plain><V>42</V></Plain>`},
+	{Value: &Plain{uint32(42)}, ExpectXML: `<Plain><V>42</V></Plain>`},
+	{Value: &Plain{float32(1.25)}, ExpectXML: `<Plain><V>1.25</V></Plain>`},
+	{Value: &Plain{float64(1.25)}, ExpectXML: `<Plain><V>1.25</V></Plain>`},
+	{Value: &Plain{uintptr(0xFFDD)}, ExpectXML: `<Plain><V>65501</V></Plain>`},
+	{Value: &Plain{"gopher"}, ExpectXML: `<Plain><V>gopher</V></Plain>`},
+	{Value: &Plain{[]byte("gopher")}, ExpectXML: `<Plain><V>gopher</V></Plain>`},
+	{Value: &Plain{"</>"}, ExpectXML: `<Plain><V>&lt;/&gt;</V></Plain>`},
+	{Value: &Plain{[]byte("</>")}, ExpectXML: `<Plain><V>&lt;/&gt;</V></Plain>`},
+	{Value: &Plain{[3]byte{'<', '/', '>'}}, ExpectXML: `<Plain><V>&lt;/&gt;</V></Plain>`},
+	{Value: &Plain{NamedType("potato")}, ExpectXML: `<Plain><V>potato</V></Plain>`},
+	{Value: &Plain{[]int{1, 2, 3}}, ExpectXML: `<Plain><V>1</V><V>2</V><V>3</V></Plain>`},
+	{Value: &Plain{[3]int{1, 2, 3}}, ExpectXML: `<Plain><V>1</V><V>2</V><V>3</V></Plain>`},
+	{Value: ifaceptr(true), MarshalOnly: true, ExpectXML: `<bool>true</bool>`},
+
+	// Test time.
+	{
+		Value:     &Plain{time.Unix(1e9, 123456789).UTC()},
+		ExpectXML: `<Plain><V>2001-09-09T01:46:40.123456789Z</V></Plain>`,
+	},
+
+	// A pointer to struct{} may be used to test for an element's presence.
+	{
+		Value:     &PresenceTest{new(struct{})},
+		ExpectXML: `<PresenceTest><Exists></Exists></PresenceTest>`,
+	},
+	{
+		Value:     &PresenceTest{},
+		ExpectXML: `<PresenceTest></PresenceTest>`,
+	},
+
+	// A []byte field is only nil if the element was not found.
+	{
+		Value:         &Data{},
+		ExpectXML:     `<Data></Data>`,
+		UnmarshalOnly: true,
+	},
+	{
+		Value:         &Data{Bytes: []byte{}, Custom: MyBytes{}, Attr: []byte{}},
+		ExpectXML:     `<Data Attr=""><Bytes></Bytes><Custom></Custom></Data>`,
+		UnmarshalOnly: true,
+	},
+
+	// Check that []byte works, including named []byte types.
+	{
+		Value:     &Data{Bytes: []byte("ab"), Custom: MyBytes("cd"), Attr: []byte{'v'}},
+		ExpectXML: `<Data Attr="v"><Bytes>ab</Bytes><Custom>cd</Custom></Data>`,
+	},
+
+	// Test innerxml
+	{
+		Value: &SecretAgent{
+			Handle:    "007",
+			Identity:  "James Bond",
+			Obfuscate: "<redacted/>",
+		},
+		ExpectXML:   `<agent handle="007"><Identity>James Bond</Identity><redacted/></agent>`,
+		MarshalOnly: true,
+	},
+	{
+		Value: &SecretAgent{
+			Handle:    "007",
+			Identity:  "James Bond",
+			Obfuscate: "<Identity>James Bond</Identity><redacted/>",
+		},
+		ExpectXML:     `<agent handle="007"><Identity>James Bond</Identity><redacted/></agent>`,
+		UnmarshalOnly: true,
+	},
+
+	// Test structs
+	{Value: &Port{Type: "ssl", Number: "443"}, ExpectXML: `<port type="ssl">443</port>`},
+	{Value: &Port{Number: "443"}, ExpectXML: `<port>443</port>`},
+	{Value: &Port{Type: "<unix>"}, ExpectXML: `<port type="&lt;unix&gt;"></port>`},
+	{Value: &Port{Number: "443", Comment: "https"}, ExpectXML: `<port><!--https-->443</port>`},
+	{Value: &Port{Number: "443", Comment: "add space-"}, ExpectXML: `<port><!--add space- -->443</port>`, MarshalOnly: true},
+	{Value: &Domain{Name: []byte("google.com&friends")}, ExpectXML: `<domain>google.com&amp;friends</domain>`},
+	{Value: &Domain{Name: []byte("google.com"), Comment: []byte(" &friends ")}, ExpectXML: `<domain>google.com<!-- &friends --></domain>`},
+	{Value: &Book{Title: "Pride & Prejudice"}, ExpectXML: `<book>Pride &amp; Prejudice</book>`},
+	{Value: &Event{Year: -3114}, ExpectXML: `<event>-3114</event>`},
+	{Value: &Movie{Length: 13440}, ExpectXML: `<movie>13440</movie>`},
+	{Value: &Pi{Approximation: 3.14159265}, ExpectXML: `<pi>3.1415927</pi>`},
+	{Value: &Universe{Visible: 9.3e13}, ExpectXML: `<universe>9.3e+13</universe>`},
+	{Value: &Particle{HasMass: true}, ExpectXML: `<particle>true</particle>`},
+	{Value: &Departure{When: ParseTime("2013-01-09T00:15:00-09:00")}, ExpectXML: `<departure>2013-01-09T00:15:00-09:00</departure>`},
+	{Value: atomValue, ExpectXML: atomXML},
+	{Value: &Generic[int]{1}, ExpectXML: `<Generic><X>1</X></Generic>`},
+	{
+		Value: &Ship{
+			Name:  "Heart of Gold",
+			Pilot: "Computer",
+			Age:   1,
+			Drive: ImprobabilityDrive,
+			Passenger: []*Passenger{
+				{
+					Name:   []string{"Zaphod", "Beeblebrox"},
+					Weight: 7.25,
+				},
+				{
+					Name:   []string{"Trisha", "McMillen"},
+					Weight: 5.5,
+				},
+				{
+					Name:   []string{"Ford", "Prefect"},
+					Weight: 7,
+				},
+				{
+					Name:   []string{"Arthur", "Dent"},
+					Weight: 6.75,
+				},
+			},
+		},
+		ExpectXML: `<spaceship name="Heart of Gold" pilot="Computer">` +
+			`<drive>` + strconv.Itoa(int(ImprobabilityDrive)) + `</drive>` +
+			`<age>1</age>` +
+			`<passenger>` +
+			`<name>Zaphod</name>` +
+			`<name>Beeblebrox</name>` +
+			`<weight>7.25</weight>` +
+			`</passenger>` +
+			`<passenger>` +
+			`<name>Trisha</name>` +
+			`<name>McMillen</name>` +
+			`<weight>5.5</weight>` +
+			`</passenger>` +
+			`<passenger>` +
+			`<name>Ford</name>` +
+			`<name>Prefect</name>` +
+			`<weight>7</weight>` +
+			`</passenger>` +
+			`<passenger>` +
+			`<name>Arthur</name>` +
+			`<name>Dent</name>` +
+			`<weight>6.75</weight>` +
+			`</passenger>` +
+			`</spaceship>`,
+	},
+
+	// Test a>b
+	{
+		Value: &NestedItems{Items: nil, Item1: nil},
+		ExpectXML: `<result>` +
+			`<Items>` +
+			`</Items>` +
+			`</result>`,
+	},
+	{
+		Value: &NestedItems{Items: []string{}, Item1: []string{}},
+		ExpectXML: `<result>` +
+			`<Items>` +
+			`</Items>` +
+			`</result>`,
+		MarshalOnly: true,
+	},
+	{
+		Value: &NestedItems{Items: nil, Item1: []string{"A"}},
+		ExpectXML: `<result>` +
+			`<Items>` +
+			`<item1>A</item1>` +
+			`</Items>` +
+			`</result>`,
+	},
+	{
+		Value: &NestedItems{Items: []string{"A", "B"}, Item1: nil},
+		ExpectXML: `<result>` +
+			`<Items>` +
+			`<item>A</item>` +
+			`<item>B</item>` +
+			`</Items>` +
+			`</result>`,
+	},
+	{
+		Value: &NestedItems{Items: []string{"A", "B"}, Item1: []string{"C"}},
+		ExpectXML: `<result>` +
+			`<Items>` +
+			`<item>A</item>` +
+			`<item>B</item>` +
+			`<item1>C</item1>` +
+			`</Items>` +
+			`</result>`,
+	},
+	{
+		Value: &NestedOrder{Field1: "C", Field2: "B", Field3: "A"},
+		ExpectXML: `<result>` +
+			`<parent>` +
+			`<c>C</c>` +
+			`<b>B</b>` +
+			`<a>A</a>` +
+			`</parent>` +
+			`</result>`,
+	},
+	{
+		Value: &NilTest{A: "A", B: nil, C: "C"},
+		ExpectXML: `<NilTest>` +
+			`<parent1>` +
+			`<parent2><a>A</a></parent2>` +
+			`<parent2><c>C</c></parent2>` +
+			`</parent1>` +
+			`</NilTest>`,
+		MarshalOnly: true, // Uses interface{}
+	},
+	{
+		Value: &MixedNested{A: "A", B: "B", C: "C", D: "D"},
+		ExpectXML: `<result>` +
+			`<parent1><a>A</a></parent1>` +
+			`<b>B</b>` +
+			`<parent1>` +
+			`<parent2><c>C</c></parent2>` +
+			`<d>D</d>` +
+			`</parent1>` +
+			`</result>`,
+	},
+	{
+		Value:     &Service{Port: &Port{Number: "80"}},
+		ExpectXML: `<service><host><port>80</port></host></service>`,
+	},
+	{
+		Value:     &Service{},
+		ExpectXML: `<service></service>`,
+	},
+	{
+		Value: &Service{Port: &Port{Number: "80"}, Extra1: "A", Extra2: "B"},
+		ExpectXML: `<service>` +
+			`<host><port>80</port></host>` +
+			`<Extra1>A</Extra1>` +
+			`<host><extra2>B</extra2></host>` +
+			`</service>`,
+		MarshalOnly: true,
+	},
+	{
+		Value: &Service{Port: &Port{Number: "80"}, Extra2: "example"},
+		ExpectXML: `<service>` +
+			`<host><port>80</port></host>` +
+			`<host><extra2>example</extra2></host>` +
+			`</service>`,
+		MarshalOnly: true,
+	},
+	{
+		Value: &struct {
+			XMLName struct{} `xml:"space top"`
+			A       string   `xml:"x>a"`
+			B       string   `xml:"x>b"`
+			C       string   `xml:"space x>c"`
+			C1      string   `xml:"space1 x>c"`
+			D1      string   `xml:"space1 x>d"`
+		}{
+			A:  "a",
+			B:  "b",
+			C:  "c",
+			C1: "c1",
+			D1: "d1",
+		},
+		ExpectXML: `<top xmlns="space">` +
+			`<x><a>a</a><b>b</b><c xmlns="space">c</c>` +
+			`<c xmlns="space1">c1</c>` +
+			`<d xmlns="space1">d1</d>` +
+			`</x>` +
+			`</top>`,
+	},
+	{
+		Value: &struct {
+			XMLName Name
+			A       string `xml:"x>a"`
+			B       string `xml:"x>b"`
+			C       string `xml:"space x>c"`
+			C1      string `xml:"space1 x>c"`
+			D1      string `xml:"space1 x>d"`
+		}{
+			XMLName: Name{
+				Space: "space0",
+				Local: "top",
+			},
+			A:  "a",
+			B:  "b",
+			C:  "c",
+			C1: "c1",
+			D1: "d1",
+		},
+		ExpectXML: `<top xmlns="space0">` +
+			`<x><a>a</a><b>b</b>` +
+			`<c xmlns="space">c</c>` +
+			`<c xmlns="space1">c1</c>` +
+			`<d xmlns="space1">d1</d>` +
+			`</x>` +
+			`</top>`,
+	},
+	{
+		Value: &struct {
+			XMLName struct{} `xml:"top"`
+			B       string   `xml:"space x>b"`
+			B1      string   `xml:"space1 x>b"`
+		}{
+			B:  "b",
+			B1: "b1",
+		},
+		ExpectXML: `<top>` +
+			`<x><b xmlns="space">b</b>` +
+			`<b xmlns="space1">b1</b></x>` +
+			`</top>`,
+	},
+
+	// Test struct embedding
+	{
+		Value: &EmbedA{
+			EmbedC: EmbedC{
+				FieldA1: "", // Shadowed by A.A
+				FieldA2: "", // Shadowed by A.A
+				FieldB:  "A.C.B",
+				FieldC:  "A.C.C",
+			},
+			EmbedB: EmbedB{
+				FieldB: "A.B.B",
+				EmbedC: &EmbedC{
+					FieldA1: "A.B.C.A1",
+					FieldA2: "A.B.C.A2",
+					FieldB:  "", // Shadowed by A.B.B
+					FieldC:  "A.B.C.C",
+				},
+			},
+			FieldA: "A.A",
+			embedD: embedD{
+				FieldE: "A.D.E",
+			},
+		},
+		ExpectXML: `<EmbedA>` +
+			`<FieldB>A.C.B</FieldB>` +
+			`<FieldC>A.C.C</FieldC>` +
+			`<EmbedB>` +
+			`<FieldB>A.B.B</FieldB>` +
+			`<FieldA>` +
+			`<A1>A.B.C.A1</A1>` +
+			`<A2>A.B.C.A2</A2>` +
+			`</FieldA>` +
+			`<FieldC>A.B.C.C</FieldC>` +
+			`</EmbedB>` +
+			`<FieldA>A.A</FieldA>` +
+			`<FieldE>A.D.E</FieldE>` +
+			`</EmbedA>`,
+	},
+
+	// Anonymous struct pointer field which is nil
+	{
+		Value:     &EmbedB{},
+		ExpectXML: `<EmbedB><FieldB></FieldB></EmbedB>`,
+	},
+
+	// Other kinds of nil anonymous fields
+	{
+		Value:     &PointerAnonFields{},
+		ExpectXML: `<PointerAnonFields></PointerAnonFields>`,
+	},
+
+	// Test that name casing matters
+	{
+		Value:     &NameCasing{Xy: "mixed", XY: "upper", XyA: "mixedA", XYA: "upperA"},
+		ExpectXML: `<casing Xy="mixedA" XY="upperA"><Xy>mixed</Xy><XY>upper</XY></casing>`,
+	},
+
+	// Test the order in which the XML element name is chosen
+	{
+		Value: &NamePrecedence{
+			FromTag:     XMLNameWithoutTag{Value: "A"},
+			FromNameVal: XMLNameWithoutTag{XMLName: Name{Local: "InXMLName"}, Value: "B"},
+			FromNameTag: XMLNameWithTag{Value: "C"},
+			InFieldName: "D",
+		},
+		ExpectXML: `<Parent>` +
+			`<InTag>A</InTag>` +
+			`<InXMLName>B</InXMLName>` +
+			`<InXMLNameTag>C</InXMLNameTag>` +
+			`<InFieldName>D</InFieldName>` +
+			`</Parent>`,
+		MarshalOnly: true,
+	},
+	{
+		Value: &NamePrecedence{
+			XMLName:     Name{Local: "Parent"},
+			FromTag:     XMLNameWithoutTag{XMLName: Name{Local: "InTag"}, Value: "A"},
+			FromNameVal: XMLNameWithoutTag{XMLName: Name{Local: "FromNameVal"}, Value: "B"},
+			FromNameTag: XMLNameWithTag{XMLName: Name{Local: "InXMLNameTag"}, Value: "C"},
+			InFieldName: "D",
+		},
+		ExpectXML: `<Parent>` +
+			`<InTag>A</InTag>` +
+			`<FromNameVal>B</FromNameVal>` +
+			`<InXMLNameTag>C</InXMLNameTag>` +
+			`<InFieldName>D</InFieldName>` +
+			`</Parent>`,
+		UnmarshalOnly: true,
+	},
+
+	// xml.Name works in a plain field as well.
+	{
+		Value:     &NameInField{Name{Space: "ns", Local: "foo"}},
+		ExpectXML: `<NameInField><foo xmlns="ns"></foo></NameInField>`,
+	},
+	{
+		Value:         &NameInField{Name{Space: "ns", Local: "foo"}},
+		ExpectXML:     `<NameInField><foo xmlns="ns"><ignore></ignore></foo></NameInField>`,
+		UnmarshalOnly: true,
+	},
+
+	// Marshaling zero xml.Name uses the tag or field name.
+	{
+		Value:       &NameInField{},
+		ExpectXML:   `<NameInField><foo xmlns="ns"></foo></NameInField>`,
+		MarshalOnly: true,
+	},
+
+	// Test attributes
+	{
+		Value: &AttrTest{
+			Int:   8,
+			Named: 9,
+			Float: 23.5,
+			Uint8: 255,
+			Bool:  true,
+			Str:   "str",
+			Bytes: []byte("byt"),
+		},
+		ExpectXML: `<AttrTest Int="8" int="9" Float="23.5" Uint8="255"` +
+			` Bool="true" Str="str" Bytes="byt"></AttrTest>`,
+	},
+	{
+		Value: &AttrTest{Bytes: []byte{}},
+		ExpectXML: `<AttrTest Int="0" int="0" Float="0" Uint8="0"` +
+			` Bool="false" Str="" Bytes=""></AttrTest>`,
+	},
+	{
+		Value: &AttrsTest{
+			Attrs: []Attr{
+				{Name: Name{Local: "Answer"}, Value: "42"},
+				{Name: Name{Local: "Int"}, Value: "8"},
+				{Name: Name{Local: "int"}, Value: "9"},
+				{Name: Name{Local: "Float"}, Value: "23.5"},
+				{Name: Name{Local: "Uint8"}, Value: "255"},
+				{Name: Name{Local: "Bool"}, Value: "true"},
+				{Name: Name{Local: "Str"}, Value: "str"},
+				{Name: Name{Local: "Bytes"}, Value: "byt"},
+			},
+		},
+		ExpectXML:   `<AttrsTest Answer="42" Int="8" int="9" Float="23.5" Uint8="255" Bool="true" Str="str" Bytes="byt" Int="0" int="0" Float="0" Uint8="0" Bool="false" Str="" Bytes=""></AttrsTest>`,
+		MarshalOnly: true,
+	},
+	{
+		Value: &AttrsTest{
+			Attrs: []Attr{
+				{Name: Name{Local: "Answer"}, Value: "42"},
+			},
+			Int:   8,
+			Named: 9,
+			Float: 23.5,
+			Uint8: 255,
+			Bool:  true,
+			Str:   "str",
+			Bytes: []byte("byt"),
+		},
+		ExpectXML: `<AttrsTest Answer="42" Int="8" int="9" Float="23.5" Uint8="255" Bool="true" Str="str" Bytes="byt"></AttrsTest>`,
+	},
+	{
+		Value: &AttrsTest{
+			Attrs: []Attr{
+				{Name: Name{Local: "Int"}, Value: "0"},
+				{Name: Name{Local: "int"}, Value: "0"},
+				{Name: Name{Local: "Float"}, Value: "0"},
+				{Name: Name{Local: "Uint8"}, Value: "0"},
+				{Name: Name{Local: "Bool"}, Value: "false"},
+				{Name: Name{Local: "Str"}},
+				{Name: Name{Local: "Bytes"}},
+			},
+			Bytes: []byte{},
+		},
+		ExpectXML:   `<AttrsTest Int="0" int="0" Float="0" Uint8="0" Bool="false" Str="" Bytes="" Int="0" int="0" Float="0" Uint8="0" Bool="false" Str="" Bytes=""></AttrsTest>`,
+		MarshalOnly: true,
+	},
+	{
+		Value: &OmitAttrTest{
+			Int:   8,
+			Named: 9,
+			Float: 23.5,
+			Uint8: 255,
+			Bool:  true,
+			Str:   "str",
+			Bytes: []byte("byt"),
+			PStr:  &empty,
+		},
+		ExpectXML: `<OmitAttrTest Int="8" int="9" Float="23.5" Uint8="255"` +
+			` Bool="true" Str="str" Bytes="byt" PStr=""></OmitAttrTest>`,
+	},
+	{
+		Value:     &OmitAttrTest{},
+		ExpectXML: `<OmitAttrTest></OmitAttrTest>`,
+	},
+
+	// pointer fields
+	{
+		Value:       &PointerFieldsTest{Name: &nameAttr, Age: &ageAttr, Contents: &contentsAttr},
+		ExpectXML:   `<dummy name="Sarah" age="12">lorem ipsum</dummy>`,
+		MarshalOnly: true,
+	},
+
+	// empty chardata pointer field
+	{
+		Value:       &ChardataEmptyTest{},
+		ExpectXML:   `<test></test>`,
+		MarshalOnly: true,
+	},
+
+	// omitempty on fields
+	{
+		Value: &OmitFieldTest{
+			Int:   8,
+			Named: 9,
+			Float: 23.5,
+			Uint8: 255,
+			Bool:  true,
+			Str:   "str",
+			Bytes: []byte("byt"),
+			PStr:  &empty,
+			Ptr:   &PresenceTest{},
+		},
+		ExpectXML: `<OmitFieldTest>` +
+			`<Int>8</Int>` +
+			`<int>9</int>` +
+			`<Float>23.5</Float>` +
+			`<Uint8>255</Uint8>` +
+			`<Bool>true</Bool>` +
+			`<Str>str</Str>` +
+			`<Bytes>byt</Bytes>` +
+			`<PStr></PStr>` +
+			`<Ptr></Ptr>` +
+			`</OmitFieldTest>`,
+	},
+	{
+		Value:     &OmitFieldTest{},
+		ExpectXML: `<OmitFieldTest></OmitFieldTest>`,
+	},
+
+	// Test ",any"
+	{
+		ExpectXML: `<a><nested><value>known</value></nested><other><sub>unknown</sub></other></a>`,
+		Value: &AnyTest{
+			Nested: "known",
+			AnyField: AnyHolder{
+				XMLName: Name{Local: "other"},
+				XML:     "<sub>unknown</sub>",
+			},
+		},
+	},
+	{
+		Value: &AnyTest{Nested: "known",
+			AnyField: AnyHolder{
+				XML:     "<unknown/>",
+				XMLName: Name{Local: "AnyField"},
+			},
+		},
+		ExpectXML: `<a><nested><value>known</value></nested><AnyField><unknown/></AnyField></a>`,
+	},
+	{
+		ExpectXML: `<a><nested><value>b</value></nested></a>`,
+		Value: &AnyOmitTest{
+			Nested: "b",
+		},
+	},
+	{
+		ExpectXML: `<a><nested><value>b</value></nested><c><d>e</d></c><g xmlns="f"><h>i</h></g></a>`,
+		Value: &AnySliceTest{
+			Nested: "b",
+			AnyField: []AnyHolder{
+				{
+					XMLName: Name{Local: "c"},
+					XML:     "<d>e</d>",
+				},
+				{
+					XMLName: Name{Space: "f", Local: "g"},
+					XML:     "<h>i</h>",
+				},
+			},
+		},
+	},
+	{
+		ExpectXML: `<a><nested><value>b</value></nested></a>`,
+		Value: &AnySliceTest{
+			Nested: "b",
+		},
+	},
+
+	// Test recursive types.
+	{
+		Value: &RecurseA{
+			A: "a1",
+			B: &RecurseB{
+				A: &RecurseA{"a2", nil},
+				B: "b1",
+			},
+		},
+		ExpectXML: `<RecurseA><A>a1</A><B><A><A>a2</A></A><B>b1</B></B></RecurseA>`,
+	},
+
+	// Test ignoring fields via "-" tag
+	{
+		ExpectXML: `<IgnoreTest></IgnoreTest>`,
+		Value:     &IgnoreTest{},
+	},
+	{
+		ExpectXML:   `<IgnoreTest></IgnoreTest>`,
+		Value:       &IgnoreTest{PublicSecret: "can't tell"},
+		MarshalOnly: true,
+	},
+	{
+		ExpectXML:     `<IgnoreTest><PublicSecret>ignore me</PublicSecret></IgnoreTest>`,
+		Value:         &IgnoreTest{},
+		UnmarshalOnly: true,
+	},
+
+	// Test escaping.
+	{
+		ExpectXML: `<a><nested><value>dquote: &#34;; squote: &#39;; ampersand: &amp;; less: &lt;; greater: &gt;;</value></nested><empty></empty></a>`,
+		Value: &AnyTest{
+			Nested:   `dquote: "; squote: '; ampersand: &; less: <; greater: >;`,
+			AnyField: AnyHolder{XMLName: Name{Local: "empty"}},
+		},
+	},
+	{
+		ExpectXML: `<a><nested><value>newline: &#xA;; cr: &#xD;; tab: &#x9;;</value></nested><AnyField></AnyField></a>`,
+		Value: &AnyTest{
+			Nested:   "newline: \n; cr: \r; tab: \t;",
+			AnyField: AnyHolder{XMLName: Name{Local: "AnyField"}},
+		},
+	},
+	{
+		ExpectXML: "<a><nested><value>1\r2\r\n3\n\r4\n5</value></nested></a>",
+		Value: &AnyTest{
+			Nested: "1\n2\n3\n\n4\n5",
+		},
+		UnmarshalOnly: true,
+	},
+	{
+		ExpectXML: `<EmbedInt><MyInt>42</MyInt></EmbedInt>`,
+		Value: &EmbedInt{
+			MyInt: 42,
+		},
+	},
+	// Test outputting CDATA-wrapped text.
+	{
+		ExpectXML: `<CDataTest></CDataTest>`,
+		Value:     &CDataTest{},
+	},
+	{
+		ExpectXML: `<CDataTest><![CDATA[http://example.com/tests/1?foo=1&bar=baz]]></CDataTest>`,
+		Value: &CDataTest{
+			Chardata: "http://example.com/tests/1?foo=1&bar=baz",
+		},
+	},
+	{
+		ExpectXML: `<CDataTest><![CDATA[Literal <![CDATA[Nested]]]]><![CDATA[>!]]></CDataTest>`,
+		Value: &CDataTest{
+			Chardata: "Literal <![CDATA[Nested]]>!",
+		},
+	},
+	{
+		ExpectXML: `<CDataTest><![CDATA[<![CDATA[Nested]]]]><![CDATA[> Literal!]]></CDataTest>`,
+		Value: &CDataTest{
+			Chardata: "<![CDATA[Nested]]> Literal!",
+		},
+	},
+	{
+		ExpectXML: `<CDataTest><![CDATA[<![CDATA[Nested]]]]><![CDATA[> Literal! <![CDATA[Nested]]]]><![CDATA[> Literal!]]></CDataTest>`,
+		Value: &CDataTest{
+			Chardata: "<![CDATA[Nested]]> Literal! <![CDATA[Nested]]> Literal!",
+		},
+	},
+	{
+		ExpectXML: `<CDataTest><![CDATA[<![CDATA[<![CDATA[Nested]]]]><![CDATA[>]]]]><![CDATA[>]]></CDataTest>`,
+		Value: &CDataTest{
+			Chardata: "<![CDATA[<![CDATA[Nested]]>]]>",
+		},
+	},
+
+	// Test omitempty with parent chain; see golang.org/issue/4168.
+	{
+		ExpectXML: `<Strings><A></A></Strings>`,
+		Value:     &Strings{},
+	},
+	// Custom marshalers.
+	{
+		ExpectXML: `<MyMarshalerTest>hello world</MyMarshalerTest>`,
+		Value:     &MyMarshalerTest{},
+	},
+	{
+		ExpectXML: `<MarshalerStruct Foo="hello world"></MarshalerStruct>`,
+		Value:     &MarshalerStruct{},
+	},
+	{
+		ExpectXML: `<outer xmlns="testns" int="10"></outer>`,
+		Value:     &OuterStruct{IntAttr: 10},
+	},
+	{
+		ExpectXML: `<test xmlns="outerns" int="10"></test>`,
+		Value:     &OuterNamedStruct{XMLName: Name{Space: "outerns", Local: "test"}, IntAttr: 10},
+	},
+	{
+		ExpectXML: `<test xmlns="outerns" int="10"></test>`,
+		Value:     &OuterNamedOrderedStruct{XMLName: Name{Space: "outerns", Local: "test"}, IntAttr: 10},
+	},
+	{
+		ExpectXML: `<outer xmlns="testns" int="10"></outer>`,
+		Value:     &OuterOuterStruct{OuterStruct{IntAttr: 10}},
+	},
+	{
+		ExpectXML: `<NestedAndChardata><A><B></B><B></B></A>test</NestedAndChardata>`,
+		Value:     &NestedAndChardata{AB: make([]string, 2), Chardata: "test"},
+	},
+	{
+		ExpectXML: `<NestedAndComment><A><B></B><B></B></A><!--test--></NestedAndComment>`,
+		Value:     &NestedAndComment{AB: make([]string, 2), Comment: "test"},
+	},
+	{
+		ExpectXML: `<NestedAndCData><A><B></B><B></B></A><![CDATA[test]]></NestedAndCData>`,
+		Value:     &NestedAndCData{AB: make([]string, 2), CDATA: "test"},
+	},
+	// Test pointer indirection in various kinds of fields.
+	// https://golang.org/issue/19063
+	{
+		ExpectXML:   `<IndirComment><T1></T1><!--hi--><T2></T2></IndirComment>`,
+		Value:       &IndirComment{Comment: stringptr("hi")},
+		MarshalOnly: true,
+	},
+	{
+		ExpectXML:   `<IndirComment><T1></T1><T2></T2></IndirComment>`,
+		Value:       &IndirComment{Comment: stringptr("")},
+		MarshalOnly: true,
+	},
+	{
+		ExpectXML:    `<IndirComment><T1></T1><T2></T2></IndirComment>`,
+		Value:        &IndirComment{Comment: nil},
+		MarshalError: "xml: bad type for comment field of xml.IndirComment",
+	},
+	{
+		ExpectXML:     `<IndirComment><T1></T1><!--hi--><T2></T2></IndirComment>`,
+		Value:         &IndirComment{Comment: nil},
+		UnmarshalOnly: true,
+	},
+	{
+		ExpectXML:   `<IfaceComment><T1></T1><!--hi--><T2></T2></IfaceComment>`,
+		Value:       &IfaceComment{Comment: "hi"},
+		MarshalOnly: true,
+	},
+	{
+		ExpectXML:     `<IfaceComment><T1></T1><!--hi--><T2></T2></IfaceComment>`,
+		Value:         &IfaceComment{Comment: nil},
+		UnmarshalOnly: true,
+	},
+	{
+		ExpectXML:    `<IfaceComment><T1></T1><T2></T2></IfaceComment>`,
+		Value:        &IfaceComment{Comment: nil},
+		MarshalError: "xml: bad type for comment field of xml.IfaceComment",
+	},
+	{
+		ExpectXML:     `<IfaceComment><T1></T1><T2></T2></IfaceComment>`,
+		Value:         &IfaceComment{Comment: nil},
+		UnmarshalOnly: true,
+	},
+	{
+		ExpectXML: `<DirectComment><T1></T1><!--hi--><T2></T2></DirectComment>`,
+		Value:     &DirectComment{Comment: string("hi")},
+	},
+	{
+		ExpectXML: `<DirectComment><T1></T1><T2></T2></DirectComment>`,
+		Value:     &DirectComment{Comment: string("")},
+	},
+	{
+		ExpectXML: `<IndirChardata><T1></T1>hi<T2></T2></IndirChardata>`,
+		Value:     &IndirChardata{Chardata: stringptr("hi")},
+	},
+	{
+		ExpectXML:     `<IndirChardata><T1></T1><![CDATA[hi]]><T2></T2></IndirChardata>`,
+		Value:         &IndirChardata{Chardata: stringptr("hi")},
+		UnmarshalOnly: true, // marshals without CDATA
+	},
+	{
+		ExpectXML: `<IndirChardata><T1></T1><T2></T2></IndirChardata>`,
+		Value:     &IndirChardata{Chardata: stringptr("")},
+	},
+	{
+		ExpectXML:   `<IndirChardata><T1></T1><T2></T2></IndirChardata>`,
+		Value:       &IndirChardata{Chardata: nil},
+		MarshalOnly: true, // unmarshal leaves Chardata=stringptr("")
+	},
+	{
+		ExpectXML:      `<IfaceChardata><T1></T1>hi<T2></T2></IfaceChardata>`,
+		Value:          &IfaceChardata{Chardata: string("hi")},
+		UnmarshalError: "cannot unmarshal into interface {}",
+	},
+	{
+		ExpectXML:      `<IfaceChardata><T1></T1><![CDATA[hi]]><T2></T2></IfaceChardata>`,
+		Value:          &IfaceChardata{Chardata: string("hi")},
+		UnmarshalOnly:  true, // marshals without CDATA
+		UnmarshalError: "cannot unmarshal into interface {}",
+	},
+	{
+		ExpectXML:      `<IfaceChardata><T1></T1><T2></T2></IfaceChardata>`,
+		Value:          &IfaceChardata{Chardata: string("")},
+		UnmarshalError: "cannot unmarshal into interface {}",
+	},
+	{
+		ExpectXML:      `<IfaceChardata><T1></T1><T2></T2></IfaceChardata>`,
+		Value:          &IfaceChardata{Chardata: nil},
+		UnmarshalError: "cannot unmarshal into interface {}",
+	},
+	{
+		ExpectXML: `<DirectChardata><T1></T1>hi<T2></T2></DirectChardata>`,
+		Value:     &DirectChardata{Chardata: string("hi")},
+	},
+	{
+		ExpectXML:     `<DirectChardata><T1></T1><![CDATA[hi]]><T2></T2></DirectChardata>`,
+		Value:         &DirectChardata{Chardata: string("hi")},
+		UnmarshalOnly: true, // marshals without CDATA
+	},
+	{
+		ExpectXML: `<DirectChardata><T1></T1><T2></T2></DirectChardata>`,
+		Value:     &DirectChardata{Chardata: string("")},
+	},
+	{
+		ExpectXML: `<IndirCDATA><T1></T1><![CDATA[hi]]><T2></T2></IndirCDATA>`,
+		Value:     &IndirCDATA{CDATA: stringptr("hi")},
+	},
+	{
+		ExpectXML:     `<IndirCDATA><T1></T1>hi<T2></T2></IndirCDATA>`,
+		Value:         &IndirCDATA{CDATA: stringptr("hi")},
+		UnmarshalOnly: true, // marshals with CDATA
+	},
+	{
+		ExpectXML: `<IndirCDATA><T1></T1><T2></T2></IndirCDATA>`,
+		Value:     &IndirCDATA{CDATA: stringptr("")},
+	},
+	{
+		ExpectXML:   `<IndirCDATA><T1></T1><T2></T2></IndirCDATA>`,
+		Value:       &IndirCDATA{CDATA: nil},
+		MarshalOnly: true, // unmarshal leaves CDATA=stringptr("")
+	},
+	{
+		ExpectXML:      `<IfaceCDATA><T1></T1><![CDATA[hi]]><T2></T2></IfaceCDATA>`,
+		Value:          &IfaceCDATA{CDATA: string("hi")},
+		UnmarshalError: "cannot unmarshal into interface {}",
+	},
+	{
+		ExpectXML:      `<IfaceCDATA><T1></T1>hi<T2></T2></IfaceCDATA>`,
+		Value:          &IfaceCDATA{CDATA: string("hi")},
+		UnmarshalOnly:  true, // marshals with CDATA
+		UnmarshalError: "cannot unmarshal into interface {}",
+	},
+	{
+		ExpectXML:      `<IfaceCDATA><T1></T1><T2></T2></IfaceCDATA>`,
+		Value:          &IfaceCDATA{CDATA: string("")},
+		UnmarshalError: "cannot unmarshal into interface {}",
+	},
+	{
+		ExpectXML:      `<IfaceCDATA><T1></T1><T2></T2></IfaceCDATA>`,
+		Value:          &IfaceCDATA{CDATA: nil},
+		UnmarshalError: "cannot unmarshal into interface {}",
+	},
+	{
+		ExpectXML: `<DirectCDATA><T1></T1><![CDATA[hi]]><T2></T2></DirectCDATA>`,
+		Value:     &DirectCDATA{CDATA: string("hi")},
+	},
+	{
+		ExpectXML:     `<DirectCDATA><T1></T1>hi<T2></T2></DirectCDATA>`,
+		Value:         &DirectCDATA{CDATA: string("hi")},
+		UnmarshalOnly: true, // marshals with CDATA
+	},
+	{
+		ExpectXML: `<DirectCDATA><T1></T1><T2></T2></DirectCDATA>`,
+		Value:     &DirectCDATA{CDATA: string("")},
+	},
+	{
+		ExpectXML:   `<IndirInnerXML><T1></T1><hi/><T2></T2></IndirInnerXML>`,
+		Value:       &IndirInnerXML{InnerXML: stringptr("<hi/>")},
+		MarshalOnly: true,
+	},
+	{
+		ExpectXML:   `<IndirInnerXML><T1></T1><T2></T2></IndirInnerXML>`,
+		Value:       &IndirInnerXML{InnerXML: stringptr("")},
+		MarshalOnly: true,
+	},
+	{
+		ExpectXML: `<IndirInnerXML><T1></T1><T2></T2></IndirInnerXML>`,
+		Value:     &IndirInnerXML{InnerXML: nil},
+	},
+	{
+		ExpectXML:     `<IndirInnerXML><T1></T1><hi/><T2></T2></IndirInnerXML>`,
+		Value:         &IndirInnerXML{InnerXML: nil},
+		UnmarshalOnly: true,
+	},
+	{
+		ExpectXML:   `<IfaceInnerXML><T1></T1><hi/><T2></T2></IfaceInnerXML>`,
+		Value:       &IfaceInnerXML{InnerXML: "<hi/>"},
+		MarshalOnly: true,
+	},
+	{
+		ExpectXML:     `<IfaceInnerXML><T1></T1><hi/><T2></T2></IfaceInnerXML>`,
+		Value:         &IfaceInnerXML{InnerXML: nil},
+		UnmarshalOnly: true,
+	},
+	{
+		ExpectXML: `<IfaceInnerXML><T1></T1><T2></T2></IfaceInnerXML>`,
+		Value:     &IfaceInnerXML{InnerXML: nil},
+	},
+	{
+		ExpectXML:     `<IfaceInnerXML><T1></T1><T2></T2></IfaceInnerXML>`,
+		Value:         &IfaceInnerXML{InnerXML: nil},
+		UnmarshalOnly: true,
+	},
+	{
+		ExpectXML:   `<DirectInnerXML><T1></T1><hi/><T2></T2></DirectInnerXML>`,
+		Value:       &DirectInnerXML{InnerXML: string("<hi/>")},
+		MarshalOnly: true,
+	},
+	{
+		ExpectXML:     `<DirectInnerXML><T1></T1><hi/><T2></T2></DirectInnerXML>`,
+		Value:         &DirectInnerXML{InnerXML: string("<T1></T1><hi/><T2></T2>")},
+		UnmarshalOnly: true,
+	},
+	{
+		ExpectXML:   `<DirectInnerXML><T1></T1><T2></T2></DirectInnerXML>`,
+		Value:       &DirectInnerXML{InnerXML: string("")},
+		MarshalOnly: true,
+	},
+	{
+		ExpectXML:     `<DirectInnerXML><T1></T1><T2></T2></DirectInnerXML>`,
+		Value:         &DirectInnerXML{InnerXML: string("<T1></T1><T2></T2>")},
+		UnmarshalOnly: true,
+	},
+	{
+		ExpectXML: `<IndirElement><T1></T1><Element>hi</Element><T2></T2></IndirElement>`,
+		Value:     &IndirElement{Element: stringptr("hi")},
+	},
+	{
+		ExpectXML: `<IndirElement><T1></T1><Element></Element><T2></T2></IndirElement>`,
+		Value:     &IndirElement{Element: stringptr("")},
+	},
+	{
+		ExpectXML: `<IndirElement><T1></T1><T2></T2></IndirElement>`,
+		Value:     &IndirElement{Element: nil},
+	},
+	{
+		ExpectXML:   `<IfaceElement><T1></T1><Element>hi</Element><T2></T2></IfaceElement>`,
+		Value:       &IfaceElement{Element: "hi"},
+		MarshalOnly: true,
+	},
+	{
+		ExpectXML:     `<IfaceElement><T1></T1><Element>hi</Element><T2></T2></IfaceElement>`,
+		Value:         &IfaceElement{Element: nil},
+		UnmarshalOnly: true,
+	},
+	{
+		ExpectXML: `<IfaceElement><T1></T1><T2></T2></IfaceElement>`,
+		Value:     &IfaceElement{Element: nil},
+	},
+	{
+		ExpectXML:     `<IfaceElement><T1></T1><T2></T2></IfaceElement>`,
+		Value:         &IfaceElement{Element: nil},
+		UnmarshalOnly: true,
+	},
+	{
+		ExpectXML: `<DirectElement><T1></T1><Element>hi</Element><T2></T2></DirectElement>`,
+		Value:     &DirectElement{Element: string("hi")},
+	},
+	{
+		ExpectXML: `<DirectElement><T1></T1><Element></Element><T2></T2></DirectElement>`,
+		Value:     &DirectElement{Element: string("")},
+	},
+	{
+		ExpectXML: `<IndirOmitEmpty><T1></T1><OmitEmpty>hi</OmitEmpty><T2></T2></IndirOmitEmpty>`,
+		Value:     &IndirOmitEmpty{OmitEmpty: stringptr("hi")},
+	},
+	{
+		// Note: Changed in Go 1.8 to include <OmitEmpty> element (because x.OmitEmpty != nil).
+		ExpectXML:   `<IndirOmitEmpty><T1></T1><OmitEmpty></OmitEmpty><T2></T2></IndirOmitEmpty>`,
+		Value:       &IndirOmitEmpty{OmitEmpty: stringptr("")},
+		MarshalOnly: true,
+	},
+	{
+		ExpectXML:     `<IndirOmitEmpty><T1></T1><OmitEmpty></OmitEmpty><T2></T2></IndirOmitEmpty>`,
+		Value:         &IndirOmitEmpty{OmitEmpty: stringptr("")},
+		UnmarshalOnly: true,
+	},
+	{
+		ExpectXML: `<IndirOmitEmpty><T1></T1><T2></T2></IndirOmitEmpty>`,
+		Value:     &IndirOmitEmpty{OmitEmpty: nil},
+	},
+	{
+		ExpectXML:   `<IfaceOmitEmpty><T1></T1><OmitEmpty>hi</OmitEmpty><T2></T2></IfaceOmitEmpty>`,
+		Value:       &IfaceOmitEmpty{OmitEmpty: "hi"},
+		MarshalOnly: true,
+	},
+	{
+		ExpectXML:     `<IfaceOmitEmpty><T1></T1><OmitEmpty>hi</OmitEmpty><T2></T2></IfaceOmitEmpty>`,
+		Value:         &IfaceOmitEmpty{OmitEmpty: nil},
+		UnmarshalOnly: true,
+	},
+	{
+		ExpectXML: `<IfaceOmitEmpty><T1></T1><T2></T2></IfaceOmitEmpty>`,
+		Value:     &IfaceOmitEmpty{OmitEmpty: nil},
+	},
+	{
+		ExpectXML:     `<IfaceOmitEmpty><T1></T1><T2></T2></IfaceOmitEmpty>`,
+		Value:         &IfaceOmitEmpty{OmitEmpty: nil},
+		UnmarshalOnly: true,
+	},
+	{
+		ExpectXML: `<DirectOmitEmpty><T1></T1><OmitEmpty>hi</OmitEmpty><T2></T2></DirectOmitEmpty>`,
+		Value:     &DirectOmitEmpty{OmitEmpty: string("hi")},
+	},
+	{
+		ExpectXML: `<DirectOmitEmpty><T1></T1><T2></T2></DirectOmitEmpty>`,
+		Value:     &DirectOmitEmpty{OmitEmpty: string("")},
+	},
+	{
+		ExpectXML: `<IndirAny><T1></T1><Any>hi</Any><T2></T2></IndirAny>`,
+		Value:     &IndirAny{Any: stringptr("hi")},
+	},
+	{
+		ExpectXML: `<IndirAny><T1></T1><Any></Any><T2></T2></IndirAny>`,
+		Value:     &IndirAny{Any: stringptr("")},
+	},
+	{
+		ExpectXML: `<IndirAny><T1></T1><T2></T2></IndirAny>`,
+		Value:     &IndirAny{Any: nil},
+	},
+	{
+		ExpectXML:   `<IfaceAny><T1></T1><Any>hi</Any><T2></T2></IfaceAny>`,
+		Value:       &IfaceAny{Any: "hi"},
+		MarshalOnly: true,
+	},
+	{
+		ExpectXML:     `<IfaceAny><T1></T1><Any>hi</Any><T2></T2></IfaceAny>`,
+		Value:         &IfaceAny{Any: nil},
+		UnmarshalOnly: true,
+	},
+	{
+		ExpectXML: `<IfaceAny><T1></T1><T2></T2></IfaceAny>`,
+		Value:     &IfaceAny{Any: nil},
+	},
+	{
+		ExpectXML:     `<IfaceAny><T1></T1><T2></T2></IfaceAny>`,
+		Value:         &IfaceAny{Any: nil},
+		UnmarshalOnly: true,
+	},
+	{
+		ExpectXML: `<DirectAny><T1></T1><Any>hi</Any><T2></T2></DirectAny>`,
+		Value:     &DirectAny{Any: string("hi")},
+	},
+	{
+		ExpectXML: `<DirectAny><T1></T1><Any></Any><T2></T2></DirectAny>`,
+		Value:     &DirectAny{Any: string("")},
+	},
+	{
+		ExpectXML:     `<IndirFoo><T1></T1><Foo>hi</Foo><T2></T2></IndirFoo>`,
+		Value:         &IndirAny{Any: stringptr("hi")},
+		UnmarshalOnly: true,
+	},
+	{
+		ExpectXML:     `<IndirFoo><T1></T1><Foo></Foo><T2></T2></IndirFoo>`,
+		Value:         &IndirAny{Any: stringptr("")},
+		UnmarshalOnly: true,
+	},
+	{
+		ExpectXML:     `<IndirFoo><T1></T1><T2></T2></IndirFoo>`,
+		Value:         &IndirAny{Any: nil},
+		UnmarshalOnly: true,
+	},
+	{
+		ExpectXML:     `<IfaceFoo><T1></T1><Foo>hi</Foo><T2></T2></IfaceFoo>`,
+		Value:         &IfaceAny{Any: nil},
+		UnmarshalOnly: true,
+	},
+	{
+		ExpectXML:     `<IfaceFoo><T1></T1><T2></T2></IfaceFoo>`,
+		Value:         &IfaceAny{Any: nil},
+		UnmarshalOnly: true,
+	},
+	{
+		ExpectXML:     `<IfaceFoo><T1></T1><T2></T2></IfaceFoo>`,
+		Value:         &IfaceAny{Any: nil},
+		UnmarshalOnly: true,
+	},
+	{
+		ExpectXML:     `<DirectFoo><T1></T1><Foo>hi</Foo><T2></T2></DirectFoo>`,
+		Value:         &DirectAny{Any: string("hi")},
+		UnmarshalOnly: true,
+	},
+	{
+		ExpectXML:     `<DirectFoo><T1></T1><Foo></Foo><T2></T2></DirectFoo>`,
+		Value:         &DirectAny{Any: string("")},
+		UnmarshalOnly: true,
+	},
+}
+
+func TestMarshal(t *testing.T) {
+	for idx, test := range marshalTests {
+		if test.UnmarshalOnly {
+			continue
+		}
+
+		t.Run(fmt.Sprintf("%d", idx), func(t *testing.T) {
+			data, err := Marshal(test.Value)
+			if err != nil {
+				if test.MarshalError == "" {
+					t.Errorf("marshal(%#v): %s", test.Value, err)
+					return
+				}
+				if !strings.Contains(err.Error(), test.MarshalError) {
+					t.Errorf("marshal(%#v): %s, want %q", test.Value, err, test.MarshalError)
+				}
+				return
+			}
+			if test.MarshalError != "" {
+				t.Errorf("Marshal succeeded, want error %q", test.MarshalError)
+				return
+			}
+			if got, want := string(data), test.ExpectXML; got != want {
+				if strings.Contains(want, "\n") {
+					t.Errorf("marshal(%#v):\nHAVE:\n%s\nWANT:\n%s", test.Value, got, want)
+				} else {
+					t.Errorf("marshal(%#v):\nhave %#q\nwant %#q", test.Value, got, want)
+				}
+			}
+		})
+	}
+}
+
+type AttrParent struct {
+	X string `xml:"X>Y,attr"`
+}
+
+type BadAttr struct {
+	Name map[string]string `xml:"name,attr"`
+}
+
+var marshalErrorTests = []struct {
+	Value any
+	Err   string
+	Kind  reflect.Kind
+}{
+	{
+		Value: make(chan bool),
+		Err:   "xml: unsupported type: chan bool",
+		Kind:  reflect.Chan,
+	},
+	{
+		Value: map[string]string{
+			"question": "What do you get when you multiply six by nine?",
+			"answer":   "42",
+		},
+		Err:  "xml: unsupported type: map[string]string",
+		Kind: reflect.Map,
+	},
+	{
+		Value: map[*Ship]bool{nil: false},
+		Err:   "xml: unsupported type: map[*xml.Ship]bool",
+		Kind:  reflect.Map,
+	},
+	{
+		Value: &Domain{Comment: []byte("f--bar")},
+		Err:   `xml: comments must not contain "--"`,
+	},
+	// Reject parent chain with attr, never worked; see golang.org/issue/5033.
+	{
+		Value: &AttrParent{},
+		Err:   `xml: X>Y chain not valid with attr flag`,
+	},
+	{
+		Value: BadAttr{map[string]string{"X": "Y"}},
+		Err:   `xml: unsupported type: map[string]string`,
+	},
+}
+
+var marshalIndentTests = []struct {
+	Value     any
+	Prefix    string
+	Indent    string
+	ExpectXML string
+}{
+	{
+		Value: &SecretAgent{
+			Handle:    "007",
+			Identity:  "James Bond",
+			Obfuscate: "<redacted/>",
+		},
+		Prefix:    "",
+		Indent:    "\t",
+		ExpectXML: fmt.Sprintf("<agent handle=\"007\">\n\t<Identity>James Bond</Identity><redacted/>\n</agent>"),
+	},
+}
+
+func TestMarshalErrors(t *testing.T) {
+	for idx, test := range marshalErrorTests {
+		data, err := Marshal(test.Value)
+		if err == nil {
+			t.Errorf("#%d: marshal(%#v) = [success] %q, want error %v", idx, test.Value, data, test.Err)
+			continue
+		}
+		if err.Error() != test.Err {
+			t.Errorf("#%d: marshal(%#v) = [error] %v, want %v", idx, test.Value, err, test.Err)
+		}
+		if test.Kind != reflect.Invalid {
+			if kind := err.(*UnsupportedTypeError).Type.Kind(); kind != test.Kind {
+				t.Errorf("#%d: marshal(%#v) = [error kind] %s, want %s", idx, test.Value, kind, test.Kind)
+			}
+		}
+	}
+}
+
+// Do invertibility testing on the various structures that we test
+func TestUnmarshal(t *testing.T) {
+	for i, test := range marshalTests {
+		if test.MarshalOnly {
+			continue
+		}
+		if _, ok := test.Value.(*Plain); ok {
+			continue
+		}
+		if test.ExpectXML == `<top>`+
+			`<x><b xmlns="space">b</b>`+
+			`<b xmlns="space1">b1</b></x>`+
+			`</top>` {
+			// TODO(rogpeppe): re-enable this test in
+			// https://go-review.googlesource.com/#/c/5910/
+			continue
+		}
+
+		vt := reflect.TypeOf(test.Value)
+		dest := reflect.New(vt.Elem()).Interface()
+		err := Unmarshal([]byte(test.ExpectXML), dest)
+
+		t.Run(fmt.Sprintf("%d", i), func(t *testing.T) {
+			switch fix := dest.(type) {
+			case *Feed:
+				fix.Author.InnerXML = ""
+				for i := range fix.Entry {
+					fix.Entry[i].Author.InnerXML = ""
+				}
+			}
+
+			if err != nil {
+				if test.UnmarshalError == "" {
+					t.Errorf("unmarshal(%#v): %s", test.ExpectXML, err)
+					return
+				}
+				if !strings.Contains(err.Error(), test.UnmarshalError) {
+					t.Errorf("unmarshal(%#v): %s, want %q", test.ExpectXML, err, test.UnmarshalError)
+				}
+				return
+			}
+			if got, want := dest, test.Value; !reflect.DeepEqual(got, want) {
+				t.Errorf("unmarshal(%q):\nhave %#v\nwant %#v", test.ExpectXML, got, want)
+			}
+		})
+	}
+}
+
+func TestMarshalIndent(t *testing.T) {
+	for i, test := range marshalIndentTests {
+		data, err := MarshalIndent(test.Value, test.Prefix, test.Indent)
+		if err != nil {
+			t.Errorf("#%d: Error: %s", i, err)
+			continue
+		}
+		if got, want := string(data), test.ExpectXML; got != want {
+			t.Errorf("#%d: MarshalIndent:\nGot:%s\nWant:\n%s", i, got, want)
+		}
+	}
+}
+
+type limitedBytesWriter struct {
+	w      io.Writer
+	remain int // until writes fail
+}
+
+func (lw *limitedBytesWriter) Write(p []byte) (n int, err error) {
+	if lw.remain <= 0 {
+		println("error")
+		return 0, errors.New("write limit hit")
+	}
+	if len(p) > lw.remain {
+		p = p[:lw.remain]
+		n, _ = lw.w.Write(p)
+		lw.remain = 0
+		return n, errors.New("write limit hit")
+	}
+	n, err = lw.w.Write(p)
+	lw.remain -= n
+	return n, err
+}
+
+func TestMarshalWriteErrors(t *testing.T) {
+	var buf bytes.Buffer
+	const writeCap = 1024
+	w := &limitedBytesWriter{&buf, writeCap}
+	enc := NewEncoder(w)
+	var err error
+	var i int
+	const n = 4000
+	for i = 1; i <= n; i++ {
+		err = enc.Encode(&Passenger{
+			Name:   []string{"Alice", "Bob"},
+			Weight: 5,
+		})
+		if err != nil {
+			break
+		}
+	}
+	if err == nil {
+		t.Error("expected an error")
+	}
+	if i == n {
+		t.Errorf("expected to fail before the end")
+	}
+	if buf.Len() != writeCap {
+		t.Errorf("buf.Len() = %d; want %d", buf.Len(), writeCap)
+	}
+}
+
+func TestMarshalWriteIOErrors(t *testing.T) {
+	enc := NewEncoder(errWriter{})
+
+	expectErr := "unwritable"
+	err := enc.Encode(&Passenger{})
+	if err == nil || err.Error() != expectErr {
+		t.Errorf("EscapeTest = [error] %v, want %v", err, expectErr)
+	}
+}
+
+func TestMarshalFlush(t *testing.T) {
+	var buf bytes.Buffer
+	enc := NewEncoder(&buf)
+	if err := enc.EncodeToken(CharData("hello world")); err != nil {
+		t.Fatalf("enc.EncodeToken: %v", err)
+	}
+	if buf.Len() > 0 {
+		t.Fatalf("enc.EncodeToken caused actual write: %q", buf.Bytes())
+	}
+	if err := enc.Flush(); err != nil {
+		t.Fatalf("enc.Flush: %v", err)
+	}
+	if buf.String() != "hello world" {
+		t.Fatalf("after enc.Flush, buf.String() = %q, want %q", buf.String(), "hello world")
+	}
+}
+
+func BenchmarkMarshal(b *testing.B) {
+	b.ReportAllocs()
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			Marshal(atomValue)
+		}
+	})
+}
+
+func BenchmarkUnmarshal(b *testing.B) {
+	b.ReportAllocs()
+	xml := []byte(atomXML)
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			Unmarshal(xml, &Feed{})
+		}
+	})
+}
+
+// golang.org/issue/6556
+func TestStructPointerMarshal(t *testing.T) {
+	type A struct {
+		XMLName string `xml:"a"`
+		B       []any
+	}
+	type C struct {
+		XMLName Name
+		Value   string `xml:"value"`
+	}
+
+	a := new(A)
+	a.B = append(a.B, &C{
+		XMLName: Name{Local: "c"},
+		Value:   "x",
+	})
+
+	b, err := Marshal(a)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if x := string(b); x != "<a><c><value>x</value></c></a>" {
+		t.Fatal(x)
+	}
+	var v A
+	err = Unmarshal(b, &v)
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+var encodeTokenTests = []struct {
+	desc string
+	toks []Token
+	want string
+	err  string
+}{{
+	desc: "start element with name space",
+	toks: []Token{
+		StartElement{Name{"space", "local"}, nil},
+	},
+	want: `<local xmlns="space">`,
+}, {
+	desc: "start element with no name",
+	toks: []Token{
+		StartElement{Name{"space", ""}, nil},
+	},
+	err: "xml: start tag with no name",
+}, {
+	desc: "end element with no name",
+	toks: []Token{
+		EndElement{Name{"space", ""}},
+	},
+	err: "xml: end tag with no name",
+}, {
+	desc: "char data",
+	toks: []Token{
+		CharData("foo"),
+	},
+	want: `foo`,
+}, {
+	desc: "char data with escaped chars",
+	toks: []Token{
+		CharData(" \t\n"),
+	},
+	want: " &#x9;\n",
+}, {
+	desc: "comment",
+	toks: []Token{
+		Comment("foo"),
+	},
+	want: `<!--foo-->`,
+}, {
+	desc: "comment with invalid content",
+	toks: []Token{
+		Comment("foo-->"),
+	},
+	err: "xml: EncodeToken of Comment containing --> marker",
+}, {
+	desc: "proc instruction",
+	toks: []Token{
+		ProcInst{"Target", []byte("Instruction")},
+	},
+	want: `<?Target Instruction?>`,
+}, {
+	desc: "proc instruction with empty target",
+	toks: []Token{
+		ProcInst{"", []byte("Instruction")},
+	},
+	err: "xml: EncodeToken of ProcInst with invalid Target",
+}, {
+	desc: "proc instruction with bad content",
+	toks: []Token{
+		ProcInst{"", []byte("Instruction?>")},
+	},
+	err: "xml: EncodeToken of ProcInst with invalid Target",
+}, {
+	desc: "directive",
+	toks: []Token{
+		Directive("foo"),
+	},
+	want: `<!foo>`,
+}, {
+	desc: "more complex directive",
+	toks: []Token{
+		Directive("DOCTYPE doc [ <!ELEMENT doc '>'> <!-- com>ment --> ]"),
+	},
+	want: `<!DOCTYPE doc [ <!ELEMENT doc '>'> <!-- com>ment --> ]>`,
+}, {
+	desc: "directive instruction with bad name",
+	toks: []Token{
+		Directive("foo>"),
+	},
+	err: "xml: EncodeToken of Directive containing wrong < or > markers",
+}, {
+	desc: "end tag without start tag",
+	toks: []Token{
+		EndElement{Name{"foo", "bar"}},
+	},
+	err: "xml: end tag </bar> without start tag",
+}, {
+	desc: "mismatching end tag local name",
+	toks: []Token{
+		StartElement{Name{"", "foo"}, nil},
+		EndElement{Name{"", "bar"}},
+	},
+	err:  "xml: end tag </bar> does not match start tag <foo>",
+	want: `<foo>`,
+}, {
+	desc: "mismatching end tag namespace",
+	toks: []Token{
+		StartElement{Name{"space", "foo"}, nil},
+		EndElement{Name{"another", "foo"}},
+	},
+	err:  "xml: end tag </foo> in namespace another does not match start tag <foo> in namespace space",
+	want: `<foo xmlns="space">`,
+}, {
+	desc: "start element with explicit namespace",
+	toks: []Token{
+		StartElement{Name{"space", "local"}, []Attr{
+			{Name{"xmlns", "x"}, "space"},
+			{Name{"space", "foo"}, "value"},
+		}},
+	},
+	want: `<local xmlns="space" xmlns:_xmlns="xmlns" _xmlns:x="space" xmlns:space="space" space:foo="value">`,
+}, {
+	desc: "start element with explicit namespace and colliding prefix",
+	toks: []Token{
+		StartElement{Name{"space", "local"}, []Attr{
+			{Name{"xmlns", "x"}, "space"},
+			{Name{"space", "foo"}, "value"},
+			{Name{"x", "bar"}, "other"},
+		}},
+	},
+	want: `<local xmlns="space" xmlns:_xmlns="xmlns" _xmlns:x="space" xmlns:space="space" space:foo="value" xmlns:x="x" x:bar="other">`,
+}, {
+	desc: "start element using previously defined namespace",
+	toks: []Token{
+		StartElement{Name{"", "local"}, []Attr{
+			{Name{"xmlns", "x"}, "space"},
+		}},
+		StartElement{Name{"space", "foo"}, []Attr{
+			{Name{"space", "x"}, "y"},
+		}},
+	},
+	want: `<local xmlns:_xmlns="xmlns" _xmlns:x="space"><foo xmlns="space" xmlns:space="space" space:x="y">`,
+}, {
+	desc: "nested name space with same prefix",
+	toks: []Token{
+		StartElement{Name{"", "foo"}, []Attr{
+			{Name{"xmlns", "x"}, "space1"},
+		}},
+		StartElement{Name{"", "foo"}, []Attr{
+			{Name{"xmlns", "x"}, "space2"},
+		}},
+		StartElement{Name{"", "foo"}, []Attr{
+			{Name{"space1", "a"}, "space1 value"},
+			{Name{"space2", "b"}, "space2 value"},
+		}},
+		EndElement{Name{"", "foo"}},
+		EndElement{Name{"", "foo"}},
+		StartElement{Name{"", "foo"}, []Attr{
+			{Name{"space1", "a"}, "space1 value"},
+			{Name{"space2", "b"}, "space2 value"},
+		}},
+	},
+	want: `<foo xmlns:_xmlns="xmlns" _xmlns:x="space1"><foo _xmlns:x="space2"><foo xmlns:space1="space1" space1:a="space1 value" xmlns:space2="space2" space2:b="space2 value"></foo></foo><foo xmlns:space1="space1" space1:a="space1 value" xmlns:space2="space2" space2:b="space2 value">`,
+}, {
+	desc: "start element defining several prefixes for the same name space",
+	toks: []Token{
+		StartElement{Name{"space", "foo"}, []Attr{
+			{Name{"xmlns", "a"}, "space"},
+			{Name{"xmlns", "b"}, "space"},
+			{Name{"space", "x"}, "value"},
+		}},
+	},
+	want: `<foo xmlns="space" xmlns:_xmlns="xmlns" _xmlns:a="space" _xmlns:b="space" xmlns:space="space" space:x="value">`,
+}, {
+	desc: "nested element redefines name space",
+	toks: []Token{
+		StartElement{Name{"", "foo"}, []Attr{
+			{Name{"xmlns", "x"}, "space"},
+		}},
+		StartElement{Name{"space", "foo"}, []Attr{
+			{Name{"xmlns", "y"}, "space"},
+			{Name{"space", "a"}, "value"},
+		}},
+	},
+	want: `<foo xmlns:_xmlns="xmlns" _xmlns:x="space"><foo xmlns="space" _xmlns:y="space" xmlns:space="space" space:a="value">`,
+}, {
+	desc: "nested element creates alias for default name space",
+	toks: []Token{
+		StartElement{Name{"space", "foo"}, []Attr{
+			{Name{"", "xmlns"}, "space"},
+		}},
+		StartElement{Name{"space", "foo"}, []Attr{
+			{Name{"xmlns", "y"}, "space"},
+			{Name{"space", "a"}, "value"},
+		}},
+	},
+	want: `<foo xmlns="space" xmlns="space"><foo xmlns="space" xmlns:_xmlns="xmlns" _xmlns:y="space" xmlns:space="space" space:a="value">`,
+}, {
+	desc: "nested element defines default name space with existing prefix",
+	toks: []Token{
+		StartElement{Name{"", "foo"}, []Attr{
+			{Name{"xmlns", "x"}, "space"},
+		}},
+		StartElement{Name{"space", "foo"}, []Attr{
+			{Name{"", "xmlns"}, "space"},
+			{Name{"space", "a"}, "value"},
+		}},
+	},
+	want: `<foo xmlns:_xmlns="xmlns" _xmlns:x="space"><foo xmlns="space" xmlns="space" xmlns:space="space" space:a="value">`,
+}, {
+	desc: "nested element uses empty attribute name space when default ns defined",
+	toks: []Token{
+		StartElement{Name{"space", "foo"}, []Attr{
+			{Name{"", "xmlns"}, "space"},
+		}},
+		StartElement{Name{"space", "foo"}, []Attr{
+			{Name{"", "attr"}, "value"},
+		}},
+	},
+	want: `<foo xmlns="space" xmlns="space"><foo xmlns="space" attr="value">`,
+}, {
+	desc: "redefine xmlns",
+	toks: []Token{
+		StartElement{Name{"", "foo"}, []Attr{
+			{Name{"foo", "xmlns"}, "space"},
+		}},
+	},
+	want: `<foo xmlns:foo="foo" foo:xmlns="space">`,
+}, {
+	desc: "xmlns with explicit name space #1",
+	toks: []Token{
+		StartElement{Name{"space", "foo"}, []Attr{
+			{Name{"xml", "xmlns"}, "space"},
+		}},
+	},
+	want: `<foo xmlns="space" xmlns:_xml="xml" _xml:xmlns="space">`,
+}, {
+	desc: "xmlns with explicit name space #2",
+	toks: []Token{
+		StartElement{Name{"space", "foo"}, []Attr{
+			{Name{xmlURL, "xmlns"}, "space"},
+		}},
+	},
+	want: `<foo xmlns="space" xml:xmlns="space">`,
+}, {
+	desc: "empty name space declaration is ignored",
+	toks: []Token{
+		StartElement{Name{"", "foo"}, []Attr{
+			{Name{"xmlns", "foo"}, ""},
+		}},
+	},
+	want: `<foo xmlns:_xmlns="xmlns" _xmlns:foo="">`,
+}, {
+	desc: "attribute with no name is ignored",
+	toks: []Token{
+		StartElement{Name{"", "foo"}, []Attr{
+			{Name{"", ""}, "value"},
+		}},
+	},
+	want: `<foo>`,
+}, {
+	desc: "namespace URL with non-valid name",
+	toks: []Token{
+		StartElement{Name{"/34", "foo"}, []Attr{
+			{Name{"/34", "x"}, "value"},
+		}},
+	},
+	want: `<foo xmlns="/34" xmlns:_="/34" _:x="value">`,
+}, {
+	desc: "nested element resets default namespace to empty",
+	toks: []Token{
+		StartElement{Name{"space", "foo"}, []Attr{
+			{Name{"", "xmlns"}, "space"},
+		}},
+		StartElement{Name{"", "foo"}, []Attr{
+			{Name{"", "xmlns"}, ""},
+			{Name{"", "x"}, "value"},
+			{Name{"space", "x"}, "value"},
+		}},
+	},
+	want: `<foo xmlns="space" xmlns="space"><foo xmlns="" x="value" xmlns:space="space" space:x="value">`,
+}, {
+	desc: "nested element requires empty default name space",
+	toks: []Token{
+		StartElement{Name{"space", "foo"}, []Attr{
+			{Name{"", "xmlns"}, "space"},
+		}},
+		StartElement{Name{"", "foo"}, nil},
+	},
+	want: `<foo xmlns="space" xmlns="space"><foo>`,
+}, {
+	desc: "attribute uses name space from xmlns",
+	toks: []Token{
+		StartElement{Name{"some/space", "foo"}, []Attr{
+			{Name{"", "attr"}, "value"},
+			{Name{"some/space", "other"}, "other value"},
+		}},
+	},
+	want: `<foo xmlns="some/space" attr="value" xmlns:space="some/space" space:other="other value">`,
+}, {
+	desc: "default name space should not be used by attributes",
+	toks: []Token{
+		StartElement{Name{"space", "foo"}, []Attr{
+			{Name{"", "xmlns"}, "space"},
+			{Name{"xmlns", "bar"}, "space"},
+			{Name{"space", "baz"}, "foo"},
+		}},
+		StartElement{Name{"space", "baz"}, nil},
+		EndElement{Name{"space", "baz"}},
+		EndElement{Name{"space", "foo"}},
+	},
+	want: `<foo xmlns="space" xmlns="space" xmlns:_xmlns="xmlns" _xmlns:bar="space" xmlns:space="space" space:baz="foo"><baz xmlns="space"></baz></foo>`,
+}, {
+	desc: "default name space not used by attributes, not explicitly defined",
+	toks: []Token{
+		StartElement{Name{"space", "foo"}, []Attr{
+			{Name{"", "xmlns"}, "space"},
+			{Name{"space", "baz"}, "foo"},
+		}},
+		StartElement{Name{"space", "baz"}, nil},
+		EndElement{Name{"space", "baz"}},
+		EndElement{Name{"space", "foo"}},
+	},
+	want: `<foo xmlns="space" xmlns="space" xmlns:space="space" space:baz="foo"><baz xmlns="space"></baz></foo>`,
+}, {
+	desc: "impossible xmlns declaration",
+	toks: []Token{
+		StartElement{Name{"", "foo"}, []Attr{
+			{Name{"", "xmlns"}, "space"},
+		}},
+		StartElement{Name{"space", "bar"}, []Attr{
+			{Name{"space", "attr"}, "value"},
+		}},
+	},
+	want: `<foo xmlns="space"><bar xmlns="space" xmlns:space="space" space:attr="value">`,
+}, {
+	desc: "reserved namespace prefix -- all lower case",
+	toks: []Token{
+		StartElement{Name{"", "foo"}, []Attr{
+			{Name{"http://www.w3.org/2001/xmlSchema-instance", "nil"}, "true"},
+		}},
+	},
+	want: `<foo xmlns:_xmlSchema-instance="http://www.w3.org/2001/xmlSchema-instance" _xmlSchema-instance:nil="true">`,
+}, {
+	desc: "reserved namespace prefix -- all upper case",
+	toks: []Token{
+		StartElement{Name{"", "foo"}, []Attr{
+			{Name{"http://www.w3.org/2001/XMLSchema-instance", "nil"}, "true"},
+		}},
+	},
+	want: `<foo xmlns:_XMLSchema-instance="http://www.w3.org/2001/XMLSchema-instance" _XMLSchema-instance:nil="true">`,
+}, {
+	desc: "reserved namespace prefix -- all mixed case",
+	toks: []Token{
+		StartElement{Name{"", "foo"}, []Attr{
+			{Name{"http://www.w3.org/2001/XmLSchema-instance", "nil"}, "true"},
+		}},
+	},
+	want: `<foo xmlns:_XmLSchema-instance="http://www.w3.org/2001/XmLSchema-instance" _XmLSchema-instance:nil="true">`,
+}}
+
+func TestEncodeToken(t *testing.T) {
+loop:
+	for i, tt := range encodeTokenTests {
+		var buf bytes.Buffer
+		enc := NewEncoder(&buf)
+		var err error
+		for j, tok := range tt.toks {
+			err = enc.EncodeToken(tok)
+			if err != nil && j < len(tt.toks)-1 {
+				t.Errorf("#%d %s token #%d: %v", i, tt.desc, j, err)
+				continue loop
+			}
+		}
+		errorf := func(f string, a ...any) {
+			t.Errorf("#%d %s token #%d:%s", i, tt.desc, len(tt.toks)-1, fmt.Sprintf(f, a...))
+		}
+		switch {
+		case tt.err != "" && err == nil:
+			errorf(" expected error; got none")
+			continue
+		case tt.err == "" && err != nil:
+			errorf(" got error: %v", err)
+			continue
+		case tt.err != "" && err != nil && tt.err != err.Error():
+			errorf(" error mismatch; got %v, want %v", err, tt.err)
+			continue
+		}
+		if err := enc.Flush(); err != nil {
+			errorf(" %v", err)
+			continue
+		}
+		if got := buf.String(); got != tt.want {
+			errorf("\ngot  %v\nwant %v", got, tt.want)
+			continue
+		}
+	}
+}
+
+func TestProcInstEncodeToken(t *testing.T) {
+	var buf bytes.Buffer
+	enc := NewEncoder(&buf)
+
+	if err := enc.EncodeToken(ProcInst{"xml", []byte("Instruction")}); err != nil {
+		t.Fatalf("enc.EncodeToken: expected to be able to encode xml target ProcInst as first token, %s", err)
+	}
+
+	if err := enc.EncodeToken(ProcInst{"Target", []byte("Instruction")}); err != nil {
+		t.Fatalf("enc.EncodeToken: expected to be able to add non-xml target ProcInst")
+	}
+
+	if err := enc.EncodeToken(ProcInst{"xml", []byte("Instruction")}); err == nil {
+		t.Fatalf("enc.EncodeToken: expected to not be allowed to encode xml target ProcInst when not first token")
+	}
+}
+
+func TestDecodeEncode(t *testing.T) {
+	var in, out bytes.Buffer
+	in.WriteString(`<?xml version="1.0" encoding="UTF-8"?>
+<?Target Instruction?>
+<root>
+</root>
+`)
+	dec := NewDecoder(&in)
+	enc := NewEncoder(&out)
+	for tok, err := dec.Token(); err == nil; tok, err = dec.Token() {
+		err = enc.EncodeToken(tok)
+		if err != nil {
+			t.Fatalf("enc.EncodeToken: Unable to encode token (%#v), %v", tok, err)
+		}
+	}
+}
+
+// Issue 9796. Used to fail with GORACE="halt_on_error=1" -race.
+func TestRace9796(t *testing.T) {
+	type A struct{}
+	type B struct {
+		C []A `xml:"X>Y"`
+	}
+	var wg sync.WaitGroup
+	for i := 0; i < 2; i++ {
+		wg.Add(1)
+		go func() {
+			Marshal(B{[]A{{}}})
+			wg.Done()
+		}()
+	}
+	wg.Wait()
+}
+
+func TestIsValidDirective(t *testing.T) {
+	testOK := []string{
+		"<>",
+		"< < > >",
+		"<!DOCTYPE '<' '>' '>' <!--nothing-->>",
+		"<!DOCTYPE doc [ <!ELEMENT doc ANY> <!ELEMENT doc ANY> ]>",
+		"<!DOCTYPE doc [ <!ELEMENT doc \"ANY> '<' <!E\" LEMENT '>' doc ANY> ]>",
+		"<!DOCTYPE doc <!-- just>>>> a < comment --> [ <!ITEM anything> ] >",
+	}
+	testKO := []string{
+		"<",
+		">",
+		"<!--",
+		"-->",
+		"< > > < < >",
+		"<!dummy <!-- > -->",
+		"<!DOCTYPE doc '>",
+		"<!DOCTYPE doc '>'",
+		"<!DOCTYPE doc <!--comment>",
+	}
+	for _, s := range testOK {
+		if !isValidDirective(Directive(s)) {
+			t.Errorf("Directive %q is expected to be valid", s)
+		}
+	}
+	for _, s := range testKO {
+		if isValidDirective(Directive(s)) {
+			t.Errorf("Directive %q is expected to be invalid", s)
+		}
+	}
+}
+
+// Issue 11719. EncodeToken used to silently eat tokens with an invalid type.
+func TestSimpleUseOfEncodeToken(t *testing.T) {
+	var buf bytes.Buffer
+	enc := NewEncoder(&buf)
+	if err := enc.EncodeToken(&StartElement{Name: Name{"", "object1"}}); err == nil {
+		t.Errorf("enc.EncodeToken: pointer type should be rejected")
+	}
+	if err := enc.EncodeToken(&EndElement{Name: Name{"", "object1"}}); err == nil {
+		t.Errorf("enc.EncodeToken: pointer type should be rejected")
+	}
+	if err := enc.EncodeToken(StartElement{Name: Name{"", "object2"}}); err != nil {
+		t.Errorf("enc.EncodeToken: StartElement %s", err)
+	}
+	if err := enc.EncodeToken(EndElement{Name: Name{"", "object2"}}); err != nil {
+		t.Errorf("enc.EncodeToken: EndElement %s", err)
+	}
+	if err := enc.EncodeToken(Universe{}); err == nil {
+		t.Errorf("enc.EncodeToken: invalid type not caught")
+	}
+	if err := enc.Flush(); err != nil {
+		t.Errorf("enc.Flush: %s", err)
+	}
+	if buf.Len() == 0 {
+		t.Errorf("enc.EncodeToken: empty buffer")
+	}
+	want := "<object2></object2>"
+	if buf.String() != want {
+		t.Errorf("enc.EncodeToken: expected %q; got %q", want, buf.String())
+	}
+}
+
+// Issue 16158. Decoder.unmarshalAttr ignores the return value of copyValue.
+func TestIssue16158(t *testing.T) {
+	const data = `<foo b="HELLOWORLD"></foo>`
+	err := Unmarshal([]byte(data), &struct {
+		B byte `xml:"b,attr,omitempty"`
+	}{})
+	if err == nil {
+		t.Errorf("Unmarshal: expected error, got nil")
+	}
+}
+
+// Issue 20953. Crash on invalid XMLName attribute.
+
+type InvalidXMLName struct {
+	XMLName Name `xml:"error"`
+	Type    struct {
+		XMLName Name `xml:"type,attr"`
+	}
+}
+
+func TestInvalidXMLName(t *testing.T) {
+	var buf bytes.Buffer
+	enc := NewEncoder(&buf)
+	if err := enc.Encode(InvalidXMLName{}); err == nil {
+		t.Error("unexpected success")
+	} else if want := "invalid tag"; !strings.Contains(err.Error(), want) {
+		t.Errorf("error %q does not contain %q", err, want)
+	}
+}
+
+// Issue 50164. Crash on zero value XML attribute.
+type LayerOne struct {
+	XMLName Name `xml:"l1"`
+
+	Value     *float64 `xml:"value,omitempty"`
+	*LayerTwo `xml:",omitempty"`
+}
+
+type LayerTwo struct {
+	ValueTwo *int `xml:"value_two,attr,omitempty"`
+}
+
+func TestMarshalZeroValue(t *testing.T) {
+	proofXml := `<l1><value>1.2345</value></l1>`
+	var l1 LayerOne
+	err := Unmarshal([]byte(proofXml), &l1)
+	if err != nil {
+		t.Fatalf("unmarshal XML error: %v", err)
+	}
+	want := float64(1.2345)
+	got := *l1.Value
+	if got != want {
+		t.Fatalf("unexpected unmarshal result, want %f but got %f", want, got)
+	}
+
+	// Marshal again (or Encode again)
+	// In issue 50164, here `Marshal(l1)` will panic because of the zero value of xml attribute ValueTwo `value_two`.
+	anotherXML, err := Marshal(l1)
+	if err != nil {
+		t.Fatalf("marshal XML error: %v", err)
+	}
+	if string(anotherXML) != proofXml {
+		t.Fatalf("unexpected unmarshal result, want %q but got %q", proofXml, anotherXML)
+	}
+}
diff --git a/src/encoding/xml/read.go b/src/encoding/xml/read.go
new file mode 100644
index 0000000..cfd4407
--- /dev/null
+++ b/src/encoding/xml/read.go
@@ -0,0 +1,767 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package xml
+
+import (
+	"bytes"
+	"encoding"
+	"errors"
+	"fmt"
+	"reflect"
+	"strconv"
+	"strings"
+)
+
+// BUG(rsc): Mapping between XML elements and data structures is inherently flawed:
+// an XML element is an order-dependent collection of anonymous
+// values, while a data structure is an order-independent collection
+// of named values.
+// See package json for a textual representation more suitable
+// to data structures.
+
+// Unmarshal parses the XML-encoded data and stores the result in
+// the value pointed to by v, which must be an arbitrary struct,
+// slice, or string. Well-formed data that does not fit into v is
+// discarded.
+//
+// Because Unmarshal uses the reflect package, it can only assign
+// to exported (upper case) fields. Unmarshal uses a case-sensitive
+// comparison to match XML element names to tag values and struct
+// field names.
+//
+// Unmarshal maps an XML element to a struct using the following rules.
+// In the rules, the tag of a field refers to the value associated with the
+// key 'xml' in the struct field's tag (see the example above).
+//
+//   * If the struct has a field of type []byte or string with tag
+//      ",innerxml", Unmarshal accumulates the raw XML nested inside the
+//      element in that field. The rest of the rules still apply.
+//
+//   * If the struct has a field named XMLName of type Name,
+//      Unmarshal records the element name in that field.
+//
+//   * If the XMLName field has an associated tag of the form
+//      "name" or "namespace-URL name", the XML element must have
+//      the given name (and, optionally, name space) or else Unmarshal
+//      returns an error.
+//
+//   * If the XML element has an attribute whose name matches a
+//      struct field name with an associated tag containing ",attr" or
+//      the explicit name in a struct field tag of the form "name,attr",
+//      Unmarshal records the attribute value in that field.
+//
+//   * If the XML element has an attribute not handled by the previous
+//      rule and the struct has a field with an associated tag containing
+//      ",any,attr", Unmarshal records the attribute value in the first
+//      such field.
+//
+//   * If the XML element contains character data, that data is
+//      accumulated in the first struct field that has tag ",chardata".
+//      The struct field may have type []byte or string.
+//      If there is no such field, the character data is discarded.
+//
+//   * If the XML element contains comments, they are accumulated in
+//      the first struct field that has tag ",comment".  The struct
+//      field may have type []byte or string. If there is no such
+//      field, the comments are discarded.
+//
+//   * If the XML element contains a sub-element whose name matches
+//      the prefix of a tag formatted as "a" or "a>b>c", unmarshal
+//      will descend into the XML structure looking for elements with the
+//      given names, and will map the innermost elements to that struct
+//      field. A tag starting with ">" is equivalent to one starting
+//      with the field name followed by ">".
+//
+//   * If the XML element contains a sub-element whose name matches
+//      a struct field's XMLName tag and the struct field has no
+//      explicit name tag as per the previous rule, unmarshal maps
+//      the sub-element to that struct field.
+//
+//   * If the XML element contains a sub-element whose name matches a
+//      field without any mode flags (",attr", ",chardata", etc), Unmarshal
+//      maps the sub-element to that struct field.
+//
+//   * If the XML element contains a sub-element that hasn't matched any
+//      of the above rules and the struct has a field with tag ",any",
+//      unmarshal maps the sub-element to that struct field.
+//
+//   * An anonymous struct field is handled as if the fields of its
+//      value were part of the outer struct.
+//
+//   * A struct field with tag "-" is never unmarshaled into.
+//
+// If Unmarshal encounters a field type that implements the Unmarshaler
+// interface, Unmarshal calls its UnmarshalXML method to produce the value from
+// the XML element.  Otherwise, if the value implements
+// encoding.TextUnmarshaler, Unmarshal calls that value's UnmarshalText method.
+//
+// Unmarshal maps an XML element to a string or []byte by saving the
+// concatenation of that element's character data in the string or
+// []byte. The saved []byte is never nil.
+//
+// Unmarshal maps an attribute value to a string or []byte by saving
+// the value in the string or slice.
+//
+// Unmarshal maps an attribute value to an Attr by saving the attribute,
+// including its name, in the Attr.
+//
+// Unmarshal maps an XML element or attribute value to a slice by
+// extending the length of the slice and mapping the element or attribute
+// to the newly created value.
+//
+// Unmarshal maps an XML element or attribute value to a bool by
+// setting it to the boolean value represented by the string. Whitespace
+// is trimmed and ignored.
+//
+// Unmarshal maps an XML element or attribute value to an integer or
+// floating-point field by setting the field to the result of
+// interpreting the string value in decimal. There is no check for
+// overflow. Whitespace is trimmed and ignored.
+//
+// Unmarshal maps an XML element to a Name by recording the element
+// name.
+//
+// Unmarshal maps an XML element to a pointer by setting the pointer
+// to a freshly allocated value and then mapping the element to that value.
+//
+// A missing element or empty attribute value will be unmarshaled as a zero value.
+// If the field is a slice, a zero value will be appended to the field. Otherwise, the
+// field will be set to its zero value.
+func Unmarshal(data []byte, v any) error {
+	return NewDecoder(bytes.NewReader(data)).Decode(v)
+}
+
+// Decode works like Unmarshal, except it reads the decoder
+// stream to find the start element.
+func (d *Decoder) Decode(v any) error {
+	return d.DecodeElement(v, nil)
+}
+
+// DecodeElement works like Unmarshal except that it takes
+// a pointer to the start XML element to decode into v.
+// It is useful when a client reads some raw XML tokens itself
+// but also wants to defer to Unmarshal for some elements.
+func (d *Decoder) DecodeElement(v any, start *StartElement) error {
+	val := reflect.ValueOf(v)
+	if val.Kind() != reflect.Pointer {
+		return errors.New("non-pointer passed to Unmarshal")
+	}
+	return d.unmarshal(val.Elem(), start, 0)
+}
+
+// An UnmarshalError represents an error in the unmarshaling process.
+type UnmarshalError string
+
+func (e UnmarshalError) Error() string { return string(e) }
+
+// Unmarshaler is the interface implemented by objects that can unmarshal
+// an XML element description of themselves.
+//
+// UnmarshalXML decodes a single XML element
+// beginning with the given start element.
+// If it returns an error, the outer call to Unmarshal stops and
+// returns that error.
+// UnmarshalXML must consume exactly one XML element.
+// One common implementation strategy is to unmarshal into
+// a separate value with a layout matching the expected XML
+// using d.DecodeElement, and then to copy the data from
+// that value into the receiver.
+// Another common strategy is to use d.Token to process the
+// XML object one token at a time.
+// UnmarshalXML may not use d.RawToken.
+type Unmarshaler interface {
+	UnmarshalXML(d *Decoder, start StartElement) error
+}
+
+// UnmarshalerAttr is the interface implemented by objects that can unmarshal
+// an XML attribute description of themselves.
+//
+// UnmarshalXMLAttr decodes a single XML attribute.
+// If it returns an error, the outer call to Unmarshal stops and
+// returns that error.
+// UnmarshalXMLAttr is used only for struct fields with the
+// "attr" option in the field tag.
+type UnmarshalerAttr interface {
+	UnmarshalXMLAttr(attr Attr) error
+}
+
+// receiverType returns the receiver type to use in an expression like "%s.MethodName".
+func receiverType(val any) string {
+	t := reflect.TypeOf(val)
+	if t.Name() != "" {
+		return t.String()
+	}
+	return "(" + t.String() + ")"
+}
+
+// unmarshalInterface unmarshals a single XML element into val.
+// start is the opening tag of the element.
+func (d *Decoder) unmarshalInterface(val Unmarshaler, start *StartElement) error {
+	// Record that decoder must stop at end tag corresponding to start.
+	d.pushEOF()
+
+	d.unmarshalDepth++
+	err := val.UnmarshalXML(d, *start)
+	d.unmarshalDepth--
+	if err != nil {
+		d.popEOF()
+		return err
+	}
+
+	if !d.popEOF() {
+		return fmt.Errorf("xml: %s.UnmarshalXML did not consume entire <%s> element", receiverType(val), start.Name.Local)
+	}
+
+	return nil
+}
+
+// unmarshalTextInterface unmarshals a single XML element into val.
+// The chardata contained in the element (but not its children)
+// is passed to the text unmarshaler.
+func (d *Decoder) unmarshalTextInterface(val encoding.TextUnmarshaler) error {
+	var buf []byte
+	depth := 1
+	for depth > 0 {
+		t, err := d.Token()
+		if err != nil {
+			return err
+		}
+		switch t := t.(type) {
+		case CharData:
+			if depth == 1 {
+				buf = append(buf, t...)
+			}
+		case StartElement:
+			depth++
+		case EndElement:
+			depth--
+		}
+	}
+	return val.UnmarshalText(buf)
+}
+
+// unmarshalAttr unmarshals a single XML attribute into val.
+func (d *Decoder) unmarshalAttr(val reflect.Value, attr Attr) error {
+	if val.Kind() == reflect.Pointer {
+		if val.IsNil() {
+			val.Set(reflect.New(val.Type().Elem()))
+		}
+		val = val.Elem()
+	}
+	if val.CanInterface() && val.Type().Implements(unmarshalerAttrType) {
+		// This is an unmarshaler with a non-pointer receiver,
+		// so it's likely to be incorrect, but we do what we're told.
+		return val.Interface().(UnmarshalerAttr).UnmarshalXMLAttr(attr)
+	}
+	if val.CanAddr() {
+		pv := val.Addr()
+		if pv.CanInterface() && pv.Type().Implements(unmarshalerAttrType) {
+			return pv.Interface().(UnmarshalerAttr).UnmarshalXMLAttr(attr)
+		}
+	}
+
+	// Not an UnmarshalerAttr; try encoding.TextUnmarshaler.
+	if val.CanInterface() && val.Type().Implements(textUnmarshalerType) {
+		// This is an unmarshaler with a non-pointer receiver,
+		// so it's likely to be incorrect, but we do what we're told.
+		return val.Interface().(encoding.TextUnmarshaler).UnmarshalText([]byte(attr.Value))
+	}
+	if val.CanAddr() {
+		pv := val.Addr()
+		if pv.CanInterface() && pv.Type().Implements(textUnmarshalerType) {
+			return pv.Interface().(encoding.TextUnmarshaler).UnmarshalText([]byte(attr.Value))
+		}
+	}
+
+	if val.Type().Kind() == reflect.Slice && val.Type().Elem().Kind() != reflect.Uint8 {
+		// Slice of element values.
+		// Grow slice.
+		n := val.Len()
+		val.Set(reflect.Append(val, reflect.Zero(val.Type().Elem())))
+
+		// Recur to read element into slice.
+		if err := d.unmarshalAttr(val.Index(n), attr); err != nil {
+			val.SetLen(n)
+			return err
+		}
+		return nil
+	}
+
+	if val.Type() == attrType {
+		val.Set(reflect.ValueOf(attr))
+		return nil
+	}
+
+	return copyValue(val, []byte(attr.Value))
+}
+
+var (
+	attrType            = reflect.TypeOf(Attr{})
+	unmarshalerType     = reflect.TypeOf((*Unmarshaler)(nil)).Elem()
+	unmarshalerAttrType = reflect.TypeOf((*UnmarshalerAttr)(nil)).Elem()
+	textUnmarshalerType = reflect.TypeOf((*encoding.TextUnmarshaler)(nil)).Elem()
+)
+
+const maxUnmarshalDepth = 10000
+
+var errExeceededMaxUnmarshalDepth = errors.New("exceeded max depth")
+
+// Unmarshal a single XML element into val.
+func (d *Decoder) unmarshal(val reflect.Value, start *StartElement, depth int) error {
+	if depth >= maxUnmarshalDepth {
+		return errExeceededMaxUnmarshalDepth
+	}
+	// Find start element if we need it.
+	if start == nil {
+		for {
+			tok, err := d.Token()
+			if err != nil {
+				return err
+			}
+			if t, ok := tok.(StartElement); ok {
+				start = &t
+				break
+			}
+		}
+	}
+
+	// Load value from interface, but only if the result will be
+	// usefully addressable.
+	if val.Kind() == reflect.Interface && !val.IsNil() {
+		e := val.Elem()
+		if e.Kind() == reflect.Pointer && !e.IsNil() {
+			val = e
+		}
+	}
+
+	if val.Kind() == reflect.Pointer {
+		if val.IsNil() {
+			val.Set(reflect.New(val.Type().Elem()))
+		}
+		val = val.Elem()
+	}
+
+	if val.CanInterface() && val.Type().Implements(unmarshalerType) {
+		// This is an unmarshaler with a non-pointer receiver,
+		// so it's likely to be incorrect, but we do what we're told.
+		return d.unmarshalInterface(val.Interface().(Unmarshaler), start)
+	}
+
+	if val.CanAddr() {
+		pv := val.Addr()
+		if pv.CanInterface() && pv.Type().Implements(unmarshalerType) {
+			return d.unmarshalInterface(pv.Interface().(Unmarshaler), start)
+		}
+	}
+
+	if val.CanInterface() && val.Type().Implements(textUnmarshalerType) {
+		return d.unmarshalTextInterface(val.Interface().(encoding.TextUnmarshaler))
+	}
+
+	if val.CanAddr() {
+		pv := val.Addr()
+		if pv.CanInterface() && pv.Type().Implements(textUnmarshalerType) {
+			return d.unmarshalTextInterface(pv.Interface().(encoding.TextUnmarshaler))
+		}
+	}
+
+	var (
+		data         []byte
+		saveData     reflect.Value
+		comment      []byte
+		saveComment  reflect.Value
+		saveXML      reflect.Value
+		saveXMLIndex int
+		saveXMLData  []byte
+		saveAny      reflect.Value
+		sv           reflect.Value
+		tinfo        *typeInfo
+		err          error
+	)
+
+	switch v := val; v.Kind() {
+	default:
+		return errors.New("unknown type " + v.Type().String())
+
+	case reflect.Interface:
+		// TODO: For now, simply ignore the field. In the near
+		//       future we may choose to unmarshal the start
+		//       element on it, if not nil.
+		return d.Skip()
+
+	case reflect.Slice:
+		typ := v.Type()
+		if typ.Elem().Kind() == reflect.Uint8 {
+			// []byte
+			saveData = v
+			break
+		}
+
+		// Slice of element values.
+		// Grow slice.
+		n := v.Len()
+		v.Set(reflect.Append(val, reflect.Zero(v.Type().Elem())))
+
+		// Recur to read element into slice.
+		if err := d.unmarshal(v.Index(n), start, depth+1); err != nil {
+			v.SetLen(n)
+			return err
+		}
+		return nil
+
+	case reflect.Bool, reflect.Float32, reflect.Float64, reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64, reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr, reflect.String:
+		saveData = v
+
+	case reflect.Struct:
+		typ := v.Type()
+		if typ == nameType {
+			v.Set(reflect.ValueOf(start.Name))
+			break
+		}
+
+		sv = v
+		tinfo, err = getTypeInfo(typ)
+		if err != nil {
+			return err
+		}
+
+		// Validate and assign element name.
+		if tinfo.xmlname != nil {
+			finfo := tinfo.xmlname
+			if finfo.name != "" && finfo.name != start.Name.Local {
+				return UnmarshalError("expected element type <" + finfo.name + "> but have <" + start.Name.Local + ">")
+			}
+			if finfo.xmlns != "" && finfo.xmlns != start.Name.Space {
+				e := "expected element <" + finfo.name + "> in name space " + finfo.xmlns + " but have "
+				if start.Name.Space == "" {
+					e += "no name space"
+				} else {
+					e += start.Name.Space
+				}
+				return UnmarshalError(e)
+			}
+			fv := finfo.value(sv, initNilPointers)
+			if _, ok := fv.Interface().(Name); ok {
+				fv.Set(reflect.ValueOf(start.Name))
+			}
+		}
+
+		// Assign attributes.
+		for _, a := range start.Attr {
+			handled := false
+			any := -1
+			for i := range tinfo.fields {
+				finfo := &tinfo.fields[i]
+				switch finfo.flags & fMode {
+				case fAttr:
+					strv := finfo.value(sv, initNilPointers)
+					if a.Name.Local == finfo.name && (finfo.xmlns == "" || finfo.xmlns == a.Name.Space) {
+						if err := d.unmarshalAttr(strv, a); err != nil {
+							return err
+						}
+						handled = true
+					}
+
+				case fAny | fAttr:
+					if any == -1 {
+						any = i
+					}
+				}
+			}
+			if !handled && any >= 0 {
+				finfo := &tinfo.fields[any]
+				strv := finfo.value(sv, initNilPointers)
+				if err := d.unmarshalAttr(strv, a); err != nil {
+					return err
+				}
+			}
+		}
+
+		// Determine whether we need to save character data or comments.
+		for i := range tinfo.fields {
+			finfo := &tinfo.fields[i]
+			switch finfo.flags & fMode {
+			case fCDATA, fCharData:
+				if !saveData.IsValid() {
+					saveData = finfo.value(sv, initNilPointers)
+				}
+
+			case fComment:
+				if !saveComment.IsValid() {
+					saveComment = finfo.value(sv, initNilPointers)
+				}
+
+			case fAny, fAny | fElement:
+				if !saveAny.IsValid() {
+					saveAny = finfo.value(sv, initNilPointers)
+				}
+
+			case fInnerXML:
+				if !saveXML.IsValid() {
+					saveXML = finfo.value(sv, initNilPointers)
+					if d.saved == nil {
+						saveXMLIndex = 0
+						d.saved = new(bytes.Buffer)
+					} else {
+						saveXMLIndex = d.savedOffset()
+					}
+				}
+			}
+		}
+	}
+
+	// Find end element.
+	// Process sub-elements along the way.
+Loop:
+	for {
+		var savedOffset int
+		if saveXML.IsValid() {
+			savedOffset = d.savedOffset()
+		}
+		tok, err := d.Token()
+		if err != nil {
+			return err
+		}
+		switch t := tok.(type) {
+		case StartElement:
+			consumed := false
+			if sv.IsValid() {
+				// unmarshalPath can call unmarshal, so we need to pass the depth through so that
+				// we can continue to enforce the maximum recusion limit.
+				consumed, err = d.unmarshalPath(tinfo, sv, nil, &t, depth)
+				if err != nil {
+					return err
+				}
+				if !consumed && saveAny.IsValid() {
+					consumed = true
+					if err := d.unmarshal(saveAny, &t, depth+1); err != nil {
+						return err
+					}
+				}
+			}
+			if !consumed {
+				if err := d.Skip(); err != nil {
+					return err
+				}
+			}
+
+		case EndElement:
+			if saveXML.IsValid() {
+				saveXMLData = d.saved.Bytes()[saveXMLIndex:savedOffset]
+				if saveXMLIndex == 0 {
+					d.saved = nil
+				}
+			}
+			break Loop
+
+		case CharData:
+			if saveData.IsValid() {
+				data = append(data, t...)
+			}
+
+		case Comment:
+			if saveComment.IsValid() {
+				comment = append(comment, t...)
+			}
+		}
+	}
+
+	if saveData.IsValid() && saveData.CanInterface() && saveData.Type().Implements(textUnmarshalerType) {
+		if err := saveData.Interface().(encoding.TextUnmarshaler).UnmarshalText(data); err != nil {
+			return err
+		}
+		saveData = reflect.Value{}
+	}
+
+	if saveData.IsValid() && saveData.CanAddr() {
+		pv := saveData.Addr()
+		if pv.CanInterface() && pv.Type().Implements(textUnmarshalerType) {
+			if err := pv.Interface().(encoding.TextUnmarshaler).UnmarshalText(data); err != nil {
+				return err
+			}
+			saveData = reflect.Value{}
+		}
+	}
+
+	if err := copyValue(saveData, data); err != nil {
+		return err
+	}
+
+	switch t := saveComment; t.Kind() {
+	case reflect.String:
+		t.SetString(string(comment))
+	case reflect.Slice:
+		t.Set(reflect.ValueOf(comment))
+	}
+
+	switch t := saveXML; t.Kind() {
+	case reflect.String:
+		t.SetString(string(saveXMLData))
+	case reflect.Slice:
+		if t.Type().Elem().Kind() == reflect.Uint8 {
+			t.Set(reflect.ValueOf(saveXMLData))
+		}
+	}
+
+	return nil
+}
+
+func copyValue(dst reflect.Value, src []byte) (err error) {
+	dst0 := dst
+
+	if dst.Kind() == reflect.Pointer {
+		if dst.IsNil() {
+			dst.Set(reflect.New(dst.Type().Elem()))
+		}
+		dst = dst.Elem()
+	}
+
+	// Save accumulated data.
+	switch dst.Kind() {
+	case reflect.Invalid:
+		// Probably a comment.
+	default:
+		return errors.New("cannot unmarshal into " + dst0.Type().String())
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		if len(src) == 0 {
+			dst.SetInt(0)
+			return nil
+		}
+		itmp, err := strconv.ParseInt(strings.TrimSpace(string(src)), 10, dst.Type().Bits())
+		if err != nil {
+			return err
+		}
+		dst.SetInt(itmp)
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		if len(src) == 0 {
+			dst.SetUint(0)
+			return nil
+		}
+		utmp, err := strconv.ParseUint(strings.TrimSpace(string(src)), 10, dst.Type().Bits())
+		if err != nil {
+			return err
+		}
+		dst.SetUint(utmp)
+	case reflect.Float32, reflect.Float64:
+		if len(src) == 0 {
+			dst.SetFloat(0)
+			return nil
+		}
+		ftmp, err := strconv.ParseFloat(strings.TrimSpace(string(src)), dst.Type().Bits())
+		if err != nil {
+			return err
+		}
+		dst.SetFloat(ftmp)
+	case reflect.Bool:
+		if len(src) == 0 {
+			dst.SetBool(false)
+			return nil
+		}
+		value, err := strconv.ParseBool(strings.TrimSpace(string(src)))
+		if err != nil {
+			return err
+		}
+		dst.SetBool(value)
+	case reflect.String:
+		dst.SetString(string(src))
+	case reflect.Slice:
+		if len(src) == 0 {
+			// non-nil to flag presence
+			src = []byte{}
+		}
+		dst.SetBytes(src)
+	}
+	return nil
+}
+
+// unmarshalPath walks down an XML structure looking for wanted
+// paths, and calls unmarshal on them.
+// The consumed result tells whether XML elements have been consumed
+// from the Decoder until start's matching end element, or if it's
+// still untouched because start is uninteresting for sv's fields.
+func (d *Decoder) unmarshalPath(tinfo *typeInfo, sv reflect.Value, parents []string, start *StartElement, depth int) (consumed bool, err error) {
+	recurse := false
+Loop:
+	for i := range tinfo.fields {
+		finfo := &tinfo.fields[i]
+		if finfo.flags&fElement == 0 || len(finfo.parents) < len(parents) || finfo.xmlns != "" && finfo.xmlns != start.Name.Space {
+			continue
+		}
+		for j := range parents {
+			if parents[j] != finfo.parents[j] {
+				continue Loop
+			}
+		}
+		if len(finfo.parents) == len(parents) && finfo.name == start.Name.Local {
+			// It's a perfect match, unmarshal the field.
+			return true, d.unmarshal(finfo.value(sv, initNilPointers), start, depth+1)
+		}
+		if len(finfo.parents) > len(parents) && finfo.parents[len(parents)] == start.Name.Local {
+			// It's a prefix for the field. Break and recurse
+			// since it's not ok for one field path to be itself
+			// the prefix for another field path.
+			recurse = true
+
+			// We can reuse the same slice as long as we
+			// don't try to append to it.
+			parents = finfo.parents[:len(parents)+1]
+			break
+		}
+	}
+	if !recurse {
+		// We have no business with this element.
+		return false, nil
+	}
+	// The element is not a perfect match for any field, but one
+	// or more fields have the path to this element as a parent
+	// prefix. Recurse and attempt to match these.
+	for {
+		var tok Token
+		tok, err = d.Token()
+		if err != nil {
+			return true, err
+		}
+		switch t := tok.(type) {
+		case StartElement:
+			// the recursion depth of unmarshalPath is limited to the path length specified
+			// by the struct field tag, so we don't increment the depth here.
+			consumed2, err := d.unmarshalPath(tinfo, sv, parents, &t, depth)
+			if err != nil {
+				return true, err
+			}
+			if !consumed2 {
+				if err := d.Skip(); err != nil {
+					return true, err
+				}
+			}
+		case EndElement:
+			return true, nil
+		}
+	}
+}
+
+// Skip reads tokens until it has consumed the end element
+// matching the most recent start element already consumed,
+// skipping nested structures.
+// It returns nil if it finds an end element matching the start
+// element; otherwise it returns an error describing the problem.
+func (d *Decoder) Skip() error {
+	var depth int64
+	for {
+		tok, err := d.Token()
+		if err != nil {
+			return err
+		}
+		switch tok.(type) {
+		case StartElement:
+			depth++
+		case EndElement:
+			if depth == 0 {
+				return nil
+			}
+			depth--
+		}
+	}
+}
diff --git a/src/encoding/xml/read_test.go b/src/encoding/xml/read_test.go
new file mode 100644
index 0000000..1362f7f
--- /dev/null
+++ b/src/encoding/xml/read_test.go
@@ -0,0 +1,1112 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package xml
+
+import (
+	"bytes"
+	"errors"
+	"io"
+	"reflect"
+	"strings"
+	"testing"
+	"time"
+)
+
+// Stripped down Atom feed data structures.
+
+func TestUnmarshalFeed(t *testing.T) {
+	var f Feed
+	if err := Unmarshal([]byte(atomFeedString), &f); err != nil {
+		t.Fatalf("Unmarshal: %s", err)
+	}
+	if !reflect.DeepEqual(f, atomFeed) {
+		t.Fatalf("have %#v\nwant %#v", f, atomFeed)
+	}
+}
+
+// hget http://codereview.appspot.com/rss/mine/rsc
+const atomFeedString = `
+<?xml version="1.0" encoding="utf-8"?>
+<feed xmlns="http://www.w3.org/2005/Atom" xml:lang="en-us" updated="2009-10-04T01:35:58+00:00"><title>Code Review - My issues</title><link href="http://codereview.appspot.com/" rel="alternate"></link><link href="http://codereview.appspot.com/rss/mine/rsc" rel="self"></link><id>http://codereview.appspot.com/</id><author><name>rietveld&lt;&gt;</name></author><entry><title>rietveld: an attempt at pubsubhubbub
+</title><link href="http://codereview.appspot.com/126085" rel="alternate"></link><updated>2009-10-04T01:35:58+00:00</updated><author><name>email-address-removed</name></author><id>urn:md5:134d9179c41f806be79b3a5f7877d19a</id><summary type="html">
+  An attempt at adding pubsubhubbub support to Rietveld.
+http://code.google.com/p/pubsubhubbub
+http://code.google.com/p/rietveld/issues/detail?id=155
+
+The server side of the protocol is trivial:
+  1. add a &amp;lt;link rel=&amp;quot;hub&amp;quot; href=&amp;quot;hub-server&amp;quot;&amp;gt; tag to all
+     feeds that will be pubsubhubbubbed.
+  2. every time one of those feeds changes, tell the hub
+     with a simple POST request.
+
+I have tested this by adding debug prints to a local hub
+server and checking that the server got the right publish
+requests.
+
+I can&amp;#39;t quite get the server to work, but I think the bug
+is not in my code.  I think that the server expects to be
+able to grab the feed and see the feed&amp;#39;s actual URL in
+the link rel=&amp;quot;self&amp;quot;, but the default value for that drops
+the :port from the URL, and I cannot for the life of me
+figure out how to get the Atom generator deep inside
+django not to do that, or even where it is doing that,
+or even what code is running to generate the Atom feed.
+(I thought I knew but I added some assert False statements
+and it kept running!)
+
+Ignoring that particular problem, I would appreciate
+feedback on the right way to get the two values at
+the top of feeds.py marked NOTE(rsc).
+
+
+</summary></entry><entry><title>rietveld: correct tab handling
+</title><link href="http://codereview.appspot.com/124106" rel="alternate"></link><updated>2009-10-03T23:02:17+00:00</updated><author><name>email-address-removed</name></author><id>urn:md5:0a2a4f19bb815101f0ba2904aed7c35a</id><summary type="html">
+  This fixes the buggy tab rendering that can be seen at
+http://codereview.appspot.com/116075/diff/1/2
+
+The fundamental problem was that the tab code was
+not being told what column the text began in, so it
+didn&amp;#39;t know where to put the tab stops.  Another problem
+was that some of the code assumed that string byte
+offsets were the same as column offsets, which is only
+true if there are no tabs.
+
+In the process of fixing this, I cleaned up the arguments
+to Fold and ExpandTabs and renamed them Break and
+_ExpandTabs so that I could be sure that I found all the
+call sites.  I also wanted to verify that ExpandTabs was
+not being used from outside intra_region_diff.py.
+
+
+</summary></entry></feed> 	   `
+
+type Feed struct {
+	XMLName Name      `xml:"http://www.w3.org/2005/Atom feed"`
+	Title   string    `xml:"title"`
+	ID      string    `xml:"id"`
+	Link    []Link    `xml:"link"`
+	Updated time.Time `xml:"updated,attr"`
+	Author  Person    `xml:"author"`
+	Entry   []Entry   `xml:"entry"`
+}
+
+type Entry struct {
+	Title   string    `xml:"title"`
+	ID      string    `xml:"id"`
+	Link    []Link    `xml:"link"`
+	Updated time.Time `xml:"updated"`
+	Author  Person    `xml:"author"`
+	Summary Text      `xml:"summary"`
+}
+
+type Link struct {
+	Rel  string `xml:"rel,attr,omitempty"`
+	Href string `xml:"href,attr"`
+}
+
+type Person struct {
+	Name     string `xml:"name"`
+	URI      string `xml:"uri"`
+	Email    string `xml:"email"`
+	InnerXML string `xml:",innerxml"`
+}
+
+type Text struct {
+	Type string `xml:"type,attr,omitempty"`
+	Body string `xml:",chardata"`
+}
+
+var atomFeed = Feed{
+	XMLName: Name{"http://www.w3.org/2005/Atom", "feed"},
+	Title:   "Code Review - My issues",
+	Link: []Link{
+		{Rel: "alternate", Href: "http://codereview.appspot.com/"},
+		{Rel: "self", Href: "http://codereview.appspot.com/rss/mine/rsc"},
+	},
+	ID:      "http://codereview.appspot.com/",
+	Updated: ParseTime("2009-10-04T01:35:58+00:00"),
+	Author: Person{
+		Name:     "rietveld<>",
+		InnerXML: "<name>rietveld&lt;&gt;</name>",
+	},
+	Entry: []Entry{
+		{
+			Title: "rietveld: an attempt at pubsubhubbub\n",
+			Link: []Link{
+				{Rel: "alternate", Href: "http://codereview.appspot.com/126085"},
+			},
+			Updated: ParseTime("2009-10-04T01:35:58+00:00"),
+			Author: Person{
+				Name:     "email-address-removed",
+				InnerXML: "<name>email-address-removed</name>",
+			},
+			ID: "urn:md5:134d9179c41f806be79b3a5f7877d19a",
+			Summary: Text{
+				Type: "html",
+				Body: `
+  An attempt at adding pubsubhubbub support to Rietveld.
+http://code.google.com/p/pubsubhubbub
+http://code.google.com/p/rietveld/issues/detail?id=155
+
+The server side of the protocol is trivial:
+  1. add a &lt;link rel=&quot;hub&quot; href=&quot;hub-server&quot;&gt; tag to all
+     feeds that will be pubsubhubbubbed.
+  2. every time one of those feeds changes, tell the hub
+     with a simple POST request.
+
+I have tested this by adding debug prints to a local hub
+server and checking that the server got the right publish
+requests.
+
+I can&#39;t quite get the server to work, but I think the bug
+is not in my code.  I think that the server expects to be
+able to grab the feed and see the feed&#39;s actual URL in
+the link rel=&quot;self&quot;, but the default value for that drops
+the :port from the URL, and I cannot for the life of me
+figure out how to get the Atom generator deep inside
+django not to do that, or even where it is doing that,
+or even what code is running to generate the Atom feed.
+(I thought I knew but I added some assert False statements
+and it kept running!)
+
+Ignoring that particular problem, I would appreciate
+feedback on the right way to get the two values at
+the top of feeds.py marked NOTE(rsc).
+
+
+`,
+			},
+		},
+		{
+			Title: "rietveld: correct tab handling\n",
+			Link: []Link{
+				{Rel: "alternate", Href: "http://codereview.appspot.com/124106"},
+			},
+			Updated: ParseTime("2009-10-03T23:02:17+00:00"),
+			Author: Person{
+				Name:     "email-address-removed",
+				InnerXML: "<name>email-address-removed</name>",
+			},
+			ID: "urn:md5:0a2a4f19bb815101f0ba2904aed7c35a",
+			Summary: Text{
+				Type: "html",
+				Body: `
+  This fixes the buggy tab rendering that can be seen at
+http://codereview.appspot.com/116075/diff/1/2
+
+The fundamental problem was that the tab code was
+not being told what column the text began in, so it
+didn&#39;t know where to put the tab stops.  Another problem
+was that some of the code assumed that string byte
+offsets were the same as column offsets, which is only
+true if there are no tabs.
+
+In the process of fixing this, I cleaned up the arguments
+to Fold and ExpandTabs and renamed them Break and
+_ExpandTabs so that I could be sure that I found all the
+call sites.  I also wanted to verify that ExpandTabs was
+not being used from outside intra_region_diff.py.
+
+
+`,
+			},
+		},
+	},
+}
+
+const pathTestString = `
+<Result>
+    <Before>1</Before>
+    <Items>
+        <Item1>
+            <Value>A</Value>
+        </Item1>
+        <Item2>
+            <Value>B</Value>
+        </Item2>
+        <Item1>
+            <Value>C</Value>
+            <Value>D</Value>
+        </Item1>
+        <_>
+            <Value>E</Value>
+        </_>
+    </Items>
+    <After>2</After>
+</Result>
+`
+
+type PathTestItem struct {
+	Value string
+}
+
+type PathTestA struct {
+	Items         []PathTestItem `xml:">Item1"`
+	Before, After string
+}
+
+type PathTestB struct {
+	Other         []PathTestItem `xml:"Items>Item1"`
+	Before, After string
+}
+
+type PathTestC struct {
+	Values1       []string `xml:"Items>Item1>Value"`
+	Values2       []string `xml:"Items>Item2>Value"`
+	Before, After string
+}
+
+type PathTestSet struct {
+	Item1 []PathTestItem
+}
+
+type PathTestD struct {
+	Other         PathTestSet `xml:"Items"`
+	Before, After string
+}
+
+type PathTestE struct {
+	Underline     string `xml:"Items>_>Value"`
+	Before, After string
+}
+
+var pathTests = []any{
+	&PathTestA{Items: []PathTestItem{{"A"}, {"D"}}, Before: "1", After: "2"},
+	&PathTestB{Other: []PathTestItem{{"A"}, {"D"}}, Before: "1", After: "2"},
+	&PathTestC{Values1: []string{"A", "C", "D"}, Values2: []string{"B"}, Before: "1", After: "2"},
+	&PathTestD{Other: PathTestSet{Item1: []PathTestItem{{"A"}, {"D"}}}, Before: "1", After: "2"},
+	&PathTestE{Underline: "E", Before: "1", After: "2"},
+}
+
+func TestUnmarshalPaths(t *testing.T) {
+	for _, pt := range pathTests {
+		v := reflect.New(reflect.TypeOf(pt).Elem()).Interface()
+		if err := Unmarshal([]byte(pathTestString), v); err != nil {
+			t.Fatalf("Unmarshal: %s", err)
+		}
+		if !reflect.DeepEqual(v, pt) {
+			t.Fatalf("have %#v\nwant %#v", v, pt)
+		}
+	}
+}
+
+type BadPathTestA struct {
+	First  string `xml:"items>item1"`
+	Other  string `xml:"items>item2"`
+	Second string `xml:"items"`
+}
+
+type BadPathTestB struct {
+	Other  string `xml:"items>item2>value"`
+	First  string `xml:"items>item1"`
+	Second string `xml:"items>item1>value"`
+}
+
+type BadPathTestC struct {
+	First  string
+	Second string `xml:"First"`
+}
+
+type BadPathTestD struct {
+	BadPathEmbeddedA
+	BadPathEmbeddedB
+}
+
+type BadPathEmbeddedA struct {
+	First string
+}
+
+type BadPathEmbeddedB struct {
+	Second string `xml:"First"`
+}
+
+var badPathTests = []struct {
+	v, e any
+}{
+	{&BadPathTestA{}, &TagPathError{reflect.TypeOf(BadPathTestA{}), "First", "items>item1", "Second", "items"}},
+	{&BadPathTestB{}, &TagPathError{reflect.TypeOf(BadPathTestB{}), "First", "items>item1", "Second", "items>item1>value"}},
+	{&BadPathTestC{}, &TagPathError{reflect.TypeOf(BadPathTestC{}), "First", "", "Second", "First"}},
+	{&BadPathTestD{}, &TagPathError{reflect.TypeOf(BadPathTestD{}), "First", "", "Second", "First"}},
+}
+
+func TestUnmarshalBadPaths(t *testing.T) {
+	for _, tt := range badPathTests {
+		err := Unmarshal([]byte(pathTestString), tt.v)
+		if !reflect.DeepEqual(err, tt.e) {
+			t.Fatalf("Unmarshal with %#v didn't fail properly:\nhave %#v,\nwant %#v", tt.v, err, tt.e)
+		}
+	}
+}
+
+const OK = "OK"
+const withoutNameTypeData = `
+<?xml version="1.0" charset="utf-8"?>
+<Test3 Attr="OK" />`
+
+type TestThree struct {
+	XMLName Name   `xml:"Test3"`
+	Attr    string `xml:",attr"`
+}
+
+func TestUnmarshalWithoutNameType(t *testing.T) {
+	var x TestThree
+	if err := Unmarshal([]byte(withoutNameTypeData), &x); err != nil {
+		t.Fatalf("Unmarshal: %s", err)
+	}
+	if x.Attr != OK {
+		t.Fatalf("have %v\nwant %v", x.Attr, OK)
+	}
+}
+
+func TestUnmarshalAttr(t *testing.T) {
+	type ParamVal struct {
+		Int int `xml:"int,attr"`
+	}
+
+	type ParamPtr struct {
+		Int *int `xml:"int,attr"`
+	}
+
+	type ParamStringPtr struct {
+		Int *string `xml:"int,attr"`
+	}
+
+	x := []byte(`<Param int="1" />`)
+
+	p1 := &ParamPtr{}
+	if err := Unmarshal(x, p1); err != nil {
+		t.Fatalf("Unmarshal: %s", err)
+	}
+	if p1.Int == nil {
+		t.Fatalf("Unmarshal failed in to *int field")
+	} else if *p1.Int != 1 {
+		t.Fatalf("Unmarshal with %s failed:\nhave %#v,\n want %#v", x, p1.Int, 1)
+	}
+
+	p2 := &ParamVal{}
+	if err := Unmarshal(x, p2); err != nil {
+		t.Fatalf("Unmarshal: %s", err)
+	}
+	if p2.Int != 1 {
+		t.Fatalf("Unmarshal with %s failed:\nhave %#v,\n want %#v", x, p2.Int, 1)
+	}
+
+	p3 := &ParamStringPtr{}
+	if err := Unmarshal(x, p3); err != nil {
+		t.Fatalf("Unmarshal: %s", err)
+	}
+	if p3.Int == nil {
+		t.Fatalf("Unmarshal failed in to *string field")
+	} else if *p3.Int != "1" {
+		t.Fatalf("Unmarshal with %s failed:\nhave %#v,\n want %#v", x, p3.Int, 1)
+	}
+}
+
+type Tables struct {
+	HTable string `xml:"http://www.w3.org/TR/html4/ table"`
+	FTable string `xml:"http://www.w3schools.com/furniture table"`
+}
+
+var tables = []struct {
+	xml string
+	tab Tables
+	ns  string
+}{
+	{
+		xml: `<Tables>` +
+			`<table xmlns="http://www.w3.org/TR/html4/">hello</table>` +
+			`<table xmlns="http://www.w3schools.com/furniture">world</table>` +
+			`</Tables>`,
+		tab: Tables{"hello", "world"},
+	},
+	{
+		xml: `<Tables>` +
+			`<table xmlns="http://www.w3schools.com/furniture">world</table>` +
+			`<table xmlns="http://www.w3.org/TR/html4/">hello</table>` +
+			`</Tables>`,
+		tab: Tables{"hello", "world"},
+	},
+	{
+		xml: `<Tables xmlns:f="http://www.w3schools.com/furniture" xmlns:h="http://www.w3.org/TR/html4/">` +
+			`<f:table>world</f:table>` +
+			`<h:table>hello</h:table>` +
+			`</Tables>`,
+		tab: Tables{"hello", "world"},
+	},
+	{
+		xml: `<Tables>` +
+			`<table>bogus</table>` +
+			`</Tables>`,
+		tab: Tables{},
+	},
+	{
+		xml: `<Tables>` +
+			`<table>only</table>` +
+			`</Tables>`,
+		tab: Tables{HTable: "only"},
+		ns:  "http://www.w3.org/TR/html4/",
+	},
+	{
+		xml: `<Tables>` +
+			`<table>only</table>` +
+			`</Tables>`,
+		tab: Tables{FTable: "only"},
+		ns:  "http://www.w3schools.com/furniture",
+	},
+	{
+		xml: `<Tables>` +
+			`<table>only</table>` +
+			`</Tables>`,
+		tab: Tables{},
+		ns:  "something else entirely",
+	},
+}
+
+func TestUnmarshalNS(t *testing.T) {
+	for i, tt := range tables {
+		var dst Tables
+		var err error
+		if tt.ns != "" {
+			d := NewDecoder(strings.NewReader(tt.xml))
+			d.DefaultSpace = tt.ns
+			err = d.Decode(&dst)
+		} else {
+			err = Unmarshal([]byte(tt.xml), &dst)
+		}
+		if err != nil {
+			t.Errorf("#%d: Unmarshal: %v", i, err)
+			continue
+		}
+		want := tt.tab
+		if dst != want {
+			t.Errorf("#%d: dst=%+v, want %+v", i, dst, want)
+		}
+	}
+}
+
+func TestMarshalNS(t *testing.T) {
+	dst := Tables{"hello", "world"}
+	data, err := Marshal(&dst)
+	if err != nil {
+		t.Fatalf("Marshal: %v", err)
+	}
+	want := `<Tables><table xmlns="http://www.w3.org/TR/html4/">hello</table><table xmlns="http://www.w3schools.com/furniture">world</table></Tables>`
+	str := string(data)
+	if str != want {
+		t.Errorf("have: %q\nwant: %q\n", str, want)
+	}
+}
+
+type TableAttrs struct {
+	TAttr TAttr
+}
+
+type TAttr struct {
+	HTable string `xml:"http://www.w3.org/TR/html4/ table,attr"`
+	FTable string `xml:"http://www.w3schools.com/furniture table,attr"`
+	Lang   string `xml:"http://www.w3.org/XML/1998/namespace lang,attr,omitempty"`
+	Other1 string `xml:"http://golang.org/xml/ other,attr,omitempty"`
+	Other2 string `xml:"http://golang.org/xmlfoo/ other,attr,omitempty"`
+	Other3 string `xml:"http://golang.org/json/ other,attr,omitempty"`
+	Other4 string `xml:"http://golang.org/2/json/ other,attr,omitempty"`
+}
+
+var tableAttrs = []struct {
+	xml string
+	tab TableAttrs
+	ns  string
+}{
+	{
+		xml: `<TableAttrs xmlns:f="http://www.w3schools.com/furniture" xmlns:h="http://www.w3.org/TR/html4/"><TAttr ` +
+			`h:table="hello" f:table="world" ` +
+			`/></TableAttrs>`,
+		tab: TableAttrs{TAttr{HTable: "hello", FTable: "world"}},
+	},
+	{
+		xml: `<TableAttrs><TAttr xmlns:f="http://www.w3schools.com/furniture" xmlns:h="http://www.w3.org/TR/html4/" ` +
+			`h:table="hello" f:table="world" ` +
+			`/></TableAttrs>`,
+		tab: TableAttrs{TAttr{HTable: "hello", FTable: "world"}},
+	},
+	{
+		xml: `<TableAttrs><TAttr ` +
+			`h:table="hello" f:table="world" xmlns:f="http://www.w3schools.com/furniture" xmlns:h="http://www.w3.org/TR/html4/" ` +
+			`/></TableAttrs>`,
+		tab: TableAttrs{TAttr{HTable: "hello", FTable: "world"}},
+	},
+	{
+		// Default space does not apply to attribute names.
+		xml: `<TableAttrs xmlns="http://www.w3schools.com/furniture" xmlns:h="http://www.w3.org/TR/html4/"><TAttr ` +
+			`h:table="hello" table="world" ` +
+			`/></TableAttrs>`,
+		tab: TableAttrs{TAttr{HTable: "hello", FTable: ""}},
+	},
+	{
+		// Default space does not apply to attribute names.
+		xml: `<TableAttrs xmlns:f="http://www.w3schools.com/furniture"><TAttr xmlns="http://www.w3.org/TR/html4/" ` +
+			`table="hello" f:table="world" ` +
+			`/></TableAttrs>`,
+		tab: TableAttrs{TAttr{HTable: "", FTable: "world"}},
+	},
+	{
+		xml: `<TableAttrs><TAttr ` +
+			`table="bogus" ` +
+			`/></TableAttrs>`,
+		tab: TableAttrs{},
+	},
+	{
+		// Default space does not apply to attribute names.
+		xml: `<TableAttrs xmlns:h="http://www.w3.org/TR/html4/"><TAttr ` +
+			`h:table="hello" table="world" ` +
+			`/></TableAttrs>`,
+		tab: TableAttrs{TAttr{HTable: "hello", FTable: ""}},
+		ns:  "http://www.w3schools.com/furniture",
+	},
+	{
+		// Default space does not apply to attribute names.
+		xml: `<TableAttrs xmlns:f="http://www.w3schools.com/furniture"><TAttr ` +
+			`table="hello" f:table="world" ` +
+			`/></TableAttrs>`,
+		tab: TableAttrs{TAttr{HTable: "", FTable: "world"}},
+		ns:  "http://www.w3.org/TR/html4/",
+	},
+	{
+		xml: `<TableAttrs><TAttr ` +
+			`table="bogus" ` +
+			`/></TableAttrs>`,
+		tab: TableAttrs{},
+		ns:  "something else entirely",
+	},
+}
+
+func TestUnmarshalNSAttr(t *testing.T) {
+	for i, tt := range tableAttrs {
+		var dst TableAttrs
+		var err error
+		if tt.ns != "" {
+			d := NewDecoder(strings.NewReader(tt.xml))
+			d.DefaultSpace = tt.ns
+			err = d.Decode(&dst)
+		} else {
+			err = Unmarshal([]byte(tt.xml), &dst)
+		}
+		if err != nil {
+			t.Errorf("#%d: Unmarshal: %v", i, err)
+			continue
+		}
+		want := tt.tab
+		if dst != want {
+			t.Errorf("#%d: dst=%+v, want %+v", i, dst, want)
+		}
+	}
+}
+
+func TestMarshalNSAttr(t *testing.T) {
+	src := TableAttrs{TAttr{"hello", "world", "en_US", "other1", "other2", "other3", "other4"}}
+	data, err := Marshal(&src)
+	if err != nil {
+		t.Fatalf("Marshal: %v", err)
+	}
+	want := `<TableAttrs><TAttr xmlns:html4="http://www.w3.org/TR/html4/" html4:table="hello" xmlns:furniture="http://www.w3schools.com/furniture" furniture:table="world" xml:lang="en_US" xmlns:_xml="http://golang.org/xml/" _xml:other="other1" xmlns:_xmlfoo="http://golang.org/xmlfoo/" _xmlfoo:other="other2" xmlns:json="http://golang.org/json/" json:other="other3" xmlns:json_1="http://golang.org/2/json/" json_1:other="other4"></TAttr></TableAttrs>`
+	str := string(data)
+	if str != want {
+		t.Errorf("Marshal:\nhave: %#q\nwant: %#q\n", str, want)
+	}
+
+	var dst TableAttrs
+	if err := Unmarshal(data, &dst); err != nil {
+		t.Errorf("Unmarshal: %v", err)
+	}
+
+	if dst != src {
+		t.Errorf("Unmarshal = %q, want %q", dst, src)
+	}
+}
+
+type MyCharData struct {
+	body string
+}
+
+func (m *MyCharData) UnmarshalXML(d *Decoder, start StartElement) error {
+	for {
+		t, err := d.Token()
+		if err == io.EOF { // found end of element
+			break
+		}
+		if err != nil {
+			return err
+		}
+		if char, ok := t.(CharData); ok {
+			m.body += string(char)
+		}
+	}
+	return nil
+}
+
+var _ Unmarshaler = (*MyCharData)(nil)
+
+func (m *MyCharData) UnmarshalXMLAttr(attr Attr) error {
+	panic("must not call")
+}
+
+type MyAttr struct {
+	attr string
+}
+
+func (m *MyAttr) UnmarshalXMLAttr(attr Attr) error {
+	m.attr = attr.Value
+	return nil
+}
+
+var _ UnmarshalerAttr = (*MyAttr)(nil)
+
+type MyStruct struct {
+	Data *MyCharData
+	Attr *MyAttr `xml:",attr"`
+
+	Data2 MyCharData
+	Attr2 MyAttr `xml:",attr"`
+}
+
+func TestUnmarshaler(t *testing.T) {
+	xml := `<?xml version="1.0" encoding="utf-8"?>
+		<MyStruct Attr="attr1" Attr2="attr2">
+		<Data>hello <!-- comment -->world</Data>
+		<Data2>howdy <!-- comment -->world</Data2>
+		</MyStruct>
+	`
+
+	var m MyStruct
+	if err := Unmarshal([]byte(xml), &m); err != nil {
+		t.Fatal(err)
+	}
+
+	if m.Data == nil || m.Attr == nil || m.Data.body != "hello world" || m.Attr.attr != "attr1" || m.Data2.body != "howdy world" || m.Attr2.attr != "attr2" {
+		t.Errorf("m=%#+v\n", m)
+	}
+}
+
+type Pea struct {
+	Cotelydon string
+}
+
+type Pod struct {
+	Pea any `xml:"Pea"`
+}
+
+// https://golang.org/issue/6836
+func TestUnmarshalIntoInterface(t *testing.T) {
+	pod := new(Pod)
+	pod.Pea = new(Pea)
+	xml := `<Pod><Pea><Cotelydon>Green stuff</Cotelydon></Pea></Pod>`
+	err := Unmarshal([]byte(xml), pod)
+	if err != nil {
+		t.Fatalf("failed to unmarshal %q: %v", xml, err)
+	}
+	pea, ok := pod.Pea.(*Pea)
+	if !ok {
+		t.Fatalf("unmarshaled into wrong type: have %T want *Pea", pod.Pea)
+	}
+	have, want := pea.Cotelydon, "Green stuff"
+	if have != want {
+		t.Errorf("failed to unmarshal into interface, have %q want %q", have, want)
+	}
+}
+
+type X struct {
+	D string `xml:",comment"`
+}
+
+// Issue 11112. Unmarshal must reject invalid comments.
+func TestMalformedComment(t *testing.T) {
+	testData := []string{
+		"<X><!-- a---></X>",
+		"<X><!-- -- --></X>",
+		"<X><!-- a--b --></X>",
+		"<X><!------></X>",
+	}
+	for i, test := range testData {
+		data := []byte(test)
+		v := new(X)
+		if err := Unmarshal(data, v); err == nil {
+			t.Errorf("%d: unmarshal should reject invalid comments", i)
+		}
+	}
+}
+
+type IXField struct {
+	Five        int      `xml:"five"`
+	NotInnerXML []string `xml:",innerxml"`
+}
+
+// Issue 15600. ",innerxml" on a field that can't hold it.
+func TestInvalidInnerXMLType(t *testing.T) {
+	v := new(IXField)
+	if err := Unmarshal([]byte(`<tag><five>5</five><innertag/></tag>`), v); err != nil {
+		t.Errorf("Unmarshal failed: got %v", err)
+	}
+	if v.Five != 5 {
+		t.Errorf("Five = %v, want 5", v.Five)
+	}
+	if v.NotInnerXML != nil {
+		t.Errorf("NotInnerXML = %v, want nil", v.NotInnerXML)
+	}
+}
+
+type Child struct {
+	G struct {
+		I int
+	}
+}
+
+type ChildToEmbed struct {
+	X bool
+}
+
+type Parent struct {
+	I        int
+	IPtr     *int
+	Is       []int
+	IPtrs    []*int
+	F        float32
+	FPtr     *float32
+	Fs       []float32
+	FPtrs    []*float32
+	B        bool
+	BPtr     *bool
+	Bs       []bool
+	BPtrs    []*bool
+	Bytes    []byte
+	BytesPtr *[]byte
+	S        string
+	SPtr     *string
+	Ss       []string
+	SPtrs    []*string
+	MyI      MyInt
+	Child    Child
+	Children []Child
+	ChildPtr *Child
+	ChildToEmbed
+}
+
+const (
+	emptyXML = `
+<Parent>
+    <I></I>
+    <IPtr></IPtr>
+    <Is></Is>
+    <IPtrs></IPtrs>
+    <F></F>
+    <FPtr></FPtr>
+    <Fs></Fs>
+    <FPtrs></FPtrs>
+    <B></B>
+    <BPtr></BPtr>
+    <Bs></Bs>
+    <BPtrs></BPtrs>
+    <Bytes></Bytes>
+    <BytesPtr></BytesPtr>
+    <S></S>
+    <SPtr></SPtr>
+    <Ss></Ss>
+    <SPtrs></SPtrs>
+    <MyI></MyI>
+    <Child></Child>
+    <Children></Children>
+    <ChildPtr></ChildPtr>
+    <X></X>
+</Parent>
+`
+)
+
+// golang.org/issues/13417
+func TestUnmarshalEmptyValues(t *testing.T) {
+	// Test first with a zero-valued dst.
+	v := new(Parent)
+	if err := Unmarshal([]byte(emptyXML), v); err != nil {
+		t.Fatalf("zero: Unmarshal failed: got %v", err)
+	}
+
+	zBytes, zInt, zStr, zFloat, zBool := []byte{}, 0, "", float32(0), false
+	want := &Parent{
+		IPtr:         &zInt,
+		Is:           []int{zInt},
+		IPtrs:        []*int{&zInt},
+		FPtr:         &zFloat,
+		Fs:           []float32{zFloat},
+		FPtrs:        []*float32{&zFloat},
+		BPtr:         &zBool,
+		Bs:           []bool{zBool},
+		BPtrs:        []*bool{&zBool},
+		Bytes:        []byte{},
+		BytesPtr:     &zBytes,
+		SPtr:         &zStr,
+		Ss:           []string{zStr},
+		SPtrs:        []*string{&zStr},
+		Children:     []Child{{}},
+		ChildPtr:     new(Child),
+		ChildToEmbed: ChildToEmbed{},
+	}
+	if !reflect.DeepEqual(v, want) {
+		t.Fatalf("zero: Unmarshal:\nhave:  %#+v\nwant: %#+v", v, want)
+	}
+
+	// Test with a pre-populated dst.
+	// Multiple addressable copies, as pointer-to fields will replace value during unmarshal.
+	vBytes0, vInt0, vStr0, vFloat0, vBool0 := []byte("x"), 1, "x", float32(1), true
+	vBytes1, vInt1, vStr1, vFloat1, vBool1 := []byte("x"), 1, "x", float32(1), true
+	vInt2, vStr2, vFloat2, vBool2 := 1, "x", float32(1), true
+	v = &Parent{
+		I:            vInt0,
+		IPtr:         &vInt1,
+		Is:           []int{vInt0},
+		IPtrs:        []*int{&vInt2},
+		F:            vFloat0,
+		FPtr:         &vFloat1,
+		Fs:           []float32{vFloat0},
+		FPtrs:        []*float32{&vFloat2},
+		B:            vBool0,
+		BPtr:         &vBool1,
+		Bs:           []bool{vBool0},
+		BPtrs:        []*bool{&vBool2},
+		Bytes:        vBytes0,
+		BytesPtr:     &vBytes1,
+		S:            vStr0,
+		SPtr:         &vStr1,
+		Ss:           []string{vStr0},
+		SPtrs:        []*string{&vStr2},
+		MyI:          MyInt(vInt0),
+		Child:        Child{G: struct{ I int }{I: vInt0}},
+		Children:     []Child{{G: struct{ I int }{I: vInt0}}},
+		ChildPtr:     &Child{G: struct{ I int }{I: vInt0}},
+		ChildToEmbed: ChildToEmbed{X: vBool0},
+	}
+	if err := Unmarshal([]byte(emptyXML), v); err != nil {
+		t.Fatalf("populated: Unmarshal failed: got %v", err)
+	}
+
+	want = &Parent{
+		IPtr:     &zInt,
+		Is:       []int{vInt0, zInt},
+		IPtrs:    []*int{&vInt0, &zInt},
+		FPtr:     &zFloat,
+		Fs:       []float32{vFloat0, zFloat},
+		FPtrs:    []*float32{&vFloat0, &zFloat},
+		BPtr:     &zBool,
+		Bs:       []bool{vBool0, zBool},
+		BPtrs:    []*bool{&vBool0, &zBool},
+		Bytes:    []byte{},
+		BytesPtr: &zBytes,
+		SPtr:     &zStr,
+		Ss:       []string{vStr0, zStr},
+		SPtrs:    []*string{&vStr0, &zStr},
+		Child:    Child{G: struct{ I int }{I: vInt0}}, // I should == zInt0? (zero value)
+		Children: []Child{{G: struct{ I int }{I: vInt0}}, {}},
+		ChildPtr: &Child{G: struct{ I int }{I: vInt0}}, // I should == zInt0? (zero value)
+	}
+	if !reflect.DeepEqual(v, want) {
+		t.Fatalf("populated: Unmarshal:\nhave:  %#+v\nwant: %#+v", v, want)
+	}
+}
+
+type WhitespaceValuesParent struct {
+	BFalse bool
+	BTrue  bool
+	I      int
+	INeg   int
+	I8     int8
+	I8Neg  int8
+	I16    int16
+	I16Neg int16
+	I32    int32
+	I32Neg int32
+	I64    int64
+	I64Neg int64
+	UI     uint
+	UI8    uint8
+	UI16   uint16
+	UI32   uint32
+	UI64   uint64
+	F32    float32
+	F32Neg float32
+	F64    float64
+	F64Neg float64
+}
+
+const whitespaceValuesXML = `
+<WhitespaceValuesParent>
+    <BFalse>   false   </BFalse>
+    <BTrue>   true   </BTrue>
+    <I>   266703   </I>
+    <INeg>   -266703   </INeg>
+    <I8>  112  </I8>
+    <I8Neg>  -112  </I8Neg>
+    <I16>  6703  </I16>
+    <I16Neg>  -6703  </I16Neg>
+    <I32>  266703  </I32>
+    <I32Neg>  -266703  </I32Neg>
+    <I64>  266703  </I64>
+    <I64Neg>  -266703  </I64Neg>
+    <UI>   266703   </UI>
+    <UI8>  112  </UI8>
+    <UI16>  6703  </UI16>
+    <UI32>  266703  </UI32>
+    <UI64>  266703  </UI64>
+    <F32>  266.703  </F32>
+    <F32Neg>  -266.703  </F32Neg>
+    <F64>  266.703  </F64>
+    <F64Neg>  -266.703  </F64Neg>
+</WhitespaceValuesParent>
+`
+
+// golang.org/issues/22146
+func TestUnmarshalWhitespaceValues(t *testing.T) {
+	v := WhitespaceValuesParent{}
+	if err := Unmarshal([]byte(whitespaceValuesXML), &v); err != nil {
+		t.Fatalf("whitespace values: Unmarshal failed: got %v", err)
+	}
+
+	want := WhitespaceValuesParent{
+		BFalse: false,
+		BTrue:  true,
+		I:      266703,
+		INeg:   -266703,
+		I8:     112,
+		I8Neg:  -112,
+		I16:    6703,
+		I16Neg: -6703,
+		I32:    266703,
+		I32Neg: -266703,
+		I64:    266703,
+		I64Neg: -266703,
+		UI:     266703,
+		UI8:    112,
+		UI16:   6703,
+		UI32:   266703,
+		UI64:   266703,
+		F32:    266.703,
+		F32Neg: -266.703,
+		F64:    266.703,
+		F64Neg: -266.703,
+	}
+	if v != want {
+		t.Fatalf("whitespace values: Unmarshal:\nhave: %#+v\nwant: %#+v", v, want)
+	}
+}
+
+type WhitespaceAttrsParent struct {
+	BFalse bool    `xml:",attr"`
+	BTrue  bool    `xml:",attr"`
+	I      int     `xml:",attr"`
+	INeg   int     `xml:",attr"`
+	I8     int8    `xml:",attr"`
+	I8Neg  int8    `xml:",attr"`
+	I16    int16   `xml:",attr"`
+	I16Neg int16   `xml:",attr"`
+	I32    int32   `xml:",attr"`
+	I32Neg int32   `xml:",attr"`
+	I64    int64   `xml:",attr"`
+	I64Neg int64   `xml:",attr"`
+	UI     uint    `xml:",attr"`
+	UI8    uint8   `xml:",attr"`
+	UI16   uint16  `xml:",attr"`
+	UI32   uint32  `xml:",attr"`
+	UI64   uint64  `xml:",attr"`
+	F32    float32 `xml:",attr"`
+	F32Neg float32 `xml:",attr"`
+	F64    float64 `xml:",attr"`
+	F64Neg float64 `xml:",attr"`
+}
+
+const whitespaceAttrsXML = `
+<WhitespaceAttrsParent
+    BFalse="  false  "
+    BTrue="  true  "
+    I="  266703  "
+    INeg="  -266703  "
+    I8="  112  "
+    I8Neg="  -112  "
+    I16="  6703  "
+    I16Neg="  -6703  "
+    I32="  266703  "
+    I32Neg="  -266703  "
+    I64="  266703  "
+    I64Neg="  -266703  "
+    UI="  266703  "
+    UI8="  112  "
+    UI16="  6703  "
+    UI32="  266703  "
+    UI64="  266703  "
+    F32="  266.703  "
+    F32Neg="  -266.703  "
+    F64="  266.703  "
+    F64Neg="  -266.703  "
+>
+</WhitespaceAttrsParent>
+`
+
+// golang.org/issues/22146
+func TestUnmarshalWhitespaceAttrs(t *testing.T) {
+	v := WhitespaceAttrsParent{}
+	if err := Unmarshal([]byte(whitespaceAttrsXML), &v); err != nil {
+		t.Fatalf("whitespace attrs: Unmarshal failed: got %v", err)
+	}
+
+	want := WhitespaceAttrsParent{
+		BFalse: false,
+		BTrue:  true,
+		I:      266703,
+		INeg:   -266703,
+		I8:     112,
+		I8Neg:  -112,
+		I16:    6703,
+		I16Neg: -6703,
+		I32:    266703,
+		I32Neg: -266703,
+		I64:    266703,
+		I64Neg: -266703,
+		UI:     266703,
+		UI8:    112,
+		UI16:   6703,
+		UI32:   266703,
+		UI64:   266703,
+		F32:    266.703,
+		F32Neg: -266.703,
+		F64:    266.703,
+		F64Neg: -266.703,
+	}
+	if v != want {
+		t.Fatalf("whitespace attrs: Unmarshal:\nhave: %#+v\nwant: %#+v", v, want)
+	}
+}
+
+func TestCVE202230633(t *testing.T) {
+	if testing.Short() {
+		t.Skip("test requires significant memory")
+	}
+	defer func() {
+		p := recover()
+		if p != nil {
+			t.Fatal("Unmarshal panicked")
+		}
+	}()
+	var example struct {
+		Things []string
+	}
+	Unmarshal(bytes.Repeat([]byte("<a>"), 17_000_000), &example)
+}
+
+func TestCVE202228131(t *testing.T) {
+	type nested struct {
+		Parent *nested `xml:",any"`
+	}
+	var n nested
+	err := Unmarshal(bytes.Repeat([]byte("<a>"), maxUnmarshalDepth+1), &n)
+	if err == nil {
+		t.Fatal("Unmarshal did not fail")
+	} else if !errors.Is(err, errExeceededMaxUnmarshalDepth) {
+		t.Fatalf("Unmarshal unexpected error: got %q, want %q", err, errExeceededMaxUnmarshalDepth)
+	}
+}
diff --git a/src/encoding/xml/typeinfo.go b/src/encoding/xml/typeinfo.go
new file mode 100644
index 0000000..6b399b9
--- /dev/null
+++ b/src/encoding/xml/typeinfo.go
@@ -0,0 +1,374 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package xml
+
+import (
+	"fmt"
+	"reflect"
+	"strings"
+	"sync"
+)
+
+// typeInfo holds details for the xml representation of a type.
+type typeInfo struct {
+	xmlname *fieldInfo
+	fields  []fieldInfo
+}
+
+// fieldInfo holds details for the xml representation of a single field.
+type fieldInfo struct {
+	idx     []int
+	name    string
+	xmlns   string
+	flags   fieldFlags
+	parents []string
+}
+
+type fieldFlags int
+
+const (
+	fElement fieldFlags = 1 << iota
+	fAttr
+	fCDATA
+	fCharData
+	fInnerXML
+	fComment
+	fAny
+
+	fOmitEmpty
+
+	fMode = fElement | fAttr | fCDATA | fCharData | fInnerXML | fComment | fAny
+
+	xmlName = "XMLName"
+)
+
+var tinfoMap sync.Map // map[reflect.Type]*typeInfo
+
+var nameType = reflect.TypeOf(Name{})
+
+// getTypeInfo returns the typeInfo structure with details necessary
+// for marshaling and unmarshaling typ.
+func getTypeInfo(typ reflect.Type) (*typeInfo, error) {
+	if ti, ok := tinfoMap.Load(typ); ok {
+		return ti.(*typeInfo), nil
+	}
+
+	tinfo := &typeInfo{}
+	if typ.Kind() == reflect.Struct && typ != nameType {
+		n := typ.NumField()
+		for i := 0; i < n; i++ {
+			f := typ.Field(i)
+			if (!f.IsExported() && !f.Anonymous) || f.Tag.Get("xml") == "-" {
+				continue // Private field
+			}
+
+			// For embedded structs, embed its fields.
+			if f.Anonymous {
+				t := f.Type
+				if t.Kind() == reflect.Pointer {
+					t = t.Elem()
+				}
+				if t.Kind() == reflect.Struct {
+					inner, err := getTypeInfo(t)
+					if err != nil {
+						return nil, err
+					}
+					if tinfo.xmlname == nil {
+						tinfo.xmlname = inner.xmlname
+					}
+					for _, finfo := range inner.fields {
+						finfo.idx = append([]int{i}, finfo.idx...)
+						if err := addFieldInfo(typ, tinfo, &finfo); err != nil {
+							return nil, err
+						}
+					}
+					continue
+				}
+			}
+
+			finfo, err := structFieldInfo(typ, &f)
+			if err != nil {
+				return nil, err
+			}
+
+			if f.Name == xmlName {
+				tinfo.xmlname = finfo
+				continue
+			}
+
+			// Add the field if it doesn't conflict with other fields.
+			if err := addFieldInfo(typ, tinfo, finfo); err != nil {
+				return nil, err
+			}
+		}
+	}
+
+	ti, _ := tinfoMap.LoadOrStore(typ, tinfo)
+	return ti.(*typeInfo), nil
+}
+
+// structFieldInfo builds and returns a fieldInfo for f.
+func structFieldInfo(typ reflect.Type, f *reflect.StructField) (*fieldInfo, error) {
+	finfo := &fieldInfo{idx: f.Index}
+
+	// Split the tag from the xml namespace if necessary.
+	tag := f.Tag.Get("xml")
+	if ns, t, ok := strings.Cut(tag, " "); ok {
+		finfo.xmlns, tag = ns, t
+	}
+
+	// Parse flags.
+	tokens := strings.Split(tag, ",")
+	if len(tokens) == 1 {
+		finfo.flags = fElement
+	} else {
+		tag = tokens[0]
+		for _, flag := range tokens[1:] {
+			switch flag {
+			case "attr":
+				finfo.flags |= fAttr
+			case "cdata":
+				finfo.flags |= fCDATA
+			case "chardata":
+				finfo.flags |= fCharData
+			case "innerxml":
+				finfo.flags |= fInnerXML
+			case "comment":
+				finfo.flags |= fComment
+			case "any":
+				finfo.flags |= fAny
+			case "omitempty":
+				finfo.flags |= fOmitEmpty
+			}
+		}
+
+		// Validate the flags used.
+		valid := true
+		switch mode := finfo.flags & fMode; mode {
+		case 0:
+			finfo.flags |= fElement
+		case fAttr, fCDATA, fCharData, fInnerXML, fComment, fAny, fAny | fAttr:
+			if f.Name == xmlName || tag != "" && mode != fAttr {
+				valid = false
+			}
+		default:
+			// This will also catch multiple modes in a single field.
+			valid = false
+		}
+		if finfo.flags&fMode == fAny {
+			finfo.flags |= fElement
+		}
+		if finfo.flags&fOmitEmpty != 0 && finfo.flags&(fElement|fAttr) == 0 {
+			valid = false
+		}
+		if !valid {
+			return nil, fmt.Errorf("xml: invalid tag in field %s of type %s: %q",
+				f.Name, typ, f.Tag.Get("xml"))
+		}
+	}
+
+	// Use of xmlns without a name is not allowed.
+	if finfo.xmlns != "" && tag == "" {
+		return nil, fmt.Errorf("xml: namespace without name in field %s of type %s: %q",
+			f.Name, typ, f.Tag.Get("xml"))
+	}
+
+	if f.Name == xmlName {
+		// The XMLName field records the XML element name. Don't
+		// process it as usual because its name should default to
+		// empty rather than to the field name.
+		finfo.name = tag
+		return finfo, nil
+	}
+
+	if tag == "" {
+		// If the name part of the tag is completely empty, get
+		// default from XMLName of underlying struct if feasible,
+		// or field name otherwise.
+		if xmlname := lookupXMLName(f.Type); xmlname != nil {
+			finfo.xmlns, finfo.name = xmlname.xmlns, xmlname.name
+		} else {
+			finfo.name = f.Name
+		}
+		return finfo, nil
+	}
+
+	// Prepare field name and parents.
+	parents := strings.Split(tag, ">")
+	if parents[0] == "" {
+		parents[0] = f.Name
+	}
+	if parents[len(parents)-1] == "" {
+		return nil, fmt.Errorf("xml: trailing '>' in field %s of type %s", f.Name, typ)
+	}
+	finfo.name = parents[len(parents)-1]
+	if len(parents) > 1 {
+		if (finfo.flags & fElement) == 0 {
+			return nil, fmt.Errorf("xml: %s chain not valid with %s flag", tag, strings.Join(tokens[1:], ","))
+		}
+		finfo.parents = parents[:len(parents)-1]
+	}
+
+	// If the field type has an XMLName field, the names must match
+	// so that the behavior of both marshaling and unmarshaling
+	// is straightforward and unambiguous.
+	if finfo.flags&fElement != 0 {
+		ftyp := f.Type
+		xmlname := lookupXMLName(ftyp)
+		if xmlname != nil && xmlname.name != finfo.name {
+			return nil, fmt.Errorf("xml: name %q in tag of %s.%s conflicts with name %q in %s.XMLName",
+				finfo.name, typ, f.Name, xmlname.name, ftyp)
+		}
+	}
+	return finfo, nil
+}
+
+// lookupXMLName returns the fieldInfo for typ's XMLName field
+// in case it exists and has a valid xml field tag, otherwise
+// it returns nil.
+func lookupXMLName(typ reflect.Type) (xmlname *fieldInfo) {
+	for typ.Kind() == reflect.Pointer {
+		typ = typ.Elem()
+	}
+	if typ.Kind() != reflect.Struct {
+		return nil
+	}
+	for i, n := 0, typ.NumField(); i < n; i++ {
+		f := typ.Field(i)
+		if f.Name != xmlName {
+			continue
+		}
+		finfo, err := structFieldInfo(typ, &f)
+		if err == nil && finfo.name != "" {
+			return finfo
+		}
+		// Also consider errors as a non-existent field tag
+		// and let getTypeInfo itself report the error.
+		break
+	}
+	return nil
+}
+
+func min(a, b int) int {
+	if a <= b {
+		return a
+	}
+	return b
+}
+
+// addFieldInfo adds finfo to tinfo.fields if there are no
+// conflicts, or if conflicts arise from previous fields that were
+// obtained from deeper embedded structures than finfo. In the latter
+// case, the conflicting entries are dropped.
+// A conflict occurs when the path (parent + name) to a field is
+// itself a prefix of another path, or when two paths match exactly.
+// It is okay for field paths to share a common, shorter prefix.
+func addFieldInfo(typ reflect.Type, tinfo *typeInfo, newf *fieldInfo) error {
+	var conflicts []int
+Loop:
+	// First, figure all conflicts. Most working code will have none.
+	for i := range tinfo.fields {
+		oldf := &tinfo.fields[i]
+		if oldf.flags&fMode != newf.flags&fMode {
+			continue
+		}
+		if oldf.xmlns != "" && newf.xmlns != "" && oldf.xmlns != newf.xmlns {
+			continue
+		}
+		minl := min(len(newf.parents), len(oldf.parents))
+		for p := 0; p < minl; p++ {
+			if oldf.parents[p] != newf.parents[p] {
+				continue Loop
+			}
+		}
+		if len(oldf.parents) > len(newf.parents) {
+			if oldf.parents[len(newf.parents)] == newf.name {
+				conflicts = append(conflicts, i)
+			}
+		} else if len(oldf.parents) < len(newf.parents) {
+			if newf.parents[len(oldf.parents)] == oldf.name {
+				conflicts = append(conflicts, i)
+			}
+		} else {
+			if newf.name == oldf.name {
+				conflicts = append(conflicts, i)
+			}
+		}
+	}
+	// Without conflicts, add the new field and return.
+	if conflicts == nil {
+		tinfo.fields = append(tinfo.fields, *newf)
+		return nil
+	}
+
+	// If any conflict is shallower, ignore the new field.
+	// This matches the Go field resolution on embedding.
+	for _, i := range conflicts {
+		if len(tinfo.fields[i].idx) < len(newf.idx) {
+			return nil
+		}
+	}
+
+	// Otherwise, if any of them is at the same depth level, it's an error.
+	for _, i := range conflicts {
+		oldf := &tinfo.fields[i]
+		if len(oldf.idx) == len(newf.idx) {
+			f1 := typ.FieldByIndex(oldf.idx)
+			f2 := typ.FieldByIndex(newf.idx)
+			return &TagPathError{typ, f1.Name, f1.Tag.Get("xml"), f2.Name, f2.Tag.Get("xml")}
+		}
+	}
+
+	// Otherwise, the new field is shallower, and thus takes precedence,
+	// so drop the conflicting fields from tinfo and append the new one.
+	for c := len(conflicts) - 1; c >= 0; c-- {
+		i := conflicts[c]
+		copy(tinfo.fields[i:], tinfo.fields[i+1:])
+		tinfo.fields = tinfo.fields[:len(tinfo.fields)-1]
+	}
+	tinfo.fields = append(tinfo.fields, *newf)
+	return nil
+}
+
+// A TagPathError represents an error in the unmarshaling process
+// caused by the use of field tags with conflicting paths.
+type TagPathError struct {
+	Struct       reflect.Type
+	Field1, Tag1 string
+	Field2, Tag2 string
+}
+
+func (e *TagPathError) Error() string {
+	return fmt.Sprintf("%s field %q with tag %q conflicts with field %q with tag %q", e.Struct, e.Field1, e.Tag1, e.Field2, e.Tag2)
+}
+
+const (
+	initNilPointers     = true
+	dontInitNilPointers = false
+)
+
+// value returns v's field value corresponding to finfo.
+// It's equivalent to v.FieldByIndex(finfo.idx), but when passed
+// initNilPointers, it initializes and dereferences pointers as necessary.
+// When passed dontInitNilPointers and a nil pointer is reached, the function
+// returns a zero reflect.Value.
+func (finfo *fieldInfo) value(v reflect.Value, shouldInitNilPointers bool) reflect.Value {
+	for i, x := range finfo.idx {
+		if i > 0 {
+			t := v.Type()
+			if t.Kind() == reflect.Pointer && t.Elem().Kind() == reflect.Struct {
+				if v.IsNil() {
+					if !shouldInitNilPointers {
+						return reflect.Value{}
+					}
+					v.Set(reflect.New(v.Type().Elem()))
+				}
+				v = v.Elem()
+			}
+		}
+		v = v.Field(x)
+	}
+	return v
+}
diff --git a/src/encoding/xml/xml.go b/src/encoding/xml/xml.go
new file mode 100644
index 0000000..8a0a9c2
--- /dev/null
+++ b/src/encoding/xml/xml.go
@@ -0,0 +1,2057 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package xml implements a simple XML 1.0 parser that
+// understands XML name spaces.
+package xml
+
+// References:
+//    Annotated XML spec: https://www.xml.com/axml/testaxml.htm
+//    XML name spaces: https://www.w3.org/TR/REC-xml-names/
+
+// TODO(rsc):
+//	Test error handling.
+
+import (
+	"bufio"
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"strconv"
+	"strings"
+	"unicode"
+	"unicode/utf8"
+)
+
+// A SyntaxError represents a syntax error in the XML input stream.
+type SyntaxError struct {
+	Msg  string
+	Line int
+}
+
+func (e *SyntaxError) Error() string {
+	return "XML syntax error on line " + strconv.Itoa(e.Line) + ": " + e.Msg
+}
+
+// A Name represents an XML name (Local) annotated
+// with a name space identifier (Space).
+// In tokens returned by Decoder.Token, the Space identifier
+// is given as a canonical URL, not the short prefix used
+// in the document being parsed.
+type Name struct {
+	Space, Local string
+}
+
+// An Attr represents an attribute in an XML element (Name=Value).
+type Attr struct {
+	Name  Name
+	Value string
+}
+
+// A Token is an interface holding one of the token types:
+// StartElement, EndElement, CharData, Comment, ProcInst, or Directive.
+type Token any
+
+// A StartElement represents an XML start element.
+type StartElement struct {
+	Name Name
+	Attr []Attr
+}
+
+// Copy creates a new copy of StartElement.
+func (e StartElement) Copy() StartElement {
+	attrs := make([]Attr, len(e.Attr))
+	copy(attrs, e.Attr)
+	e.Attr = attrs
+	return e
+}
+
+// End returns the corresponding XML end element.
+func (e StartElement) End() EndElement {
+	return EndElement{e.Name}
+}
+
+// An EndElement represents an XML end element.
+type EndElement struct {
+	Name Name
+}
+
+// A CharData represents XML character data (raw text),
+// in which XML escape sequences have been replaced by
+// the characters they represent.
+type CharData []byte
+
+func makeCopy(b []byte) []byte {
+	b1 := make([]byte, len(b))
+	copy(b1, b)
+	return b1
+}
+
+// Copy creates a new copy of CharData.
+func (c CharData) Copy() CharData { return CharData(makeCopy(c)) }
+
+// A Comment represents an XML comment of the form <!--comment-->.
+// The bytes do not include the <!-- and --> comment markers.
+type Comment []byte
+
+// Copy creates a new copy of Comment.
+func (c Comment) Copy() Comment { return Comment(makeCopy(c)) }
+
+// A ProcInst represents an XML processing instruction of the form <?target inst?>
+type ProcInst struct {
+	Target string
+	Inst   []byte
+}
+
+// Copy creates a new copy of ProcInst.
+func (p ProcInst) Copy() ProcInst {
+	p.Inst = makeCopy(p.Inst)
+	return p
+}
+
+// A Directive represents an XML directive of the form <!text>.
+// The bytes do not include the <! and > markers.
+type Directive []byte
+
+// Copy creates a new copy of Directive.
+func (d Directive) Copy() Directive { return Directive(makeCopy(d)) }
+
+// CopyToken returns a copy of a Token.
+func CopyToken(t Token) Token {
+	switch v := t.(type) {
+	case CharData:
+		return v.Copy()
+	case Comment:
+		return v.Copy()
+	case Directive:
+		return v.Copy()
+	case ProcInst:
+		return v.Copy()
+	case StartElement:
+		return v.Copy()
+	}
+	return t
+}
+
+// A TokenReader is anything that can decode a stream of XML tokens, including a
+// Decoder.
+//
+// When Token encounters an error or end-of-file condition after successfully
+// reading a token, it returns the token. It may return the (non-nil) error from
+// the same call or return the error (and a nil token) from a subsequent call.
+// An instance of this general case is that a TokenReader returning a non-nil
+// token at the end of the token stream may return either io.EOF or a nil error.
+// The next Read should return nil, io.EOF.
+//
+// Implementations of Token are discouraged from returning a nil token with a
+// nil error. Callers should treat a return of nil, nil as indicating that
+// nothing happened; in particular it does not indicate EOF.
+type TokenReader interface {
+	Token() (Token, error)
+}
+
+// A Decoder represents an XML parser reading a particular input stream.
+// The parser assumes that its input is encoded in UTF-8.
+type Decoder struct {
+	// Strict defaults to true, enforcing the requirements
+	// of the XML specification.
+	// If set to false, the parser allows input containing common
+	// mistakes:
+	//	* If an element is missing an end tag, the parser invents
+	//	  end tags as necessary to keep the return values from Token
+	//	  properly balanced.
+	//	* In attribute values and character data, unknown or malformed
+	//	  character entities (sequences beginning with &) are left alone.
+	//
+	// Setting:
+	//
+	//	d.Strict = false
+	//	d.AutoClose = xml.HTMLAutoClose
+	//	d.Entity = xml.HTMLEntity
+	//
+	// creates a parser that can handle typical HTML.
+	//
+	// Strict mode does not enforce the requirements of the XML name spaces TR.
+	// In particular it does not reject name space tags using undefined prefixes.
+	// Such tags are recorded with the unknown prefix as the name space URL.
+	Strict bool
+
+	// When Strict == false, AutoClose indicates a set of elements to
+	// consider closed immediately after they are opened, regardless
+	// of whether an end element is present.
+	AutoClose []string
+
+	// Entity can be used to map non-standard entity names to string replacements.
+	// The parser behaves as if these standard mappings are present in the map,
+	// regardless of the actual map content:
+	//
+	//	"lt": "<",
+	//	"gt": ">",
+	//	"amp": "&",
+	//	"apos": "'",
+	//	"quot": `"`,
+	Entity map[string]string
+
+	// CharsetReader, if non-nil, defines a function to generate
+	// charset-conversion readers, converting from the provided
+	// non-UTF-8 charset into UTF-8. If CharsetReader is nil or
+	// returns an error, parsing stops with an error. One of the
+	// CharsetReader's result values must be non-nil.
+	CharsetReader func(charset string, input io.Reader) (io.Reader, error)
+
+	// DefaultSpace sets the default name space used for unadorned tags,
+	// as if the entire XML stream were wrapped in an element containing
+	// the attribute xmlns="DefaultSpace".
+	DefaultSpace string
+
+	r              io.ByteReader
+	t              TokenReader
+	buf            bytes.Buffer
+	saved          *bytes.Buffer
+	stk            *stack
+	free           *stack
+	needClose      bool
+	toClose        Name
+	nextToken      Token
+	nextByte       int
+	ns             map[string]string
+	err            error
+	line           int
+	offset         int64
+	unmarshalDepth int
+}
+
+// NewDecoder creates a new XML parser reading from r.
+// If r does not implement io.ByteReader, NewDecoder will
+// do its own buffering.
+func NewDecoder(r io.Reader) *Decoder {
+	d := &Decoder{
+		ns:       make(map[string]string),
+		nextByte: -1,
+		line:     1,
+		Strict:   true,
+	}
+	d.switchToReader(r)
+	return d
+}
+
+// NewTokenDecoder creates a new XML parser using an underlying token stream.
+func NewTokenDecoder(t TokenReader) *Decoder {
+	// Is it already a Decoder?
+	if d, ok := t.(*Decoder); ok {
+		return d
+	}
+	d := &Decoder{
+		ns:       make(map[string]string),
+		t:        t,
+		nextByte: -1,
+		line:     1,
+		Strict:   true,
+	}
+	return d
+}
+
+// Token returns the next XML token in the input stream.
+// At the end of the input stream, Token returns nil, io.EOF.
+//
+// Slices of bytes in the returned token data refer to the
+// parser's internal buffer and remain valid only until the next
+// call to Token. To acquire a copy of the bytes, call CopyToken
+// or the token's Copy method.
+//
+// Token expands self-closing elements such as <br>
+// into separate start and end elements returned by successive calls.
+//
+// Token guarantees that the StartElement and EndElement
+// tokens it returns are properly nested and matched:
+// if Token encounters an unexpected end element
+// or EOF before all expected end elements,
+// it will return an error.
+//
+// Token implements XML name spaces as described by
+// https://www.w3.org/TR/REC-xml-names/. Each of the
+// Name structures contained in the Token has the Space
+// set to the URL identifying its name space when known.
+// If Token encounters an unrecognized name space prefix,
+// it uses the prefix as the Space rather than report an error.
+func (d *Decoder) Token() (Token, error) {
+	var t Token
+	var err error
+	if d.stk != nil && d.stk.kind == stkEOF {
+		return nil, io.EOF
+	}
+	if d.nextToken != nil {
+		t = d.nextToken
+		d.nextToken = nil
+	} else {
+		if t, err = d.rawToken(); t == nil && err != nil {
+			if err == io.EOF && d.stk != nil && d.stk.kind != stkEOF {
+				err = d.syntaxError("unexpected EOF")
+			}
+			return nil, err
+		}
+		// We still have a token to process, so clear any
+		// errors (e.g. EOF) and proceed.
+		err = nil
+	}
+	if !d.Strict {
+		if t1, ok := d.autoClose(t); ok {
+			d.nextToken = t
+			t = t1
+		}
+	}
+	switch t1 := t.(type) {
+	case StartElement:
+		// In XML name spaces, the translations listed in the
+		// attributes apply to the element name and
+		// to the other attribute names, so process
+		// the translations first.
+		for _, a := range t1.Attr {
+			if a.Name.Space == xmlnsPrefix {
+				v, ok := d.ns[a.Name.Local]
+				d.pushNs(a.Name.Local, v, ok)
+				d.ns[a.Name.Local] = a.Value
+			}
+			if a.Name.Space == "" && a.Name.Local == xmlnsPrefix {
+				// Default space for untagged names
+				v, ok := d.ns[""]
+				d.pushNs("", v, ok)
+				d.ns[""] = a.Value
+			}
+		}
+
+		d.translate(&t1.Name, true)
+		for i := range t1.Attr {
+			d.translate(&t1.Attr[i].Name, false)
+		}
+		d.pushElement(t1.Name)
+		t = t1
+
+	case EndElement:
+		d.translate(&t1.Name, true)
+		if !d.popElement(&t1) {
+			return nil, d.err
+		}
+		t = t1
+	}
+	return t, err
+}
+
+const (
+	xmlURL      = "http://www.w3.org/XML/1998/namespace"
+	xmlnsPrefix = "xmlns"
+	xmlPrefix   = "xml"
+)
+
+// Apply name space translation to name n.
+// The default name space (for Space=="")
+// applies only to element names, not to attribute names.
+func (d *Decoder) translate(n *Name, isElementName bool) {
+	switch {
+	case n.Space == xmlnsPrefix:
+		return
+	case n.Space == "" && !isElementName:
+		return
+	case n.Space == xmlPrefix:
+		n.Space = xmlURL
+	case n.Space == "" && n.Local == xmlnsPrefix:
+		return
+	}
+	if v, ok := d.ns[n.Space]; ok {
+		n.Space = v
+	} else if n.Space == "" {
+		n.Space = d.DefaultSpace
+	}
+}
+
+func (d *Decoder) switchToReader(r io.Reader) {
+	// Get efficient byte at a time reader.
+	// Assume that if reader has its own
+	// ReadByte, it's efficient enough.
+	// Otherwise, use bufio.
+	if rb, ok := r.(io.ByteReader); ok {
+		d.r = rb
+	} else {
+		d.r = bufio.NewReader(r)
+	}
+}
+
+// Parsing state - stack holds old name space translations
+// and the current set of open elements. The translations to pop when
+// ending a given tag are *below* it on the stack, which is
+// more work but forced on us by XML.
+type stack struct {
+	next *stack
+	kind int
+	name Name
+	ok   bool
+}
+
+const (
+	stkStart = iota
+	stkNs
+	stkEOF
+)
+
+func (d *Decoder) push(kind int) *stack {
+	s := d.free
+	if s != nil {
+		d.free = s.next
+	} else {
+		s = new(stack)
+	}
+	s.next = d.stk
+	s.kind = kind
+	d.stk = s
+	return s
+}
+
+func (d *Decoder) pop() *stack {
+	s := d.stk
+	if s != nil {
+		d.stk = s.next
+		s.next = d.free
+		d.free = s
+	}
+	return s
+}
+
+// Record that after the current element is finished
+// (that element is already pushed on the stack)
+// Token should return EOF until popEOF is called.
+func (d *Decoder) pushEOF() {
+	// Walk down stack to find Start.
+	// It might not be the top, because there might be stkNs
+	// entries above it.
+	start := d.stk
+	for start.kind != stkStart {
+		start = start.next
+	}
+	// The stkNs entries below a start are associated with that
+	// element too; skip over them.
+	for start.next != nil && start.next.kind == stkNs {
+		start = start.next
+	}
+	s := d.free
+	if s != nil {
+		d.free = s.next
+	} else {
+		s = new(stack)
+	}
+	s.kind = stkEOF
+	s.next = start.next
+	start.next = s
+}
+
+// Undo a pushEOF.
+// The element must have been finished, so the EOF should be at the top of the stack.
+func (d *Decoder) popEOF() bool {
+	if d.stk == nil || d.stk.kind != stkEOF {
+		return false
+	}
+	d.pop()
+	return true
+}
+
+// Record that we are starting an element with the given name.
+func (d *Decoder) pushElement(name Name) {
+	s := d.push(stkStart)
+	s.name = name
+}
+
+// Record that we are changing the value of ns[local].
+// The old value is url, ok.
+func (d *Decoder) pushNs(local string, url string, ok bool) {
+	s := d.push(stkNs)
+	s.name.Local = local
+	s.name.Space = url
+	s.ok = ok
+}
+
+// Creates a SyntaxError with the current line number.
+func (d *Decoder) syntaxError(msg string) error {
+	return &SyntaxError{Msg: msg, Line: d.line}
+}
+
+// Record that we are ending an element with the given name.
+// The name must match the record at the top of the stack,
+// which must be a pushElement record.
+// After popping the element, apply any undo records from
+// the stack to restore the name translations that existed
+// before we saw this element.
+func (d *Decoder) popElement(t *EndElement) bool {
+	s := d.pop()
+	name := t.Name
+	switch {
+	case s == nil || s.kind != stkStart:
+		d.err = d.syntaxError("unexpected end element </" + name.Local + ">")
+		return false
+	case s.name.Local != name.Local:
+		if !d.Strict {
+			d.needClose = true
+			d.toClose = t.Name
+			t.Name = s.name
+			return true
+		}
+		d.err = d.syntaxError("element <" + s.name.Local + "> closed by </" + name.Local + ">")
+		return false
+	case s.name.Space != name.Space:
+		d.err = d.syntaxError("element <" + s.name.Local + "> in space " + s.name.Space +
+			"closed by </" + name.Local + "> in space " + name.Space)
+		return false
+	}
+
+	// Pop stack until a Start or EOF is on the top, undoing the
+	// translations that were associated with the element we just closed.
+	for d.stk != nil && d.stk.kind != stkStart && d.stk.kind != stkEOF {
+		s := d.pop()
+		if s.ok {
+			d.ns[s.name.Local] = s.name.Space
+		} else {
+			delete(d.ns, s.name.Local)
+		}
+	}
+
+	return true
+}
+
+// If the top element on the stack is autoclosing and
+// t is not the end tag, invent the end tag.
+func (d *Decoder) autoClose(t Token) (Token, bool) {
+	if d.stk == nil || d.stk.kind != stkStart {
+		return nil, false
+	}
+	name := strings.ToLower(d.stk.name.Local)
+	for _, s := range d.AutoClose {
+		if strings.ToLower(s) == name {
+			// This one should be auto closed if t doesn't close it.
+			et, ok := t.(EndElement)
+			if !ok || et.Name.Local != name {
+				return EndElement{d.stk.name}, true
+			}
+			break
+		}
+	}
+	return nil, false
+}
+
+var errRawToken = errors.New("xml: cannot use RawToken from UnmarshalXML method")
+
+// RawToken is like Token but does not verify that
+// start and end elements match and does not translate
+// name space prefixes to their corresponding URLs.
+func (d *Decoder) RawToken() (Token, error) {
+	if d.unmarshalDepth > 0 {
+		return nil, errRawToken
+	}
+	return d.rawToken()
+}
+
+func (d *Decoder) rawToken() (Token, error) {
+	if d.t != nil {
+		return d.t.Token()
+	}
+	if d.err != nil {
+		return nil, d.err
+	}
+	if d.needClose {
+		// The last element we read was self-closing and
+		// we returned just the StartElement half.
+		// Return the EndElement half now.
+		d.needClose = false
+		return EndElement{d.toClose}, nil
+	}
+
+	b, ok := d.getc()
+	if !ok {
+		return nil, d.err
+	}
+
+	if b != '<' {
+		// Text section.
+		d.ungetc(b)
+		data := d.text(-1, false)
+		if data == nil {
+			return nil, d.err
+		}
+		return CharData(data), nil
+	}
+
+	if b, ok = d.mustgetc(); !ok {
+		return nil, d.err
+	}
+	switch b {
+	case '/':
+		// </: End element
+		var name Name
+		if name, ok = d.nsname(); !ok {
+			if d.err == nil {
+				d.err = d.syntaxError("expected element name after </")
+			}
+			return nil, d.err
+		}
+		d.space()
+		if b, ok = d.mustgetc(); !ok {
+			return nil, d.err
+		}
+		if b != '>' {
+			d.err = d.syntaxError("invalid characters between </" + name.Local + " and >")
+			return nil, d.err
+		}
+		return EndElement{name}, nil
+
+	case '?':
+		// <?: Processing instruction.
+		var target string
+		if target, ok = d.name(); !ok {
+			if d.err == nil {
+				d.err = d.syntaxError("expected target name after <?")
+			}
+			return nil, d.err
+		}
+		d.space()
+		d.buf.Reset()
+		var b0 byte
+		for {
+			if b, ok = d.mustgetc(); !ok {
+				return nil, d.err
+			}
+			d.buf.WriteByte(b)
+			if b0 == '?' && b == '>' {
+				break
+			}
+			b0 = b
+		}
+		data := d.buf.Bytes()
+		data = data[0 : len(data)-2] // chop ?>
+
+		if target == "xml" {
+			content := string(data)
+			ver := procInst("version", content)
+			if ver != "" && ver != "1.0" {
+				d.err = fmt.Errorf("xml: unsupported version %q; only version 1.0 is supported", ver)
+				return nil, d.err
+			}
+			enc := procInst("encoding", content)
+			if enc != "" && enc != "utf-8" && enc != "UTF-8" && !strings.EqualFold(enc, "utf-8") {
+				if d.CharsetReader == nil {
+					d.err = fmt.Errorf("xml: encoding %q declared but Decoder.CharsetReader is nil", enc)
+					return nil, d.err
+				}
+				newr, err := d.CharsetReader(enc, d.r.(io.Reader))
+				if err != nil {
+					d.err = fmt.Errorf("xml: opening charset %q: %v", enc, err)
+					return nil, d.err
+				}
+				if newr == nil {
+					panic("CharsetReader returned a nil Reader for charset " + enc)
+				}
+				d.switchToReader(newr)
+			}
+		}
+		return ProcInst{target, data}, nil
+
+	case '!':
+		// <!: Maybe comment, maybe CDATA.
+		if b, ok = d.mustgetc(); !ok {
+			return nil, d.err
+		}
+		switch b {
+		case '-': // <!-
+			// Probably <!-- for a comment.
+			if b, ok = d.mustgetc(); !ok {
+				return nil, d.err
+			}
+			if b != '-' {
+				d.err = d.syntaxError("invalid sequence <!- not part of <!--")
+				return nil, d.err
+			}
+			// Look for terminator.
+			d.buf.Reset()
+			var b0, b1 byte
+			for {
+				if b, ok = d.mustgetc(); !ok {
+					return nil, d.err
+				}
+				d.buf.WriteByte(b)
+				if b0 == '-' && b1 == '-' {
+					if b != '>' {
+						d.err = d.syntaxError(
+							`invalid sequence "--" not allowed in comments`)
+						return nil, d.err
+					}
+					break
+				}
+				b0, b1 = b1, b
+			}
+			data := d.buf.Bytes()
+			data = data[0 : len(data)-3] // chop -->
+			return Comment(data), nil
+
+		case '[': // <![
+			// Probably <![CDATA[.
+			for i := 0; i < 6; i++ {
+				if b, ok = d.mustgetc(); !ok {
+					return nil, d.err
+				}
+				if b != "CDATA["[i] {
+					d.err = d.syntaxError("invalid <![ sequence")
+					return nil, d.err
+				}
+			}
+			// Have <![CDATA[.  Read text until ]]>.
+			data := d.text(-1, true)
+			if data == nil {
+				return nil, d.err
+			}
+			return CharData(data), nil
+		}
+
+		// Probably a directive: <!DOCTYPE ...>, <!ENTITY ...>, etc.
+		// We don't care, but accumulate for caller. Quoted angle
+		// brackets do not count for nesting.
+		d.buf.Reset()
+		d.buf.WriteByte(b)
+		inquote := uint8(0)
+		depth := 0
+		for {
+			if b, ok = d.mustgetc(); !ok {
+				return nil, d.err
+			}
+			if inquote == 0 && b == '>' && depth == 0 {
+				break
+			}
+		HandleB:
+			d.buf.WriteByte(b)
+			switch {
+			case b == inquote:
+				inquote = 0
+
+			case inquote != 0:
+				// in quotes, no special action
+
+			case b == '\'' || b == '"':
+				inquote = b
+
+			case b == '>' && inquote == 0:
+				depth--
+
+			case b == '<' && inquote == 0:
+				// Look for <!-- to begin comment.
+				s := "!--"
+				for i := 0; i < len(s); i++ {
+					if b, ok = d.mustgetc(); !ok {
+						return nil, d.err
+					}
+					if b != s[i] {
+						for j := 0; j < i; j++ {
+							d.buf.WriteByte(s[j])
+						}
+						depth++
+						goto HandleB
+					}
+				}
+
+				// Remove < that was written above.
+				d.buf.Truncate(d.buf.Len() - 1)
+
+				// Look for terminator.
+				var b0, b1 byte
+				for {
+					if b, ok = d.mustgetc(); !ok {
+						return nil, d.err
+					}
+					if b0 == '-' && b1 == '-' && b == '>' {
+						break
+					}
+					b0, b1 = b1, b
+				}
+
+				// Replace the comment with a space in the returned Directive
+				// body, so that markup parts that were separated by the comment
+				// (like a "<" and a "!") don't get joined when re-encoding the
+				// Directive, taking new semantic meaning.
+				d.buf.WriteByte(' ')
+			}
+		}
+		return Directive(d.buf.Bytes()), nil
+	}
+
+	// Must be an open element like <a href="foo">
+	d.ungetc(b)
+
+	var (
+		name  Name
+		empty bool
+		attr  []Attr
+	)
+	if name, ok = d.nsname(); !ok {
+		if d.err == nil {
+			d.err = d.syntaxError("expected element name after <")
+		}
+		return nil, d.err
+	}
+
+	attr = []Attr{}
+	for {
+		d.space()
+		if b, ok = d.mustgetc(); !ok {
+			return nil, d.err
+		}
+		if b == '/' {
+			empty = true
+			if b, ok = d.mustgetc(); !ok {
+				return nil, d.err
+			}
+			if b != '>' {
+				d.err = d.syntaxError("expected /> in element")
+				return nil, d.err
+			}
+			break
+		}
+		if b == '>' {
+			break
+		}
+		d.ungetc(b)
+
+		a := Attr{}
+		if a.Name, ok = d.nsname(); !ok {
+			if d.err == nil {
+				d.err = d.syntaxError("expected attribute name in element")
+			}
+			return nil, d.err
+		}
+		d.space()
+		if b, ok = d.mustgetc(); !ok {
+			return nil, d.err
+		}
+		if b != '=' {
+			if d.Strict {
+				d.err = d.syntaxError("attribute name without = in element")
+				return nil, d.err
+			}
+			d.ungetc(b)
+			a.Value = a.Name.Local
+		} else {
+			d.space()
+			data := d.attrval()
+			if data == nil {
+				return nil, d.err
+			}
+			a.Value = string(data)
+		}
+		attr = append(attr, a)
+	}
+	if empty {
+		d.needClose = true
+		d.toClose = name
+	}
+	return StartElement{name, attr}, nil
+}
+
+func (d *Decoder) attrval() []byte {
+	b, ok := d.mustgetc()
+	if !ok {
+		return nil
+	}
+	// Handle quoted attribute values
+	if b == '"' || b == '\'' {
+		return d.text(int(b), false)
+	}
+	// Handle unquoted attribute values for strict parsers
+	if d.Strict {
+		d.err = d.syntaxError("unquoted or missing attribute value in element")
+		return nil
+	}
+	// Handle unquoted attribute values for unstrict parsers
+	d.ungetc(b)
+	d.buf.Reset()
+	for {
+		b, ok = d.mustgetc()
+		if !ok {
+			return nil
+		}
+		// https://www.w3.org/TR/REC-html40/intro/sgmltut.html#h-3.2.2
+		if 'a' <= b && b <= 'z' || 'A' <= b && b <= 'Z' ||
+			'0' <= b && b <= '9' || b == '_' || b == ':' || b == '-' {
+			d.buf.WriteByte(b)
+		} else {
+			d.ungetc(b)
+			break
+		}
+	}
+	return d.buf.Bytes()
+}
+
+// Skip spaces if any
+func (d *Decoder) space() {
+	for {
+		b, ok := d.getc()
+		if !ok {
+			return
+		}
+		switch b {
+		case ' ', '\r', '\n', '\t':
+		default:
+			d.ungetc(b)
+			return
+		}
+	}
+}
+
+// Read a single byte.
+// If there is no byte to read, return ok==false
+// and leave the error in d.err.
+// Maintain line number.
+func (d *Decoder) getc() (b byte, ok bool) {
+	if d.err != nil {
+		return 0, false
+	}
+	if d.nextByte >= 0 {
+		b = byte(d.nextByte)
+		d.nextByte = -1
+	} else {
+		b, d.err = d.r.ReadByte()
+		if d.err != nil {
+			return 0, false
+		}
+		if d.saved != nil {
+			d.saved.WriteByte(b)
+		}
+	}
+	if b == '\n' {
+		d.line++
+	}
+	d.offset++
+	return b, true
+}
+
+// InputOffset returns the input stream byte offset of the current decoder position.
+// The offset gives the location of the end of the most recently returned token
+// and the beginning of the next token.
+func (d *Decoder) InputOffset() int64 {
+	return d.offset
+}
+
+// Return saved offset.
+// If we did ungetc (nextByte >= 0), have to back up one.
+func (d *Decoder) savedOffset() int {
+	n := d.saved.Len()
+	if d.nextByte >= 0 {
+		n--
+	}
+	return n
+}
+
+// Must read a single byte.
+// If there is no byte to read,
+// set d.err to SyntaxError("unexpected EOF")
+// and return ok==false
+func (d *Decoder) mustgetc() (b byte, ok bool) {
+	if b, ok = d.getc(); !ok {
+		if d.err == io.EOF {
+			d.err = d.syntaxError("unexpected EOF")
+		}
+	}
+	return
+}
+
+// Unread a single byte.
+func (d *Decoder) ungetc(b byte) {
+	if b == '\n' {
+		d.line--
+	}
+	d.nextByte = int(b)
+	d.offset--
+}
+
+var entity = map[string]rune{
+	"lt":   '<',
+	"gt":   '>',
+	"amp":  '&',
+	"apos": '\'',
+	"quot": '"',
+}
+
+// Read plain text section (XML calls it character data).
+// If quote >= 0, we are in a quoted string and need to find the matching quote.
+// If cdata == true, we are in a <![CDATA[ section and need to find ]]>.
+// On failure return nil and leave the error in d.err.
+func (d *Decoder) text(quote int, cdata bool) []byte {
+	var b0, b1 byte
+	var trunc int
+	d.buf.Reset()
+Input:
+	for {
+		b, ok := d.getc()
+		if !ok {
+			if cdata {
+				if d.err == io.EOF {
+					d.err = d.syntaxError("unexpected EOF in CDATA section")
+				}
+				return nil
+			}
+			break Input
+		}
+
+		// <![CDATA[ section ends with ]]>.
+		// It is an error for ]]> to appear in ordinary text.
+		if b0 == ']' && b1 == ']' && b == '>' {
+			if cdata {
+				trunc = 2
+				break Input
+			}
+			d.err = d.syntaxError("unescaped ]]> not in CDATA section")
+			return nil
+		}
+
+		// Stop reading text if we see a <.
+		if b == '<' && !cdata {
+			if quote >= 0 {
+				d.err = d.syntaxError("unescaped < inside quoted string")
+				return nil
+			}
+			d.ungetc('<')
+			break Input
+		}
+		if quote >= 0 && b == byte(quote) {
+			break Input
+		}
+		if b == '&' && !cdata {
+			// Read escaped character expression up to semicolon.
+			// XML in all its glory allows a document to define and use
+			// its own character names with <!ENTITY ...> directives.
+			// Parsers are required to recognize lt, gt, amp, apos, and quot
+			// even if they have not been declared.
+			before := d.buf.Len()
+			d.buf.WriteByte('&')
+			var ok bool
+			var text string
+			var haveText bool
+			if b, ok = d.mustgetc(); !ok {
+				return nil
+			}
+			if b == '#' {
+				d.buf.WriteByte(b)
+				if b, ok = d.mustgetc(); !ok {
+					return nil
+				}
+				base := 10
+				if b == 'x' {
+					base = 16
+					d.buf.WriteByte(b)
+					if b, ok = d.mustgetc(); !ok {
+						return nil
+					}
+				}
+				start := d.buf.Len()
+				for '0' <= b && b <= '9' ||
+					base == 16 && 'a' <= b && b <= 'f' ||
+					base == 16 && 'A' <= b && b <= 'F' {
+					d.buf.WriteByte(b)
+					if b, ok = d.mustgetc(); !ok {
+						return nil
+					}
+				}
+				if b != ';' {
+					d.ungetc(b)
+				} else {
+					s := string(d.buf.Bytes()[start:])
+					d.buf.WriteByte(';')
+					n, err := strconv.ParseUint(s, base, 64)
+					if err == nil && n <= unicode.MaxRune {
+						text = string(rune(n))
+						haveText = true
+					}
+				}
+			} else {
+				d.ungetc(b)
+				if !d.readName() {
+					if d.err != nil {
+						return nil
+					}
+				}
+				if b, ok = d.mustgetc(); !ok {
+					return nil
+				}
+				if b != ';' {
+					d.ungetc(b)
+				} else {
+					name := d.buf.Bytes()[before+1:]
+					d.buf.WriteByte(';')
+					if isName(name) {
+						s := string(name)
+						if r, ok := entity[s]; ok {
+							text = string(r)
+							haveText = true
+						} else if d.Entity != nil {
+							text, haveText = d.Entity[s]
+						}
+					}
+				}
+			}
+
+			if haveText {
+				d.buf.Truncate(before)
+				d.buf.Write([]byte(text))
+				b0, b1 = 0, 0
+				continue Input
+			}
+			if !d.Strict {
+				b0, b1 = 0, 0
+				continue Input
+			}
+			ent := string(d.buf.Bytes()[before:])
+			if ent[len(ent)-1] != ';' {
+				ent += " (no semicolon)"
+			}
+			d.err = d.syntaxError("invalid character entity " + ent)
+			return nil
+		}
+
+		// We must rewrite unescaped \r and \r\n into \n.
+		if b == '\r' {
+			d.buf.WriteByte('\n')
+		} else if b1 == '\r' && b == '\n' {
+			// Skip \r\n--we already wrote \n.
+		} else {
+			d.buf.WriteByte(b)
+		}
+
+		b0, b1 = b1, b
+	}
+	data := d.buf.Bytes()
+	data = data[0 : len(data)-trunc]
+
+	// Inspect each rune for being a disallowed character.
+	buf := data
+	for len(buf) > 0 {
+		r, size := utf8.DecodeRune(buf)
+		if r == utf8.RuneError && size == 1 {
+			d.err = d.syntaxError("invalid UTF-8")
+			return nil
+		}
+		buf = buf[size:]
+		if !isInCharacterRange(r) {
+			d.err = d.syntaxError(fmt.Sprintf("illegal character code %U", r))
+			return nil
+		}
+	}
+
+	return data
+}
+
+// Decide whether the given rune is in the XML Character Range, per
+// the Char production of https://www.xml.com/axml/testaxml.htm,
+// Section 2.2 Characters.
+func isInCharacterRange(r rune) (inrange bool) {
+	return r == 0x09 ||
+		r == 0x0A ||
+		r == 0x0D ||
+		r >= 0x20 && r <= 0xD7FF ||
+		r >= 0xE000 && r <= 0xFFFD ||
+		r >= 0x10000 && r <= 0x10FFFF
+}
+
+// Get name space name: name with a : stuck in the middle.
+// The part before the : is the name space identifier.
+func (d *Decoder) nsname() (name Name, ok bool) {
+	s, ok := d.name()
+	if !ok {
+		return
+	}
+	if strings.Count(s, ":") > 1 {
+		name.Local = s
+	} else if space, local, ok := strings.Cut(s, ":"); !ok || space == "" || local == "" {
+		name.Local = s
+	} else {
+		name.Space = space
+		name.Local = local
+	}
+	return name, true
+}
+
+// Get name: /first(first|second)*/
+// Do not set d.err if the name is missing (unless unexpected EOF is received):
+// let the caller provide better context.
+func (d *Decoder) name() (s string, ok bool) {
+	d.buf.Reset()
+	if !d.readName() {
+		return "", false
+	}
+
+	// Now we check the characters.
+	b := d.buf.Bytes()
+	if !isName(b) {
+		d.err = d.syntaxError("invalid XML name: " + string(b))
+		return "", false
+	}
+	return string(b), true
+}
+
+// Read a name and append its bytes to d.buf.
+// The name is delimited by any single-byte character not valid in names.
+// All multi-byte characters are accepted; the caller must check their validity.
+func (d *Decoder) readName() (ok bool) {
+	var b byte
+	if b, ok = d.mustgetc(); !ok {
+		return
+	}
+	if b < utf8.RuneSelf && !isNameByte(b) {
+		d.ungetc(b)
+		return false
+	}
+	d.buf.WriteByte(b)
+
+	for {
+		if b, ok = d.mustgetc(); !ok {
+			return
+		}
+		if b < utf8.RuneSelf && !isNameByte(b) {
+			d.ungetc(b)
+			break
+		}
+		d.buf.WriteByte(b)
+	}
+	return true
+}
+
+func isNameByte(c byte) bool {
+	return 'A' <= c && c <= 'Z' ||
+		'a' <= c && c <= 'z' ||
+		'0' <= c && c <= '9' ||
+		c == '_' || c == ':' || c == '.' || c == '-'
+}
+
+func isName(s []byte) bool {
+	if len(s) == 0 {
+		return false
+	}
+	c, n := utf8.DecodeRune(s)
+	if c == utf8.RuneError && n == 1 {
+		return false
+	}
+	if !unicode.Is(first, c) {
+		return false
+	}
+	for n < len(s) {
+		s = s[n:]
+		c, n = utf8.DecodeRune(s)
+		if c == utf8.RuneError && n == 1 {
+			return false
+		}
+		if !unicode.Is(first, c) && !unicode.Is(second, c) {
+			return false
+		}
+	}
+	return true
+}
+
+func isNameString(s string) bool {
+	if len(s) == 0 {
+		return false
+	}
+	c, n := utf8.DecodeRuneInString(s)
+	if c == utf8.RuneError && n == 1 {
+		return false
+	}
+	if !unicode.Is(first, c) {
+		return false
+	}
+	for n < len(s) {
+		s = s[n:]
+		c, n = utf8.DecodeRuneInString(s)
+		if c == utf8.RuneError && n == 1 {
+			return false
+		}
+		if !unicode.Is(first, c) && !unicode.Is(second, c) {
+			return false
+		}
+	}
+	return true
+}
+
+// These tables were generated by cut and paste from Appendix B of
+// the XML spec at https://www.xml.com/axml/testaxml.htm
+// and then reformatting. First corresponds to (Letter | '_' | ':')
+// and second corresponds to NameChar.
+
+var first = &unicode.RangeTable{
+	R16: []unicode.Range16{
+		{0x003A, 0x003A, 1},
+		{0x0041, 0x005A, 1},
+		{0x005F, 0x005F, 1},
+		{0x0061, 0x007A, 1},
+		{0x00C0, 0x00D6, 1},
+		{0x00D8, 0x00F6, 1},
+		{0x00F8, 0x00FF, 1},
+		{0x0100, 0x0131, 1},
+		{0x0134, 0x013E, 1},
+		{0x0141, 0x0148, 1},
+		{0x014A, 0x017E, 1},
+		{0x0180, 0x01C3, 1},
+		{0x01CD, 0x01F0, 1},
+		{0x01F4, 0x01F5, 1},
+		{0x01FA, 0x0217, 1},
+		{0x0250, 0x02A8, 1},
+		{0x02BB, 0x02C1, 1},
+		{0x0386, 0x0386, 1},
+		{0x0388, 0x038A, 1},
+		{0x038C, 0x038C, 1},
+		{0x038E, 0x03A1, 1},
+		{0x03A3, 0x03CE, 1},
+		{0x03D0, 0x03D6, 1},
+		{0x03DA, 0x03E0, 2},
+		{0x03E2, 0x03F3, 1},
+		{0x0401, 0x040C, 1},
+		{0x040E, 0x044F, 1},
+		{0x0451, 0x045C, 1},
+		{0x045E, 0x0481, 1},
+		{0x0490, 0x04C4, 1},
+		{0x04C7, 0x04C8, 1},
+		{0x04CB, 0x04CC, 1},
+		{0x04D0, 0x04EB, 1},
+		{0x04EE, 0x04F5, 1},
+		{0x04F8, 0x04F9, 1},
+		{0x0531, 0x0556, 1},
+		{0x0559, 0x0559, 1},
+		{0x0561, 0x0586, 1},
+		{0x05D0, 0x05EA, 1},
+		{0x05F0, 0x05F2, 1},
+		{0x0621, 0x063A, 1},
+		{0x0641, 0x064A, 1},
+		{0x0671, 0x06B7, 1},
+		{0x06BA, 0x06BE, 1},
+		{0x06C0, 0x06CE, 1},
+		{0x06D0, 0x06D3, 1},
+		{0x06D5, 0x06D5, 1},
+		{0x06E5, 0x06E6, 1},
+		{0x0905, 0x0939, 1},
+		{0x093D, 0x093D, 1},
+		{0x0958, 0x0961, 1},
+		{0x0985, 0x098C, 1},
+		{0x098F, 0x0990, 1},
+		{0x0993, 0x09A8, 1},
+		{0x09AA, 0x09B0, 1},
+		{0x09B2, 0x09B2, 1},
+		{0x09B6, 0x09B9, 1},
+		{0x09DC, 0x09DD, 1},
+		{0x09DF, 0x09E1, 1},
+		{0x09F0, 0x09F1, 1},
+		{0x0A05, 0x0A0A, 1},
+		{0x0A0F, 0x0A10, 1},
+		{0x0A13, 0x0A28, 1},
+		{0x0A2A, 0x0A30, 1},
+		{0x0A32, 0x0A33, 1},
+		{0x0A35, 0x0A36, 1},
+		{0x0A38, 0x0A39, 1},
+		{0x0A59, 0x0A5C, 1},
+		{0x0A5E, 0x0A5E, 1},
+		{0x0A72, 0x0A74, 1},
+		{0x0A85, 0x0A8B, 1},
+		{0x0A8D, 0x0A8D, 1},
+		{0x0A8F, 0x0A91, 1},
+		{0x0A93, 0x0AA8, 1},
+		{0x0AAA, 0x0AB0, 1},
+		{0x0AB2, 0x0AB3, 1},
+		{0x0AB5, 0x0AB9, 1},
+		{0x0ABD, 0x0AE0, 0x23},
+		{0x0B05, 0x0B0C, 1},
+		{0x0B0F, 0x0B10, 1},
+		{0x0B13, 0x0B28, 1},
+		{0x0B2A, 0x0B30, 1},
+		{0x0B32, 0x0B33, 1},
+		{0x0B36, 0x0B39, 1},
+		{0x0B3D, 0x0B3D, 1},
+		{0x0B5C, 0x0B5D, 1},
+		{0x0B5F, 0x0B61, 1},
+		{0x0B85, 0x0B8A, 1},
+		{0x0B8E, 0x0B90, 1},
+		{0x0B92, 0x0B95, 1},
+		{0x0B99, 0x0B9A, 1},
+		{0x0B9C, 0x0B9C, 1},
+		{0x0B9E, 0x0B9F, 1},
+		{0x0BA3, 0x0BA4, 1},
+		{0x0BA8, 0x0BAA, 1},
+		{0x0BAE, 0x0BB5, 1},
+		{0x0BB7, 0x0BB9, 1},
+		{0x0C05, 0x0C0C, 1},
+		{0x0C0E, 0x0C10, 1},
+		{0x0C12, 0x0C28, 1},
+		{0x0C2A, 0x0C33, 1},
+		{0x0C35, 0x0C39, 1},
+		{0x0C60, 0x0C61, 1},
+		{0x0C85, 0x0C8C, 1},
+		{0x0C8E, 0x0C90, 1},
+		{0x0C92, 0x0CA8, 1},
+		{0x0CAA, 0x0CB3, 1},
+		{0x0CB5, 0x0CB9, 1},
+		{0x0CDE, 0x0CDE, 1},
+		{0x0CE0, 0x0CE1, 1},
+		{0x0D05, 0x0D0C, 1},
+		{0x0D0E, 0x0D10, 1},
+		{0x0D12, 0x0D28, 1},
+		{0x0D2A, 0x0D39, 1},
+		{0x0D60, 0x0D61, 1},
+		{0x0E01, 0x0E2E, 1},
+		{0x0E30, 0x0E30, 1},
+		{0x0E32, 0x0E33, 1},
+		{0x0E40, 0x0E45, 1},
+		{0x0E81, 0x0E82, 1},
+		{0x0E84, 0x0E84, 1},
+		{0x0E87, 0x0E88, 1},
+		{0x0E8A, 0x0E8D, 3},
+		{0x0E94, 0x0E97, 1},
+		{0x0E99, 0x0E9F, 1},
+		{0x0EA1, 0x0EA3, 1},
+		{0x0EA5, 0x0EA7, 2},
+		{0x0EAA, 0x0EAB, 1},
+		{0x0EAD, 0x0EAE, 1},
+		{0x0EB0, 0x0EB0, 1},
+		{0x0EB2, 0x0EB3, 1},
+		{0x0EBD, 0x0EBD, 1},
+		{0x0EC0, 0x0EC4, 1},
+		{0x0F40, 0x0F47, 1},
+		{0x0F49, 0x0F69, 1},
+		{0x10A0, 0x10C5, 1},
+		{0x10D0, 0x10F6, 1},
+		{0x1100, 0x1100, 1},
+		{0x1102, 0x1103, 1},
+		{0x1105, 0x1107, 1},
+		{0x1109, 0x1109, 1},
+		{0x110B, 0x110C, 1},
+		{0x110E, 0x1112, 1},
+		{0x113C, 0x1140, 2},
+		{0x114C, 0x1150, 2},
+		{0x1154, 0x1155, 1},
+		{0x1159, 0x1159, 1},
+		{0x115F, 0x1161, 1},
+		{0x1163, 0x1169, 2},
+		{0x116D, 0x116E, 1},
+		{0x1172, 0x1173, 1},
+		{0x1175, 0x119E, 0x119E - 0x1175},
+		{0x11A8, 0x11AB, 0x11AB - 0x11A8},
+		{0x11AE, 0x11AF, 1},
+		{0x11B7, 0x11B8, 1},
+		{0x11BA, 0x11BA, 1},
+		{0x11BC, 0x11C2, 1},
+		{0x11EB, 0x11F0, 0x11F0 - 0x11EB},
+		{0x11F9, 0x11F9, 1},
+		{0x1E00, 0x1E9B, 1},
+		{0x1EA0, 0x1EF9, 1},
+		{0x1F00, 0x1F15, 1},
+		{0x1F18, 0x1F1D, 1},
+		{0x1F20, 0x1F45, 1},
+		{0x1F48, 0x1F4D, 1},
+		{0x1F50, 0x1F57, 1},
+		{0x1F59, 0x1F5B, 0x1F5B - 0x1F59},
+		{0x1F5D, 0x1F5D, 1},
+		{0x1F5F, 0x1F7D, 1},
+		{0x1F80, 0x1FB4, 1},
+		{0x1FB6, 0x1FBC, 1},
+		{0x1FBE, 0x1FBE, 1},
+		{0x1FC2, 0x1FC4, 1},
+		{0x1FC6, 0x1FCC, 1},
+		{0x1FD0, 0x1FD3, 1},
+		{0x1FD6, 0x1FDB, 1},
+		{0x1FE0, 0x1FEC, 1},
+		{0x1FF2, 0x1FF4, 1},
+		{0x1FF6, 0x1FFC, 1},
+		{0x2126, 0x2126, 1},
+		{0x212A, 0x212B, 1},
+		{0x212E, 0x212E, 1},
+		{0x2180, 0x2182, 1},
+		{0x3007, 0x3007, 1},
+		{0x3021, 0x3029, 1},
+		{0x3041, 0x3094, 1},
+		{0x30A1, 0x30FA, 1},
+		{0x3105, 0x312C, 1},
+		{0x4E00, 0x9FA5, 1},
+		{0xAC00, 0xD7A3, 1},
+	},
+}
+
+var second = &unicode.RangeTable{
+	R16: []unicode.Range16{
+		{0x002D, 0x002E, 1},
+		{0x0030, 0x0039, 1},
+		{0x00B7, 0x00B7, 1},
+		{0x02D0, 0x02D1, 1},
+		{0x0300, 0x0345, 1},
+		{0x0360, 0x0361, 1},
+		{0x0387, 0x0387, 1},
+		{0x0483, 0x0486, 1},
+		{0x0591, 0x05A1, 1},
+		{0x05A3, 0x05B9, 1},
+		{0x05BB, 0x05BD, 1},
+		{0x05BF, 0x05BF, 1},
+		{0x05C1, 0x05C2, 1},
+		{0x05C4, 0x0640, 0x0640 - 0x05C4},
+		{0x064B, 0x0652, 1},
+		{0x0660, 0x0669, 1},
+		{0x0670, 0x0670, 1},
+		{0x06D6, 0x06DC, 1},
+		{0x06DD, 0x06DF, 1},
+		{0x06E0, 0x06E4, 1},
+		{0x06E7, 0x06E8, 1},
+		{0x06EA, 0x06ED, 1},
+		{0x06F0, 0x06F9, 1},
+		{0x0901, 0x0903, 1},
+		{0x093C, 0x093C, 1},
+		{0x093E, 0x094C, 1},
+		{0x094D, 0x094D, 1},
+		{0x0951, 0x0954, 1},
+		{0x0962, 0x0963, 1},
+		{0x0966, 0x096F, 1},
+		{0x0981, 0x0983, 1},
+		{0x09BC, 0x09BC, 1},
+		{0x09BE, 0x09BF, 1},
+		{0x09C0, 0x09C4, 1},
+		{0x09C7, 0x09C8, 1},
+		{0x09CB, 0x09CD, 1},
+		{0x09D7, 0x09D7, 1},
+		{0x09E2, 0x09E3, 1},
+		{0x09E6, 0x09EF, 1},
+		{0x0A02, 0x0A3C, 0x3A},
+		{0x0A3E, 0x0A3F, 1},
+		{0x0A40, 0x0A42, 1},
+		{0x0A47, 0x0A48, 1},
+		{0x0A4B, 0x0A4D, 1},
+		{0x0A66, 0x0A6F, 1},
+		{0x0A70, 0x0A71, 1},
+		{0x0A81, 0x0A83, 1},
+		{0x0ABC, 0x0ABC, 1},
+		{0x0ABE, 0x0AC5, 1},
+		{0x0AC7, 0x0AC9, 1},
+		{0x0ACB, 0x0ACD, 1},
+		{0x0AE6, 0x0AEF, 1},
+		{0x0B01, 0x0B03, 1},
+		{0x0B3C, 0x0B3C, 1},
+		{0x0B3E, 0x0B43, 1},
+		{0x0B47, 0x0B48, 1},
+		{0x0B4B, 0x0B4D, 1},
+		{0x0B56, 0x0B57, 1},
+		{0x0B66, 0x0B6F, 1},
+		{0x0B82, 0x0B83, 1},
+		{0x0BBE, 0x0BC2, 1},
+		{0x0BC6, 0x0BC8, 1},
+		{0x0BCA, 0x0BCD, 1},
+		{0x0BD7, 0x0BD7, 1},
+		{0x0BE7, 0x0BEF, 1},
+		{0x0C01, 0x0C03, 1},
+		{0x0C3E, 0x0C44, 1},
+		{0x0C46, 0x0C48, 1},
+		{0x0C4A, 0x0C4D, 1},
+		{0x0C55, 0x0C56, 1},
+		{0x0C66, 0x0C6F, 1},
+		{0x0C82, 0x0C83, 1},
+		{0x0CBE, 0x0CC4, 1},
+		{0x0CC6, 0x0CC8, 1},
+		{0x0CCA, 0x0CCD, 1},
+		{0x0CD5, 0x0CD6, 1},
+		{0x0CE6, 0x0CEF, 1},
+		{0x0D02, 0x0D03, 1},
+		{0x0D3E, 0x0D43, 1},
+		{0x0D46, 0x0D48, 1},
+		{0x0D4A, 0x0D4D, 1},
+		{0x0D57, 0x0D57, 1},
+		{0x0D66, 0x0D6F, 1},
+		{0x0E31, 0x0E31, 1},
+		{0x0E34, 0x0E3A, 1},
+		{0x0E46, 0x0E46, 1},
+		{0x0E47, 0x0E4E, 1},
+		{0x0E50, 0x0E59, 1},
+		{0x0EB1, 0x0EB1, 1},
+		{0x0EB4, 0x0EB9, 1},
+		{0x0EBB, 0x0EBC, 1},
+		{0x0EC6, 0x0EC6, 1},
+		{0x0EC8, 0x0ECD, 1},
+		{0x0ED0, 0x0ED9, 1},
+		{0x0F18, 0x0F19, 1},
+		{0x0F20, 0x0F29, 1},
+		{0x0F35, 0x0F39, 2},
+		{0x0F3E, 0x0F3F, 1},
+		{0x0F71, 0x0F84, 1},
+		{0x0F86, 0x0F8B, 1},
+		{0x0F90, 0x0F95, 1},
+		{0x0F97, 0x0F97, 1},
+		{0x0F99, 0x0FAD, 1},
+		{0x0FB1, 0x0FB7, 1},
+		{0x0FB9, 0x0FB9, 1},
+		{0x20D0, 0x20DC, 1},
+		{0x20E1, 0x3005, 0x3005 - 0x20E1},
+		{0x302A, 0x302F, 1},
+		{0x3031, 0x3035, 1},
+		{0x3099, 0x309A, 1},
+		{0x309D, 0x309E, 1},
+		{0x30FC, 0x30FE, 1},
+	},
+}
+
+// HTMLEntity is an entity map containing translations for the
+// standard HTML entity characters.
+//
+// See the Decoder.Strict and Decoder.Entity fields' documentation.
+var HTMLEntity map[string]string = htmlEntity
+
+var htmlEntity = map[string]string{
+	/*
+		hget http://www.w3.org/TR/html4/sgml/entities.html |
+		ssam '
+			,y /\&gt;/ x/\&lt;(.|\n)+/ s/\n/ /g
+			,x v/^\&lt;!ENTITY/d
+			,s/\&lt;!ENTITY ([^ ]+) .*U\+([0-9A-F][0-9A-F][0-9A-F][0-9A-F]) .+/	"\1": "\\u\2",/g
+		'
+	*/
+	"nbsp":     "\u00A0",
+	"iexcl":    "\u00A1",
+	"cent":     "\u00A2",
+	"pound":    "\u00A3",
+	"curren":   "\u00A4",
+	"yen":      "\u00A5",
+	"brvbar":   "\u00A6",
+	"sect":     "\u00A7",
+	"uml":      "\u00A8",
+	"copy":     "\u00A9",
+	"ordf":     "\u00AA",
+	"laquo":    "\u00AB",
+	"not":      "\u00AC",
+	"shy":      "\u00AD",
+	"reg":      "\u00AE",
+	"macr":     "\u00AF",
+	"deg":      "\u00B0",
+	"plusmn":   "\u00B1",
+	"sup2":     "\u00B2",
+	"sup3":     "\u00B3",
+	"acute":    "\u00B4",
+	"micro":    "\u00B5",
+	"para":     "\u00B6",
+	"middot":   "\u00B7",
+	"cedil":    "\u00B8",
+	"sup1":     "\u00B9",
+	"ordm":     "\u00BA",
+	"raquo":    "\u00BB",
+	"frac14":   "\u00BC",
+	"frac12":   "\u00BD",
+	"frac34":   "\u00BE",
+	"iquest":   "\u00BF",
+	"Agrave":   "\u00C0",
+	"Aacute":   "\u00C1",
+	"Acirc":    "\u00C2",
+	"Atilde":   "\u00C3",
+	"Auml":     "\u00C4",
+	"Aring":    "\u00C5",
+	"AElig":    "\u00C6",
+	"Ccedil":   "\u00C7",
+	"Egrave":   "\u00C8",
+	"Eacute":   "\u00C9",
+	"Ecirc":    "\u00CA",
+	"Euml":     "\u00CB",
+	"Igrave":   "\u00CC",
+	"Iacute":   "\u00CD",
+	"Icirc":    "\u00CE",
+	"Iuml":     "\u00CF",
+	"ETH":      "\u00D0",
+	"Ntilde":   "\u00D1",
+	"Ograve":   "\u00D2",
+	"Oacute":   "\u00D3",
+	"Ocirc":    "\u00D4",
+	"Otilde":   "\u00D5",
+	"Ouml":     "\u00D6",
+	"times":    "\u00D7",
+	"Oslash":   "\u00D8",
+	"Ugrave":   "\u00D9",
+	"Uacute":   "\u00DA",
+	"Ucirc":    "\u00DB",
+	"Uuml":     "\u00DC",
+	"Yacute":   "\u00DD",
+	"THORN":    "\u00DE",
+	"szlig":    "\u00DF",
+	"agrave":   "\u00E0",
+	"aacute":   "\u00E1",
+	"acirc":    "\u00E2",
+	"atilde":   "\u00E3",
+	"auml":     "\u00E4",
+	"aring":    "\u00E5",
+	"aelig":    "\u00E6",
+	"ccedil":   "\u00E7",
+	"egrave":   "\u00E8",
+	"eacute":   "\u00E9",
+	"ecirc":    "\u00EA",
+	"euml":     "\u00EB",
+	"igrave":   "\u00EC",
+	"iacute":   "\u00ED",
+	"icirc":    "\u00EE",
+	"iuml":     "\u00EF",
+	"eth":      "\u00F0",
+	"ntilde":   "\u00F1",
+	"ograve":   "\u00F2",
+	"oacute":   "\u00F3",
+	"ocirc":    "\u00F4",
+	"otilde":   "\u00F5",
+	"ouml":     "\u00F6",
+	"divide":   "\u00F7",
+	"oslash":   "\u00F8",
+	"ugrave":   "\u00F9",
+	"uacute":   "\u00FA",
+	"ucirc":    "\u00FB",
+	"uuml":     "\u00FC",
+	"yacute":   "\u00FD",
+	"thorn":    "\u00FE",
+	"yuml":     "\u00FF",
+	"fnof":     "\u0192",
+	"Alpha":    "\u0391",
+	"Beta":     "\u0392",
+	"Gamma":    "\u0393",
+	"Delta":    "\u0394",
+	"Epsilon":  "\u0395",
+	"Zeta":     "\u0396",
+	"Eta":      "\u0397",
+	"Theta":    "\u0398",
+	"Iota":     "\u0399",
+	"Kappa":    "\u039A",
+	"Lambda":   "\u039B",
+	"Mu":       "\u039C",
+	"Nu":       "\u039D",
+	"Xi":       "\u039E",
+	"Omicron":  "\u039F",
+	"Pi":       "\u03A0",
+	"Rho":      "\u03A1",
+	"Sigma":    "\u03A3",
+	"Tau":      "\u03A4",
+	"Upsilon":  "\u03A5",
+	"Phi":      "\u03A6",
+	"Chi":      "\u03A7",
+	"Psi":      "\u03A8",
+	"Omega":    "\u03A9",
+	"alpha":    "\u03B1",
+	"beta":     "\u03B2",
+	"gamma":    "\u03B3",
+	"delta":    "\u03B4",
+	"epsilon":  "\u03B5",
+	"zeta":     "\u03B6",
+	"eta":      "\u03B7",
+	"theta":    "\u03B8",
+	"iota":     "\u03B9",
+	"kappa":    "\u03BA",
+	"lambda":   "\u03BB",
+	"mu":       "\u03BC",
+	"nu":       "\u03BD",
+	"xi":       "\u03BE",
+	"omicron":  "\u03BF",
+	"pi":       "\u03C0",
+	"rho":      "\u03C1",
+	"sigmaf":   "\u03C2",
+	"sigma":    "\u03C3",
+	"tau":      "\u03C4",
+	"upsilon":  "\u03C5",
+	"phi":      "\u03C6",
+	"chi":      "\u03C7",
+	"psi":      "\u03C8",
+	"omega":    "\u03C9",
+	"thetasym": "\u03D1",
+	"upsih":    "\u03D2",
+	"piv":      "\u03D6",
+	"bull":     "\u2022",
+	"hellip":   "\u2026",
+	"prime":    "\u2032",
+	"Prime":    "\u2033",
+	"oline":    "\u203E",
+	"frasl":    "\u2044",
+	"weierp":   "\u2118",
+	"image":    "\u2111",
+	"real":     "\u211C",
+	"trade":    "\u2122",
+	"alefsym":  "\u2135",
+	"larr":     "\u2190",
+	"uarr":     "\u2191",
+	"rarr":     "\u2192",
+	"darr":     "\u2193",
+	"harr":     "\u2194",
+	"crarr":    "\u21B5",
+	"lArr":     "\u21D0",
+	"uArr":     "\u21D1",
+	"rArr":     "\u21D2",
+	"dArr":     "\u21D3",
+	"hArr":     "\u21D4",
+	"forall":   "\u2200",
+	"part":     "\u2202",
+	"exist":    "\u2203",
+	"empty":    "\u2205",
+	"nabla":    "\u2207",
+	"isin":     "\u2208",
+	"notin":    "\u2209",
+	"ni":       "\u220B",
+	"prod":     "\u220F",
+	"sum":      "\u2211",
+	"minus":    "\u2212",
+	"lowast":   "\u2217",
+	"radic":    "\u221A",
+	"prop":     "\u221D",
+	"infin":    "\u221E",
+	"ang":      "\u2220",
+	"and":      "\u2227",
+	"or":       "\u2228",
+	"cap":      "\u2229",
+	"cup":      "\u222A",
+	"int":      "\u222B",
+	"there4":   "\u2234",
+	"sim":      "\u223C",
+	"cong":     "\u2245",
+	"asymp":    "\u2248",
+	"ne":       "\u2260",
+	"equiv":    "\u2261",
+	"le":       "\u2264",
+	"ge":       "\u2265",
+	"sub":      "\u2282",
+	"sup":      "\u2283",
+	"nsub":     "\u2284",
+	"sube":     "\u2286",
+	"supe":     "\u2287",
+	"oplus":    "\u2295",
+	"otimes":   "\u2297",
+	"perp":     "\u22A5",
+	"sdot":     "\u22C5",
+	"lceil":    "\u2308",
+	"rceil":    "\u2309",
+	"lfloor":   "\u230A",
+	"rfloor":   "\u230B",
+	"lang":     "\u2329",
+	"rang":     "\u232A",
+	"loz":      "\u25CA",
+	"spades":   "\u2660",
+	"clubs":    "\u2663",
+	"hearts":   "\u2665",
+	"diams":    "\u2666",
+	"quot":     "\u0022",
+	"amp":      "\u0026",
+	"lt":       "\u003C",
+	"gt":       "\u003E",
+	"OElig":    "\u0152",
+	"oelig":    "\u0153",
+	"Scaron":   "\u0160",
+	"scaron":   "\u0161",
+	"Yuml":     "\u0178",
+	"circ":     "\u02C6",
+	"tilde":    "\u02DC",
+	"ensp":     "\u2002",
+	"emsp":     "\u2003",
+	"thinsp":   "\u2009",
+	"zwnj":     "\u200C",
+	"zwj":      "\u200D",
+	"lrm":      "\u200E",
+	"rlm":      "\u200F",
+	"ndash":    "\u2013",
+	"mdash":    "\u2014",
+	"lsquo":    "\u2018",
+	"rsquo":    "\u2019",
+	"sbquo":    "\u201A",
+	"ldquo":    "\u201C",
+	"rdquo":    "\u201D",
+	"bdquo":    "\u201E",
+	"dagger":   "\u2020",
+	"Dagger":   "\u2021",
+	"permil":   "\u2030",
+	"lsaquo":   "\u2039",
+	"rsaquo":   "\u203A",
+	"euro":     "\u20AC",
+}
+
+// HTMLAutoClose is the set of HTML elements that
+// should be considered to close automatically.
+//
+// See the Decoder.Strict and Decoder.Entity fields' documentation.
+var HTMLAutoClose []string = htmlAutoClose
+
+var htmlAutoClose = []string{
+	/*
+		hget http://www.w3.org/TR/html4/loose.dtd |
+		9 sed -n 's/<!ELEMENT ([^ ]*) +- O EMPTY.+/	"\1",/p' | tr A-Z a-z
+	*/
+	"basefont",
+	"br",
+	"area",
+	"link",
+	"img",
+	"param",
+	"hr",
+	"input",
+	"col",
+	"frame",
+	"isindex",
+	"base",
+	"meta",
+}
+
+var (
+	escQuot = []byte("&#34;") // shorter than "&quot;"
+	escApos = []byte("&#39;") // shorter than "&apos;"
+	escAmp  = []byte("&amp;")
+	escLT   = []byte("&lt;")
+	escGT   = []byte("&gt;")
+	escTab  = []byte("&#x9;")
+	escNL   = []byte("&#xA;")
+	escCR   = []byte("&#xD;")
+	escFFFD = []byte("\uFFFD") // Unicode replacement character
+)
+
+// EscapeText writes to w the properly escaped XML equivalent
+// of the plain text data s.
+func EscapeText(w io.Writer, s []byte) error {
+	return escapeText(w, s, true)
+}
+
+// escapeText writes to w the properly escaped XML equivalent
+// of the plain text data s. If escapeNewline is true, newline
+// characters will be escaped.
+func escapeText(w io.Writer, s []byte, escapeNewline bool) error {
+	var esc []byte
+	last := 0
+	for i := 0; i < len(s); {
+		r, width := utf8.DecodeRune(s[i:])
+		i += width
+		switch r {
+		case '"':
+			esc = escQuot
+		case '\'':
+			esc = escApos
+		case '&':
+			esc = escAmp
+		case '<':
+			esc = escLT
+		case '>':
+			esc = escGT
+		case '\t':
+			esc = escTab
+		case '\n':
+			if !escapeNewline {
+				continue
+			}
+			esc = escNL
+		case '\r':
+			esc = escCR
+		default:
+			if !isInCharacterRange(r) || (r == 0xFFFD && width == 1) {
+				esc = escFFFD
+				break
+			}
+			continue
+		}
+		if _, err := w.Write(s[last : i-width]); err != nil {
+			return err
+		}
+		if _, err := w.Write(esc); err != nil {
+			return err
+		}
+		last = i
+	}
+	_, err := w.Write(s[last:])
+	return err
+}
+
+// EscapeString writes to p the properly escaped XML equivalent
+// of the plain text data s.
+func (p *printer) EscapeString(s string) {
+	var esc []byte
+	last := 0
+	for i := 0; i < len(s); {
+		r, width := utf8.DecodeRuneInString(s[i:])
+		i += width
+		switch r {
+		case '"':
+			esc = escQuot
+		case '\'':
+			esc = escApos
+		case '&':
+			esc = escAmp
+		case '<':
+			esc = escLT
+		case '>':
+			esc = escGT
+		case '\t':
+			esc = escTab
+		case '\n':
+			esc = escNL
+		case '\r':
+			esc = escCR
+		default:
+			if !isInCharacterRange(r) || (r == 0xFFFD && width == 1) {
+				esc = escFFFD
+				break
+			}
+			continue
+		}
+		p.WriteString(s[last : i-width])
+		p.Write(esc)
+		last = i
+	}
+	p.WriteString(s[last:])
+}
+
+// Escape is like EscapeText but omits the error return value.
+// It is provided for backwards compatibility with Go 1.0.
+// Code targeting Go 1.1 or later should use EscapeText.
+func Escape(w io.Writer, s []byte) {
+	EscapeText(w, s)
+}
+
+var (
+	cdataStart  = []byte("<![CDATA[")
+	cdataEnd    = []byte("]]>")
+	cdataEscape = []byte("]]]]><![CDATA[>")
+)
+
+// emitCDATA writes to w the CDATA-wrapped plain text data s.
+// It escapes CDATA directives nested in s.
+func emitCDATA(w io.Writer, s []byte) error {
+	if len(s) == 0 {
+		return nil
+	}
+	if _, err := w.Write(cdataStart); err != nil {
+		return err
+	}
+
+	for {
+		before, after, ok := bytes.Cut(s, cdataEnd)
+		if !ok {
+			break
+		}
+		// Found a nested CDATA directive end.
+		if _, err := w.Write(before); err != nil {
+			return err
+		}
+		if _, err := w.Write(cdataEscape); err != nil {
+			return err
+		}
+		s = after
+	}
+
+	if _, err := w.Write(s); err != nil {
+		return err
+	}
+
+	_, err := w.Write(cdataEnd)
+	return err
+}
+
+// procInst parses the `param="..."` or `param='...'`
+// value out of the provided string, returning "" if not found.
+func procInst(param, s string) string {
+	// TODO: this parsing is somewhat lame and not exact.
+	// It works for all actual cases, though.
+	param = param + "="
+	_, v, _ := strings.Cut(s, param)
+	if v == "" {
+		return ""
+	}
+	if v[0] != '\'' && v[0] != '"' {
+		return ""
+	}
+	unquote, _, ok := strings.Cut(v[1:], v[:1])
+	if !ok {
+		return ""
+	}
+	return unquote
+}
diff --git a/src/encoding/xml/xml_test.go b/src/encoding/xml/xml_test.go
new file mode 100644
index 0000000..19152db
--- /dev/null
+++ b/src/encoding/xml/xml_test.go
@@ -0,0 +1,1062 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package xml
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"reflect"
+	"strings"
+	"testing"
+	"unicode/utf8"
+)
+
+type toks struct {
+	earlyEOF bool
+	t        []Token
+}
+
+func (t *toks) Token() (Token, error) {
+	if len(t.t) == 0 {
+		return nil, io.EOF
+	}
+	var tok Token
+	tok, t.t = t.t[0], t.t[1:]
+	if t.earlyEOF && len(t.t) == 0 {
+		return tok, io.EOF
+	}
+	return tok, nil
+}
+
+func TestDecodeEOF(t *testing.T) {
+	start := StartElement{Name: Name{Local: "test"}}
+	tests := []struct {
+		name   string
+		tokens []Token
+		ok     bool
+	}{
+		{
+			name: "OK",
+			tokens: []Token{
+				start,
+				start.End(),
+			},
+			ok: true,
+		},
+		{
+			name: "Malformed",
+			tokens: []Token{
+				start,
+				StartElement{Name: Name{Local: "bad"}},
+				start.End(),
+			},
+			ok: false,
+		},
+	}
+	for _, tc := range tests {
+		for _, eof := range []bool{true, false} {
+			name := fmt.Sprintf("%s/earlyEOF=%v", tc.name, eof)
+			t.Run(name, func(t *testing.T) {
+				d := NewTokenDecoder(&toks{
+					earlyEOF: eof,
+					t:        tc.tokens,
+				})
+				err := d.Decode(&struct {
+					XMLName Name `xml:"test"`
+				}{})
+				if tc.ok && err != nil {
+					t.Fatalf("d.Decode: expected nil error, got %v", err)
+				}
+				if _, ok := err.(*SyntaxError); !tc.ok && !ok {
+					t.Errorf("d.Decode: expected syntax error, got %v", err)
+				}
+			})
+		}
+	}
+}
+
+type toksNil struct {
+	returnEOF bool
+	t         []Token
+}
+
+func (t *toksNil) Token() (Token, error) {
+	if len(t.t) == 0 {
+		if !t.returnEOF {
+			// Return nil, nil before returning an EOF. It's legal, but
+			// discouraged.
+			t.returnEOF = true
+			return nil, nil
+		}
+		return nil, io.EOF
+	}
+	var tok Token
+	tok, t.t = t.t[0], t.t[1:]
+	return tok, nil
+}
+
+func TestDecodeNilToken(t *testing.T) {
+	for _, strict := range []bool{true, false} {
+		name := fmt.Sprintf("Strict=%v", strict)
+		t.Run(name, func(t *testing.T) {
+			start := StartElement{Name: Name{Local: "test"}}
+			bad := StartElement{Name: Name{Local: "bad"}}
+			d := NewTokenDecoder(&toksNil{
+				// Malformed
+				t: []Token{start, bad, start.End()},
+			})
+			d.Strict = strict
+			err := d.Decode(&struct {
+				XMLName Name `xml:"test"`
+			}{})
+			if _, ok := err.(*SyntaxError); !ok {
+				t.Errorf("d.Decode: expected syntax error, got %v", err)
+			}
+		})
+	}
+}
+
+const testInput = `
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
+  "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
+<body xmlns:foo="ns1" xmlns="ns2" xmlns:tag="ns3" ` +
+	"\r\n\t" + `  >
+  <hello lang="en">World &lt;&gt;&apos;&quot; &#x767d;&#40300;翔</hello>
+  <query>&何; &is-it;</query>
+  <goodbye />
+  <outer foo:attr="value" xmlns:tag="ns4">
+    <inner/>
+  </outer>
+  <tag:name>
+    <![CDATA[Some text here.]]>
+  </tag:name>
+</body><!-- missing final newline -->`
+
+var testEntity = map[string]string{"何": "What", "is-it": "is it?"}
+
+var rawTokens = []Token{
+	CharData("\n"),
+	ProcInst{"xml", []byte(`version="1.0" encoding="UTF-8"`)},
+	CharData("\n"),
+	Directive(`DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
+  "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"`),
+	CharData("\n"),
+	StartElement{Name{"", "body"}, []Attr{{Name{"xmlns", "foo"}, "ns1"}, {Name{"", "xmlns"}, "ns2"}, {Name{"xmlns", "tag"}, "ns3"}}},
+	CharData("\n  "),
+	StartElement{Name{"", "hello"}, []Attr{{Name{"", "lang"}, "en"}}},
+	CharData("World <>'\" 白鵬翔"),
+	EndElement{Name{"", "hello"}},
+	CharData("\n  "),
+	StartElement{Name{"", "query"}, []Attr{}},
+	CharData("What is it?"),
+	EndElement{Name{"", "query"}},
+	CharData("\n  "),
+	StartElement{Name{"", "goodbye"}, []Attr{}},
+	EndElement{Name{"", "goodbye"}},
+	CharData("\n  "),
+	StartElement{Name{"", "outer"}, []Attr{{Name{"foo", "attr"}, "value"}, {Name{"xmlns", "tag"}, "ns4"}}},
+	CharData("\n    "),
+	StartElement{Name{"", "inner"}, []Attr{}},
+	EndElement{Name{"", "inner"}},
+	CharData("\n  "),
+	EndElement{Name{"", "outer"}},
+	CharData("\n  "),
+	StartElement{Name{"tag", "name"}, []Attr{}},
+	CharData("\n    "),
+	CharData("Some text here."),
+	CharData("\n  "),
+	EndElement{Name{"tag", "name"}},
+	CharData("\n"),
+	EndElement{Name{"", "body"}},
+	Comment(" missing final newline "),
+}
+
+var cookedTokens = []Token{
+	CharData("\n"),
+	ProcInst{"xml", []byte(`version="1.0" encoding="UTF-8"`)},
+	CharData("\n"),
+	Directive(`DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
+  "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"`),
+	CharData("\n"),
+	StartElement{Name{"ns2", "body"}, []Attr{{Name{"xmlns", "foo"}, "ns1"}, {Name{"", "xmlns"}, "ns2"}, {Name{"xmlns", "tag"}, "ns3"}}},
+	CharData("\n  "),
+	StartElement{Name{"ns2", "hello"}, []Attr{{Name{"", "lang"}, "en"}}},
+	CharData("World <>'\" 白鵬翔"),
+	EndElement{Name{"ns2", "hello"}},
+	CharData("\n  "),
+	StartElement{Name{"ns2", "query"}, []Attr{}},
+	CharData("What is it?"),
+	EndElement{Name{"ns2", "query"}},
+	CharData("\n  "),
+	StartElement{Name{"ns2", "goodbye"}, []Attr{}},
+	EndElement{Name{"ns2", "goodbye"}},
+	CharData("\n  "),
+	StartElement{Name{"ns2", "outer"}, []Attr{{Name{"ns1", "attr"}, "value"}, {Name{"xmlns", "tag"}, "ns4"}}},
+	CharData("\n    "),
+	StartElement{Name{"ns2", "inner"}, []Attr{}},
+	EndElement{Name{"ns2", "inner"}},
+	CharData("\n  "),
+	EndElement{Name{"ns2", "outer"}},
+	CharData("\n  "),
+	StartElement{Name{"ns3", "name"}, []Attr{}},
+	CharData("\n    "),
+	CharData("Some text here."),
+	CharData("\n  "),
+	EndElement{Name{"ns3", "name"}},
+	CharData("\n"),
+	EndElement{Name{"ns2", "body"}},
+	Comment(" missing final newline "),
+}
+
+const testInputAltEncoding = `
+<?xml version="1.0" encoding="x-testing-uppercase"?>
+<TAG>VALUE</TAG>`
+
+var rawTokensAltEncoding = []Token{
+	CharData("\n"),
+	ProcInst{"xml", []byte(`version="1.0" encoding="x-testing-uppercase"`)},
+	CharData("\n"),
+	StartElement{Name{"", "tag"}, []Attr{}},
+	CharData("value"),
+	EndElement{Name{"", "tag"}},
+}
+
+var xmlInput = []string{
+	// unexpected EOF cases
+	"<",
+	"<t",
+	"<t ",
+	"<t/",
+	"<!",
+	"<!-",
+	"<!--",
+	"<!--c-",
+	"<!--c--",
+	"<!d",
+	"<t></",
+	"<t></t",
+	"<?",
+	"<?p",
+	"<t a",
+	"<t a=",
+	"<t a='",
+	"<t a=''",
+	"<t/><![",
+	"<t/><![C",
+	"<t/><![CDATA[d",
+	"<t/><![CDATA[d]",
+	"<t/><![CDATA[d]]",
+
+	// other Syntax errors
+	"<>",
+	"<t/a",
+	"<0 />",
+	"<?0 >",
+	//	"<!0 >",	// let the Token() caller handle
+	"</0>",
+	"<t 0=''>",
+	"<t a='&'>",
+	"<t a='<'>",
+	"<t>&nbspc;</t>",
+	"<t a>",
+	"<t a=>",
+	"<t a=v>",
+	//	"<![CDATA[d]]>",	// let the Token() caller handle
+	"<t></e>",
+	"<t></>",
+	"<t></t!",
+	"<t>cdata]]></t>",
+}
+
+func TestRawToken(t *testing.T) {
+	d := NewDecoder(strings.NewReader(testInput))
+	d.Entity = testEntity
+	testRawToken(t, d, testInput, rawTokens)
+}
+
+const nonStrictInput = `
+<tag>non&entity</tag>
+<tag>&unknown;entity</tag>
+<tag>&#123</tag>
+<tag>&#zzz;</tag>
+<tag>&なまえ3;</tag>
+<tag>&lt-gt;</tag>
+<tag>&;</tag>
+<tag>&0a;</tag>
+`
+
+var nonStrictTokens = []Token{
+	CharData("\n"),
+	StartElement{Name{"", "tag"}, []Attr{}},
+	CharData("non&entity"),
+	EndElement{Name{"", "tag"}},
+	CharData("\n"),
+	StartElement{Name{"", "tag"}, []Attr{}},
+	CharData("&unknown;entity"),
+	EndElement{Name{"", "tag"}},
+	CharData("\n"),
+	StartElement{Name{"", "tag"}, []Attr{}},
+	CharData("&#123"),
+	EndElement{Name{"", "tag"}},
+	CharData("\n"),
+	StartElement{Name{"", "tag"}, []Attr{}},
+	CharData("&#zzz;"),
+	EndElement{Name{"", "tag"}},
+	CharData("\n"),
+	StartElement{Name{"", "tag"}, []Attr{}},
+	CharData("&なまえ3;"),
+	EndElement{Name{"", "tag"}},
+	CharData("\n"),
+	StartElement{Name{"", "tag"}, []Attr{}},
+	CharData("&lt-gt;"),
+	EndElement{Name{"", "tag"}},
+	CharData("\n"),
+	StartElement{Name{"", "tag"}, []Attr{}},
+	CharData("&;"),
+	EndElement{Name{"", "tag"}},
+	CharData("\n"),
+	StartElement{Name{"", "tag"}, []Attr{}},
+	CharData("&0a;"),
+	EndElement{Name{"", "tag"}},
+	CharData("\n"),
+}
+
+func TestNonStrictRawToken(t *testing.T) {
+	d := NewDecoder(strings.NewReader(nonStrictInput))
+	d.Strict = false
+	testRawToken(t, d, nonStrictInput, nonStrictTokens)
+}
+
+type downCaser struct {
+	t *testing.T
+	r io.ByteReader
+}
+
+func (d *downCaser) ReadByte() (c byte, err error) {
+	c, err = d.r.ReadByte()
+	if c >= 'A' && c <= 'Z' {
+		c += 'a' - 'A'
+	}
+	return
+}
+
+func (d *downCaser) Read(p []byte) (int, error) {
+	d.t.Fatalf("unexpected Read call on downCaser reader")
+	panic("unreachable")
+}
+
+func TestRawTokenAltEncoding(t *testing.T) {
+	d := NewDecoder(strings.NewReader(testInputAltEncoding))
+	d.CharsetReader = func(charset string, input io.Reader) (io.Reader, error) {
+		if charset != "x-testing-uppercase" {
+			t.Fatalf("unexpected charset %q", charset)
+		}
+		return &downCaser{t, input.(io.ByteReader)}, nil
+	}
+	testRawToken(t, d, testInputAltEncoding, rawTokensAltEncoding)
+}
+
+func TestRawTokenAltEncodingNoConverter(t *testing.T) {
+	d := NewDecoder(strings.NewReader(testInputAltEncoding))
+	token, err := d.RawToken()
+	if token == nil {
+		t.Fatalf("expected a token on first RawToken call")
+	}
+	if err != nil {
+		t.Fatal(err)
+	}
+	token, err = d.RawToken()
+	if token != nil {
+		t.Errorf("expected a nil token; got %#v", token)
+	}
+	if err == nil {
+		t.Fatalf("expected an error on second RawToken call")
+	}
+	const encoding = "x-testing-uppercase"
+	if !strings.Contains(err.Error(), encoding) {
+		t.Errorf("expected error to contain %q; got error: %v",
+			encoding, err)
+	}
+}
+
+func testRawToken(t *testing.T, d *Decoder, raw string, rawTokens []Token) {
+	lastEnd := int64(0)
+	for i, want := range rawTokens {
+		start := d.InputOffset()
+		have, err := d.RawToken()
+		end := d.InputOffset()
+		if err != nil {
+			t.Fatalf("token %d: unexpected error: %s", i, err)
+		}
+		if !reflect.DeepEqual(have, want) {
+			var shave, swant string
+			if _, ok := have.(CharData); ok {
+				shave = fmt.Sprintf("CharData(%q)", have)
+			} else {
+				shave = fmt.Sprintf("%#v", have)
+			}
+			if _, ok := want.(CharData); ok {
+				swant = fmt.Sprintf("CharData(%q)", want)
+			} else {
+				swant = fmt.Sprintf("%#v", want)
+			}
+			t.Errorf("token %d = %s, want %s", i, shave, swant)
+		}
+
+		// Check that InputOffset returned actual token.
+		switch {
+		case start < lastEnd:
+			t.Errorf("token %d: position [%d,%d) for %T is before previous token", i, start, end, have)
+		case start >= end:
+			// Special case: EndElement can be synthesized.
+			if start == end && end == lastEnd {
+				break
+			}
+			t.Errorf("token %d: position [%d,%d) for %T is empty", i, start, end, have)
+		case end > int64(len(raw)):
+			t.Errorf("token %d: position [%d,%d) for %T extends beyond input", i, start, end, have)
+		default:
+			text := raw[start:end]
+			if strings.ContainsAny(text, "<>") && (!strings.HasPrefix(text, "<") || !strings.HasSuffix(text, ">")) {
+				t.Errorf("token %d: misaligned raw token %#q for %T", i, text, have)
+			}
+		}
+		lastEnd = end
+	}
+}
+
+// Ensure that directives (specifically !DOCTYPE) include the complete
+// text of any nested directives, noting that < and > do not change
+// nesting depth if they are in single or double quotes.
+
+var nestedDirectivesInput = `
+<!DOCTYPE [<!ENTITY rdf "http://www.w3.org/1999/02/22-rdf-syntax-ns#">]>
+<!DOCTYPE [<!ENTITY xlt ">">]>
+<!DOCTYPE [<!ENTITY xlt "<">]>
+<!DOCTYPE [<!ENTITY xlt '>'>]>
+<!DOCTYPE [<!ENTITY xlt '<'>]>
+<!DOCTYPE [<!ENTITY xlt '">'>]>
+<!DOCTYPE [<!ENTITY xlt "'<">]>
+`
+
+var nestedDirectivesTokens = []Token{
+	CharData("\n"),
+	Directive(`DOCTYPE [<!ENTITY rdf "http://www.w3.org/1999/02/22-rdf-syntax-ns#">]`),
+	CharData("\n"),
+	Directive(`DOCTYPE [<!ENTITY xlt ">">]`),
+	CharData("\n"),
+	Directive(`DOCTYPE [<!ENTITY xlt "<">]`),
+	CharData("\n"),
+	Directive(`DOCTYPE [<!ENTITY xlt '>'>]`),
+	CharData("\n"),
+	Directive(`DOCTYPE [<!ENTITY xlt '<'>]`),
+	CharData("\n"),
+	Directive(`DOCTYPE [<!ENTITY xlt '">'>]`),
+	CharData("\n"),
+	Directive(`DOCTYPE [<!ENTITY xlt "'<">]`),
+	CharData("\n"),
+}
+
+func TestNestedDirectives(t *testing.T) {
+	d := NewDecoder(strings.NewReader(nestedDirectivesInput))
+
+	for i, want := range nestedDirectivesTokens {
+		have, err := d.Token()
+		if err != nil {
+			t.Fatalf("token %d: unexpected error: %s", i, err)
+		}
+		if !reflect.DeepEqual(have, want) {
+			t.Errorf("token %d = %#v want %#v", i, have, want)
+		}
+	}
+}
+
+func TestToken(t *testing.T) {
+	d := NewDecoder(strings.NewReader(testInput))
+	d.Entity = testEntity
+
+	for i, want := range cookedTokens {
+		have, err := d.Token()
+		if err != nil {
+			t.Fatalf("token %d: unexpected error: %s", i, err)
+		}
+		if !reflect.DeepEqual(have, want) {
+			t.Errorf("token %d = %#v want %#v", i, have, want)
+		}
+	}
+}
+
+func TestSyntax(t *testing.T) {
+	for i := range xmlInput {
+		d := NewDecoder(strings.NewReader(xmlInput[i]))
+		var err error
+		for _, err = d.Token(); err == nil; _, err = d.Token() {
+		}
+		if _, ok := err.(*SyntaxError); !ok {
+			t.Fatalf(`xmlInput "%s": expected SyntaxError not received`, xmlInput[i])
+		}
+	}
+}
+
+type allScalars struct {
+	True1     bool
+	True2     bool
+	False1    bool
+	False2    bool
+	Int       int
+	Int8      int8
+	Int16     int16
+	Int32     int32
+	Int64     int64
+	Uint      int
+	Uint8     uint8
+	Uint16    uint16
+	Uint32    uint32
+	Uint64    uint64
+	Uintptr   uintptr
+	Float32   float32
+	Float64   float64
+	String    string
+	PtrString *string
+}
+
+var all = allScalars{
+	True1:     true,
+	True2:     true,
+	False1:    false,
+	False2:    false,
+	Int:       1,
+	Int8:      -2,
+	Int16:     3,
+	Int32:     -4,
+	Int64:     5,
+	Uint:      6,
+	Uint8:     7,
+	Uint16:    8,
+	Uint32:    9,
+	Uint64:    10,
+	Uintptr:   11,
+	Float32:   13.0,
+	Float64:   14.0,
+	String:    "15",
+	PtrString: &sixteen,
+}
+
+var sixteen = "16"
+
+const testScalarsInput = `<allscalars>
+	<True1>true</True1>
+	<True2>1</True2>
+	<False1>false</False1>
+	<False2>0</False2>
+	<Int>1</Int>
+	<Int8>-2</Int8>
+	<Int16>3</Int16>
+	<Int32>-4</Int32>
+	<Int64>5</Int64>
+	<Uint>6</Uint>
+	<Uint8>7</Uint8>
+	<Uint16>8</Uint16>
+	<Uint32>9</Uint32>
+	<Uint64>10</Uint64>
+	<Uintptr>11</Uintptr>
+	<Float>12.0</Float>
+	<Float32>13.0</Float32>
+	<Float64>14.0</Float64>
+	<String>15</String>
+	<PtrString>16</PtrString>
+</allscalars>`
+
+func TestAllScalars(t *testing.T) {
+	var a allScalars
+	err := Unmarshal([]byte(testScalarsInput), &a)
+
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !reflect.DeepEqual(a, all) {
+		t.Errorf("have %+v want %+v", a, all)
+	}
+}
+
+type item struct {
+	FieldA string
+}
+
+func TestIssue569(t *testing.T) {
+	data := `<item><FieldA>abcd</FieldA></item>`
+	var i item
+	err := Unmarshal([]byte(data), &i)
+
+	if err != nil || i.FieldA != "abcd" {
+		t.Fatal("Expecting abcd")
+	}
+}
+
+func TestUnquotedAttrs(t *testing.T) {
+	data := "<tag attr=azAZ09:-_\t>"
+	d := NewDecoder(strings.NewReader(data))
+	d.Strict = false
+	token, err := d.Token()
+	if _, ok := err.(*SyntaxError); ok {
+		t.Errorf("Unexpected error: %v", err)
+	}
+	if token.(StartElement).Name.Local != "tag" {
+		t.Errorf("Unexpected tag name: %v", token.(StartElement).Name.Local)
+	}
+	attr := token.(StartElement).Attr[0]
+	if attr.Value != "azAZ09:-_" {
+		t.Errorf("Unexpected attribute value: %v", attr.Value)
+	}
+	if attr.Name.Local != "attr" {
+		t.Errorf("Unexpected attribute name: %v", attr.Name.Local)
+	}
+}
+
+func TestValuelessAttrs(t *testing.T) {
+	tests := [][3]string{
+		{"<p nowrap>", "p", "nowrap"},
+		{"<p nowrap >", "p", "nowrap"},
+		{"<input checked/>", "input", "checked"},
+		{"<input checked />", "input", "checked"},
+	}
+	for _, test := range tests {
+		d := NewDecoder(strings.NewReader(test[0]))
+		d.Strict = false
+		token, err := d.Token()
+		if _, ok := err.(*SyntaxError); ok {
+			t.Errorf("Unexpected error: %v", err)
+		}
+		if token.(StartElement).Name.Local != test[1] {
+			t.Errorf("Unexpected tag name: %v", token.(StartElement).Name.Local)
+		}
+		attr := token.(StartElement).Attr[0]
+		if attr.Value != test[2] {
+			t.Errorf("Unexpected attribute value: %v", attr.Value)
+		}
+		if attr.Name.Local != test[2] {
+			t.Errorf("Unexpected attribute name: %v", attr.Name.Local)
+		}
+	}
+}
+
+func TestCopyTokenCharData(t *testing.T) {
+	data := []byte("same data")
+	var tok1 Token = CharData(data)
+	tok2 := CopyToken(tok1)
+	if !reflect.DeepEqual(tok1, tok2) {
+		t.Error("CopyToken(CharData) != CharData")
+	}
+	data[1] = 'o'
+	if reflect.DeepEqual(tok1, tok2) {
+		t.Error("CopyToken(CharData) uses same buffer.")
+	}
+}
+
+func TestCopyTokenStartElement(t *testing.T) {
+	elt := StartElement{Name{"", "hello"}, []Attr{{Name{"", "lang"}, "en"}}}
+	var tok1 Token = elt
+	tok2 := CopyToken(tok1)
+	if tok1.(StartElement).Attr[0].Value != "en" {
+		t.Error("CopyToken overwrote Attr[0]")
+	}
+	if !reflect.DeepEqual(tok1, tok2) {
+		t.Error("CopyToken(StartElement) != StartElement")
+	}
+	tok1.(StartElement).Attr[0] = Attr{Name{"", "lang"}, "de"}
+	if reflect.DeepEqual(tok1, tok2) {
+		t.Error("CopyToken(CharData) uses same buffer.")
+	}
+}
+
+func TestSyntaxErrorLineNum(t *testing.T) {
+	testInput := "<P>Foo<P>\n\n<P>Bar</>\n"
+	d := NewDecoder(strings.NewReader(testInput))
+	var err error
+	for _, err = d.Token(); err == nil; _, err = d.Token() {
+	}
+	synerr, ok := err.(*SyntaxError)
+	if !ok {
+		t.Error("Expected SyntaxError.")
+	}
+	if synerr.Line != 3 {
+		t.Error("SyntaxError didn't have correct line number.")
+	}
+}
+
+func TestTrailingRawToken(t *testing.T) {
+	input := `<FOO></FOO>  `
+	d := NewDecoder(strings.NewReader(input))
+	var err error
+	for _, err = d.RawToken(); err == nil; _, err = d.RawToken() {
+	}
+	if err != io.EOF {
+		t.Fatalf("d.RawToken() = _, %v, want _, io.EOF", err)
+	}
+}
+
+func TestTrailingToken(t *testing.T) {
+	input := `<FOO></FOO>  `
+	d := NewDecoder(strings.NewReader(input))
+	var err error
+	for _, err = d.Token(); err == nil; _, err = d.Token() {
+	}
+	if err != io.EOF {
+		t.Fatalf("d.Token() = _, %v, want _, io.EOF", err)
+	}
+}
+
+func TestEntityInsideCDATA(t *testing.T) {
+	input := `<test><![CDATA[ &val=foo ]]></test>`
+	d := NewDecoder(strings.NewReader(input))
+	var err error
+	for _, err = d.Token(); err == nil; _, err = d.Token() {
+	}
+	if err != io.EOF {
+		t.Fatalf("d.Token() = _, %v, want _, io.EOF", err)
+	}
+}
+
+var characterTests = []struct {
+	in  string
+	err string
+}{
+	{"\x12<doc/>", "illegal character code U+0012"},
+	{"<?xml version=\"1.0\"?>\x0b<doc/>", "illegal character code U+000B"},
+	{"\xef\xbf\xbe<doc/>", "illegal character code U+FFFE"},
+	{"<?xml version=\"1.0\"?><doc>\r\n<hiya/>\x07<toots/></doc>", "illegal character code U+0007"},
+	{"<?xml version=\"1.0\"?><doc \x12='value'>what's up</doc>", "expected attribute name in element"},
+	{"<doc>&abc\x01;</doc>", "invalid character entity &abc (no semicolon)"},
+	{"<doc>&\x01;</doc>", "invalid character entity & (no semicolon)"},
+	{"<doc>&\xef\xbf\xbe;</doc>", "invalid character entity &\uFFFE;"},
+	{"<doc>&hello;</doc>", "invalid character entity &hello;"},
+}
+
+func TestDisallowedCharacters(t *testing.T) {
+
+	for i, tt := range characterTests {
+		d := NewDecoder(strings.NewReader(tt.in))
+		var err error
+
+		for err == nil {
+			_, err = d.Token()
+		}
+		synerr, ok := err.(*SyntaxError)
+		if !ok {
+			t.Fatalf("input %d d.Token() = _, %v, want _, *SyntaxError", i, err)
+		}
+		if synerr.Msg != tt.err {
+			t.Fatalf("input %d synerr.Msg wrong: want %q, got %q", i, tt.err, synerr.Msg)
+		}
+	}
+}
+
+func TestIsInCharacterRange(t *testing.T) {
+	invalid := []rune{
+		utf8.MaxRune + 1,
+		0xD800, // surrogate min
+		0xDFFF, // surrogate max
+		-1,
+	}
+	for _, r := range invalid {
+		if isInCharacterRange(r) {
+			t.Errorf("rune %U considered valid", r)
+		}
+	}
+}
+
+var procInstTests = []struct {
+	input  string
+	expect [2]string
+}{
+	{`version="1.0" encoding="utf-8"`, [2]string{"1.0", "utf-8"}},
+	{`version="1.0" encoding='utf-8'`, [2]string{"1.0", "utf-8"}},
+	{`version="1.0" encoding='utf-8' `, [2]string{"1.0", "utf-8"}},
+	{`version="1.0" encoding=utf-8`, [2]string{"1.0", ""}},
+	{`encoding="FOO" `, [2]string{"", "FOO"}},
+}
+
+func TestProcInstEncoding(t *testing.T) {
+	for _, test := range procInstTests {
+		if got := procInst("version", test.input); got != test.expect[0] {
+			t.Errorf("procInst(version, %q) = %q; want %q", test.input, got, test.expect[0])
+		}
+		if got := procInst("encoding", test.input); got != test.expect[1] {
+			t.Errorf("procInst(encoding, %q) = %q; want %q", test.input, got, test.expect[1])
+		}
+	}
+}
+
+// Ensure that directives with comments include the complete
+// text of any nested directives.
+
+var directivesWithCommentsInput = `
+<!DOCTYPE [<!-- a comment --><!ENTITY rdf "http://www.w3.org/1999/02/22-rdf-syntax-ns#">]>
+<!DOCTYPE [<!ENTITY go "Golang"><!-- a comment-->]>
+<!DOCTYPE <!-> <!> <!----> <!-->--> <!--->--> [<!ENTITY go "Golang"><!-- a comment-->]>
+`
+
+var directivesWithCommentsTokens = []Token{
+	CharData("\n"),
+	Directive(`DOCTYPE [ <!ENTITY rdf "http://www.w3.org/1999/02/22-rdf-syntax-ns#">]`),
+	CharData("\n"),
+	Directive(`DOCTYPE [<!ENTITY go "Golang"> ]`),
+	CharData("\n"),
+	Directive(`DOCTYPE <!-> <!>       [<!ENTITY go "Golang"> ]`),
+	CharData("\n"),
+}
+
+func TestDirectivesWithComments(t *testing.T) {
+	d := NewDecoder(strings.NewReader(directivesWithCommentsInput))
+
+	for i, want := range directivesWithCommentsTokens {
+		have, err := d.Token()
+		if err != nil {
+			t.Fatalf("token %d: unexpected error: %s", i, err)
+		}
+		if !reflect.DeepEqual(have, want) {
+			t.Errorf("token %d = %#v want %#v", i, have, want)
+		}
+	}
+}
+
+// Writer whose Write method always returns an error.
+type errWriter struct{}
+
+func (errWriter) Write(p []byte) (n int, err error) { return 0, fmt.Errorf("unwritable") }
+
+func TestEscapeTextIOErrors(t *testing.T) {
+	expectErr := "unwritable"
+	err := EscapeText(errWriter{}, []byte{'A'})
+
+	if err == nil || err.Error() != expectErr {
+		t.Errorf("have %v, want %v", err, expectErr)
+	}
+}
+
+func TestEscapeTextInvalidChar(t *testing.T) {
+	input := []byte("A \x00 terminated string.")
+	expected := "A \uFFFD terminated string."
+
+	buff := new(bytes.Buffer)
+	if err := EscapeText(buff, input); err != nil {
+		t.Fatalf("have %v, want nil", err)
+	}
+	text := buff.String()
+
+	if text != expected {
+		t.Errorf("have %v, want %v", text, expected)
+	}
+}
+
+func TestIssue5880(t *testing.T) {
+	type T []byte
+	data, err := Marshal(T{192, 168, 0, 1})
+	if err != nil {
+		t.Errorf("Marshal error: %v", err)
+	}
+	if !utf8.Valid(data) {
+		t.Errorf("Marshal generated invalid UTF-8: %x", data)
+	}
+}
+
+func TestIssue11405(t *testing.T) {
+	testCases := []string{
+		"<root>",
+		"<root><foo>",
+		"<root><foo></foo>",
+	}
+	for _, tc := range testCases {
+		d := NewDecoder(strings.NewReader(tc))
+		var err error
+		for {
+			_, err = d.Token()
+			if err != nil {
+				break
+			}
+		}
+		if _, ok := err.(*SyntaxError); !ok {
+			t.Errorf("%s: Token: Got error %v, want SyntaxError", tc, err)
+		}
+	}
+}
+
+func TestIssue12417(t *testing.T) {
+	testCases := []struct {
+		s  string
+		ok bool
+	}{
+		{`<?xml encoding="UtF-8" version="1.0"?><root/>`, true},
+		{`<?xml encoding="UTF-8" version="1.0"?><root/>`, true},
+		{`<?xml encoding="utf-8" version="1.0"?><root/>`, true},
+		{`<?xml encoding="uuu-9" version="1.0"?><root/>`, false},
+	}
+	for _, tc := range testCases {
+		d := NewDecoder(strings.NewReader(tc.s))
+		var err error
+		for {
+			_, err = d.Token()
+			if err != nil {
+				if err == io.EOF {
+					err = nil
+				}
+				break
+			}
+		}
+		if err != nil && tc.ok {
+			t.Errorf("%q: Encoding charset: expected no error, got %s", tc.s, err)
+			continue
+		}
+		if err == nil && !tc.ok {
+			t.Errorf("%q: Encoding charset: expected error, got nil", tc.s)
+		}
+	}
+}
+
+func tokenMap(mapping func(t Token) Token) func(TokenReader) TokenReader {
+	return func(src TokenReader) TokenReader {
+		return mapper{
+			t: src,
+			f: mapping,
+		}
+	}
+}
+
+type mapper struct {
+	t TokenReader
+	f func(Token) Token
+}
+
+func (m mapper) Token() (Token, error) {
+	tok, err := m.t.Token()
+	if err != nil {
+		return nil, err
+	}
+	return m.f(tok), nil
+}
+
+func TestNewTokenDecoderIdempotent(t *testing.T) {
+	d := NewDecoder(strings.NewReader(`<br>`))
+	d2 := NewTokenDecoder(d)
+	if d != d2 {
+		t.Error("NewTokenDecoder did not detect underlying Decoder")
+	}
+}
+
+func TestWrapDecoder(t *testing.T) {
+	d := NewDecoder(strings.NewReader(`<quote>[Re-enter Clown with a letter, and FABIAN]</quote>`))
+	m := tokenMap(func(t Token) Token {
+		switch tok := t.(type) {
+		case StartElement:
+			if tok.Name.Local == "quote" {
+				tok.Name.Local = "blocking"
+				return tok
+			}
+		case EndElement:
+			if tok.Name.Local == "quote" {
+				tok.Name.Local = "blocking"
+				return tok
+			}
+		}
+		return t
+	})
+
+	d = NewTokenDecoder(m(d))
+
+	o := struct {
+		XMLName  Name   `xml:"blocking"`
+		Chardata string `xml:",chardata"`
+	}{}
+
+	if err := d.Decode(&o); err != nil {
+		t.Fatal("Got unexpected error while decoding:", err)
+	}
+
+	if o.Chardata != "[Re-enter Clown with a letter, and FABIAN]" {
+		t.Fatalf("Got unexpected chardata: `%s`\n", o.Chardata)
+	}
+}
+
+type tokReader struct{}
+
+func (tokReader) Token() (Token, error) {
+	return StartElement{}, nil
+}
+
+type Failure struct{}
+
+func (Failure) UnmarshalXML(*Decoder, StartElement) error {
+	return nil
+}
+
+func TestTokenUnmarshaler(t *testing.T) {
+	defer func() {
+		if r := recover(); r != nil {
+			t.Error("Unexpected panic using custom token unmarshaler")
+		}
+	}()
+
+	d := NewTokenDecoder(tokReader{})
+	d.Decode(&Failure{})
+}
+
+func testRoundTrip(t *testing.T, input string) {
+	d := NewDecoder(strings.NewReader(input))
+	var tokens []Token
+	var buf bytes.Buffer
+	e := NewEncoder(&buf)
+	for {
+		tok, err := d.Token()
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			t.Fatalf("invalid input: %v", err)
+		}
+		if err := e.EncodeToken(tok); err != nil {
+			t.Fatalf("failed to re-encode input: %v", err)
+		}
+		tokens = append(tokens, CopyToken(tok))
+	}
+	if err := e.Flush(); err != nil {
+		t.Fatal(err)
+	}
+
+	d = NewDecoder(&buf)
+	for {
+		tok, err := d.Token()
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			t.Fatalf("failed to decode output: %v", err)
+		}
+		if len(tokens) == 0 {
+			t.Fatalf("unexpected token: %#v", tok)
+		}
+		a, b := tokens[0], tok
+		if !reflect.DeepEqual(a, b) {
+			t.Fatalf("token mismatch: %#v vs %#v", a, b)
+		}
+		tokens = tokens[1:]
+	}
+	if len(tokens) > 0 {
+		t.Fatalf("lost tokens: %#v", tokens)
+	}
+}
+
+func TestRoundTrip(t *testing.T) {
+	tests := map[string]string{
+		"leading colon":          `<::Test ::foo="bar"><:::Hello></:::Hello><Hello></Hello></::Test>`,
+		"trailing colon":         `<foo abc:="x"></foo>`,
+		"double colon":           `<x:y:foo></x:y:foo>`,
+		"comments in directives": `<!ENTITY x<!<!-- c1 [ " -->--x --> > <e></e> <!DOCTYPE xxx [ x<!-- c2 " -->--x ]>`,
+	}
+	for name, input := range tests {
+		t.Run(name, func(t *testing.T) { testRoundTrip(t, input) })
+	}
+}