1 files changed, 583 insertions, 0 deletions
diff --git a/src/encoding/base32/base32.go b/src/encoding/base32/base32.go
new file mode 100644
index 0000000..4a61199
--- /dev/null
+++ b/src/encoding/base32/base32.go
@@ -0,0 +1,583 @@
+// 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"
+	"slices"
+	"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   // mapping of symbol index to symbol byte value
+	decodeMap [256]uint8 // mapping of symbol byte value to symbol index
+	padChar   rune
+}
+
+const (
+	StdPadding rune = '=' // Standard padding character
+	NoPadding  rune = -1  // No padding
+)
+
+const (
+	decodeMapInitialize = "" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff"
+	invalidIndex = '\xff'
+)
+
+// NewEncoding returns a new padded Encoding defined by the given alphabet,
+// which must be a 32-byte string that contains unique byte values and
+// does not contain the padding character or CR / LF ('\r', '\n').
+// The alphabet is treated as a sequence of byte values
+// without any special treatment for multi-byte UTF-8.
+// The resulting Encoding uses the default padding character ('='),
+// which may be changed or disabled via [Encoding.WithPadding].
+func NewEncoding(encoder string) *Encoding {
+	if len(encoder) != 32 {
+		panic("encoding alphabet is not 32-bytes long")
+	}
+
+	e := new(Encoding)
+	e.padChar = StdPadding
+	copy(e.encode[:], encoder)
+	copy(e.decodeMap[:], decodeMapInitialize)
+
+	for i := 0; i < len(encoder); i++ {
+		// Note: While we document that the alphabet cannot contain
+		// the padding character, we do not enforce it since we do not know
+		// if the caller intends to switch the padding from StdPadding later.
+		switch {
+		case encoder[i] == '\n' || encoder[i] == '\r':
+			panic("encoding alphabet contains newline character")
+		case e.decodeMap[encoder[i]] != invalidIndex:
+			panic("encoding alphabet includes duplicate symbols")
+		}
+		e.decodeMap[encoder[i]] = uint8(i)
+	}
+	return e
+}
+
+// StdEncoding is the standard base32 encoding, as defined in RFC 4648.
+var StdEncoding = NewEncoding("ABCDEFGHIJKLMNOPQRSTUVWXYZ234567")
+
+// HexEncoding is the “Extended Hex Alphabet” defined in RFC 4648.
+// It is typically used in DNS.
+var HexEncoding = NewEncoding("0123456789ABCDEFGHIJKLMNOPQRSTUV")
+
+// 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,
+// must not be negative, and must be a rune equal or below '\xff'.
+// Padding characters above '\x7f' are encoded as their exact byte value
+// rather than using the UTF-8 representation of the codepoint.
+func (enc Encoding) WithPadding(padding rune) *Encoding {
+	switch {
+	case padding < NoPadding || padding == '\r' || padding == '\n' || padding > 0xff:
+		panic("invalid padding")
+	case padding != NoPadding && enc.decodeMap[byte(padding)] != invalidIndex:
+		panic("padding contained in alphabet")
+	}
+	enc.padChar = padding
+	return &enc
+}
+
+/*
+ * Encoder
+ */
+
+// Encode encodes src using the encoding enc,
+// writing [Encoding.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) {
+	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) / 5) * 5
+	for si < n {
+		// Combining two 32 bit loads allows the same code to be used
+		// for 32 and 64 bit platforms.
+		hi := uint32(src[si+0])<<24 | uint32(src[si+1])<<16 | uint32(src[si+2])<<8 | uint32(src[si+3])
+		lo := hi<<8 | uint32(src[si+4])
+
+		dst[di+0] = enc.encode[(hi>>27)&0x1F]
+		dst[di+1] = enc.encode[(hi>>22)&0x1F]
+		dst[di+2] = enc.encode[(hi>>17)&0x1F]
+		dst[di+3] = enc.encode[(hi>>12)&0x1F]
+		dst[di+4] = enc.encode[(hi>>7)&0x1F]
+		dst[di+5] = enc.encode[(hi>>2)&0x1F]
+		dst[di+6] = enc.encode[(lo>>5)&0x1F]
+		dst[di+7] = enc.encode[(lo)&0x1F]
+
+		si += 5
+		di += 8
+	}
+
+	// Add the remaining small block
+	remain := len(src) - si
+	if remain == 0 {
+		return
+	}
+
+	// Encode the remaining bytes in reverse order.
+	val := uint32(0)
+	switch remain {
+	case 4:
+		val |= uint32(src[si+3])
+		dst[di+6] = enc.encode[val<<3&0x1F]
+		dst[di+5] = enc.encode[val>>2&0x1F]
+		fallthrough
+	case 3:
+		val |= uint32(src[si+2]) << 8
+		dst[di+4] = enc.encode[val>>7&0x1F]
+		fallthrough
+	case 2:
+		val |= uint32(src[si+1]) << 16
+		dst[di+3] = enc.encode[val>>12&0x1F]
+		dst[di+2] = enc.encode[val>>17&0x1F]
+		fallthrough
+	case 1:
+		val |= uint32(src[si+0]) << 24
+		dst[di+1] = enc.encode[val>>22&0x1F]
+		dst[di+0] = enc.encode[val>>27&0x1F]
+	}
+
+	// Pad the final quantum
+	if enc.padChar != NoPadding {
+		nPad := (remain * 8 / 5) + 1
+		for i := nPad; i < 8; i++ {
+			dst[di+i] = byte(enc.padChar)
+		}
+	}
+}
+
+// AppendEncode appends the base32 encoded src to dst
+// and returns the extended buffer.
+func (enc *Encoding) AppendEncode(dst, src []byte) []byte {
+	n := enc.EncodedLen(len(src))
+	dst = slices.Grow(dst, n)
+	enc.Encode(dst[len(dst):][:n], src)
+	return dst[:len(dst)+n]
+}
+
+// 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/5*8 + (n%5*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
+// [Encoding.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].
+// Newline 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
+}
+
+// AppendDecode appends the base32 decoded src to dst
+// and returns the extended buffer.
+// If the input is malformed, it returns the partially decoded src and an error.
+func (enc *Encoding) AppendDecode(dst, src []byte) ([]byte, error) {
+	// Compute the output size without padding to avoid over allocating.
+	n := len(src)
+	for n > 0 && rune(src[n-1]) == enc.padChar {
+		n--
+	}
+	n = decodedLen(n, NoPadding)
+
+	dst = slices.Grow(dst, n)
+	n, err := enc.Decode(dst[len(dst):][:n], src)
+	return dst[:len(dst)+n], err
+}
+
+// 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
+	}
+	if nn > 0 && d.end {
+		return 0, CorruptInputError(0)
+	}
+
+	// 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 {
+	return decodedLen(n, enc.padChar)
+}
+
+func decodedLen(n int, padChar rune) int {
+	if padChar == NoPadding {
+		return n/8*5 + n%8*5/8
+	}
+	return n / 8 * 5
+}