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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-16 19:19:13 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-16 19:19:13 +0000
commitccd992355df7192993c666236047820244914598 (patch)
treef00fea65147227b7743083c6148396f74cd66935 /src/encoding/ascii85
parentInitial commit. (diff)
downloadgolang-1.21-ccd992355df7192993c666236047820244914598.tar.xz
golang-1.21-ccd992355df7192993c666236047820244914598.zip
Adding upstream version 1.21.8.upstream/1.21.8
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'src/encoding/ascii85')
-rw-r--r--src/encoding/ascii85/ascii85.go307
-rw-r--r--src/encoding/ascii85/ascii85_test.go214
2 files changed, 521 insertions, 0 deletions
diff --git a/src/encoding/ascii85/ascii85.go b/src/encoding/ascii85/ascii85.go
new file mode 100644
index 0000000..1f1fb00
--- /dev/null
+++ b/src/encoding/ascii85/ascii85.go
@@ -0,0 +1,307 @@
+// 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..578829e
--- /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 := &strings.Builder{}
+ 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 := &strings.Builder{}
+ 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)
+ }
+}