summaryrefslogtreecommitdiff
path: root/src/pkg/compress/flate/inflate.go
diff options
context:
space:
mode:
Diffstat (limited to 'src/pkg/compress/flate/inflate.go')
-rw-r--r--src/pkg/compress/flate/inflate.go708
1 files changed, 0 insertions, 708 deletions
diff --git a/src/pkg/compress/flate/inflate.go b/src/pkg/compress/flate/inflate.go
deleted file mode 100644
index 3845f1204..000000000
--- a/src/pkg/compress/flate/inflate.go
+++ /dev/null
@@ -1,708 +0,0 @@
-// 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 flate implements the DEFLATE compressed data format, described in
-// RFC 1951. The gzip and zlib packages implement access to DEFLATE-based file
-// formats.
-package flate
-
-import (
- "bufio"
- "io"
- "os"
- "strconv"
-)
-
-const (
- maxCodeLen = 16 // max length of Huffman code
- maxHist = 32768 // max history required
- maxLit = 286
- maxDist = 32
- numCodes = 19 // number of codes in Huffman meta-code
-)
-
-// A CorruptInputError reports the presence of corrupt input at a given offset.
-type CorruptInputError int64
-
-func (e CorruptInputError) String() string {
- return "flate: corrupt input before offset " + strconv.Itoa64(int64(e))
-}
-
-// An InternalError reports an error in the flate code itself.
-type InternalError string
-
-func (e InternalError) String() string { return "flate: internal error: " + string(e) }
-
-// A ReadError reports an error encountered while reading input.
-type ReadError struct {
- Offset int64 // byte offset where error occurred
- Error os.Error // error returned by underlying Read
-}
-
-func (e *ReadError) String() string {
- return "flate: read error at offset " + strconv.Itoa64(e.Offset) + ": " + e.Error.String()
-}
-
-// A WriteError reports an error encountered while writing output.
-type WriteError struct {
- Offset int64 // byte offset where error occurred
- Error os.Error // error returned by underlying Write
-}
-
-func (e *WriteError) String() string {
- return "flate: write error at offset " + strconv.Itoa64(e.Offset) + ": " + e.Error.String()
-}
-
-// Huffman decoder is based on
-// J. Brian Connell, ``A Huffman-Shannon-Fano Code,''
-// Proceedings of the IEEE, 61(7) (July 1973), pp 1046-1047.
-type huffmanDecoder struct {
- // min, max code length
- min, max int
-
- // limit[i] = largest code word of length i
- // Given code v of length n,
- // need more bits if v > limit[n].
- limit [maxCodeLen + 1]int
-
- // base[i] = smallest code word of length i - seq number
- base [maxCodeLen + 1]int
-
- // codes[seq number] = output code.
- // Given code v of length n, value is
- // codes[v - base[n]].
- codes []int
-}
-
-// Initialize Huffman decoding tables from array of code lengths.
-func (h *huffmanDecoder) init(bits []int) bool {
- // Count number of codes of each length,
- // compute min and max length.
- var count [maxCodeLen + 1]int
- var min, max int
- for _, n := range bits {
- if n == 0 {
- continue
- }
- if min == 0 || n < min {
- min = n
- }
- if n > max {
- max = n
- }
- count[n]++
- }
- if max == 0 {
- return false
- }
-
- h.min = min
- h.max = max
-
- // For each code range, compute
- // nextcode (first code of that length),
- // limit (last code of that length), and
- // base (offset from first code to sequence number).
- code := 0
- seq := 0
- var nextcode [maxCodeLen]int
- for i := min; i <= max; i++ {
- n := count[i]
- nextcode[i] = code
- h.base[i] = code - seq
- code += n
- seq += n
- h.limit[i] = code - 1
- code <<= 1
- }
-
- // Make array mapping sequence numbers to codes.
- if len(h.codes) < len(bits) {
- h.codes = make([]int, len(bits))
- }
- for i, n := range bits {
- if n == 0 {
- continue
- }
- code := nextcode[n]
- nextcode[n]++
- seq := code - h.base[n]
- h.codes[seq] = i
- }
- return true
-}
-
-// Hard-coded Huffman tables for DEFLATE algorithm.
-// See RFC 1951, section 3.2.6.
-var fixedHuffmanDecoder = huffmanDecoder{
- 7, 9,
- [maxCodeLen + 1]int{7: 23, 199, 511},
- [maxCodeLen + 1]int{7: 0, 24, 224},
- []int{
- // length 7: 256-279
- 256, 257, 258, 259, 260, 261, 262,
- 263, 264, 265, 266, 267, 268, 269,
- 270, 271, 272, 273, 274, 275, 276,
- 277, 278, 279,
-
- // length 8: 0-143
- 0, 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, 71,
- 72, 73, 74, 75, 76, 77, 78, 79, 80, 81,
- 82, 83, 84, 85, 86, 87, 88, 89, 90, 91,
- 92, 93, 94, 95, 96, 97, 98, 99, 100,
- 101, 102, 103, 104, 105, 106, 107, 108,
- 109, 110, 111, 112, 113, 114, 115, 116,
- 117, 118, 119, 120, 121, 122, 123, 124,
- 125, 126, 127, 128, 129, 130, 131, 132,
- 133, 134, 135, 136, 137, 138, 139, 140,
- 141, 142, 143,
-
- // length 8: 280-287
- 280, 281, 282, 283, 284, 285, 286, 287,
-
- // length 9: 144-255
- 144, 145, 146, 147, 148, 149, 150, 151,
- 152, 153, 154, 155, 156, 157, 158, 159,
- 160, 161, 162, 163, 164, 165, 166, 167,
- 168, 169, 170, 171, 172, 173, 174, 175,
- 176, 177, 178, 179, 180, 181, 182, 183,
- 184, 185, 186, 187, 188, 189, 190, 191,
- 192, 193, 194, 195, 196, 197, 198, 199,
- 200, 201, 202, 203, 204, 205, 206, 207,
- 208, 209, 210, 211, 212, 213, 214, 215,
- 216, 217, 218, 219, 220, 221, 222, 223,
- 224, 225, 226, 227, 228, 229, 230, 231,
- 232, 233, 234, 235, 236, 237, 238, 239,
- 240, 241, 242, 243, 244, 245, 246, 247,
- 248, 249, 250, 251, 252, 253, 254, 255,
- },
-}
-
-// The actual read interface needed by NewReader.
-// If the passed in io.Reader does not also have ReadByte,
-// the NewReader will introduce its own buffering.
-type Reader interface {
- io.Reader
- ReadByte() (c byte, err os.Error)
-}
-
-// Decompress state.
-type decompressor struct {
- // Input source.
- r Reader
- roffset int64
- woffset int64
-
- // Input bits, in top of b.
- b uint32
- nb uint
-
- // Huffman decoders for literal/length, distance.
- h1, h2 huffmanDecoder
-
- // Length arrays used to define Huffman codes.
- bits [maxLit + maxDist]int
- codebits [numCodes]int
-
- // Output history, buffer.
- hist [maxHist]byte
- hp int // current output position in buffer
- hw int // have written hist[0:hw] already
- hfull bool // buffer has filled at least once
-
- // Temporary buffer (avoids repeated allocation).
- buf [4]byte
-
- // Next step in the decompression,
- // and decompression state.
- step func(*decompressor)
- final bool
- err os.Error
- toRead []byte
- hl, hd *huffmanDecoder
- copyLen int
- copyDist int
-}
-
-func (f *decompressor) nextBlock() {
- if f.final {
- if f.hw != f.hp {
- f.flush((*decompressor).nextBlock)
- return
- }
- f.err = os.EOF
- return
- }
- for f.nb < 1+2 {
- if f.err = f.moreBits(); f.err != nil {
- return
- }
- }
- f.final = f.b&1 == 1
- f.b >>= 1
- typ := f.b & 3
- f.b >>= 2
- f.nb -= 1 + 2
- switch typ {
- case 0:
- f.dataBlock()
- case 1:
- // compressed, fixed Huffman tables
- f.hl = &fixedHuffmanDecoder
- f.hd = nil
- f.huffmanBlock()
- case 2:
- // compressed, dynamic Huffman tables
- if f.err = f.readHuffman(); f.err != nil {
- break
- }
- f.hl = &f.h1
- f.hd = &f.h2
- f.huffmanBlock()
- default:
- // 3 is reserved.
- f.err = CorruptInputError(f.roffset)
- }
-}
-
-func (f *decompressor) Read(b []byte) (int, os.Error) {
- for {
- if len(f.toRead) > 0 {
- n := copy(b, f.toRead)
- f.toRead = f.toRead[n:]
- return n, nil
- }
- if f.err != nil {
- return 0, f.err
- }
- f.step(f)
- }
- panic("unreachable")
-}
-
-func (f *decompressor) Close() os.Error {
- if f.err == os.EOF {
- return nil
- }
- return f.err
-}
-
-// RFC 1951 section 3.2.7.
-// Compression with dynamic Huffman codes
-
-var codeOrder = [...]int{16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15}
-
-func (f *decompressor) readHuffman() os.Error {
- // HLIT[5], HDIST[5], HCLEN[4].
- for f.nb < 5+5+4 {
- if err := f.moreBits(); err != nil {
- return err
- }
- }
- nlit := int(f.b&0x1F) + 257
- f.b >>= 5
- ndist := int(f.b&0x1F) + 1
- f.b >>= 5
- nclen := int(f.b&0xF) + 4
- f.b >>= 4
- f.nb -= 5 + 5 + 4
-
- // (HCLEN+4)*3 bits: code lengths in the magic codeOrder order.
- for i := 0; i < nclen; i++ {
- for f.nb < 3 {
- if err := f.moreBits(); err != nil {
- return err
- }
- }
- f.codebits[codeOrder[i]] = int(f.b & 0x7)
- f.b >>= 3
- f.nb -= 3
- }
- for i := nclen; i < len(codeOrder); i++ {
- f.codebits[codeOrder[i]] = 0
- }
- if !f.h1.init(f.codebits[0:]) {
- return CorruptInputError(f.roffset)
- }
-
- // HLIT + 257 code lengths, HDIST + 1 code lengths,
- // using the code length Huffman code.
- for i, n := 0, nlit+ndist; i < n; {
- x, err := f.huffSym(&f.h1)
- if err != nil {
- return err
- }
- if x < 16 {
- // Actual length.
- f.bits[i] = x
- i++
- continue
- }
- // Repeat previous length or zero.
- var rep int
- var nb uint
- var b int
- switch x {
- default:
- return InternalError("unexpected length code")
- case 16:
- rep = 3
- nb = 2
- if i == 0 {
- return CorruptInputError(f.roffset)
- }
- b = f.bits[i-1]
- case 17:
- rep = 3
- nb = 3
- b = 0
- case 18:
- rep = 11
- nb = 7
- b = 0
- }
- for f.nb < nb {
- if err := f.moreBits(); err != nil {
- return err
- }
- }
- rep += int(f.b & uint32(1<<nb-1))
- f.b >>= nb
- f.nb -= nb
- if i+rep > n {
- return CorruptInputError(f.roffset)
- }
- for j := 0; j < rep; j++ {
- f.bits[i] = b
- i++
- }
- }
-
- if !f.h1.init(f.bits[0:nlit]) || !f.h2.init(f.bits[nlit:nlit+ndist]) {
- return CorruptInputError(f.roffset)
- }
-
- return nil
-}
-
-// Decode a single Huffman block from f.
-// hl and hd are the Huffman states for the lit/length values
-// and the distance values, respectively. If hd == nil, using the
-// fixed distance encoding associated with fixed Huffman blocks.
-func (f *decompressor) huffmanBlock() {
- for {
- v, err := f.huffSym(f.hl)
- if err != nil {
- f.err = err
- return
- }
- var n uint // number of bits extra
- var length int
- switch {
- case v < 256:
- f.hist[f.hp] = byte(v)
- f.hp++
- if f.hp == len(f.hist) {
- // After the flush, continue this loop.
- f.flush((*decompressor).huffmanBlock)
- return
- }
- continue
- case v == 256:
- // Done with huffman block; read next block.
- f.step = (*decompressor).nextBlock
- return
- // otherwise, reference to older data
- case v < 265:
- length = v - (257 - 3)
- n = 0
- case v < 269:
- length = v*2 - (265*2 - 11)
- n = 1
- case v < 273:
- length = v*4 - (269*4 - 19)
- n = 2
- case v < 277:
- length = v*8 - (273*8 - 35)
- n = 3
- case v < 281:
- length = v*16 - (277*16 - 67)
- n = 4
- case v < 285:
- length = v*32 - (281*32 - 131)
- n = 5
- default:
- length = 258
- n = 0
- }
- if n > 0 {
- for f.nb < n {
- if err = f.moreBits(); err != nil {
- f.err = err
- return
- }
- }
- length += int(f.b & uint32(1<<n-1))
- f.b >>= n
- f.nb -= n
- }
-
- var dist int
- if f.hd == nil {
- for f.nb < 5 {
- if err = f.moreBits(); err != nil {
- f.err = err
- return
- }
- }
- dist = int(reverseByte[(f.b&0x1F)<<3])
- f.b >>= 5
- f.nb -= 5
- } else {
- if dist, err = f.huffSym(f.hd); err != nil {
- f.err = err
- return
- }
- }
-
- switch {
- case dist < 4:
- dist++
- case dist >= 30:
- f.err = CorruptInputError(f.roffset)
- return
- default:
- nb := uint(dist-2) >> 1
- // have 1 bit in bottom of dist, need nb more.
- extra := (dist & 1) << nb
- for f.nb < nb {
- if err = f.moreBits(); err != nil {
- f.err = err
- return
- }
- }
- extra |= int(f.b & uint32(1<<nb-1))
- f.b >>= nb
- f.nb -= nb
- dist = 1<<(nb+1) + 1 + extra
- }
-
- // Copy history[-dist:-dist+length] into output.
- if dist > len(f.hist) {
- f.err = InternalError("bad history distance")
- return
- }
-
- // No check on length; encoding can be prescient.
- if !f.hfull && dist > f.hp {
- f.err = CorruptInputError(f.roffset)
- return
- }
-
- p := f.hp - dist
- if p < 0 {
- p += len(f.hist)
- }
- for i := 0; i < length; i++ {
- f.hist[f.hp] = f.hist[p]
- f.hp++
- p++
- if f.hp == len(f.hist) {
- // After flush continue copying out of history.
- f.copyLen = length - (i + 1)
- f.copyDist = dist
- f.flush((*decompressor).copyHuff)
- return
- }
- if p == len(f.hist) {
- p = 0
- }
- }
- }
- panic("unreached")
-}
-
-func (f *decompressor) copyHuff() {
- length := f.copyLen
- dist := f.copyDist
- p := f.hp - dist
- if p < 0 {
- p += len(f.hist)
- }
- for i := 0; i < length; i++ {
- f.hist[f.hp] = f.hist[p]
- f.hp++
- p++
- if f.hp == len(f.hist) {
- f.copyLen = length - (i + 1)
- f.flush((*decompressor).copyHuff)
- return
- }
- if p == len(f.hist) {
- p = 0
- }
- }
-
- // Continue processing Huffman block.
- f.huffmanBlock()
-}
-
-// Copy a single uncompressed data block from input to output.
-func (f *decompressor) dataBlock() {
- // Uncompressed.
- // Discard current half-byte.
- f.nb = 0
- f.b = 0
-
- // Length then ones-complement of length.
- nr, err := io.ReadFull(f.r, f.buf[0:4])
- f.roffset += int64(nr)
- if err != nil {
- f.err = &ReadError{f.roffset, err}
- return
- }
- n := int(f.buf[0]) | int(f.buf[1])<<8
- nn := int(f.buf[2]) | int(f.buf[3])<<8
- if uint16(nn) != uint16(^n) {
- f.err = CorruptInputError(f.roffset)
- return
- }
-
- if n == 0 {
- // 0-length block means sync
- f.flush((*decompressor).nextBlock)
- return
- }
-
- f.copyLen = n
- f.copyData()
-}
-
-func (f *decompressor) copyData() {
- // Read f.dataLen bytes into history,
- // pausing for reads as history fills.
- n := f.copyLen
- for n > 0 {
- m := len(f.hist) - f.hp
- if m > n {
- m = n
- }
- m, err := io.ReadFull(f.r, f.hist[f.hp:f.hp+m])
- f.roffset += int64(m)
- if err != nil {
- f.err = &ReadError{f.roffset, err}
- return
- }
- n -= m
- f.hp += m
- if f.hp == len(f.hist) {
- f.copyLen = n
- f.flush((*decompressor).copyData)
- return
- }
- }
- f.step = (*decompressor).nextBlock
-}
-
-func (f *decompressor) setDict(dict []byte) {
- if len(dict) > len(f.hist) {
- // Will only remember the tail.
- dict = dict[len(dict)-len(f.hist):]
- }
-
- f.hp = copy(f.hist[:], dict)
- if f.hp == len(f.hist) {
- f.hp = 0
- f.hfull = true
- }
- f.hw = f.hp
-}
-
-func (f *decompressor) moreBits() os.Error {
- c, err := f.r.ReadByte()
- if err != nil {
- if err == os.EOF {
- err = io.ErrUnexpectedEOF
- }
- return err
- }
- f.roffset++
- f.b |= uint32(c) << f.nb
- f.nb += 8
- return nil
-}
-
-// Read the next Huffman-encoded symbol from f according to h.
-func (f *decompressor) huffSym(h *huffmanDecoder) (int, os.Error) {
- for n := uint(h.min); n <= uint(h.max); n++ {
- lim := h.limit[n]
- if lim == -1 {
- continue
- }
- for f.nb < n {
- if err := f.moreBits(); err != nil {
- return 0, err
- }
- }
- v := int(f.b & uint32(1<<n-1))
- v <<= 16 - n
- v = int(reverseByte[v>>8]) | int(reverseByte[v&0xFF])<<8 // reverse bits
- if v <= lim {
- f.b >>= n
- f.nb -= n
- return h.codes[v-h.base[n]], nil
- }
- }
- return 0, CorruptInputError(f.roffset)
-}
-
-// Flush any buffered output to the underlying writer.
-func (f *decompressor) flush(step func(*decompressor)) {
- f.toRead = f.hist[f.hw:f.hp]
- f.woffset += int64(f.hp - f.hw)
- f.hw = f.hp
- if f.hp == len(f.hist) {
- f.hp = 0
- f.hw = 0
- f.hfull = true
- }
- f.step = step
-}
-
-func makeReader(r io.Reader) Reader {
- if rr, ok := r.(Reader); ok {
- return rr
- }
- return bufio.NewReader(r)
-}
-
-// NewReader returns a new ReadCloser that can be used
-// to read the uncompressed version of r. It is the caller's
-// responsibility to call Close on the ReadCloser when
-// finished reading.
-func NewReader(r io.Reader) io.ReadCloser {
- var f decompressor
- f.r = makeReader(r)
- f.step = (*decompressor).nextBlock
- return &f
-}
-
-// NewReaderDict is like NewReader but initializes the reader
-// with a preset dictionary. The returned Reader behaves as if
-// the uncompressed data stream started with the given dictionary,
-// which has already been read. NewReaderDict is typically used
-// to read data compressed by NewWriterDict.
-func NewReaderDict(r io.Reader, dict []byte) io.ReadCloser {
- var f decompressor
- f.setDict(dict)
- f.r = makeReader(r)
- f.step = (*decompressor).nextBlock
- return &f
-}
generated by cgit v1.2.3 (git 2.39.1) at 2025-06-22 08:20:13 +0000