mirror of
https://github.com/autc04/Retro68.git
synced 2024-12-04 16:50:57 +00:00
740 lines
16 KiB
Go
740 lines
16 KiB
Go
// 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 gen.go -output fixedhuff.go
|
|
|
|
// 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"
|
|
"strconv"
|
|
)
|
|
|
|
const (
|
|
maxCodeLen = 16 // max length of Huffman code
|
|
maxHist = 32768 // max history required
|
|
// The next three numbers come from the RFC, section 3.2.7.
|
|
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) Error() string {
|
|
return "flate: corrupt input before offset " + strconv.FormatInt(int64(e), 10)
|
|
}
|
|
|
|
// An InternalError reports an error in the flate code itself.
|
|
type InternalError string
|
|
|
|
func (e InternalError) Error() 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
|
|
Err error // error returned by underlying Read
|
|
}
|
|
|
|
func (e *ReadError) Error() string {
|
|
return "flate: read error at offset " + strconv.FormatInt(e.Offset, 10) + ": " + e.Err.Error()
|
|
}
|
|
|
|
// A WriteError reports an error encountered while writing output.
|
|
type WriteError struct {
|
|
Offset int64 // byte offset where error occurred
|
|
Err error // error returned by underlying Write
|
|
}
|
|
|
|
func (e *WriteError) Error() string {
|
|
return "flate: write error at offset " + strconv.FormatInt(e.Offset, 10) + ": " + e.Err.Error()
|
|
}
|
|
|
|
// Resetter resets a ReadCloser returned by NewReader or NewReaderDict to
|
|
// to switch to a new underlying Reader. This permits reusing a ReadCloser
|
|
// instead of allocating a new one.
|
|
type Resetter interface {
|
|
// Reset discards any buffered data and resets the Resetter as if it was
|
|
// newly initialized with the given reader.
|
|
Reset(r io.Reader, dict []byte) error
|
|
}
|
|
|
|
// Note that much of the implementation of huffmanDecoder is also copied
|
|
// into gen.go (in package main) for the purpose of precomputing the
|
|
// fixed huffman tables so they can be included statically.
|
|
|
|
// The data structure for decoding Huffman tables is based on that of
|
|
// zlib. There is a lookup table of a fixed bit width (huffmanChunkBits),
|
|
// For codes smaller than the table width, there are multiple entries
|
|
// (each combination of trailing bits has the same value). For codes
|
|
// larger than the table width, the table contains a link to an overflow
|
|
// table. The width of each entry in the link table is the maximum code
|
|
// size minus the chunk width.
|
|
|
|
// Note that you can do a lookup in the table even without all bits
|
|
// filled. Since the extra bits are zero, and the DEFLATE Huffman codes
|
|
// have the property that shorter codes come before longer ones, the
|
|
// bit length estimate in the result is a lower bound on the actual
|
|
// number of bits.
|
|
|
|
// chunk & 15 is number of bits
|
|
// chunk >> 4 is value, including table link
|
|
|
|
const (
|
|
huffmanChunkBits = 9
|
|
huffmanNumChunks = 1 << huffmanChunkBits
|
|
huffmanCountMask = 15
|
|
huffmanValueShift = 4
|
|
)
|
|
|
|
type huffmanDecoder struct {
|
|
min int // the minimum code length
|
|
chunks [huffmanNumChunks]uint32 // chunks as described above
|
|
links [][]uint32 // overflow links
|
|
linkMask uint32 // mask the width of the link table
|
|
}
|
|
|
|
// Initialize Huffman decoding tables from array of code lengths.
|
|
func (h *huffmanDecoder) init(bits []int) bool {
|
|
if h.min != 0 {
|
|
*h = huffmanDecoder{}
|
|
}
|
|
|
|
// Count number of codes of each length,
|
|
// compute min and max length.
|
|
var count [maxCodeLen]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
|
|
var linkBits uint
|
|
var numLinks int
|
|
if max > huffmanChunkBits {
|
|
linkBits = uint(max) - huffmanChunkBits
|
|
numLinks = 1 << linkBits
|
|
h.linkMask = uint32(numLinks - 1)
|
|
}
|
|
code := 0
|
|
var nextcode [maxCodeLen]int
|
|
for i := min; i <= max; i++ {
|
|
if i == huffmanChunkBits+1 {
|
|
// create link tables
|
|
link := code >> 1
|
|
if huffmanNumChunks < link {
|
|
return false
|
|
}
|
|
h.links = make([][]uint32, huffmanNumChunks-link)
|
|
for j := uint(link); j < huffmanNumChunks; j++ {
|
|
reverse := int(reverseByte[j>>8]) | int(reverseByte[j&0xff])<<8
|
|
reverse >>= uint(16 - huffmanChunkBits)
|
|
off := j - uint(link)
|
|
h.chunks[reverse] = uint32(off<<huffmanValueShift + uint(i))
|
|
h.links[off] = make([]uint32, 1<<linkBits)
|
|
}
|
|
}
|
|
n := count[i]
|
|
nextcode[i] = code
|
|
code += n
|
|
code <<= 1
|
|
}
|
|
|
|
for i, n := range bits {
|
|
if n == 0 {
|
|
continue
|
|
}
|
|
code := nextcode[n]
|
|
nextcode[n]++
|
|
chunk := uint32(i<<huffmanValueShift | n)
|
|
reverse := int(reverseByte[code>>8]) | int(reverseByte[code&0xff])<<8
|
|
reverse >>= uint(16 - n)
|
|
if n <= huffmanChunkBits {
|
|
for off := reverse; off < huffmanNumChunks; off += 1 << uint(n) {
|
|
h.chunks[off] = chunk
|
|
}
|
|
} else {
|
|
value := h.chunks[reverse&(huffmanNumChunks-1)] >> huffmanValueShift
|
|
if value >= uint32(len(h.links)) {
|
|
return false
|
|
}
|
|
linktab := h.links[value]
|
|
reverse >>= huffmanChunkBits
|
|
for off := reverse; off < numLinks; off += 1 << uint(n-huffmanChunkBits) {
|
|
linktab[off] = chunk
|
|
}
|
|
}
|
|
}
|
|
return true
|
|
}
|
|
|
|
// 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
|
|
io.ByteReader
|
|
}
|
|
|
|
// 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 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 = io.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, 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)
|
|
}
|
|
}
|
|
|
|
func (f *decompressor) Close() error {
|
|
if f.err == io.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() 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
|
|
if nlit > maxLit {
|
|
return CorruptInputError(f.roffset)
|
|
}
|
|
f.b >>= 5
|
|
ndist := int(f.b&0x1F) + 1
|
|
// maxDist is 32, so ndist is always valid.
|
|
f.b >>= 5
|
|
nclen := int(f.b&0xF) + 4
|
|
// numCodes is 19, so nclen is always valid.
|
|
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
|
|
}
|
|
|
|
f.copyLen, f.copyDist = length, dist
|
|
if f.copyHist() {
|
|
return
|
|
}
|
|
}
|
|
}
|
|
|
|
// copyHist copies f.copyLen bytes from f.hist (f.copyDist bytes ago) to itself.
|
|
// It reports whether the f.hist buffer is full.
|
|
func (f *decompressor) copyHist() bool {
|
|
p := f.hp - f.copyDist
|
|
if p < 0 {
|
|
p += len(f.hist)
|
|
}
|
|
for f.copyLen > 0 {
|
|
n := f.copyLen
|
|
if x := len(f.hist) - f.hp; n > x {
|
|
n = x
|
|
}
|
|
if x := len(f.hist) - p; n > x {
|
|
n = x
|
|
}
|
|
forwardCopy(f.hist[:], f.hp, p, n)
|
|
p += n
|
|
f.hp += n
|
|
f.copyLen -= n
|
|
if f.hp == len(f.hist) {
|
|
// After flush continue copying out of history.
|
|
f.flush((*decompressor).copyHuff)
|
|
return true
|
|
}
|
|
if p == len(f.hist) {
|
|
p = 0
|
|
}
|
|
}
|
|
return false
|
|
}
|
|
|
|
func (f *decompressor) copyHuff() {
|
|
if f.copyHist() {
|
|
return
|
|
}
|
|
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()
|
|
}
|
|
|
|
// copyData copies f.copyLen bytes from the underlying reader into f.hist.
|
|
// It pauses for reads when f.hist is full.
|
|
func (f *decompressor) copyData() {
|
|
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() error {
|
|
c, err := f.r.ReadByte()
|
|
if err != nil {
|
|
if err == io.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, error) {
|
|
n := uint(h.min)
|
|
for {
|
|
for f.nb < n {
|
|
if err := f.moreBits(); err != nil {
|
|
return 0, err
|
|
}
|
|
}
|
|
chunk := h.chunks[f.b&(huffmanNumChunks-1)]
|
|
n = uint(chunk & huffmanCountMask)
|
|
if n > huffmanChunkBits {
|
|
chunk = h.links[chunk>>huffmanValueShift][(f.b>>huffmanChunkBits)&h.linkMask]
|
|
n = uint(chunk & huffmanCountMask)
|
|
if n == 0 {
|
|
f.err = CorruptInputError(f.roffset)
|
|
return 0, f.err
|
|
}
|
|
}
|
|
if n <= f.nb {
|
|
f.b >>= n
|
|
f.nb -= n
|
|
return int(chunk >> huffmanValueShift), nil
|
|
}
|
|
}
|
|
}
|
|
|
|
// 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)
|
|
}
|
|
|
|
func (f *decompressor) Reset(r io.Reader, dict []byte) error {
|
|
*f = decompressor{
|
|
r: makeReader(r),
|
|
bits: f.bits,
|
|
codebits: f.codebits,
|
|
hist: f.hist,
|
|
step: (*decompressor).nextBlock,
|
|
}
|
|
if dict != nil {
|
|
f.setDict(dict)
|
|
}
|
|
return nil
|
|
}
|
|
|
|
// NewReader returns a new ReadCloser that can be used
|
|
// to read the uncompressed version of r.
|
|
// If r does not also implement io.ByteReader,
|
|
// the decompressor may read more data than necessary from r.
|
|
// It is the caller's responsibility to call Close on the ReadCloser
|
|
// when finished reading.
|
|
//
|
|
// The ReadCloser returned by NewReader also implements Resetter.
|
|
func NewReader(r io.Reader) io.ReadCloser {
|
|
var f decompressor
|
|
f.bits = new([maxLit + maxDist]int)
|
|
f.codebits = new([numCodes]int)
|
|
f.r = makeReader(r)
|
|
f.hist = new([maxHist]byte)
|
|
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.
|
|
//
|
|
// The ReadCloser returned by NewReader also implements Resetter.
|
|
func NewReaderDict(r io.Reader, dict []byte) io.ReadCloser {
|
|
var f decompressor
|
|
f.r = makeReader(r)
|
|
f.hist = new([maxHist]byte)
|
|
f.bits = new([maxLit + maxDist]int)
|
|
f.codebits = new([numCodes]int)
|
|
f.step = (*decompressor).nextBlock
|
|
f.setDict(dict)
|
|
return &f
|
|
}
|