mirror of https://github.com/golang/go.git
Merge 161f02171c into 49cdf0c42e
This commit is contained in:
Klaus Post
GitHub
commit
ace2a9f115
|
|
@ -0,0 +1,277 @@
|
|||
// Copyright 2020 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.
|
||||
|
||||
//go:build generate
|
||||
// +build generate
|
||||
|
||||
//go:generate go run $GOFILE
|
||||
//go:generate go fmt inflate_gen.go
|
||||
|
||||
package main
|
||||
|
||||
import (
|
||||
"os"
|
||||
"strings"
|
||||
)
|
||||
|
||||
func main() {
|
||||
f, err := os.Create("inflate_gen.go")
|
||||
if err != nil {
|
||||
panic(err)
|
||||
}
|
||||
defer f.Close()
|
||||
types := []string{"*bytes.Buffer", "*bytes.Reader", "*bufio.Reader", "*strings.Reader", "Reader"}
|
||||
names := []string{"BytesBuffer", "BytesReader", "BufioReader", "StringsReader", "GenericReader"}
|
||||
imports := []string{"bytes", "bufio", "strings", "math/bits"}
|
||||
f.WriteString(`// Code generated by go generate gen_inflate.go. DO NOT EDIT.
|
||||
|
||||
package flate
|
||||
|
||||
import (
|
||||
`)
|
||||
|
||||
for _, imp := range imports {
|
||||
f.WriteString("\t\"" + imp + "\"\n")
|
||||
}
|
||||
f.WriteString(")\n\n")
|
||||
|
||||
template := `
|
||||
|
||||
// $FUNCNAME$ decodes a single Huffman block from f.
|
||||
// f.r must be a $TYPE$.
|
||||
// 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) $FUNCNAME$() {
|
||||
const (
|
||||
stateInit = iota // Zero value must be stateInit
|
||||
stateDict
|
||||
)
|
||||
fr := f.r.($TYPE$)
|
||||
|
||||
// Optimization. Compiler isn't smart enough to keep f.b, f.nb in registers,
|
||||
// but is smart enough to keep local variables in registers, so use nb and b,
|
||||
// dict reference and reassign b, nb back to f on return.
|
||||
fnb, fb, dict := f.nb, f.b, &f.dict
|
||||
switch f.stepState {
|
||||
case stateInit:
|
||||
goto readLiteral
|
||||
case stateDict:
|
||||
goto copyHistory
|
||||
}
|
||||
|
||||
readLiteral:
|
||||
// Read literal and/or (length, distance) according to RFC section 3.2.3.
|
||||
{
|
||||
var v int
|
||||
{
|
||||
// Inlined v, err := f.huffSym(f.hl)
|
||||
// Since a huffmanDecoder can be empty or be composed of a degenerate tree
|
||||
// with single element, huffSym must error on these two edge cases. In both
|
||||
// cases, the chunks slice will be 0 for the invalid sequence, leading it
|
||||
// satisfy the n == 0 check below.
|
||||
n := uint(f.hl.maxRead)
|
||||
for {
|
||||
for fnb < n {
|
||||
c, err := fr.ReadByte()
|
||||
if err != nil {
|
||||
f.b, f.nb = fb, fnb
|
||||
f.err = noEOF(err)
|
||||
return
|
||||
}
|
||||
f.roffset++
|
||||
fb |= uint32(c) << (fnb & 31)
|
||||
fnb += 8
|
||||
}
|
||||
chunk := f.hl.chunks[fb&(huffmanNumChunks-1)]
|
||||
n = uint(chunk & huffmanCountMask)
|
||||
if n > huffmanChunkBits {
|
||||
chunk = f.hl.links[chunk>>huffmanValueShift][(fb>>huffmanChunkBits)&f.hl.linkMask]
|
||||
n = uint(chunk & huffmanCountMask)
|
||||
}
|
||||
if n <= fnb {
|
||||
if n == 0 {
|
||||
f.b, f.nb = fb, fnb
|
||||
f.err = CorruptInputError(f.roffset)
|
||||
return
|
||||
}
|
||||
fb = fb >> (n & 31)
|
||||
fnb = fnb - n
|
||||
v = int(chunk >> huffmanValueShift)
|
||||
break
|
||||
}
|
||||
}
|
||||
}
|
||||
var length int
|
||||
switch {
|
||||
case v < 256:
|
||||
dict.writeByte(byte(v))
|
||||
if dict.availWrite() == 0 {
|
||||
f.toRead = dict.readFlush()
|
||||
f.step = (*decompressor).$FUNCNAME$
|
||||
f.stepState = stateInit
|
||||
f.b, f.nb = fb, fnb
|
||||
return
|
||||
}
|
||||
goto readLiteral
|
||||
case v == 256:
|
||||
f.b, f.nb = fb, fnb
|
||||
f.finishBlock()
|
||||
return
|
||||
// otherwise, reference to older data
|
||||
case v < 265:
|
||||
// No extra bits
|
||||
length = v - (257 - 3)
|
||||
case v < maxNumLit:
|
||||
val := decCodeToLen[(v - 257)]
|
||||
length = int(val.length) + 3
|
||||
n := uint(val.extra)
|
||||
for fnb < n {
|
||||
c, err := fr.ReadByte()
|
||||
if err != nil {
|
||||
f.b, f.nb = fb, fnb
|
||||
f.err = err
|
||||
return
|
||||
}
|
||||
f.roffset++
|
||||
fb |= uint32(c) << (fnb&31)
|
||||
fnb += 8
|
||||
}
|
||||
length += int(fb & bitMask32[n])
|
||||
fb >>= n & 31
|
||||
fnb -= n
|
||||
default:
|
||||
f.err = CorruptInputError(f.roffset)
|
||||
f.b, f.nb = fb, fnb
|
||||
return
|
||||
}
|
||||
var dist uint32
|
||||
if f.hd == nil {
|
||||
for fnb < 5 {
|
||||
c, err := fr.ReadByte()
|
||||
if err != nil {
|
||||
f.b, f.nb = fb, fnb
|
||||
f.err = err
|
||||
return
|
||||
}
|
||||
f.roffset++
|
||||
fb |= uint32(c) << (fnb&31)
|
||||
fnb += 8
|
||||
}
|
||||
dist = uint32(bits.Reverse8(uint8(fb & 0x1F << 3)))
|
||||
fb >>= 5
|
||||
fnb -= 5
|
||||
} else {
|
||||
// Since a huffmanDecoder can be empty or be composed of a degenerate tree
|
||||
// with single element, huffSym must error on these two edge cases. In both
|
||||
// cases, the chunks slice will be 0 for the invalid sequence, leading it
|
||||
// satisfy the n == 0 check below.
|
||||
n := uint(f.hd.maxRead)
|
||||
for {
|
||||
for fnb < n {
|
||||
c, err := fr.ReadByte()
|
||||
if err != nil {
|
||||
f.b, f.nb = fb, fnb
|
||||
f.err = noEOF(err)
|
||||
return
|
||||
}
|
||||
f.roffset++
|
||||
fb |= uint32(c) << (fnb & 31)
|
||||
fnb += 8
|
||||
}
|
||||
chunk := f.hd.chunks[fb&(huffmanNumChunks-1)]
|
||||
n = uint(chunk & huffmanCountMask)
|
||||
if n > huffmanChunkBits {
|
||||
chunk = f.hd.links[chunk>>huffmanValueShift][(fb>>huffmanChunkBits)&f.hd.linkMask]
|
||||
n = uint(chunk & huffmanCountMask)
|
||||
}
|
||||
if n <= fnb {
|
||||
if n == 0 {
|
||||
f.b, f.nb = fb, fnb
|
||||
f.err = CorruptInputError(f.roffset)
|
||||
return
|
||||
}
|
||||
fb = fb >> (n & 31)
|
||||
fnb = fnb - n
|
||||
dist = uint32(chunk >> huffmanValueShift)
|
||||
break
|
||||
}
|
||||
}
|
||||
}
|
||||
switch {
|
||||
case dist < 4:
|
||||
dist++
|
||||
case dist < maxNumDist:
|
||||
nb := uint(dist-2) >> 1
|
||||
// have 1 bit in bottom of dist, need nb more.
|
||||
extra := (dist & 1) << (nb & 31)
|
||||
for fnb < nb {
|
||||
c, err := fr.ReadByte()
|
||||
if err != nil {
|
||||
f.b, f.nb = fb, fnb
|
||||
f.err = err
|
||||
return
|
||||
}
|
||||
f.roffset++
|
||||
fb |= uint32(c) << (fnb&31)
|
||||
fnb += 8
|
||||
}
|
||||
extra |= fb & bitMask32[nb]
|
||||
fb >>= nb & 31
|
||||
fnb -= nb
|
||||
dist = 1<<((nb+1)&31) + 1 + extra
|
||||
default:
|
||||
f.b, f.nb = fb, fnb
|
||||
f.err = CorruptInputError(f.roffset)
|
||||
return
|
||||
}
|
||||
// No check on length; encoding can be prescient.
|
||||
if dist > uint32(dict.histSize()) {
|
||||
f.b, f.nb = fb, fnb
|
||||
f.err = CorruptInputError(f.roffset)
|
||||
return
|
||||
}
|
||||
f.copyLen, f.copyDist = length, int(dist)
|
||||
goto copyHistory
|
||||
}
|
||||
copyHistory:
|
||||
// Perform a backwards copy according to RFC section 3.2.3.
|
||||
{
|
||||
cnt := dict.tryWriteCopy(f.copyDist, f.copyLen)
|
||||
if cnt == 0 {
|
||||
cnt = dict.writeCopy(f.copyDist, f.copyLen)
|
||||
}
|
||||
f.copyLen -= cnt
|
||||
if dict.availWrite() == 0 || f.copyLen > 0 {
|
||||
f.toRead = dict.readFlush()
|
||||
f.step = (*decompressor).$FUNCNAME$ // We need to continue this work
|
||||
f.stepState = stateDict
|
||||
f.b, f.nb = fb, fnb
|
||||
return
|
||||
}
|
||||
goto readLiteral
|
||||
}
|
||||
// Not reached
|
||||
}
|
||||
|
||||
`
|
||||
for i, t := range types {
|
||||
s := strings.Replace(template, "$FUNCNAME$", "huffman"+names[i], -1)
|
||||
s = strings.Replace(s, "$TYPE$", t, -1)
|
||||
f.WriteString(s)
|
||||
}
|
||||
f.WriteString("func (f *decompressor) huffmanBlockDecoder() func() {\n")
|
||||
f.WriteString("\tswitch f.r.(type) {\n")
|
||||
for i, t := range types {
|
||||
f.WriteString("\t\tcase " + t + ":\n")
|
||||
f.WriteString("\t\t\treturn f.huffman" + names[i] + "\n")
|
||||
}
|
||||
f.WriteString("\t\tdefault:\n")
|
||||
f.WriteString("\t\t\treturn f.huffmanGenericReader")
|
||||
f.WriteString("\t}\n}\n")
|
||||
}
|
||||
|
|
@ -16,7 +16,8 @@ import (
|
|||
)
|
||||
|
||||
const (
|
||||
maxCodeLen = 16 // max length of Huffman code
|
||||
maxCodeLen = 16 // max length of Huffman code
|
||||
maxCodeLenMask = 15 // mask for max length of Huffman code
|
||||
// The next three numbers come from the RFC section 3.2.7, with the
|
||||
// additional proviso in section 3.2.5 which implies that distance codes
|
||||
// 30 and 31 should never occur in compressed data.
|
||||
|
|
@ -29,6 +30,21 @@ const (
|
|||
var fixedOnce sync.Once
|
||||
var fixedHuffmanDecoder huffmanDecoder
|
||||
|
||||
var bitMask32 = [32]uint32{
|
||||
0, 1, 3, 7, 0xF, 0x1F, 0x3F, 0x7F, 0xFF,
|
||||
0x1FF, 0x3FF, 0x7FF, 0xFFF, 0x1FFF, 0x3FFF, 0x7FFF, 0xFFFF,
|
||||
0x1ffff, 0x3ffff, 0x7FFFF, 0xfFFFF, 0x1fFFFF, 0x3fFFFF, 0x7fFFFF, 0xffFFFF,
|
||||
0x1ffFFFF, 0x3ffFFFF, 0x7ffFFFF, 0xfffFFFF, 0x1fffFFFF, 0x3fffFFFF, 0x7fffFFFF,
|
||||
} // up to 32 bits
|
||||
|
||||
// Value of length - 3 and extra bits.
|
||||
type lengthExtra struct {
|
||||
length, extra uint8
|
||||
}
|
||||
|
||||
// decCodeToLen contains fast lookup of each length and the number of extra bits.
|
||||
var decCodeToLen = [32]lengthExtra{{length: 0x0, extra: 0x0}, {length: 0x1, extra: 0x0}, {length: 0x2, extra: 0x0}, {length: 0x3, extra: 0x0}, {length: 0x4, extra: 0x0}, {length: 0x5, extra: 0x0}, {length: 0x6, extra: 0x0}, {length: 0x7, extra: 0x0}, {length: 0x8, extra: 0x1}, {length: 0xa, extra: 0x1}, {length: 0xc, extra: 0x1}, {length: 0xe, extra: 0x1}, {length: 0x10, extra: 0x2}, {length: 0x14, extra: 0x2}, {length: 0x18, extra: 0x2}, {length: 0x1c, extra: 0x2}, {length: 0x20, extra: 0x3}, {length: 0x28, extra: 0x3}, {length: 0x30, extra: 0x3}, {length: 0x38, extra: 0x3}, {length: 0x40, extra: 0x4}, {length: 0x50, extra: 0x4}, {length: 0x60, extra: 0x4}, {length: 0x70, extra: 0x4}, {length: 0x80, extra: 0x5}, {length: 0xa0, extra: 0x5}, {length: 0xc0, extra: 0x5}, {length: 0xe0, extra: 0x5}, {length: 0xff, extra: 0x0}, {length: 0x0, extra: 0x0}, {length: 0x0, extra: 0x0}, {length: 0x0, extra: 0x0}}
|
||||
|
||||
// A CorruptInputError reports the presence of corrupt input at a given offset.
|
||||
type CorruptInputError int64
|
||||
|
||||
|
|
@ -102,10 +118,10 @@ const (
|
|||
)
|
||||
|
||||
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
|
||||
maxRead int // the maximum number of bits we can read and not overread
|
||||
chunks *[huffmanNumChunks]uint16 // chunks as described above
|
||||
links [][]uint16 // overflow links
|
||||
linkMask uint32 // mask the width of the link table
|
||||
}
|
||||
|
||||
// Initialize Huffman decoding tables from array of code lengths.
|
||||
|
|
@ -119,12 +135,15 @@ func (h *huffmanDecoder) init(lengths []int) bool {
|
|||
// development to supplement the currently ad-hoc unit tests.
|
||||
const sanity = false
|
||||
|
||||
if h.min != 0 {
|
||||
*h = huffmanDecoder{}
|
||||
if h.chunks == nil {
|
||||
h.chunks = &[huffmanNumChunks]uint16{}
|
||||
}
|
||||
if h.maxRead != 0 {
|
||||
*h = huffmanDecoder{chunks: h.chunks, links: h.links}
|
||||
}
|
||||
|
||||
// Count number of codes of each length,
|
||||
// compute min and max length.
|
||||
// compute maxRead and max length.
|
||||
var count [maxCodeLen]int
|
||||
var min, max int
|
||||
for _, n := range lengths {
|
||||
|
|
@ -137,7 +156,7 @@ func (h *huffmanDecoder) init(lengths []int) bool {
|
|||
if n > max {
|
||||
max = n
|
||||
}
|
||||
count[n]++
|
||||
count[n&maxCodeLenMask]++
|
||||
}
|
||||
|
||||
// Empty tree. The decompressor.huffSym function will fail later if the tree
|
||||
|
|
@ -155,8 +174,8 @@ func (h *huffmanDecoder) init(lengths []int) bool {
|
|||
var nextcode [maxCodeLen]int
|
||||
for i := min; i <= max; i++ {
|
||||
code <<= 1
|
||||
nextcode[i] = code
|
||||
code += count[i]
|
||||
nextcode[i&maxCodeLenMask] = code
|
||||
code += count[i&maxCodeLenMask]
|
||||
}
|
||||
|
||||
// Check that the coding is complete (i.e., that we've
|
||||
|
|
@ -168,14 +187,23 @@ func (h *huffmanDecoder) init(lengths []int) bool {
|
|||
return false
|
||||
}
|
||||
|
||||
h.min = min
|
||||
h.maxRead = min
|
||||
chunks := h.chunks[:]
|
||||
for i := range chunks {
|
||||
chunks[i] = 0
|
||||
}
|
||||
|
||||
if max > huffmanChunkBits {
|
||||
numLinks := 1 << (uint(max) - huffmanChunkBits)
|
||||
h.linkMask = uint32(numLinks - 1)
|
||||
|
||||
// create link tables
|
||||
link := nextcode[huffmanChunkBits+1] >> 1
|
||||
h.links = make([][]uint32, huffmanNumChunks-link)
|
||||
if cap(h.links) < huffmanNumChunks-link {
|
||||
h.links = make([][]uint16, huffmanNumChunks-link)
|
||||
} else {
|
||||
h.links = h.links[:huffmanNumChunks-link]
|
||||
}
|
||||
for j := uint(link); j < huffmanNumChunks; j++ {
|
||||
reverse := int(bits.Reverse16(uint16(j)))
|
||||
reverse >>= uint(16 - huffmanChunkBits)
|
||||
|
|
@ -183,9 +211,16 @@ func (h *huffmanDecoder) init(lengths []int) bool {
|
|||
if sanity && h.chunks[reverse] != 0 {
|
||||
panic("impossible: overwriting existing chunk")
|
||||
}
|
||||
h.chunks[reverse] = uint32(off<<huffmanValueShift | (huffmanChunkBits + 1))
|
||||
h.links[off] = make([]uint32, numLinks)
|
||||
h.chunks[reverse] = uint16(off<<huffmanValueShift | (huffmanChunkBits + 1))
|
||||
if cap(h.links[off]) < numLinks {
|
||||
h.links[off] = make([]uint16, numLinks)
|
||||
} else {
|
||||
links := h.links[off][:0]
|
||||
h.links[off] = links[:numLinks]
|
||||
}
|
||||
}
|
||||
} else {
|
||||
h.links = h.links[:0]
|
||||
}
|
||||
|
||||
for i, n := range lengths {
|
||||
|
|
@ -194,7 +229,7 @@ func (h *huffmanDecoder) init(lengths []int) bool {
|
|||
}
|
||||
code := nextcode[n]
|
||||
nextcode[n]++
|
||||
chunk := uint32(i<<huffmanValueShift | n)
|
||||
chunk := uint16(i<<huffmanValueShift | n)
|
||||
reverse := int(bits.Reverse16(uint16(code)))
|
||||
reverse >>= uint(16 - n)
|
||||
if n <= huffmanChunkBits {
|
||||
|
|
@ -270,10 +305,6 @@ type decompressor struct {
|
|||
rBuf *bufio.Reader // created if provided io.Reader does not implement io.ByteReader
|
||||
roffset int64
|
||||
|
||||
// Input bits, in top of b.
|
||||
b uint32
|
||||
nb uint
|
||||
|
||||
// Huffman decoders for literal/length, distance.
|
||||
h1, h2 huffmanDecoder
|
||||
|
||||
|
|
@ -284,19 +315,24 @@ type decompressor struct {
|
|||
// Output history, buffer.
|
||||
dict dictDecoder
|
||||
|
||||
// Temporary buffer (avoids repeated allocation).
|
||||
buf [4]byte
|
||||
|
||||
// Next step in the decompression,
|
||||
// and decompression state.
|
||||
step func(*decompressor)
|
||||
stepState int
|
||||
final bool
|
||||
err error
|
||||
toRead []byte
|
||||
hl, hd *huffmanDecoder
|
||||
copyLen int
|
||||
copyDist int
|
||||
|
||||
// Temporary buffer (avoids repeated allocation).
|
||||
buf [4]byte
|
||||
|
||||
// Input bits, in top of b.
|
||||
b uint32
|
||||
|
||||
nb uint
|
||||
final bool
|
||||
}
|
||||
|
||||
func (f *decompressor) nextBlock() {
|
||||
|
|
@ -317,7 +353,7 @@ func (f *decompressor) nextBlock() {
|
|||
// compressed, fixed Huffman tables
|
||||
f.hl = &fixedHuffmanDecoder
|
||||
f.hd = nil
|
||||
f.huffmanBlock()
|
||||
f.huffmanBlockDecoder()()
|
||||
case 2:
|
||||
// compressed, dynamic Huffman tables
|
||||
if f.err = f.readHuffman(); f.err != nil {
|
||||
|
|
@ -325,7 +361,7 @@ func (f *decompressor) nextBlock() {
|
|||
}
|
||||
f.hl = &f.h1
|
||||
f.hd = &f.h2
|
||||
f.huffmanBlock()
|
||||
f.huffmanBlockDecoder()()
|
||||
default:
|
||||
// 3 is reserved.
|
||||
f.err = CorruptInputError(f.roffset)
|
||||
|
|
@ -461,181 +497,51 @@ func (f *decompressor) readHuffman() error {
|
|||
return CorruptInputError(f.roffset)
|
||||
}
|
||||
|
||||
// As an optimization, we can initialize the min bits to read at a time
|
||||
// As an optimization, we can initialize the maxRead bits to read at a time
|
||||
// for the HLIT tree to the length of the EOB marker since we know that
|
||||
// every block must terminate with one. This preserves the property that
|
||||
// we never read any extra bytes after the end of the DEFLATE stream.
|
||||
if f.h1.min < f.bits[endBlockMarker] {
|
||||
f.h1.min = f.bits[endBlockMarker]
|
||||
if f.h1.maxRead < f.bits[endBlockMarker] {
|
||||
f.h1.maxRead = f.bits[endBlockMarker]
|
||||
}
|
||||
if !f.final {
|
||||
// If not the final block, the smallest block possible is
|
||||
// a predefined table, BTYPE=01, with a single EOB marker.
|
||||
// This will take up 3 + 7 bits.
|
||||
f.h1.maxRead += 10
|
||||
}
|
||||
|
||||
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() {
|
||||
const (
|
||||
stateInit = iota // Zero value must be stateInit
|
||||
stateDict
|
||||
)
|
||||
|
||||
switch f.stepState {
|
||||
case stateInit:
|
||||
goto readLiteral
|
||||
case stateDict:
|
||||
goto copyHistory
|
||||
}
|
||||
|
||||
readLiteral:
|
||||
// Read literal and/or (length, distance) according to RFC section 3.2.3.
|
||||
{
|
||||
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.dict.writeByte(byte(v))
|
||||
if f.dict.availWrite() == 0 {
|
||||
f.toRead = f.dict.readFlush()
|
||||
f.step = (*decompressor).huffmanBlock
|
||||
f.stepState = stateInit
|
||||
return
|
||||
}
|
||||
goto readLiteral
|
||||
case v == 256:
|
||||
f.finishBlock()
|
||||
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
|
||||
case v < maxNumLit:
|
||||
length = 258
|
||||
n = 0
|
||||
default:
|
||||
f.err = CorruptInputError(f.roffset)
|
||||
return
|
||||
}
|
||||
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(bits.Reverse8(uint8(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 < maxNumDist:
|
||||
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
|
||||
default:
|
||||
f.err = CorruptInputError(f.roffset)
|
||||
return
|
||||
}
|
||||
|
||||
// No check on length; encoding can be prescient.
|
||||
if dist > f.dict.histSize() {
|
||||
f.err = CorruptInputError(f.roffset)
|
||||
return
|
||||
}
|
||||
|
||||
f.copyLen, f.copyDist = length, dist
|
||||
goto copyHistory
|
||||
}
|
||||
|
||||
copyHistory:
|
||||
// Perform a backwards copy according to RFC section 3.2.3.
|
||||
{
|
||||
cnt := f.dict.tryWriteCopy(f.copyDist, f.copyLen)
|
||||
if cnt == 0 {
|
||||
cnt = f.dict.writeCopy(f.copyDist, f.copyLen)
|
||||
}
|
||||
f.copyLen -= cnt
|
||||
|
||||
if f.dict.availWrite() == 0 || f.copyLen > 0 {
|
||||
f.toRead = f.dict.readFlush()
|
||||
f.step = (*decompressor).huffmanBlock // We need to continue this work
|
||||
f.stepState = stateDict
|
||||
return
|
||||
}
|
||||
goto readLiteral
|
||||
}
|
||||
}
|
||||
|
||||
// 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
|
||||
// Discard current partial byte.
|
||||
left := (f.nb) & 7
|
||||
f.nb -= left
|
||||
f.b >>= left
|
||||
|
||||
offBytes := f.nb >> 3
|
||||
// Unfilled values will be overwritten.
|
||||
f.buf[0] = uint8(f.b)
|
||||
f.buf[1] = uint8(f.b >> 8)
|
||||
f.buf[2] = uint8(f.b >> 16)
|
||||
f.buf[3] = uint8(f.b >> 24)
|
||||
|
||||
f.roffset += int64(offBytes)
|
||||
f.nb, f.b = 0, 0
|
||||
|
||||
// Length then ones-complement of length.
|
||||
nr, err := io.ReadFull(f.r, f.buf[0:4])
|
||||
nr, err := io.ReadFull(f.r, f.buf[offBytes:4])
|
||||
f.roffset += int64(nr)
|
||||
if err != nil {
|
||||
f.err = noEOF(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) {
|
||||
n := uint16(f.buf[0]) | uint16(f.buf[1])<<8
|
||||
nn := uint16(f.buf[2]) | uint16(f.buf[3])<<8
|
||||
if nn != ^n {
|
||||
f.err = CorruptInputError(f.roffset)
|
||||
return
|
||||
}
|
||||
|
|
@ -646,7 +552,7 @@ func (f *decompressor) dataBlock() {
|
|||
return
|
||||
}
|
||||
|
||||
f.copyLen = n
|
||||
f.copyLen = int(n)
|
||||
f.copyData()
|
||||
}
|
||||
|
||||
|
|
@ -710,7 +616,7 @@ func (f *decompressor) huffSym(h *huffmanDecoder) (int, error) {
|
|||
// with single element, huffSym must error on these two edge cases. In both
|
||||
// cases, the chunks slice will be 0 for the invalid sequence, leading it
|
||||
// satisfy the n == 0 check below.
|
||||
n := uint(h.min)
|
||||
n := uint(h.maxRead)
|
||||
// Optimization. Compiler isn't smart enough to keep f.b,f.nb in registers,
|
||||
// but is smart enough to keep local variables in registers, so use nb and b,
|
||||
// inline call to moreBits and reassign b,nb back to f on return.
|
||||
|
|
@ -788,6 +694,8 @@ func (f *decompressor) Reset(r io.Reader, dict []byte) error {
|
|||
rBuf: f.rBuf,
|
||||
bits: f.bits,
|
||||
codebits: f.codebits,
|
||||
h1: f.h1,
|
||||
h2: f.h2,
|
||||
dict: f.dict,
|
||||
step: (*decompressor).nextBlock,
|
||||
}
|
||||
|
|
|
|||
File diff suppressed because it is too large
Load Diff
|
|
@ -51,10 +51,14 @@ func BenchmarkDecode(b *testing.B) {
|
|||
w.Close()
|
||||
buf1 := compressed.Bytes()
|
||||
buf0, compressed, w = nil, nil, nil
|
||||
src := bytes.NewReader(buf1)
|
||||
dec := NewReader(src)
|
||||
runtime.GC()
|
||||
b.StartTimer()
|
||||
for i := 0; i < b.N; i++ {
|
||||
io.Copy(io.Discard, NewReader(bytes.NewReader(buf1)))
|
||||
src.Reset(buf1)
|
||||
dec.(Resetter).Reset(src, nil)
|
||||
io.Copy(io.Discard, dec)
|
||||
}
|
||||
})
|
||||
}
|
||||
|
|
|
|||
Loading…
Reference in New Issue