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- package flate
- import (
- "bufio"
- "io"
- "strconv"
- "sync"
- )
- const (
- maxCodeLen = 16
-
-
-
- maxNumLit = 286
- maxNumDist = 30
- numCodes = 19
- )
- var fixedOnce sync.Once
- var fixedHuffmanDecoder huffmanDecoder
- type CorruptInputError int64
- func (e CorruptInputError) Error() string {
- return "flate: corrupt input before offset " + strconv.FormatInt(int64(e), 10)
- }
- type InternalError string
- func (e InternalError) Error() string { return "flate: internal error: " + string(e) }
- type ReadError struct {
- Offset int64
- Err error
- }
- func (e *ReadError) Error() string {
- return "flate: read error at offset " + strconv.FormatInt(e.Offset, 10) + ": " + e.Err.Error()
- }
- type WriteError struct {
- Offset int64
- Err error
- }
- func (e *WriteError) Error() string {
- return "flate: write error at offset " + strconv.FormatInt(e.Offset, 10) + ": " + e.Err.Error()
- }
- type Resetter interface {
-
-
- Reset(r io.Reader, dict []byte) error
- }
- const (
- huffmanChunkBits = 9
- huffmanNumChunks = 1 << huffmanChunkBits
- huffmanCountMask = 15
- huffmanValueShift = 4
- )
- type huffmanDecoder struct {
- min int
- chunks [huffmanNumChunks]uint32
- links [][]uint32
- linkMask uint32
- }
- func (h *huffmanDecoder) init(bits []int) bool {
-
-
-
- const sanity = false
- if h.min != 0 {
- *h = huffmanDecoder{}
- }
-
-
- 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 true
- }
- code := 0
- var nextcode [maxCodeLen]int
- for i := min; i <= max; i++ {
- code <<= 1
- nextcode[i] = code
- code += count[i]
- }
-
-
-
-
-
- if code != 1<<uint(max) && !(code == 1 && max == 1) {
- return false
- }
- h.min = min
- if max > huffmanChunkBits {
- numLinks := 1 << (uint(max) - huffmanChunkBits)
- h.linkMask = uint32(numLinks - 1)
-
- link := nextcode[huffmanChunkBits+1] >> 1
- 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)
- 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)
- }
- }
- 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 < len(h.chunks); off += 1 << uint(n) {
-
-
-
-
-
- if sanity && h.chunks[off] != 0 {
- panic("impossible: overwriting existing chunk")
- }
- h.chunks[off] = chunk
- }
- } else {
- j := reverse & (huffmanNumChunks - 1)
- if sanity && h.chunks[j]&huffmanCountMask != huffmanChunkBits+1 {
-
-
- panic("impossible: not an indirect chunk")
- }
- value := h.chunks[j] >> huffmanValueShift
- linktab := h.links[value]
- reverse >>= huffmanChunkBits
- for off := reverse; off < len(linktab); off += 1 << uint(n-huffmanChunkBits) {
- if sanity && linktab[off] != 0 {
- panic("impossible: overwriting existing chunk")
- }
- linktab[off] = chunk
- }
- }
- }
- if sanity {
-
-
-
- for i, chunk := range h.chunks {
- if chunk == 0 {
-
-
-
- if code == 1 && i%2 == 1 {
- continue
- }
- panic("impossible: missing chunk")
- }
- }
- for _, linktab := range h.links {
- for _, chunk := range linktab {
- if chunk == 0 {
- panic("impossible: missing chunk")
- }
- }
- }
- }
- return true
- }
- type Reader interface {
- io.Reader
- io.ByteReader
- }
- type decompressor struct {
-
- r Reader
- roffset int64
-
- b uint32
- nb uint
-
- h1, h2 huffmanDecoder
-
- bits *[maxNumLit + maxNumDist]int
- codebits *[numCodes]int
-
- dict dictDecoder
-
- buf [4]byte
-
-
- step func(*decompressor)
- stepState int
- final bool
- err error
- toRead []byte
- hl, hd *huffmanDecoder
- copyLen int
- copyDist int
- }
- func (f *decompressor) nextBlock() {
- 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:
-
- f.hl = &fixedHuffmanDecoder
- f.hd = nil
- f.huffmanBlock()
- case 2:
-
- if f.err = f.readHuffman(); f.err != nil {
- break
- }
- f.hl = &f.h1
- f.hd = &f.h2
- f.huffmanBlock()
- default:
-
- 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:]
- if len(f.toRead) == 0 {
- return n, f.err
- }
- return n, nil
- }
- if f.err != nil {
- return 0, f.err
- }
- f.step(f)
- if f.err != nil && len(f.toRead) == 0 {
- f.toRead = f.dict.readFlush()
- }
- }
- }
- func (f *decompressor) WriteTo(w io.Writer) (int64, error) {
- total := int64(0)
- flushed := false
- for {
- if len(f.toRead) > 0 {
- n, err := w.Write(f.toRead)
- total += int64(n)
- if err != nil {
- f.err = err
- return total, err
- }
- if n != len(f.toRead) {
- return total, io.ErrShortWrite
- }
- f.toRead = f.toRead[:0]
- }
- if f.err != nil && flushed {
- if f.err == io.EOF {
- return total, nil
- }
- return total, f.err
- }
- if f.err == nil {
- f.step(f)
- }
- if len(f.toRead) == 0 && f.err != nil && !flushed {
- f.toRead = f.dict.readFlush()
- flushed = true
- }
- }
- }
- func (f *decompressor) Close() error {
- if f.err == io.EOF {
- return nil
- }
- return f.err
- }
- 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 {
-
- for f.nb < 5+5+4 {
- if err := f.moreBits(); err != nil {
- return err
- }
- }
- nlit := int(f.b&0x1F) + 257
- if nlit > maxNumLit {
- return CorruptInputError(f.roffset)
- }
- f.b >>= 5
- ndist := int(f.b&0x1F) + 1
- if ndist > maxNumDist {
- return CorruptInputError(f.roffset)
- }
- f.b >>= 5
- nclen := int(f.b&0xF) + 4
-
- f.b >>= 4
- f.nb -= 5 + 5 + 4
-
- 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)
- }
-
-
- for i, n := 0, nlit+ndist; i < n; {
- x, err := f.huffSym(&f.h1)
- if err != nil {
- return err
- }
- if x < 16 {
-
- f.bits[i] = x
- i++
- continue
- }
-
- 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)
- }
-
-
-
-
- if f.h1.min < f.bits[endBlockMarker] {
- f.h1.min = f.bits[endBlockMarker]
- }
- return nil
- }
- func (f *decompressor) huffmanBlock() {
- const (
- stateInit = iota
- stateDict
- )
- switch f.stepState {
- case stateInit:
- goto readLiteral
- case stateDict:
- goto copyHistory
- }
- readLiteral:
-
- {
- v, err := f.huffSym(f.hl)
- if err != nil {
- f.err = err
- return
- }
- var n uint
- 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
-
- 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(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 < maxNumDist:
- nb := uint(dist-2) >> 1
-
- 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
- }
-
- if dist > f.dict.histSize() {
- f.err = CorruptInputError(f.roffset)
- return
- }
- f.copyLen, f.copyDist = length, dist
- goto copyHistory
- }
- copyHistory:
-
- {
- 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
- f.stepState = stateDict
- return
- }
- goto readLiteral
- }
- }
- func (f *decompressor) dataBlock() {
-
-
- f.nb = 0
- f.b = 0
-
- nr, err := io.ReadFull(f.r, f.buf[0:4])
- f.roffset += int64(nr)
- if err != nil {
- if err == io.EOF {
- err = io.ErrUnexpectedEOF
- }
- f.err = 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 {
- f.toRead = f.dict.readFlush()
- f.finishBlock()
- return
- }
- f.copyLen = n
- f.copyData()
- }
- func (f *decompressor) copyData() {
- buf := f.dict.writeSlice()
- if len(buf) > f.copyLen {
- buf = buf[:f.copyLen]
- }
- cnt, err := io.ReadFull(f.r, buf)
- f.roffset += int64(cnt)
- f.copyLen -= cnt
- f.dict.writeMark(cnt)
- if err != nil {
- if err == io.EOF {
- err = io.ErrUnexpectedEOF
- }
- f.err = err
- return
- }
- if f.dict.availWrite() == 0 || f.copyLen > 0 {
- f.toRead = f.dict.readFlush()
- f.step = (*decompressor).copyData
- return
- }
- f.finishBlock()
- }
- func (f *decompressor) finishBlock() {
- if f.final {
- if f.dict.availRead() > 0 {
- f.toRead = f.dict.readFlush()
- }
- f.err = io.EOF
- }
- f.step = (*decompressor).nextBlock
- }
- 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
- }
- 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 <= f.nb {
- if n == 0 {
- f.err = CorruptInputError(f.roffset)
- return 0, f.err
- }
- f.b >>= n
- f.nb -= n
- return int(chunk >> huffmanValueShift), nil
- }
- }
- }
- func makeReader(r io.Reader) Reader {
- if rr, ok := r.(Reader); ok {
- return rr
- }
- return bufio.NewReader(r)
- }
- func fixedHuffmanDecoderInit() {
- fixedOnce.Do(func() {
-
- var bits [288]int
- for i := 0; i < 144; i++ {
- bits[i] = 8
- }
- for i := 144; i < 256; i++ {
- bits[i] = 9
- }
- for i := 256; i < 280; i++ {
- bits[i] = 7
- }
- for i := 280; i < 288; i++ {
- bits[i] = 8
- }
- fixedHuffmanDecoder.init(bits[:])
- })
- }
- func (f *decompressor) Reset(r io.Reader, dict []byte) error {
- *f = decompressor{
- r: makeReader(r),
- bits: f.bits,
- codebits: f.codebits,
- dict: f.dict,
- step: (*decompressor).nextBlock,
- }
- f.dict.init(maxMatchOffset, dict)
- return nil
- }
- func NewReader(r io.Reader) io.ReadCloser {
- fixedHuffmanDecoderInit()
- var f decompressor
- f.r = makeReader(r)
- f.bits = new([maxNumLit + maxNumDist]int)
- f.codebits = new([numCodes]int)
- f.step = (*decompressor).nextBlock
- f.dict.init(maxMatchOffset, nil)
- return &f
- }
- func NewReaderDict(r io.Reader, dict []byte) io.ReadCloser {
- fixedHuffmanDecoderInit()
- var f decompressor
- f.r = makeReader(r)
- f.bits = new([maxNumLit + maxNumDist]int)
- f.codebits = new([numCodes]int)
- f.step = (*decompressor).nextBlock
- f.dict.init(maxMatchOffset, dict)
- return &f
- }
|