mirror of
https://github.com/cwinfo/matterbridge.git
synced 2024-11-10 15:40:30 +00:00
716 lines
19 KiB
Go
716 lines
19 KiB
Go
// Copyright 2019+ Klaus Post. All rights reserved.
|
|
// License information can be found in the LICENSE file.
|
|
// Based on work by Yann Collet, released under BSD License.
|
|
|
|
package zstd
|
|
|
|
import (
|
|
"errors"
|
|
"fmt"
|
|
"io"
|
|
)
|
|
|
|
type seq struct {
|
|
litLen uint32
|
|
matchLen uint32
|
|
offset uint32
|
|
|
|
// Codes are stored here for the encoder
|
|
// so they only have to be looked up once.
|
|
llCode, mlCode, ofCode uint8
|
|
}
|
|
|
|
type seqVals struct {
|
|
ll, ml, mo int
|
|
}
|
|
|
|
func (s seq) String() string {
|
|
if s.offset <= 3 {
|
|
if s.offset == 0 {
|
|
return fmt.Sprint("litLen:", s.litLen, ", matchLen:", s.matchLen+zstdMinMatch, ", offset: INVALID (0)")
|
|
}
|
|
return fmt.Sprint("litLen:", s.litLen, ", matchLen:", s.matchLen+zstdMinMatch, ", offset:", s.offset, " (repeat)")
|
|
}
|
|
return fmt.Sprint("litLen:", s.litLen, ", matchLen:", s.matchLen+zstdMinMatch, ", offset:", s.offset-3, " (new)")
|
|
}
|
|
|
|
type seqCompMode uint8
|
|
|
|
const (
|
|
compModePredefined seqCompMode = iota
|
|
compModeRLE
|
|
compModeFSE
|
|
compModeRepeat
|
|
)
|
|
|
|
type sequenceDec struct {
|
|
// decoder keeps track of the current state and updates it from the bitstream.
|
|
fse *fseDecoder
|
|
state fseState
|
|
repeat bool
|
|
}
|
|
|
|
// init the state of the decoder with input from stream.
|
|
func (s *sequenceDec) init(br *bitReader) error {
|
|
if s.fse == nil {
|
|
return errors.New("sequence decoder not defined")
|
|
}
|
|
s.state.init(br, s.fse.actualTableLog, s.fse.dt[:1<<s.fse.actualTableLog])
|
|
return nil
|
|
}
|
|
|
|
// sequenceDecs contains all 3 sequence decoders and their state.
|
|
type sequenceDecs struct {
|
|
litLengths sequenceDec
|
|
offsets sequenceDec
|
|
matchLengths sequenceDec
|
|
prevOffset [3]int
|
|
dict []byte
|
|
literals []byte
|
|
out []byte
|
|
nSeqs int
|
|
br *bitReader
|
|
seqSize int
|
|
windowSize int
|
|
maxBits uint8
|
|
}
|
|
|
|
// initialize all 3 decoders from the stream input.
|
|
func (s *sequenceDecs) initialize(br *bitReader, hist *history, out []byte) error {
|
|
if err := s.litLengths.init(br); err != nil {
|
|
return errors.New("litLengths:" + err.Error())
|
|
}
|
|
if err := s.offsets.init(br); err != nil {
|
|
return errors.New("offsets:" + err.Error())
|
|
}
|
|
if err := s.matchLengths.init(br); err != nil {
|
|
return errors.New("matchLengths:" + err.Error())
|
|
}
|
|
s.br = br
|
|
s.prevOffset = hist.recentOffsets
|
|
s.maxBits = s.litLengths.fse.maxBits + s.offsets.fse.maxBits + s.matchLengths.fse.maxBits
|
|
s.windowSize = hist.windowSize
|
|
s.out = out
|
|
s.dict = nil
|
|
if hist.dict != nil {
|
|
s.dict = hist.dict.content
|
|
}
|
|
return nil
|
|
}
|
|
|
|
// decode sequences from the stream with the provided history.
|
|
func (s *sequenceDecs) decode(seqs []seqVals) error {
|
|
br := s.br
|
|
|
|
// Grab full sizes tables, to avoid bounds checks.
|
|
llTable, mlTable, ofTable := s.litLengths.fse.dt[:maxTablesize], s.matchLengths.fse.dt[:maxTablesize], s.offsets.fse.dt[:maxTablesize]
|
|
llState, mlState, ofState := s.litLengths.state.state, s.matchLengths.state.state, s.offsets.state.state
|
|
s.seqSize = 0
|
|
litRemain := len(s.literals)
|
|
maxBlockSize := maxCompressedBlockSize
|
|
if s.windowSize < maxBlockSize {
|
|
maxBlockSize = s.windowSize
|
|
}
|
|
for i := range seqs {
|
|
var ll, mo, ml int
|
|
if br.off > 4+((maxOffsetBits+16+16)>>3) {
|
|
// inlined function:
|
|
// ll, mo, ml = s.nextFast(br, llState, mlState, ofState)
|
|
|
|
// Final will not read from stream.
|
|
var llB, mlB, moB uint8
|
|
ll, llB = llState.final()
|
|
ml, mlB = mlState.final()
|
|
mo, moB = ofState.final()
|
|
|
|
// extra bits are stored in reverse order.
|
|
br.fillFast()
|
|
mo += br.getBits(moB)
|
|
if s.maxBits > 32 {
|
|
br.fillFast()
|
|
}
|
|
ml += br.getBits(mlB)
|
|
ll += br.getBits(llB)
|
|
|
|
if moB > 1 {
|
|
s.prevOffset[2] = s.prevOffset[1]
|
|
s.prevOffset[1] = s.prevOffset[0]
|
|
s.prevOffset[0] = mo
|
|
} else {
|
|
// mo = s.adjustOffset(mo, ll, moB)
|
|
// Inlined for rather big speedup
|
|
if ll == 0 {
|
|
// There is an exception though, when current sequence's literals_length = 0.
|
|
// In this case, repeated offsets are shifted by one, so an offset_value of 1 means Repeated_Offset2,
|
|
// an offset_value of 2 means Repeated_Offset3, and an offset_value of 3 means Repeated_Offset1 - 1_byte.
|
|
mo++
|
|
}
|
|
|
|
if mo == 0 {
|
|
mo = s.prevOffset[0]
|
|
} else {
|
|
var temp int
|
|
if mo == 3 {
|
|
temp = s.prevOffset[0] - 1
|
|
} else {
|
|
temp = s.prevOffset[mo]
|
|
}
|
|
|
|
if temp == 0 {
|
|
// 0 is not valid; input is corrupted; force offset to 1
|
|
println("WARNING: temp was 0")
|
|
temp = 1
|
|
}
|
|
|
|
if mo != 1 {
|
|
s.prevOffset[2] = s.prevOffset[1]
|
|
}
|
|
s.prevOffset[1] = s.prevOffset[0]
|
|
s.prevOffset[0] = temp
|
|
mo = temp
|
|
}
|
|
}
|
|
br.fillFast()
|
|
} else {
|
|
if br.overread() {
|
|
if debugDecoder {
|
|
printf("reading sequence %d, exceeded available data\n", i)
|
|
}
|
|
return io.ErrUnexpectedEOF
|
|
}
|
|
ll, mo, ml = s.next(br, llState, mlState, ofState)
|
|
br.fill()
|
|
}
|
|
|
|
if debugSequences {
|
|
println("Seq", i, "Litlen:", ll, "mo:", mo, "(abs) ml:", ml)
|
|
}
|
|
// Evaluate.
|
|
// We might be doing this async, so do it early.
|
|
if mo == 0 && ml > 0 {
|
|
return fmt.Errorf("zero matchoff and matchlen (%d) > 0", ml)
|
|
}
|
|
if ml > maxMatchLen {
|
|
return fmt.Errorf("match len (%d) bigger than max allowed length", ml)
|
|
}
|
|
s.seqSize += ll + ml
|
|
if s.seqSize > maxBlockSize {
|
|
return fmt.Errorf("output (%d) bigger than max block size (%d)", s.seqSize, maxBlockSize)
|
|
}
|
|
litRemain -= ll
|
|
if litRemain < 0 {
|
|
return fmt.Errorf("unexpected literal count, want %d bytes, but only %d is available", ll, litRemain+ll)
|
|
}
|
|
seqs[i] = seqVals{
|
|
ll: ll,
|
|
ml: ml,
|
|
mo: mo,
|
|
}
|
|
if i == len(seqs)-1 {
|
|
// This is the last sequence, so we shouldn't update state.
|
|
break
|
|
}
|
|
|
|
// Manually inlined, ~ 5-20% faster
|
|
// Update all 3 states at once. Approx 20% faster.
|
|
nBits := llState.nbBits() + mlState.nbBits() + ofState.nbBits()
|
|
if nBits == 0 {
|
|
llState = llTable[llState.newState()&maxTableMask]
|
|
mlState = mlTable[mlState.newState()&maxTableMask]
|
|
ofState = ofTable[ofState.newState()&maxTableMask]
|
|
} else {
|
|
bits := br.get32BitsFast(nBits)
|
|
lowBits := uint16(bits >> ((ofState.nbBits() + mlState.nbBits()) & 31))
|
|
llState = llTable[(llState.newState()+lowBits)&maxTableMask]
|
|
|
|
lowBits = uint16(bits >> (ofState.nbBits() & 31))
|
|
lowBits &= bitMask[mlState.nbBits()&15]
|
|
mlState = mlTable[(mlState.newState()+lowBits)&maxTableMask]
|
|
|
|
lowBits = uint16(bits) & bitMask[ofState.nbBits()&15]
|
|
ofState = ofTable[(ofState.newState()+lowBits)&maxTableMask]
|
|
}
|
|
}
|
|
s.seqSize += litRemain
|
|
if s.seqSize > maxBlockSize {
|
|
return fmt.Errorf("output (%d) bigger than max block size (%d)", s.seqSize, maxBlockSize)
|
|
}
|
|
err := br.close()
|
|
if err != nil {
|
|
printf("Closing sequences: %v, %+v\n", err, *br)
|
|
}
|
|
return err
|
|
}
|
|
|
|
// execute will execute the decoded sequence with the provided history.
|
|
// The sequence must be evaluated before being sent.
|
|
func (s *sequenceDecs) execute(seqs []seqVals, hist []byte) error {
|
|
// Ensure we have enough output size...
|
|
if len(s.out)+s.seqSize > cap(s.out) {
|
|
addBytes := s.seqSize + len(s.out)
|
|
s.out = append(s.out, make([]byte, addBytes)...)
|
|
s.out = s.out[:len(s.out)-addBytes]
|
|
}
|
|
|
|
if debugDecoder {
|
|
printf("Execute %d seqs with hist %d, dict %d, literals: %d into %d bytes\n", len(seqs), len(hist), len(s.dict), len(s.literals), s.seqSize)
|
|
}
|
|
|
|
var t = len(s.out)
|
|
out := s.out[:t+s.seqSize]
|
|
|
|
for _, seq := range seqs {
|
|
// Add literals
|
|
copy(out[t:], s.literals[:seq.ll])
|
|
t += seq.ll
|
|
s.literals = s.literals[seq.ll:]
|
|
|
|
// Copy from dictionary...
|
|
if seq.mo > t+len(hist) || seq.mo > s.windowSize {
|
|
if len(s.dict) == 0 {
|
|
return fmt.Errorf("match offset (%d) bigger than current history (%d)", seq.mo, t+len(hist))
|
|
}
|
|
|
|
// we may be in dictionary.
|
|
dictO := len(s.dict) - (seq.mo - (t + len(hist)))
|
|
if dictO < 0 || dictO >= len(s.dict) {
|
|
return fmt.Errorf("match offset (%d) bigger than current history+dict (%d)", seq.mo, t+len(hist)+len(s.dict))
|
|
}
|
|
end := dictO + seq.ml
|
|
if end > len(s.dict) {
|
|
n := len(s.dict) - dictO
|
|
copy(out[t:], s.dict[dictO:])
|
|
t += n
|
|
seq.ml -= n
|
|
} else {
|
|
copy(out[t:], s.dict[dictO:end])
|
|
t += end - dictO
|
|
continue
|
|
}
|
|
}
|
|
|
|
// Copy from history.
|
|
if v := seq.mo - t; v > 0 {
|
|
// v is the start position in history from end.
|
|
start := len(hist) - v
|
|
if seq.ml > v {
|
|
// Some goes into current block.
|
|
// Copy remainder of history
|
|
copy(out[t:], hist[start:])
|
|
t += v
|
|
seq.ml -= v
|
|
} else {
|
|
copy(out[t:], hist[start:start+seq.ml])
|
|
t += seq.ml
|
|
continue
|
|
}
|
|
}
|
|
// We must be in current buffer now
|
|
if seq.ml > 0 {
|
|
start := t - seq.mo
|
|
if seq.ml <= t-start {
|
|
// No overlap
|
|
copy(out[t:], out[start:start+seq.ml])
|
|
t += seq.ml
|
|
continue
|
|
} else {
|
|
// Overlapping copy
|
|
// Extend destination slice and copy one byte at the time.
|
|
src := out[start : start+seq.ml]
|
|
dst := out[t:]
|
|
dst = dst[:len(src)]
|
|
t += len(src)
|
|
// Destination is the space we just added.
|
|
for i := range src {
|
|
dst[i] = src[i]
|
|
}
|
|
}
|
|
}
|
|
}
|
|
// Add final literals
|
|
copy(out[t:], s.literals)
|
|
if debugDecoder {
|
|
t += len(s.literals)
|
|
if t != len(out) {
|
|
panic(fmt.Errorf("length mismatch, want %d, got %d, ss: %d", len(out), t, s.seqSize))
|
|
}
|
|
}
|
|
s.out = out
|
|
|
|
return nil
|
|
}
|
|
|
|
// decode sequences from the stream with the provided history.
|
|
func (s *sequenceDecs) decodeSync(history *history) error {
|
|
br := s.br
|
|
seqs := s.nSeqs
|
|
startSize := len(s.out)
|
|
// Grab full sizes tables, to avoid bounds checks.
|
|
llTable, mlTable, ofTable := s.litLengths.fse.dt[:maxTablesize], s.matchLengths.fse.dt[:maxTablesize], s.offsets.fse.dt[:maxTablesize]
|
|
llState, mlState, ofState := s.litLengths.state.state, s.matchLengths.state.state, s.offsets.state.state
|
|
hist := history.b[history.ignoreBuffer:]
|
|
out := s.out
|
|
maxBlockSize := maxCompressedBlockSize
|
|
if s.windowSize < maxBlockSize {
|
|
maxBlockSize = s.windowSize
|
|
}
|
|
|
|
for i := seqs - 1; i >= 0; i-- {
|
|
if br.overread() {
|
|
printf("reading sequence %d, exceeded available data\n", seqs-i)
|
|
return io.ErrUnexpectedEOF
|
|
}
|
|
var ll, mo, ml int
|
|
if br.off > 4+((maxOffsetBits+16+16)>>3) {
|
|
// inlined function:
|
|
// ll, mo, ml = s.nextFast(br, llState, mlState, ofState)
|
|
|
|
// Final will not read from stream.
|
|
var llB, mlB, moB uint8
|
|
ll, llB = llState.final()
|
|
ml, mlB = mlState.final()
|
|
mo, moB = ofState.final()
|
|
|
|
// extra bits are stored in reverse order.
|
|
br.fillFast()
|
|
mo += br.getBits(moB)
|
|
if s.maxBits > 32 {
|
|
br.fillFast()
|
|
}
|
|
ml += br.getBits(mlB)
|
|
ll += br.getBits(llB)
|
|
|
|
if moB > 1 {
|
|
s.prevOffset[2] = s.prevOffset[1]
|
|
s.prevOffset[1] = s.prevOffset[0]
|
|
s.prevOffset[0] = mo
|
|
} else {
|
|
// mo = s.adjustOffset(mo, ll, moB)
|
|
// Inlined for rather big speedup
|
|
if ll == 0 {
|
|
// There is an exception though, when current sequence's literals_length = 0.
|
|
// In this case, repeated offsets are shifted by one, so an offset_value of 1 means Repeated_Offset2,
|
|
// an offset_value of 2 means Repeated_Offset3, and an offset_value of 3 means Repeated_Offset1 - 1_byte.
|
|
mo++
|
|
}
|
|
|
|
if mo == 0 {
|
|
mo = s.prevOffset[0]
|
|
} else {
|
|
var temp int
|
|
if mo == 3 {
|
|
temp = s.prevOffset[0] - 1
|
|
} else {
|
|
temp = s.prevOffset[mo]
|
|
}
|
|
|
|
if temp == 0 {
|
|
// 0 is not valid; input is corrupted; force offset to 1
|
|
println("WARNING: temp was 0")
|
|
temp = 1
|
|
}
|
|
|
|
if mo != 1 {
|
|
s.prevOffset[2] = s.prevOffset[1]
|
|
}
|
|
s.prevOffset[1] = s.prevOffset[0]
|
|
s.prevOffset[0] = temp
|
|
mo = temp
|
|
}
|
|
}
|
|
br.fillFast()
|
|
} else {
|
|
ll, mo, ml = s.next(br, llState, mlState, ofState)
|
|
br.fill()
|
|
}
|
|
|
|
if debugSequences {
|
|
println("Seq", seqs-i-1, "Litlen:", ll, "mo:", mo, "(abs) ml:", ml)
|
|
}
|
|
|
|
if ll > len(s.literals) {
|
|
return fmt.Errorf("unexpected literal count, want %d bytes, but only %d is available", ll, len(s.literals))
|
|
}
|
|
size := ll + ml + len(out)
|
|
if size-startSize > maxBlockSize {
|
|
return fmt.Errorf("output (%d) bigger than max block size (%d)", size, maxBlockSize)
|
|
}
|
|
if size > cap(out) {
|
|
// Not enough size, which can happen under high volume block streaming conditions
|
|
// but could be if destination slice is too small for sync operations.
|
|
// over-allocating here can create a large amount of GC pressure so we try to keep
|
|
// it as contained as possible
|
|
used := len(out) - startSize
|
|
addBytes := 256 + ll + ml + used>>2
|
|
// Clamp to max block size.
|
|
if used+addBytes > maxBlockSize {
|
|
addBytes = maxBlockSize - used
|
|
}
|
|
out = append(out, make([]byte, addBytes)...)
|
|
out = out[:len(out)-addBytes]
|
|
}
|
|
if ml > maxMatchLen {
|
|
return fmt.Errorf("match len (%d) bigger than max allowed length", ml)
|
|
}
|
|
|
|
// Add literals
|
|
out = append(out, s.literals[:ll]...)
|
|
s.literals = s.literals[ll:]
|
|
|
|
if mo == 0 && ml > 0 {
|
|
return fmt.Errorf("zero matchoff and matchlen (%d) > 0", ml)
|
|
}
|
|
|
|
if mo > len(out)+len(hist) || mo > s.windowSize {
|
|
if len(s.dict) == 0 {
|
|
return fmt.Errorf("match offset (%d) bigger than current history (%d)", mo, len(out)+len(hist))
|
|
}
|
|
|
|
// we may be in dictionary.
|
|
dictO := len(s.dict) - (mo - (len(out) + len(hist)))
|
|
if dictO < 0 || dictO >= len(s.dict) {
|
|
return fmt.Errorf("match offset (%d) bigger than current history (%d)", mo, len(out)+len(hist))
|
|
}
|
|
end := dictO + ml
|
|
if end > len(s.dict) {
|
|
out = append(out, s.dict[dictO:]...)
|
|
ml -= len(s.dict) - dictO
|
|
} else {
|
|
out = append(out, s.dict[dictO:end]...)
|
|
mo = 0
|
|
ml = 0
|
|
}
|
|
}
|
|
|
|
// Copy from history.
|
|
// TODO: Blocks without history could be made to ignore this completely.
|
|
if v := mo - len(out); v > 0 {
|
|
// v is the start position in history from end.
|
|
start := len(hist) - v
|
|
if ml > v {
|
|
// Some goes into current block.
|
|
// Copy remainder of history
|
|
out = append(out, hist[start:]...)
|
|
ml -= v
|
|
} else {
|
|
out = append(out, hist[start:start+ml]...)
|
|
ml = 0
|
|
}
|
|
}
|
|
// We must be in current buffer now
|
|
if ml > 0 {
|
|
start := len(out) - mo
|
|
if ml <= len(out)-start {
|
|
// No overlap
|
|
out = append(out, out[start:start+ml]...)
|
|
} else {
|
|
// Overlapping copy
|
|
// Extend destination slice and copy one byte at the time.
|
|
out = out[:len(out)+ml]
|
|
src := out[start : start+ml]
|
|
// Destination is the space we just added.
|
|
dst := out[len(out)-ml:]
|
|
dst = dst[:len(src)]
|
|
for i := range src {
|
|
dst[i] = src[i]
|
|
}
|
|
}
|
|
}
|
|
if i == 0 {
|
|
// This is the last sequence, so we shouldn't update state.
|
|
break
|
|
}
|
|
|
|
// Manually inlined, ~ 5-20% faster
|
|
// Update all 3 states at once. Approx 20% faster.
|
|
nBits := llState.nbBits() + mlState.nbBits() + ofState.nbBits()
|
|
if nBits == 0 {
|
|
llState = llTable[llState.newState()&maxTableMask]
|
|
mlState = mlTable[mlState.newState()&maxTableMask]
|
|
ofState = ofTable[ofState.newState()&maxTableMask]
|
|
} else {
|
|
bits := br.get32BitsFast(nBits)
|
|
lowBits := uint16(bits >> ((ofState.nbBits() + mlState.nbBits()) & 31))
|
|
llState = llTable[(llState.newState()+lowBits)&maxTableMask]
|
|
|
|
lowBits = uint16(bits >> (ofState.nbBits() & 31))
|
|
lowBits &= bitMask[mlState.nbBits()&15]
|
|
mlState = mlTable[(mlState.newState()+lowBits)&maxTableMask]
|
|
|
|
lowBits = uint16(bits) & bitMask[ofState.nbBits()&15]
|
|
ofState = ofTable[(ofState.newState()+lowBits)&maxTableMask]
|
|
}
|
|
}
|
|
|
|
// Check if space for literals
|
|
if len(s.literals)+len(s.out)-startSize > maxBlockSize {
|
|
return fmt.Errorf("output (%d) bigger than max block size (%d)", len(s.out), maxBlockSize)
|
|
}
|
|
|
|
// Add final literals
|
|
s.out = append(out, s.literals...)
|
|
return br.close()
|
|
}
|
|
|
|
// update states, at least 27 bits must be available.
|
|
func (s *sequenceDecs) update(br *bitReader) {
|
|
// Max 8 bits
|
|
s.litLengths.state.next(br)
|
|
// Max 9 bits
|
|
s.matchLengths.state.next(br)
|
|
// Max 8 bits
|
|
s.offsets.state.next(br)
|
|
}
|
|
|
|
var bitMask [16]uint16
|
|
|
|
func init() {
|
|
for i := range bitMask[:] {
|
|
bitMask[i] = uint16((1 << uint(i)) - 1)
|
|
}
|
|
}
|
|
|
|
// update states, at least 27 bits must be available.
|
|
func (s *sequenceDecs) updateAlt(br *bitReader) {
|
|
// Update all 3 states at once. Approx 20% faster.
|
|
a, b, c := s.litLengths.state.state, s.matchLengths.state.state, s.offsets.state.state
|
|
|
|
nBits := a.nbBits() + b.nbBits() + c.nbBits()
|
|
if nBits == 0 {
|
|
s.litLengths.state.state = s.litLengths.state.dt[a.newState()]
|
|
s.matchLengths.state.state = s.matchLengths.state.dt[b.newState()]
|
|
s.offsets.state.state = s.offsets.state.dt[c.newState()]
|
|
return
|
|
}
|
|
bits := br.get32BitsFast(nBits)
|
|
lowBits := uint16(bits >> ((c.nbBits() + b.nbBits()) & 31))
|
|
s.litLengths.state.state = s.litLengths.state.dt[a.newState()+lowBits]
|
|
|
|
lowBits = uint16(bits >> (c.nbBits() & 31))
|
|
lowBits &= bitMask[b.nbBits()&15]
|
|
s.matchLengths.state.state = s.matchLengths.state.dt[b.newState()+lowBits]
|
|
|
|
lowBits = uint16(bits) & bitMask[c.nbBits()&15]
|
|
s.offsets.state.state = s.offsets.state.dt[c.newState()+lowBits]
|
|
}
|
|
|
|
// nextFast will return new states when there are at least 4 unused bytes left on the stream when done.
|
|
func (s *sequenceDecs) nextFast(br *bitReader, llState, mlState, ofState decSymbol) (ll, mo, ml int) {
|
|
// Final will not read from stream.
|
|
ll, llB := llState.final()
|
|
ml, mlB := mlState.final()
|
|
mo, moB := ofState.final()
|
|
|
|
// extra bits are stored in reverse order.
|
|
br.fillFast()
|
|
mo += br.getBits(moB)
|
|
if s.maxBits > 32 {
|
|
br.fillFast()
|
|
}
|
|
ml += br.getBits(mlB)
|
|
ll += br.getBits(llB)
|
|
|
|
if moB > 1 {
|
|
s.prevOffset[2] = s.prevOffset[1]
|
|
s.prevOffset[1] = s.prevOffset[0]
|
|
s.prevOffset[0] = mo
|
|
return
|
|
}
|
|
// mo = s.adjustOffset(mo, ll, moB)
|
|
// Inlined for rather big speedup
|
|
if ll == 0 {
|
|
// There is an exception though, when current sequence's literals_length = 0.
|
|
// In this case, repeated offsets are shifted by one, so an offset_value of 1 means Repeated_Offset2,
|
|
// an offset_value of 2 means Repeated_Offset3, and an offset_value of 3 means Repeated_Offset1 - 1_byte.
|
|
mo++
|
|
}
|
|
|
|
if mo == 0 {
|
|
mo = s.prevOffset[0]
|
|
return
|
|
}
|
|
var temp int
|
|
if mo == 3 {
|
|
temp = s.prevOffset[0] - 1
|
|
} else {
|
|
temp = s.prevOffset[mo]
|
|
}
|
|
|
|
if temp == 0 {
|
|
// 0 is not valid; input is corrupted; force offset to 1
|
|
println("temp was 0")
|
|
temp = 1
|
|
}
|
|
|
|
if mo != 1 {
|
|
s.prevOffset[2] = s.prevOffset[1]
|
|
}
|
|
s.prevOffset[1] = s.prevOffset[0]
|
|
s.prevOffset[0] = temp
|
|
mo = temp
|
|
return
|
|
}
|
|
|
|
func (s *sequenceDecs) next(br *bitReader, llState, mlState, ofState decSymbol) (ll, mo, ml int) {
|
|
// Final will not read from stream.
|
|
ll, llB := llState.final()
|
|
ml, mlB := mlState.final()
|
|
mo, moB := ofState.final()
|
|
|
|
// extra bits are stored in reverse order.
|
|
br.fill()
|
|
if s.maxBits <= 32 {
|
|
mo += br.getBits(moB)
|
|
ml += br.getBits(mlB)
|
|
ll += br.getBits(llB)
|
|
} else {
|
|
mo += br.getBits(moB)
|
|
br.fill()
|
|
// matchlength+literal length, max 32 bits
|
|
ml += br.getBits(mlB)
|
|
ll += br.getBits(llB)
|
|
|
|
}
|
|
mo = s.adjustOffset(mo, ll, moB)
|
|
return
|
|
}
|
|
|
|
func (s *sequenceDecs) adjustOffset(offset, litLen int, offsetB uint8) int {
|
|
if offsetB > 1 {
|
|
s.prevOffset[2] = s.prevOffset[1]
|
|
s.prevOffset[1] = s.prevOffset[0]
|
|
s.prevOffset[0] = offset
|
|
return offset
|
|
}
|
|
|
|
if litLen == 0 {
|
|
// There is an exception though, when current sequence's literals_length = 0.
|
|
// In this case, repeated offsets are shifted by one, so an offset_value of 1 means Repeated_Offset2,
|
|
// an offset_value of 2 means Repeated_Offset3, and an offset_value of 3 means Repeated_Offset1 - 1_byte.
|
|
offset++
|
|
}
|
|
|
|
if offset == 0 {
|
|
return s.prevOffset[0]
|
|
}
|
|
var temp int
|
|
if offset == 3 {
|
|
temp = s.prevOffset[0] - 1
|
|
} else {
|
|
temp = s.prevOffset[offset]
|
|
}
|
|
|
|
if temp == 0 {
|
|
// 0 is not valid; input is corrupted; force offset to 1
|
|
println("temp was 0")
|
|
temp = 1
|
|
}
|
|
|
|
if offset != 1 {
|
|
s.prevOffset[2] = s.prevOffset[1]
|
|
}
|
|
s.prevOffset[1] = s.prevOffset[0]
|
|
s.prevOffset[0] = temp
|
|
return temp
|
|
}
|