/
decompress.go
1453 lines (1312 loc) · 35.9 KB
/
decompress.go
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package huff0
import (
"errors"
"fmt"
"io"
"sync"
"github.com/klauspost/compress/fse"
)
type dTable struct {
single []dEntrySingle
double []dEntryDouble
}
// single-symbols decoding
type dEntrySingle struct {
entry uint16
}
// double-symbols decoding
type dEntryDouble struct {
seq [4]byte
nBits uint8
len uint8
}
// Uses special code for all tables that are < 8 bits.
const use8BitTables = true
// ReadTable will read a table from the input.
// The size of the input may be larger than the table definition.
// Any content remaining after the table definition will be returned.
// If no Scratch is provided a new one is allocated.
// The returned Scratch can be used for encoding or decoding input using this table.
func ReadTable(in []byte, s *Scratch) (s2 *Scratch, remain []byte, err error) {
s, err = s.prepare(in)
if err != nil {
return s, nil, err
}
if len(in) <= 1 {
return s, nil, errors.New("input too small for table")
}
iSize := in[0]
in = in[1:]
if iSize >= 128 {
// Uncompressed
oSize := iSize - 127
iSize = (oSize + 1) / 2
if int(iSize) > len(in) {
return s, nil, errors.New("input too small for table")
}
for n := uint8(0); n < oSize; n += 2 {
v := in[n/2]
s.huffWeight[n] = v >> 4
s.huffWeight[n+1] = v & 15
}
s.symbolLen = uint16(oSize)
in = in[iSize:]
} else {
if len(in) < int(iSize) {
return s, nil, fmt.Errorf("input too small for table, want %d bytes, have %d", iSize, len(in))
}
// FSE compressed weights
s.fse.DecompressLimit = 255
hw := s.huffWeight[:]
s.fse.Out = hw
b, err := fse.Decompress(in[:iSize], s.fse)
s.fse.Out = nil
if err != nil {
return s, nil, err
}
if len(b) > 255 {
return s, nil, errors.New("corrupt input: output table too large")
}
s.symbolLen = uint16(len(b))
in = in[iSize:]
}
// collect weight stats
var rankStats [16]uint32
weightTotal := uint32(0)
for _, v := range s.huffWeight[:s.symbolLen] {
if v > tableLogMax {
return s, nil, errors.New("corrupt input: weight too large")
}
v2 := v & 15
rankStats[v2]++
// (1 << (v2-1)) is slower since the compiler cannot prove that v2 isn't 0.
weightTotal += (1 << v2) >> 1
}
if weightTotal == 0 {
return s, nil, errors.New("corrupt input: weights zero")
}
// get last non-null symbol weight (implied, total must be 2^n)
{
tableLog := highBit32(weightTotal) + 1
if tableLog > tableLogMax {
return s, nil, errors.New("corrupt input: tableLog too big")
}
s.actualTableLog = uint8(tableLog)
// determine last weight
{
total := uint32(1) << tableLog
rest := total - weightTotal
verif := uint32(1) << highBit32(rest)
lastWeight := highBit32(rest) + 1
if verif != rest {
// last value must be a clean power of 2
return s, nil, errors.New("corrupt input: last value not power of two")
}
s.huffWeight[s.symbolLen] = uint8(lastWeight)
s.symbolLen++
rankStats[lastWeight]++
}
}
if (rankStats[1] < 2) || (rankStats[1]&1 != 0) {
// by construction : at least 2 elts of rank 1, must be even
return s, nil, errors.New("corrupt input: min elt size, even check failed ")
}
// TODO: Choose between single/double symbol decoding
// Calculate starting value for each rank
{
var nextRankStart uint32
for n := uint8(1); n < s.actualTableLog+1; n++ {
current := nextRankStart
nextRankStart += rankStats[n] << (n - 1)
rankStats[n] = current
}
}
// fill DTable (always full size)
tSize := 1 << tableLogMax
if len(s.dt.single) != tSize {
s.dt.single = make([]dEntrySingle, tSize)
}
cTable := s.prevTable
if cap(cTable) < maxSymbolValue+1 {
cTable = make([]cTableEntry, 0, maxSymbolValue+1)
}
cTable = cTable[:maxSymbolValue+1]
s.prevTable = cTable[:s.symbolLen]
s.prevTableLog = s.actualTableLog
for n, w := range s.huffWeight[:s.symbolLen] {
if w == 0 {
cTable[n] = cTableEntry{
val: 0,
nBits: 0,
}
continue
}
length := (uint32(1) << w) >> 1
d := dEntrySingle{
entry: uint16(s.actualTableLog+1-w) | (uint16(n) << 8),
}
rank := &rankStats[w]
cTable[n] = cTableEntry{
val: uint16(*rank >> (w - 1)),
nBits: uint8(d.entry),
}
single := s.dt.single[*rank : *rank+length]
for i := range single {
single[i] = d
}
*rank += length
}
return s, in, nil
}
// Decompress1X will decompress a 1X encoded stream.
// The length of the supplied input must match the end of a block exactly.
// Before this is called, the table must be initialized with ReadTable unless
// the encoder re-used the table.
// deprecated: Use the stateless Decoder() to get a concurrent version.
func (s *Scratch) Decompress1X(in []byte) (out []byte, err error) {
if cap(s.Out) < s.MaxDecodedSize {
s.Out = make([]byte, s.MaxDecodedSize)
}
s.Out = s.Out[:0:s.MaxDecodedSize]
s.Out, err = s.Decoder().Decompress1X(s.Out, in)
return s.Out, err
}
// Decompress4X will decompress a 4X encoded stream.
// Before this is called, the table must be initialized with ReadTable unless
// the encoder re-used the table.
// The length of the supplied input must match the end of a block exactly.
// The destination size of the uncompressed data must be known and provided.
// deprecated: Use the stateless Decoder() to get a concurrent version.
func (s *Scratch) Decompress4X(in []byte, dstSize int) (out []byte, err error) {
if dstSize > s.MaxDecodedSize {
return nil, ErrMaxDecodedSizeExceeded
}
if cap(s.Out) < dstSize {
s.Out = make([]byte, s.MaxDecodedSize)
}
s.Out = s.Out[:0:dstSize]
s.Out, err = s.Decoder().Decompress4X(s.Out, in)
return s.Out, err
}
// Decoder will return a stateless decoder that can be used by multiple
// decompressors concurrently.
// Before this is called, the table must be initialized with ReadTable.
// The Decoder is still linked to the scratch buffer so that cannot be reused.
// However, it is safe to discard the scratch.
func (s *Scratch) Decoder() *Decoder {
return &Decoder{
dt: s.dt,
actualTableLog: s.actualTableLog,
bufs: &s.decPool,
}
}
// Decoder provides stateless decoding.
type Decoder struct {
dt dTable
actualTableLog uint8
bufs *sync.Pool
}
func (d *Decoder) buffer() *[4][256]byte {
buf, ok := d.bufs.Get().(*[4][256]byte)
if ok {
return buf
}
return &[4][256]byte{}
}
// Decompress1X will decompress a 1X encoded stream.
// The cap of the output buffer will be the maximum decompressed size.
// The length of the supplied input must match the end of a block exactly.
func (d *Decoder) Decompress1X(dst, src []byte) ([]byte, error) {
if len(d.dt.single) == 0 {
return nil, errors.New("no table loaded")
}
if use8BitTables && d.actualTableLog <= 8 {
return d.decompress1X8Bit(dst, src)
}
var br bitReaderShifted
err := br.init(src)
if err != nil {
return dst, err
}
maxDecodedSize := cap(dst)
dst = dst[:0]
// Avoid bounds check by always having full sized table.
const tlSize = 1 << tableLogMax
const tlMask = tlSize - 1
dt := d.dt.single[:tlSize]
// Use temp table to avoid bound checks/append penalty.
bufs := d.buffer()
buf := &bufs[0]
var off uint8
for br.off >= 8 {
br.fillFast()
v := dt[br.peekBitsFast(d.actualTableLog)&tlMask]
br.advance(uint8(v.entry))
buf[off+0] = uint8(v.entry >> 8)
v = dt[br.peekBitsFast(d.actualTableLog)&tlMask]
br.advance(uint8(v.entry))
buf[off+1] = uint8(v.entry >> 8)
// Refill
br.fillFast()
v = dt[br.peekBitsFast(d.actualTableLog)&tlMask]
br.advance(uint8(v.entry))
buf[off+2] = uint8(v.entry >> 8)
v = dt[br.peekBitsFast(d.actualTableLog)&tlMask]
br.advance(uint8(v.entry))
buf[off+3] = uint8(v.entry >> 8)
off += 4
if off == 0 {
if len(dst)+256 > maxDecodedSize {
br.close()
d.bufs.Put(bufs)
return nil, ErrMaxDecodedSizeExceeded
}
dst = append(dst, buf[:]...)
}
}
if len(dst)+int(off) > maxDecodedSize {
d.bufs.Put(bufs)
br.close()
return nil, ErrMaxDecodedSizeExceeded
}
dst = append(dst, buf[:off]...)
// br < 8, so uint8 is fine
bitsLeft := uint8(br.off)*8 + 64 - br.bitsRead
for bitsLeft > 0 {
br.fill()
if false && br.bitsRead >= 32 {
if br.off >= 4 {
v := br.in[br.off-4:]
v = v[:4]
low := (uint32(v[0])) | (uint32(v[1]) << 8) | (uint32(v[2]) << 16) | (uint32(v[3]) << 24)
br.value = (br.value << 32) | uint64(low)
br.bitsRead -= 32
br.off -= 4
} else {
for br.off > 0 {
br.value = (br.value << 8) | uint64(br.in[br.off-1])
br.bitsRead -= 8
br.off--
}
}
}
if len(dst) >= maxDecodedSize {
d.bufs.Put(bufs)
br.close()
return nil, ErrMaxDecodedSizeExceeded
}
v := d.dt.single[br.peekBitsFast(d.actualTableLog)&tlMask]
nBits := uint8(v.entry)
br.advance(nBits)
bitsLeft -= nBits
dst = append(dst, uint8(v.entry>>8))
}
d.bufs.Put(bufs)
return dst, br.close()
}
// decompress1X8Bit will decompress a 1X encoded stream with tablelog <= 8.
// The cap of the output buffer will be the maximum decompressed size.
// The length of the supplied input must match the end of a block exactly.
func (d *Decoder) decompress1X8Bit(dst, src []byte) ([]byte, error) {
if d.actualTableLog == 8 {
return d.decompress1X8BitExactly(dst, src)
}
var br bitReaderBytes
err := br.init(src)
if err != nil {
return dst, err
}
maxDecodedSize := cap(dst)
dst = dst[:0]
// Avoid bounds check by always having full sized table.
dt := d.dt.single[:256]
// Use temp table to avoid bound checks/append penalty.
bufs := d.buffer()
buf := &bufs[0]
var off uint8
switch d.actualTableLog {
case 8:
const shift = 8 - 8
for br.off >= 4 {
br.fillFast()
v := dt[uint8(br.value>>(56+shift))]
br.advance(uint8(v.entry))
buf[off+0] = uint8(v.entry >> 8)
v = dt[uint8(br.value>>(56+shift))]
br.advance(uint8(v.entry))
buf[off+1] = uint8(v.entry >> 8)
v = dt[uint8(br.value>>(56+shift))]
br.advance(uint8(v.entry))
buf[off+2] = uint8(v.entry >> 8)
v = dt[uint8(br.value>>(56+shift))]
br.advance(uint8(v.entry))
buf[off+3] = uint8(v.entry >> 8)
off += 4
if off == 0 {
if len(dst)+256 > maxDecodedSize {
br.close()
d.bufs.Put(bufs)
return nil, ErrMaxDecodedSizeExceeded
}
dst = append(dst, buf[:]...)
}
}
case 7:
const shift = 8 - 7
for br.off >= 4 {
br.fillFast()
v := dt[uint8(br.value>>(56+shift))]
br.advance(uint8(v.entry))
buf[off+0] = uint8(v.entry >> 8)
v = dt[uint8(br.value>>(56+shift))]
br.advance(uint8(v.entry))
buf[off+1] = uint8(v.entry >> 8)
v = dt[uint8(br.value>>(56+shift))]
br.advance(uint8(v.entry))
buf[off+2] = uint8(v.entry >> 8)
v = dt[uint8(br.value>>(56+shift))]
br.advance(uint8(v.entry))
buf[off+3] = uint8(v.entry >> 8)
off += 4
if off == 0 {
if len(dst)+256 > maxDecodedSize {
br.close()
d.bufs.Put(bufs)
return nil, ErrMaxDecodedSizeExceeded
}
dst = append(dst, buf[:]...)
}
}
case 6:
const shift = 8 - 6
for br.off >= 4 {
br.fillFast()
v := dt[uint8(br.value>>(56+shift))]
br.advance(uint8(v.entry))
buf[off+0] = uint8(v.entry >> 8)
v = dt[uint8(br.value>>(56+shift))]
br.advance(uint8(v.entry))
buf[off+1] = uint8(v.entry >> 8)
v = dt[uint8(br.value>>(56+shift))]
br.advance(uint8(v.entry))
buf[off+2] = uint8(v.entry >> 8)
v = dt[uint8(br.value>>(56+shift))]
br.advance(uint8(v.entry))
buf[off+3] = uint8(v.entry >> 8)
off += 4
if off == 0 {
if len(dst)+256 > maxDecodedSize {
d.bufs.Put(bufs)
br.close()
return nil, ErrMaxDecodedSizeExceeded
}
dst = append(dst, buf[:]...)
}
}
case 5:
const shift = 8 - 5
for br.off >= 4 {
br.fillFast()
v := dt[uint8(br.value>>(56+shift))]
br.advance(uint8(v.entry))
buf[off+0] = uint8(v.entry >> 8)
v = dt[uint8(br.value>>(56+shift))]
br.advance(uint8(v.entry))
buf[off+1] = uint8(v.entry >> 8)
v = dt[uint8(br.value>>(56+shift))]
br.advance(uint8(v.entry))
buf[off+2] = uint8(v.entry >> 8)
v = dt[uint8(br.value>>(56+shift))]
br.advance(uint8(v.entry))
buf[off+3] = uint8(v.entry >> 8)
off += 4
if off == 0 {
if len(dst)+256 > maxDecodedSize {
d.bufs.Put(bufs)
br.close()
return nil, ErrMaxDecodedSizeExceeded
}
dst = append(dst, buf[:]...)
}
}
case 4:
const shift = 8 - 4
for br.off >= 4 {
br.fillFast()
v := dt[uint8(br.value>>(56+shift))]
br.advance(uint8(v.entry))
buf[off+0] = uint8(v.entry >> 8)
v = dt[uint8(br.value>>(56+shift))]
br.advance(uint8(v.entry))
buf[off+1] = uint8(v.entry >> 8)
v = dt[uint8(br.value>>(56+shift))]
br.advance(uint8(v.entry))
buf[off+2] = uint8(v.entry >> 8)
v = dt[uint8(br.value>>(56+shift))]
br.advance(uint8(v.entry))
buf[off+3] = uint8(v.entry >> 8)
off += 4
if off == 0 {
if len(dst)+256 > maxDecodedSize {
d.bufs.Put(bufs)
br.close()
return nil, ErrMaxDecodedSizeExceeded
}
dst = append(dst, buf[:]...)
}
}
case 3:
const shift = 8 - 3
for br.off >= 4 {
br.fillFast()
v := dt[uint8(br.value>>(56+shift))]
br.advance(uint8(v.entry))
buf[off+0] = uint8(v.entry >> 8)
v = dt[uint8(br.value>>(56+shift))]
br.advance(uint8(v.entry))
buf[off+1] = uint8(v.entry >> 8)
v = dt[uint8(br.value>>(56+shift))]
br.advance(uint8(v.entry))
buf[off+2] = uint8(v.entry >> 8)
v = dt[uint8(br.value>>(56+shift))]
br.advance(uint8(v.entry))
buf[off+3] = uint8(v.entry >> 8)
off += 4
if off == 0 {
if len(dst)+256 > maxDecodedSize {
d.bufs.Put(bufs)
br.close()
return nil, ErrMaxDecodedSizeExceeded
}
dst = append(dst, buf[:]...)
}
}
case 2:
const shift = 8 - 2
for br.off >= 4 {
br.fillFast()
v := dt[uint8(br.value>>(56+shift))]
br.advance(uint8(v.entry))
buf[off+0] = uint8(v.entry >> 8)
v = dt[uint8(br.value>>(56+shift))]
br.advance(uint8(v.entry))
buf[off+1] = uint8(v.entry >> 8)
v = dt[uint8(br.value>>(56+shift))]
br.advance(uint8(v.entry))
buf[off+2] = uint8(v.entry >> 8)
v = dt[uint8(br.value>>(56+shift))]
br.advance(uint8(v.entry))
buf[off+3] = uint8(v.entry >> 8)
off += 4
if off == 0 {
if len(dst)+256 > maxDecodedSize {
d.bufs.Put(bufs)
br.close()
return nil, ErrMaxDecodedSizeExceeded
}
dst = append(dst, buf[:]...)
}
}
case 1:
const shift = 8 - 1
for br.off >= 4 {
br.fillFast()
v := dt[uint8(br.value>>(56+shift))]
br.advance(uint8(v.entry))
buf[off+0] = uint8(v.entry >> 8)
v = dt[uint8(br.value>>(56+shift))]
br.advance(uint8(v.entry))
buf[off+1] = uint8(v.entry >> 8)
v = dt[uint8(br.value>>(56+shift))]
br.advance(uint8(v.entry))
buf[off+2] = uint8(v.entry >> 8)
v = dt[uint8(br.value>>(56+shift))]
br.advance(uint8(v.entry))
buf[off+3] = uint8(v.entry >> 8)
off += 4
if off == 0 {
if len(dst)+256 > maxDecodedSize {
d.bufs.Put(bufs)
br.close()
return nil, ErrMaxDecodedSizeExceeded
}
dst = append(dst, buf[:]...)
}
}
default:
d.bufs.Put(bufs)
return nil, fmt.Errorf("invalid tablelog: %d", d.actualTableLog)
}
if len(dst)+int(off) > maxDecodedSize {
d.bufs.Put(bufs)
br.close()
return nil, ErrMaxDecodedSizeExceeded
}
dst = append(dst, buf[:off]...)
// br < 4, so uint8 is fine
bitsLeft := int8(uint8(br.off)*8 + (64 - br.bitsRead))
shift := (8 - d.actualTableLog) & 7
for bitsLeft > 0 {
if br.bitsRead >= 64-8 {
for br.off > 0 {
br.value |= uint64(br.in[br.off-1]) << (br.bitsRead - 8)
br.bitsRead -= 8
br.off--
}
}
if len(dst) >= maxDecodedSize {
br.close()
d.bufs.Put(bufs)
return nil, ErrMaxDecodedSizeExceeded
}
v := dt[br.peekByteFast()>>shift]
nBits := uint8(v.entry)
br.advance(nBits)
bitsLeft -= int8(nBits)
dst = append(dst, uint8(v.entry>>8))
}
d.bufs.Put(bufs)
return dst, br.close()
}
// decompress1X8Bit will decompress a 1X encoded stream with tablelog <= 8.
// The cap of the output buffer will be the maximum decompressed size.
// The length of the supplied input must match the end of a block exactly.
func (d *Decoder) decompress1X8BitExactly(dst, src []byte) ([]byte, error) {
var br bitReaderBytes
err := br.init(src)
if err != nil {
return dst, err
}
maxDecodedSize := cap(dst)
dst = dst[:0]
// Avoid bounds check by always having full sized table.
dt := d.dt.single[:256]
// Use temp table to avoid bound checks/append penalty.
bufs := d.buffer()
buf := &bufs[0]
var off uint8
const shift = 56
//fmt.Printf("mask: %b, tl:%d\n", mask, d.actualTableLog)
for br.off >= 4 {
br.fillFast()
v := dt[uint8(br.value>>shift)]
br.advance(uint8(v.entry))
buf[off+0] = uint8(v.entry >> 8)
v = dt[uint8(br.value>>shift)]
br.advance(uint8(v.entry))
buf[off+1] = uint8(v.entry >> 8)
v = dt[uint8(br.value>>shift)]
br.advance(uint8(v.entry))
buf[off+2] = uint8(v.entry >> 8)
v = dt[uint8(br.value>>shift)]
br.advance(uint8(v.entry))
buf[off+3] = uint8(v.entry >> 8)
off += 4
if off == 0 {
if len(dst)+256 > maxDecodedSize {
d.bufs.Put(bufs)
br.close()
return nil, ErrMaxDecodedSizeExceeded
}
dst = append(dst, buf[:]...)
}
}
if len(dst)+int(off) > maxDecodedSize {
d.bufs.Put(bufs)
br.close()
return nil, ErrMaxDecodedSizeExceeded
}
dst = append(dst, buf[:off]...)
// br < 4, so uint8 is fine
bitsLeft := int8(uint8(br.off)*8 + (64 - br.bitsRead))
for bitsLeft > 0 {
if br.bitsRead >= 64-8 {
for br.off > 0 {
br.value |= uint64(br.in[br.off-1]) << (br.bitsRead - 8)
br.bitsRead -= 8
br.off--
}
}
if len(dst) >= maxDecodedSize {
d.bufs.Put(bufs)
br.close()
return nil, ErrMaxDecodedSizeExceeded
}
v := dt[br.peekByteFast()]
nBits := uint8(v.entry)
br.advance(nBits)
bitsLeft -= int8(nBits)
dst = append(dst, uint8(v.entry>>8))
}
d.bufs.Put(bufs)
return dst, br.close()
}
// Decompress4X will decompress a 4X encoded stream.
// The length of the supplied input must match the end of a block exactly.
// The *capacity* of the dst slice must match the destination size of
// the uncompressed data exactly.
func (d *Decoder) Decompress4X(dst, src []byte) ([]byte, error) {
if len(d.dt.single) == 0 {
return nil, errors.New("no table loaded")
}
if len(src) < 6+(4*1) {
return nil, errors.New("input too small")
}
if use8BitTables && d.actualTableLog <= 8 {
return d.decompress4X8bit(dst, src)
}
var br [4]bitReaderShifted
// Decode "jump table"
start := 6
for i := 0; i < 3; i++ {
length := int(src[i*2]) | (int(src[i*2+1]) << 8)
if start+length >= len(src) {
return nil, errors.New("truncated input (or invalid offset)")
}
err := br[i].init(src[start : start+length])
if err != nil {
return nil, err
}
start += length
}
err := br[3].init(src[start:])
if err != nil {
return nil, err
}
// destination, offset to match first output
dstSize := cap(dst)
dst = dst[:dstSize]
out := dst
dstEvery := (dstSize + 3) / 4
const tlSize = 1 << tableLogMax
const tlMask = tlSize - 1
single := d.dt.single[:tlSize]
// Use temp table to avoid bound checks/append penalty.
buf := d.buffer()
var off uint8
var decoded int
// Decode 2 values from each decoder/loop.
const bufoff = 256
for {
if br[0].off < 4 || br[1].off < 4 || br[2].off < 4 || br[3].off < 4 {
break
}
{
const stream = 0
const stream2 = 1
br[stream].fillFast()
br[stream2].fillFast()
val := br[stream].peekBitsFast(d.actualTableLog)
val2 := br[stream2].peekBitsFast(d.actualTableLog)
v := single[val&tlMask]
v2 := single[val2&tlMask]
br[stream].advance(uint8(v.entry))
br[stream2].advance(uint8(v2.entry))
buf[stream][off] = uint8(v.entry >> 8)
buf[stream2][off] = uint8(v2.entry >> 8)
val = br[stream].peekBitsFast(d.actualTableLog)
val2 = br[stream2].peekBitsFast(d.actualTableLog)
v = single[val&tlMask]
v2 = single[val2&tlMask]
br[stream].advance(uint8(v.entry))
br[stream2].advance(uint8(v2.entry))
buf[stream][off+1] = uint8(v.entry >> 8)
buf[stream2][off+1] = uint8(v2.entry >> 8)
}
{
const stream = 2
const stream2 = 3
br[stream].fillFast()
br[stream2].fillFast()
val := br[stream].peekBitsFast(d.actualTableLog)
val2 := br[stream2].peekBitsFast(d.actualTableLog)
v := single[val&tlMask]
v2 := single[val2&tlMask]
br[stream].advance(uint8(v.entry))
br[stream2].advance(uint8(v2.entry))
buf[stream][off] = uint8(v.entry >> 8)
buf[stream2][off] = uint8(v2.entry >> 8)
val = br[stream].peekBitsFast(d.actualTableLog)
val2 = br[stream2].peekBitsFast(d.actualTableLog)
v = single[val&tlMask]
v2 = single[val2&tlMask]
br[stream].advance(uint8(v.entry))
br[stream2].advance(uint8(v2.entry))
buf[stream][off+1] = uint8(v.entry >> 8)
buf[stream2][off+1] = uint8(v2.entry >> 8)
}
off += 2
if off == 0 {
if bufoff > dstEvery {
d.bufs.Put(buf)
return nil, errors.New("corruption detected: stream overrun 1")
}
copy(out, buf[0][:])
copy(out[dstEvery:], buf[1][:])
copy(out[dstEvery*2:], buf[2][:])
copy(out[dstEvery*3:], buf[3][:])
out = out[bufoff:]
decoded += bufoff * 4
// There must at least be 3 buffers left.
if len(out) < dstEvery*3 {
d.bufs.Put(buf)
return nil, errors.New("corruption detected: stream overrun 2")
}
}
}
if off > 0 {
ioff := int(off)
if len(out) < dstEvery*3+ioff {
d.bufs.Put(buf)
return nil, errors.New("corruption detected: stream overrun 3")
}
copy(out, buf[0][:off])
copy(out[dstEvery:], buf[1][:off])
copy(out[dstEvery*2:], buf[2][:off])
copy(out[dstEvery*3:], buf[3][:off])
decoded += int(off) * 4
out = out[off:]
}
// Decode remaining.
remainBytes := dstEvery - (decoded / 4)
for i := range br {
offset := dstEvery * i
endsAt := offset + remainBytes
if endsAt > len(out) {
endsAt = len(out)
}
br := &br[i]
bitsLeft := br.remaining()
for bitsLeft > 0 {
br.fill()
if offset >= endsAt {
d.bufs.Put(buf)
return nil, errors.New("corruption detected: stream overrun 4")
}
// Read value and increment offset.
val := br.peekBitsFast(d.actualTableLog)
v := single[val&tlMask].entry
nBits := uint8(v)
br.advance(nBits)
bitsLeft -= uint(nBits)
out[offset] = uint8(v >> 8)
offset++
}
if offset != endsAt {
d.bufs.Put(buf)
return nil, fmt.Errorf("corruption detected: short output block %d, end %d != %d", i, offset, endsAt)
}
decoded += offset - dstEvery*i
err = br.close()
if err != nil {
return nil, err
}
}
d.bufs.Put(buf)
if dstSize != decoded {
return nil, errors.New("corruption detected: short output block")
}
return dst, nil
}
// Decompress4X will decompress a 4X encoded stream.
// The length of the supplied input must match the end of a block exactly.
// The *capacity* of the dst slice must match the destination size of
// the uncompressed data exactly.
func (d *Decoder) decompress4X8bit(dst, src []byte) ([]byte, error) {
if d.actualTableLog == 8 {
return d.decompress4X8bitExactly(dst, src)
}
var br [4]bitReaderBytes
start := 6
for i := 0; i < 3; i++ {
length := int(src[i*2]) | (int(src[i*2+1]) << 8)
if start+length >= len(src) {
return nil, errors.New("truncated input (or invalid offset)")
}
err := br[i].init(src[start : start+length])
if err != nil {
return nil, err
}
start += length
}
err := br[3].init(src[start:])
if err != nil {
return nil, err
}
// destination, offset to match first output
dstSize := cap(dst)
dst = dst[:dstSize]
out := dst
dstEvery := (dstSize + 3) / 4
shift := (56 + (8 - d.actualTableLog)) & 63
const tlSize = 1 << 8
single := d.dt.single[:tlSize]
// Use temp table to avoid bound checks/append penalty.
buf := d.buffer()
var off uint8
var decoded int
// Decode 4 values from each decoder/loop.
const bufoff = 256
for {
if br[0].off < 4 || br[1].off < 4 || br[2].off < 4 || br[3].off < 4 {
break
}
{
// Interleave 2 decodes.
const stream = 0
const stream2 = 1
br1 := &br[stream]
br2 := &br[stream2]
br1.fillFast()
br2.fillFast()
v := single[uint8(br1.value>>shift)].entry
v2 := single[uint8(br2.value>>shift)].entry
br1.bitsRead += uint8(v)
br1.value <<= v & 63
br2.bitsRead += uint8(v2)
br2.value <<= v2 & 63
buf[stream][off] = uint8(v >> 8)
buf[stream2][off] = uint8(v2 >> 8)
v = single[uint8(br1.value>>shift)].entry
v2 = single[uint8(br2.value>>shift)].entry
br1.bitsRead += uint8(v)
br1.value <<= v & 63
br2.bitsRead += uint8(v2)
br2.value <<= v2 & 63
buf[stream][off+1] = uint8(v >> 8)
buf[stream2][off+1] = uint8(v2 >> 8)
v = single[uint8(br1.value>>shift)].entry
v2 = single[uint8(br2.value>>shift)].entry
br1.bitsRead += uint8(v)
br1.value <<= v & 63
br2.bitsRead += uint8(v2)
br2.value <<= v2 & 63
buf[stream][off+2] = uint8(v >> 8)
buf[stream2][off+2] = uint8(v2 >> 8)
v = single[uint8(br1.value>>shift)].entry
v2 = single[uint8(br2.value>>shift)].entry
br1.bitsRead += uint8(v)
br1.value <<= v & 63