forgejo-federation/vendor/github.com/klauspost/compress/huff0/decompress.go
techknowlogick c5d5d63c9c
Macaron 1.5 (#12596)
* update macaron to v1.5 of fork

* update macaron to v1.5 of fork

* test gzip PR

* add push method impl to context_tests

* use proper gzip commit

Co-authored-by: zeripath <art27@cantab.net>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
2020-08-27 22:47:17 -04:00

1164 lines
30 KiB
Go
Vendored

package huff0
import (
"errors"
"fmt"
"io"
"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 uint16
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,
}
}
// Decoder provides stateless decoding.
type Decoder struct {
dt dTable
actualTableLog uint8
}
// 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.
var buf [256]byte
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()
return nil, ErrMaxDecodedSizeExceeded
}
dst = append(dst, buf[:]...)
}
}
if len(dst)+int(off) > maxDecodedSize {
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 {
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))
}
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.
var buf [256]byte
var off uint8
shift := (8 - d.actualTableLog) & 7
//fmt.Printf("mask: %b, tl:%d\n", mask, d.actualTableLog)
for br.off >= 4 {
br.fillFast()
v := dt[br.peekByteFast()>>shift]
br.advance(uint8(v.entry))
buf[off+0] = uint8(v.entry >> 8)
v = dt[br.peekByteFast()>>shift]
br.advance(uint8(v.entry))
buf[off+1] = uint8(v.entry >> 8)
v = dt[br.peekByteFast()>>shift]
br.advance(uint8(v.entry))
buf[off+2] = uint8(v.entry >> 8)
v = dt[br.peekByteFast()>>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()
return nil, ErrMaxDecodedSizeExceeded
}
dst = append(dst, buf[:]...)
}
}
if len(dst)+int(off) > maxDecodedSize {
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 {
br.close()
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))
}
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.
var buf [256]byte
var off uint8
const shift = 0
//fmt.Printf("mask: %b, tl:%d\n", mask, d.actualTableLog)
for br.off >= 4 {
br.fillFast()
v := dt[br.peekByteFast()>>shift]
br.advance(uint8(v.entry))
buf[off+0] = uint8(v.entry >> 8)
v = dt[br.peekByteFast()>>shift]
br.advance(uint8(v.entry))
buf[off+1] = uint8(v.entry >> 8)
v = dt[br.peekByteFast()>>shift]
br.advance(uint8(v.entry))
buf[off+2] = uint8(v.entry >> 8)
v = dt[br.peekByteFast()>>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()
return nil, ErrMaxDecodedSizeExceeded
}
dst = append(dst, buf[:]...)
}
}
if len(dst)+int(off) > maxDecodedSize {
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 {
br.close()
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))
}
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
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.
var buf [256]byte
var off uint8
var decoded int
// Decode 2 values from each decoder/loop.
const bufoff = 256 / 4
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)
v := single[val&tlMask]
br[stream].advance(uint8(v.entry))
buf[off+bufoff*stream] = uint8(v.entry >> 8)
val2 := br[stream2].peekBitsFast(d.actualTableLog)
v2 := single[val2&tlMask]
br[stream2].advance(uint8(v2.entry))
buf[off+bufoff*stream2] = uint8(v2.entry >> 8)
val = br[stream].peekBitsFast(d.actualTableLog)
v = single[val&tlMask]
br[stream].advance(uint8(v.entry))
buf[off+bufoff*stream+1] = uint8(v.entry >> 8)
val2 = br[stream2].peekBitsFast(d.actualTableLog)
v2 = single[val2&tlMask]
br[stream2].advance(uint8(v2.entry))
buf[off+bufoff*stream2+1] = uint8(v2.entry >> 8)
}
{
const stream = 2
const stream2 = 3
br[stream].fillFast()
br[stream2].fillFast()
val := br[stream].peekBitsFast(d.actualTableLog)
v := single[val&tlMask]
br[stream].advance(uint8(v.entry))
buf[off+bufoff*stream] = uint8(v.entry >> 8)
val2 := br[stream2].peekBitsFast(d.actualTableLog)
v2 := single[val2&tlMask]
br[stream2].advance(uint8(v2.entry))
buf[off+bufoff*stream2] = uint8(v2.entry >> 8)
val = br[stream].peekBitsFast(d.actualTableLog)
v = single[val&tlMask]
br[stream].advance(uint8(v.entry))
buf[off+bufoff*stream+1] = uint8(v.entry >> 8)
val2 = br[stream2].peekBitsFast(d.actualTableLog)
v2 = single[val2&tlMask]
br[stream2].advance(uint8(v2.entry))
buf[off+bufoff*stream2+1] = uint8(v2.entry >> 8)
}
off += 2
if off == bufoff {
if bufoff > dstEvery {
return nil, errors.New("corruption detected: stream overrun 1")
}
copy(out, buf[:bufoff])
copy(out[dstEvery:], buf[bufoff:bufoff*2])
copy(out[dstEvery*2:], buf[bufoff*2:bufoff*3])
copy(out[dstEvery*3:], buf[bufoff*3:bufoff*4])
off = 0
out = out[bufoff:]
decoded += 256
// There must at least be 3 buffers left.
if len(out) < dstEvery*3 {
return nil, errors.New("corruption detected: stream overrun 2")
}
}
}
if off > 0 {
ioff := int(off)
if len(out) < dstEvery*3+ioff {
return nil, errors.New("corruption detected: stream overrun 3")
}
copy(out, buf[:off])
copy(out[dstEvery:dstEvery+ioff], buf[bufoff:bufoff*2])
copy(out[dstEvery*2:dstEvery*2+ioff], buf[bufoff*2:bufoff*3])
copy(out[dstEvery*3:dstEvery*3+ioff], buf[bufoff*3:bufoff*4])
decoded += int(off) * 4
out = out[off:]
}
// Decode remaining.
for i := range br {
offset := dstEvery * i
br := &br[i]
bitsLeft := br.off*8 + uint(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--
}
}
}
// end inline...
if offset >= len(out) {
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++
}
decoded += offset - dstEvery*i
err = br.close()
if err != nil {
return nil, err
}
}
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 := (8 - d.actualTableLog) & 7
const tlSize = 1 << 8
const tlMask = tlSize - 1
single := d.dt.single[:tlSize]
// Use temp table to avoid bound checks/append penalty.
var buf [256]byte
var off uint8
var decoded int
// Decode 4 values from each decoder/loop.
const bufoff = 256 / 4
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
br[stream].fillFast()
br[stream2].fillFast()
v := single[br[stream].peekByteFast()>>shift].entry
buf[off+bufoff*stream] = uint8(v >> 8)
br[stream].advance(uint8(v))
v2 := single[br[stream2].peekByteFast()>>shift].entry
buf[off+bufoff*stream2] = uint8(v2 >> 8)
br[stream2].advance(uint8(v2))
v = single[br[stream].peekByteFast()>>shift].entry
buf[off+bufoff*stream+1] = uint8(v >> 8)
br[stream].advance(uint8(v))
v2 = single[br[stream2].peekByteFast()>>shift].entry
buf[off+bufoff*stream2+1] = uint8(v2 >> 8)
br[stream2].advance(uint8(v2))
v = single[br[stream].peekByteFast()>>shift].entry
buf[off+bufoff*stream+2] = uint8(v >> 8)
br[stream].advance(uint8(v))
v2 = single[br[stream2].peekByteFast()>>shift].entry
buf[off+bufoff*stream2+2] = uint8(v2 >> 8)
br[stream2].advance(uint8(v2))
v = single[br[stream].peekByteFast()>>shift].entry
buf[off+bufoff*stream+3] = uint8(v >> 8)
br[stream].advance(uint8(v))
v2 = single[br[stream2].peekByteFast()>>shift].entry
buf[off+bufoff*stream2+3] = uint8(v2 >> 8)
br[stream2].advance(uint8(v2))
}
{
const stream = 2
const stream2 = 3
br[stream].fillFast()
br[stream2].fillFast()
v := single[br[stream].peekByteFast()>>shift].entry
buf[off+bufoff*stream] = uint8(v >> 8)
br[stream].advance(uint8(v))
v2 := single[br[stream2].peekByteFast()>>shift].entry
buf[off+bufoff*stream2] = uint8(v2 >> 8)
br[stream2].advance(uint8(v2))
v = single[br[stream].peekByteFast()>>shift].entry
buf[off+bufoff*stream+1] = uint8(v >> 8)
br[stream].advance(uint8(v))
v2 = single[br[stream2].peekByteFast()>>shift].entry
buf[off+bufoff*stream2+1] = uint8(v2 >> 8)
br[stream2].advance(uint8(v2))
v = single[br[stream].peekByteFast()>>shift].entry
buf[off+bufoff*stream+2] = uint8(v >> 8)
br[stream].advance(uint8(v))
v2 = single[br[stream2].peekByteFast()>>shift].entry
buf[off+bufoff*stream2+2] = uint8(v2 >> 8)
br[stream2].advance(uint8(v2))
v = single[br[stream].peekByteFast()>>shift].entry
buf[off+bufoff*stream+3] = uint8(v >> 8)
br[stream].advance(uint8(v))
v2 = single[br[stream2].peekByteFast()>>shift].entry
buf[off+bufoff*stream2+3] = uint8(v2 >> 8)
br[stream2].advance(uint8(v2))
}
off += 4
if off == bufoff {
if bufoff > dstEvery {
return nil, errors.New("corruption detected: stream overrun 1")
}
copy(out, buf[:bufoff])
copy(out[dstEvery:], buf[bufoff:bufoff*2])
copy(out[dstEvery*2:], buf[bufoff*2:bufoff*3])
copy(out[dstEvery*3:], buf[bufoff*3:bufoff*4])
off = 0
out = out[bufoff:]
decoded += 256
// There must at least be 3 buffers left.
if len(out) < dstEvery*3 {
return nil, errors.New("corruption detected: stream overrun 2")
}
}
}
if off > 0 {
ioff := int(off)
if len(out) < dstEvery*3+ioff {
return nil, errors.New("corruption detected: stream overrun 3")
}
copy(out, buf[:off])
copy(out[dstEvery:dstEvery+ioff], buf[bufoff:bufoff*2])
copy(out[dstEvery*2:dstEvery*2+ioff], buf[bufoff*2:bufoff*3])
copy(out[dstEvery*3:dstEvery*3+ioff], buf[bufoff*3:bufoff*4])
decoded += int(off) * 4
out = out[off:]
}
// Decode remaining.
for i := range br {
offset := dstEvery * i
br := &br[i]
bitsLeft := int(br.off*8) + int(64-br.bitsRead)
for bitsLeft > 0 {
if br.finished() {
return nil, io.ErrUnexpectedEOF
}
if br.bitsRead >= 56 {
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 |= uint64(low) << (br.bitsRead - 32)
br.bitsRead -= 32
br.off -= 4
} else {
for br.off > 0 {
br.value |= uint64(br.in[br.off-1]) << (br.bitsRead - 8)
br.bitsRead -= 8
br.off--
}
}
}
// end inline...
if offset >= len(out) {
return nil, errors.New("corruption detected: stream overrun 4")
}
// Read value and increment offset.
v := single[br.peekByteFast()>>shift].entry
nBits := uint8(v)
br.advance(nBits)
bitsLeft -= int(nBits)
out[offset] = uint8(v >> 8)
offset++
}
decoded += offset - dstEvery*i
err = br.close()
if err != nil {
return nil, err
}
}
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) decompress4X8bitExactly(dst, src []byte) ([]byte, error) {
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
const shift = 0
const tlSize = 1 << 8
const tlMask = tlSize - 1
single := d.dt.single[:tlSize]
// Use temp table to avoid bound checks/append penalty.
var buf [256]byte
var off uint8
var decoded int
// Decode 4 values from each decoder/loop.
const bufoff = 256 / 4
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
br[stream].fillFast()
br[stream2].fillFast()
v := single[br[stream].peekByteFast()>>shift].entry
buf[off+bufoff*stream] = uint8(v >> 8)
br[stream].advance(uint8(v))
v2 := single[br[stream2].peekByteFast()>>shift].entry
buf[off+bufoff*stream2] = uint8(v2 >> 8)
br[stream2].advance(uint8(v2))
v = single[br[stream].peekByteFast()>>shift].entry
buf[off+bufoff*stream+1] = uint8(v >> 8)
br[stream].advance(uint8(v))
v2 = single[br[stream2].peekByteFast()>>shift].entry
buf[off+bufoff*stream2+1] = uint8(v2 >> 8)
br[stream2].advance(uint8(v2))
v = single[br[stream].peekByteFast()>>shift].entry
buf[off+bufoff*stream+2] = uint8(v >> 8)
br[stream].advance(uint8(v))
v2 = single[br[stream2].peekByteFast()>>shift].entry
buf[off+bufoff*stream2+2] = uint8(v2 >> 8)
br[stream2].advance(uint8(v2))
v = single[br[stream].peekByteFast()>>shift].entry
buf[off+bufoff*stream+3] = uint8(v >> 8)
br[stream].advance(uint8(v))
v2 = single[br[stream2].peekByteFast()>>shift].entry
buf[off+bufoff*stream2+3] = uint8(v2 >> 8)
br[stream2].advance(uint8(v2))
}
{
const stream = 2
const stream2 = 3
br[stream].fillFast()
br[stream2].fillFast()
v := single[br[stream].peekByteFast()>>shift].entry
buf[off+bufoff*stream] = uint8(v >> 8)
br[stream].advance(uint8(v))
v2 := single[br[stream2].peekByteFast()>>shift].entry
buf[off+bufoff*stream2] = uint8(v2 >> 8)
br[stream2].advance(uint8(v2))
v = single[br[stream].peekByteFast()>>shift].entry
buf[off+bufoff*stream+1] = uint8(v >> 8)
br[stream].advance(uint8(v))
v2 = single[br[stream2].peekByteFast()>>shift].entry
buf[off+bufoff*stream2+1] = uint8(v2 >> 8)
br[stream2].advance(uint8(v2))
v = single[br[stream].peekByteFast()>>shift].entry
buf[off+bufoff*stream+2] = uint8(v >> 8)
br[stream].advance(uint8(v))
v2 = single[br[stream2].peekByteFast()>>shift].entry
buf[off+bufoff*stream2+2] = uint8(v2 >> 8)
br[stream2].advance(uint8(v2))
v = single[br[stream].peekByteFast()>>shift].entry
buf[off+bufoff*stream+3] = uint8(v >> 8)
br[stream].advance(uint8(v))
v2 = single[br[stream2].peekByteFast()>>shift].entry
buf[off+bufoff*stream2+3] = uint8(v2 >> 8)
br[stream2].advance(uint8(v2))
}
off += 4
if off == bufoff {
if bufoff > dstEvery {
return nil, errors.New("corruption detected: stream overrun 1")
}
copy(out, buf[:bufoff])
copy(out[dstEvery:], buf[bufoff:bufoff*2])
copy(out[dstEvery*2:], buf[bufoff*2:bufoff*3])
copy(out[dstEvery*3:], buf[bufoff*3:bufoff*4])
off = 0
out = out[bufoff:]
decoded += 256
// There must at least be 3 buffers left.
if len(out) < dstEvery*3 {
return nil, errors.New("corruption detected: stream overrun 2")
}
}
}
if off > 0 {
ioff := int(off)
if len(out) < dstEvery*3+ioff {
return nil, errors.New("corruption detected: stream overrun 3")
}
copy(out, buf[:off])
copy(out[dstEvery:dstEvery+ioff], buf[bufoff:bufoff*2])
copy(out[dstEvery*2:dstEvery*2+ioff], buf[bufoff*2:bufoff*3])
copy(out[dstEvery*3:dstEvery*3+ioff], buf[bufoff*3:bufoff*4])
decoded += int(off) * 4
out = out[off:]
}
// Decode remaining.
for i := range br {
offset := dstEvery * i
br := &br[i]
bitsLeft := int(br.off*8) + int(64-br.bitsRead)
for bitsLeft > 0 {
if br.finished() {
return nil, io.ErrUnexpectedEOF
}
if br.bitsRead >= 56 {
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 |= uint64(low) << (br.bitsRead - 32)
br.bitsRead -= 32
br.off -= 4
} else {
for br.off > 0 {
br.value |= uint64(br.in[br.off-1]) << (br.bitsRead - 8)
br.bitsRead -= 8
br.off--
}
}
}
// end inline...
if offset >= len(out) {
return nil, errors.New("corruption detected: stream overrun 4")
}
// Read value and increment offset.
v := single[br.peekByteFast()>>shift].entry
nBits := uint8(v)
br.advance(nBits)
bitsLeft -= int(nBits)
out[offset] = uint8(v >> 8)
offset++
}
decoded += offset - dstEvery*i
err = br.close()
if err != nil {
return nil, err
}
}
if dstSize != decoded {
return nil, errors.New("corruption detected: short output block")
}
return dst, nil
}
// matches will compare a decoding table to a coding table.
// Errors are written to the writer.
// Nothing will be written if table is ok.
func (s *Scratch) matches(ct cTable, w io.Writer) {
if s == nil || len(s.dt.single) == 0 {
return
}
dt := s.dt.single[:1<<s.actualTableLog]
tablelog := s.actualTableLog
ok := 0
broken := 0
for sym, enc := range ct {
errs := 0
broken++
if enc.nBits == 0 {
for _, dec := range dt {
if uint8(dec.entry>>8) == byte(sym) {
fmt.Fprintf(w, "symbol %x has decoder, but no encoder\n", sym)
errs++
break
}
}
if errs == 0 {
broken--
}
continue
}
// Unused bits in input
ub := tablelog - enc.nBits
top := enc.val << ub
// decoder looks at top bits.
dec := dt[top]
if uint8(dec.entry) != enc.nBits {
fmt.Fprintf(w, "symbol 0x%x bit size mismatch (enc: %d, dec:%d).\n", sym, enc.nBits, uint8(dec.entry))
errs++
}
if uint8(dec.entry>>8) != uint8(sym) {
fmt.Fprintf(w, "symbol 0x%x decoder output mismatch (enc: %d, dec:%d).\n", sym, sym, uint8(dec.entry>>8))
errs++
}
if errs > 0 {
fmt.Fprintf(w, "%d errros in base, stopping\n", errs)
continue
}
// Ensure that all combinations are covered.
for i := uint16(0); i < (1 << ub); i++ {
vval := top | i
dec := dt[vval]
if uint8(dec.entry) != enc.nBits {
fmt.Fprintf(w, "symbol 0x%x bit size mismatch (enc: %d, dec:%d).\n", vval, enc.nBits, uint8(dec.entry))
errs++
}
if uint8(dec.entry>>8) != uint8(sym) {
fmt.Fprintf(w, "symbol 0x%x decoder output mismatch (enc: %d, dec:%d).\n", vval, sym, uint8(dec.entry>>8))
errs++
}
if errs > 20 {
fmt.Fprintf(w, "%d errros, stopping\n", errs)
break
}
}
if errs == 0 {
ok++
broken--
}
}
if broken > 0 {
fmt.Fprintf(w, "%d broken, %d ok\n", broken, ok)
}
}