VictoriaMetrics/vendor/github.com/klauspost/compress/huff0/decompress.go

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package huff0
import (
"errors"
"fmt"
"io"
"github.com/klauspost/compress/fse"
)
type dTable struct {
single []dEntrySingle
double []dEntryDouble
}
// single-symbols decoding
type dEntrySingle struct {
byte uint8
nBits uint8
}
// double-symbols decoding
type dEntryDouble struct {
seq uint16
nBits uint8
len uint8
}
// 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 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, errors.New("input too small for table")
}
// 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 [tableLogMax + 1]uint32
weightTotal := uint32(0)
for _, v := range s.huffWeight[:s.symbolLen] {
if v > tableLogMax {
return s, nil, errors.New("corrupt input: weight too large")
}
rankStats[v]++
weightTotal += (1 << (v & 15)) >> 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)
}
for n, w := range s.huffWeight[:s.symbolLen] {
length := (uint32(1) << w) >> 1
d := dEntrySingle{
byte: uint8(n),
nBits: s.actualTableLog + 1 - w,
}
for u := rankStats[w]; u < rankStats[w]+length; u++ {
s.dt.single[u] = d
}
rankStats[w] += 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.
func (s *Scratch) Decompress1X(in []byte) (out []byte, err error) {
if len(s.dt.single) == 0 {
return nil, errors.New("no table loaded")
}
var br bitReader
err = br.init(in)
if err != nil {
return nil, err
}
s.Out = s.Out[:0]
decode := func() byte {
val := br.peekBitsFast(s.actualTableLog) /* note : actualTableLog >= 1 */
v := s.dt.single[val]
br.bitsRead += v.nBits
return v.byte
}
hasDec := func(v dEntrySingle) byte {
br.bitsRead += v.nBits
return v.byte
}
// Avoid bounds check by always having full sized table.
const tlSize = 1 << tableLogMax
const tlMask = tlSize - 1
dt := s.dt.single[:tlSize]
// Use temp table to avoid bound checks/append penalty.
var tmp = s.huffWeight[:256]
var off uint8
for br.off >= 8 {
br.fillFast()
tmp[off+0] = hasDec(dt[br.peekBitsFast(s.actualTableLog)&tlMask])
tmp[off+1] = hasDec(dt[br.peekBitsFast(s.actualTableLog)&tlMask])
br.fillFast()
tmp[off+2] = hasDec(dt[br.peekBitsFast(s.actualTableLog)&tlMask])
tmp[off+3] = hasDec(dt[br.peekBitsFast(s.actualTableLog)&tlMask])
off += 4
if off == 0 {
s.Out = append(s.Out, tmp...)
}
}
s.Out = append(s.Out, tmp[:off]...)
for !br.finished() {
br.fill()
s.Out = append(s.Out, decode())
}
return s.Out, br.close()
}
// 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.
func (s *Scratch) Decompress4X(in []byte, dstSize int) (out []byte, err error) {
if len(s.dt.single) == 0 {
return nil, errors.New("no table loaded")
}
if len(in) < 6+(4*1) {
return nil, errors.New("input too small")
}
// TODO: We do not detect when we overrun a buffer, except if the last one does.
var br [4]bitReader
start := 6
for i := 0; i < 3; i++ {
length := int(in[i*2]) | (int(in[i*2+1]) << 8)
if start+length >= len(in) {
return nil, errors.New("truncated input (or invalid offset)")
}
err = br[i].init(in[start : start+length])
if err != nil {
return nil, err
}
start += length
}
err = br[3].init(in[start:])
if err != nil {
return nil, err
}
// Prepare output
if cap(s.Out) < dstSize {
s.Out = make([]byte, 0, dstSize)
}
s.Out = s.Out[:dstSize]
// destination, offset to match first output
dstOut := s.Out
dstEvery := (dstSize + 3) / 4
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const tlSize = 1 << tableLogMax
const tlMask = tlSize - 1
single := s.dt.single[:tlSize]
decode := func(br *bitReader) byte {
val := br.peekBitsFast(s.actualTableLog) /* note : actualTableLog >= 1 */
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v := single[val&tlMask]
br.bitsRead += v.nBits
return v.byte
}
// Use temp table to avoid bound checks/append penalty.
var tmp = s.huffWeight[:256]
var off uint8
// Decode 2 values from each decoder/loop.
const bufoff = 256 / 4
bigloop:
for {
for i := range br {
if br[i].off < 4 {
break bigloop
}
br[i].fillFast()
}
tmp[off] = decode(&br[0])
tmp[off+bufoff] = decode(&br[1])
tmp[off+bufoff*2] = decode(&br[2])
tmp[off+bufoff*3] = decode(&br[3])
tmp[off+1] = decode(&br[0])
tmp[off+1+bufoff] = decode(&br[1])
tmp[off+1+bufoff*2] = decode(&br[2])
tmp[off+1+bufoff*3] = decode(&br[3])
off += 2
if off == bufoff {
if bufoff > dstEvery {
return nil, errors.New("corruption detected: stream overrun")
}
copy(dstOut, tmp[:bufoff])
copy(dstOut[dstEvery:], tmp[bufoff:bufoff*2])
copy(dstOut[dstEvery*2:], tmp[bufoff*2:bufoff*3])
copy(dstOut[dstEvery*3:], tmp[bufoff*3:bufoff*4])
off = 0
dstOut = dstOut[bufoff:]
// There must at least be 3 buffers left.
if len(dstOut) < dstEvery*3+3 {
return nil, errors.New("corruption detected: stream overrun")
}
}
}
if off > 0 {
ioff := int(off)
if len(dstOut) < dstEvery*3+ioff {
return nil, errors.New("corruption detected: stream overrun")
}
copy(dstOut, tmp[:off])
copy(dstOut[dstEvery:dstEvery+ioff], tmp[bufoff:bufoff*2])
copy(dstOut[dstEvery*2:dstEvery*2+ioff], tmp[bufoff*2:bufoff*3])
copy(dstOut[dstEvery*3:dstEvery*3+ioff], tmp[bufoff*3:bufoff*4])
dstOut = dstOut[off:]
}
for i := range br {
offset := dstEvery * i
br := &br[i]
for !br.finished() {
br.fill()
if offset >= len(dstOut) {
return nil, errors.New("corruption detected: stream overrun")
}
dstOut[offset] = decode(br)
offset++
}
err = br.close()
if err != nil {
return nil, err
}
}
return s.Out, 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 dec.byte == 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 dec.nBits != enc.nBits {
fmt.Fprintf(w, "symbol 0x%x bit size mismatch (enc: %d, dec:%d).\n", sym, enc.nBits, dec.nBits)
errs++
}
if dec.byte != uint8(sym) {
fmt.Fprintf(w, "symbol 0x%x decoder output mismatch (enc: %d, dec:%d).\n", sym, sym, dec.byte)
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 dec.nBits != enc.nBits {
fmt.Fprintf(w, "symbol 0x%x bit size mismatch (enc: %d, dec:%d).\n", vval, enc.nBits, dec.nBits)
errs++
}
if dec.byte != uint8(sym) {
fmt.Fprintf(w, "symbol 0x%x decoder output mismatch (enc: %d, dec:%d).\n", vval, sym, dec.byte)
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)
}
}