mirror of
https://github.com/VictoriaMetrics/VictoriaMetrics.git
synced 2024-12-15 16:30:55 +01:00
742 lines
18 KiB
Go
742 lines
18 KiB
Go
package huff0
|
|
|
|
import (
|
|
"fmt"
|
|
"math"
|
|
"runtime"
|
|
"sync"
|
|
)
|
|
|
|
// Compress1X will compress the input.
|
|
// The output can be decoded using Decompress1X.
|
|
// Supply a Scratch object. The scratch object contains state about re-use,
|
|
// So when sharing across independent encodes, be sure to set the re-use policy.
|
|
func Compress1X(in []byte, s *Scratch) (out []byte, reUsed bool, err error) {
|
|
s, err = s.prepare(in)
|
|
if err != nil {
|
|
return nil, false, err
|
|
}
|
|
return compress(in, s, s.compress1X)
|
|
}
|
|
|
|
// Compress4X will compress the input. The input is split into 4 independent blocks
|
|
// and compressed similar to Compress1X.
|
|
// The output can be decoded using Decompress4X.
|
|
// Supply a Scratch object. The scratch object contains state about re-use,
|
|
// So when sharing across independent encodes, be sure to set the re-use policy.
|
|
func Compress4X(in []byte, s *Scratch) (out []byte, reUsed bool, err error) {
|
|
s, err = s.prepare(in)
|
|
if err != nil {
|
|
return nil, false, err
|
|
}
|
|
if false {
|
|
// TODO: compress4Xp only slightly faster.
|
|
const parallelThreshold = 8 << 10
|
|
if len(in) < parallelThreshold || runtime.GOMAXPROCS(0) == 1 {
|
|
return compress(in, s, s.compress4X)
|
|
}
|
|
return compress(in, s, s.compress4Xp)
|
|
}
|
|
return compress(in, s, s.compress4X)
|
|
}
|
|
|
|
func compress(in []byte, s *Scratch, compressor func(src []byte) ([]byte, error)) (out []byte, reUsed bool, err error) {
|
|
// Nuke previous table if we cannot reuse anyway.
|
|
if s.Reuse == ReusePolicyNone {
|
|
s.prevTable = s.prevTable[:0]
|
|
}
|
|
|
|
// Create histogram, if none was provided.
|
|
maxCount := s.maxCount
|
|
var canReuse = false
|
|
if maxCount == 0 {
|
|
maxCount, canReuse = s.countSimple(in)
|
|
} else {
|
|
canReuse = s.canUseTable(s.prevTable)
|
|
}
|
|
|
|
// We want the output size to be less than this:
|
|
wantSize := len(in)
|
|
if s.WantLogLess > 0 {
|
|
wantSize -= wantSize >> s.WantLogLess
|
|
}
|
|
|
|
// Reset for next run.
|
|
s.clearCount = true
|
|
s.maxCount = 0
|
|
if maxCount >= len(in) {
|
|
if maxCount > len(in) {
|
|
return nil, false, fmt.Errorf("maxCount (%d) > length (%d)", maxCount, len(in))
|
|
}
|
|
if len(in) == 1 {
|
|
return nil, false, ErrIncompressible
|
|
}
|
|
// One symbol, use RLE
|
|
return nil, false, ErrUseRLE
|
|
}
|
|
if maxCount == 1 || maxCount < (len(in)>>7) {
|
|
// Each symbol present maximum once or too well distributed.
|
|
return nil, false, ErrIncompressible
|
|
}
|
|
if s.Reuse == ReusePolicyMust && !canReuse {
|
|
// We must reuse, but we can't.
|
|
return nil, false, ErrIncompressible
|
|
}
|
|
if (s.Reuse == ReusePolicyPrefer || s.Reuse == ReusePolicyMust) && canReuse {
|
|
keepTable := s.cTable
|
|
keepTL := s.actualTableLog
|
|
s.cTable = s.prevTable
|
|
s.actualTableLog = s.prevTableLog
|
|
s.Out, err = compressor(in)
|
|
s.cTable = keepTable
|
|
s.actualTableLog = keepTL
|
|
if err == nil && len(s.Out) < wantSize {
|
|
s.OutData = s.Out
|
|
return s.Out, true, nil
|
|
}
|
|
if s.Reuse == ReusePolicyMust {
|
|
return nil, false, ErrIncompressible
|
|
}
|
|
// Do not attempt to re-use later.
|
|
s.prevTable = s.prevTable[:0]
|
|
}
|
|
|
|
// Calculate new table.
|
|
err = s.buildCTable()
|
|
if err != nil {
|
|
return nil, false, err
|
|
}
|
|
|
|
if false && !s.canUseTable(s.cTable) {
|
|
panic("invalid table generated")
|
|
}
|
|
|
|
if s.Reuse == ReusePolicyAllow && canReuse {
|
|
hSize := len(s.Out)
|
|
oldSize := s.prevTable.estimateSize(s.count[:s.symbolLen])
|
|
newSize := s.cTable.estimateSize(s.count[:s.symbolLen])
|
|
if oldSize <= hSize+newSize || hSize+12 >= wantSize {
|
|
// Retain cTable even if we re-use.
|
|
keepTable := s.cTable
|
|
keepTL := s.actualTableLog
|
|
|
|
s.cTable = s.prevTable
|
|
s.actualTableLog = s.prevTableLog
|
|
s.Out, err = compressor(in)
|
|
|
|
// Restore ctable.
|
|
s.cTable = keepTable
|
|
s.actualTableLog = keepTL
|
|
if err != nil {
|
|
return nil, false, err
|
|
}
|
|
if len(s.Out) >= wantSize {
|
|
return nil, false, ErrIncompressible
|
|
}
|
|
s.OutData = s.Out
|
|
return s.Out, true, nil
|
|
}
|
|
}
|
|
|
|
// Use new table
|
|
err = s.cTable.write(s)
|
|
if err != nil {
|
|
s.OutTable = nil
|
|
return nil, false, err
|
|
}
|
|
s.OutTable = s.Out
|
|
|
|
// Compress using new table
|
|
s.Out, err = compressor(in)
|
|
if err != nil {
|
|
s.OutTable = nil
|
|
return nil, false, err
|
|
}
|
|
if len(s.Out) >= wantSize {
|
|
s.OutTable = nil
|
|
return nil, false, ErrIncompressible
|
|
}
|
|
// Move current table into previous.
|
|
s.prevTable, s.prevTableLog, s.cTable = s.cTable, s.actualTableLog, s.prevTable[:0]
|
|
s.OutData = s.Out[len(s.OutTable):]
|
|
return s.Out, false, nil
|
|
}
|
|
|
|
// EstimateSizes will estimate the data sizes
|
|
func EstimateSizes(in []byte, s *Scratch) (tableSz, dataSz, reuseSz int, err error) {
|
|
s, err = s.prepare(in)
|
|
if err != nil {
|
|
return 0, 0, 0, err
|
|
}
|
|
|
|
// Create histogram, if none was provided.
|
|
tableSz, dataSz, reuseSz = -1, -1, -1
|
|
maxCount := s.maxCount
|
|
var canReuse = false
|
|
if maxCount == 0 {
|
|
maxCount, canReuse = s.countSimple(in)
|
|
} else {
|
|
canReuse = s.canUseTable(s.prevTable)
|
|
}
|
|
|
|
// We want the output size to be less than this:
|
|
wantSize := len(in)
|
|
if s.WantLogLess > 0 {
|
|
wantSize -= wantSize >> s.WantLogLess
|
|
}
|
|
|
|
// Reset for next run.
|
|
s.clearCount = true
|
|
s.maxCount = 0
|
|
if maxCount >= len(in) {
|
|
if maxCount > len(in) {
|
|
return 0, 0, 0, fmt.Errorf("maxCount (%d) > length (%d)", maxCount, len(in))
|
|
}
|
|
if len(in) == 1 {
|
|
return 0, 0, 0, ErrIncompressible
|
|
}
|
|
// One symbol, use RLE
|
|
return 0, 0, 0, ErrUseRLE
|
|
}
|
|
if maxCount == 1 || maxCount < (len(in)>>7) {
|
|
// Each symbol present maximum once or too well distributed.
|
|
return 0, 0, 0, ErrIncompressible
|
|
}
|
|
|
|
// Calculate new table.
|
|
err = s.buildCTable()
|
|
if err != nil {
|
|
return 0, 0, 0, err
|
|
}
|
|
|
|
if false && !s.canUseTable(s.cTable) {
|
|
panic("invalid table generated")
|
|
}
|
|
|
|
tableSz, err = s.cTable.estTableSize(s)
|
|
if err != nil {
|
|
return 0, 0, 0, err
|
|
}
|
|
if canReuse {
|
|
reuseSz = s.prevTable.estimateSize(s.count[:s.symbolLen])
|
|
}
|
|
dataSz = s.cTable.estimateSize(s.count[:s.symbolLen])
|
|
|
|
// Restore
|
|
return tableSz, dataSz, reuseSz, nil
|
|
}
|
|
|
|
func (s *Scratch) compress1X(src []byte) ([]byte, error) {
|
|
return s.compress1xDo(s.Out, src), nil
|
|
}
|
|
|
|
func (s *Scratch) compress1xDo(dst, src []byte) []byte {
|
|
var bw = bitWriter{out: dst}
|
|
|
|
// N is length divisible by 4.
|
|
n := len(src)
|
|
n -= n & 3
|
|
cTable := s.cTable[:256]
|
|
|
|
// Encode last bytes.
|
|
for i := len(src) & 3; i > 0; i-- {
|
|
bw.encSymbol(cTable, src[n+i-1])
|
|
}
|
|
n -= 4
|
|
if s.actualTableLog <= 8 {
|
|
for ; n >= 0; n -= 4 {
|
|
tmp := src[n : n+4]
|
|
// tmp should be len 4
|
|
bw.flush32()
|
|
bw.encFourSymbols(cTable[tmp[3]], cTable[tmp[2]], cTable[tmp[1]], cTable[tmp[0]])
|
|
}
|
|
} else {
|
|
for ; n >= 0; n -= 4 {
|
|
tmp := src[n : n+4]
|
|
// tmp should be len 4
|
|
bw.flush32()
|
|
bw.encTwoSymbols(cTable, tmp[3], tmp[2])
|
|
bw.flush32()
|
|
bw.encTwoSymbols(cTable, tmp[1], tmp[0])
|
|
}
|
|
}
|
|
bw.close()
|
|
return bw.out
|
|
}
|
|
|
|
var sixZeros [6]byte
|
|
|
|
func (s *Scratch) compress4X(src []byte) ([]byte, error) {
|
|
if len(src) < 12 {
|
|
return nil, ErrIncompressible
|
|
}
|
|
segmentSize := (len(src) + 3) / 4
|
|
|
|
// Add placeholder for output length
|
|
offsetIdx := len(s.Out)
|
|
s.Out = append(s.Out, sixZeros[:]...)
|
|
|
|
for i := 0; i < 4; i++ {
|
|
toDo := src
|
|
if len(toDo) > segmentSize {
|
|
toDo = toDo[:segmentSize]
|
|
}
|
|
src = src[len(toDo):]
|
|
|
|
idx := len(s.Out)
|
|
s.Out = s.compress1xDo(s.Out, toDo)
|
|
if len(s.Out)-idx > math.MaxUint16 {
|
|
// We cannot store the size in the jump table
|
|
return nil, ErrIncompressible
|
|
}
|
|
// Write compressed length as little endian before block.
|
|
if i < 3 {
|
|
// Last length is not written.
|
|
length := len(s.Out) - idx
|
|
s.Out[i*2+offsetIdx] = byte(length)
|
|
s.Out[i*2+offsetIdx+1] = byte(length >> 8)
|
|
}
|
|
}
|
|
|
|
return s.Out, nil
|
|
}
|
|
|
|
// compress4Xp will compress 4 streams using separate goroutines.
|
|
func (s *Scratch) compress4Xp(src []byte) ([]byte, error) {
|
|
if len(src) < 12 {
|
|
return nil, ErrIncompressible
|
|
}
|
|
// Add placeholder for output length
|
|
s.Out = s.Out[:6]
|
|
|
|
segmentSize := (len(src) + 3) / 4
|
|
var wg sync.WaitGroup
|
|
wg.Add(4)
|
|
for i := 0; i < 4; i++ {
|
|
toDo := src
|
|
if len(toDo) > segmentSize {
|
|
toDo = toDo[:segmentSize]
|
|
}
|
|
src = src[len(toDo):]
|
|
|
|
// Separate goroutine for each block.
|
|
go func(i int) {
|
|
s.tmpOut[i] = s.compress1xDo(s.tmpOut[i][:0], toDo)
|
|
wg.Done()
|
|
}(i)
|
|
}
|
|
wg.Wait()
|
|
for i := 0; i < 4; i++ {
|
|
o := s.tmpOut[i]
|
|
if len(o) > math.MaxUint16 {
|
|
// We cannot store the size in the jump table
|
|
return nil, ErrIncompressible
|
|
}
|
|
// Write compressed length as little endian before block.
|
|
if i < 3 {
|
|
// Last length is not written.
|
|
s.Out[i*2] = byte(len(o))
|
|
s.Out[i*2+1] = byte(len(o) >> 8)
|
|
}
|
|
|
|
// Write output.
|
|
s.Out = append(s.Out, o...)
|
|
}
|
|
return s.Out, nil
|
|
}
|
|
|
|
// countSimple will create a simple histogram in s.count.
|
|
// Returns the biggest count.
|
|
// Does not update s.clearCount.
|
|
func (s *Scratch) countSimple(in []byte) (max int, reuse bool) {
|
|
reuse = true
|
|
for _, v := range in {
|
|
s.count[v]++
|
|
}
|
|
m := uint32(0)
|
|
if len(s.prevTable) > 0 {
|
|
for i, v := range s.count[:] {
|
|
if v == 0 {
|
|
continue
|
|
}
|
|
if v > m {
|
|
m = v
|
|
}
|
|
s.symbolLen = uint16(i) + 1
|
|
if i >= len(s.prevTable) {
|
|
reuse = false
|
|
} else if s.prevTable[i].nBits == 0 {
|
|
reuse = false
|
|
}
|
|
}
|
|
return int(m), reuse
|
|
}
|
|
for i, v := range s.count[:] {
|
|
if v == 0 {
|
|
continue
|
|
}
|
|
if v > m {
|
|
m = v
|
|
}
|
|
s.symbolLen = uint16(i) + 1
|
|
}
|
|
return int(m), false
|
|
}
|
|
|
|
func (s *Scratch) canUseTable(c cTable) bool {
|
|
if len(c) < int(s.symbolLen) {
|
|
return false
|
|
}
|
|
for i, v := range s.count[:s.symbolLen] {
|
|
if v != 0 && c[i].nBits == 0 {
|
|
return false
|
|
}
|
|
}
|
|
return true
|
|
}
|
|
|
|
//lint:ignore U1000 used for debugging
|
|
func (s *Scratch) validateTable(c cTable) bool {
|
|
if len(c) < int(s.symbolLen) {
|
|
return false
|
|
}
|
|
for i, v := range s.count[:s.symbolLen] {
|
|
if v != 0 {
|
|
if c[i].nBits == 0 {
|
|
return false
|
|
}
|
|
if c[i].nBits > s.actualTableLog {
|
|
return false
|
|
}
|
|
}
|
|
}
|
|
return true
|
|
}
|
|
|
|
// minTableLog provides the minimum logSize to safely represent a distribution.
|
|
func (s *Scratch) minTableLog() uint8 {
|
|
minBitsSrc := highBit32(uint32(s.br.remain())) + 1
|
|
minBitsSymbols := highBit32(uint32(s.symbolLen-1)) + 2
|
|
if minBitsSrc < minBitsSymbols {
|
|
return uint8(minBitsSrc)
|
|
}
|
|
return uint8(minBitsSymbols)
|
|
}
|
|
|
|
// optimalTableLog calculates and sets the optimal tableLog in s.actualTableLog
|
|
func (s *Scratch) optimalTableLog() {
|
|
tableLog := s.TableLog
|
|
minBits := s.minTableLog()
|
|
maxBitsSrc := uint8(highBit32(uint32(s.br.remain()-1))) - 1
|
|
if maxBitsSrc < tableLog {
|
|
// Accuracy can be reduced
|
|
tableLog = maxBitsSrc
|
|
}
|
|
if minBits > tableLog {
|
|
tableLog = minBits
|
|
}
|
|
// Need a minimum to safely represent all symbol values
|
|
if tableLog < minTablelog {
|
|
tableLog = minTablelog
|
|
}
|
|
if tableLog > tableLogMax {
|
|
tableLog = tableLogMax
|
|
}
|
|
s.actualTableLog = tableLog
|
|
}
|
|
|
|
type cTableEntry struct {
|
|
val uint16
|
|
nBits uint8
|
|
// We have 8 bits extra
|
|
}
|
|
|
|
const huffNodesMask = huffNodesLen - 1
|
|
|
|
func (s *Scratch) buildCTable() error {
|
|
s.optimalTableLog()
|
|
s.huffSort()
|
|
if cap(s.cTable) < maxSymbolValue+1 {
|
|
s.cTable = make([]cTableEntry, s.symbolLen, maxSymbolValue+1)
|
|
} else {
|
|
s.cTable = s.cTable[:s.symbolLen]
|
|
for i := range s.cTable {
|
|
s.cTable[i] = cTableEntry{}
|
|
}
|
|
}
|
|
|
|
var startNode = int16(s.symbolLen)
|
|
nonNullRank := s.symbolLen - 1
|
|
|
|
nodeNb := startNode
|
|
huffNode := s.nodes[1 : huffNodesLen+1]
|
|
|
|
// This overlays the slice above, but allows "-1" index lookups.
|
|
// Different from reference implementation.
|
|
huffNode0 := s.nodes[0 : huffNodesLen+1]
|
|
|
|
for huffNode[nonNullRank].count() == 0 {
|
|
nonNullRank--
|
|
}
|
|
|
|
lowS := int16(nonNullRank)
|
|
nodeRoot := nodeNb + lowS - 1
|
|
lowN := nodeNb
|
|
huffNode[nodeNb].setCount(huffNode[lowS].count() + huffNode[lowS-1].count())
|
|
huffNode[lowS].setParent(nodeNb)
|
|
huffNode[lowS-1].setParent(nodeNb)
|
|
nodeNb++
|
|
lowS -= 2
|
|
for n := nodeNb; n <= nodeRoot; n++ {
|
|
huffNode[n].setCount(1 << 30)
|
|
}
|
|
// fake entry, strong barrier
|
|
huffNode0[0].setCount(1 << 31)
|
|
|
|
// create parents
|
|
for nodeNb <= nodeRoot {
|
|
var n1, n2 int16
|
|
if huffNode0[lowS+1].count() < huffNode0[lowN+1].count() {
|
|
n1 = lowS
|
|
lowS--
|
|
} else {
|
|
n1 = lowN
|
|
lowN++
|
|
}
|
|
if huffNode0[lowS+1].count() < huffNode0[lowN+1].count() {
|
|
n2 = lowS
|
|
lowS--
|
|
} else {
|
|
n2 = lowN
|
|
lowN++
|
|
}
|
|
|
|
huffNode[nodeNb].setCount(huffNode0[n1+1].count() + huffNode0[n2+1].count())
|
|
huffNode0[n1+1].setParent(nodeNb)
|
|
huffNode0[n2+1].setParent(nodeNb)
|
|
nodeNb++
|
|
}
|
|
|
|
// distribute weights (unlimited tree height)
|
|
huffNode[nodeRoot].setNbBits(0)
|
|
for n := nodeRoot - 1; n >= startNode; n-- {
|
|
huffNode[n].setNbBits(huffNode[huffNode[n].parent()].nbBits() + 1)
|
|
}
|
|
for n := uint16(0); n <= nonNullRank; n++ {
|
|
huffNode[n].setNbBits(huffNode[huffNode[n].parent()].nbBits() + 1)
|
|
}
|
|
s.actualTableLog = s.setMaxHeight(int(nonNullRank))
|
|
maxNbBits := s.actualTableLog
|
|
|
|
// fill result into tree (val, nbBits)
|
|
if maxNbBits > tableLogMax {
|
|
return fmt.Errorf("internal error: maxNbBits (%d) > tableLogMax (%d)", maxNbBits, tableLogMax)
|
|
}
|
|
var nbPerRank [tableLogMax + 1]uint16
|
|
var valPerRank [16]uint16
|
|
for _, v := range huffNode[:nonNullRank+1] {
|
|
nbPerRank[v.nbBits()]++
|
|
}
|
|
// determine stating value per rank
|
|
{
|
|
min := uint16(0)
|
|
for n := maxNbBits; n > 0; n-- {
|
|
// get starting value within each rank
|
|
valPerRank[n] = min
|
|
min += nbPerRank[n]
|
|
min >>= 1
|
|
}
|
|
}
|
|
|
|
// push nbBits per symbol, symbol order
|
|
for _, v := range huffNode[:nonNullRank+1] {
|
|
s.cTable[v.symbol()].nBits = v.nbBits()
|
|
}
|
|
|
|
// assign value within rank, symbol order
|
|
t := s.cTable[:s.symbolLen]
|
|
for n, val := range t {
|
|
nbits := val.nBits & 15
|
|
v := valPerRank[nbits]
|
|
t[n].val = v
|
|
valPerRank[nbits] = v + 1
|
|
}
|
|
|
|
return nil
|
|
}
|
|
|
|
// huffSort will sort symbols, decreasing order.
|
|
func (s *Scratch) huffSort() {
|
|
type rankPos struct {
|
|
base uint32
|
|
current uint32
|
|
}
|
|
|
|
// Clear nodes
|
|
nodes := s.nodes[:huffNodesLen+1]
|
|
s.nodes = nodes
|
|
nodes = nodes[1 : huffNodesLen+1]
|
|
|
|
// Sort into buckets based on length of symbol count.
|
|
var rank [32]rankPos
|
|
for _, v := range s.count[:s.symbolLen] {
|
|
r := highBit32(v+1) & 31
|
|
rank[r].base++
|
|
}
|
|
// maxBitLength is log2(BlockSizeMax) + 1
|
|
const maxBitLength = 18 + 1
|
|
for n := maxBitLength; n > 0; n-- {
|
|
rank[n-1].base += rank[n].base
|
|
}
|
|
for n := range rank[:maxBitLength] {
|
|
rank[n].current = rank[n].base
|
|
}
|
|
for n, c := range s.count[:s.symbolLen] {
|
|
r := (highBit32(c+1) + 1) & 31
|
|
pos := rank[r].current
|
|
rank[r].current++
|
|
prev := nodes[(pos-1)&huffNodesMask]
|
|
for pos > rank[r].base && c > prev.count() {
|
|
nodes[pos&huffNodesMask] = prev
|
|
pos--
|
|
prev = nodes[(pos-1)&huffNodesMask]
|
|
}
|
|
nodes[pos&huffNodesMask] = makeNodeElt(c, byte(n))
|
|
}
|
|
}
|
|
|
|
func (s *Scratch) setMaxHeight(lastNonNull int) uint8 {
|
|
maxNbBits := s.actualTableLog
|
|
huffNode := s.nodes[1 : huffNodesLen+1]
|
|
//huffNode = huffNode[: huffNodesLen]
|
|
|
|
largestBits := huffNode[lastNonNull].nbBits()
|
|
|
|
// early exit : no elt > maxNbBits
|
|
if largestBits <= maxNbBits {
|
|
return largestBits
|
|
}
|
|
totalCost := int(0)
|
|
baseCost := int(1) << (largestBits - maxNbBits)
|
|
n := uint32(lastNonNull)
|
|
|
|
for huffNode[n].nbBits() > maxNbBits {
|
|
totalCost += baseCost - (1 << (largestBits - huffNode[n].nbBits()))
|
|
huffNode[n].setNbBits(maxNbBits)
|
|
n--
|
|
}
|
|
// n stops at huffNode[n].nbBits <= maxNbBits
|
|
|
|
for huffNode[n].nbBits() == maxNbBits {
|
|
n--
|
|
}
|
|
// n end at index of smallest symbol using < maxNbBits
|
|
|
|
// renorm totalCost
|
|
totalCost >>= largestBits - maxNbBits /* note : totalCost is necessarily a multiple of baseCost */
|
|
|
|
// repay normalized cost
|
|
{
|
|
const noSymbol = 0xF0F0F0F0
|
|
var rankLast [tableLogMax + 2]uint32
|
|
|
|
for i := range rankLast[:] {
|
|
rankLast[i] = noSymbol
|
|
}
|
|
|
|
// Get pos of last (smallest) symbol per rank
|
|
{
|
|
currentNbBits := maxNbBits
|
|
for pos := int(n); pos >= 0; pos-- {
|
|
if huffNode[pos].nbBits() >= currentNbBits {
|
|
continue
|
|
}
|
|
currentNbBits = huffNode[pos].nbBits() // < maxNbBits
|
|
rankLast[maxNbBits-currentNbBits] = uint32(pos)
|
|
}
|
|
}
|
|
|
|
for totalCost > 0 {
|
|
nBitsToDecrease := uint8(highBit32(uint32(totalCost))) + 1
|
|
|
|
for ; nBitsToDecrease > 1; nBitsToDecrease-- {
|
|
highPos := rankLast[nBitsToDecrease]
|
|
lowPos := rankLast[nBitsToDecrease-1]
|
|
if highPos == noSymbol {
|
|
continue
|
|
}
|
|
if lowPos == noSymbol {
|
|
break
|
|
}
|
|
highTotal := huffNode[highPos].count()
|
|
lowTotal := 2 * huffNode[lowPos].count()
|
|
if highTotal <= lowTotal {
|
|
break
|
|
}
|
|
}
|
|
// only triggered when no more rank 1 symbol left => find closest one (note : there is necessarily at least one !)
|
|
// HUF_MAX_TABLELOG test just to please gcc 5+; but it should not be necessary
|
|
// FIXME: try to remove
|
|
for (nBitsToDecrease <= tableLogMax) && (rankLast[nBitsToDecrease] == noSymbol) {
|
|
nBitsToDecrease++
|
|
}
|
|
totalCost -= 1 << (nBitsToDecrease - 1)
|
|
if rankLast[nBitsToDecrease-1] == noSymbol {
|
|
// this rank is no longer empty
|
|
rankLast[nBitsToDecrease-1] = rankLast[nBitsToDecrease]
|
|
}
|
|
huffNode[rankLast[nBitsToDecrease]].setNbBits(1 +
|
|
huffNode[rankLast[nBitsToDecrease]].nbBits())
|
|
if rankLast[nBitsToDecrease] == 0 {
|
|
/* special case, reached largest symbol */
|
|
rankLast[nBitsToDecrease] = noSymbol
|
|
} else {
|
|
rankLast[nBitsToDecrease]--
|
|
if huffNode[rankLast[nBitsToDecrease]].nbBits() != maxNbBits-nBitsToDecrease {
|
|
rankLast[nBitsToDecrease] = noSymbol /* this rank is now empty */
|
|
}
|
|
}
|
|
}
|
|
|
|
for totalCost < 0 { /* Sometimes, cost correction overshoot */
|
|
if rankLast[1] == noSymbol { /* special case : no rank 1 symbol (using maxNbBits-1); let's create one from largest rank 0 (using maxNbBits) */
|
|
for huffNode[n].nbBits() == maxNbBits {
|
|
n--
|
|
}
|
|
huffNode[n+1].setNbBits(huffNode[n+1].nbBits() - 1)
|
|
rankLast[1] = n + 1
|
|
totalCost++
|
|
continue
|
|
}
|
|
huffNode[rankLast[1]+1].setNbBits(huffNode[rankLast[1]+1].nbBits() - 1)
|
|
rankLast[1]++
|
|
totalCost++
|
|
}
|
|
}
|
|
return maxNbBits
|
|
}
|
|
|
|
// A nodeElt is the fields
|
|
//
|
|
// count uint32
|
|
// parent uint16
|
|
// symbol byte
|
|
// nbBits uint8
|
|
//
|
|
// in some order, all squashed into an integer so that the compiler
|
|
// always loads and stores entire nodeElts instead of separate fields.
|
|
type nodeElt uint64
|
|
|
|
func makeNodeElt(count uint32, symbol byte) nodeElt {
|
|
return nodeElt(count) | nodeElt(symbol)<<48
|
|
}
|
|
|
|
func (e *nodeElt) count() uint32 { return uint32(*e) }
|
|
func (e *nodeElt) parent() uint16 { return uint16(*e >> 32) }
|
|
func (e *nodeElt) symbol() byte { return byte(*e >> 48) }
|
|
func (e *nodeElt) nbBits() uint8 { return uint8(*e >> 56) }
|
|
|
|
func (e *nodeElt) setCount(c uint32) { *e = (*e)&0xffffffff00000000 | nodeElt(c) }
|
|
func (e *nodeElt) setParent(p int16) { *e = (*e)&0xffff0000ffffffff | nodeElt(uint16(p))<<32 }
|
|
func (e *nodeElt) setNbBits(n uint8) { *e = (*e)&0x00ffffffffffffff | nodeElt(n)<<56 }
|