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bit_writer: Use arrays. #177

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merged 1 commit into from Nov 10, 2019
Merged

bit_writer: Use arrays. #177

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34 changes: 16 additions & 18 deletions flate/huffman_bit_writer.go
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Expand Up @@ -87,9 +87,6 @@ type huffmanBitWriter struct {
bits uint64
nbits uint16
nbytes uint8
literalFreq []uint16
offsetFreq []uint16
codegen []uint8
literalEncoding *huffmanEncoder
offsetEncoding *huffmanEncoder
codegenEncoding *huffmanEncoder
Expand All @@ -99,7 +96,12 @@ type huffmanBitWriter struct {
logReusePenalty uint
lastHuffMan bool
bytes [256]byte
literalFreq [lengthCodesStart + 32]uint16
offsetFreq [32]uint16
codegenFreq [codegenCodeCount]uint16

// codegen must have an extra space for the final symbol.
codegen [literalCount + offsetCodeCount + 1]uint8
}

// Huffman reuse.
Expand All @@ -123,11 +125,7 @@ type huffmanBitWriter struct {

func newHuffmanBitWriter(w io.Writer) *huffmanBitWriter {
return &huffmanBitWriter{
writer: w,
literalFreq: make([]uint16, lengthCodesStart+32),
offsetFreq: make([]uint16, 32),
// codegen must have an extra space for the final symbol.
codegen: make([]uint8, literalCount+offsetCodeCount+1),
writer: w,
literalEncoding: newHuffmanEncoder(literalCount),
codegenEncoding: newHuffmanEncoder(codegenCodeCount),
offsetEncoding: newHuffmanEncoder(offsetCodeCount),
Expand Down Expand Up @@ -253,7 +251,7 @@ func (w *huffmanBitWriter) generateCodegen(numLiterals int, numOffsets int, litE
// a copy of the frequencies, and as the place where we put the result.
// This is fine because the output is always shorter than the input used
// so far.
codegen := w.codegen // cache
codegen := w.codegen[:] // cache
// Copy the concatenated code sizes to codegen. Put a marker at the end.
cgnl := codegen[:numLiterals]
for i := range cgnl {
Expand Down Expand Up @@ -356,8 +354,8 @@ func (w *huffmanBitWriter) headerSize() (size, numCodegens int) {
func (w *huffmanBitWriter) dynamicSize(litEnc, offEnc *huffmanEncoder, extraBits int) (size, numCodegens int) {
header, numCodegens := w.headerSize()
size = header +
litEnc.bitLength(w.literalFreq) +
offEnc.bitLength(w.offsetFreq) +
litEnc.bitLength(w.literalFreq[:]) +
offEnc.bitLength(w.offsetFreq[:]) +
extraBits
return size, numCodegens
}
Expand All @@ -378,8 +376,8 @@ func (w *huffmanBitWriter) extraBitSize() int {
// fixedSize returns the size of dynamically encoded data in bits.
func (w *huffmanBitWriter) fixedSize(extraBits int) int {
return 3 +
fixedLiteralEncoding.bitLength(w.literalFreq) +
fixedOffsetEncoding.bitLength(w.offsetFreq) +
fixedLiteralEncoding.bitLength(w.literalFreq[:]) +
fixedOffsetEncoding.bitLength(w.offsetFreq[:]) +
extraBits
}

Expand Down Expand Up @@ -670,9 +668,9 @@ func (w *huffmanBitWriter) writeBlockDynamic(tokens *tokens, eof bool, input []b
// and offsetEncoding.
// The number of literal and offset tokens is returned.
func (w *huffmanBitWriter) indexTokens(t *tokens, filled bool) (numLiterals, numOffsets int) {
copy(w.literalFreq, t.litHist[:])
copy(w.literalFreq[:], t.litHist[:])
copy(w.literalFreq[256:], t.extraHist[:])
copy(w.offsetFreq, t.offHist[:offsetCodeCount])
copy(w.offsetFreq[:], t.offHist[:offsetCodeCount])

if t.n == 0 {
return
Expand Down Expand Up @@ -797,17 +795,17 @@ func (w *huffmanBitWriter) writeBlockHuff(eof bool, input []byte, sync bool) {
}

// Clear histogram
for i := range w.literalFreq {
for i := range w.literalFreq[:] {
w.literalFreq[i] = 0
}
if !w.lastHuffMan {
for i := range w.offsetFreq {
for i := range w.offsetFreq[:] {
w.offsetFreq[i] = 0
}
}

// Add everything as literals
estBits := histogramSize(input, w.literalFreq, !eof && !sync) + 15
estBits := histogramSize(input, w.literalFreq[:], !eof && !sync) + 15

// Store bytes, if we don't get a reasonable improvement.
ssize, storable := w.storedSize(input)
Expand Down