@@ -84,11 +84,11 @@ type huffmanBitWriter struct {
8484 bits uint64
8585 nbits uint
8686 bytes [bufferSize ]byte
87+ codegenFreq [codegenCodeCount ]int32
8788 nbytes int
8889 literalFreq []int32
8990 offsetFreq []int32
9091 codegen []uint8
91- codegenFreq []int32
9292 literalEncoding * huffmanEncoder
9393 offsetEncoding * huffmanEncoder
9494 codegenEncoding * huffmanEncoder
@@ -101,7 +101,6 @@ func newHuffmanBitWriter(w io.Writer) *huffmanBitWriter {
101101 literalFreq : make ([]int32 , maxNumLit ),
102102 offsetFreq : make ([]int32 , offsetCodeCount ),
103103 codegen : make ([]uint8 , maxNumLit + offsetCodeCount + 1 ),
104- codegenFreq : make ([]int32 , codegenCodeCount ),
105104 literalEncoding : newHuffmanEncoder (maxNumLit ),
106105 codegenEncoding : newHuffmanEncoder (codegenCodeCount ),
107106 offsetEncoding : newHuffmanEncoder (offsetCodeCount ),
@@ -143,12 +142,13 @@ func (w *huffmanBitWriter) writeBits(b int32, nb uint) {
143142 w .bits >>= 48
144143 w .nbits -= 48
145144 n := w .nbytes
146- w .bytes [n + 0 ] = byte (bits )
147- w .bytes [n + 1 ] = byte (bits >> 8 )
148- w .bytes [n + 2 ] = byte (bits >> 16 )
149- w .bytes [n + 3 ] = byte (bits >> 24 )
150- w .bytes [n + 4 ] = byte (bits >> 32 )
151- w .bytes [n + 5 ] = byte (bits >> 40 )
145+ bytes := w .bytes [n : n + 6 ]
146+ bytes [0 ] = byte (bits )
147+ bytes [1 ] = byte (bits >> 8 )
148+ bytes [2 ] = byte (bits >> 16 )
149+ bytes [3 ] = byte (bits >> 24 )
150+ bytes [4 ] = byte (bits >> 32 )
151+ bytes [5 ] = byte (bits >> 40 )
152152 n += 6
153153 if n >= bufferFlushSize {
154154 _ , w .err = w .w .Write (w .bytes [:n ])
@@ -293,12 +293,13 @@ func (w *huffmanBitWriter) writeCode(c hcode) {
293293 w .bits >>= 48
294294 w .nbits -= 48
295295 n := w .nbytes
296- w .bytes [n + 0 ] = byte (bits )
297- w .bytes [n + 1 ] = byte (bits >> 8 )
298- w .bytes [n + 2 ] = byte (bits >> 16 )
299- w .bytes [n + 3 ] = byte (bits >> 24 )
300- w .bytes [n + 4 ] = byte (bits >> 32 )
301- w .bytes [n + 5 ] = byte (bits >> 40 )
296+ bytes := w .bytes [n : n + 6 ]
297+ bytes [0 ] = byte (bits )
298+ bytes [1 ] = byte (bits >> 8 )
299+ bytes [2 ] = byte (bits >> 16 )
300+ bytes [3 ] = byte (bits >> 24 )
301+ bytes [4 ] = byte (bits >> 32 )
302+ bytes [5 ] = byte (bits >> 40 )
302303 n += 6
303304 if n >= bufferFlushSize {
304305 _ , w .err = w .w .Write (w .bytes [:n ])
@@ -428,13 +429,13 @@ func (w *huffmanBitWriter) writeBlock(tokens []token, eof bool, input []byte) {
428429 // Generate codegen and codegenFrequencies, which indicates how to encode
429430 // the literalEncoding and the offsetEncoding.
430431 w .generateCodegen (numLiterals , numOffsets , w .literalEncoding , w .offsetEncoding )
431- w .codegenEncoding .generate (w .codegenFreq , 7 )
432+ w .codegenEncoding .generate (w .codegenFreq [:] , 7 )
432433 numCodegens = len (w .codegenFreq )
433434 for numCodegens > 4 && w .codegenFreq [codegenOrder [numCodegens - 1 ]] == 0 {
434435 numCodegens --
435436 }
436437 dynamicHeader := int64 (3 + 5 + 5 + 4 + (3 * numCodegens )) +
437- w .codegenEncoding .bitLength (w .codegenFreq ) +
438+ w .codegenEncoding .bitLength (w .codegenFreq [:] ) +
438439 int64 (extraBits ) +
439440 int64 (w .codegenFreq [16 ]* 2 ) +
440441 int64 (w .codegenFreq [17 ]* 3 ) +
@@ -482,7 +483,7 @@ func (w *huffmanBitWriter) writeBlockDynamic(tokens []token, eof bool, input []b
482483 // Generate codegen and codegenFrequencies, which indicates how to encode
483484 // the literalEncoding and the offsetEncoding.
484485 w .generateCodegen (numLiterals , numOffsets , w .literalEncoding , w .offsetEncoding )
485- w .codegenEncoding .generate (w .codegenFreq , 7 )
486+ w .codegenEncoding .generate (w .codegenFreq [:] , 7 )
486487 numCodegens := len (w .codegenFreq )
487488 for numCodegens > 4 && w .codegenFreq [codegenOrder [numCodegens - 1 ]] == 0 {
488489 numCodegens --
@@ -609,13 +610,13 @@ func (w *huffmanBitWriter) writeBlockHuff(eof bool, input []byte) {
609610 // Generate codegen and codegenFrequencies, which indicates how to encode
610611 // the literalEncoding and the offsetEncoding.
611612 w .generateCodegen (numLiterals , numOffsets , w .literalEncoding , huffOffset )
612- w .codegenEncoding .generate (w .codegenFreq , 7 )
613+ w .codegenEncoding .generate (w .codegenFreq [:] , 7 )
613614 numCodegens = len (w .codegenFreq )
614615 for numCodegens > 4 && w .codegenFreq [codegenOrder [numCodegens - 1 ]] == 0 {
615616 numCodegens --
616617 }
617618 headerSize := int64 (3 + 5 + 5 + 4 + (3 * numCodegens )) +
618- w .codegenEncoding .bitLength (w .codegenFreq ) +
619+ w .codegenEncoding .bitLength (w .codegenFreq [:] ) +
619620 int64 (w .codegenFreq [16 ]* 2 ) +
620621 int64 (w .codegenFreq [17 ]* 3 ) +
621622 int64 (w .codegenFreq [18 ]* 7 )
@@ -639,7 +640,7 @@ func (w *huffmanBitWriter) writeBlockHuff(eof bool, input []byte) {
639640
640641 // Huffman.
641642 w .writeDynamicHeader (numLiterals , numOffsets , numCodegens , eof )
642- encoding := w .literalEncoding .codes
643+ encoding := w .literalEncoding .codes [: 257 ]
643644 n := w .nbytes
644645 for _ , t := range input {
645646 // Bitwriting inlined, ~30% speedup
@@ -653,12 +654,13 @@ func (w *huffmanBitWriter) writeBlockHuff(eof bool, input []byte) {
653654 bits := w .bits
654655 w .bits >>= 48
655656 w .nbits -= 48
656- w .bytes [n + 0 ] = byte (bits )
657- w .bytes [n + 1 ] = byte (bits >> 8 )
658- w .bytes [n + 2 ] = byte (bits >> 16 )
659- w .bytes [n + 3 ] = byte (bits >> 24 )
660- w .bytes [n + 4 ] = byte (bits >> 32 )
661- w .bytes [n + 5 ] = byte (bits >> 40 )
657+ bytes := w .bytes [n : n + 6 ]
658+ bytes [0 ] = byte (bits )
659+ bytes [1 ] = byte (bits >> 8 )
660+ bytes [2 ] = byte (bits >> 16 )
661+ bytes [3 ] = byte (bits >> 24 )
662+ bytes [4 ] = byte (bits >> 32 )
663+ bytes [5 ] = byte (bits >> 40 )
662664 n += 6
663665 if n < bufferFlushSize {
664666 continue
@@ -677,6 +679,7 @@ func (w *huffmanBitWriter) writeBlockHuff(eof bool, input []byte) {
677679//
678680// len(h) must be >= 256, and h's elements must be all zeroes.
679681func histogram (b []byte , h []int32 ) {
682+ h = h [:256 ]
680683 for _ , t := range b {
681684 h [t ]++
682685 }
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