diff options
Diffstat (limited to 'vendor/github.com/klauspost/compress/flate/huffman_code.go')
| -rw-r--r-- | vendor/github.com/klauspost/compress/flate/huffman_code.go | 40 |
1 files changed, 26 insertions, 14 deletions
diff --git a/vendor/github.com/klauspost/compress/flate/huffman_code.go b/vendor/github.com/klauspost/compress/flate/huffman_code.go index f35e00261..9ab497c27 100644 --- a/vendor/github.com/klauspost/compress/flate/huffman_code.go +++ b/vendor/github.com/klauspost/compress/flate/huffman_code.go @@ -17,7 +17,8 @@ const ( // hcode is a huffman code with a bit code and bit length. type hcode struct { - code, len uint16 + code uint16 + len uint8 } type huffmanEncoder struct { @@ -56,7 +57,7 @@ type levelInfo struct { } // set sets the code and length of an hcode. -func (h *hcode) set(code uint16, length uint16) { +func (h *hcode) set(code uint16, length uint8) { h.len = length h.code = code } @@ -80,7 +81,7 @@ func generateFixedLiteralEncoding() *huffmanEncoder { var ch uint16 for ch = 0; ch < literalCount; ch++ { var bits uint16 - var size uint16 + var size uint8 switch { case ch < 144: // size 8, 000110000 .. 10111111 @@ -99,7 +100,7 @@ func generateFixedLiteralEncoding() *huffmanEncoder { bits = ch + 192 - 280 size = 8 } - codes[ch] = hcode{code: reverseBits(bits, byte(size)), len: size} + codes[ch] = hcode{code: reverseBits(bits, size), len: size} } return h } @@ -187,14 +188,19 @@ func (h *huffmanEncoder) bitCounts(list []literalNode, maxBits int32) []int32 { // of the level j ancestor. var leafCounts [maxBitsLimit][maxBitsLimit]int32 + // Descending to only have 1 bounds check. + l2f := int32(list[2].freq) + l1f := int32(list[1].freq) + l0f := int32(list[0].freq) + int32(list[1].freq) + for level := int32(1); level <= maxBits; level++ { // For every level, the first two items are the first two characters. // We initialize the levels as if we had already figured this out. levels[level] = levelInfo{ level: level, - lastFreq: int32(list[1].freq), - nextCharFreq: int32(list[2].freq), - nextPairFreq: int32(list[0].freq) + int32(list[1].freq), + lastFreq: l1f, + nextCharFreq: l2f, + nextPairFreq: l0f, } leafCounts[level][level] = 2 if level == 1 { @@ -205,8 +211,8 @@ func (h *huffmanEncoder) bitCounts(list []literalNode, maxBits int32) []int32 { // We need a total of 2*n - 2 items at top level and have already generated 2. levels[maxBits].needed = 2*n - 4 - level := maxBits - for { + level := uint32(maxBits) + for level < 16 { l := &levels[level] if l.nextPairFreq == math.MaxInt32 && l.nextCharFreq == math.MaxInt32 { // We've run out of both leafs and pairs. @@ -238,7 +244,13 @@ func (h *huffmanEncoder) bitCounts(list []literalNode, maxBits int32) []int32 { // more values in the level below l.lastFreq = l.nextPairFreq // Take leaf counts from the lower level, except counts[level] remains the same. - copy(leafCounts[level][:level], leafCounts[level-1][:level]) + if true { + save := leafCounts[level][level] + leafCounts[level] = leafCounts[level-1] + leafCounts[level][level] = save + } else { + copy(leafCounts[level][:level], leafCounts[level-1][:level]) + } levels[l.level-1].needed = 2 } @@ -296,7 +308,7 @@ func (h *huffmanEncoder) assignEncodingAndSize(bitCount []int32, list []literalN sortByLiteral(chunk) for _, node := range chunk { - h.codes[node.literal] = hcode{code: reverseBits(code, uint8(n)), len: uint16(n)} + h.codes[node.literal] = hcode{code: reverseBits(code, uint8(n)), len: uint8(n)} code++ } list = list[0 : len(list)-int(bits)] @@ -309,6 +321,7 @@ func (h *huffmanEncoder) assignEncodingAndSize(bitCount []int32, list []literalN // maxBits The maximum number of bits to use for any literal. func (h *huffmanEncoder) generate(freq []uint16, maxBits int32) { list := h.freqcache[:len(freq)+1] + codes := h.codes[:len(freq)] // Number of non-zero literals count := 0 // Set list to be the set of all non-zero literals and their frequencies @@ -317,11 +330,10 @@ func (h *huffmanEncoder) generate(freq []uint16, maxBits int32) { list[count] = literalNode{uint16(i), f} count++ } else { - list[count] = literalNode{} - h.codes[i].len = 0 + codes[i].len = 0 } } - list[len(freq)] = literalNode{} + list[count] = literalNode{} list = list[:count] if count <= 2 { |