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 | 417 |
1 files changed, 0 insertions, 417 deletions
diff --git a/vendor/github.com/klauspost/compress/flate/huffman_code.go b/vendor/github.com/klauspost/compress/flate/huffman_code.go deleted file mode 100644 index be7b58b47..000000000 --- a/vendor/github.com/klauspost/compress/flate/huffman_code.go +++ /dev/null @@ -1,417 +0,0 @@ -// Copyright 2009 The Go Authors. All rights reserved. -// Use of this source code is governed by a BSD-style -// license that can be found in the LICENSE file. - -package flate - -import ( - "math" - "math/bits" -) - -const ( - maxBitsLimit = 16 - // number of valid literals - literalCount = 286 -) - -// hcode is a huffman code with a bit code and bit length. -type hcode uint32 - -func (h hcode) len() uint8 { - return uint8(h) -} - -func (h hcode) code64() uint64 { - return uint64(h >> 8) -} - -func (h hcode) zero() bool { - return h == 0 -} - -type huffmanEncoder struct { - codes []hcode - bitCount [17]int32 - - // Allocate a reusable buffer with the longest possible frequency table. - // Possible lengths are codegenCodeCount, offsetCodeCount and literalCount. - // The largest of these is literalCount, so we allocate for that case. - freqcache [literalCount + 1]literalNode -} - -type literalNode struct { - literal uint16 - freq uint16 -} - -// A levelInfo describes the state of the constructed tree for a given depth. -type levelInfo struct { - // Our level. for better printing - level int32 - - // The frequency of the last node at this level - lastFreq int32 - - // The frequency of the next character to add to this level - nextCharFreq int32 - - // The frequency of the next pair (from level below) to add to this level. - // Only valid if the "needed" value of the next lower level is 0. - nextPairFreq int32 - - // The number of chains remaining to generate for this level before moving - // up to the next level - needed int32 -} - -// set sets the code and length of an hcode. -func (h *hcode) set(code uint16, length uint8) { - *h = hcode(length) | (hcode(code) << 8) -} - -func newhcode(code uint16, length uint8) hcode { - return hcode(length) | (hcode(code) << 8) -} - -func reverseBits(number uint16, bitLength byte) uint16 { - return bits.Reverse16(number << ((16 - bitLength) & 15)) -} - -func maxNode() literalNode { return literalNode{math.MaxUint16, math.MaxUint16} } - -func newHuffmanEncoder(size int) *huffmanEncoder { - // Make capacity to next power of two. - c := uint(bits.Len32(uint32(size - 1))) - return &huffmanEncoder{codes: make([]hcode, size, 1<<c)} -} - -// Generates a HuffmanCode corresponding to the fixed literal table -func generateFixedLiteralEncoding() *huffmanEncoder { - h := newHuffmanEncoder(literalCount) - codes := h.codes - var ch uint16 - for ch = 0; ch < literalCount; ch++ { - var bits uint16 - var size uint8 - switch { - case ch < 144: - // size 8, 000110000 .. 10111111 - bits = ch + 48 - size = 8 - case ch < 256: - // size 9, 110010000 .. 111111111 - bits = ch + 400 - 144 - size = 9 - case ch < 280: - // size 7, 0000000 .. 0010111 - bits = ch - 256 - size = 7 - default: - // size 8, 11000000 .. 11000111 - bits = ch + 192 - 280 - size = 8 - } - codes[ch] = newhcode(reverseBits(bits, size), size) - } - return h -} - -func generateFixedOffsetEncoding() *huffmanEncoder { - h := newHuffmanEncoder(30) - codes := h.codes - for ch := range codes { - codes[ch] = newhcode(reverseBits(uint16(ch), 5), 5) - } - return h -} - -var fixedLiteralEncoding = generateFixedLiteralEncoding() -var fixedOffsetEncoding = generateFixedOffsetEncoding() - -func (h *huffmanEncoder) bitLength(freq []uint16) int { - var total int - for i, f := range freq { - if f != 0 { - total += int(f) * int(h.codes[i].len()) - } - } - return total -} - -func (h *huffmanEncoder) bitLengthRaw(b []byte) int { - var total int - for _, f := range b { - total += int(h.codes[f].len()) - } - return total -} - -// canReuseBits returns the number of bits or math.MaxInt32 if the encoder cannot be reused. -func (h *huffmanEncoder) canReuseBits(freq []uint16) int { - var total int - for i, f := range freq { - if f != 0 { - code := h.codes[i] - if code.zero() { - return math.MaxInt32 - } - total += int(f) * int(code.len()) - } - } - return total -} - -// Return the number of literals assigned to each bit size in the Huffman encoding -// -// This method is only called when list.length >= 3 -// The cases of 0, 1, and 2 literals are handled by special case code. -// -// list An array of the literals with non-zero frequencies -// -// and their associated frequencies. The array is in order of increasing -// frequency, and has as its last element a special element with frequency -// MaxInt32 -// -// maxBits The maximum number of bits that should be used to encode any literal. -// -// Must be less than 16. -// -// return An integer array in which array[i] indicates the number of literals -// -// that should be encoded in i bits. -func (h *huffmanEncoder) bitCounts(list []literalNode, maxBits int32) []int32 { - if maxBits >= maxBitsLimit { - panic("flate: maxBits too large") - } - n := int32(len(list)) - list = list[0 : n+1] - list[n] = maxNode() - - // The tree can't have greater depth than n - 1, no matter what. This - // saves a little bit of work in some small cases - if maxBits > n-1 { - maxBits = n - 1 - } - - // Create information about each of the levels. - // A bogus "Level 0" whose sole purpose is so that - // level1.prev.needed==0. This makes level1.nextPairFreq - // be a legitimate value that never gets chosen. - var levels [maxBitsLimit]levelInfo - // leafCounts[i] counts the number of literals at the left - // of ancestors of the rightmost node at level i. - // leafCounts[i][j] is the number of literals at the left - // 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: l1f, - nextCharFreq: l2f, - nextPairFreq: l0f, - } - leafCounts[level][level] = 2 - if level == 1 { - levels[level].nextPairFreq = math.MaxInt32 - } - } - - // We need a total of 2*n - 2 items at top level and have already generated 2. - levels[maxBits].needed = 2*n - 4 - - 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. - // End all calculations for this level. - // To make sure we never come back to this level or any lower level, - // set nextPairFreq impossibly large. - l.needed = 0 - levels[level+1].nextPairFreq = math.MaxInt32 - level++ - continue - } - - prevFreq := l.lastFreq - if l.nextCharFreq < l.nextPairFreq { - // The next item on this row is a leaf node. - n := leafCounts[level][level] + 1 - l.lastFreq = l.nextCharFreq - // Lower leafCounts are the same of the previous node. - leafCounts[level][level] = n - e := list[n] - if e.literal < math.MaxUint16 { - l.nextCharFreq = int32(e.freq) - } else { - l.nextCharFreq = math.MaxInt32 - } - } else { - // The next item on this row is a pair from the previous row. - // nextPairFreq isn't valid until we generate two - // more values in the level below - l.lastFreq = l.nextPairFreq - // Take leaf counts from the lower level, except counts[level] remains the same. - 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 - } - - if l.needed--; l.needed == 0 { - // We've done everything we need to do for this level. - // Continue calculating one level up. Fill in nextPairFreq - // of that level with the sum of the two nodes we've just calculated on - // this level. - if l.level == maxBits { - // All done! - break - } - levels[l.level+1].nextPairFreq = prevFreq + l.lastFreq - level++ - } else { - // If we stole from below, move down temporarily to replenish it. - for levels[level-1].needed > 0 { - level-- - } - } - } - - // Somethings is wrong if at the end, the top level is null or hasn't used - // all of the leaves. - if leafCounts[maxBits][maxBits] != n { - panic("leafCounts[maxBits][maxBits] != n") - } - - bitCount := h.bitCount[:maxBits+1] - bits := 1 - counts := &leafCounts[maxBits] - for level := maxBits; level > 0; level-- { - // chain.leafCount gives the number of literals requiring at least "bits" - // bits to encode. - bitCount[bits] = counts[level] - counts[level-1] - bits++ - } - return bitCount -} - -// Look at the leaves and assign them a bit count and an encoding as specified -// in RFC 1951 3.2.2 -func (h *huffmanEncoder) assignEncodingAndSize(bitCount []int32, list []literalNode) { - code := uint16(0) - for n, bits := range bitCount { - code <<= 1 - if n == 0 || bits == 0 { - continue - } - // The literals list[len(list)-bits] .. list[len(list)-bits] - // are encoded using "bits" bits, and get the values - // code, code + 1, .... The code values are - // assigned in literal order (not frequency order). - chunk := list[len(list)-int(bits):] - - sortByLiteral(chunk) - for _, node := range chunk { - h.codes[node.literal] = newhcode(reverseBits(code, uint8(n)), uint8(n)) - code++ - } - list = list[0 : len(list)-int(bits)] - } -} - -// Update this Huffman Code object to be the minimum code for the specified frequency count. -// -// freq An array of frequencies, in which frequency[i] gives the frequency of literal i. -// 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 - for i, f := range freq { - if f != 0 { - list[count] = literalNode{uint16(i), f} - count++ - } else { - codes[i] = 0 - } - } - list[count] = literalNode{} - - list = list[:count] - if count <= 2 { - // Handle the small cases here, because they are awkward for the general case code. With - // two or fewer literals, everything has bit length 1. - for i, node := range list { - // "list" is in order of increasing literal value. - h.codes[node.literal].set(uint16(i), 1) - } - return - } - sortByFreq(list) - - // Get the number of literals for each bit count - bitCount := h.bitCounts(list, maxBits) - // And do the assignment - h.assignEncodingAndSize(bitCount, list) -} - -// atLeastOne clamps the result between 1 and 15. -func atLeastOne(v float32) float32 { - if v < 1 { - return 1 - } - if v > 15 { - return 15 - } - return v -} - -func histogram(b []byte, h []uint16) { - if true && len(b) >= 8<<10 { - // Split for bigger inputs - histogramSplit(b, h) - } else { - h = h[:256] - for _, t := range b { - h[t]++ - } - } -} - -func histogramSplit(b []byte, h []uint16) { - // Tested, and slightly faster than 2-way. - // Writing to separate arrays and combining is also slightly slower. - h = h[:256] - for len(b)&3 != 0 { - h[b[0]]++ - b = b[1:] - } - n := len(b) / 4 - x, y, z, w := b[:n], b[n:], b[n+n:], b[n+n+n:] - y, z, w = y[:len(x)], z[:len(x)], w[:len(x)] - for i, t := range x { - v0 := &h[t] - v1 := &h[y[i]] - v3 := &h[w[i]] - v2 := &h[z[i]] - *v0++ - *v1++ - *v2++ - *v3++ - } -} |