Move modules/gzip to gitea.com/macaron/gzip (#9058)

* Move modules/gzip to gitea.com/macaron/gzip

* Fix vendor

vendor/github.com/klauspost/compress/flate/huffman_code.go

@@ -6,9 +6,16 @@ package flate
 
 import (
 	"math"
+	"math/bits"
 	"sort"
 )
 
+const (
+	maxBitsLimit = 16
+	// number of valid literals
+	literalCount = 286
+)
+
 // hcode is a huffman code with a bit code and bit length.
 type hcode struct {
 	code, len uint16
@@ -24,7 +31,7 @@ type huffmanEncoder struct {
 
 type literalNode struct {
 	literal uint16
-	freq    int32
+	freq    uint16
 }
 
 // A levelInfo describes the state of the constructed tree for a given depth.
@@ -53,18 +60,24 @@ func (h *hcode) set(code uint16, length uint16) {
 	h.code = code
 }
 
-func maxNode() literalNode { return literalNode{math.MaxUint16, math.MaxInt32} }
+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 {
-	return &huffmanEncoder{codes: make([]hcode, size)}
+	// 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(maxNumLit)
+	h := newHuffmanEncoder(literalCount)
 	codes := h.codes
 	var ch uint16
-	for ch = 0; ch < maxNumLit; ch++ {
+	for ch = 0; ch < literalCount; ch++ {
 		var bits uint16
 		var size uint16
 		switch {
@@ -105,7 +118,7 @@ func generateFixedOffsetEncoding() *huffmanEncoder {
 var fixedLiteralEncoding *huffmanEncoder = generateFixedLiteralEncoding()
 var fixedOffsetEncoding *huffmanEncoder = generateFixedOffsetEncoding()
 
-func (h *huffmanEncoder) bitLength(freq []int32) int {
+func (h *huffmanEncoder) bitLength(freq []uint16) int {
 	var total int
 	for i, f := range freq {
 		if f != 0 {
@@ -115,8 +128,6 @@ func (h *huffmanEncoder) bitLength(freq []int32) int {
 	return total
 }
 
-const maxBitsLimit = 16
-
 // Return the number of literals assigned to each bit size in the Huffman encoding
 //
 // This method is only called when list.length >= 3
@@ -160,9 +171,9 @@ func (h *huffmanEncoder) bitCounts(list []literalNode, maxBits int32) []int32 {
 		// We initialize the levels as if we had already figured this out.
 		levels[level] = levelInfo{
 			level:        level,
-			lastFreq:     list[1].freq,
-			nextCharFreq: list[2].freq,
-			nextPairFreq: list[0].freq + list[1].freq,
+			lastFreq:     int32(list[1].freq),
+			nextCharFreq: int32(list[2].freq),
+			nextPairFreq: int32(list[0].freq) + int32(list[1].freq),
 		}
 		leafCounts[level][level] = 2
 		if level == 1 {
@@ -194,7 +205,12 @@ func (h *huffmanEncoder) bitCounts(list []literalNode, maxBits int32) []int32 {
 			l.lastFreq = l.nextCharFreq
 			// Lower leafCounts are the same of the previous node.
 			leafCounts[level][level] = n
-			l.nextCharFreq = list[n].freq
+			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
@@ -270,12 +286,12 @@ func (h *huffmanEncoder) assignEncodingAndSize(bitCount []int32, list []literalN
 //
 // 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 []int32, maxBits int32) {
+func (h *huffmanEncoder) generate(freq []uint16, maxBits int32) {
 	if h.freqcache == nil {
 		// Allocate a reusable buffer with the longest possible frequency table.
-		// Possible lengths are codegenCodeCount, offsetCodeCount and maxNumLit.
-		// The largest of these is maxNumLit, so we allocate for that case.
-		h.freqcache = make([]literalNode, maxNumLit+1)
+		// Possible lengths are codegenCodeCount, offsetCodeCount and literalCount.
+		// The largest of these is literalCount, so we allocate for that case.
+		h.freqcache = make([]literalNode, literalCount+1)
 	}
 	list := h.freqcache[:len(freq)+1]
 	// Number of non-zero literals
@@ -342,3 +358,27 @@ func (s byFreq) Less(i, j int) bool {
 }
 
 func (s byFreq) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
+
+// histogramSize accumulates a histogram of b in h.
+// An estimated size in bits is returned.
+// Unassigned values are assigned '1' in the histogram.
+// len(h) must be >= 256, and h's elements must be all zeroes.
+func histogramSize(b []byte, h []uint16, fill bool) int {
+	h = h[:256]
+	for _, t := range b {
+		h[t]++
+	}
+	invTotal := 1.0 / float64(len(b))
+	shannon := 0.0
+	single := math.Ceil(-math.Log2(invTotal))
+	for i, v := range h[:] {
+		if v > 0 {
+			n := float64(v)
+			shannon += math.Ceil(-math.Log2(n*invTotal) * n)
+		} else if fill {
+			shannon += single
+			h[i] = 1
+		}
+	}
+	return int(shannon + 0.99)
+}