796 lines
27 KiB
Go
796 lines
27 KiB
Go
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package brotli
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import "math"
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type zopfliNode struct {
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length uint32
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distance uint32
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dcode_insert_length uint32
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u struct {
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cost float32
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next uint32
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shortcut uint32
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}
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}
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const maxEffectiveDistanceAlphabetSize = 544
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const kInfinity float32 = 1.7e38 /* ~= 2 ^ 127 */
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var kDistanceCacheIndex = []uint32{0, 1, 2, 3, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1}
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var kDistanceCacheOffset = []int{0, 0, 0, 0, -1, 1, -2, 2, -3, 3, -1, 1, -2, 2, -3, 3}
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func initZopfliNodes(array []zopfliNode, length uint) {
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var stub zopfliNode
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var i uint
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stub.length = 1
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stub.distance = 0
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stub.dcode_insert_length = 0
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stub.u.cost = kInfinity
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for i = 0; i < length; i++ {
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array[i] = stub
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}
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}
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func zopfliNodeCopyLength(self *zopfliNode) uint32 {
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return self.length & 0x1FFFFFF
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}
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func zopfliNodeLengthCode(self *zopfliNode) uint32 {
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var modifier uint32 = self.length >> 25
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return zopfliNodeCopyLength(self) + 9 - modifier
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}
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func zopfliNodeCopyDistance(self *zopfliNode) uint32 {
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return self.distance
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}
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func zopfliNodeDistanceCode(self *zopfliNode) uint32 {
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var short_code uint32 = self.dcode_insert_length >> 27
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if short_code == 0 {
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return zopfliNodeCopyDistance(self) + numDistanceShortCodes - 1
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} else {
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return short_code - 1
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}
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}
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func zopfliNodeCommandLength(self *zopfliNode) uint32 {
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return zopfliNodeCopyLength(self) + (self.dcode_insert_length & 0x7FFFFFF)
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}
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/* Histogram based cost model for zopflification. */
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type zopfliCostModel struct {
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cost_cmd_ [numCommandSymbols]float32
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cost_dist_ []float32
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distance_histogram_size uint32
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literal_costs_ []float32
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min_cost_cmd_ float32
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num_bytes_ uint
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}
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func initZopfliCostModel(self *zopfliCostModel, dist *distanceParams, num_bytes uint) {
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var distance_histogram_size uint32 = dist.alphabet_size
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if distance_histogram_size > maxEffectiveDistanceAlphabetSize {
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distance_histogram_size = maxEffectiveDistanceAlphabetSize
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}
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self.num_bytes_ = num_bytes
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self.literal_costs_ = make([]float32, (num_bytes + 2))
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self.cost_dist_ = make([]float32, (dist.alphabet_size))
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self.distance_histogram_size = distance_histogram_size
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}
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func cleanupZopfliCostModel(self *zopfliCostModel) {
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self.literal_costs_ = nil
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self.cost_dist_ = nil
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}
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func setCost(histogram []uint32, histogram_size uint, literal_histogram bool, cost []float32) {
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var sum uint = 0
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var missing_symbol_sum uint
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var log2sum float32
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var missing_symbol_cost float32
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var i uint
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for i = 0; i < histogram_size; i++ {
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sum += uint(histogram[i])
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}
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log2sum = float32(fastLog2(sum))
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missing_symbol_sum = sum
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if !literal_histogram {
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for i = 0; i < histogram_size; i++ {
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if histogram[i] == 0 {
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missing_symbol_sum++
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}
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}
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}
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missing_symbol_cost = float32(fastLog2(missing_symbol_sum)) + 2
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for i = 0; i < histogram_size; i++ {
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if histogram[i] == 0 {
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cost[i] = missing_symbol_cost
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continue
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}
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/* Shannon bits for this symbol. */
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cost[i] = log2sum - float32(fastLog2(uint(histogram[i])))
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/* Cannot be coded with less than 1 bit */
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if cost[i] < 1 {
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cost[i] = 1
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}
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}
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}
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func zopfliCostModelSetFromCommands(self *zopfliCostModel, position uint, ringbuffer []byte, ringbuffer_mask uint, commands []command, num_commands uint, last_insert_len uint) {
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var histogram_literal [numLiteralSymbols]uint32
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var histogram_cmd [numCommandSymbols]uint32
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var histogram_dist [maxEffectiveDistanceAlphabetSize]uint32
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var cost_literal [numLiteralSymbols]float32
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var pos uint = position - last_insert_len
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var min_cost_cmd float32 = kInfinity
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var i uint
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var cost_cmd []float32 = self.cost_cmd_[:]
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var literal_costs []float32
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histogram_literal = [numLiteralSymbols]uint32{}
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histogram_cmd = [numCommandSymbols]uint32{}
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histogram_dist = [maxEffectiveDistanceAlphabetSize]uint32{}
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for i = 0; i < num_commands; i++ {
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var inslength uint = uint(commands[i].insert_len_)
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var copylength uint = uint(commandCopyLen(&commands[i]))
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var distcode uint = uint(commands[i].dist_prefix_) & 0x3FF
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var cmdcode uint = uint(commands[i].cmd_prefix_)
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var j uint
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histogram_cmd[cmdcode]++
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if cmdcode >= 128 {
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histogram_dist[distcode]++
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}
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for j = 0; j < inslength; j++ {
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histogram_literal[ringbuffer[(pos+j)&ringbuffer_mask]]++
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}
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pos += inslength + copylength
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}
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setCost(histogram_literal[:], numLiteralSymbols, true, cost_literal[:])
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setCost(histogram_cmd[:], numCommandSymbols, false, cost_cmd)
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setCost(histogram_dist[:], uint(self.distance_histogram_size), false, self.cost_dist_)
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for i = 0; i < numCommandSymbols; i++ {
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min_cost_cmd = brotli_min_float(min_cost_cmd, cost_cmd[i])
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}
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self.min_cost_cmd_ = min_cost_cmd
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{
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literal_costs = self.literal_costs_
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var literal_carry float32 = 0.0
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var num_bytes uint = self.num_bytes_
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literal_costs[0] = 0.0
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for i = 0; i < num_bytes; i++ {
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literal_carry += cost_literal[ringbuffer[(position+i)&ringbuffer_mask]]
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literal_costs[i+1] = literal_costs[i] + literal_carry
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literal_carry -= literal_costs[i+1] - literal_costs[i]
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}
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}
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}
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func zopfliCostModelSetFromLiteralCosts(self *zopfliCostModel, position uint, ringbuffer []byte, ringbuffer_mask uint) {
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var literal_costs []float32 = self.literal_costs_
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var literal_carry float32 = 0.0
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var cost_dist []float32 = self.cost_dist_
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var cost_cmd []float32 = self.cost_cmd_[:]
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var num_bytes uint = self.num_bytes_
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var i uint
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estimateBitCostsForLiterals(position, num_bytes, ringbuffer_mask, ringbuffer, literal_costs[1:])
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literal_costs[0] = 0.0
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for i = 0; i < num_bytes; i++ {
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literal_carry += literal_costs[i+1]
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literal_costs[i+1] = literal_costs[i] + literal_carry
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literal_carry -= literal_costs[i+1] - literal_costs[i]
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}
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for i = 0; i < numCommandSymbols; i++ {
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cost_cmd[i] = float32(fastLog2(uint(11 + uint32(i))))
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}
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for i = 0; uint32(i) < self.distance_histogram_size; i++ {
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cost_dist[i] = float32(fastLog2(uint(20 + uint32(i))))
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}
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self.min_cost_cmd_ = float32(fastLog2(11))
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}
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func zopfliCostModelGetCommandCost(self *zopfliCostModel, cmdcode uint16) float32 {
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return self.cost_cmd_[cmdcode]
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}
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func zopfliCostModelGetDistanceCost(self *zopfliCostModel, distcode uint) float32 {
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return self.cost_dist_[distcode]
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}
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func zopfliCostModelGetLiteralCosts(self *zopfliCostModel, from uint, to uint) float32 {
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return self.literal_costs_[to] - self.literal_costs_[from]
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}
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func zopfliCostModelGetMinCostCmd(self *zopfliCostModel) float32 {
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return self.min_cost_cmd_
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}
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/* REQUIRES: len >= 2, start_pos <= pos */
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/* REQUIRES: cost < kInfinity, nodes[start_pos].cost < kInfinity */
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/* Maintains the "ZopfliNode array invariant". */
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func updateZopfliNode(nodes []zopfliNode, pos uint, start_pos uint, len uint, len_code uint, dist uint, short_code uint, cost float32) {
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var next *zopfliNode = &nodes[pos+len]
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next.length = uint32(len | (len+9-len_code)<<25)
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next.distance = uint32(dist)
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next.dcode_insert_length = uint32(short_code<<27 | (pos - start_pos))
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next.u.cost = cost
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}
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type posData struct {
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pos uint
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distance_cache [4]int
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costdiff float32
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cost float32
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}
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/* Maintains the smallest 8 cost difference together with their positions */
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type startPosQueue struct {
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q_ [8]posData
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idx_ uint
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}
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func initStartPosQueue(self *startPosQueue) {
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self.idx_ = 0
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}
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func startPosQueueSize(self *startPosQueue) uint {
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return brotli_min_size_t(self.idx_, 8)
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}
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func startPosQueuePush(self *startPosQueue, posdata *posData) {
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var offset uint = ^(self.idx_) & 7
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self.idx_++
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var len uint = startPosQueueSize(self)
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var i uint
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var q []posData = self.q_[:]
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q[offset] = *posdata
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/* Restore the sorted order. In the list of |len| items at most |len - 1|
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adjacent element comparisons / swaps are required. */
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for i = 1; i < len; i++ {
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if q[offset&7].costdiff > q[(offset+1)&7].costdiff {
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var tmp posData = q[offset&7]
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q[offset&7] = q[(offset+1)&7]
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q[(offset+1)&7] = tmp
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}
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offset++
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}
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}
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func startPosQueueAt(self *startPosQueue, k uint) *posData {
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return &self.q_[(k-self.idx_)&7]
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}
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/* Returns the minimum possible copy length that can improve the cost of any */
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/* future position. */
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func computeMinimumCopyLength(start_cost float32, nodes []zopfliNode, num_bytes uint, pos uint) uint {
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var min_cost float32 = start_cost
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var len uint = 2
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var next_len_bucket uint = 4
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/* Compute the minimum possible cost of reaching any future position. */
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var next_len_offset uint = 10
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for pos+len <= num_bytes && nodes[pos+len].u.cost <= min_cost {
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/* We already reached (pos + len) with no more cost than the minimum
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possible cost of reaching anything from this pos, so there is no point in
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looking for lengths <= len. */
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len++
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if len == next_len_offset {
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/* We reached the next copy length code bucket, so we add one more
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extra bit to the minimum cost. */
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min_cost += 1.0
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next_len_offset += next_len_bucket
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next_len_bucket *= 2
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}
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}
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return uint(len)
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}
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/* REQUIRES: nodes[pos].cost < kInfinity
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REQUIRES: nodes[0..pos] satisfies that "ZopfliNode array invariant". */
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func computeDistanceShortcut(block_start uint, pos uint, max_backward_limit uint, gap uint, nodes []zopfliNode) uint32 {
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var clen uint = uint(zopfliNodeCopyLength(&nodes[pos]))
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var ilen uint = uint(nodes[pos].dcode_insert_length & 0x7FFFFFF)
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var dist uint = uint(zopfliNodeCopyDistance(&nodes[pos]))
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/* Since |block_start + pos| is the end position of the command, the copy part
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starts from |block_start + pos - clen|. Distances that are greater than
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this or greater than |max_backward_limit| + |gap| are static dictionary
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references, and do not update the last distances.
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Also distance code 0 (last distance) does not update the last distances. */
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if pos == 0 {
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return 0
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} else if dist+clen <= block_start+pos+gap && dist <= max_backward_limit+gap && zopfliNodeDistanceCode(&nodes[pos]) > 0 {
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return uint32(pos)
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} else {
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return nodes[pos-clen-ilen].u.shortcut
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}
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}
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/* Fills in dist_cache[0..3] with the last four distances (as defined by
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Section 4. of the Spec) that would be used at (block_start + pos) if we
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used the shortest path of commands from block_start, computed from
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nodes[0..pos]. The last four distances at block_start are in
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starting_dist_cache[0..3].
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REQUIRES: nodes[pos].cost < kInfinity
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REQUIRES: nodes[0..pos] satisfies that "ZopfliNode array invariant". */
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func computeDistanceCache(pos uint, starting_dist_cache []int, nodes []zopfliNode, dist_cache []int) {
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var idx int = 0
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var p uint = uint(nodes[pos].u.shortcut)
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for idx < 4 && p > 0 {
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var ilen uint = uint(nodes[p].dcode_insert_length & 0x7FFFFFF)
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var clen uint = uint(zopfliNodeCopyLength(&nodes[p]))
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var dist uint = uint(zopfliNodeCopyDistance(&nodes[p]))
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dist_cache[idx] = int(dist)
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idx++
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/* Because of prerequisite, p >= clen + ilen >= 2. */
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p = uint(nodes[p-clen-ilen].u.shortcut)
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}
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for ; idx < 4; idx++ {
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dist_cache[idx] = starting_dist_cache[0]
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starting_dist_cache = starting_dist_cache[1:]
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
/* Maintains "ZopfliNode array invariant" and pushes node to the queue, if it
|
||
|
|
is eligible. */
|
||
|
|
func evaluateNode(block_start uint, pos uint, max_backward_limit uint, gap uint, starting_dist_cache []int, model *zopfliCostModel, queue *startPosQueue, nodes []zopfliNode) {
|
||
|
|
/* Save cost, because ComputeDistanceCache invalidates it. */
|
||
|
|
var node_cost float32 = nodes[pos].u.cost
|
||
|
|
nodes[pos].u.shortcut = computeDistanceShortcut(block_start, pos, max_backward_limit, gap, nodes)
|
||
|
|
if node_cost <= zopfliCostModelGetLiteralCosts(model, 0, pos) {
|
||
|
|
var posdata posData
|
||
|
|
posdata.pos = pos
|
||
|
|
posdata.cost = node_cost
|
||
|
|
posdata.costdiff = node_cost - zopfliCostModelGetLiteralCosts(model, 0, pos)
|
||
|
|
computeDistanceCache(pos, starting_dist_cache, nodes, posdata.distance_cache[:])
|
||
|
|
startPosQueuePush(queue, &posdata)
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
/* Returns longest copy length. */
|
||
|
|
func updateNodes(num_bytes uint, block_start uint, pos uint, ringbuffer []byte, ringbuffer_mask uint, params *encoderParams, max_backward_limit uint, starting_dist_cache []int, num_matches uint, matches []backwardMatch, model *zopfliCostModel, queue *startPosQueue, nodes []zopfliNode) uint {
|
||
|
|
var cur_ix uint = block_start + pos
|
||
|
|
var cur_ix_masked uint = cur_ix & ringbuffer_mask
|
||
|
|
var max_distance uint = brotli_min_size_t(cur_ix, max_backward_limit)
|
||
|
|
var max_len uint = num_bytes - pos
|
||
|
|
var max_zopfli_len uint = maxZopfliLen(params)
|
||
|
|
var max_iters uint = maxZopfliCandidates(params)
|
||
|
|
var min_len uint
|
||
|
|
var result uint = 0
|
||
|
|
var k uint
|
||
|
|
var gap uint = 0
|
||
|
|
|
||
|
|
evaluateNode(block_start, pos, max_backward_limit, gap, starting_dist_cache, model, queue, nodes)
|
||
|
|
{
|
||
|
|
var posdata *posData = startPosQueueAt(queue, 0)
|
||
|
|
var min_cost float32 = (posdata.cost + zopfliCostModelGetMinCostCmd(model) + zopfliCostModelGetLiteralCosts(model, posdata.pos, pos))
|
||
|
|
min_len = computeMinimumCopyLength(min_cost, nodes, num_bytes, pos)
|
||
|
|
}
|
||
|
|
|
||
|
|
/* Go over the command starting positions in order of increasing cost
|
||
|
|
difference. */
|
||
|
|
for k = 0; k < max_iters && k < startPosQueueSize(queue); k++ {
|
||
|
|
var posdata *posData = startPosQueueAt(queue, k)
|
||
|
|
var start uint = posdata.pos
|
||
|
|
var inscode uint16 = getInsertLengthCode(pos - start)
|
||
|
|
var start_costdiff float32 = posdata.costdiff
|
||
|
|
var base_cost float32 = start_costdiff + float32(getInsertExtra(inscode)) + zopfliCostModelGetLiteralCosts(model, 0, pos)
|
||
|
|
var best_len uint = min_len - 1
|
||
|
|
var j uint = 0
|
||
|
|
/* Look for last distance matches using the distance cache from this
|
||
|
|
starting position. */
|
||
|
|
for ; j < numDistanceShortCodes && best_len < max_len; j++ {
|
||
|
|
var idx uint = uint(kDistanceCacheIndex[j])
|
||
|
|
var backward uint = uint(posdata.distance_cache[idx] + kDistanceCacheOffset[j])
|
||
|
|
var prev_ix uint = cur_ix - backward
|
||
|
|
var len uint = 0
|
||
|
|
var continuation byte = ringbuffer[cur_ix_masked+best_len]
|
||
|
|
if cur_ix_masked+best_len > ringbuffer_mask {
|
||
|
|
break
|
||
|
|
}
|
||
|
|
|
||
|
|
if backward > max_distance+gap {
|
||
|
|
/* Word dictionary -> ignore. */
|
||
|
|
continue
|
||
|
|
}
|
||
|
|
|
||
|
|
if backward <= max_distance {
|
||
|
|
/* Regular backward reference. */
|
||
|
|
if prev_ix >= cur_ix {
|
||
|
|
continue
|
||
|
|
}
|
||
|
|
|
||
|
|
prev_ix &= ringbuffer_mask
|
||
|
|
if prev_ix+best_len > ringbuffer_mask || continuation != ringbuffer[prev_ix+best_len] {
|
||
|
|
continue
|
||
|
|
}
|
||
|
|
|
||
|
|
len = findMatchLengthWithLimit(ringbuffer[prev_ix:], ringbuffer[cur_ix_masked:], max_len)
|
||
|
|
} else {
|
||
|
|
continue
|
||
|
|
}
|
||
|
|
{
|
||
|
|
var dist_cost float32 = base_cost + zopfliCostModelGetDistanceCost(model, j)
|
||
|
|
var l uint
|
||
|
|
for l = best_len + 1; l <= len; l++ {
|
||
|
|
var copycode uint16 = getCopyLengthCode(l)
|
||
|
|
var cmdcode uint16 = combineLengthCodes(inscode, copycode, j == 0)
|
||
|
|
var tmp float32
|
||
|
|
if cmdcode < 128 {
|
||
|
|
tmp = base_cost
|
||
|
|
} else {
|
||
|
|
tmp = dist_cost
|
||
|
|
}
|
||
|
|
var cost float32 = tmp + float32(getCopyExtra(copycode)) + zopfliCostModelGetCommandCost(model, cmdcode)
|
||
|
|
if cost < nodes[pos+l].u.cost {
|
||
|
|
updateZopfliNode(nodes, pos, start, l, l, backward, j+1, cost)
|
||
|
|
result = brotli_max_size_t(result, l)
|
||
|
|
}
|
||
|
|
|
||
|
|
best_len = l
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
/* At higher iterations look only for new last distance matches, since
|
||
|
|
looking only for new command start positions with the same distances
|
||
|
|
does not help much. */
|
||
|
|
if k >= 2 {
|
||
|
|
continue
|
||
|
|
}
|
||
|
|
{
|
||
|
|
/* Loop through all possible copy lengths at this position. */
|
||
|
|
var len uint = min_len
|
||
|
|
for j = 0; j < num_matches; j++ {
|
||
|
|
var match backwardMatch = matches[j]
|
||
|
|
var dist uint = uint(match.distance)
|
||
|
|
var is_dictionary_match bool = (dist > max_distance+gap)
|
||
|
|
var dist_code uint = dist + numDistanceShortCodes - 1
|
||
|
|
var dist_symbol uint16
|
||
|
|
var distextra uint32
|
||
|
|
var distnumextra uint32
|
||
|
|
var dist_cost float32
|
||
|
|
var max_match_len uint
|
||
|
|
/* We already tried all possible last distance matches, so we can use
|
||
|
|
normal distance code here. */
|
||
|
|
prefixEncodeCopyDistance(dist_code, uint(params.dist.num_direct_distance_codes), uint(params.dist.distance_postfix_bits), &dist_symbol, &distextra)
|
||
|
|
|
||
|
|
distnumextra = uint32(dist_symbol) >> 10
|
||
|
|
dist_cost = base_cost + float32(distnumextra) + zopfliCostModelGetDistanceCost(model, uint(dist_symbol)&0x3FF)
|
||
|
|
|
||
|
|
/* Try all copy lengths up until the maximum copy length corresponding
|
||
|
|
to this distance. If the distance refers to the static dictionary, or
|
||
|
|
the maximum length is long enough, try only one maximum length. */
|
||
|
|
max_match_len = backwardMatchLength(&match)
|
||
|
|
|
||
|
|
if len < max_match_len && (is_dictionary_match || max_match_len > max_zopfli_len) {
|
||
|
|
len = max_match_len
|
||
|
|
}
|
||
|
|
|
||
|
|
for ; len <= max_match_len; len++ {
|
||
|
|
var len_code uint
|
||
|
|
if is_dictionary_match {
|
||
|
|
len_code = backwardMatchLengthCode(&match)
|
||
|
|
} else {
|
||
|
|
len_code = len
|
||
|
|
}
|
||
|
|
var copycode uint16 = getCopyLengthCode(len_code)
|
||
|
|
var cmdcode uint16 = combineLengthCodes(inscode, copycode, false)
|
||
|
|
var cost float32 = dist_cost + float32(getCopyExtra(copycode)) + zopfliCostModelGetCommandCost(model, cmdcode)
|
||
|
|
if cost < nodes[pos+len].u.cost {
|
||
|
|
updateZopfliNode(nodes, pos, start, uint(len), len_code, dist, 0, cost)
|
||
|
|
result = brotli_max_size_t(result, uint(len))
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
return result
|
||
|
|
}
|
||
|
|
|
||
|
|
func computeShortestPathFromNodes(num_bytes uint, nodes []zopfliNode) uint {
|
||
|
|
var index uint = num_bytes
|
||
|
|
var num_commands uint = 0
|
||
|
|
for nodes[index].dcode_insert_length&0x7FFFFFF == 0 && nodes[index].length == 1 {
|
||
|
|
index--
|
||
|
|
}
|
||
|
|
nodes[index].u.next = math.MaxUint32
|
||
|
|
for index != 0 {
|
||
|
|
var len uint = uint(zopfliNodeCommandLength(&nodes[index]))
|
||
|
|
index -= uint(len)
|
||
|
|
nodes[index].u.next = uint32(len)
|
||
|
|
num_commands++
|
||
|
|
}
|
||
|
|
|
||
|
|
return num_commands
|
||
|
|
}
|
||
|
|
|
||
|
|
/* REQUIRES: nodes != NULL and len(nodes) >= num_bytes + 1 */
|
||
|
|
func zopfliCreateCommands(num_bytes uint, block_start uint, nodes []zopfliNode, dist_cache []int, last_insert_len *uint, params *encoderParams, commands []command, num_literals *uint) {
|
||
|
|
var max_backward_limit uint = maxBackwardLimit(params.lgwin)
|
||
|
|
var pos uint = 0
|
||
|
|
var offset uint32 = nodes[0].u.next
|
||
|
|
var i uint
|
||
|
|
var gap uint = 0
|
||
|
|
for i = 0; offset != math.MaxUint32; i++ {
|
||
|
|
var next *zopfliNode = &nodes[uint32(pos)+offset]
|
||
|
|
var copy_length uint = uint(zopfliNodeCopyLength(next))
|
||
|
|
var insert_length uint = uint(next.dcode_insert_length & 0x7FFFFFF)
|
||
|
|
pos += insert_length
|
||
|
|
offset = next.u.next
|
||
|
|
if i == 0 {
|
||
|
|
insert_length += *last_insert_len
|
||
|
|
*last_insert_len = 0
|
||
|
|
}
|
||
|
|
{
|
||
|
|
var distance uint = uint(zopfliNodeCopyDistance(next))
|
||
|
|
var len_code uint = uint(zopfliNodeLengthCode(next))
|
||
|
|
var max_distance uint = brotli_min_size_t(block_start+pos, max_backward_limit)
|
||
|
|
var is_dictionary bool = (distance > max_distance+gap)
|
||
|
|
var dist_code uint = uint(zopfliNodeDistanceCode(next))
|
||
|
|
initCommand(&commands[i], ¶ms.dist, insert_length, copy_length, int(len_code)-int(copy_length), dist_code)
|
||
|
|
|
||
|
|
if !is_dictionary && dist_code > 0 {
|
||
|
|
dist_cache[3] = dist_cache[2]
|
||
|
|
dist_cache[2] = dist_cache[1]
|
||
|
|
dist_cache[1] = dist_cache[0]
|
||
|
|
dist_cache[0] = int(distance)
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
*num_literals += insert_length
|
||
|
|
pos += copy_length
|
||
|
|
}
|
||
|
|
|
||
|
|
*last_insert_len += num_bytes - pos
|
||
|
|
}
|
||
|
|
|
||
|
|
func zopfliIterate(num_bytes uint, position uint, ringbuffer []byte, ringbuffer_mask uint, params *encoderParams, gap uint, dist_cache []int, model *zopfliCostModel, num_matches []uint32, matches []backwardMatch, nodes []zopfliNode) uint {
|
||
|
|
var max_backward_limit uint = maxBackwardLimit(params.lgwin)
|
||
|
|
var max_zopfli_len uint = maxZopfliLen(params)
|
||
|
|
var queue startPosQueue
|
||
|
|
var cur_match_pos uint = 0
|
||
|
|
var i uint
|
||
|
|
nodes[0].length = 0
|
||
|
|
nodes[0].u.cost = 0
|
||
|
|
initStartPosQueue(&queue)
|
||
|
|
for i = 0; i+3 < num_bytes; i++ {
|
||
|
|
var skip uint = updateNodes(num_bytes, position, i, ringbuffer, ringbuffer_mask, params, max_backward_limit, dist_cache, uint(num_matches[i]), matches[cur_match_pos:], model, &queue, nodes)
|
||
|
|
if skip < longCopyQuickStep {
|
||
|
|
skip = 0
|
||
|
|
}
|
||
|
|
cur_match_pos += uint(num_matches[i])
|
||
|
|
if num_matches[i] == 1 && backwardMatchLength(&matches[cur_match_pos-1]) > max_zopfli_len {
|
||
|
|
skip = brotli_max_size_t(backwardMatchLength(&matches[cur_match_pos-1]), skip)
|
||
|
|
}
|
||
|
|
|
||
|
|
if skip > 1 {
|
||
|
|
skip--
|
||
|
|
for skip != 0 {
|
||
|
|
i++
|
||
|
|
if i+3 >= num_bytes {
|
||
|
|
break
|
||
|
|
}
|
||
|
|
evaluateNode(position, i, max_backward_limit, gap, dist_cache, model, &queue, nodes)
|
||
|
|
cur_match_pos += uint(num_matches[i])
|
||
|
|
skip--
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
return computeShortestPathFromNodes(num_bytes, nodes)
|
||
|
|
}
|
||
|
|
|
||
|
|
/* Computes the shortest path of commands from position to at most
|
||
|
|
position + num_bytes.
|
||
|
|
|
||
|
|
On return, path->size() is the number of commands found and path[i] is the
|
||
|
|
length of the i-th command (copy length plus insert length).
|
||
|
|
Note that the sum of the lengths of all commands can be less than num_bytes.
|
||
|
|
|
||
|
|
On return, the nodes[0..num_bytes] array will have the following
|
||
|
|
"ZopfliNode array invariant":
|
||
|
|
For each i in [1..num_bytes], if nodes[i].cost < kInfinity, then
|
||
|
|
(1) nodes[i].copy_length() >= 2
|
||
|
|
(2) nodes[i].command_length() <= i and
|
||
|
|
(3) nodes[i - nodes[i].command_length()].cost < kInfinity
|
||
|
|
|
||
|
|
REQUIRES: nodes != nil and len(nodes) >= num_bytes + 1 */
|
||
|
|
func zopfliComputeShortestPath(num_bytes uint, position uint, ringbuffer []byte, ringbuffer_mask uint, params *encoderParams, dist_cache []int, hasher *h10, nodes []zopfliNode) uint {
|
||
|
|
var max_backward_limit uint = maxBackwardLimit(params.lgwin)
|
||
|
|
var max_zopfli_len uint = maxZopfliLen(params)
|
||
|
|
var model zopfliCostModel
|
||
|
|
var queue startPosQueue
|
||
|
|
var matches [2 * (maxNumMatchesH10 + 64)]backwardMatch
|
||
|
|
var store_end uint
|
||
|
|
if num_bytes >= hasher.StoreLookahead() {
|
||
|
|
store_end = position + num_bytes - hasher.StoreLookahead() + 1
|
||
|
|
} else {
|
||
|
|
store_end = position
|
||
|
|
}
|
||
|
|
var i uint
|
||
|
|
var gap uint = 0
|
||
|
|
var lz_matches_offset uint = 0
|
||
|
|
nodes[0].length = 0
|
||
|
|
nodes[0].u.cost = 0
|
||
|
|
initZopfliCostModel(&model, ¶ms.dist, num_bytes)
|
||
|
|
zopfliCostModelSetFromLiteralCosts(&model, position, ringbuffer, ringbuffer_mask)
|
||
|
|
initStartPosQueue(&queue)
|
||
|
|
for i = 0; i+hasher.HashTypeLength()-1 < num_bytes; i++ {
|
||
|
|
var pos uint = position + i
|
||
|
|
var max_distance uint = brotli_min_size_t(pos, max_backward_limit)
|
||
|
|
var skip uint
|
||
|
|
var num_matches uint
|
||
|
|
num_matches = findAllMatchesH10(hasher, ¶ms.dictionary, ringbuffer, ringbuffer_mask, pos, num_bytes-i, max_distance, gap, params, matches[lz_matches_offset:])
|
||
|
|
if num_matches > 0 && backwardMatchLength(&matches[num_matches-1]) > max_zopfli_len {
|
||
|
|
matches[0] = matches[num_matches-1]
|
||
|
|
num_matches = 1
|
||
|
|
}
|
||
|
|
|
||
|
|
skip = updateNodes(num_bytes, position, i, ringbuffer, ringbuffer_mask, params, max_backward_limit, dist_cache, num_matches, matches[:], &model, &queue, nodes)
|
||
|
|
if skip < longCopyQuickStep {
|
||
|
|
skip = 0
|
||
|
|
}
|
||
|
|
if num_matches == 1 && backwardMatchLength(&matches[0]) > max_zopfli_len {
|
||
|
|
skip = brotli_max_size_t(backwardMatchLength(&matches[0]), skip)
|
||
|
|
}
|
||
|
|
|
||
|
|
if skip > 1 {
|
||
|
|
/* Add the tail of the copy to the hasher. */
|
||
|
|
hasher.StoreRange(ringbuffer, ringbuffer_mask, pos+1, brotli_min_size_t(pos+skip, store_end))
|
||
|
|
|
||
|
|
skip--
|
||
|
|
for skip != 0 {
|
||
|
|
i++
|
||
|
|
if i+hasher.HashTypeLength()-1 >= num_bytes {
|
||
|
|
break
|
||
|
|
}
|
||
|
|
evaluateNode(position, i, max_backward_limit, gap, dist_cache, &model, &queue, nodes)
|
||
|
|
skip--
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
cleanupZopfliCostModel(&model)
|
||
|
|
return computeShortestPathFromNodes(num_bytes, nodes)
|
||
|
|
}
|
||
|
|
|
||
|
|
func createZopfliBackwardReferences(num_bytes uint, position uint, ringbuffer []byte, ringbuffer_mask uint, params *encoderParams, hasher *h10, dist_cache []int, last_insert_len *uint, commands []command, num_commands *uint, num_literals *uint) {
|
||
|
|
var nodes []zopfliNode
|
||
|
|
nodes = make([]zopfliNode, (num_bytes + 1))
|
||
|
|
initZopfliNodes(nodes, num_bytes+1)
|
||
|
|
*num_commands += zopfliComputeShortestPath(num_bytes, position, ringbuffer, ringbuffer_mask, params, dist_cache, hasher, nodes)
|
||
|
|
zopfliCreateCommands(num_bytes, position, nodes, dist_cache, last_insert_len, params, commands, num_literals)
|
||
|
|
nodes = nil
|
||
|
|
}
|
||
|
|
|
||
|
|
func createHqZopfliBackwardReferences(num_bytes uint, position uint, ringbuffer []byte, ringbuffer_mask uint, params *encoderParams, hasher hasherHandle, dist_cache []int, last_insert_len *uint, commands []command, num_commands *uint, num_literals *uint) {
|
||
|
|
var max_backward_limit uint = maxBackwardLimit(params.lgwin)
|
||
|
|
var num_matches []uint32 = make([]uint32, num_bytes)
|
||
|
|
var matches_size uint = 4 * num_bytes
|
||
|
|
var store_end uint
|
||
|
|
if num_bytes >= hasher.StoreLookahead() {
|
||
|
|
store_end = position + num_bytes - hasher.StoreLookahead() + 1
|
||
|
|
} else {
|
||
|
|
store_end = position
|
||
|
|
}
|
||
|
|
var cur_match_pos uint = 0
|
||
|
|
var i uint
|
||
|
|
var orig_num_literals uint
|
||
|
|
var orig_last_insert_len uint
|
||
|
|
var orig_dist_cache [4]int
|
||
|
|
var orig_num_commands uint
|
||
|
|
var model zopfliCostModel
|
||
|
|
var nodes []zopfliNode
|
||
|
|
var matches []backwardMatch = make([]backwardMatch, matches_size)
|
||
|
|
var gap uint = 0
|
||
|
|
var shadow_matches uint = 0
|
||
|
|
var new_array []backwardMatch
|
||
|
|
for i = 0; i+hasher.HashTypeLength()-1 < num_bytes; i++ {
|
||
|
|
var pos uint = position + i
|
||
|
|
var max_distance uint = brotli_min_size_t(pos, max_backward_limit)
|
||
|
|
var max_length uint = num_bytes - i
|
||
|
|
var num_found_matches uint
|
||
|
|
var cur_match_end uint
|
||
|
|
var j uint
|
||
|
|
|
||
|
|
/* Ensure that we have enough free slots. */
|
||
|
|
if matches_size < cur_match_pos+maxNumMatchesH10+shadow_matches {
|
||
|
|
var new_size uint = matches_size
|
||
|
|
if new_size == 0 {
|
||
|
|
new_size = cur_match_pos + maxNumMatchesH10 + shadow_matches
|
||
|
|
}
|
||
|
|
|
||
|
|
for new_size < cur_match_pos+maxNumMatchesH10+shadow_matches {
|
||
|
|
new_size *= 2
|
||
|
|
}
|
||
|
|
|
||
|
|
new_array = make([]backwardMatch, new_size)
|
||
|
|
if matches_size != 0 {
|
||
|
|
copy(new_array, matches[:matches_size])
|
||
|
|
}
|
||
|
|
|
||
|
|
matches = new_array
|
||
|
|
matches_size = new_size
|
||
|
|
}
|
||
|
|
|
||
|
|
num_found_matches = findAllMatchesH10(hasher.(*h10), ¶ms.dictionary, ringbuffer, ringbuffer_mask, pos, max_length, max_distance, gap, params, matches[cur_match_pos+shadow_matches:])
|
||
|
|
cur_match_end = cur_match_pos + num_found_matches
|
||
|
|
for j = cur_match_pos; j+1 < cur_match_end; j++ {
|
||
|
|
assert(backwardMatchLength(&matches[j]) <= backwardMatchLength(&matches[j+1]))
|
||
|
|
}
|
||
|
|
|
||
|
|
num_matches[i] = uint32(num_found_matches)
|
||
|
|
if num_found_matches > 0 {
|
||
|
|
var match_len uint = backwardMatchLength(&matches[cur_match_end-1])
|
||
|
|
if match_len > maxZopfliLenQuality11 {
|
||
|
|
var skip uint = match_len - 1
|
||
|
|
matches[cur_match_pos] = matches[cur_match_end-1]
|
||
|
|
cur_match_pos++
|
||
|
|
num_matches[i] = 1
|
||
|
|
|
||
|
|
/* Add the tail of the copy to the hasher. */
|
||
|
|
hasher.StoreRange(ringbuffer, ringbuffer_mask, pos+1, brotli_min_size_t(pos+match_len, store_end))
|
||
|
|
var pos uint = i
|
||
|
|
for i := 0; i < int(skip); i++ {
|
||
|
|
num_matches[pos+1:][i] = 0
|
||
|
|
}
|
||
|
|
i += skip
|
||
|
|
} else {
|
||
|
|
cur_match_pos = cur_match_end
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
orig_num_literals = *num_literals
|
||
|
|
orig_last_insert_len = *last_insert_len
|
||
|
|
copy(orig_dist_cache[:], dist_cache[:4])
|
||
|
|
orig_num_commands = *num_commands
|
||
|
|
nodes = make([]zopfliNode, (num_bytes + 1))
|
||
|
|
initZopfliCostModel(&model, ¶ms.dist, num_bytes)
|
||
|
|
for i = 0; i < 2; i++ {
|
||
|
|
initZopfliNodes(nodes, num_bytes+1)
|
||
|
|
if i == 0 {
|
||
|
|
zopfliCostModelSetFromLiteralCosts(&model, position, ringbuffer, ringbuffer_mask)
|
||
|
|
} else {
|
||
|
|
zopfliCostModelSetFromCommands(&model, position, ringbuffer, ringbuffer_mask, commands, *num_commands-orig_num_commands, orig_last_insert_len)
|
||
|
|
}
|
||
|
|
|
||
|
|
*num_commands = orig_num_commands
|
||
|
|
*num_literals = orig_num_literals
|
||
|
|
*last_insert_len = orig_last_insert_len
|
||
|
|
copy(dist_cache, orig_dist_cache[:4])
|
||
|
|
*num_commands += zopfliIterate(num_bytes, position, ringbuffer, ringbuffer_mask, params, gap, dist_cache, &model, num_matches, matches, nodes)
|
||
|
|
zopfliCreateCommands(num_bytes, position, nodes, dist_cache, last_insert_len, params, commands, num_literals)
|
||
|
|
}
|
||
|
|
|
||
|
|
cleanupZopfliCostModel(&model)
|
||
|
|
nodes = nil
|
||
|
|
matches = nil
|
||
|
|
num_matches = nil
|
||
|
|
}
|