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histogram.go
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histogram.go
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package brotli
import "math"
/* The distance symbols effectively used by "Large Window Brotli" (32-bit). */
const numHistogramDistanceSymbols = 544
type histogramLiteral struct {
data_ [numLiteralSymbols]uint32
total_count_ uint
bit_cost_ float64
}
func histogramClearLiteral(self *histogramLiteral) {
self.data_ = [numLiteralSymbols]uint32{}
self.total_count_ = 0
self.bit_cost_ = math.MaxFloat64
}
func clearHistogramsLiteral(array []histogramLiteral, length uint) {
var i uint
for i = 0; i < length; i++ {
histogramClearLiteral(&array[i:][0])
}
}
func histogramAddLiteral(self *histogramLiteral, val uint) {
self.data_[val]++
self.total_count_++
}
func histogramAddVectorLiteral(self *histogramLiteral, p []byte, n uint) {
self.total_count_ += n
n += 1
for {
n--
if n == 0 {
break
}
self.data_[p[0]]++
p = p[1:]
}
}
func histogramAddHistogramLiteral(self *histogramLiteral, v *histogramLiteral) {
var i uint
self.total_count_ += v.total_count_
for i = 0; i < numLiteralSymbols; i++ {
self.data_[i] += v.data_[i]
}
}
func histogramDataSizeLiteral() uint {
return numLiteralSymbols
}
type histogramCommand struct {
data_ [numCommandSymbols]uint32
total_count_ uint
bit_cost_ float64
}
func histogramClearCommand(self *histogramCommand) {
self.data_ = [numCommandSymbols]uint32{}
self.total_count_ = 0
self.bit_cost_ = math.MaxFloat64
}
func clearHistogramsCommand(array []histogramCommand, length uint) {
var i uint
for i = 0; i < length; i++ {
histogramClearCommand(&array[i:][0])
}
}
func histogramAddCommand(self *histogramCommand, val uint) {
self.data_[val]++
self.total_count_++
}
func histogramAddVectorCommand(self *histogramCommand, p []uint16, n uint) {
self.total_count_ += n
n += 1
for {
n--
if n == 0 {
break
}
self.data_[p[0]]++
p = p[1:]
}
}
func histogramAddHistogramCommand(self *histogramCommand, v *histogramCommand) {
var i uint
self.total_count_ += v.total_count_
for i = 0; i < numCommandSymbols; i++ {
self.data_[i] += v.data_[i]
}
}
func histogramDataSizeCommand() uint {
return numCommandSymbols
}
type histogramDistance struct {
data_ [numDistanceSymbols]uint32
total_count_ uint
bit_cost_ float64
}
func histogramClearDistance(self *histogramDistance) {
self.data_ = [numDistanceSymbols]uint32{}
self.total_count_ = 0
self.bit_cost_ = math.MaxFloat64
}
func clearHistogramsDistance(array []histogramDistance, length uint) {
var i uint
for i = 0; i < length; i++ {
histogramClearDistance(&array[i:][0])
}
}
func histogramAddDistance(self *histogramDistance, val uint) {
self.data_[val]++
self.total_count_++
}
func histogramAddVectorDistance(self *histogramDistance, p []uint16, n uint) {
self.total_count_ += n
n += 1
for {
n--
if n == 0 {
break
}
self.data_[p[0]]++
p = p[1:]
}
}
func histogramAddHistogramDistance(self *histogramDistance, v *histogramDistance) {
var i uint
self.total_count_ += v.total_count_
for i = 0; i < numDistanceSymbols; i++ {
self.data_[i] += v.data_[i]
}
}
func histogramDataSizeDistance() uint {
return numDistanceSymbols
}
type blockSplitIterator struct {
split_ *blockSplit
idx_ uint
type_ uint
length_ uint
}
func initBlockSplitIterator(self *blockSplitIterator, split *blockSplit) {
self.split_ = split
self.idx_ = 0
self.type_ = 0
if len(split.lengths) > 0 {
self.length_ = uint(split.lengths[0])
} else {
self.length_ = 0
}
}
func blockSplitIteratorNext(self *blockSplitIterator) {
if self.length_ == 0 {
self.idx_++
self.type_ = uint(self.split_.types[self.idx_])
self.length_ = uint(self.split_.lengths[self.idx_])
}
self.length_--
}
func buildHistogramsWithContext(cmds []command, literal_split *blockSplit, insert_and_copy_split *blockSplit, dist_split *blockSplit, ringbuffer []byte, start_pos uint, mask uint, prev_byte byte, prev_byte2 byte, context_modes []int, literal_histograms []histogramLiteral, insert_and_copy_histograms []histogramCommand, copy_dist_histograms []histogramDistance) {
var pos uint = start_pos
var literal_it blockSplitIterator
var insert_and_copy_it blockSplitIterator
var dist_it blockSplitIterator
initBlockSplitIterator(&literal_it, literal_split)
initBlockSplitIterator(&insert_and_copy_it, insert_and_copy_split)
initBlockSplitIterator(&dist_it, dist_split)
for i := range cmds {
var cmd *command = &cmds[i]
var j uint
blockSplitIteratorNext(&insert_and_copy_it)
histogramAddCommand(&insert_and_copy_histograms[insert_and_copy_it.type_], uint(cmd.cmd_prefix_))
/* TODO: unwrap iterator blocks. */
for j = uint(cmd.insert_len_); j != 0; j-- {
var context uint
blockSplitIteratorNext(&literal_it)
context = literal_it.type_
if context_modes != nil {
var lut contextLUT = getContextLUT(context_modes[context])
context = (context << literalContextBits) + uint(getContext(prev_byte, prev_byte2, lut))
}
histogramAddLiteral(&literal_histograms[context], uint(ringbuffer[pos&mask]))
prev_byte2 = prev_byte
prev_byte = ringbuffer[pos&mask]
pos++
}
pos += uint(commandCopyLen(cmd))
if commandCopyLen(cmd) != 0 {
prev_byte2 = ringbuffer[(pos-2)&mask]
prev_byte = ringbuffer[(pos-1)&mask]
if cmd.cmd_prefix_ >= 128 {
var context uint
blockSplitIteratorNext(&dist_it)
context = uint(uint32(dist_it.type_<<distanceContextBits) + commandDistanceContext(cmd))
histogramAddDistance(©_dist_histograms[context], uint(cmd.dist_prefix_)&0x3FF)
}
}
}
}