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// Copyright 2010 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 compress
func (coder Coder8) MoveToFrontCoder() Coder16 {
symbols := make(chan []uint16, BUFFER_CHAN_SIZE)
go func() {
nodes, buffer := [256]byte{}, [BUFFER_POOL_SIZE]uint16{}
var first byte
for node, _ := range nodes {
nodes[node] = uint8(node) + 1
}
current, offset, index := buffer[0:BUFFER_SIZE], BUFFER_SIZE, 0
for block := range coder.Input {
for _, v := range block {
var node, next byte
var symbol uint16
for next = first; next != v; node, next = next, nodes[next] {
symbol++
}
current[index], index = symbol, index + 1
if symbol != 0 {
first, nodes[node], nodes[next] = next, nodes[next], first
}
if index == BUFFER_SIZE {
symbols <- current
next := offset + BUFFER_SIZE
current, offset, index = buffer[offset:next], next & BUFFER_POOL_SIZE_MASK, 0
}
}
}
symbols <- current[:index]
close(symbols)
}()
return Coder16{Alphabit:256, Input:symbols}
}
func (coder Coder8) MoveToFrontDecoder() Coder16 {
nodes := [256]byte{}
var first byte
for node, _ := range nodes {
nodes[node] = uint8(node) + 1
}
output := func(symbol uint16) bool {
var node, next byte
moveToFront := symbol != 0
for next = first; symbol > 0; node, next = next, nodes[next] {
symbol--
}
if moveToFront {
first, nodes[node], nodes[next] = next, nodes[next], first
}
return coder.Output(next)
}
return Coder16{Alphabit:256, Output:output}
}
func (coder Coder8) MoveToFrontRunLengthCoder() Coder16 {
symbols := make(chan []uint16, BUFFER_CHAN_SIZE)
go func() {
var buffer [BUFFER_POOL_SIZE]uint16
current, offset, index, length := buffer[0:BUFFER_SIZE], BUFFER_SIZE, 0, uint64(0)
outputSymbol := func(symbol uint16) {
current[index], index = symbol, index + 1
if index == BUFFER_SIZE {
symbols <- current
next := offset + BUFFER_SIZE
current, offset, index = buffer[offset:next], next & BUFFER_POOL_SIZE_MASK, 0
}
}
outputLength := func() {
if length > 0 {
length--
outputSymbol(uint16(length & 1))
for length > 1 {
length = (length - 2) >> 1
outputSymbol(uint16(length & 1))
}
length = 0
}
}
var nodes [256]byte
var first byte
for node, _ := range nodes {
nodes[node] = byte(node) + 1
}
for block := range coder.Input {
for _, v := range block {
var node, next byte
var symbol uint16
for next = first; next != v; node, next = next, nodes[next] {
symbol++
}
if symbol == 0 {
length++
continue
}
first, nodes[node], nodes[next] = next, nodes[next], first
outputLength()
outputSymbol(symbol + 1)
}
}
outputLength()
symbols <- current[:index]
close(symbols)
}()
return Coder16{Alphabit:257, Input:symbols}
}
func (coder Coder8) MoveToFrontRunLengthDecoder() Coder16 {
var nodes [256]byte
var first byte
for node, _ := range nodes {
nodes[node] = uint8(node) + 1
}
length := uint64(1)
output := func(symbol uint16) bool {
if symbol > 1 {
var node, next byte
symbol, length = symbol - 1, 1
for next = first; symbol > 0; node, next = next, nodes[next] {
symbol--
}
first, nodes[node], nodes[next] = next, nodes[next], first
return coder.Output(next)
}
for c := length << symbol; c > 0; c-- {
if coder.Output(first) {
return true
}
}
length <<= 1
return false
}
return Coder16{Alphabit:257, Output:output}
}
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