/usr/share/gocode/src/github.com/pointlander/compress/burrows_wheeler.go is in golang-github-pointlander-compress-dev 1.0.0-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 | // 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
import "sort"
type rotation struct {
int
s []uint8
}
type Rotations []rotation
func (r Rotations) Len() int {
return len(r)
}
func less(a, b rotation) bool {
la, lb, ia, ib := len(a.s), len(b.s), a.int, b.int
for {
if x, y := a.s[ia], b.s[ib]; x != y {
return x < y
}
ia, ib = ia + 1, ib + 1
if ia == la {
ia = 0
}
if ib == lb {
ib = 0
}
if ia == a.int && ib == b.int {
break
}
}
return false
}
func (r Rotations) Less(i, j int) bool {
return less(r[i], r[j])
}
func (r Rotations) Swap(i, j int) {
r[i], r[j] = r[j], r[i]
}
func merge(left, right, out Rotations) {
for len(left) > 0 && len(right) > 0 {
if less(left[0], right[0]) {
out[0], left = left[0], left[1:]
} else {
out[0], right = right[0], right[1:]
}
out = out[1:]
}
copy(out, left)
copy(out, right)
}
func psort(in Rotations, s chan<- bool) {
if len(in) < 1024 {
sort.Sort(in)
s <- true
return
}
l, r, split := make(chan bool), make(chan bool), len(in) / 2
left, right := in[:split], in[split:]
go psort(left, l)
go psort(right, r)
_, _ = <-l, <-r
out := make(Rotations, len(in))
merge(left, right, out)
copy(in, out)
s <- true
}
func BijectiveBurrowsWheelerCoder(input <-chan []byte) Coder8 {
output := make(chan []byte)
go func() {
var lyndon Lyndon
var rotations Rotations
wait := make(chan bool)
var buffer []uint8
for block := range input {
if cap(buffer) < len(block) {
buffer = make([]uint8, len(block))
} else {
buffer = buffer[:len(block)]
}
copy(buffer, block)
lyndon.Factor(buffer)
/* rotate */
if length := len(block); cap(rotations) < length {
rotations = make(Rotations, length)
} else {
rotations = rotations[:length]
}
r := 0
for _, word := range lyndon.Words {
for i, _ := range word {
rotations[r], r = rotation{i, word}, r + 1
}
}
go psort(rotations, wait)
<-wait
/* output the last character of each rotation */
for i, j := range rotations {
if j.int == 0 {
j.int = len(j.s)
}
block[i] = j.s[j.int - 1]
}
output <- block
}
close(output)
}()
return Coder8{Alphabit:256, Input:output}
}
func BijectiveBurrowsWheelerDecoder(input <-chan []byte) Coder8 {
inverse := func(buffer []byte) {
length := len(buffer)
input, major, minor := make([]byte, length), [256]int {}, make([]int, length)
for k, v := range buffer {
input[k], minor[k], major[v] = v, major[v], major[v] + 1
}
sum := 0
for k, v := range major {
major[k], sum = sum, sum + v
}
j := length - 1
for k, _ := range input {
for minor[k] != -1 {
buffer[j], j, k, minor[k] = input[k], j - 1, major[input[k]] + minor[k], -1
}
}
}
buffer, i := []byte(nil), 0
add := func(symbol uint8) bool {
if len(buffer) == 0 {
next, ok := <-input
if !ok {
return true
}
buffer = next
}
buffer[i], i = symbol, i + 1
if i == len(buffer) {
inverse(buffer)
next, ok := <-input
if !ok {
return true
}
buffer, i = next, 0
}
return false
}
return Coder8{Alphabit:256, Output:add}
}
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