/usr/share/gocode/src/github.com/templexxx/reedsolomon/matrix.go is in golang-github-templexxx-reedsolomon-dev 0.1.1+git20170927.7092926-4.
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 | package reedsolomon
import "errors"
type matrix []byte
func genEncMatrixCauchy(d, p int) matrix {
t := d + p
m := make([]byte, t*d)
for i := 0; i < d; i++ {
m[i*d+i] = byte(1)
}
d2 := d * d
for i := d; i < t; i++ {
for j := 0; j < d; j++ {
d := i ^ j
a := inverseTbl[d]
m[d2] = byte(a)
d2++
}
}
return m
}
func gfExp(b byte, n int) byte {
if n == 0 {
return 1
}
if b == 0 {
return 0
}
a := logTbl[b]
ret := int(a) * n
for ret >= 255 {
ret -= 255
}
return byte(expTbl[ret])
}
func genVandMatrix(vm []byte, t, d int) {
for i := 0; i < t; i++ {
for j := 0; j < d; j++ {
vm[i*d+j] = gfExp(byte(i), j)
}
}
}
func (m matrix) mul(right matrix, rows, cols int, r []byte) {
for i := 0; i < rows; i++ {
for j := 0; j < cols; j++ {
var v byte
for k := 0; k < cols; k++ {
v ^= gfMul(m[i*cols+k], right[k*cols+j])
}
r[i*cols+j] = v
}
}
}
func genEncMatrixVand(d, p int) (matrix, error) {
t := d + p
buf := make([]byte, (2*t+4*d)*d)
vm := buf[:t*d]
genVandMatrix(vm, t, d)
top := buf[t*d : (t+d)*d]
copy(top, vm[:d*d])
raw := buf[(t+d)*d : (t+3*d)*d]
im := buf[(t+3*d)*d : (t+4*d)*d]
err := matrix(top).invert(raw, d, im)
if err != nil {
return nil, err
}
r := buf[(t+4*d)*d : (2*t+4*d)*d]
matrix(vm).mul(im, t, d, r)
return matrix(r), nil
}
// [I|m'] -> [m']
func (m matrix) subMatrix(n int, r []byte) {
for i := 0; i < n; i++ {
off := i * n
copy(r[off:off+n], m[2*off+n:2*(off+n)])
}
}
func (m matrix) invert(raw matrix, n int, im []byte) error {
// [m] -> [m|I]
for i := 0; i < n; i++ {
t := i * n
copy(raw[2*t:2*t+n], m[t:t+n])
raw[2*t+i+n] = byte(1)
}
err := gauss(raw, n)
if err != nil {
return err
}
raw.subMatrix(n, im)
return nil
}
func (m matrix) swap(i, j, n int) {
for k := 0; k < n; k++ {
m[i*n+k], m[j*n+k] = m[j*n+k], m[i*n+k]
}
}
func gfMul(a, b byte) byte {
return mulTbl[a][b]
}
var errSingular = errors.New("rs.invert: matrix is singular")
// [m|I] -> [I|m']
func gauss(m matrix, n int) error {
n2 := 2 * n
for i := 0; i < n; i++ {
if m[i*n2+i] == 0 {
for j := i + 1; j < n; j++ {
if m[j*n2+i] != 0 {
m.swap(i, j, n2)
break
}
}
}
if m[i*n2+i] == 0 {
return errSingular
}
if m[i*n2+i] != 1 {
d := m[i*n2+i]
scale := inverseTbl[d]
for c := 0; c < n2; c++ {
m[i*n2+c] = gfMul(m[i*n2+c], scale)
}
}
for j := i + 1; j < n; j++ {
if m[j*n2+i] != 0 {
scale := m[j*n2+i]
for c := 0; c < n2; c++ {
m[j*n2+c] ^= gfMul(scale, m[i*n2+c])
}
}
}
}
for k := 0; k < n; k++ {
for j := 0; j < k; j++ {
if m[j*n2+k] != 0 {
scale := m[j*n2+k]
for c := 0; c < n2; c++ {
m[j*n2+c] ^= gfMul(scale, m[k*n2+c])
}
}
}
}
return nil
}
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