bugfix for datamatrix error correction
more tests and code cleanup
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Florian Sundermann committed
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19 files changed
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@@ -0,0 +1,117 @@
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package utils
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// utility class that contains bits
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type BitList struct {
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count int
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data []int32
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}
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// returns a new BitList with the given length
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// all bits are initialize with false
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func NewBitList(capacity int) *BitList {
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bl := new(BitList)
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bl.count = capacity
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x := 0
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if capacity%32 != 0 {
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x = 1
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}
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bl.data = make([]int32, capacity/32+x)
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return bl
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}
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// returns the number of contained bits
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func (bl *BitList) Len() int {
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return bl.count
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}
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func (bl *BitList) grow() {
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growBy := len(bl.data)
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if growBy < 128 {
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growBy = 128
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} else if growBy >= 1024 {
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growBy = 1024
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}
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nd := make([]int32, len(bl.data)+growBy)
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copy(nd, bl.data)
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bl.data = nd
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}
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// appends the given bit to the end of the list
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func (bl *BitList) AddBit(bit bool) {
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itmIndex := bl.count / 32
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for itmIndex >= len(bl.data) {
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bl.grow()
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}
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bl.SetBit(bl.count, bit)
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bl.count++
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}
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// sets the bit at the given index to the given value
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func (bl *BitList) SetBit(index int, value bool) {
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itmIndex := index / 32
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itmBitShift := 31 - (index % 32)
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if value {
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bl.data[itmIndex] = bl.data[itmIndex] | 1<<uint(itmBitShift)
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} else {
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bl.data[itmIndex] = bl.data[itmIndex] & ^(1 << uint(itmBitShift))
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}
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}
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// returns the bit at the given index
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func (bl *BitList) GetBit(index int) bool {
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itmIndex := index / 32
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itmBitShift := 31 - (index % 32)
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return ((bl.data[itmIndex] >> uint(itmBitShift)) & 1) == 1
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}
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// appends all 8 bits of the given byte to the end of the list
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func (bl *BitList) AddByte(b byte) {
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for i := 7; i >= 0; i-- {
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bl.AddBit(((b >> uint(i)) & 1) == 1)
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}
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}
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// appends the last (LSB) 'count' bits of 'b' the the end of the list
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func (bl *BitList) AddBits(b int, count byte) {
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for i := int(count - 1); i >= 0; i-- {
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bl.AddBit(((b >> uint(i)) & 1) == 1)
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}
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}
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// returns all bits of the BitList as a []byte
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func (bl *BitList) GetBytes() []byte {
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len := bl.count >> 3
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if (bl.count % 8) != 0 {
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len += 1
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}
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result := make([]byte, len)
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for i := 0; i < len; i++ {
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shift := (3 - (i % 4)) * 8
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result[i] = (byte)((bl.data[i/4] >> uint(shift)) & 0xFF)
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}
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return result
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}
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// iterates through all bytes contained in the BitList
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func (bl *BitList) IterateBytes() <-chan byte {
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res := make(chan byte)
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go func() {
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c := bl.count
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shift := 24
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i := 0
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for c > 0 {
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res <- byte((bl.data[i] >> uint(shift)) & 0xFF)
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shift -= 8
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if shift < 0 {
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shift = 24
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i += 1
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}
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c -= 8
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}
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close(res)
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}()
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return res
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}
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@@ -0,0 +1,49 @@
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package utils
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type GaloisField struct {
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ALogTbl []int
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LogTbl []int
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}
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func NewGaloisField(pp int) *GaloisField {
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result := new(GaloisField)
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fldSize := 256
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result.ALogTbl = make([]int, fldSize)
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result.LogTbl = make([]int, fldSize)
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x := 1
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for i := 0; i < fldSize; i++ {
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result.ALogTbl[i] = x
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x = x * 2
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if x >= fldSize {
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x = (x ^ pp) & (fldSize - 1)
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}
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}
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for i := 0; i < fldSize; i++ {
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result.LogTbl[result.ALogTbl[i]] = int(i)
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}
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return result
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}
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func (gf *GaloisField) AddOrSub(a, b int) int {
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return a ^ b
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}
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func (gf *GaloisField) Multiply(a, b int) int {
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if a == 0 || b == 0 {
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return 0
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}
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return gf.ALogTbl[(gf.LogTbl[a]+gf.LogTbl[b])%255]
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}
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func (gf *GaloisField) Divide(a, b int) int {
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if b == 0 {
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panic("divide by zero")
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} else if a == 0 {
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return 0
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}
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return gf.ALogTbl[(gf.LogTbl[a]-gf.LogTbl[b])%255]
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}
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@@ -0,0 +1,59 @@
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package utils
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import (
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"testing"
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)
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func Test_GF(t *testing.T) {
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log := []int{
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0, 255, 1, 240, 2, 225, 241, 53, 3, 38, 226, 133, 242, 43, 54, 210,
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4, 195, 39, 114, 227, 106, 134, 28, 243, 140, 44, 23, 55, 118, 211, 234,
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5, 219, 196, 96, 40, 222, 115, 103, 228, 78, 107, 125, 135, 8, 29, 162,
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244, 186, 141, 180, 45, 99, 24, 49, 56, 13, 119, 153, 212, 199, 235, 91,
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6, 76, 220, 217, 197, 11, 97, 184, 41, 36, 223, 253, 116, 138, 104, 193,
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229, 86, 79, 171, 108, 165, 126, 145, 136, 34, 9, 74, 30, 32, 163, 84,
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245, 173, 187, 204, 142, 81, 181, 190, 46, 88, 100, 159, 25, 231, 50, 207,
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57, 147, 14, 67, 120, 128, 154, 248, 213, 167, 200, 63, 236, 110, 92, 176,
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7, 161, 77, 124, 221, 102, 218, 95, 198, 90, 12, 152, 98, 48, 185, 179,
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42, 209, 37, 132, 224, 52, 254, 239, 117, 233, 139, 22, 105, 27, 194, 113,
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230, 206, 87, 158, 80, 189, 172, 203, 109, 175, 166, 62, 127, 247, 146, 66,
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137, 192, 35, 252, 10, 183, 75, 216, 31, 83, 33, 73, 164, 144, 85, 170,
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246, 65, 174, 61, 188, 202, 205, 157, 143, 169, 82, 72, 182, 215, 191, 251,
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47, 178, 89, 151, 101, 94, 160, 123, 26, 112, 232, 21, 51, 238, 208, 131,
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58, 69, 148, 18, 15, 16, 68, 17, 121, 149, 129, 19, 155, 59, 249, 70,
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214, 250, 168, 71, 201, 156, 64, 60, 237, 130, 111, 20, 93, 122, 177, 150,
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}
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alog := []int{
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1, 2, 4, 8, 16, 32, 64, 128, 45, 90, 180, 69, 138, 57, 114, 228,
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229, 231, 227, 235, 251, 219, 155, 27, 54, 108, 216, 157, 23, 46, 92, 184,
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93, 186, 89, 178, 73, 146, 9, 18, 36, 72, 144, 13, 26, 52, 104, 208,
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141, 55, 110, 220, 149, 7, 14, 28, 56, 112, 224, 237, 247, 195, 171, 123,
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246, 193, 175, 115, 230, 225, 239, 243, 203, 187, 91, 182, 65, 130, 41, 82,
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164, 101, 202, 185, 95, 190, 81, 162, 105, 210, 137, 63, 126, 252, 213, 135,
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35, 70, 140, 53, 106, 212, 133, 39, 78, 156, 21, 42, 84, 168, 125, 250,
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217, 159, 19, 38, 76, 152, 29, 58, 116, 232, 253, 215, 131, 43, 86, 172,
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117, 234, 249, 223, 147, 11, 22, 44, 88, 176, 77, 154, 25, 50, 100, 200,
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189, 87, 174, 113, 226, 233, 255, 211, 139, 59, 118, 236, 245, 199, 163, 107,
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214, 129, 47, 94, 188, 85, 170, 121, 242, 201, 191, 83, 166, 97, 194, 169,
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127, 254, 209, 143, 51, 102, 204, 181, 71, 142, 49, 98, 196, 165, 103, 206,
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177, 79, 158, 17, 34, 68, 136, 61, 122, 244, 197, 167, 99, 198, 161, 111,
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222, 145, 15, 30, 60, 120, 240, 205, 183, 67, 134, 33, 66, 132, 37, 74,
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148, 5, 10, 20, 40, 80, 160, 109, 218, 153, 31, 62, 124, 248, 221, 151,
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3, 6, 12, 24, 48, 96, 192, 173, 119, 238, 241, 207, 179, 75, 150, 1,
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}
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gf := NewGaloisField(301)
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if len(gf.LogTbl) != len(gf.ALogTbl) || len(gf.LogTbl) != len(log) {
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t.Fail()
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}
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for i := 0; i < len(log); i++ {
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if gf.LogTbl[i] != log[i] {
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t.Error("Invalid Log Table")
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}
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if gf.ALogTbl[i] != alog[i] {
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t.Error("Invalid ALog Table")
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}
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}
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}
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