59 lines
1.3 KiB
Go
59 lines
1.3 KiB
Go
package qr
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import (
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"github.com/boombuler/barcode/utils"
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)
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type errorCorrection struct {
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fld *utils.GaloisField
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polynomes map[byte][]byte
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}
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var ec *errorCorrection = newGF()
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func newGF() *errorCorrection {
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return &errorCorrection{utils.NewGaloisField(285), make(map[byte][]byte)}
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}
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func (ec *errorCorrection) getPolynomial(eccc byte) []byte {
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_, ok := ec.polynomes[eccc]
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if !ok {
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if eccc == 1 {
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ec.polynomes[eccc] = []byte{0, 0}
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} else {
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b1 := ec.getPolynomial(eccc - 1)
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result := make([]byte, eccc+1)
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for x := 0; x < len(b1); x++ {
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tmp1 := (int(b1[x]) + int(eccc-1)) % 255
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if x == 0 {
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result[x] = b1[x]
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} else {
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tmp0 := int(ec.fld.ALogTbl[result[x]]) ^ int(ec.fld.ALogTbl[b1[x]])
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result[x] = byte(ec.fld.LogTbl[tmp0])
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}
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result[x+1] = byte(tmp1)
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}
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ec.polynomes[eccc] = result
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}
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}
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return ec.polynomes[eccc]
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}
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func (ec *errorCorrection) calcECC(data []byte, eccCount byte) []byte {
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tmp := make([]byte, len(data)+int(eccCount))
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copy(tmp, data)
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generator := ec.getPolynomial(eccCount)
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for i := 0; i < len(data); i++ {
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alpha := ec.fld.LogTbl[tmp[i]]
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for j := 0; j < len(generator); j++ {
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idx := (int(alpha) + int(generator[j])) % 255
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polyJ := ec.fld.ALogTbl[idx]
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tmp[i+j] = byte(ec.fld.AddOrSub(int(tmp[i+j]), polyJ))
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}
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}
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return tmp[len(data):]
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}
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