1 files changed, 62 insertions, 0 deletions
diff --git a/vendor/github.com/boombuler/barcode/utils/galoisfield.go b/vendor/github.com/boombuler/barcode/utils/galoisfield.go
new file mode 100644
index 0000000..6f077d7
--- /dev/null
+++ b/vendor/github.com/boombuler/barcode/utils/galoisfield.go
@@ -0,0 +1,62 @@
+package utils
+
+// GaloisField encapsulates galois field arithmetics
+type GaloisField struct {
+	ALogTbl []int
+	LogTbl  []int
+}
+
+// NewGaloisField creates a new falois field
+func NewGaloisField(pp int) *GaloisField {
+	result := new(GaloisField)
+	fldSize := 256
+
+	result.ALogTbl = make([]int, fldSize)
+	result.LogTbl = make([]int, fldSize)
+
+	x := 1
+	for i := 0; i < fldSize; i++ {
+		result.ALogTbl[i] = x
+		x = x * 2
+		if x >= fldSize {
+			x = (x ^ pp) & (fldSize - 1)
+		}
+	}
+
+	for i := 0; i < fldSize; i++ {
+		result.LogTbl[result.ALogTbl[i]] = int(i)
+	}
+
+	return result
+}
+
+func (gf *GaloisField) Zero() *GFPoly {
+	return NewGFPoly(gf, []byte{0})
+}
+
+// AddOrSub add or substract two numbers
+func (gf *GaloisField) AddOrSub(a, b int) int {
+	return a ^ b
+}
+
+// Multiply multiplys two numbers
+func (gf *GaloisField) Multiply(a, b int) int {
+	if a == 0 || b == 0 {
+		return 0
+	}
+	return gf.ALogTbl[(gf.LogTbl[a]+gf.LogTbl[b])%255]
+}
+
+// Divide divides two numbers
+func (gf *GaloisField) Divide(a, b int) int {
+	if b == 0 {
+		panic("divide by zero")
+	} else if a == 0 {
+		return 0
+	}
+	return gf.ALogTbl[(gf.LogTbl[a]-gf.LogTbl[b])%255]
+}
+
+func (gf *GaloisField) Invers(num int) int {
+	return gf.ALogTbl[255-gf.LogTbl[num]]
+}