init: v1.0.0

gmath/int.go

@@ -0,0 +1,70 @@
+package gmath
+
+import (
+	"math/big"
+)
+
+// BigIntx is a big.Int of x
+var (
+	BigInt0    = big.NewInt(0)
+	BigInt1    = big.NewInt(1)
+	BigInt2    = big.NewInt(2)
+	BigInt3    = big.NewInt(3)
+	BigInt4    = big.NewInt(4)
+	BigInt5    = big.NewInt(5)
+	BigInt6    = big.NewInt(6)
+	BigInt7    = big.NewInt(7)
+	BigInt8    = big.NewInt(8)
+	BigInt9    = big.NewInt(9)
+	BigInt10   = big.NewInt(10)
+	BigInt11   = big.NewInt(11)
+	BigInt12   = big.NewInt(12)
+	BigInt2256 = new(big.Int).Lsh(BigInt1, 256) // = 2^256
+)
+
+// IsBigInt0 return if x==0
+func IsBigInt0(x *big.Int) bool {
+	return x.Sign() == 0
+}
+
+// IsBigInt1 return if x==0
+func IsBigInt1(x *big.Int) bool {
+	return x.Cmp(BigInt1) == 0
+}
+
+// ClearBigInt set memory of x be 0
+func ClearBigInt(x *big.Int) {
+	if x == nil {
+		return
+	}
+	words := x.Bits()
+	for i := range words {
+		words[i] = 0
+	}
+	x.SetInt64(0)
+}
+
+type bytes interface {
+	Bytes() []byte
+}
+
+// ToNBytes ouput a bytes to fix n bytes. extend as 0.
+func ToNBytes(b bytes, n int) []byte {
+	abs := b.Bytes()
+	l := len(abs)
+	var s []byte
+	// l==n is the most case (255/256)
+	if l >= n {
+		s = abs[l-n : l]
+	} else {
+		s = make([]byte, n)
+		copy(s[n-l:], abs)
+	}
+	return s
+}
+
+// BigIntToNByte return a n byte slice of the input big.Int as big-endian
+// if len(a.Bytes()) > n, then only the lower n bytes are return
+func BigIntToNByte(a *big.Int, n int) []byte {
+	return ToNBytes(a, n)
+}