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