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big.go
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big.go
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// Copyright gotools (https://github.com/zerjioang/gotools)
// SPDX-License-Identifier: GNU GPL v3
package fixtures
import (
"math/big"
)
const (
// number of bits in a big.Word
wordBits = 32 << (uint64(^big.Word(0)) >> 63)
// number of bytes in a big.Word
wordBytes = wordBits / 8
)
var (
Big1 = big.NewInt(1)
Big0 = big.NewInt(0)
)
// HexOrDecimal256 marshals big.Int as hex or decimal.
type HexOrDecimal256 big.Int
// PaddedBigBytes encodes a big integer as a big-endian byte slice. The length
// of the slice is at least n bytes.
func PaddedBigBytes(bigint *big.Int, n int) []byte {
if bigint.BitLen()/8 >= n {
return bigint.Bytes()
}
ret := make([]byte, n)
ReadBits(bigint, ret)
return ret
}
// ReadBits encodes the absolute value of bigint as big-endian bytes. Callers must ensure
// that buf has enough space. If buf is too short the result will be incomplete.
func ReadBits(bigint *big.Int, buf []byte) {
i := len(buf)
for _, d := range bigint.Bits() {
for j := 0; j < wordBytes && i > 0; j++ {
i--
buf[i] = byte(d)
d >>= 8
}
}
}
// ParseEthSignature parses s as a hexadecimal encoded signature for given message
// and returns, s, r and v values
func ParseEthSignature(signature string) (r string, s string, v string) {
data := signature[2:]
s = "0x" + data[0:64]
r = "0x" + data[64:128]
v = "0x" + data[128:130]
//TODO NOTE: v must be a decimal number, hence the second v_decimal that turns hex v into decimal v.
// TODO check that the resulting v_decimal must be either 27 or 28!
return
}
// ParseBig256 parses s as a 256 bit integer in decimal or hexadecimal syntax.
// Leading zeros are accepted. The empty string parses as zero.
func ParseBig256(s string) (*big.Int, bool) {
if s == "" {
return new(big.Int), true
}
var bigint *big.Int
var ok bool
if len(s) >= 2 && (s[:2] == "0x" || s[:2] == "0X") {
bigint, ok = new(big.Int).SetString(s[2:], 16)
} else {
bigint, ok = new(big.Int).SetString(s, 10)
}
if ok && bigint.BitLen() > 256 {
bigint, ok = nil, false
}
return bigint, ok
}
// MustParseBig256 parses s as a 256 bit big integer and panics if the string is invalid.
func MustParseBig256(s string) *big.Int {
v, ok := ParseBig256(s)
if !ok {
panic("invalid 256 bit integer: " + s)
}
return v
}