status-go/vendor/github.com/btcsuite/btcutil/base58/base58.go

76 lines
1.4 KiB
Go
Raw Normal View History

// Copyright (c) 2013-2015 The btcsuite developers
// Use of this source code is governed by an ISC
// license that can be found in the LICENSE file.
package base58
import (
"math/big"
)
//go:generate go run genalphabet.go
var bigRadix = big.NewInt(58)
var bigZero = big.NewInt(0)
// Decode decodes a modified base58 string to a byte slice.
func Decode(b string) []byte {
answer := big.NewInt(0)
j := big.NewInt(1)
scratch := new(big.Int)
for i := len(b) - 1; i >= 0; i-- {
tmp := b58[b[i]]
if tmp == 255 {
return []byte("")
}
scratch.SetInt64(int64(tmp))
scratch.Mul(j, scratch)
answer.Add(answer, scratch)
j.Mul(j, bigRadix)
}
tmpval := answer.Bytes()
var numZeros int
for numZeros = 0; numZeros < len(b); numZeros++ {
if b[numZeros] != alphabetIdx0 {
break
}
}
flen := numZeros + len(tmpval)
val := make([]byte, flen)
copy(val[numZeros:], tmpval)
return val
}
// Encode encodes a byte slice to a modified base58 string.
func Encode(b []byte) string {
x := new(big.Int)
x.SetBytes(b)
answer := make([]byte, 0, len(b)*136/100)
for x.Cmp(bigZero) > 0 {
mod := new(big.Int)
x.DivMod(x, bigRadix, mod)
answer = append(answer, alphabet[mod.Int64()])
}
// leading zero bytes
for _, i := range b {
if i != 0 {
break
}
answer = append(answer, alphabetIdx0)
}
// reverse
alen := len(answer)
for i := 0; i < alen/2; i++ {
answer[i], answer[alen-1-i] = answer[alen-1-i], answer[i]
}
return string(answer)
}