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