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base58.go
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base58.go
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// Copyright (c) 2018 Yuriy Lisovskiy
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
package base58
import (
"bytes"
"math/big"
)
var b58Alphabet = []byte("123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz")
func Encode(input []byte) []byte {
var result []byte
x := big.NewInt(0).SetBytes(input)
base := big.NewInt(int64(len(b58Alphabet)))
zero := big.NewInt(0)
mod := &big.Int{}
for x.Cmp(zero) != 0 {
x.DivMod(x, base, mod)
result = append(result, b58Alphabet[mod.Int64()])
}
reverseBytes(result)
for b := range input {
if b == 0x00 {
result = append([]byte{b58Alphabet[0]}, result...)
} else {
break
}
}
return result
}
func Decode(input []byte) []byte {
result := big.NewInt(0)
zeroBytes := 0
for b := range input {
if b == 0x00 {
zeroBytes++
}
}
payload := input[zeroBytes:]
for _, b := range payload {
charIndex := bytes.IndexByte(b58Alphabet, b)
result.Mul(result, big.NewInt(58))
result.Add(result, big.NewInt(int64(charIndex)))
}
decoded := result.Bytes()
decoded = append(bytes.Repeat([]byte{byte(0x00)}, zeroBytes), decoded...)
return decoded
}
func reverseBytes(data []byte) {
for i, j := 0, len(data)-1; i < j; i, j = i+1, j-1 {
data[i], data[j] = data[j], data[i]
}
}