/
base58.go
104 lines (92 loc) · 2.59 KB
/
base58.go
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package bitcoin
//----------------------------------------------------------------------
// This file is part of Gospel.
// Copyright (C) 2011-2023 Bernd Fix >Y<
//
// Gospel is free software: you can redistribute it and/or modify it
// under the terms of the GNU Affero General Public License as published
// by the Free Software Foundation, either version 3 of the License,
// or (at your option) any later version.
//
// Gospel 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
// Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
//
// SPDX-License-Identifier: AGPL3.0-or-later
//----------------------------------------------------------------------
import (
"bytes"
"errors"
gerr "github.com/bfix/gospel/errors"
"github.com/bfix/gospel/math"
)
var (
alphabet = []byte("123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz")
b58 = math.NewInt(58)
)
// Error codes
var (
ErrBtcBase58Decoding = errors.New("base58 decoding error -- unknown character")
)
// Base58Encode converts byte array to base58 string representation
func Base58Encode(in []byte) string {
// convert byte array to integer
val := math.NewIntFromBytes(in)
// convert integer to base58 representation
b := []byte{}
var m *math.Int
for val.Cmp(math.ZERO) > 0 {
val, m = val.DivMod(b58)
b = append(b, alphabet[int(m.Int64())])
}
// handle leading zero bytes in input
for _, x := range in {
if x == 0 {
b = append(b, alphabet[0])
} else {
break
}
}
// return base58 representation
return string(reverse(b))
}
// Base58Decode converts a base58 representation into byte array
func Base58Decode(s string) (data []byte, err error) {
// convert string to byte array
in := []byte(s)
// convert base58 to integer (ignores leading zeros)
val := math.ZERO
for _, b := range in {
pos := bytes.IndexByte(alphabet, b)
if pos == -1 {
err = gerr.New(ErrBtcBase58Decoding, "char '%c'", b)
return
}
val = val.Mul(b58).Add(math.NewInt(int64(pos)))
}
// prefix byte array with leading zeros
pf := []byte{}
for _, x := range s {
if byte(x) == alphabet[0] {
pf = append(pf, 0)
} else {
break
}
}
// return final byte array
data = append(pf, val.Bytes()...)
return
}
// reverse byte array
func reverse(in []byte) []byte {
n := len(in)
out := make([]byte, n)
for i := 0; i < n; i++ {
out[n-i-1] = in[i]
}
return out
}