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base58.go
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base58.go
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/* license: https://mit-license.org
* ==============================================================================
* The MIT License (MIT)
*
* Copyright (c) 2020 Albert Moky
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
* ==============================================================================
*/
package format
import (
"bytes"
. "github.com/dimchat/mkm-go/format"
"math/big"
)
var base58Alphabets = []byte("123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz")
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]
}
}
type Base58Coder struct {}
func (coder Base58Coder) Init() DataCoder {
return coder
}
//-------- IDataCoder
func (coder Base58Coder) Encode(data []byte) string {
x := big.NewInt(0).SetBytes(data)
base := big.NewInt(58)
zero := big.NewInt(0)
mod := &big.Int{}
var result []byte
for x.Cmp(zero) != 0 {
x.DivMod(x, base, mod)
result = append(result, base58Alphabets[mod.Int64()])
}
ReverseBytes(result)
return string(result)
}
func (coder Base58Coder) Decode(string string) []byte {
result := big.NewInt(0)
input := []byte(string)
for _, b := range input {
charIndex := bytes.IndexByte(base58Alphabets, b)
result.Mul(result, big.NewInt(58))
result.Add(result, big.NewInt(int64(charIndex)))
}
decoded := result.Bytes()
if input[0] == base58Alphabets[0] {
decoded = append([]byte{0x00}, decoded...)
}
return decoded
}