neo-go/pkg/crypto/base58.go

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package crypto
import (
"bytes"
"crypto/sha256"
"fmt"
"math/big"
"github.com/pkg/errors"
)
const prefix rune = '1'
var decodeMap = map[rune]int64{
'1': 0, '2': 1, '3': 2, '4': 3, '5': 4,
'6': 5, '7': 6, '8': 7, '9': 8, 'A': 9,
'B': 10, 'C': 11, 'D': 12, 'E': 13, 'F': 14,
'G': 15, 'H': 16, 'J': 17, 'K': 18, 'L': 19,
'M': 20, 'N': 21, 'P': 22, 'Q': 23, 'R': 24,
'S': 25, 'T': 26, 'U': 27, 'V': 28, 'W': 29,
'X': 30, 'Y': 31, 'Z': 32, 'a': 33, 'b': 34,
'c': 35, 'd': 36, 'e': 37, 'f': 38, 'g': 39,
'h': 40, 'i': 41, 'j': 42, 'k': 43, 'm': 44,
'n': 45, 'o': 46, 'p': 47, 'q': 48, 'r': 49,
's': 50, 't': 51, 'u': 52, 'v': 53, 'w': 54,
'x': 55, 'y': 56, 'z': 57,
}
// Base58Decode decodes the base58 encoded string.
func Base58Decode(s string) ([]byte, error) {
var (
startIndex = 0
zero = 0
)
for i, c := range s {
if c == prefix {
zero++
} else {
startIndex = i
break
}
}
var (
n = big.NewInt(0)
div = big.NewInt(58)
)
for _, c := range s[startIndex:] {
charIndex, ok := decodeMap[c]
if !ok {
return nil, fmt.Errorf(
"invalid character '%c' when decoding this base58 string: '%s'", c, s,
)
}
n.Add(n.Mul(n, div), big.NewInt(charIndex))
}
out := n.Bytes()
buf := make([]byte, zero+len(out))
copy(buf[zero:], out)
return buf, nil
}
// Base58Encode encodes a byte slice to be a base58 encoded string.
func Base58Encode(bytes []byte) string {
var (
lookupTable = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"
x = new(big.Int).SetBytes(bytes)
r = new(big.Int)
m = big.NewInt(58)
zero = big.NewInt(0)
encoded string
)
for x.Cmp(zero) > 0 {
x.QuoRem(x, m, r)
encoded = string(lookupTable[r.Int64()]) + encoded
}
return encoded
}
// Base58CheckDecode decodes the given string.
func Base58CheckDecode(s string) (b []byte, err error) {
b, err = Base58Decode(s)
if err != nil {
return nil, err
}
for i := 0; i < len(s); i++ {
if s[i] != '1' {
break
}
b = append([]byte{0x00}, b...)
}
if len(b) < 5 {
return nil, errors.New("invalid base-58 check string: missing checksum.")
}
sha := sha256.New()
if _, err = sha.Write(b[:len(b)-4]); err != nil {
return nil, err
}
hash := sha.Sum(nil)
sha.Reset()
if _, err = sha.Write(hash); err != nil {
return nil, err
}
hash = sha.Sum(nil)
if !bytes.Equal(hash[0:4], b[len(b)-4:]) {
return nil, errors.New("invalid base-58 check string: invalid checksum.")
}
// Strip the 4 byte long hash.
b = b[:len(b)-4]
return b, nil
}
// Base58checkEncode encodes b into a base-58 check encoded string.
func Base58CheckEncode(b []byte) string {
sha := sha256.New()
sha.Write(b)
hash := sha.Sum(nil)
sha.Reset()
sha.Write(hash)
hash = sha.Sum(nil)
b = append(b, hash[0:4]...)
return Base58Encode(b)
}