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base58.go
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base58.go
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package btcTransaction
import (
"errors"
"fmt"
"github.com/blocktree/go-owcrypt"
)
// Errors
var (
ErrorInvalidBase58String = errors.New("invalid base58 string")
)
// Alphabet: copy from https://en.wikipedia.org/wiki/Base58
var (
BitcoinAlphabet = NewAlphabet("123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz")
)
// Alphabet The base58 alphabet object.
type Alphabet struct {
encodeTable [58]rune
decodeTable [256]int
unicodeDecodeTable []rune
}
// Alphabet's string representation
func (alphabet Alphabet) String() string {
return string(alphabet.encodeTable[:])
}
// NewAlphabet create a custom alphabet from 58-length string.
// Note: len(rune(alphabet)) must be 58.
func NewAlphabet(alphabet string) *Alphabet {
alphabetRunes := []rune(alphabet)
if len(alphabetRunes) != 58 {
panic(fmt.Sprintf("Base58 Alphabet length must 58, but %d", len(alphabetRunes)))
}
ret := new(Alphabet)
for i := range ret.decodeTable {
ret.decodeTable[i] = -1
}
ret.unicodeDecodeTable = make([]rune, 0, 58*2)
for idx, ch := range alphabetRunes {
ret.encodeTable[idx] = ch
if ch >= 0 && ch < 256 {
ret.decodeTable[byte(ch)] = idx
} else {
ret.unicodeDecodeTable = append(ret.unicodeDecodeTable, ch)
ret.unicodeDecodeTable = append(ret.unicodeDecodeTable, rune(idx))
}
}
return ret
}
// Encode encode with custom alphabet
func Encode(input []byte, alphabet *Alphabet) string {
// prefix 0
inputLength := len(input)
prefixZeroes := 0
for prefixZeroes < inputLength && input[prefixZeroes] == 0 {
prefixZeroes++
}
capacity := inputLength*138/100 + 1 // log256 / log58
output := make([]byte, capacity)
outputReverseEnd := capacity - 1
for inputPos := prefixZeroes; inputPos < inputLength; inputPos++ {
carry := uint32(input[inputPos])
outputIdx := capacity - 1
for ; carry != 0 || outputIdx > outputReverseEnd; outputIdx-- {
carry += (uint32(output[outputIdx]) << 8) // XX << 8 same as: 256 * XX
output[outputIdx] = byte(carry % 58)
carry /= 58
}
outputReverseEnd = outputIdx
}
encodeTable := alphabet.encodeTable
// when not contains unicode, use []byte to improve performance
if len(alphabet.unicodeDecodeTable) == 0 {
retStrBytes := make([]byte, prefixZeroes+(capacity-1-outputReverseEnd))
for i := 0; i < prefixZeroes; i++ {
retStrBytes[i] = byte(encodeTable[0])
}
for i, n := range output[outputReverseEnd+1:] {
retStrBytes[prefixZeroes+i] = byte(encodeTable[n])
}
return string(retStrBytes)
}
retStrRunes := make([]rune, prefixZeroes+(capacity-1-outputReverseEnd))
for i := 0; i < prefixZeroes; i++ {
retStrRunes[i] = encodeTable[0]
}
for i, n := range output[outputReverseEnd+1:] {
retStrRunes[prefixZeroes+i] = encodeTable[n]
}
return string(retStrRunes)
}
// Decode docode with custom alphabet
func Decode(input string, alphabet *Alphabet) ([]byte, error) {
inputBytes := []rune(input)
inputLength := len(inputBytes)
capacity := inputLength*733/1000 + 1 // log(58) / log(256)
output := make([]byte, capacity)
outputReverseEnd := capacity - 1
// prefix 0
zero58Byte := alphabet.encodeTable[0]
prefixZeroes := 0
for prefixZeroes < inputLength && inputBytes[prefixZeroes] == zero58Byte {
prefixZeroes++
}
for inputPos := 0; inputPos < inputLength; inputPos++ {
carry := -1
target := inputBytes[inputPos]
if target >= 0 && target < 256 {
carry = alphabet.decodeTable[target]
} else { // unicode
for i := 0; i < len(alphabet.unicodeDecodeTable); i += 2 {
if alphabet.unicodeDecodeTable[i] == target {
carry = int(alphabet.unicodeDecodeTable[i+1])
break
}
}
}
if carry == -1 {
return nil, ErrorInvalidBase58String
}
outputIdx := capacity - 1
for ; carry != 0 || outputIdx > outputReverseEnd; outputIdx-- {
carry += 58 * int(output[outputIdx])
output[outputIdx] = byte(uint32(carry) & 0xff) // same as: byte(uint32(carry) % 256)
carry >>= 8 // same as: carry /= 256
}
outputReverseEnd = outputIdx
}
retBytes := make([]byte, prefixZeroes+(capacity-1-outputReverseEnd))
for i, n := range output[outputReverseEnd+1:] {
retBytes[prefixZeroes+i] = n
}
return retBytes, nil
}
//return prefix + hash + error
func DecodeCheck(address string) ([]byte, []byte, error) {
ret, err := Decode(address, BitcoinAlphabet)
if err != nil {
return nil, nil, errors.New("Invalid address!")
}
checksum := owcrypt.Hash(ret[:len(ret)-4], 0, owcrypt.HASH_ALG_DOUBLE_SHA256)[:4]
for i := 0; i < 4; i++ {
if checksum[i] != ret[len(ret)-4+i] {
return nil, nil, errors.New("Invalid address!")
}
}
prefixLen := len(ret) - 4 - 0x14
return ret[:prefixLen], ret[prefixLen : len(ret)-4], nil
}
func EncodeCheck(prefix []byte, hash []byte) string {
data := append(prefix, hash...)
checksum := owcrypt.Hash(data, 0, owcrypt.HASH_ALG_DOUBLE_SHA256)[:4]
data = append(data, checksum...)
return Encode(data, BitcoinAlphabet)
}