123 lines
4.1 KiB
JavaScript
123 lines
4.1 KiB
JavaScript
'use strict';
|
|
// base-x encoding / decoding
|
|
// Copyright (c) 2018 base-x contributors
|
|
// Copyright (c) 2014-2018 The Bitcoin Core developers (base58.cpp)
|
|
// Distributed under the MIT software license, see the accompanying
|
|
// file LICENSE or http://www.opensource.org/licenses/mit-license.php.
|
|
(function(){
|
|
this.baseX = function base (ALPHABET) {
|
|
if (ALPHABET.length >= 255) { throw new TypeError('Alphabet too long') }
|
|
var BASE_MAP = new Uint8Array(256)
|
|
for (var j = 0; j < BASE_MAP.length; j++) {
|
|
BASE_MAP[j] = 255
|
|
}
|
|
for (var i = 0; i < ALPHABET.length; i++) {
|
|
var x = ALPHABET.charAt(i)
|
|
var xc = x.charCodeAt(0)
|
|
if (BASE_MAP[xc] !== 255) { throw new TypeError(x + ' is ambiguous') }
|
|
BASE_MAP[xc] = i
|
|
}
|
|
var BASE = ALPHABET.length
|
|
var LEADER = ALPHABET.charAt(0)
|
|
var FACTOR = Math.log(BASE) / Math.log(256) // log(BASE) / log(256), rounded up
|
|
var iFACTOR = Math.log(256) / Math.log(BASE) // log(256) / log(BASE), rounded up
|
|
function encode (source) {
|
|
if (source instanceof Uint8Array) {
|
|
} else if (ArrayBuffer.isView(source)) {
|
|
source = new Uint8Array(source.buffer, source.byteOffset, source.byteLength)
|
|
} else if (Array.isArray(source)) {
|
|
source = Uint8Array.from(source)
|
|
}
|
|
if (!(source instanceof Uint8Array)) { throw new TypeError('Expected Uint8Array') }
|
|
if (source.length === 0) { return '' }
|
|
// Skip & count leading zeroes.
|
|
var zeroes = 0
|
|
var length = 0
|
|
var pbegin = 0
|
|
var pend = source.length
|
|
while (pbegin !== pend && source[pbegin] === 0) {
|
|
pbegin++
|
|
zeroes++
|
|
}
|
|
// Allocate enough space in big-endian base58 representation.
|
|
var size = ((pend - pbegin) * iFACTOR + 1) >>> 0
|
|
var b58 = new Uint8Array(size)
|
|
// Process the bytes.
|
|
while (pbegin !== pend) {
|
|
var carry = source[pbegin]
|
|
// Apply "b58 = b58 * 256 + ch".
|
|
var i = 0
|
|
for (var it1 = size - 1; (carry !== 0 || i < length) && (it1 !== -1); it1--, i++) {
|
|
carry += (256 * b58[it1]) >>> 0
|
|
b58[it1] = (carry % BASE) >>> 0
|
|
carry = (carry / BASE) >>> 0
|
|
}
|
|
if (carry !== 0) { throw new Error('Non-zero carry') }
|
|
length = i
|
|
pbegin++
|
|
}
|
|
// Skip leading zeroes in base58 result.
|
|
var it2 = size - length
|
|
while (it2 !== size && b58[it2] === 0) {
|
|
it2++
|
|
}
|
|
// Translate the result into a string.
|
|
var str = LEADER.repeat(zeroes)
|
|
for (; it2 < size; ++it2) { str += ALPHABET.charAt(b58[it2]) }
|
|
return str
|
|
}
|
|
function decodeUnsafe (source) {
|
|
if (typeof source !== 'string') { throw new TypeError('Expected String') }
|
|
if (source.length === 0) { return new Uint8Array() }
|
|
var psz = 0
|
|
// Skip and count leading '1's.
|
|
var zeroes = 0
|
|
var length = 0
|
|
while (source[psz] === LEADER) {
|
|
zeroes++
|
|
psz++
|
|
}
|
|
// Allocate enough space in big-endian base256 representation.
|
|
var size = (((source.length - psz) * FACTOR) + 1) >>> 0 // log(58) / log(256), rounded up.
|
|
var b256 = new Uint8Array(size)
|
|
// Process the characters.
|
|
while (source[psz]) {
|
|
// Decode character
|
|
var carry = BASE_MAP[source.charCodeAt(psz)]
|
|
// Invalid character
|
|
if (carry === 255) { return }
|
|
var i = 0
|
|
for (var it3 = size - 1; (carry !== 0 || i < length) && (it3 !== -1); it3--, i++) {
|
|
carry += (BASE * b256[it3]) >>> 0
|
|
b256[it3] = (carry % 256) >>> 0
|
|
carry = (carry / 256) >>> 0
|
|
}
|
|
if (carry !== 0) { throw new Error('Non-zero carry') }
|
|
length = i
|
|
psz++
|
|
}
|
|
// Skip leading zeroes in b256.
|
|
var it4 = size - length
|
|
while (it4 !== size && b256[it4] === 0) {
|
|
it4++
|
|
}
|
|
var vch = new Uint8Array(zeroes + (size - it4))
|
|
var j = zeroes
|
|
while (it4 !== size) {
|
|
vch[j++] = b256[it4++]
|
|
}
|
|
return vch
|
|
}
|
|
function decode (string) {
|
|
var buffer = decodeUnsafe(string)
|
|
if (buffer) { return buffer }
|
|
throw new Error('Non-base' + BASE + ' character')
|
|
}
|
|
return {
|
|
encode: encode,
|
|
decodeUnsafe: decodeUnsafe,
|
|
decode: decode
|
|
}
|
|
}
|
|
}).call(this);
|