120 lines
3.9 KiB
JavaScript
120 lines
3.9 KiB
JavaScript
'use strict';
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// base-x encoding / decoding
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// based on https://github.com/cryptocoinjs/base-x 3.0.7
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// modification: removed Buffer dependency and node.modules entry
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// Copyright (c) 2018 base-x contributors
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// Copyright (c) 2014-2018 The Bitcoin Core developers (base58.cpp)
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// Distributed under the MIT software license, see the accompanying
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// file LICENSE or http://www.opensource.org/licenses/mit-license.php.
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(function(){
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this.baseX = function base (ALPHABET) {
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if (ALPHABET.length >= 255) { throw new TypeError('Alphabet too long') }
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var BASE_MAP = new Uint8Array(256)
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BASE_MAP.fill(255)
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for (var i = 0; i < ALPHABET.length; i++) {
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var x = ALPHABET.charAt(i)
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var xc = x.charCodeAt(0)
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if (BASE_MAP[xc] !== 255) { throw new TypeError(x + ' is ambiguous') }
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BASE_MAP[xc] = i
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}
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var BASE = ALPHABET.length
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var LEADER = ALPHABET.charAt(0)
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var FACTOR = Math.log(BASE) / Math.log(256) // log(BASE) / log(256), rounded up
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var iFACTOR = Math.log(256) / Math.log(BASE) // log(256) / log(BASE), rounded up
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function encode (source) {
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if (source.length === 0) { return '' }
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// Skip & count leading zeroes.
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var zeroes = 0
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var length = 0
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var pbegin = 0
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var pend = source.length
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while (pbegin !== pend && source[pbegin] === 0) {
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pbegin++
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zeroes++
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}
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// Allocate enough space in big-endian base58 representation.
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var size = ((pend - pbegin) * iFACTOR + 1) >>> 0
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var b58 = new Uint8Array(size)
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// Process the bytes.
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while (pbegin !== pend) {
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var carry = source[pbegin]
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// Apply "b58 = b58 * 256 + ch".
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var i = 0
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for (var it1 = size - 1; (carry !== 0 || i < length) && (it1 !== -1); it1--, i++) {
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carry += (256 * b58[it1]) >>> 0
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b58[it1] = (carry % BASE) >>> 0
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carry = (carry / BASE) >>> 0
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}
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if (carry !== 0) { throw new Error('Non-zero carry') }
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length = i
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pbegin++
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}
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// Skip leading zeroes in base58 result.
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var it2 = size - length
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while (it2 !== size && b58[it2] === 0) {
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it2++
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}
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// Translate the result into a string.
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var str = LEADER.repeat(zeroes)
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for (; it2 < size; ++it2) { str += ALPHABET.charAt(b58[it2]) }
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return str
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}
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function decodeUnsafe (source) {
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if (typeof source !== 'string') { throw new TypeError('Expected String') }
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if (source.length === 0) { return '' }
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var psz = 0
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// Skip leading spaces.
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if (source[psz] === ' ') { return }
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// Skip and count leading '1's.
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var zeroes = 0
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var length = 0
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while (source[psz] === LEADER) {
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zeroes++
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psz++
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}
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// Allocate enough space in big-endian base256 representation.
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var size = (((source.length - psz) * FACTOR) + 1) >>> 0 // log(58) / log(256), rounded up.
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var b256 = new Uint8Array(size)
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// Process the characters.
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while (source[psz]) {
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// Decode character
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var carry = BASE_MAP[source.charCodeAt(psz)]
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// Invalid character
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if (carry === 255) { return }
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var i = 0
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for (var it3 = size - 1; (carry !== 0 || i < length) && (it3 !== -1); it3--, i++) {
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carry += (BASE * b256[it3]) >>> 0
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b256[it3] = (carry % 256) >>> 0
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carry = (carry / 256) >>> 0
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}
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if (carry !== 0) { throw new Error('Non-zero carry') }
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length = i
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psz++
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}
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// Skip trailing spaces.
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if (source[psz] === ' ') { return }
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// Skip leading zeroes in b256.
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var it4 = size - length
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while (it4 !== size && b256[it4] === 0) {
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it4++
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}
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var vch = []
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var j = zeroes
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while (it4 !== size) {
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vch[j++] = b256[it4++]
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}
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return vch
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}
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function decode (string) {
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var buffer = decodeUnsafe(string)
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if (buffer) { return buffer }
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throw new Error('Non-base' + BASE + ' character')
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}
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return {
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encode: encode,
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decodeUnsafe: decodeUnsafe,
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decode: decode
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}
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}
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}).call(this);
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