73 lines
1.7 KiB
JavaScript
73 lines
1.7 KiB
JavaScript
// Base58 encoding/decoding
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// Originally written by Mike Hearn for BitcoinJ
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// Copyright (c) 2011 Google Inc
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// Ported to JavaScript by Stefan Thomas
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// Merged Buffer refactorings from base58-native by Stephen Pair
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// Copyright (c) 2013 BitPay Inc
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var assert = require('assert')
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var BigInteger = require('bigi')
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var ALPHABET = '123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz'
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var ALPHABET_BUF = new Buffer(ALPHABET, 'ascii')
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var ALPHABET_MAP = {}
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for(var i = 0; i < ALPHABET.length; i++) {
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ALPHABET_MAP[ALPHABET[i]] = BigInteger.valueOf(i)
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}
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var BASE = BigInteger.valueOf(58)
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function encode(buffer) {
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var bi = BigInteger.fromBuffer(buffer)
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var result = new Buffer(buffer.length << 1)
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var i = result.length - 1
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while (bi.compareTo(BigInteger.ZERO) > 0) {
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var remainder = bi.mod(BASE)
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bi = bi.divide(BASE)
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result[i] = ALPHABET_BUF[remainder.intValue()]
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i--
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}
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// deal with leading zeros
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var j = 0
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while (buffer[j] === 0) {
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result[i] = ALPHABET_BUF[0]
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j++
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i--
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}
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return result.slice(i + 1, result.length).toString('ascii')
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}
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function decode(string) {
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if (string.length === 0) return new Buffer(0)
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var num = BigInteger.ZERO.clone()
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for (var i = 0; i < string.length; i++) {
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num = num.multiply(BASE)
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var figure = ALPHABET_MAP[string.charAt(i)]
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assert.notEqual(figure, undefined, 'Non-base58 character')
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num = num.add(figure)
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}
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// deal with leading zeros
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var i = 0
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while ((i < string.length) && (string[i] === ALPHABET[0])) {
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i++
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}
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var buffer = num.toBuffer()
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var leadz = new Buffer(i)
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leadz.fill(0)
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return Buffer.concat([leadz, buffer])
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}
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module.exports = {
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encode: encode,
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decode: decode
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}
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