Merges Buffer refactorings from base58-native by Stephen Pair

Author: dcousens

src/base58.js

@@ -2,78 +2,65 @@
 // Originally written by Mike Hearn for BitcoinJ
 // Copyright (c) 2011 Google Inc
 // Ported to JavaScript by Stefan Thomas
+// Merged Buffer refactorings from base58-native by Stephen Pair
+// Copyright (c) 2013 BitPay Inc
 
 var BigInteger = require('./jsbn/jsbn')
 
-// FIXME: ? This is a Base58Check alphabet
-var alphabet = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"
-var base = BigInteger.valueOf(58)
-
-var alphabetMap = {}
-for (var i=0; i<alphabet.length; ++i) {
- var chr = alphabet[i]
- alphabetMap[chr] = BigInteger.valueOf(i)
+var ALPHABET = '123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz'
+var ALPHABET_BUF = new Buffer(ALPHABET, 'ascii')
+var ALPHABET_MAP = {}
+for(var i = 0; i < ALPHABET.length; i++) {
+ ALPHABET_MAP[ALPHABET[i]] = BigInteger.valueOf(i)
 }
+var BASE = BigInteger.valueOf(58)
 
-// encode a byte array into a base58 encoded String
-// @return String
 function encode(buffer) {
  var bi = BigInteger.fromByteArrayUnsigned(buffer)
- var chars = []
+ var result = new Buffer(buffer.length << 1)
 
- while (bi.compareTo(base) >= 0) {
- var mod = bi.mod(base)
- bi = bi.subtract(mod).divide(base)
+ var i = result.length - 1
+ while (bi.compareTo(BigInteger.ZERO) > 0) {
+ var remainder = bi.mod(BASE)
+ bi = bi.divide(BASE)
 
- chars.push(alphabet[mod.intValue()])
+ result[i] = ALPHABET_BUF[remainder.intValue()]
+ i--
  }
 
- chars.push(alphabet[bi.intValue()])
-
- // Convert leading zeros too.
- for (var i=0; i<buffer.length; i++) {
- if (buffer[i] !== 0x00) break
-
- chars.push(alphabet[0])
+ // deal with leading zeros
+ var j = 0
+ while (buffer[j] === 0) {
+ result[i] = ALPHABET_BUF[0]
+ j++
+ i--
  }
 
- return chars.reverse().join('')
+ return result.slice(i + 1, result.length).toString('ascii')
 }
 
-// decode a base58 encoded String into a byte array
-// @return Array
-function decode(str) {
- var num = BigInteger.valueOf(0)
-
- var leading_zero = 0
- var seen_other = false
+function decode(string) {
+ if (string.length === 0) return new Buffer(0)
 
- for (var i=0; i<str.length; ++i) {
- var chr = str[i]
- var bi = alphabetMap[chr]
+ var num = BigInteger.ZERO.clone()
 
- // if we encounter an invalid character, decoding fails
- if (bi === undefined) {
- throw new Error('invalid base58 string: ' + str)
- }
-
- num = num.multiply(base).add(bi)
-
- if (chr === '1' && !seen_other) {
- ++leading_zero
- } else {
- seen_other = true
- }
+ for (var i = 0; i < string.length; i++) {
+ num = num.multiply(BASE)
+ num = num.add(ALPHABET_MAP[string.charAt(i)])
  }
 
- var bytes = num.toByteArrayUnsigned()
-
- // remove leading zeros
- while (leading_zero-- > 0) {
- bytes.unshift(0)
+ // deal with leading zeros
+ var i = 0
+ while ((i < string.length) && (string[i] === ALPHABET[0])) {
+ i++
  }
 
- return new Buffer(bytes)
+ // FIXME: If BigInteger supported buffers, this could be a copy
+ var buffer = new Buffer(num.toByteArrayUnsigned())
+ var padding = new Buffer(i)
+ padding.fill(0)
+
+ return Buffer.concat([padding, buffer])
 }
 
 module.exports = {