bs58: use Buffers for internal calculation

Ported from bitcoinjs-lib, uses BigInteger precomputation as well.

lib/bs58.js

@@ -1,75 +1,73 @@
-var BigInteger = require('bigi');
-
-'use strict'
-
-module.exports.decode = decode;
-module.exports.encode = encode;
-
-var ALPHABET = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";
-var ALPHABET_BUF = new Buffer(ALPHABET)
-var LOOKUP = {};
-for (var i=0 ; i < ALPHABET.length ; ++i) {
-  LOOKUP[ALPHABET[i]] = i;
+// Base58 encoding/decoding
+// 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 assert = require('assert')
+var BigInteger = require('bigi')
+
+var ALPHABET = '123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz'
+var ALPHABET_BUF = new Buffer(ALPHABET, 'ascii')
+var ALPHABET_MAP = {}
+for(var i = 0; i < ALPHABET.length; i++) {
+  ALPHABET_MAP[ALPHABET.charAt(i)] = BigInteger.valueOf(i)
 }
+var BASE = new BigInteger('58')
 
-var BASE = 58;
-var base = BigInteger.valueOf(BASE);
-
-
-function encode (input) {
-  var bi = BigInteger.fromBuffer(input)
-  var result = new Buffer(input.length << 1)
+function encode(buffer) {
+  var bi = BigInteger.fromBuffer(buffer)
+  var result = new Buffer(buffer.length << 1)
 
   var i = result.length - 1
-  while (bi.compareTo(BigInteger.ZERO) > 0) {
-    var remainder = bi.mod(base)
-    bi = bi.divide(base)
+  while (bi.signum() > 0) {
+    var remainder = bi.mod(BASE)
+    bi = bi.divide(BASE)
 
     result[i] = ALPHABET_BUF[remainder.intValue()]
     i--
   }
 
   // deal with leading zeros
   var j = 0
-  while (input[j] === 0) {
+  while (buffer[j] === 0) {
     result[i] = ALPHABET_BUF[0]
     j++
     i--
   }
 
-  return result.slice(i + 1, result.length).toString()
+  return result.slice(i + 1, result.length).toString('ascii')
 }
 
+function decode(string) {
+  if (string.length === 0) return new Buffer(0)
 
-function decode (input) {
-  var num = BigInteger.valueOf(0);
-  var leadingZero = 0;
-  var seenOther = false;
-  for (var i = 0; i < input.length ; ++i) {
-    var ch = input[i];
-    var p = LOOKUP[ch];
+  var num = BigInteger.ZERO
 
-    // if we encounter an invalid character, decoding fails
-    if (p === undefined) {
-      throw new Error('invalid base58 string: ' + input);
-    }
+  for (var i = 0; i < string.length; i++) {
+    num = num.multiply(BASE)
 
-    num = num.multiply(base).add(BigInteger.valueOf(p));
+    var figure = ALPHABET_MAP[string.charAt(i)]
+    assert.notEqual(figure, undefined, 'Non-base58 character')
 
-    if (ch == ALPHABET[0] && !seenOther) {
-      ++leadingZero;
-    }
-    else {
-      seenOther = true;
-    }
+    num = num.add(figure)
   }
 
-  var bytes = num.toByteArrayUnsigned();
-
-  // remove leading zeros
-  while (leadingZero-- > 0) {
-    bytes.unshift(0);
+  // deal with leading zeros
+  var j = 0
+  while ((j < string.length) && (string[j] === ALPHABET[0])) {
+    j++
   }
 
-  return new Buffer(bytes);
+  var buffer = num.toBuffer()
+  var leadingZeros = new Buffer(j)
+  leadingZeros.fill(0)
+
+  return Buffer.concat([leadingZeros, buffer])
+}
+
+module.exports = {
+  encode: encode,
+  decode: decode
 }

test/bs58.js

@@ -27,7 +27,7 @@ describe('base58', function() {
       it('throws on ' + f.description, function() {
         assert.throws(function() {
           base58.decode(f.string)
-        }, /invalid base58 string/)
+        }, /Non-base58 character/)
       })
     })
   })