Isolates Base58Check encoding from Base58 code/tests

src/base58.js

@@ -1,66 +1,65 @@
-// https://en.bitcoin.it/wiki/Base58Check_encoding
+// Base58 encoding/decoding
+// Originally written by Mike Hearn for BitcoinJ
+// Copyright (c) 2011 Google Inc
+// Ported to JavaScript by Stefan Thomas
 
 var BigInteger = require('./jsbn/jsbn')
-var Crypto = require('crypto-js')
-var convert = require('./convert')
-var SHA256 = Crypto.SHA256
 
+// FIXME: ? This is a Base58Check alphabet
 var alphabet = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"
 var base = BigInteger.valueOf(58)
 
-var positions = {}
+var alphabetMap = {}
 for (var i=0; i<alphabet.length; ++i) {
-  positions[alphabet[i]] = i
+  var chr = alphabet[i]
+  alphabetMap[chr] = BigInteger.valueOf(i)
 }
 
-// Convert a byte array to a base58-encoded string.
-// Written by Mike Hearn for BitcoinJ.
-// Copyright (c) 2011 Google Inc.
-// Ported to JavaScript by Stefan Thomas.
-function encode(input) {
-  var bi = BigInteger.fromByteArrayUnsigned(input)
+// encode a byte array into a base58 encoded String
+// @return String
+function encode(buffer) {
+  var bi = BigInteger.fromByteArrayUnsigned(buffer)
   var chars = []
 
   while (bi.compareTo(base) >= 0) {
     var mod = bi.mod(base)
-    chars.push(alphabet[mod.intValue()])
     bi = bi.subtract(mod).divide(base)
+
+    chars.push(alphabet[mod.intValue()])
   }
 
   chars.push(alphabet[bi.intValue()])
 
   // Convert leading zeros too.
-  for (var i=0; i<input.length; i++) {
-    if (input[i] == 0x00) {
-      chars.push(alphabet[0])
-    } else break
+  for (var i=0; i<buffer.length; i++) {
+    if (buffer[i] !== 0x00) break
+
+    chars.push(alphabet[0])
   }
 
   return chars.reverse().join('')
 }
 
-// decode a base58 string into a byte array
-// input should be a base58 encoded string
+// decode a base58 encoded String into a byte array
 // @return Array
-function decode(input) {
-  var base = BigInteger.valueOf(58)
-
-  var length = input.length
+function decode(str) {
   var num = BigInteger.valueOf(0)
+
   var leading_zero = 0
   var seen_other = false
-  for (var i=0; i<length; ++i) {
-    var chr = input[i]
-    var p = positions[chr]
+
+  for (var i=0; i<str.length; ++i) {
+    var chr = str[i]
+    var bi = alphabetMap[chr]
 
     // if we encounter an invalid character, decoding fails
-    if (p === undefined) {
-      throw new Error('invalid base58 string: ' + input)
+    if (bi === undefined) {
+      throw new Error('invalid base58 string: ' + str)
     }
 
-    num = num.multiply(base).add(BigInteger.valueOf(p))
+    num = num.multiply(base).add(bi)
 
-    if (chr == '1' && !seen_other) {
+    if (chr === '1' && !seen_other) {
       ++leading_zero
     } else {
       seen_other = true
@@ -74,41 +73,10 @@ function decode(input) {
     bytes.unshift(0)
   }
 
-  return bytes
-}
-
-function checkEncode(input, vbyte) {
-  vbyte = vbyte || 0
-
-  var front = [vbyte].concat(input)
-  return encode(front.concat(getChecksum(front)))
-}
-
-function checkDecode(input) {
-  var bytes = decode(input),
-  front = bytes.slice(0, bytes.length-4),
-  back = bytes.slice(bytes.length-4)
-
-  var checksum = getChecksum(front)
-
-  if ("" + checksum != "" + back) {
-    throw new Error("Checksum failed")
-  }
-
-  var o = front.slice(1)
-  o.version = front[0]
-  return o
-}
-
-function getChecksum(bytes) {
-  var wordArray = convert.bytesToWordArray(bytes)
-  return convert.hexToBytes(SHA256(SHA256(wordArray)).toString()).slice(0, 4)
+  return new Buffer(bytes)
 }
 
 module.exports = {
   encode: encode,
-  decode: decode,
-  checkEncode: checkEncode,
-  checkDecode: checkDecode,
-  getChecksum: getChecksum
+  decode: decode
 }

src/base58check.js

@@ -0,0 +1,53 @@
+// https://en.bitcoin.it/wiki/Base58Check_encoding
+var assert = require('assert')
+var base58 = require('./base58')
+var crypto = require('crypto')
+
+function sha256(buf) {
+  var hash = crypto.createHash('sha256')
+  hash.update(buf)
+
+  return hash.digest()
+}
+
+// Encode a buffer as a base58-check-encoded string
+function encode(buffer, version) {
+  version = version || 0
+
+  // FIXME: `new Buffer(buffer)` is unnecessary if input is a Buffer
+  var version = new Buffer([version])
+  var payload = new Buffer(buffer)
+
+  var message = Buffer.concat([version, payload])
+  var checksum = sha256(sha256(message)).slice(0, 4)
+
+  return base58.encode(Buffer.concat([
+    message,
+    checksum
+  ]))
+}
+
+// Decode a base58-check-encoded string to a buffer
+function decode(string) {
+  var buffer = base58.decode(string)
+
+  var message = buffer.slice(0, -4)
+  var checksum = buffer.slice(-4)
+  var newChecksum = sha256(sha256(message)).slice(0, 4)
+
+  assert.deepEqual(newChecksum, checksum)
+
+  var version = message.readUInt8(0)
+  var payload = message.slice(1)
+
+  return {
+    version: version,
+    payload: payload,
+    checksum: checksum
+  }
+}
+
+module.exports = {
+  encode: encode,
+  decode: decode
+}

src/index.js

@@ -21,5 +21,6 @@ module.exports = {
   ecdsa: require('./ecdsa'),
   HDWallet: require('./hdwallet.js'),
   base58: require('./base58'),
+  base58check: require('./base58check'),
   convert: require('./convert')
 }