convert: use Buffer internally and remove unused functions

src/convert.js

@@ -2,29 +2,28 @@ var assert = require('assert')
 var Crypto = require('crypto-js')
 var WordArray = Crypto.lib.WordArray
 
-function bufferToWords(buffer) {
+function bufferToWordArray(buffer) {
-  assert(Buffer.isBuffer(buffer), 'Expected Buffer, got' + buffer)
+  assert(Buffer.isBuffer(buffer), 'Expected Buffer, got', buffer)
+
   var words = []
   for (var i = 0, b = 0; i < buffer.length; i++, b += 8) {
     words[b >>> 5] |= buffer[i] << (24 - b % 32)
   }
-  return words
-}
 
-function wordsToBytes(words) {
+  return new WordArray.init(words, buffer.length)
-  var bytes = []
-  for (var b = 0; b < words.length * 32; b += 8) {
-    bytes.push((words[b >>> 5] >>> (24 - b % 32)) & 0xFF)
-  }
-  return bytes
-}
-
-function bufferToWordArray(buffer) {
-  return new WordArray.init(bufferToWords(buffer), buffer.length)
 }
 
 function wordArrayToBuffer(wordArray) {
-  return new Buffer(wordsToBytes(wordArray.words))
+  assert(Array.isArray(wordArray.words), 'Expected WordArray, got' + wordArray)
+
+  var words = wordArray.words
+  var buffer = new Buffer(words.length * 4)
+
+  words.forEach(function(value, i) {
+    buffer.writeInt32BE(value & -1, i * 4)
+  })
+
+  return buffer
 }
 
 function reverseEndian(hex) {
@@ -35,8 +34,6 @@ function reverseEndian(hex) {
 }
 
 module.exports = {
-  bufferToWords: bufferToWords,
-  wordsToBytes: wordsToBytes,
   bufferToWordArray: bufferToWordArray,
   wordArrayToBuffer: wordArrayToBuffer,
   reverseEndian: reverseEndian