(function() {
  var base64map
      = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/',

  crypt = {
    // Bit-wise rotation left
    rotl: function(n, b) {
      return (n << b) | (n >>> (32 - b));
    },

    // Bit-wise rotation right
    rotr: function(n, b) {
      return (n << (32 - b)) | (n >>> b);
    },

    // Swap big-endian to little-endian and vice versa
    endian: function(n) {
      // If number given, swap endian
      if (n.constructor == Number) {
        return crypt.rotl(n, 8) & 0x00FF00FF | crypt.rotl(n, 24) & 0xFF00FF00;
      }

      // Else, assume array and swap all items
      for (var i = 0; i < n.length; i++)
        n[i] = crypt.endian(n[i]);
      return n;
    },

    // Generate an array of any length of random bytes
    randomBytes: function(n) {
      for (var bytes = []; n > 0; n--)
        bytes.push(Math.floor(Math.random() * 256));
      return bytes;
    },

    // Convert a byte array to big-endian 32-bit words
    bytesToWords: function(bytes) {
      for (var words = [], i = 0, b = 0; i < bytes.length; i++, b += 8)
        words[b >>> 5] |= bytes[i] << (24 - b % 32);
      return words;
    },

    // Convert big-endian 32-bit words to a byte array
    wordsToBytes: function(words) {
      for (var bytes = [], b = 0; b < words.length * 32; b += 8)
        bytes.push((words[b >>> 5] >>> (24 - b % 32)) & 0xFF);
      return bytes;
    },

    // Convert a byte array to a hex string
    bytesToHex: function(bytes) {
      for (var hex = [], i = 0; i < bytes.length; i++) {
        hex.push((bytes[i] >>> 4).toString(16));
        hex.push((bytes[i] & 0xF).toString(16));
      }
      return hex.join('');
    },

    // Convert a hex string to a byte array
    hexToBytes: function(hex) {
      for (var bytes = [], c = 0; c < hex.length; c += 2)
        bytes.push(parseInt(hex.substr(c, 2), 16));
      return bytes;
    },

    // Convert a byte array to a base-64 string
    bytesToBase64: function(bytes) {
      for (var base64 = [], i = 0; i < bytes.length; i += 3) {
        var triplet = (bytes[i] << 16) | (bytes[i + 1] << 8) | bytes[i + 2];
        for (var j = 0; j < 4; j++)
          if (i * 8 + j * 6 <= bytes.length * 8)
            base64.push(base64map.charAt((triplet >>> 6 * (3 - j)) & 0x3F));
          else
            base64.push('=');
      }
      return base64.join('');
    },

    // Convert a base-64 string to a byte array
    base64ToBytes: function(base64) {
      // Remove non-base-64 characters
      base64 = base64.replace(/[^A-Z0-9+\/]/ig, '');

      for (var bytes = [], i = 0, imod4 = 0; i < base64.length;
          imod4 = ++i % 4) {
        if (imod4 == 0) continue;
        bytes.push(((base64map.indexOf(base64.charAt(i - 1))
            & (Math.pow(2, -2 * imod4 + 8) - 1)) << (imod4 * 2))
            | (base64map.indexOf(base64.charAt(i)) >>> (6 - imod4 * 2)));
      }
      return bytes;
    }
  };

  module.exports = crypt;
})();