script/base64.js

/* Copyright (C) 1999 Masanao Izumo <iz@onicos.co.jp>
 * Version: 1.0
 * LastModified: Dec 25 1999
 * This library is free.  You can redistribute it and/or modify it.
 */
 /* Modified by Chris Anderson to not use CommonJS */
 /* Modified by Dan Webb not to require Narwhal's binary library */

var Base64 = {};
(function(exports) {
  
  var encodeChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  var decodeChars = [
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,
      52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1,
      -1,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,
      15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,
      -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
      41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1
  ];

  exports.encode = function (str) {
      var out, i, length;
      var c1, c2, c3;

      length = len(str);
      i = 0;
      out = [];
      while(i < length) {
          c1 = str.charCodeAt(i++) & 0xff;
          if(i == length)
          {
              out.push(encodeChars.charCodeAt(c1 >> 2));
              out.push(encodeChars.charCodeAt((c1 & 0x3) << 4));
              out.push("=".charCodeAt(0));
              out.push("=".charCodeAt(0));
              break;
          }
          c2 = str.charCodeAt(i++);
          if(i == length)
          {
              out.push(encodeChars.charCodeAt(c1 >> 2));
              out.push(encodeChars.charCodeAt(((c1 & 0x3)<< 4) | ((c2 & 0xF0) >> 4)));
              out.push(encodeChars.charCodeAt((c2 & 0xF) << 2));
              out.push("=".charCodeAt(0));
              break;
          }
          c3 = str.charCodeAt(i++);
          out.push(encodeChars.charCodeAt(c1 >> 2));
          out.push(encodeChars.charCodeAt(((c1 & 0x3)<< 4) | ((c2 & 0xF0) >> 4)));
          out.push(encodeChars.charCodeAt(((c2 & 0xF) << 2) | ((c3 & 0xC0) >>6)));
          out.push(encodeChars.charCodeAt(c3 & 0x3F));
      }

      var str = ""; 
      out.forEach(function(chr) { str += String.fromCharCode(chr) });
      return str;
  };

  exports.decode = function (str) {
      var c1, c2, c3, c4;
      var i, length, out;

      length = len(str);
      i = 0;
      out = [];
      while(i < length) {
          /* c1 */
          do {
              c1 = decodeChars[str.charCodeAt(i++) & 0xff];
          } while(i < length && c1 == -1);
          if(c1 == -1)
              break;

          /* c2 */
          do {
              c2 = decodeChars[str.charCodeAt(i++) & 0xff];
          } while(i < length && c2 == -1);
          if(c2 == -1)
              break;

          out.push(String.fromCharCode((c1 << 2) | ((c2 & 0x30) >> 4)));

          /* c3 */
          do {
              c3 = str.charCodeAt(i++) & 0xff;
              if(c3 == 61)
                  return out.join('');
              c3 = decodeChars[c3];
          } while(i < length && c3 == -1);
          if(c3 == -1)
              break;

          out.push(String.fromCharCode(((c2 & 0xF) << 4) | ((c3 & 0x3C) >> 2)));

          /* c4 */
          do {
              c4 = str.charCodeAt(i++) & 0xff;
              if(c4 == 61)
                  return out.join('');
              c4 = decodeChars[c4];
          } while(i < length && c4 == -1);

          if(c4 == -1)
              break;

          out.push(String.fromCharCode(((c3 & 0x03) << 6) | c4));
      }

      return out.join('');
  };

  var len = function (object) {
      if (object.length !== undefined) {
          return object.length;
      } else if (object.getLength !== undefined) {
          return object.getLength();
      } else {
          return undefined;
      }
  };
})(Base64);