/**
 *  Base64.js - Base64 encode / decode
 *
  Synopsis:
   No dependencies.

   <script src='/js/Base64.js'></script>
   <script>

      var string = 'test string';
      var encoded = Base64.encode(string);
      var decoded = Base64.decode(encoded);
      // string == decoded

   </script>
 */

var Base64 = {

    // Store lookup tables for b64 characters
    _b64chars : "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=",
    _b64inv : new Object,

    // Private init function to build inverse map
    _init_b64inv : function() {
        if (!this._b64inv['A']) {
            var c = this._b64chars;
            for (var i=0; i < c.length; i++){
                this._b64inv[c[i]] = i;
            }
        }
    },


    // public method for encoding
    encode : function (input) {
        var output = "";
        var chr1, chr2, chr3, enc1, enc2, enc3, enc4;
        var i = 0;

        while (i < input.length) {

            chr1 = input.charCodeAt(i++);
            chr2 = input.charCodeAt(i++);
            chr3 = input.charCodeAt(i++);

            enc1 = chr1 >> 2;
            enc2 = ((chr1 & 3) << 4) | (chr2 >> 4);
            enc3 = ((chr2 & 15) << 2) | (chr3 >> 6);
            enc4 = chr3 & 63;

            // If any of the encodings go out of range, replace with padding
            if (isNaN(chr2)) {
                enc3 = enc4 = 64;
            } else if (isNaN(chr3)) {
                enc4 = 64;
            }

            output = output +
            this._b64chars.charAt(enc1) + this._b64chars.charAt(enc2) +
            this._b64chars.charAt(enc3) + this._b64chars.charAt(enc4);

        }

        return output;
    },

    // public method for decoding
    decode : function (input) {
        this._init_b64inv();

        var output = "";
        var chr1, chr2, chr3;
        var enc1, enc2, enc3, enc4;
        var i = 0;

        // Scrub non-b64 characters
        input = input.replace(/[^A-Za-z0-9\+\/\=]/g, "");

        while (i < input.length) {

            enc1 = this._b64inv[input.charAt(i++)];
            enc2 = this._b64inv[input.charAt(i++)];
            enc3 = this._b64inv[input.charAt(i++)];
            enc4 = this._b64inv[input.charAt(i++)];

            chr1 = (enc1 << 2) | (enc2 >> 4);
            chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);
            chr3 = ((enc3 & 3) << 6) | enc4;

            // Alwyas use first character decoded
            output = output + String.fromCharCode(chr1);

            // Only use remaining chars if the encoding wasn't padding
            if (enc3 != 64) {
                output = output + String.fromCharCode(chr2);
            }
            if (enc4 != 64) {
                output = output + String.fromCharCode(chr3);
            }

        }

        return output;

    }

};