var keyStr = "ABCDEFGHIJKLMNOP" +
             "QRSTUVWXYZabcdef" +
             "ghijklmnopqrstuv" +
             "wxyz0123456789+/" +
             "=";

function encode64(input) {
   input = unicodetoBytes(input);
   var output = "";
   var chr1, chr2, chr3 = "";
   var enc1, enc2, enc3, enc4 = "";
   var i = 0;

   do {
      chr1 = input[i++];
      chr2 = input[i++];
      chr3 = input[i++];

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

      if (isNaN(chr2)) {
         enc3 = enc4 = 64;
      } else if (isNaN(chr3)) {
         enc4 = 64;
      }

      output = output +
         keyStr.charAt(enc1) +
         keyStr.charAt(enc2) +
         keyStr.charAt(enc3) +
         keyStr.charAt(enc4);
      chr1 = chr2 = chr3 = "";
      enc1 = enc2 = enc3 = enc4 = "";
   } while (i < input.length);

   return output;
}

function decode64(input) {
   var output = "";
   var chr1, chr2, chr3 = "";
   var enc1, enc2, enc3, enc4 = "";
   var i = 0;

   // remove all characters that are not A-Z, a-z, 0-9, +, /, or =
   var base64test = /[^A-Za-z0-9\+\/\=]/g;
   if (base64test.exec(input)) {
      alert("There were invalid base64 characters in the input text.\n" +
            "Valid base64 characters are A-Z, a-z, 0-9, '+', '/', and '='\n" +
            "Expect errors in decoding.");
   }
   input = input.replace(/[^A-Za-z0-9\+\/\=]/g, "");
    output=new Array();
   do {
      enc1 = keyStr.indexOf(input.charAt(i++));
      enc2 = keyStr.indexOf(input.charAt(i++));
      enc3 = keyStr.indexOf(input.charAt(i++));
      enc4 = keyStr.indexOf(input.charAt(i++));

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

      output.push(chr1);
      if (enc3 != 64) {
         output.push(chr2);
      }
      if (enc4 != 64) {
         output.push(chr3);
      }

      chr1 = chr2 = chr3 = "";
      enc1 = enc2 = enc3 = enc4 = "";

   } while (i < input.length);
   return bytesToUnicode(output);
}

  function unicodetoBytes(s)
   {
      var result=new Array();
      if(s==null || s=="") return result;
      result.push(255); // add "FE" to head
      result.push(254);
      for(var i=0;i<s.length;i++)
      {
        var c=s.charCodeAt(i).toString(16);
        if(c.length==1) i="000"+c;
        else if(c.length==2) c="00"+c;
        else if(c.length==3) c="0"+c;
        var var1=parseInt( c.substring(2),16);
        var var2=parseInt( c.substring(0,2),16);
        result.push( var1);
        result.push(var2) ;
      }
      return result;
   }

   function bytesToUnicode(bs)
   {
     var result="";
      var offset=0;
      if(bs.length>=2 && bs[0]==255 && bs[1]==254) offset=2;  // delete "FE"
      for(var i=offset;i<bs.length;i+=2)
      {
            var code=bs[i]+(bs[i+1]<<8);
            result+=String.fromCharCode(code);
      }
      return result;
   }