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

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

  do {
	 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 (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;
}