// http://ntt.cc/2008/01/19/base64-encoder-decoder-with-javascript.html

// window.atob and window.btoa

(function (window) {

	var keyStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
	
	window.btoa || (window.btoa = function encode64(input) {
		input = escape(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;
	});
	
	window.atob || (window.atob = function(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, "");
		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 = output + String.fromCharCode(chr1);
			if (enc3 != 64) {
				output = output + String.fromCharCode(chr2);
			}
			if (enc4 != 64) {
				output = output + String.fromCharCode(chr3);
			}
			chr1 = chr2 = chr3 = "";
			enc1 = enc2 = enc3 = enc4 = "";
		} while (i < input.length);
		return unescape(output);
	});

}(this));