var ua = navigator.userAgent.toLowerCase();
if (ua.indexOf(" chrome/") >= 0 || ua.indexOf(" firefox/") >= 0 || ua.indexOf(' gecko/') >= 0) {
    var StringMaker = function () {
        this.str = "";
        this.length = 0;
        this.append = function (s) {
            this.str += s;
            this.length += s.length;
        }
        this.prepend = function (s) {
            this.str = s + this.str;
            this.length += s.length;
        }
        this.toString = function () {
            return this.str;
        }
    }
} else {
    var StringMaker = function () {
        this.parts = [];
        this.length = 0;
        this.append = function (s) {
            this.parts.push(s);
            this.length += s.length;
        }
        this.prepend = function (s) {
            this.parts.unshift(s);
            this.length += s.length;
        }
        this.toString = function () {
            return this.parts.join('');
        }
    }
}

var keyStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";

function encode64(input) {
    var output = new StringMaker();
    var chr1, chr2, chr3;
    var 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 (isNaN(chr2)) {
            enc3 = enc4 = 64;
        } else if (isNaN(chr3)) {
            enc4 = 64;
        }

        output.append(keyStr.charAt(enc1) + keyStr.charAt(enc2) + keyStr.charAt(enc3) + keyStr.charAt(enc4));
   }

   return output.toString();
}

function decode64(input) {
    var output = new StringMaker();
    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 =
    input = input.replace(/[^A-Za-z0-9\+\/\=]/g, "");

    while (i < input.length) {
        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.append(String.fromCharCode(chr1));

        if (enc3 != 64) {
            output.append(String.fromCharCode(chr2));
        }
        if (enc4 != 64) {
            output.append(String.fromCharCode(chr3));
        }
    }

    return output.toString();
}