Offset(h)00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F
 
00000000 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F     ...............
00000010 19 84 74 68 69 73 20 69 73 20 61 20 74 65 73 74     ..this is a test

   AAECAwQFBgcICQoLDA0ODxmEdGhpcyBpcyBhIHRlc3Q=

    var data = new Base64Native("AAECAwQFBgcICQoLDA0ODxmEdGhpcyBpcyBhIHRlc3Q=");
    console.log(data.length); // outputs 32;
    console.log(data.readBoolean()); // outputs false; - reads a byte and casts it to a boolean value
    console.log(data.readByte()); // outputs 1;
    console.log(data.readWord()); // outputs 515; - reads a 16 bit number
    console.log(data.readInt()); // outputs 67438087; - reads a 32 bit number
    console.log(data.seek(28)); // moves the pointer to byte 28 (0x1C)
    console.log(data.readString(data.bytesAvailable())); // outputs 'test'; reads a string from position 28 to the end of the file

var Base64Native = function(data) {
    var keyStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=",
        length = data.length - (data.length / 4) - (data.split(/=/g).length - 1),
        ptr = 0;
 
    function keyIdx(idx) {
        return keyStr.indexOf(data.charAt(idx));
    }
 
    function readByte() {
        if (!(length - ptr)) { throw Error('End of stream!'); }
        var blockIndex = Math.floor(ptr / 3) * 4, subIndex = ptr++ % 3, ptrChr = blockIndex + subIndex;
        return !subIndex && ((keyIdx(ptrChr) < < 2) | (keyIdx(ptrChr + 1) >> 4)) || subIndex === 1 &&
               (((keyIdx(ptrChr) & 15) < < 4) | (keyIdx(ptrChr + 1) >> 2)) || ((keyIdx(ptrChr) & 3)  < < 6) |  keyIdx(ptrChr + 1);
    }
 
    return {
        /* Returns the available bytes left in the file to read */
        bytesAvailable : function() {
            return length - ptr;
        },
        /* Reads and returns a 8 bit number and increments the position of the index accordingly */
        readByte : function() {
            return readByte();
        },
        /* Reads and returns a 32 bit number and increments the position of the index accordingly */
        readInt : function() {
            return (readByte() << 24) | (readByte() << 16) | (readByte() << 8) | readByte();
        },
        /* Reads 1 byte and returns the boolean value of it and increments the position of the index accordingly */
        readBoolean : function() {
            return Boolean(readByte());
        },
        /* Reads and returns a 16 bit number and increments the position of the index accordingly */
        readWord : function() {
            return readByte() << 8 | readByte()
        },
        /* Reads and returns a string of length 'len' and increments the position of the index accordingly */
        readString : function(/*String*/len) {
            var data = '';
            for (var i = 0; i < len; i++) {
                data += String.fromCharCode(readByte());
            }
            return data;
        },
        /* Moves the index into the file at location newpos */
        seek : function(newpos) {
            ptr = newpos;
        },
        /* Returns the position of the index in the file */
        position : function() {
            return ptr;
        },
        /* The length of the data */
        length : length
    };
};