function Decoder(input) {
	this.input = atob(input);
	this.cache = 0;
	this.size = 0;
}

Decoder.prototype.pop = function() {
	if(this.size < 1) {
		if(this.input.length < 1) {
			return null;
		} else {
			this.cache = this.input.charCodeAt(0);
			this.size = 8;
			this.input = this.input.slice(1);
		}
	}
	this.size--;
	var wasFirstBitOne = this.cache > 0x7f;
	this.cache = (2*this.cache) & 0xff;
	return wasFirstBitOne ? 1 : 0;
};

Decoder.prototype.variableLength3 = function() {
	if(this.pop() == 1) {
		return this.pop() + 1;
	} else {
		return 0;
	}
};

Decoder.prototype.variableLength6 = function() {
	if(this.pop() == 1) {
		return 2 + this.int(2);
	} else {
		return this.pop();
	}
};

Decoder.prototype.int = function(size) {
	var result = 0;
	for(var i = 0; i < size; i++) {
		result = 2*result + this.pop();
	}
	return result;
};

return {
	make: function(input) {return new Decoder(input);}
};