minecraft.js/lib/uint4Array.js

Minecraft data serialization/deserialization and networking

/** @constructor */
var Uint4Array = module.exports = function(buffer, byteOffset, length) {
	this.buffer = buffer;
	this.byteOffset = byteOffset || 0;
	this.length = length || this.buffer.byteLength;
	
	this.view = new Uint8Array(this.buffer, this.byteOffset, Math.ceil(this.length / 2));
	
	if(this.length > this.buffer.byteLength * 2) {
		//TODO: throw exception
	}
};

Uint4Array.prototype.get = function(index) {
	var value = this.view[Math.floor(index / 2)];
	if(index % 2 == 0) {
		value = value >>> 4;
	} else {
		value = (value << 28) >>> 28;
	}
	return value;
};

Uint4Array.prototype.set = function(index, value) {
	value = Math.floor(value);
	value = (value << 28) >>> 28;
	
	if(index % 2 == 0) {
		value = (value << 4) + this.get(index + 1);
	} else  {
		value = (this.get(index - 1) << 4) + value;
	}
	this.view[Math.floor(index / 2)] = value;
	
	return this;
};