参照protobuf，将json数据转换成二进制在网络中传输。

json数据格式在网络中传输需要的数据比二进制庞大太多，我们可以省去key，外加将数字不需要编码成字符串，直接二进制编码就OK。

pack : 将json压包，unpack解包成json。

var Struct = module.exports = {};

Struct.TYPE = {
	int8:1,
	int16:2,
	int32:3,
	uint8:4,	
	uint16:5,
	uint32:7,
	string:8,
	object:9,
	aint8:10,
	aint16:11,
	aint32:12,
	auint8:13,
	auint16:14,
	auint32:15,
	aobject:16
};


//
Struct.unpack = function(proto, buf) {
	var _unpack = function(proto, buf, pos) {
		var p = {};
		var ret;
		var length;

		for (var k in proto) {
			var type = proto[k][0];
			if (typeof type == 'object') {
				var json = type;
				type = 'object';
			}
			if (proto[k].length == 2 && proto[k][1] == 'array') {
				type = 'a' + type;
			}
			var value = [];
			switch(Struct.TYPE[type]) {
				case Struct.TYPE.int8:
					p[k] = buf.readInt8(pos);
					pos += 1;
					break;
				case Struct.TYPE.int16:
					p[k] = buf.readInt16BE(pos);
					pos += 2;
					break;
				case Struct.TYPE.int32:
					p[k] = buf.readInt32BE(pos);
					pos += 4;
					break;
				case Struct.TYPE.uint8:
					p[k] = buf.readUInt8(pos);
					pos += 1;
					break;
				case Struct.TYPE.uint16:
					p[k] = buf.readUInt16BE(pos);
					pos += 2;
					break;
				case Struct.TYPE.uint32:
					p[k] = buf.readUInt32BE(pos);
					pos += 4;
					break;
				case Struct.TYPE.string:
					ret = getLen(buf,pos);
					pos = ret[1];
					p[k] = buf.toString('utf-8',pos, pos + ret[0]);
					pos += ret[0];
					break;
				case Struct.TYPE.object:
					ret = _unpack(json, buf, pos);
					p[k] = ret[0];
					pos = ret[1];
					break;
				case Struct.TYPE.aint8:
					ret = getLen(buf,pos);
					length = ret[0];
					pos = ret[1];
					for (var i=0; i < length; i++) {
						value.push(buf.readInt8(pos));
						pos += 1;
					}
					p[k] = value;
					break;
				case Struct.TYPE.aint16:
					ret = getLen(buf,pos);
					length = ret[0];
					pos = ret[1];
					for (var i=0; i < length; i++) {
						value.push(buf.readInt16BE(pos));
						pos += 2;
					}
					p[k] = value;
					break;
				case Struct.TYPE.aint32:
					ret = getLen(buf,pos);
					length = ret[0];
					pos = ret[1];
					for (var i=0; i < length; i++) {
						value.push(buf.readInt32BE(pos));