socket.io/lib/transport.js

/**
 * Socket.IO client
 * 
 * @author Guillermo Rauch <guillermo@learnboost.com>
 * @license The MIT license.
 * @copyright Copyright (c) 2010 LearnBoost <dev@learnboost.com>
 */

// abstract

(function(){
	
	var frame = '~m~',
	
	stringify = function(message){
		if (Object.prototype.toString.call(message) == '[object Object]'){
			if (!('JSON' in window)){
				if ('console' in window && console.error) console.error('Trying to encode as JSON, but JSON.stringify is missing.');
				return '{ "$error": "Invalid message" }';
			}
			return '~j~' + JSON.stringify(message);
		} else {
			return String(message);
		}
	};
	
	Transport = io.Transport = function(base, options){
		this.base = base;
		this.options = {
			timeout: 15000 // based on heartbeat interval default
		};
		io.util.merge(this.options, options);
	};

	Transport.prototype.send = function(){
		throw new Error('Missing send() implementation');
	};

	Transport.prototype.connect = function(){
		throw new Error('Missing connect() implementation');
	};

	Transport.prototype.disconnect = function(){
		throw new Error('Missing disconnect() implementation');
	};
	
	Transport.prototype._encode = function(messages){
		var ret = '', message,
				messages = io.util.isArray(messages) ? messages : [messages];
		for (var i = 0, l = messages.length; i < l; i++){
			message = messages[i] === null || messages[i] === undefined ? '' : stringify(messages[i]);
			ret += frame + message.length + frame + message;
		}
		return ret;
	};
	
	Transport.prototype._decode = function(data){
		var messages = [], number, n;
		do {
			if (data.substr(0, 3) !== frame) return messages;
			data = data.substr(3);
			number = '', n = '';
			for (var i = 0, l = data.length; i < l; i++){
				n = Number(data.substr(i, 1));
				if (data.substr(i, 1) == n){
					number += n;
				} else {	
					data = data.substr(number.length + frame.length);
					number = Number(number);
					break;
				} 
			}
			messages.push(data.substr(0, number)); // here
			data = data.substr(number);
		} while(data !== '');
		return messages;
	};
	
	Transport.prototype._onData = function(data){
		this._setTimeout();
		var msgs = this._decode(data);
		if (msgs && msgs.length){
			for (var i = 0, l = msgs.length; i < l; i++){
				this._onMessage(msgs[i]);
			}
		}
	};
	
	Transport.prototype._setTimeout = function(){
		var self = this;
		if (this._timeout) clearTimeout(this._timeout);
		this._timeout = setTimeout(function(){
			self._onTimeout();
		}, this.options.timeout);
	};
	
	Transport.prototype._onTimeout = function(){
		this._onDisconnect();
	};
	
	Transport.prototype._onMessage = function(message){
		if (!this.sessionid){
			this.sessionid = message;
			this._onConnect();
		} else if (message.substr(0, 3) == '~h~'){
			this._onHeartbeat(message.substr(3));
		} else if (message.substr(0, 3) == '~j~'){
			this.base._onMessage(JSON.parse(message.substr(3)));
		} else {
			this.base._onMessage(message);
		}
	},
	
	Transport.prototype._onHeartbeat = function(heartbeat){
		this.send('~h~' + heartbeat); // echo
	};
	
	Transport.prototype._onConnect = function(){
		this.connected = true;
		this.connecting = false;
		this.base._onConnect();
		this._setTimeout();
	};

	Transport.prototype._onDisconnect = function(){
		this.connecting = false;
		this.connected = false;
		this.sessionid = null;
		this.base._onDisconnect();
	};

	Transport.prototype._prepareUrl = function(){
		return (this.base.options.secure ? 'https' : 'http') 
			+ '://' + this.base.host 
			+ ':' + this.base.options.port
			+ '/' + this.base.options.resource
			+ '/' + this.type
			+ (this.sessionid ? ('/' + this.sessionid) : '/');
	};

})();