New feature: basic Ajax suggestion for tags and implementation of Dojo toolkit

git-svn-id: https://semanticscuttle.svn.sourceforge.net/svnroot/semanticscuttle/trunk@151 b3834d28-1941-0410-a4f8-b48e95affb8f

1 files changed, 126 insertions, 0 deletions

diff --git a/includes/js/dojox/cometd/timesync.js b/includes/js/dojox/cometd/timesync.js
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+++ b/includes/js/dojox/cometd/timesync.js
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+if(!dojo._hasResource["dojox.cometd.timesync"]){ //_hasResource checks added by build. Do not use _hasResource directly in your code.
+dojo._hasResource["dojox.cometd.timesync"] = true;
+dojo.provide("dojox.cometd.timesync");
+dojo.require("dojox.cometd");
+
+/**
+ * this file provides the time synchronization extension to cometd.
+ * Timesync allows the client and server to exchange time information on every 
+ * handshake and connect message so that the client may calculate an approximate
+ * offset from it's own clock epoch to that of the server.
+ *
+ * With each handshake or connect, the extension sends timestamps within the 
+ * ext field like: {ext:{timesync:{tc:12345567890},...},...}
+ * where ts is the timestamp in ms since 1970 of when the message was sent.
+ *
+ * A cometd server that supports timesync, should respond with and ext field
+ * like: {ext:{timesync:{tc:12345567890,ts:1234567900,p:123},...},...}
+ * where ts is the timestamp sent by the client, te is the timestamp on the server
+ * of when the message was received and p is the poll duration in ms - ie the
+ * time the server took before sending the response.
+ *
+ * On receipt of the response, the client is able to use current time to determine
+ * the total trip time, from which p is subtracted to determine an approximate
+ * two way network traversal time. The assumption is made that the network is
+ * symmetric for traversal time, so the offset between the two clocks is 
+ * ts-tc-(now-tc-p)/2. In practise networks (and the cometd client/server software)
+ * is never perfectly symmetric, so accuracy is limited by the difference, which 
+ * can be 10s of milliseconds.
+ *
+ * In order to smooth over any transient fluctuations, the extension keeps a sliding
+ * average of the offsets received. By default this is over 10 messages, but this can
+ * be changed with the dojox.cometd.timesync._window element.
+ */
+dojox.cometd.timesync= new function(){
+
+	this._window=10;// The window size for the sliding average of offset samples.
+	this._minWindow=4;// The window size for the sliding average of offset samples.
+	this._offsets=new Array(); // The samples used to calculate the average offset.
+	this.offset=0;	// The offset in ms between the clients clock and the servers clock. Add this to the local
+			// time epoch to obtain server time.
+	this.samples=0; // The number of samples used to calculate the offset. If 0, the offset is not valid.
+	
+	this.getServerTime=function(){ // return: long
+		// Summary:
+		//	Calculate the current time on the server
+		// 
+		return new Date().getTime()+this.offset;
+	}
+	
+	this.getServerDate=function(){ // return: Date
+		// Summary:
+		//	Calculate the current time on the server
+		// 
+		return new Date(this.getServerTime());
+	}
+	
+	this.setTimeout=function(/*function*/call,/*long|Date*/atTimeOrDate){
+		// Summary:
+		//	Set a timeout function relative to server time
+		// call:
+		//	the function to call when the timeout occurs
+		// atTimeOrTime: 
+		//	a long timestamp or a Date representing the server time at
+		//	which the timeout should occur.
+		
+		var ts=(atTimeOrDate instanceof Date)?atTimeOrDate.getTime():(0+atTimeOrDate);
+		var tc=ts-this.offset;
+		var interval=tc-new Date().getTime();
+		if (interval<=0)
+			interval=1;
+		return setTimeout(call,interval);
+	}
+
+	this._in=function(/*Object*/msg){
+		// Summary:
+		//	Handle incoming messages for the timesync extension.
+		// description:
+		//	Look for ext:{timesync:{}} field and calculate offset if present.
+		// msg: 
+		//	The incoming bayeux message
+		
+		var channel=msg.channel;
+		if (channel &&  channel.indexOf('/meta/')==0){
+			if (msg.ext && msg.ext.timesync){
+				var sync=msg.ext.timesync;
+				var now=new Date().getTime();
+				
+				this._offsets.push(sync.ts-sync.tc-(now-sync.tc-sync.p)/2);
+				if (this._offsets.length>this._window)
+					this._offsets.shift();		
+				this.samples++;
+				var total=0;
+				for (var i in this._offsets)
+					total+=this._offsets[i];
+				this.offset=parseInt((total/this._offsets.length).toFixed());
+				
+				if (this.samples<this._minWindow)
+					setTimeout(dojox._scopeName + ".cometd.publish('/meta/ping',null)",100);
+			}
+		}
+		return msg;
+	}
+
+	this._out=function(msg){
+		// Summary:
+		//	Handle outgoing messages for the timesync extension.
+		// description:
+		//	Look for handshake and connect messages and add the ext:{timesync:{}} fields
+		// msg: 
+		//	The outgoing bayeux message
+		
+		var channel=msg.channel;
+		if (channel &&  channel.indexOf('/meta/')==0){
+			var now=new Date().getTime();
+			if (!msg.ext)
+				msg.ext={};
+			msg.ext.timesync={tc: now};
+		}
+		return msg;
+	}
+};
+
+dojox.cometd._extendInList.push(dojo.hitch(dojox.cometd.timesync,"_in"));
+dojox.cometd._extendOutList.push(dojo.hitch(dojox.cometd.timesync,"_out"));
+
+}