--- /dev/null
+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"));
+
+}
projects / eow / blobdiff