initial commit

README.md

@@ -0,0 +1,72 @@
+Long Polling Buffer
+===================
+
+(C) Rob Righter (@robrighter) 2009, Licensed under the MIT-LICENSE
+
+A Library for Node.js to simplify AJAX long polling
+
+API
+---
+
+### LongPollingBuffer(buffersize)
+
+Constructor. Initializes the buffer to be of size buffersize
+
+### push(value)
+
+Pushes data onto the queue which in turn notifies all the listeners
+
+### addListenerForUpdateSince(since, callback)
+
+Adds a listener for data updates. The callback is triggered when data is available after the since.
+
+
+Example usage: Simple Activity Monitor
+--------------------------------------
+
+var fu = require("./lib/fu");
+var sys = require('sys');
+process.mixin(GLOBAL, require("./lib/underscore"));
+var lpb = require("./lib/longpollingbuffer");
+
+HOST = null; // localhost
+PORT = 8000;
+
+//helper function
+String.prototype.trim = function() {
+    return this.replace(/^\s+|\s+$/g,"");
+}
+
+// Now start the program
+fu.listen(PORT, HOST);
+var rb = new lpb.LongPollingBuffer(200); //Create the Long Polling Buffer
+var iostat = process.createChildProcess("iostat", ["-w 1"])
+
+
+//Setup the listener to handle the flow of data from iostat 
+iostat.addListener("output", function (data) {
+    sys.puts(data);
+    if(data.search(/cpu/i) == -1){ //suppress the column header from iostat
+        rb.push(data.trim().split(/\s+/).join(" "));
+    }
+});
+
+//Setup the updater page for long polling  
+fu.get("/update", function (req, res) {
+      res.sendHeader(200,{"Content-Type": "text/html"});
+      var thesince = parseInt(req.uri.params.since);
+      if(!thesince){
+          thesince = -1;
+      }
+
+      rb.addListenerForUpdateSince(thesince, function(data){
+           var body = '['+_.map(data,JSON.stringify).join(',\n')+']';
+           res.sendBody( body );
+           res.finish();
+      });
+});
+
+// Static Files
+fu.get("/", fu.staticHandler("./client-side/index.html"));
+fu.get("/css/site.css", fu.staticHandler("./client-side/css/site.css"));
+fu.get("/js/site.js", fu.staticHandler("./client-side/js/site.js"));

example.js

@@ -0,0 +1,27 @@
+var sys = require('sys');
+var un = require("./lib/underscore");
+var lpb = require("./lib/longpollingbuffer");
+
+var rb = new lpb.LongPollingBuffer(8);
+
+rb.push("I'm");
+rb.push('affraid');
+rb.push('the Death Star');
+rb.push('will be');
+rb.push('fully');
+rb.push('operational');
+rb.push('when');
+rb.push('your');
+rb.push('friends');
+rb.push('arrive');
+
+
+//Since forever (or to the size of teh buffer)
+rb.addListenerForUpdateSince(-1, function(data){
+     sys.puts('\n\nSince forever (or to the size of the buffer): \n' + _.map(data,JSON.stringify).join(',\n') );
+});
+
+//Since offset 6
+rb.addListenerForUpdateSince(6, function(data){
+     sys.puts('\n\nSince offset 6: \n' + _.map(data,JSON.stringify).join(',\n') );
+});

lib/longpollingbuffer.js

@@ -0,0 +1,47 @@
+var sys = require('sys');
+var un = require("./underscore");
+
+//the readbuffer provides a databuffer with a moving offset that can be used to allow AJAX long polling (instead of the websocket)
+function LongPollingBuffer (buffersize) {
+    this.data = new Array();
+    this.size = buffersize;
+    this.offset = 0;
+
+    function BufferItem (offset,value) {
+        this.offset = offset;
+        this.value = value;
+    }
+
+    this.push = function(value) {
+        this.data.unshift(new BufferItem(this.offset++,value));
+        while(this.data.length > this.size){
+            this.data.pop([]);
+        }
+        this.emit('newdata',this.data);
+    }
+
+    this.datasince = function(since) {
+        return un._.select(this.data, function(item){ return item.offset>since; });
+    }
+
+    this.addListenerForUpdateSince = function(since, callback) {
+        response = this.datasince(since);
+        if(response.length==0){
+            //no data yet pass off the callout to wait for it
+            this.addListener('newdata', function(thedata){
+                callback(this.datasince(since));
+            });
+        }
+        else {
+            //send back the data
+            callback(response);
+        }
+    }
+}
+
+LongPollingBuffer.prototype = new process.EventEmitter();
+
+
+process.mixin(exports, {
+  LongPollingBuffer: LongPollingBuffer
+});