cadorn · February 2, 2012 19:39 · Feb 2, 2012 · Feb 2, 2012 · Feb 2, 2012 · Feb 2, 2012
diff --git a/q-throttle.js b/q-throttle.js
@@ -17,6 +17,7 @@
  *     
  *     for (var i=0 ; i < 10 ; i++) {
  *         throttle.when([i], function(i) {
+ *             // Never more than 3 unresolved doDeferredWork() promises
  *             return doDeferredWork(i).then(function() {
  *             });
  *         });

diff --git a/q-throttle.js b/q-throttle.js
@@ -9,6 +9,7 @@
  *     
  *     var Q = require("q");
  *     
+ *     // Require this module (to add `Q.Throttle` to the `Q` API)
  *     Q.Throttle = require("q-throttle").Throttle;
  *     
  *     // Maximum of 3 unresolved promises at a time

diff --git a/gistfile1.txt → q-throttle.js b/gistfile1.txt → q-throttle.js
diff --git a/gistfile1.txt b/gistfile1.txt
@@ -1 +1,134 @@
-.
+/**
+ * Copyright: 2012 Christoph Dorn <[email protected]>
+ * License: MIT
+ * Source: https://gist.github.com/1725325
+ * 
+ * NodeJS Example:
+ * 
+ *     // Requirements: `npm install q`
+ *     
+ *     var Q = require("q");
+ *     
+ *     Q.Throttle = require("q-throttle").Throttle;
+ *     
+ *     // Maximum of 3 unresolved promises at a time
+ *     var throttle = Q.Throttle(3);
+ *     
+ *     for (var i=0 ; i < 10 ; i++) {
+ *         throttle.when([i], function(i) {
+ *             return doDeferredWork(i).then(function() {
+ *             });
+ *         });
+ *     }
+ *
+ *     throttle.on("done", function()
+ *     {
+ *     });
+ *
+ */
+
+
+var Q = require("q"),
+	EVENTS = require("events");
+
+
+var Throttle = exports.Throttle = function(max)
+{
+	if (!(this instanceof Throttle))
+        return new Throttle(max);
+
+	this.count = 0;
+	this.buffer = [];
+	this.max = max;
+};
+Throttle.prototype = new EVENTS.EventEmitter();
+Throttle.prototype.when = function(args, func)
+{
+	var self = this,
+		result;
+
+	if (self.count >= self.max)
+	{
+		self.buffer.push([args, func]);
+		return;
+	}
+	self.count += 1;
+
+	result = func.apply(null, args);
+
+	if (!Q.isPromise(result))
+	{
+		throw new Error("Throttled function call did not return a promise!");
+	}
+
+	Q.when(result, function()
+	{
+		self.count -= 1;
+		if (self.buffer.length > 0)
+		{
+			var info = self.buffer.shift();
+			self.when(info[0], info[1]);
+		}
+		else
+		if (self.count === 0)
+		{
+			self.emit("done");
+		}
+	});
+}
+
+
+exports.Throttle_Test = function()
+{
+	var deferred = Q.defer();
+
+	try
+	{	
+		// Maximum of 3 unresolved promises at a time
+		var throttle = new Throttle(3),
+			list = [],
+		    i,
+		    count = 0;
+
+		console.log("Running Throttle_Test:");
+
+		for (i=0 ; i < 10 ; i++)
+		{
+			list.push(function()
+			{
+				return Q.delay(200 + (100 * i%3/10));
+			});
+		}
+
+		for (i=0 ; i < list.length ; i++)
+		{
+			console.log("  triggering " + i);		
+		    throttle.when([i], function(i)
+		    {
+		        // Only 3 unresolved promises will run at a time
+		    	console.log("    starting " + i);
+		    	count += 1;
+		    	if (count > 3) throw new Error("More than 3 unresolved promises at the same time!");
+		        return list[i]().then(function()
+		        {
+			    	console.log("      " + i + " done");
+			    	count -= 1;
+		        });
+		    });
+		}
+
+		console.log("  triggering done");		
+
+		throttle.on("done", function()
+		{
+			console.log("Throttle_Test OK!");
+			deferred.resolve();
+		});
+	}
+	catch(e)
+	{
+		deferred.reject(e);
+	}
+
+	return deferred.promise;
+}
diff --git a/gistfile1.txt b/gistfile1.txt
@@ -0,0 +1 @@
+.