Let’s suppose your app makes a lot of http requests at once, and you need a good administration for that. Based on used browser your app is running on, you are only allowed to limited request count – mostly its 2 requests per domain, the remaining ones are sitting in browser buffer waiting to finish those actual. URLRequestBuffer is handy class that lets you manage URLRequest-s. E.g. you are creating image gallery and request hundreds of images in gallery at a time, now when user navigates throug the images you need to make some request more prioritized before others, some to be canceled, some may timeout etc. Here comes URLRequestBuffer in scene.

Pushing requests into the buffer automaticaly sorts requests by priority and tries to load next request based on priority/delay logic. After request is complete (timeouted, or error) it loads next and so on. Usage is very simple once you get familiar with 3 classes it consist of (URLRequestBuffer, URLRequestBufferItem and URLRequestBufferEvent)

// define buffer and max simultaneous (active) requests
var buffer:URLRequestBuffer = new URLRequestBuffer(2);

// loader - URLLoader or Loader instance
// request - URLRequest instance
// priority - uint, higher priority requests loads first
// delay - request is called after X milliseconds after pushing
// pushing requests into buffer returns URLRequestBufferItem, next suitable requests called
var bufferItem:URLRequestBufferItem = buffer.push(loader, request, priority, delay);
var bufferId:uint = bufferItem.id;

// URLRequestBufferItem by bufferId
buffer.getWaitingById(bufferId)
buffer.getActiveById(bufferId)

// stop and trash request (buffered or active)
buffer.removeWaitingById(bufferId);
buffer.removeActiveById(bufferId);

// enumerating waiting item list
for(var i:uint = 0; i < buffer.countWaiting; i++)
    bufferItem = buffer.getWaitingItem(i);

// enumerating active item list
for(var i:uint = 0; i < buffer.countActive; i++)
    bufferItem = buffer.getActiveItem(i);

// buffer event handling
buffer.addEventListener(URLRequestBufferEvent.WAITING_REQUEST_ADDED, onBufferChange);
buffer.addEventListener(URLRequestBufferEvent.WAITING_REQUEST_REMOVED, onBufferChange);
buffer.addEventListener(URLRequestBufferEvent.ACTIVE_REQUEST_ADDED, onBufferChange);
buffer.addEventListener(URLRequestBufferEvent.ACTIVE_REQUEST_REMOVED, onBufferChange);
buffer.addEventListener(URLRequestBufferEvent.REQUEST_TIMEOUT, onBufferChange);

private function onBufferChange(event:URLRequestBufferEvent):void
{
    var bufferItem:URLRequestBufferItem = event.item;

    // some stats
    trace(buffer.countWaiting, buffer.countActive)
}

Update: jdem.cz, tinyurl.com, bit.ly, tr.im, is.gd providers implemented.

Application (view source enabled), please use your own api key for bit.ly

I have just discovered tr.im has not crossdomain.xml, please do not us it while it throws errors. I have just asked them and few more providers to create crossdomain files, will see…

There are two methods you can handle resuls:

// 1. use callback function
URLShorten.jdemcz(long_url.text, jdemczResult);

// ...callback function gets one parameter = short url
private function jdemczResult(url:String):void
{
    jdemcz = url;
}

// 2. addEventDispatcher to have bigger control
var dispatcher:EventDispatcher = URLShorten.tinyurlcom(long_url.text);
dispatcher.addEventListener(URLShortenEvent.COMPLETE, tinyurlcomComplete);

// ...dispatched event.url = short url
private function tinyurlcomComplete(event:URLShortenEvent):void
{
    tinyurl = event.url;
}

URLShorten class

package sk.yoz.net
{
    import com.adobe.serialization.json.JSON;

    import flash.events.Event;
    import flash.net.URLRequest;
    import flash.net.URLVariables;

    import sk.yoz.events.URLShortenEvent;

    public class URLShorten extends Object
    {
        public function URLShorten()
        {
            super();
        }

        private static function prepare(request:URLRequest,
            variables:URLVariables, callback:Function,
            completeHandler:Function=null):URLLoaderDynamic
        {
            var loader:URLLoaderDynamic = new URLLoaderDynamic();
            var handler:Function = completeHandler || complete;

            request.data = variables;
            loader.callback = callback;
            loader.load(request);
            loader.addEventListener(Event.COMPLETE, handler);
            return loader;
        }

        private static function complete(event:Event):void
        {
            var loader:URLLoaderDynamic = URLLoaderDynamic(event.target);
            var url:String = String(loader.data);

            loader.removeEventListener(Event.COMPLETE, complete);
            dispatch(url, loader)
        }

        private static function dispatch(url:String, loader:URLLoaderDynamic)
            :void
        {
            var callback:Function = loader.callback;
            var type:String = URLShortenEvent.COMPLETE;

            if(callback != null)
                callback(url);
            loader.dispatchEvent(new URLShortenEvent(type, false, false, url));
        }

        public static function jdemcz(longUrl:String, callback:Function=null)
            :URLLoaderDynamic
        {
            var apiUrl:String = "http://www.jdem.cz/get";
            var request:URLRequest = new URLRequest(apiUrl);
            var variables:URLVariables = new URLVariables();

            variables.url = longUrl;
            return prepare(request, variables, callback);
        }

        public static function tinyurlcom(longUrl:String,
            callback:Function=null):URLLoaderDynamic
        {
            var apiUrl:String = "http://tinyurl.com/api-create.php";
            var request:URLRequest = new URLRequest(apiUrl);
            var variables:URLVariables = new URLVariables();

            variables.url = longUrl;
            return prepare(request, variables, callback);
        }

        public static function bitly(longUrl:String, login:String,
            apiKey:String, version:String="2.0.1", callback:Function=null)
            :URLLoaderDynamic
        {
            var apiUrl:String = "http://api.bit.ly/shorten";
            var request:URLRequest = new URLRequest(apiUrl);
            var variables:URLVariables = new URLVariables();

            variables.version = version;
            variables.longUrl = longUrl;
            variables.login = login;
            variables.apiKey = apiKey;
            return prepare(request, variables, callback, bitlyComplete);
        }

        private static function bitlyComplete(event:Event):void
        {
            var loader:URLLoaderDynamic = URLLoaderDynamic(event.target);
            var result:String = String(loader.data);
            var data:Object = JSON.decode(result);
            var url:String;

            loader.removeEventListener(Event.COMPLETE, bitlyComplete);
            for each(var resultItem:Object in data.results)
                url = resultItem.shortUrl;
            dispatch(url, loader);
        }

        public static function trim(longUrl:String,
            callback:Function=null):URLLoaderDynamic
        {
            var apiUrl:String = "http://api.tr.im/v1/trim_simple";
            var request:URLRequest = new URLRequest(apiUrl);
            var variables:URLVariables = new URLVariables();

            variables.url = longUrl;
            return prepare(request, variables, callback);
        }

        public static function isgd(longUrl:String,
            callback:Function=null):URLLoaderDynamic
        {
            var apiUrl:String = "http://is.gd/api.php";
            var request:URLRequest = new URLRequest(apiUrl);
            var variables:URLVariables = new URLVariables();

            variables.longurl = longUrl;
            return prepare(request, variables, callback);
        }
    }
}

we need loader to hold callback function reference, URLLoaderDynamic class pretty much fits this needs

package sk.yoz.net
{
    import flash.net.URLRequest;
    import flash.net.URLLoader;

    import sk.yoz.net.URLLoaderDynamic;

    public dynamic class URLLoaderDynamic extends URLLoader
    {
        public function URLLoaderDynamic(request:URLRequest=null)
        {
            super(request);
        }

    }
}

custom URLShortenEvent class is dispatched after url is returned

package sk.yoz.events
{
    import flash.events.Event;

    public class URLShortenEvent extends Event
    {
        public static const COMPLETE:String = "URLShortenEventCOMPLETE";

        private var _url:String;

        public function URLShortenEvent(type:String, bubbles:Boolean=false,
            cancelable:Boolean=false, url:String="")
        {
            super(type, bubbles, cancelable);
            _url = url;
        }

        public function get url():String
        {
            return _url;
        }
    }
}