Introduce optimized Timer.run queue for immediate runs.

sdk/lib/async/timer.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of dart.async;
 
 abstract class Timer {
+  // Internal queue used to group Timer.run callbacks.
+  static Queue _queue = new Queue();

[floitsch, 2013/02/25 16:07:13]

A list is good enough.

[Anders Johnsen, 2013/02/25 16:25:18]

Done.

+
   /**
    * Creates a new timer.
    *
    * The [callback] callback is invoked after the given [duration]
    * (a [Duration]) has passed. A negative duration is treated similar to
    * a duration of 0.
    *
    * If the [duration] is statically known to be 0, consider using [run].
    *
    * Frequently the [duration] is either a constant or computed as in the
@@ skipping 23 matching lines @@
    *
    * *Deprecation warning*: this constructor used to take an [int] (the time
    * in milliseconds). This has changed to a [Duration].
    */
   external factory Timer.repeating(var duration,
                                    void callback(Timer timer));
 
   /**
    * Runs the given [callback] asynchronously as soon as possible.
    *
    * Returns a [Timer] that can be cancelled if the callback is not necessary

[floitsch, 2013/02/25 16:07:13]

Update comment.

[Anders Johnsen, 2013/06/11 12:14:31]

Done.

    * anymore.
    */
-  static Timer run(void callback()) {
-    return new Timer(const Duration(), callback);
+  static void run(void callback()) {

[Søren Gjesse, 2013/02/25 16:00:38]

I don't see any problem with this not having any object associated for canceling
it. It is run "almost immediately" so the cancellation window is short and would
most likely have to use some knowledge about the order of execution if one
Timer.run function should be cancelled from another Tumer.run function.

[Anders Johnsen, 2013/02/25 16:25:18]

Done.

+    bool run = _queue.isEmpty;
+    _queue.addLast(callback);
+    if (run) {
+      new Timer(const Duration(), () {

[floitsch, 2013/02/25 16:07:13]

Duration(milliseconds: 0)

[Anders Johnsen, 2013/02/25 16:25:18]

Done.

+        var queue = _queue;

[floitsch, 2013/02/25 16:07:13]

Use type.

[Anders Johnsen, 2013/02/25 16:25:18]

Done.

+        _queue = new Queue();

[Søren Gjesse, 2013/02/25 16:00:38]

Please make a comment to why you create a new queue here (not starving real
timers I presume).

[Anders Johnsen, 2013/02/25 16:25:18]

Done.

+        while (!queue.isEmpty) {

[floitsch, 2013/02/25 16:07:13]

With the list:
function runQueued(List queued, int startAt) {
  for (int i = startAt; i < queued.length; i++) {
    Function f = queued[i];
    try {
      f();
    } catch(e) {
      _list.insertRange(0, 1);
      _list[0] = () => runQueued(queued, i + 1);
      throw;  // rethrow.
    }
  }
}
List queued = _list;
_list = new List<Function>();
runQueued(queued, 0);

[Anders Johnsen, 2013/02/25 16:25:18]

Didn't do exactly this, but close.

+          // Let it fall-through, as we already are at the top of the stack.
+          queue.removeFirst()();
+        }
+      });
+    }
   }
 
   /**
    * Cancels the timer.
    */
   void cancel();
 }