Implement scheduleImmediate for the VM.

runtime/lib/isolate_patch.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.
 
 import "dart:collection" show HashMap;
 
 patch class ReceivePort {
   /* patch */ factory ReceivePort() = _ReceivePortImpl;
 
   /* patch */ factory ReceivePort.fromRawReceivePort(RawReceivePort rawPort) =
@@ skipping 39 matching lines @@
 
   close() {
     _rawPort.close();
     _controller.close();
   }
 
   final RawReceivePort _rawPort;
   StreamController _controller;
 }
 
+typedef void ImmediateCallback();
+
+/// The callback that has been registered through `scheduleImmediate`.
+ImmediateCallback _pendingImmediateCallback;
+
+/// The closure that should be used as scheduleImmediateClosure, when the VM
+/// is responsible for the event loop.
+void _isolateScheduleImmediate(void callback()) {
+  assert(_pendingImmediateCallback == null);
+  _pendingImmediateCallback = callback;
+}
+
+/// The embedder can execute this function to get hold of
+/// [_isolateScheduleImmediate] above.
+Function _getIsolateScheduleImmediateClosure() {
+  return _isolateScheduleImmediate;
+}
+
 class _RawReceivePortImpl implements RawReceivePort {
   factory _RawReceivePortImpl() native "RawReceivePortImpl_factory";
 
   close() {
     _portMap.remove(_id);
     _closeInternal(_id);
   }
 
   SendPort get sendPort {
     return new _SendPortImpl(_id);
@@ skipping 15 matching lines @@
 
   // Called from the VM to retrieve the RawReceivePort for a message.
   static _RawReceivePortImpl _lookupReceivePort(int id) {
     return _portMap[id];
   }
 
   // Called from the VM to dispatch to the handler.
   static void _handleMessage(
       _RawReceivePortImpl port, int replyId, var message) {
     assert(port != null);
+    // TODO(floitsch): this relies on the fact that any exception aborts the
+    // VM. Once we have non-fatal global exceptions we need to catch errors
+    // so that we can run the immediate callbacks.
     port._handler(message);
+    if (_pendingImmediateCallback != null) {
+      var callback = _pendingImmediateCallback;
+      _pendingImmediateCallback = null;
+      callback();
+    }
   }
 
   // Call into the VM to close the VM maintained mappings.
   static _closeInternal(int id) native "RawReceivePortImpl_closeInternal";
 
   void set handler(Function newHandler) {
     this._handler = newHandler;
   }
 
   final int _id;
@@ skipping 136 matching lines @@
   }
 
   static final RawReceivePort _self = _mainPort;
   static RawReceivePort get _mainPort native "Isolate_mainPort";
 
   static SendPort _spawnFunction(Function topLevelFunction)
       native "Isolate_spawnFunction";
 
   static SendPort _spawnUri(String uri) native "Isolate_spawnUri";
 }