Add pause methods to Isolate.

sdk/lib/isolate/isolate.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.
 
 /**
  * Concurrent programming using _isolates_:
  * independent workers that are similar to threads
  * but don't share memory,
  * communicating only via messages.
  *
@@ skipping 11 matching lines @@
  * Thrown when an isolate cannot be created.
  */
 class IsolateSpawnException implements Exception {
   // TODO(floitsch): clean up spawn exception.
   const IsolateSpawnException(String this._s);
   String toString() => "IsolateSpawnException: '$_s'";
   final String _s;
 }
 
 class Isolate {
+  /**
+   * Control port used to send control messages to the isolate.
+   *
+   * This class provides helper functions that sends control messages
+   * to the control port.
+   */
+  final SendPort controlPort;
+  final Capability pauseCapability;
 
-  final SendPort _controlPort;
-
-  Isolate._fromControlPort(SendPort controlPort)
-      : this._controlPort = controlPort;
+  Isolate._fromControlPort(this.controlPort, [this.pauseCapability]);
 
   /**
    * Creates and spawns an isolate that shares the same code as the current
    * isolate.
    *
    * The argument [entryPoint] specifies the entry point of the spawned
    * isolate. It must be a top-level function or a static method that
    * takes one argument - that is, one-parameter functions that can be
    * compile-time constant function values.
    * It is not allowed to pass the value of function expressions or an instance
@@ skipping 22 matching lines @@
    * * `main(args, message)`
    *
    * When present, the parameter `args` is set to the provided [args] list.
    * When present, the parameter `message` is set to the initial [message].
    *
    * Returns a future that will complete with an [Isolate] instance if the
    * spawning succeeded. It will complete with an error otherwise.
    */
   external static Future<Isolate> spawnUri(
       Uri uri, List<String> args, var message);
+
+
+  /**
+   * Requests the isolate to pause.
+   *
+   * The isolate should stop handling events by pausing its event queue.
+   * The request will eventually make the isolate stop doing anything.
+   * It will be handled before any other messages sent to the isolate from
+   * the current isolate, but no other guarantees are provided.
+   *
+   * If [resumeCapability] is provided, it is used to identity the pause,
+   * and must be used again to end the pause using [resume].
+   * Otherwise a new capability is created and returned.
+   *
+   * If an isolate is paused more than once using the same capabilty,
+   * only one resume with that capability is needed to end the pause.
+   *
+   * If an isolate is paused using more than one capability,
+   * they must all be individully ended before the isolate resumes.
+   *
+   * Returns the capability that must be used to resume end the pause.
+   *
+   * WARNING: This method is not handled on any platform yet.
+   */
+  Capability pause([Capability resumeCapability]) {
+    if (resumeCapability == null) resumeCapability = new Capability();
+    var message = new List(3)
+        ..[0] = "pause"
+        ..[1] = pauseCapability
+        ..[2] = resumeCapability;
+    controlPort.send(message);
+    return resumeCapability;
+  }
+
+  /**
+   * Resumes a paused isolate.
+   *
+   * Sends a message to an isolate requesting that it ends a pause
+   * that was requested using the [resumeCapability].
+   *
+   * The capability must be one returned by a call to [pause] on this
+   * isolate, otherwise the resume call does nothing.
+   *
+   * WARNING: This method is not handled on any platform yet.
+   */
+  void resume(Capability resumeCapability) {
+    var message = new List(2)
+        ..[0] = "resume"
+        ..[1] = resumeCapability;
+    controlPort.send(message);
+  }
 }
 
 /**
  * Sends messages to its [ReceivePort]s.
  *
  * [SendPort]s are created from [ReceivePort]s. Any message sent through
  * a [SendPort] is delivered to its corresponding [ReceivePort]. There might be
  * many [SendPort]s for the same [ReceivePort].
  *
  * [SendPort]s can be transmitted to other isolates.
@@ skipping 145 matching lines @@
   const _IsolateUnhandledException(this.message, this.source, this.stackTrace);
 
   String toString() {
     return 'IsolateUnhandledException: exception while handling message: '
         '${message} \n  '
         '${source.toString().replaceAll("\n", "\n  ")}\n'
         'original stack trace:\n  '
         '${stackTrace.toString().replaceAll("\n","\n  ")}';
   }
 }