Add Isolate ping functionality.

sdk/lib/isolate/isolate.dart

Index: sdk/lib/isolate/isolate.dart
diff --git a/sdk/lib/isolate/isolate.dart b/sdk/lib/isolate/isolate.dart
index a8063a083e695b133935d081f440d7010259e43f..0781697b5907039fd2ec036e29e3e59f921cf8f1 100644
--- a/sdk/lib/isolate/isolate.dart
+++ b/sdk/lib/isolate/isolate.dart
@@ -29,6 +29,13 @@ class IsolateSpawnException implements Exception {
 }
 
 class Isolate {
+  /** Argument to `ping`: Ask for immediate response. */
+  static const int PING_ALIVE = 0;
+  /** Argument to `ping`: Ask for response after control events. */
+  static const int PING_CONTROL = 1;
+  /** Argument to `ping`: Ask for response after normal events. */
+  static const int PING_EVENT = 2;
+
   /**
    * Control port used to send control messages to the isolate.
    *
@@ -104,7 +111,7 @@ class Isolate {
    *
    * Returns the capability that must be used to resume end the pause.
    *
-   * WARNING: This method is not handled on any platform yet.
+   * WARNING: This method is not handled on all platforms yet.
    */
   Capability pause([Capability resumeCapability]) {
     if (resumeCapability == null) resumeCapability = new Capability();
@@ -125,7 +132,7 @@ class Isolate {
    * 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.
+   * WARNING: This method is not handled on all platforms yet.
    */
   void resume(Capability resumeCapability) {
     var message = new List(2)
@@ -133,6 +140,39 @@ class Isolate {
         ..[1] = resumeCapability;
     controlPort.send(message);
   }
+
+  /**
+   * Request that the isolate send a response on the [responsePort].
+   *
+   * If the isolate is alive, it will eventually send a `null` response on
+   * the response port.
+   *
+   * The [pingType] must be one of [PING_ALIVE], [PING_CONTROL] or [PING_EVENT].
+   * The response is sent at different times depending on the ping type:
+   *
+   * * `PING_ALIVE`: The the isolate responds as soon as possible.

[Anders Johnsen, 2014/03/04 14:06:20]

The the

+   *     The response should happen no sooner than if sent with `PING_CONTROL`.
+   *     It may be sent earlier of the system has a way to do so.

[Anders Johnsen, 2014/03/04 14:06:20]

of -> if

+   * * `PING_CONTROL`: The response it not sent until all previously sent
+   *     control messages from the current isolate to the receiving isolate
+   *     have been processed. This can be used to wait for
+   *     previously sent control messages.
+   * * `PING_EVENT`: The response is not sent until all prevously sent
+   *     non-control messages from the current isolate to the receiving isolate
+   *     have been processed.
+   *     The ping effectively puts the resonse into the normal event queue after
+   *     previously sent messages.
+   *     This can be used to wait for a another event to be processed.
+   *
+   * WARNING: This method is not handled on all platforms yet.
+   */
+  void ping(SendPort responsePort, [int pingType = PING_ALIVE]) {
+    var message = new List(3)
+        ..[0] = "ping"
+        ..[1] = responsePort
+        ..[2] = pingType;
+    controlPort.send(message);
+  }
 }
 
 /**