Implement port equality on SendPortSync

sdk/lib/isolate/base.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.isolate;
 
 class IsolateSpawnException implements Exception {
   const IsolateSpawnException(String this._s);
   String toString() => "IsolateSpawnException: '$_s'";
   final String _s;
@@ skipping 121 matching lines @@
   void close();
 
   /**
    * Creates a new send port that sends to this receive port. It is legal to
    * create several [SendPort]s from the same [ReceivePort].
    */
   SendPort toSendPort();
 
 }
 
-// TODO(kasperl): Document this.
+/**
+ * [SendPortSync]s are created from [ReceivePortSync]s. Any message sent through
+ * a [SendPortSync] is delivered to its respective [ReceivePortSync]. There
+ * might be many [SendPortSync]s for the same [ReceivePortSync].
+ *
+ * [SendPortSync]s can be transmitted to other isolates.
+ */
 abstract class SendPortSync {
-
+  /**
+   * Sends a synchronous message to this send port and returns the result.
+   */
   callSync(var message);
 
+  /**
+   * Tests whether [other] is a [SendPortSync] pointing to the same
+   * [ReceivePortSync] as this one.
+   */
+  bool operator==(var other);
+
+  /**
+   * Returns an immutable hash code for this send port that is
+   * consistent with the == operator.
+   */
+  int get hashCode;
 }
 
 // The VM doesn't support accessing external globals in the same library. We
 // therefore create this wrapper class.
 // TODO(6997): Don't go through static class for external variables.
 abstract class _Isolate {
   external static ReceivePort get port;
   external static SendPort spawnFunction(void topLevelFunction(),
     [bool UnhandledExceptionCallback(IsolateUnhandledException e)]);
   external static SendPort spawnUri(String uri);
@@ skipping 17 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  ")}';
   }
 }