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+/*
+
+Copyright (c) Xerox Corporation 1998-2002. All rights reserved.
+
+Use and copying of this software and preparation of derivative works based
+upon this software are permitted. Any distribution of this software or
+derivative works must comply with all applicable United States export control
+laws.
+
+This software is made available AS IS, and Xerox Corporation makes no warranty
+about the software, its performance or its conformity to any specification.
+
+|<--- this code is formatted to fit into 80 columns --->|
+|<--- this code is formatted to fit into 80 columns --->|
+|<--- this code is formatted to fit into 80 columns --->|
+
+
+RegistrySynchronization.java
+Part of the Spacewar system.
+
+*/
+
+package spacewar;
+
+import coordination.Coordinator;
+
+
+/**
+ * This aspect ensures synchronized access to methods of the Registry in
+ * the presence of several threads.
+ *
+ * It uses the Coordinator class, from the AspectJ coordination library.
+ *
+ * It uses a per-Registry coordination scheme, so there is one instance of
+ * this class for each instance of the Registry class. When this class is
+ * constructed, it registers appropriate mutexes and selfexes using the
+ * behavior inherited from Coordinator.
+ *
+ * The mutating methods (register and unregister) should be self-exclusive.
+ * Each reader method should be mutually exclusive with the mutating
+ * methods. But the readers can run concurrently. */
+aspect RegistrySynchronization extends Coordinator perthis(this(Registry)) {
+
+ protected pointcut synchronizationPoint():
+ call(void Registry.register(..)) ||
+ call(void Registry.unregister(..)) ||
+ call(SpaceObject[] Registry.getObjects(..)) ||
+ call(Ship[] Registry.getShips(..));
+
+ public RegistrySynchronization() {
+ addSelfex("register");
+ addSelfex("unregister");
+
+ addMutex(new String[] {"register", "unregister", "getObjects"});
+ addMutex(new String[] {"register", "unregister", "getShips"});
+ }
+
+}