Migrated source code from Simantics SVN

[simantics/platform.git] / bundles / org.simantics.db.common / src / org / simantics / db / common / procedure / guarded / GuardedAsyncProcedureWrapper.java

diff --git a/bundles/org.simantics.db.common/src/org/simantics/db/common/procedure/guarded/GuardedAsyncProcedureWrapper.java b/bundles/org.simantics.db.common/src/org/simantics/db/common/procedure/guarded/GuardedAsyncProcedureWrapper.java
new file mode 100644 (file)
index 0000000..5fd1f70
--- /dev/null
+++ b/bundles/org.simantics.db.common/src/org/simantics/db/common/procedure/guarded/GuardedAsyncProcedureWrapper.java
@@ -0,0 +1,63 @@
+/*******************************************************************************\r
+ * Copyright (c) 2007, 2010 Association for Decentralized Information Management\r
+ * in Industry THTH ry.\r
+ * All rights reserved. This program and the accompanying materials\r
+ * are made available under the terms of the Eclipse Public License v1.0\r
+ * which accompanies this distribution, and is available at\r
+ * http://www.eclipse.org/legal/epl-v10.html\r
+ *\r
+ * Contributors:\r
+ *     VTT Technical Research Centre of Finland - initial API and implementation\r
+ *******************************************************************************/\r
+package org.simantics.db.common.procedure.guarded;\r
+\r
+import java.util.concurrent.atomic.AtomicBoolean;\r
+import java.util.concurrent.atomic.AtomicInteger;\r
+\r
+import org.simantics.db.AsyncReadGraph;\r
+import org.simantics.db.common.procedure.adapter.AsyncProcedureAdapter;\r
+import org.simantics.db.procedure.AsyncProcedure;\r
+import org.simantics.db.procedure.Procedure;\r
+\r
+/**\r
+ * An asynchronous database callback procedure that is guarded against multiple\r
+ * invocations to {@link Procedure#execute(Object)} and\r
+ * {@link Procedure#exception(Throwable)}. Only the first invocation of is\r
+ * delegated or the Nth invocation to {@link Procedure#execute(Object)} where\r
+ * Nth is <code>expectedResults</code>.\r
+ * \r
+ * @author Tuukka Lehtonen\r
+ * \r
+ * @param <T>\r
+ */\r
+public class GuardedAsyncProcedureWrapper<T> extends AsyncProcedureAdapter<T> {\r
+\r
+    private final AsyncProcedure<T> procedure;\r
+    private final AtomicBoolean     onceGuard = new AtomicBoolean(false);\r
+    private final AtomicInteger     resultCounter;\r
+\r
+    public GuardedAsyncProcedureWrapper(AsyncProcedure<T> procedure, int expectedResults) {\r
+        this.procedure = procedure;\r
+        this.resultCounter = new AtomicInteger(expectedResults);\r
+    }\r
+\r
+    @Override\r
+    public void exception(AsyncReadGraph graph, Throwable t) {\r
+        if (onceGuard.compareAndSet(false, true)) {\r
+            procedure.exception(graph, t);\r
+        }\r
+    }\r
+\r
+    @Override\r
+    public void execute(AsyncReadGraph graph, T result) {\r
+        int count = resultCounter.decrementAndGet();\r
+        if (count == 0) {\r
+            if (onceGuard.compareAndSet(false, true)) {\r
+                procedure.execute(graph, result);\r
+            }\r
+        } else if (count < 0) {\r
+            System.out.println(this + ": execute invoked more than expected (count=" + count + ", procedure=" + procedure + ")");\r
+        }\r
+    }\r
+\r
+}\r