1 files changed, 154 insertions, 0 deletions
diff --git a/ridljar/com/sun/star/uno/WeakReference.java b/ridljar/com/sun/star/uno/WeakReference.java
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index 000000000..a6b171ac2
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+++ b/ridljar/com/sun/star/uno/WeakReference.java
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+/* -*- Mode: Java; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ *
+ * This file incorporates work covered by the following license notice:
+ *
+ *   Licensed to the Apache Software Foundation (ASF) under one or more
+ *   contributor license agreements. See the NOTICE file distributed
+ *   with this work for additional information regarding copyright
+ *   ownership. The ASF licenses this file to you under the Apache
+ *   License, Version 2.0 (the "License"); you may not use this file
+ *   except in compliance with the License. You may obtain a copy of
+ *   the License at http://www.apache.org/licenses/LICENSE-2.0 .
+ */
+
+package com.sun.star.uno;
+
+/**
+ * This class holds weak reference to an object.
+ *
+ * <p>It actually holds a reference to a <code>com.sun.star.XAdapter</code>
+ * implementation and obtains a hard reference if necessary.
+ */
+public class WeakReference
+{
+    private OWeakRefListener m_listener;
+    // There is no default constructor. Every instance must register itself with the
+    // XAdapter interface, which is done in the constructors. Assume we have this code
+    // WeakReference ref= new WeakReference();
+    // ref = someOtherWeakReference;
+    //
+    // ref would not be notified (XReference.dispose()) because it did not register
+    // itself. Therefore the XAdapter would be kept alive although this is not
+    // necessary.
+
+    /**
+     * Creates an instance of this class.
+     *
+     * @param obj another instance that is to be copied.
+     */
+    public WeakReference(WeakReference obj)
+    {
+        if (obj == null) {
+            return;
+        }
+        Object weakImpl = obj.get();
+        if (weakImpl == null) {
+            return;
+        }
+        XWeak weak = UnoRuntime.queryInterface(XWeak.class, weakImpl);
+        if (weak != null) {
+            XAdapter adapter = weak.queryAdapter();
+            if (adapter != null)
+                m_listener = new OWeakRefListener(adapter);
+        }
+    }
+
+    /**
+     * Creates an instance of this class.
+     *
+     * @param obj XWeak implementation.
+     */
+    public WeakReference(Object obj)
+    {
+        XWeak weak= UnoRuntime.queryInterface(XWeak.class, obj);
+        if (weak != null)
+        {
+            XAdapter adapter= weak.queryAdapter();
+            if (adapter != null)
+                m_listener= new OWeakRefListener(adapter);
+        }
+    }
+
+    /**
+     * Returns a hard reference to the object that is kept weak by this class.
+     *
+     * @return a hard reference to the XWeak implementation.
+     */
+    public Object get()
+    {
+        if (m_listener != null)
+            return m_listener.get();
+        return null;
+    }
+}
+
+/**
+ * Implementation of com.sun.star.uno.XReference for use with WeakReference.
+ *
+ * <p>It keeps the XAdapter implementation and registers always with it.
+ * Deregistering occurs on notification by the adapter and the adapter is
+ * released.</p>
+ */
+class OWeakRefListener implements XReference
+{
+    private XAdapter m_adapter;
+
+    /**
+     * The constructor registered this object with adapter.
+     *
+     * @param adapter the XAdapter implementation.
+     */
+    OWeakRefListener( XAdapter adapter)
+    {
+        m_adapter= adapter;
+        m_adapter.addReference(this);
+    }
+
+    /**
+     * Method of <code>com.sun.star.uno.XReference</code>.
+     *
+     * <p>When called, it deregisters this object with the adapter and releases
+     * the reference to it.</p>
+     */
+    synchronized public void dispose()
+    {
+        if (m_adapter != null)
+        {
+            m_adapter.removeReference(this);
+            m_adapter= null;
+        }
+    }
+
+    /**
+     * Obtains a hard reference to the object which is kept weak by the adapter
+     * and returns it.
+     *
+     * @return hard reference to the otherwise weakly kept object.
+     */
+    synchronized Object get()
+    {
+        Object retVal= null;
+        if (m_adapter != null)
+        {
+            retVal= m_adapter.queryAdapted();
+            if (retVal == null)
+            {
+                // If this object registered as listener with XAdapter while it was notifying
+                // the listeners then this object might not have been notified. If queryAdapted
+                // returned null then the weak kept object is dead and the listeners have already
+                // been notified. And we missed it.
+                m_adapter.removeReference(this);
+                m_adapter= null;
+            }
+        }
+        return retVal;
+    }
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */