1 /************************************************************************* 2 * 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * Copyright 2000, 2010 Oracle and/or its affiliates. 6 * 7 * OpenOffice.org - a multi-platform office productivity suite 8 * 9 * This file is part of OpenOffice.org. 10 * 11 * OpenOffice.org is free software: you can redistribute it and/or modify 12 * it under the terms of the GNU Lesser General Public License version 3 13 * only, as published by the Free Software Foundation. 14 * 15 * OpenOffice.org is distributed in the hope that it will be useful, 16 * but WITHOUT ANY WARRANTY; without even the implied warranty of 17 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 18 * GNU Lesser General Public License version 3 for more details 19 * (a copy is included in the LICENSE file that accompanied this code). 20 * 21 * You should have received a copy of the GNU Lesser General Public License 22 * version 3 along with OpenOffice.org. If not, see 23 * <http://www.openoffice.org/license.html> 24 * for a copy of the LGPLv3 License. 25 * 26 ************************************************************************/ 27 28 using System; 29 using unoidl.com.sun.star.uno; 30 using unoidl.com.sun.star.lang; 31 32 namespace uno.util 33 { 34 35 /** An XAdapter implementation that holds a weak reference 36 (System.WeakReference) to an object. 37 Clients can register listeners (unoidl.com.sun.star.lang.XReference) 38 which are notified when the object (the one which is kept weak) is 39 being finalized. That is, that object is being destroyed because there 40 are not any hard references to it. 41 */ 42 public class WeakAdapter : XAdapter 43 { 44 // references the XWeak implementation 45 private WeakReference m_weakRef; 46 // contains XReference objects registered by addReference 47 private delegate void XReference_dispose(); 48 private XReference_dispose m_XReference_dispose; 49 50 /** ctor. 51 52 @param obj the object that is to be held weakly 53 */ 54 public WeakAdapter( Object obj ) 55 { 56 m_weakRef = new WeakReference( obj ); 57 m_XReference_dispose = null; 58 } 59 60 /** Called by the XWeak implementation (WeakBase) when it is being 61 finalized. It is only being called once. 62 The registererd XReference listeners are notified. On notification 63 they are to unregister themselves. The notification is thread-safe. 64 However, it is possible to add a listener during the notification 65 process, which will never receive a notification. 66 To prevent this, one would have to synchronize this method with 67 the addReference method. But this can result in deadlocks in a 68 multithreaded environment. 69 */ 70 internal /* non-virtual */ void referentDying() 71 { 72 XReference_dispose call; 73 lock (this) 74 { 75 call = m_XReference_dispose; 76 m_XReference_dispose = null; 77 } 78 if (null != call) 79 call(); 80 } 81 82 // XAdapter impl 83 84 /** Called to obtain a hard reference o the object which is kept weakly 85 by this instance. 86 87 @return hard reference to the object 88 */ 89 public Object queryAdapted() 90 { 91 return m_weakRef.Target; 92 } 93 /** Called by clients to register listener which are notified when the 94 weak object is dying. 95 96 @param xReference a listener 97 */ 98 public void removeReference( XReference xReference ) 99 { 100 lock (this) 101 { 102 m_XReference_dispose -= 103 new XReference_dispose( xReference.dispose ); 104 } 105 } 106 /** Called by clients to unregister listeners. 107 108 @param xReference a listener 109 */ 110 public void addReference( XReference xReference ) 111 { 112 lock (this) 113 { 114 m_XReference_dispose += 115 new XReference_dispose( xReference.dispose ); 116 } 117 } 118 } 119 120 } 121