cli_ure/source/ure/uno/util/WeakAdapter.cs

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  30
  31 using System;
  32 using unoidl.com.sun.star.uno;
  33 using unoidl.com.sun.star.lang;
  34
  35 namespace uno.util
  36 {
  37
  38 /** An XAdapter implementation that holds a weak reference
  39     (System.WeakReference) to an object.
  40     Clients can register listeners (unoidl.com.sun.star.lang.XReference)
  41     which are notified when the object (the one which is kept weak) is
  42     being finalized.  That is, that object is being destroyed because there
  43     are not any hard references to it.
  44 */
  45 public class WeakAdapter : XAdapter
  46 {
  47     // references the XWeak implementation
  48     private WeakReference m_weakRef;
  49     // contains XReference objects registered by addReference
  50     private delegate void XReference_dispose();
  51     private XReference_dispose m_XReference_dispose;
  52
  53     /** ctor.
  54
  55         @param obj the object that is to be held weakly
  56     */
  57     public WeakAdapter( Object obj )
  58     {
  59         m_weakRef = new WeakReference( obj );
  60         m_XReference_dispose = null;
  61     }
  62
  63     /** Called by the XWeak implementation (WeakBase) when it is being
  64         finalized.  It is only being called once.
  65         The registererd XReference listeners are notified. On notification
  66         they are  to unregister themselves. The notification is thread-safe.
  67         However, it is possible to add a listener during the notification
  68         process, which will never receive a notification.
  69         To prevent this, one would have to synchronize this method with
  70         the addReference method. But this can result in deadlocks in a
  71         multithreaded environment.
  72     */
  73     internal /* non-virtual */ void referentDying()
  74     {
  75         XReference_dispose call;
  76         lock (this)
  77         {
  78             call = m_XReference_dispose;
  79             m_XReference_dispose = null;
  80         }
  81         if (null != call)
  82             call();
  83     }
  84
  85     // XAdapter impl
  86
  87     /** Called to obtain a hard reference o the object which is kept weakly
  88         by this instance.
  89
  90         @return hard reference to the object
  91     */
  92     public Object queryAdapted()
  93     {
  94         return m_weakRef.Target;
  95     }
  96     /** Called by clients to register listener which are notified when the
  97         weak object is dying.
  98
  99         @param xReference a listener
 100     */
 101     public void removeReference( XReference xReference )
 102     {
 103         lock (this)
 104         {
 105             m_XReference_dispose -=
 106                 new XReference_dispose( xReference.dispose );
 107         }
 108     }
 109     /** Called by clients to unregister listeners.
 110
 111         @param xReference a listener
 112     */
 113     public void addReference( XReference xReference )
 114     {
 115         lock (this)
 116         {
 117             m_XReference_dispose +=
 118                 new XReference_dispose( xReference.dispose );
 119         }
 120     }
 121 }
 122
 123 }