1 files changed, 131 insertions, 0 deletions
diff --git a/mcop/weakreference.h b/mcop/weakreference.h
new file mode 100644
index 0000000..76bb381
--- /dev/null
+++ b/mcop/weakreference.h
@@ -0,0 +1,131 @@
+    /*
+
+    Copyright (C) 2000-2002 Stefan Westerfeld
+                            stefan@space.twc.de
+
+    This library is free software; you can redistribute it and/or
+    modify it under the terms of the GNU Library General Public
+    License as published by the Free Software Foundation; either
+    version 2 of the License, or (at your option) any later version.
+  
+    This library is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+    Library General Public License for more details.
+   
+    You should have received a copy of the GNU Library General Public License
+    along with this library; see the file COPYING.LIB.  If not, write to
+    the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+    Boston, MA 02111-1307, USA.
+
+    */
+
+/*
+ * BC - Status (2002-03-08): WeakReference(Base)
+ *
+ * Has to be kept binary compatible by not touching it. Add a new class if
+ * you need something else.
+ */
+
+#ifndef MCOP_WEAKREFERENCE_H
+#define MCOP_WEAKREFERENCE_H
+
+#include "arts_export.h"
+
+namespace Arts {
+
+class ARTS_EXPORT WeakReferenceBase {
+public:
+	virtual void release() = 0;
+};
+
+/**
+ * The WeakReference class can be used to safely store an object, without
+ * disallowing that it gets destroyed. A typical situation where you may want
+ * to use this is when you implement a datastructure, where A refers B, and
+ * B refers A. Using "normal" references, this structure would never get
+ * freed.
+ *
+ * Usage example:
+ *
+ *     Synth_WAVE_SIN sin;
+ *     WeakReference<Synth_PLAY_WAV> weak_sin;
+ *
+ *     {
+ *       Synth_WAVE_SIN test = weak_sin;
+ *         if(test.isNull())
+ *           printf("#1 missing object\n");
+ *         else
+ *           test.start();
+ *     }
+ *
+ *     // now, the strong reference leaves
+ *     sin = Synth_WAVE_SIN::null();
+ *
+ *     {
+ *       Synth_WAVE_SIN test = weak_sin;
+ *	     if(test.isNull())
+ *         printf("#2 missing object\n");
+ *       else
+ *         test.stop();
+ *
+ * This would output "#2 missing object".
+ *
+ */
+
+template<class SmartWrapper>
+class WeakReference : public WeakReferenceBase
+{
+private:
+	typename SmartWrapper::_base_class *content;
+
+public:
+	WeakReference()
+	{
+		content = 0;
+	}
+	WeakReference(const WeakReference<SmartWrapper>& source)
+		:WeakReferenceBase(source), content(source.content)
+	{
+		if(content)
+			content->_addWeakReference(this);
+	}
+	WeakReference(SmartWrapper& source)
+	{
+		content = source._base();
+		if(content)
+			content->_addWeakReference(this);
+	}
+	inline WeakReference<SmartWrapper>& operator=(const
+						WeakReference<SmartWrapper>& source)
+	{
+		release();
+		content = source.content;
+		if(content)
+			content->_addWeakReference(this);
+		return *this;
+	}
+	virtual ~WeakReference()
+	{
+		release();
+	}
+	void release()
+	{
+		if(content)
+		{
+			content->_removeWeakReference(this);
+			content = 0;
+		}
+	}
+	inline operator SmartWrapper() const
+	{
+		if(content)
+			return SmartWrapper::_from_base(content->_copy());
+		else
+			return SmartWrapper::null();
+	}
+};
+
+}
+
+#endif /* MCOP_WEAKREFERENCE_H */