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/*
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 */
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