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132 lines
3.1 KiB
132 lines
3.1 KiB
/*
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Copyright (C) 2000-2002 Stefan Westerfeld
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stefan@space.twc.de
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Library General Public
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License as published by the Free Software Foundation; either
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version 2 of the License, or (at your option) any later version.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public License
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along with this library; see the file COPYING.LIB. If not, write to
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the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
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Boston, MA 02110-1301, USA.
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*/
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/*
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* BC - Status (2002-03-08): WeakReference(Base)
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*
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* Has to be kept binary compatible by not touching it. Add a new class if
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* you need something else.
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*/
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#ifndef MCOP_WEAKREFERENCE_H
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#define MCOP_WEAKREFERENCE_H
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#include "arts_export.h"
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namespace Arts {
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class ARTS_EXPORT WeakReferenceBase {
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public:
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virtual void release() = 0;
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};
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/**
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* The WeakReference class can be used to safely store an object, without
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* disallowing that it gets destroyed. A typical situation where you may want
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* to use this is when you implement a datastructure, where A refers B, and
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* B refers A. Using "normal" references, this structure would never get
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* freed.
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*
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* Usage example:
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*
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* Synth_WAVE_SIN sin;
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* WeakReference<Synth_PLAY_WAV> weak_sin;
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*
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* {
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* Synth_WAVE_SIN test = weak_sin;
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* if(test.isNull())
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* printf("#1 missing object\n");
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* else
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* test.start();
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* }
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*
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* // now, the strong reference leaves
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* sin = Synth_WAVE_SIN::null();
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*
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* {
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* Synth_WAVE_SIN test = weak_sin;
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* if(test.isNull())
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* printf("#2 missing object\n");
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* else
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* test.stop();
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*
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* This would output "#2 missing object".
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*
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*/
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template<class SmartWrapper>
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class WeakReference : public WeakReferenceBase
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{
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private:
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typename SmartWrapper::_base_class *content;
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public:
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WeakReference()
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{
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content = 0;
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}
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WeakReference(const WeakReference<SmartWrapper>& source)
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:WeakReferenceBase(source), content(source.content)
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{
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if(content)
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content->_addWeakReference(this);
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}
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WeakReference(SmartWrapper& source)
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{
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content = source._base();
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if(content)
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content->_addWeakReference(this);
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}
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inline WeakReference<SmartWrapper>& operator=(const
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WeakReference<SmartWrapper>& source)
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{
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release();
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content = source.content;
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if(content)
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content->_addWeakReference(this);
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return *this;
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}
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virtual ~WeakReference()
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{
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release();
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}
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void release()
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{
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if(content)
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{
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content->_removeWeakReference(this);
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content = 0;
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}
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}
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inline operator SmartWrapper() const
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{
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if(content)
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return SmartWrapper::_from_base(content->_copy());
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else
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return SmartWrapper::null();
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}
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};
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}
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#endif /* MCOP_WEAKREFERENCE_H */
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