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151 lines
3.2 KiB
C++
151 lines
3.2 KiB
C++
// NeL - MMORPG Framework <http://dev.ryzom.com/projects/nel/>
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// Copyright (C) 2010 Winch Gate Property Limited
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Affero General Public License as
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// published by the Free Software Foundation, either version 3 of the
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// License, or (at your option) any later version.
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//
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// This program 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
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// GNU Affero General Public License for more details.
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//
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// You should have received a copy of the GNU Affero General Public License
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// along with this program. If not, see <http://www.gnu.org/licenses/>.
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#ifndef NL_READER_WRITER_H
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#define NL_READER_WRITER_H
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#include "types_nl.h"
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#include "mutex.h"
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namespace NLMISC {
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/**
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* This class allows a reader/writer ressource usage policy.
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* \author Benjamin Legros
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* \author Nevrax France
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* \date 2001
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*/
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class CReaderWriter
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{
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private:
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volatile CMutex _Fairness;
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volatile CMutex _ReadersMutex;
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volatile CMutex _RWMutex;
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volatile sint _ReadersLevel;
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public:
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CReaderWriter();
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~CReaderWriter();
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void enterReader()
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{
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const_cast<CMutex&>(_Fairness).enter();
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const_cast<CMutex&>(_ReadersMutex).enter();
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++_ReadersLevel;
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if (_ReadersLevel == 1)
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const_cast<CMutex&>(_RWMutex).enter();
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const_cast<CMutex&>(_ReadersMutex).leave();
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const_cast<CMutex&>(_Fairness).leave();
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}
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void leaveReader()
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{
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const_cast<CMutex&>(_ReadersMutex).enter();
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--_ReadersLevel;
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if (_ReadersLevel == 0)
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const_cast<CMutex&>(_RWMutex).leave();
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const_cast<CMutex&>(_ReadersMutex).leave();
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}
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void enterWriter()
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{
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const_cast<CMutex&>(_Fairness).enter();
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const_cast<CMutex&>(_RWMutex).enter();
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const_cast<CMutex&>(_Fairness).leave();
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}
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void leaveWriter()
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{
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const_cast<CMutex&>(_RWMutex).leave();
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}
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};
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/**
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* This class uses a CReaderWriter object to implement a synchronized object (see mutex.h for standard CSynchronized.)
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* \author Benjamin Legros
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* \author Nevrax France
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* \date 2001
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*/
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template <class T>
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class CRWSynchronized
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{
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public:
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class CReadAccessor
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{
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CRWSynchronized<T> *_RWSynchronized;
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public:
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CReadAccessor(CRWSynchronized<T> *cs)
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{
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_RWSynchronized = cs;
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const_cast<CReaderWriter&>(_RWSynchronized->_RWSync).enterReader();
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}
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~CReadAccessor()
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{
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const_cast<CReaderWriter&>(_RWSynchronized->_RWSync).leaveReader();
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}
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const T &value()
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{
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return const_cast<const T&>(_RWSynchronized->_Value);
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}
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};
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class CWriteAccessor
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{
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CRWSynchronized<T> *_RWSynchronized;
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public:
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CWriteAccessor(CRWSynchronized<T> *cs)
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{
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_RWSynchronized = cs;
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const_cast<CReaderWriter&>(_RWSynchronized->_RWSync).enterWriter();
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}
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~CWriteAccessor()
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{
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const_cast<CReaderWriter&>(_RWSynchronized->_RWSync).leaveWriter();
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}
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T &value()
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{
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return const_cast<T&>(_RWSynchronized->_Value);
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}
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};
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private:
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friend class CRWSynchronized::CReadAccessor;
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friend class CRWSynchronized::CWriteAccessor;
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volatile CReaderWriter _RWSync;
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volatile T _Value;
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};
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} // NLMISC
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#endif // NL_READER_WRITER_H
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/* End of reader_writer.h */
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