nevrax.org : docs

00001 
+00006 /* Copyright, 2001 Nevrax Ltd.
+00007  *
+00008  * This file is part of NEVRAX NEL.
+00009  * NEVRAX NEL is free software; you can redistribute it and/or modify
+00010  * it under the terms of the GNU General Public License as published by
+00011  * the Free Software Foundation; either version 2, or (at your option)
+00012  * any later version.
+00013 
+00014  * NEVRAX NEL is distributed in the hope that it will be useful, but
+00015  * WITHOUT ANY WARRANTY; without even the implied warranty of
+00016  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+00017  * General Public License for more details.
+00018 
+00019  * You should have received a copy of the GNU General Public License
+00020  * along with NEVRAX NEL; see the file COPYING. If not, write to the
+00021  * Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+00022  * MA 02111-1307, USA.
+00023  */
+00024 
+00025 #ifndef NL_READER_WRITER_H
+00026 #define NL_READER_WRITER_H
+00027 
+00028 #include "nel/misc/types_nl.h"
+00029 #include "nel/misc/mutex.h"
+00030 
+00031 
+00032 namespace NLMISC {
+00033 
+00040 class CReaderWriter
+00041 {
+00042 private:
+00043 
+00044         volatile CMutex _Fairness;
+00045         volatile CMutex _ReadersMutex;
+00046         volatile CMutex _RWMutex;
+00047         volatile sint   _ReadersLevel;
+00048 
+00049 public:
+00050 
+00051         CReaderWriter();
+00052         ~CReaderWriter();
+00053 
+00054         void                    enterReader()
+00055         {
+00056                 const_cast<CMutex&>(_Fairness).enter();
+00057                 const_cast<CMutex&>(_ReadersMutex).enter();
+00058                 ++_ReadersLevel;
+00059                 if (_ReadersLevel == 1)
+00060                         const_cast<CMutex&>(_RWMutex).enter();
+00061                 const_cast<CMutex&>(_ReadersMutex).leave();
+00062                 const_cast<CMutex&>(_Fairness).leave();
+00063         }
+00064 
+00065         void                    leaveReader()
+00066         {
+00067                 const_cast<CMutex&>(_ReadersMutex).enter();
+00068                 --_ReadersLevel;
+00069                 if (_ReadersLevel == 0)
+00070                         const_cast<CMutex&>(_RWMutex).leave();
+00071                 const_cast<CMutex&>(_ReadersMutex).leave();
+00072         }
+00073 
+00074         void                    enterWriter()
+00075         {
+00076                 const_cast<CMutex&>(_Fairness).enter();
+00077                 const_cast<CMutex&>(_RWMutex).enter();
+00078                 const_cast<CMutex&>(_Fairness).leave();
+00079         }
+00080 
+00081         void                    leaveWriter()
+00082         {
+00083                 const_cast<CMutex&>(_RWMutex).leave();
+00084         }
+00085 };
+00086 
+00093 template <class T>
+00094 class CRWSynchronized
+00095 {
+00096 public:
+00097 
+00098         class CReadAccessor
+00099         {
+00100                 CRWSynchronized<T>              *_RWSynchronized;
+00101 
+00102         public:
+00103 
+00104                 CReadAccessor(CRWSynchronized<T> *cs)
+00105                 {
+00106                         _RWSynchronized = cs;
+00107                         const_cast<CReaderWriter&>(_RWSynchronized->_RWSync).enterReader();
+00108                 }
+00109 
+00110                 ~CReadAccessor()
+00111                 {
+00112                         const_cast<CReaderWriter&>(_RWSynchronized->_RWSync).leaveReader();
+00113                 }
+00114 
+00115                 const T         &value()
+00116                 {
+00117                         return const_cast<const T&>(_RWSynchronized->_Value);
+00118                 }
+00119         };
+00120 
+00121         class CWriteAccessor
+00122         {
+00123                 CRWSynchronized<T>              *_RWSynchronized;
+00124 
+00125         public:
+00126 
+00127                 CWriteAccessor(CRWSynchronized<T> *cs)
+00128                 {
+00129                         _RWSynchronized = cs;
+00130                         const_cast<CReaderWriter&>(_RWSynchronized->_RWSync).enterWriter();
+00131                 }
+00132 
+00133                 ~CWriteAccessor()
+00134                 {
+00135                         const_cast<CReaderWriter&>(_RWSynchronized->_RWSync).leaveWriter();
+00136                 }
+00137 
+00138                 T               &value()
+00139                 {
+00140                         return const_cast<T&>(_RWSynchronized->_Value);
+00141                 }
+00142         };
+00143 
+00144 private:
+00145         friend class CRWSynchronized::CReadAccessor;
+00146         friend class CRWSynchronized::CWriteAccessor;
+00147 
+00148         volatile CReaderWriter          _RWSync;
+00149 
+00150         volatile T                                      _Value;
+00151 
+00152 };
+00153 
+00154 } // NLMISC
+00155 
+00156 
+00157 #endif // NL_READER_WRITER_H
+00158 
+00159 /* End of reader_writer.h */
+