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instance.h

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00001 // Copyright (C) 2001 Open Source Telecom Corporation.
00002 //  
00003 // This program is free software; you can redistribute it and/or modify
00004 // it under the terms of the GNU General Public License as published by
00005 // the Free Software Foundation; either version 2 of the License, or
00006 // (at your option) any later version.
00007 // 
00008 // This program is distributed in the hope that it will be useful,
00009 // but WITHOUT ANY WARRANTY; without even the implied warranty of
00010 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00011 // GNU General Public License for more details.
00012 // 
00013 // You should have received a copy of the GNU General Public License
00014 // along with this program; if not, write to the Free Software 
00015 // Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
00016 // 
00017 // As a special exception to the GNU General Public License, permission is 
00018 // granted for additional uses of the text contained in its release 
00019 // of Common C++.
00020 // 
00021 // The exception is that, if you link the Common C++ library with other
00022 // files to produce an executable, this does not by itself cause the
00023 // resulting executable to be covered by the GNU General Public License.
00024 // Your use of that executable is in no way restricted on account of
00025 // linking the Common C++ library code into it.
00026 // 
00027 // This exception does not however invalidate any other reasons why
00028 // the executable file might be covered by the GNU General Public License.
00029 // 
00030 // This exception applies only to the code released under the 
00031 // name Common C++.  If you copy code from other releases into a copy of
00032 // Common C++, as the General Public License permits, the exception does
00033 // not apply to the code that you add in this way.  To avoid misleading
00034 // anyone as to the status of such modified files, you must delete
00035 // this exception notice from them.
00036 // 
00037 // If you write modifications of your own for Common C++, it is your choice
00038 // whether to permit this exception to apply to your modifications.
00039 // If you do not wish that, delete this exception notice.  
00040 
00041 namespace ost {
00042 
00043 template <class T>
00044 class Instance : private RWLock
00045 {
00046 protected:
00047         static T* objPointer;
00048         unsigned objCount;
00049         bool objPurge;
00050         
00051         Instance()
00052         {
00053                 WriteLock();
00054                 if(objPointer)
00055                 {
00056                         if(objPointer->objCount)
00057                                 objPointer->objPurge = true;
00058                         else            
00059                                 delete objPointer;
00060                 }
00061                 objPointer = this;
00062                 objCount = 0;
00063                 objPurge = false;
00064                 Unlock();
00065         }
00066 public:
00067         static T *getInstance(void);
00068         
00069         void endInstance()
00070         {       
00071                 --objcount;
00072                 if(!objCount && objPurge)
00073                         delete this;
00074         }               
00075 };
00076 
00077 template <class T>
00078 T *Instance<T>::objPointer = NULL;
00079 
00080 template <class T>
00081 T *Instance<T>::getInstance(void)
00082 {
00083         Instance<T> *ptr;
00084         ReadLock();
00085         ptr = Instance<T>::objPointer;
00086         ptr->objCount++;
00087         Unlock();
00088         return <T *>ptr;
00089 }
00090 
00091 
00092 };

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