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mmshandle.h

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00001 /***************************************************************************
00002  *   Copyright (C) 2005-2007 Stefan Schwarzer, Jens Schneider,             *
00003  *                           Matthias Hardt, Guido Madaus                  *
00004  *                                                                         *
00005  *   Copyright (C) 2007-2008 BerLinux Solutions GbR                        *
00006  *                           Stefan Schwarzer & Guido Madaus               *
00007  *                                                                         *
00008  *   Copyright (C) 2009-2013 BerLinux Solutions GmbH                       *
00009  *                                                                         *
00010  *   Authors:                                                              *
00011  *      Stefan Schwarzer   <stefan.schwarzer@diskohq.org>,                 *
00012  *      Matthias Hardt     <matthias.hardt@diskohq.org>,                   *
00013  *      Jens Schneider     <jens.schneider@diskohq.org>,                   *
00014  *      Guido Madaus       <guido.madaus@diskohq.org>,                     *
00015  *      Patrick Helterhoff <patrick.helterhoff@diskohq.org>,               *
00016  *      René Bählkow       <rene.baehlkow@diskohq.org>                     *
00017  *                                                                         *
00018  *   This library is free software; you can redistribute it and/or         *
00019  *   modify it under the terms of the GNU Lesser General Public            *
00020  *   License version 2.1 as published by the Free Software Foundation.     *
00021  *                                                                         *
00022  *   This library is distributed in the hope that it will be useful,       *
00023  *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
00024  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU     *
00025  *   Lesser General Public License for more details.                       *
00026  *                                                                         *
00027  *   You should have received a copy of the GNU Lesser General Public      *
00028  *   License along with this library; if not, write to the                 *
00029  *   Free Software Foundation, Inc.,                                       *
00030  *   51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA            *
00031  **************************************************************************/
00032 
00033 #ifndef MMSHANDLER_H_
00034 #define MMSHANDLER_H_
00035 
00036 #include "mmstools/mmsmutex.h"
00037 #include <iostream>
00038 
00039 /**
00040  * Handler class that implements reference counting.
00041  */
00042 template<class X> class MMSHandle {
00043     private:
00044         X        *data;      /**< pointer to object that shall be handled                 */
00045         int      *refCount;  /**< reference counter                                       */
00046         MMSMutex *lock;      /**< needed to make increase and decrease of refCount atomic */
00047 
00048     public:
00049         /**
00050          * Constructor
00051          */
00052         explicit MMSHandle(X* orig) : data(orig), refCount(new int(1)), lock(new MMSMutex()) {
00053         }
00054 
00055         /**
00056          * Copy constructor
00057          */
00058         MMSHandle(const MMSHandle& orig) : data(orig.data), refCount(orig.refCount), lock(orig.lock) {
00059             lock->lock();
00060             (*refCount)++;
00061             lock->unlock();
00062         }
00063 
00064         /**
00065          * Destructor
00066          */
00067         virtual ~MMSHandle() throw() {
00068             lock->lock();
00069             --(*refCount);
00070             lock->unlock();
00071             if(*refCount == 0) {
00072                 if(data) delete data;
00073                 delete refCount;
00074                 delete lock;
00075             }
00076         }
00077 
00078         /**
00079          * Overloaded -> operator.
00080          * Just returns the data object.
00081          */
00082         X* operator->() throw() {
00083             return data;
00084         }
00085 
00086         /**
00087          * Overloaded = operator.
00088          */
00089         void operator=(const MMSHandle& orig) throw() {
00090             /* do not copy if data is already the same */
00091             if(data != orig.data) {
00092                 /* free memory if reference counter is 0 */
00093                 lock->lock();
00094                 --(*refCount);
00095                 lock->unlock();
00096                 if(*refCount == 0) {
00097                     if(data) delete data;
00098                     delete refCount;
00099                     delete lock;
00100                 }
00101 
00102                 /* create a copy */
00103                 data     = orig.data;
00104                 refCount = orig.refCount;
00105                 lock     = orig.lock;
00106 
00107                 /* increase reference counter */
00108                 lock->lock();
00109                 refCount++;
00110                 lock->unlock();
00111             }
00112         }
00113 
00114         /**
00115          * Get data object.
00116          */
00117         X& operator*() const throw() {
00118             return *data;
00119         }
00120 
00121         /**
00122          * Get data object.
00123          */
00124         X* getObject() const throw() {
00125             return data;
00126         }
00127 };
00128 
00129 #endif /*MMSHANDLER_H_*/

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