18a25e0a8SAndrew Rist /************************************************************** 2cdf0e10cSrcweir * 38a25e0a8SAndrew Rist * Licensed to the Apache Software Foundation (ASF) under one 48a25e0a8SAndrew Rist * or more contributor license agreements. See the NOTICE file 58a25e0a8SAndrew Rist * distributed with this work for additional information 68a25e0a8SAndrew Rist * regarding copyright ownership. The ASF licenses this file 78a25e0a8SAndrew Rist * to you under the Apache License, Version 2.0 (the 88a25e0a8SAndrew Rist * "License"); you may not use this file except in compliance 98a25e0a8SAndrew Rist * with the License. You may obtain a copy of the License at 108a25e0a8SAndrew Rist * 118a25e0a8SAndrew Rist * http://www.apache.org/licenses/LICENSE-2.0 128a25e0a8SAndrew Rist * 138a25e0a8SAndrew Rist * Unless required by applicable law or agreed to in writing, 148a25e0a8SAndrew Rist * software distributed under the License is distributed on an 158a25e0a8SAndrew Rist * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 168a25e0a8SAndrew Rist * KIND, either express or implied. See the License for the 178a25e0a8SAndrew Rist * specific language governing permissions and limitations 188a25e0a8SAndrew Rist * under the License. 198a25e0a8SAndrew Rist * 208a25e0a8SAndrew Rist *************************************************************/ 218a25e0a8SAndrew Rist 228a25e0a8SAndrew Rist 23cdf0e10cSrcweir 24cdf0e10cSrcweir #ifndef _SALHELPER_SINGLETONREF_HXX_ 25cdf0e10cSrcweir #define _SALHELPER_SINGLETONREF_HXX_ 26cdf0e10cSrcweir 27cdf0e10cSrcweir //_______________________________________________ 28cdf0e10cSrcweir // includes 29cdf0e10cSrcweir 30cdf0e10cSrcweir #include <osl/mutex.hxx> 31cdf0e10cSrcweir #include "rtl/instance.hxx" 32cdf0e10cSrcweir #include "osl/diagnose.h" 33cdf0e10cSrcweir #include "osl/getglobalmutex.hxx" 34cdf0e10cSrcweir 35cdf0e10cSrcweir //_______________________________________________ 36cdf0e10cSrcweir // namespace 37cdf0e10cSrcweir 38cdf0e10cSrcweir namespace salhelper{ 39cdf0e10cSrcweir 40cdf0e10cSrcweir //_______________________________________________ 41cdf0e10cSrcweir // definitions 42cdf0e10cSrcweir 43cdf0e10cSrcweir /** @short template for implementing singleton classes. 44cdf0e10cSrcweir 45cdf0e10cSrcweir @descr Such classes can be instanciated everytimes they 46cdf0e10cSrcweir are needed. But the internal wrapped object will 47cdf0e10cSrcweir be created one times only. Of course its used 48cdf0e10cSrcweir resources are referenced one times only too. 49cdf0e10cSrcweir This template hold it alive till the last 50cdf0e10cSrcweir reference is gone. Further all operations 51cdf0e10cSrcweir on this reference are threadsafe. Only 52cdf0e10cSrcweir calls directly to the internal object (which modify 53cdf0e10cSrcweir its state) must be made threadsafe by the object itself 54cdf0e10cSrcweir or from outside. 55cdf0e10cSrcweir 56cdf0e10cSrcweir @attention To prevent the code against race conditions, its not 57cdf0e10cSrcweir allowed to start operations inside the ctor 5886e1cf34SPedro Giffuni of the internal wrapped object - especially operations 59cdf0e10cSrcweir which needs a reference to the same singleton too. 60cdf0e10cSrcweir 6186e1cf34SPedro Giffuni The only chance to suppress such strange constellations 62cdf0e10cSrcweir is a lazy-init mechanism. 63cdf0e10cSrcweir 64cdf0e10cSrcweir <ul> 65cdf0e10cSrcweir <li>a) The singleton class can provide a special init() 66cdf0e10cSrcweir method, which must be called as first after creation.</li> 67cdf0e10cSrcweir <li>b) The singleton class can call a special impl_init() 68cdf0e10cSrcweir method implicit for every called interface method.</li> 69cdf0e10cSrcweir </ul> 70cdf0e10cSrcweir 71cdf0e10cSrcweir Note further that this singleton pattern can work only, if 72cdf0e10cSrcweir all user of such singleton are located inside the same library! 7386e1cf34SPedro Giffuni Because static values can't be exported - e.g. from windows libraries. 74cdf0e10cSrcweir */ 75cdf0e10cSrcweir template< class SingletonClass > 76cdf0e10cSrcweir class SingletonRef 77cdf0e10cSrcweir { 78cdf0e10cSrcweir //------------------------------------------- 79cdf0e10cSrcweir // member 80cdf0e10cSrcweir 81cdf0e10cSrcweir private : 82cdf0e10cSrcweir 83cdf0e10cSrcweir /** @short pointer to the internal wrapped singleton. */ 84cdf0e10cSrcweir static SingletonClass* m_pInstance; 85cdf0e10cSrcweir 86cdf0e10cSrcweir /** @short ref count, which regulate creation and removing of m_pInstance. */ 87cdf0e10cSrcweir static sal_Int32 m_nRef; 88cdf0e10cSrcweir 89cdf0e10cSrcweir //------------------------------------------- 90cdf0e10cSrcweir // interface 91cdf0e10cSrcweir 92cdf0e10cSrcweir public : 93cdf0e10cSrcweir 94cdf0e10cSrcweir //--------------------------------------- 95cdf0e10cSrcweir 96cdf0e10cSrcweir /** @short standard ctor. 97cdf0e10cSrcweir 98cdf0e10cSrcweir @descr The internal wrapped object is created only, 99*15289133Smseidel if its ref count was 0. Otherwise this method 100cdf0e10cSrcweir does nothing ... except increasing of the internal 101cdf0e10cSrcweir ref count! 102cdf0e10cSrcweir */ SingletonRef()103cdf0e10cSrcweir SingletonRef() 104cdf0e10cSrcweir { 105cdf0e10cSrcweir // GLOBAL SAFE -> 106cdf0e10cSrcweir ::osl::MutexGuard aLock(SingletonRef::ownStaticLock()); 107cdf0e10cSrcweir 108cdf0e10cSrcweir // must be increased before(!) the check is done. 109*15289133Smseidel // Otherwise this check can fail inside the same thread ... 110cdf0e10cSrcweir ++m_nRef; 111cdf0e10cSrcweir if (m_nRef == 1) 112cdf0e10cSrcweir m_pInstance = new SingletonClass(); 113cdf0e10cSrcweir 114cdf0e10cSrcweir OSL_ENSURE(m_nRef>0 && m_pInstance, "Race? Ref count of singleton >0, but instance is NULL!"); 115cdf0e10cSrcweir // <- GLOBAL SAFE 116cdf0e10cSrcweir } 117cdf0e10cSrcweir 118cdf0e10cSrcweir //--------------------------------------- 119cdf0e10cSrcweir 120cdf0e10cSrcweir /** @short standard dtor. 121cdf0e10cSrcweir 122cdf0e10cSrcweir @descr The internal wrapped object is removed only, 123*15289133Smseidel if its ref count wil be 0. Otherwise this method 124cdf0e10cSrcweir does nothing ... except decreasing of the internal 125cdf0e10cSrcweir ref count! 126cdf0e10cSrcweir */ ~SingletonRef()127cdf0e10cSrcweir ~SingletonRef() 128cdf0e10cSrcweir { 129cdf0e10cSrcweir // GLOBAL SAFE -> 130cdf0e10cSrcweir ::osl::MutexGuard aLock(SingletonRef::ownStaticLock()); 131cdf0e10cSrcweir 132cdf0e10cSrcweir // must be decreased before(!) the check is done. 133*15289133Smseidel // Otherwise this check can fail inside the same thread ... 134cdf0e10cSrcweir --m_nRef; 135cdf0e10cSrcweir if (m_nRef == 0) 136cdf0e10cSrcweir { 137cdf0e10cSrcweir delete m_pInstance; 138cdf0e10cSrcweir m_pInstance = 0; 139cdf0e10cSrcweir } 140cdf0e10cSrcweir // <- GLOBAL SAFE 141cdf0e10cSrcweir } 142cdf0e10cSrcweir 143cdf0e10cSrcweir //--------------------------------------- 144cdf0e10cSrcweir 145cdf0e10cSrcweir /** @short Allows rSingle->someBodyOp(). 146cdf0e10cSrcweir */ operator ->() const147cdf0e10cSrcweir SingletonClass* operator->() const 148cdf0e10cSrcweir { 149cdf0e10cSrcweir // GLOBAL SAFE -> 150cdf0e10cSrcweir ::osl::MutexGuard aLock(SingletonRef::ownStaticLock()); 151cdf0e10cSrcweir return m_pInstance; 152cdf0e10cSrcweir // <- GLOBAL SAFE 153cdf0e10cSrcweir } 154cdf0e10cSrcweir 155cdf0e10cSrcweir //--------------------------------------- 156cdf0e10cSrcweir 157cdf0e10cSrcweir /** @short Allows (*rSingle).someBodyOp(). 158cdf0e10cSrcweir */ operator *() const159cdf0e10cSrcweir SingletonClass& operator*() const 160cdf0e10cSrcweir { 161cdf0e10cSrcweir // GLOBAL SAFE -> 162cdf0e10cSrcweir ::osl::MutexGuard aLock(SingletonRef::ownStaticLock()); 163cdf0e10cSrcweir return *m_pInstance; 164cdf0e10cSrcweir // <- GLOBAL SAFE 165cdf0e10cSrcweir } 166cdf0e10cSrcweir 167cdf0e10cSrcweir //------------------------------------------- 168cdf0e10cSrcweir // helper 169cdf0e10cSrcweir 170cdf0e10cSrcweir private : 171cdf0e10cSrcweir 172cdf0e10cSrcweir //--------------------------------------- 173cdf0e10cSrcweir 174cdf0e10cSrcweir /** @short creates an own mutex for guarding static contents. 175cdf0e10cSrcweir 176cdf0e10cSrcweir @descr The global mutex the osl library is used one times 177cdf0e10cSrcweir only to create an own static mutex, which can be used 178cdf0e10cSrcweir next time to guard own static member operations. 179cdf0e10cSrcweir */ 180cdf0e10cSrcweir struct SingletonLockInit 181cdf0e10cSrcweir { operator ()salhelper::SingletonRef::SingletonLockInit182cdf0e10cSrcweir ::osl::Mutex* operator()() 183cdf0e10cSrcweir { 184cdf0e10cSrcweir static ::osl::Mutex aInstance; 185cdf0e10cSrcweir return &aInstance; 186cdf0e10cSrcweir } 187cdf0e10cSrcweir }; 188cdf0e10cSrcweir ownStaticLock() const189cdf0e10cSrcweir ::osl::Mutex& ownStaticLock() const 190cdf0e10cSrcweir { 191cdf0e10cSrcweir return *rtl_Instance< ::osl::Mutex, 192cdf0e10cSrcweir SingletonLockInit, 193cdf0e10cSrcweir ::osl::MutexGuard, 194cdf0e10cSrcweir ::osl::GetGlobalMutex >::create(SingletonLockInit(), ::osl::GetGlobalMutex()); 195cdf0e10cSrcweir } 196cdf0e10cSrcweir }; 197cdf0e10cSrcweir 198cdf0e10cSrcweir template< class SingletonClass > 199cdf0e10cSrcweir SingletonClass* SingletonRef< SingletonClass >::m_pInstance = 0; 200cdf0e10cSrcweir 201cdf0e10cSrcweir template< class SingletonClass > 202cdf0e10cSrcweir sal_Int32 SingletonRef< SingletonClass >::m_nRef = 0; 203cdf0e10cSrcweir 204cdf0e10cSrcweir } // namespace salhelper 205cdf0e10cSrcweir 206cdf0e10cSrcweir #endif // _SALHELPER_SINGLETONREF_HXX_ 207