25ce12a718
git-svn-id: svn://svn.code.sf.net/p/loki-lib/code/trunk@840 7ec92016-0320-0410-acc4-a06ded1c099a
110 lines
3.7 KiB
C++
110 lines
3.7 KiB
C++
////////////////////////////////////////////////////////////////////////////////
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// The Loki Library
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// Copyright (c) 2001 by Andrei Alexandrescu
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// This code is from the article:
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// "Generic<Programming>: volatile — Multithreaded Programmer’s Best Friend
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// Volatile-Correctness or How to Have Your Compiler Detect Race Conditions
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// for You" by Alexandrescu, Andrei.
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// Published in the February 2001 issue of the C/C++ Users Journal.
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// http://www.cuj.com/documents/s=7998/cujcexp1902alexandr/
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// Permission to use, copy, modify, distribute and sell this software for any
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// purpose is hereby granted without fee, provided that the above copyright
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// notice appear in all copies and that both that copyright notice and this
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// permission notice appear in supporting documentation.
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// The author makes no representations about the
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// suitability of this software for any purpose. It is provided "as is"
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// without express or implied warranty.
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// Prepared for Loki library by Richard Sposato
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////////////////////////////////////////////////////////////////////////////////
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#ifndef LOKI_LOCKING_PTR_INC_
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#define LOKI_LOCKING_PTR_INC_
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// $Id$
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#include <loki/ConstPolicy.h>
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#include <loki/Threads.h>
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namespace Loki
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{
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/** @class LockingPtr
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Locks a volatile object and casts away volatility so that the object
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can be safely used in a single-threaded region of code.
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Original version of LockingPtr had only one template - for the shared
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object, but not the mutex type. This version allows users to specify a
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the mutex type as a LockingPolicy class. The only requirements for a
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LockingPolicy class are to provide Lock and Unlock methods.
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*/
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template < typename SharedObject, typename LockingPolicy = LOKI_DEFAULT_MUTEX,
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template<class> class ConstPolicy = LOKI_DEFAULT_CONSTNESS >
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class LockingPtr
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{
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public:
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typedef typename ConstPolicy<SharedObject>::Type ConstOrNotType;
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/** Constructor locks mutex associated with an object.
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@param object Reference to object.
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@param mutex Mutex used to control thread access to object.
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*/
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LockingPtr( volatile ConstOrNotType & object, LockingPolicy & mutex )
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: pObject_( const_cast< SharedObject * >( &object ) ),
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pMutex_( &mutex )
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{
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mutex.Lock();
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}
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typedef typename std::pair<volatile ConstOrNotType *, LockingPolicy *> Pair;
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/** Constructor locks mutex associated with an object.
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@param lockpair a std::pair of pointers to the object and the mutex
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*/
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LockingPtr( Pair lockpair )
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: pObject_( const_cast< SharedObject * >( lockpair.first ) ),
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pMutex_( lockpair.second )
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{
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lockpair.second->Lock();
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}
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/// Destructor unlocks the mutex.
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~LockingPtr()
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{
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pMutex_->Unlock();
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}
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/// Star-operator dereferences pointer.
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ConstOrNotType & operator * ()
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{
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return *pObject_;
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}
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/// Point-operator returns pointer to object.
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ConstOrNotType * operator -> ()
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{
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return pObject_;
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}
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private:
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/// Default constructor is not implemented.
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LockingPtr();
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/// Copy-constructor is not implemented.
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LockingPtr( const LockingPtr & );
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/// Copy-assignment-operator is not implemented.
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LockingPtr & operator = ( const LockingPtr & );
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/// Pointer to the shared object.
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ConstOrNotType * pObject_;
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/// Pointer to the mutex.
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LockingPolicy * pMutex_;
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}; // end class LockingPtr
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} // namespace Loki
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#endif // end file guardian
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