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////////////////////////////////////////////////////////////////////////////////
// The Loki Library
// Copyright (c) 2001 by Andrei Alexandrescu
// This code is from the article:
// "Generic<Programming>: volatile Multithreaded Programmers Best Friend
// Volatile-Correctness or How to Have Your Compiler Detect Race Conditions
// for You" by Alexandrescu, Andrei.
// Published in the February 2001 issue of the C/C++ Users Journal.
// http://www.cuj.com/documents/s=7998/cujcexp1902alexandr/
// Prepared for Loki library by Richard Sposato
////////////////////////////////////////////////////////////////////////////////
// $Header: /cvsroot/loki-lib/loki/include/loki/LockingPtr.h,v 1.11 2006/03/08 18:22:42 syntheticpp Exp $
#ifndef LOKI_LOCKING_PTR_INC_
#define LOKI_LOCKING_PTR_INC_
#include <loki/ConstPolicy.h>
namespace Loki
{
/** @class LockingPtr
Locks a volatile object and casts away volatility so that the object
can be safely used in a single-threaded region of code.
Original version of LockingPtr had only one template - for the shared
object, but not the mutex type. This version allows users to specify a
the mutex type as a LockingPolicy class. The only requirements for a
LockingPolicy class are to provide Lock and Unlock methods.
*/
template < typename SharedObject, typename LockingPolicy = LOKI_DEFAULT_MUTEX,
template<class> class ConstPolicy = LOKI_DEFAULT_CONSTNESS >
class LockingPtr
{
public:
typedef typename ConstPolicy<SharedObject>::Type ConstOrNotType;
/** Constructor locks mutex associated with an object.
@param object Reference to object.
@param mutex Mutex used to control thread access to object.
*/
LockingPtr( volatile ConstOrNotType & object, LockingPolicy & mutex )
: pObject_( const_cast< SharedObject * >( &object ) ),
pMutex_( &mutex )
{
mutex.Lock();
}
/// Destructor unlocks the mutex.
~LockingPtr()
{
pMutex_->Unlock();
}
/// Star-operator dereferences pointer.
ConstOrNotType & operator * ()
{
return *pObject_;
}
/// Point-operator returns pointer to object.
ConstOrNotType * operator -> ()
{
return pObject_;
}
private:
/// Default constructor is not implemented.
LockingPtr();
/// Copy-constructor is not implemented.
LockingPtr( const LockingPtr & );
/// Copy-assignment-operator is not implemented.
LockingPtr & operator = ( const LockingPtr & );
/// Pointer to the shared object.
ConstOrNotType * pObject_;
/// Pointer to the mutex.
LockingPolicy * pMutex_;
}; // end class LockingPtr
} // namespace Loki
#endif // end file guardian
// $Log: LockingPtr.h,v $
// Revision 1.11 2006/03/08 18:22:42 syntheticpp
// doxygen fixes
//
// Revision 1.10 2006/02/20 21:45:40 rich_sposato
// Removed struct Locking - no longer needed.
//
// Revision 1.9 2006/02/19 22:04:28 rich_sposato
// Moved Const-policy structs from SmartPtr.h to ConstPolicy.h.
//
// Revision 1.8 2006/01/30 20:33:01 syntheticpp
// use policies from SmartPtr.h, clean up
//
// Revision 1.7 2006/01/22 13:37:33 syntheticpp
// use macro LOKI_DEFAULT_MUTEX for Mutex default value, defined in Threads.h
//
// Revision 1.6 2006/01/21 14:09:09 syntheticpp
// replace LockPtr/ConstLockPtr implementation with a template policy based one
//
// Revision 1.5 2006/01/21 01:02:12 rich_sposato
// Added Mutex class to Loki. Made it the default policy class for locking.
//
// Revision 1.4 2006/01/19 19:34:19 rich_sposato
// Added ConstLockingPtr class.
//
// Revision 1.3 2006/01/16 18:34:37 rich_sposato
// Changed return type from LockingPtr to SharedObject.
//
// Revision 1.2 2006/01/14 00:20:10 syntheticpp
// remove c&p error
//
// Revision 1.1 2005/11/19 22:00:23 rich_sposato
// Adding LockingPtr class to Loki project.
//
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