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/******************************************************************************
*
* $Id$
*
* Copyright (C) 1997-2006 by Dimitri van Heesch.
*
* Permission to use, copy, modify, and distribute this software and its
* documentation under the terms of the GNU General Public License is hereby
* granted. No representations are made about the suitability of this software
* for any purpose. It is provided "as is" without express or implied warranty.
* See the GNU General Public License for more details.
*
* Documents produced by Doxygen are derivative works derived from the
* input used in their production; they are not affected by this license.
*
*/
#ifndef LOCKINGPTR_H
#define LOCKINGPTR_H
/*! @brief Abstract interface for lockable objects.
*
* By implementing this interface, a smart pointer can be created which
* will lock this object. This is used to prevent that an internal pointer
* owned by a lockable object would become invalid when the object is removed from
* memory, leaving the client with an invalid pointer. By letting the client use
* a smart pointer instead of the real object the object will be locked into
* memory until the pointer is no longer used, at which point the owner object will be
* unlock and can be removed from memory.
*/
class LockableObj
{
public:
LockableObj() : m_lockCount(0) {}
virtual ~LockableObj() {}
/*! Returns TRUE if the object is currently locked. */
bool isLocked() const { return m_lockCount>0; }
//VC++6.0 workaround
// protected:
/*! Called when the object is locked. */
virtual void lock() const = 0;
/*! Called when the object is unlocked. */
virtual void unlock() const = 0;
//VC++6.0 workaround
// private:
// template<class T> friend class LockingPtr;
int m_lockCount;
};
/*! @brief Smart pointer which keeps a lock on the owner of the pointer.
*
* With the pointer an owner object derived from LockableObj is associated.
* As long as the smart object exists it will keep a lock on the obj by calling
* LockableObj::lock(). Smart pointers can be copied and passed by value. As
* soon as there or no more smart pointer references to the object,
* LockableObj::unlock() will be called automatically.
*/
template<class T> class LockingPtr
{
LockableObj *m_owner;
const T *m_ptr;
public:
/*! Creates a smart pointer for pointer \a p owned by object \a o.
*/
LockingPtr(const LockableObj *o,const T* p)
{
if (o->m_lockCount==0) o->lock();
m_owner = (LockableObj *)o;
m_owner->m_lockCount++;
m_ptr = p;
}
/*! Copies the smart pointer \a lp
*/
LockingPtr(const LockingPtr &lp)
{
m_ptr = lp.m_ptr;
m_owner = lp.m_owner;
m_owner->m_lockCount++;
}
/*! Assigns the smart pointer \a lp
*/
LockingPtr &operator=(const LockingPtr &lp)
{
m_owner->m_lockCount--;
if (m_owner->m_lockCount==0) // no more references
{
m_owner->unlock();
}
m_ptr = lp.m_ptr;
m_owner = lp.m_owner;
m_owner->m_lockCount++;
return *this;
}
/*! Destroys the smart pointer, will unlock the owner.
*/
~LockingPtr()
{
m_owner->m_lockCount--;
if (m_owner->m_lockCount==0) // no more references
{
m_owner->unlock();
}
}
bool isNull() const
{
return m_ptr==0;
}
bool operator!() const
{
return !m_ptr;
}
bool operator==(T *p) const
{
return m_ptr==p;
}
bool operator==(const LockingPtr &lp) const
{
return m_ptr==lp.m_ptr;
}
bool operator!=(T *p) const
{
return m_ptr!=p;
}
bool operator!=(const LockingPtr &lp) const
{
return m_ptr!=lp.m_ptr;
}
/*! Dereference operator */
const T& operator* () const
{
return *m_ptr;
}
T* pointer() const
{
return (T*)m_ptr;
}
/*! Pointer operator */
T* operator-> () const
{
return (T*)m_ptr;
}
};
#endif // LOCKINGPTR_H
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