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/* This file is part of the KDE libraries
Copyright (c) 1999 Waldo Bastian <bastian@kde.org>
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public
License version 2 as published by the Free Software Foundation.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Library General Public License for more details.
You should have received a copy of the GNU Library General Public License
along with this library; see the file COPYING.LIB. If not, write to
the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.
*/
#ifndef KSharedPTR_H
#define KSharedPTR_H
#include "kdelibs_export.h"
/**
* Reference counting for shared objects. If you derive your object
* from this class, then you may use it in conjunction with
* KSharedPtr to control the lifetime of your object.
*
* Specifically, all classes that derive from KShared have an internal
* counter keeping track of how many other objects have a reference to
* their object. If used with KSharedPtr, then your object will
* not be deleted until all references to the object have been
* released.
*
* You should probably not ever use any of the methods in this class
* directly -- let the KSharedPtr take care of that. Just derive
* your class from KShared and forget about it.
*
* @author Waldo Bastian <bastian@kde.org>
*/
class KDECORE_EXPORT KShared {
public:
/**
* Standard constructor. This will initialize the reference count
* on this object to 0.
*/
KShared() : count(0) { }
/**
* Copy constructor. This will @em not actually copy the objects
* but it will initialize the reference count on this object to 0.
*/
KShared( const KShared & ) : count(0) { }
/**
* Overloaded assignment operator.
*/
KShared &operator=(const KShared & ) { return *this; }
/**
* Increases the reference count by one.
*/
void _KShared_ref() const { count++; }
/**
* Releases a reference (decreases the reference count by one). If
* the count goes to 0, this object will delete itself.
*/
void _KShared_unref() const { if (!--count) delete this; }
/**
* Return the current number of references held.
*
* @return Number of references
*/
int _KShared_count() const { return count; }
protected:
virtual ~KShared() { }
private:
mutable int count;
};
/**
* Can be used to control the lifetime of an object that has derived
* KShared. As long a someone holds a KSharedPtr on some KShared
* object it won't become deleted but is deleted once its reference
* count is 0. This struct emulates C++ pointers virtually perfectly.
* So just use it like a simple C++ pointer.
*
* KShared and KSharedPtr are preferred over QShared / QSharedPtr
* since they are more safe.
*
* WARNING: Please note that this class template provides an implicit
* conversion to T*. Do *not* change this pointer or the pointee (don't
* call delete on it, for instance) behind KSharedPtr's back.
*
* @author Waldo Bastian <bastian@kde.org>
*/
template< class T >
class KSharedPtr
{
public:
/**
* Creates a null pointer.
*/
KSharedPtr()
: ptr(0) { }
/**
* Creates a new pointer.
* @param t the pointer
*/
KSharedPtr( T* t )
: ptr(t) { if ( ptr ) ptr->_KShared_ref(); }
/**
* Copies a pointer.
* @param p the pointer to copy
*/
KSharedPtr( const KSharedPtr& p )
: ptr(p.ptr) { if ( ptr ) ptr->_KShared_ref(); }
/**
* Unreferences the object that this pointer points to. If it was
* the last reference, the object will be deleted.
*/
~KSharedPtr() { if ( ptr ) ptr->_KShared_unref(); }
KSharedPtr<T>& operator= ( const KSharedPtr<T>& p ) {
if ( ptr == p.ptr ) return *this;
if ( ptr ) ptr->_KShared_unref();
ptr = p.ptr;
if ( ptr ) ptr->_KShared_ref();
return *this;
}
KSharedPtr<T>& operator= ( T* p ) {
if ( ptr == p ) return *this;
if ( ptr ) ptr->_KShared_unref();
ptr = p;
if ( ptr ) ptr->_KShared_ref();
return *this;
}
bool operator== ( const KSharedPtr<T>& p ) const { return ( ptr == p.ptr ); }
bool operator!= ( const KSharedPtr<T>& p ) const { return ( ptr != p.ptr ); }
bool operator== ( const T* p ) const { return ( ptr == p ); }
bool operator!= ( const T* p ) const { return ( ptr != p ); }
bool operator!() const { return ( ptr == 0 ); }
operator T*() const { return ptr; }
/**
* Returns the pointer.
* @return the pointer
*/
T* data() { return ptr; }
/**
* Returns the pointer.
* @return the pointer
*/
const T* data() const { return ptr; }
const T& operator*() const { return *ptr; }
T& operator*() { return *ptr; }
const T* operator->() const { return ptr; }
T* operator->() { return ptr; }
/**
* Returns the number of references.
* @return the number of references
*/
int count() const { return ptr->_KShared_count(); } // for debugging purposes
private:
T* ptr;
};
#endif
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