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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., 51 Franklin Street, Fifth Floor,
+ Boston, MA 02110-1301, USA.
+*/
+#ifndef KSharedPTR_H
+#define KSharedPTR_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>
+ * @version $Id: ksharedptr.h,v 1.23 2004/02/04 12:16:03 raabe Exp $
+ */
+class 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>
+ * @version $Id: ksharedptr.h,v 1.23 2004/02/04 12:16:03 raabe Exp $
+ */
+template< class T >
+struct 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