Question

这里是qguardedptr.h包含文件的所有文本，一字不差。它仅仅用来说明，版权由Trolltech保留。

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/****************************************************************************
** $Id$
**
** Definition of QGuardedPtr class
**
** Created : 990929
**
** Copyright (C) 1992-2000 Trolltech AS.  All rights reserved.
**
** This file is part of the kernel module of the Qt GUI Toolkit.
**
** This file may be distributed under the terms of the Q Public License
** as defined by Trolltech AS of Norway and appearing in the file
** LICENSE.QPL included in the packaging of this file.
**
** This file may be distributed and/or modified under the terms of the
** GNU General Public License version 2 as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL included in the
** packaging of this file.
**
** Licensees holding valid Qt Enterprise Edition or Qt Professional Edition
** licenses may use this file in accordance with the Qt Commercial License
** Agreement provided with the Software.
**
** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
**
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**   information about Qt Commercial License Agreements.
** See http://www.trolltech.com/qpl/ for QPL licensing information.
** See http://www.trolltech.com/gpl/ for GPL licensing information.
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**********************************************************************/

#ifndef QGUARDEDPTR_H
#define QGUARDEDPTR_H

#ifndef QT_H
#include "qobject.h"
#endif // QT_H

class Q_EXPORT QGuardedPtrPrivate : public QObject, public QShared
{
    Q_OBJECT
public:
    QGuardedPtrPrivate( QObject* );
    ~QGuardedPtrPrivate();

    QObject* object() const;
    void reconnect( QObject* );

private slots:
    void objectDestroyed();

private:
    QObject* obj;
};

template <class T>
class QGuardedPtr
{
public:
    QGuardedPtr() : priv( new QGuardedPtrPrivate( 0 ) ) {}

    QGuardedPtr( T* o) {
	priv = new QGuardedPtrPrivate( (QObject*)o );
    }

    QGuardedPtr(const QGuardedPtr<T> &p) {
	priv = p.priv;
	ref();
    }

    ~QGuardedPtr() { deref(); }

    QGuardedPtr<T> &operator=(const QGuardedPtr<T> &p) {
	if ( priv != p.priv ) {
	    deref();
	    priv = p.priv;
	    ref();
	}
	return *this;
    }

    QGuardedPtr<T> &operator=(T* o) {
	if ( priv->count == 1 ) {
	    priv->reconnect( (QObject*)o );
	} else {
	    deref();
	    priv = new QGuardedPtrPrivate( (QObject*)o );
	}
	return *this;
    }

    bool operator==( const QGuardedPtr<T> &p ) const {
	return priv->object() == p.priv->object();
    }

    bool operator!= ( const QGuardedPtr<T>& p ) const {
	return !( *this == p );
    }

    bool isNull() const { return !priv->object(); }

    T* operator->() const { return (T*) priv->object(); }

    T& operator*() const { return *( (T*)priv->object() ); }

    operator T*() const { return (T*) priv->object(); }

private:

    void ref() { priv->ref(); }

    void deref() {
	if ( priv->deref() )
	    delete priv;
    }

    QGuardedPtrPrivate* priv;
};




inline QObject* QGuardedPtrPrivate::object() const
{
    return obj;
}


#endif