/****************************************************************************

**

** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).

** All rights reserved.

** Contact: Nokia Corporation (qt-info@nokia.com)

**

** This file is part of the QtXmlPatterns module of the Qt Toolkit.

**

** $QT_BEGIN_LICENSE:LGPL$

** No Commercial Usage

** This file contains pre-release code and may not be distributed.

** You may use this file in accordance with the terms and conditions

** contained in the Technology Preview License Agreement accompanying

** this package.

**

** GNU Lesser General Public License Usage

** Alternatively, this file may be used under the terms of the GNU Lesser

** General Public License version 2.1 as published by the Free Software

** Foundation and appearing in the file LICENSE.LGPL included in the

** packaging of this file.  Please review the following information to

** ensure the GNU Lesser General Public License version 2.1 requirements

** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.

**

** In addition, as a special exception, Nokia gives you certain additional

** rights.  These rights are described in the Nokia Qt LGPL Exception

** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.

**

** If you have questions regarding the use of this file, please contact

** Nokia at qt-info@nokia.com.

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**

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** $QT_END_LICENSE$

**

****************************************************************************/

//

//  W A R N I N G

//  -------------

//

// This file is not part of the Qt API.  It exists purely as an

// implementation detail.  This header file may change from version to

// version without notice, or even be removed.

//

// We mean it.

#ifndef Patternist_EmptyIterator_H

#define Patternist_EmptyIterator_H

#include "qabstractxmlforwarditerator_p.h"

#include "qprimitives_p.h"

QT_BEGIN_HEADER

QT_BEGIN_NAMESPACE

namespace QPatternist

{

    /**

     * @short An QAbstractXmlForwardIterator which always is empty.

     *

     * EmptyIterator is an QAbstractXmlForwardIterator over the type @c T, which always is empty. Other

     * iterators can also be empty(or, at least behave as they are empty), but this

     * class is special designed for this purpose and is therefore fast.

     *

     * EmptyIterator's constructor is protected, instances is retrieved from CommonValues.

     *

     * @author Frans Englich <frans.englich@nokia.com>

     * @ingroup Patternist_iterators

     */

    template<typename T> class EmptyIterator : public QAbstractXmlForwardIterator<T>

    {

    public:

        /**

         * @returns always a default constructed value, T().

         */

        virtual T next()

        {

            return T();

        }

        /**

         * @returns always a default constructed value, T().

         */

        virtual T current() const

        {

            return T();

        }

        /**

         * @returns always 0.

         */

        virtual xsInteger position() const

        {

            return 0;

        }

        /**

         * @returns always @c this, the reverse of <tt>()</tt> is <tt>()</tt>.

         */

        virtual typename QAbstractXmlForwardIterator<T>::Ptr toReversed()

        {

            return typename QAbstractXmlForwardIterator<T>::Ptr(const_cast<EmptyIterator<T> *>(this));

        }

        /**

         * @returns always 0

         */

        virtual xsInteger count()

        {

            return 0;

        }

        /**

         * @returns @c this

         */

        virtual typename QAbstractXmlForwardIterator<T>::Ptr copy() const

        {

            return typename QAbstractXmlForwardIterator<T>::Ptr(const_cast<EmptyIterator *>(this));

        }

    protected:

        friend class CommonValues;

    };

    template<typename T>

    static inline

    typename QAbstractXmlForwardIterator<T>::Ptr

    makeEmptyIterator()

    {

        return typename QAbstractXmlForwardIterator<T>::Ptr(new EmptyIterator<T>());

    }

}

QT_END_NAMESPACE

QT_END_HEADER

#endif