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/****************************************************************************
**
** Copyright (C) 2021 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the QtXmlPatterns module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:COMM$
**
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** $QT_END_LICENSE$
**
**
**
**
**
**
**
**
**
**
**
**
**
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**
**
****************************************************************************/
//
// 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 <private/qabstractxmlforwarditerator_p.h>
#include <private/qprimitives_p.h>
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
#endif
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