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/****************************************************************************
**
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
** 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 either Technology Preview License Agreement or the
** Beta Release License Agreement.
**
** 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 1.0, included in the file LGPL_EXCEPTION.txt in this
** package.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3.0 as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL included in the
** packaging of this file. Please review the following information to
** ensure the GNU General Public License version 3.0 requirements will be
** met: http://www.gnu.org/copyleft/gpl.html.
**
** If you are unsure which license is appropriate for your use, please
** contact the sales department at http://qt.nokia.com/contact.
** $QT_END_LICENSE$
**
****************************************************************************/
//
// 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_SingletonIterator_H
#define Patternist_SingletonIterator_H
#include <QtXmlPatterns/private/qabstractxmlforwarditerator_p.h>
#include <QtXmlPatterns/private/qprimitives_p.h>
QT_BEGIN_HEADER
QT_BEGIN_NAMESPACE
namespace QPatternist
{
/**
* @short An QAbstractXmlForwardIterator over exactly one item.
*
* SingletonIterator's constructor takes one value which is
* the item it forms an QAbstractXmlForwardIterator over. Other QAbstractXmlForwardIterator instances can
* also form an QAbstractXmlForwardIterator with one in length, but by that SingletonIterator
* has this as it only task, it means it is efficient at it.
*
* Having to represent single items in Iterators is relatively common.
*
* @author Frans Englich <frans.englich@nokia.com>
* @ingroup Patternist_iterators
*/
template<typename T>
class SingletonIterator : public QAbstractXmlForwardIterator<T>
{
public:
/**
* Creates an iterator over @p item.
*
* @note item may not be @c null. Use the EmptyIterator for
* the empty sequence
*/
SingletonIterator(const T &item) : m_item(item),
m_position(0)
{
Q_ASSERT(!qIsForwardIteratorEnd(item));
}
virtual T next()
{
switch(m_position)
{
case 0:
{
++m_position;
return m_item;
}
case 1:
{
m_position = -1;
return T();
}
default:
{
Q_ASSERT(m_position == -1);
return T();
}
}
}
virtual T current() const
{
if(m_position == 1)
return m_item;
else
return T();
}
virtual xsInteger position() const
{
return m_position;
}
/**
* @returns a copy of this instance, rewinded to the beginning.
*/
virtual typename QAbstractXmlForwardIterator<T>::Ptr toReversed()
{
return typename QAbstractXmlForwardIterator<T>::Ptr(new SingletonIterator<T>(m_item));
}
/**
* @returns always 1
*/
virtual xsInteger count()
{
return 1;
}
virtual typename QAbstractXmlForwardIterator<T>::Ptr copy() const
{
return typename QAbstractXmlForwardIterator<T>::Ptr(new SingletonIterator(m_item));
}
private:
const T m_item;
qint8 m_position;
};
/**
* @short An object generator for SingletonIterator.
*
* makeSingletonIterator() is a convenience function for avoiding specifying
* the full template instantiation for SingletonIterator. Conceptually, it
* is identical to Qt's qMakePair().
*
* @relates SingletonIterator
*/
template<typename T>
inline
typename SingletonIterator<T>::Ptr
makeSingletonIterator(const T &item)
{
return typename SingletonIterator<T>::Ptr(new SingletonIterator<T>(item));
}
}
QT_END_NAMESPACE
QT_END_HEADER
#endif
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