/****************************************************************************
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** Copyright (C) 2016 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
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** This file is part of the QtXmlPatterns module of the Qt Toolkit.
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** $QT_BEGIN_LICENSE:LGPL$
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** ensure the GNU Lesser General Public License version 3 requirements
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** Alternatively, this file may be used under the terms of the GNU
** General Public License version 2.0 or (at your option) the GNU General
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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_UnionIterator_H
#define Patternist_UnionIterator_H

#include <private/qitem_p.h>

QT_BEGIN_NAMESPACE

namespace QPatternist
{
    /**
     * @short Implements the @c except operator. That is, the computation
     * of the sequence of nodes from one sequence, that doesn't appear in the
     * other.
     *
     * @ingroup Patternist_iterators
     */
    class UnionIterator : public Item::Iterator
    {
    public:
        /**
         * It is assumed that @p it1 and @p it2 are in document order and
         * without duplicates.
         */
        UnionIterator(const Item::Iterator::Ptr &it1,
                      const Item::Iterator::Ptr &it2);

        virtual Item next();
        virtual Item current() const;
        virtual xsInteger position() const;
        virtual Item::Iterator::Ptr copy() const;

    private:
        inline Item nextFromFirstOperand()
        {
            ++m_position;
            m_current = m_node1;
            m_node1 = m_it1->next();
            return m_current;
        }

        const Item::Iterator::Ptr   m_it1;
        const Item::Iterator::Ptr   m_it2;
        Item                   m_current;
        xsInteger                   m_position;
        Item                   m_node1;
        Item                   m_node2;
    };
}

QT_END_NAMESPACE

#endif
