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/****************************************************************************
**
** Copyright (C) 2012 Digia Plc and/or its subsidiary(-ies).
** Contact: http://www.qt-project.org/legal
**
** This file is part of the QtXmlPatterns module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** 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 Digia. For licensing terms and
** conditions see http://qt.digia.com/licensing. For further information
** use the contact form at http://qt.digia.com/contact-us.
**
** 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, Digia gives you certain additional
** rights. These rights are described in the Digia Qt LGPL Exception
** version 1.1, 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.
**
**
** $QT_END_LICENSE$
**
****************************************************************************/
//
// 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_OperandsIterator_H
#define Patternist_OperandsIterator_H
#include <QPair>
#include <QStack>
#include "qexpression_p.h"
QT_BEGIN_HEADER
QT_BEGIN_NAMESPACE
namespace QPatternist
{
/**
* @short A helper class that iterates a tree of Expression instances. It
* is not a sub-class of QAbstractXmlForwardIterator.
*
* The OperandsIterator delivers all Expression instances that are children at any
* depth of the Expression passed in the constructor.
* The order is delivered in a defined way, from left to right and depth
* first.
*
* @author Frans Englich <frans.englich@nokia.com>
*/
class OperandsIterator
{
/**
* The second value, the int, is the current position in the first.
*/
typedef QPair<Expression::List, int> Level;
public:
enum TreatParent
{
ExcludeParent,
IncludeParent
};
/**
* if @p treatParent is @c IncludeParent, @p start is excluded.
*
* @p start must be a valid Expression.
*/
inline OperandsIterator(const Expression::Ptr &start,
const TreatParent treatParent)
{
Q_ASSERT(start);
if(treatParent == IncludeParent)
{
Expression::List l;
l.append(start);
m_exprs.push(qMakePair(l, -1));
}
m_exprs.push(qMakePair(start->operands(), -1));
}
/**
* @short Returns the current Expression and advances the iterator.
*
* If the end has been reached, a default constructed pointer is
* returned.
*
* We intentionally return by reference.
*/
inline Expression::Ptr next()
{
if(m_exprs.isEmpty())
return Expression::Ptr();
Level &lvl = m_exprs.top();
++lvl.second;
if(lvl.second == lvl.first.size())
{
/* Resume iteration above us. */
m_exprs.pop();
if(m_exprs.isEmpty())
return Expression::Ptr();
while(true)
{
Level &previous = m_exprs.top();
++previous.second;
if(previous.second < previous.first.count())
{
const Expression::Ptr &op = previous.first.at(previous.second);
m_exprs.push(qMakePair(op->operands(), -1));
return op;
}
else
{
// We have already reached the end of this level.
m_exprs.pop();
if(m_exprs.isEmpty())
return Expression::Ptr();
}
}
}
else
{
const Expression::Ptr &op = lvl.first.at(lvl.second);
m_exprs.push(qMakePair(op->operands(), -1));
return op;
}
}
/**
* Advances this iterator by the current expression and its operands.
*/
Expression::Ptr skipOperands()
{
if(m_exprs.isEmpty())
return Expression::Ptr();
Level &lvl = m_exprs.top();
++lvl.second;
if(lvl.second == lvl.first.size())
{
/* We've reached the end of this level, at least. */
m_exprs.pop();
}
return next();
}
private:
Q_DISABLE_COPY(OperandsIterator)
QStack<Level> m_exprs;
};
}
QT_END_NAMESPACE
QT_END_HEADER
#endif
|
