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/****************************************************************************
**
** 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 examples 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.
**
**
**
**
**
**
**
**
** $QT_END_LICENSE$
**
****************************************************************************/
#include "randomlistmodel.h"
#include <stdlib.h>
static const int bufferSize(500);
static const int lookAhead(100);
static const int halfLookAhead(lookAhead/2);
RandomListModel::RandomListModel(QObject *parent)
: QAbstractListModel(parent), m_rows(bufferSize), m_count(10000)
{
}
RandomListModel::~RandomListModel()
{
}
int RandomListModel::rowCount(const QModelIndex &) const
{
return m_count;
}
//! [0]
QVariant RandomListModel::data(const QModelIndex &index, int role) const
{
if (role != Qt::DisplayRole)
return QVariant();
int row = index.row();
if (row > m_rows.lastIndex()) {
if (row - m_rows.lastIndex() > lookAhead)
cacheRows(row-halfLookAhead, qMin(m_count, row+halfLookAhead));
else while (row > m_rows.lastIndex())
m_rows.append(fetchRow(m_rows.lastIndex()+1));
} else if (row < m_rows.firstIndex()) {
if (m_rows.firstIndex() - row > lookAhead)
cacheRows(qMax(0, row-halfLookAhead), row+halfLookAhead);
else while (row < m_rows.firstIndex())
m_rows.prepend(fetchRow(m_rows.firstIndex()-1));
}
return m_rows.at(row);
}
void RandomListModel::cacheRows(int from, int to) const
{
for (int i = from; i <= to; ++i)
m_rows.insert(i, fetchRow(i));
}
//![0]
//![1]
QString RandomListModel::fetchRow(int position) const
{
return QString::number(rand() % ++position);
}
//![1]
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