97 lines
3.4 KiB
C++
97 lines
3.4 KiB
C++
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/****************************************************************************
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**
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** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
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** All rights reserved.
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** Contact: Nokia Corporation (qt-info@nokia.com)
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**
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** This file is part of the examples of the Qt Toolkit.
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**
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** $QT_BEGIN_LICENSE:BSD$
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** You may use this file under the terms of the BSD license as follows:
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**
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** "Redistribution and use in source and binary forms, with or without
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** modification, are permitted provided that the following conditions are
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** met:
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** * Redistributions of source code must retain the above copyright
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** notice, this list of conditions and the following disclaimer.
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** * Redistributions in binary form must reproduce the above copyright
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** notice, this list of conditions and the following disclaimer in
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** the documentation and/or other materials provided with the
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** distribution.
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** * Neither the name of Nokia Corporation and its Subsidiary(-ies) nor
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** the names of its contributors may be used to endorse or promote
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** products derived from this software without specific prior written
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** permission.
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**
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** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
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** $QT_END_LICENSE$
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**
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****************************************************************************/
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#include "randomlistmodel.h"
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#include <stdlib.h>
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static const int bufferSize(500);
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static const int lookAhead(100);
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static const int halfLookAhead(lookAhead/2);
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RandomListModel::RandomListModel(QObject *parent)
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: QAbstractListModel(parent), m_rows(bufferSize), m_count(10000)
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{
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}
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RandomListModel::~RandomListModel()
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{
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}
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int RandomListModel::rowCount(const QModelIndex &) const
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{
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return m_count;
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}
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//! [0]
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QVariant RandomListModel::data(const QModelIndex &index, int role) const
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{
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if (role != Qt::DisplayRole)
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return QVariant();
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int row = index.row();
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if (row > m_rows.lastIndex()) {
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if (row - m_rows.lastIndex() > lookAhead)
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cacheRows(row-halfLookAhead, qMin(m_count, row+halfLookAhead));
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else while (row > m_rows.lastIndex())
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m_rows.append(fetchRow(m_rows.lastIndex()+1));
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} else if (row < m_rows.firstIndex()) {
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if (m_rows.firstIndex() - row > lookAhead)
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cacheRows(qMax(0, row-halfLookAhead), row+halfLookAhead);
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else while (row < m_rows.firstIndex())
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m_rows.prepend(fetchRow(m_rows.firstIndex()-1));
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}
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return m_rows.at(row);
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}
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void RandomListModel::cacheRows(int from, int to) const
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{
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for (int i = from; i <= to; ++i)
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m_rows.insert(i, fetchRow(i));
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}
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//![0]
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//![1]
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QString RandomListModel::fetchRow(int position) const
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{
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return QString::number(rand() % ++position);
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}
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//![1]
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