diff options
Diffstat (limited to 'examples/tools/contiguouscache/randomlistmodel.cpp')
-rw-r--r-- | examples/tools/contiguouscache/randomlistmodel.cpp | 96 |
1 files changed, 96 insertions, 0 deletions
diff --git a/examples/tools/contiguouscache/randomlistmodel.cpp b/examples/tools/contiguouscache/randomlistmodel.cpp new file mode 100644 index 0000000000..845b1e7a2a --- /dev/null +++ b/examples/tools/contiguouscache/randomlistmodel.cpp @@ -0,0 +1,96 @@ +/**************************************************************************** +** +** Copyright (C) 2011 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. +** +** $QT_BEGIN_LICENSE:BSD$ +** You may use this file under the terms of the BSD license as follows: +** +** "Redistribution and use in source and binary forms, with or without +** modification, are permitted provided that the following conditions are +** met: +** * Redistributions of source code must retain the above copyright +** notice, this list of conditions and the following disclaimer. +** * Redistributions in binary form must reproduce the above copyright +** notice, this list of conditions and the following disclaimer in +** the documentation and/or other materials provided with the +** distribution. +** * Neither the name of Nokia Corporation and its Subsidiary(-ies) nor +** the names of its contributors may be used to endorse or promote +** products derived from this software without specific prior written +** permission. +** +** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS +** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT +** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR +** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT +** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, +** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT +** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, +** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY +** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT +** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE +** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE." +** $QT_END_LICENSE$ +** +****************************************************************************/ +#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] |