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/****************************************************************************
**
** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
** Contact: http://www.qt-project.org/legal
**
** This file is part of the QtCore 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.
**
**
** $QT_END_LICENSE$
**
****************************************************************************/
#ifndef QTCONCURRENT_MEDIAN_H
#define QTCONCURRENT_MEDIAN_H
#include <QtConcurrent/qtconcurrent_global.h>
#ifndef QT_NO_CONCURRENT
#include <QtCore/qvector.h>
#include <algorithm>
QT_BEGIN_NAMESPACE
#ifndef Q_QDOC
namespace QtConcurrent {
template <typename T>
class Median
{
public:
Median(int _bufferSize)
: currentMedian(), bufferSize(_bufferSize), currentIndex(0), valid(false), dirty(true)
{
values.resize(bufferSize);
}
void reset()
{
values.fill(0);
currentIndex = 0;
valid = false;
dirty = true;
}
void addValue(T value)
{
currentIndex = ((currentIndex + 1) % bufferSize);
if (valid == false && currentIndex % bufferSize == 0)
valid = true;
// Only update the cached median value when we have to, that
// is when the new value is on then other side of the median
// compared to the current value at the index.
const T currentIndexValue = values[currentIndex];
if ((currentIndexValue > currentMedian && currentMedian > value)
|| (currentMedian > currentIndexValue && value > currentMedian)) {
dirty = true;
}
values[currentIndex] = value;
}
bool isMedianValid() const
{
return valid;
}
T median()
{
if (dirty) {
dirty = false;
QVector<T> copy = values;
typename QVector<T>::iterator begin = copy.begin(), mid = copy.begin() + bufferSize/2, end = copy.end();
std::nth_element(begin, mid, end);
currentMedian = *mid;
}
return currentMedian;
}
private:
QVector<T> values;
T currentMedian;
int bufferSize;
int currentIndex;
bool valid;
bool dirty;
};
} // namespace QtConcurrent
#endif //Q_QDOC
QT_END_NAMESPACE
#endif // QT_NO_CONCURRENT
#endif
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