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// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
#ifndef QTCONCURRENT_MEDIAN_H
#define QTCONCURRENT_MEDIAN_H
#include <QtConcurrent/qtconcurrent_global.h>
#if !defined(QT_NO_CONCURRENT) || defined(Q_QDOC)
#include <algorithm>
#include <cstring>
QT_BEGIN_NAMESPACE
namespace QtConcurrent {
class Median
{
public:
enum { BufferSize = 7 };
Median()
: currentMedian(), currentIndex(0), valid(false), dirty(true)
{
std::fill_n(values, static_cast<int>(BufferSize), 0.0);
}
void reset()
{
std::fill_n(values, static_cast<int>(BufferSize), 0.0);
currentIndex = 0;
valid = false;
dirty = true;
}
void addValue(double value)
{
++currentIndex;
if (currentIndex == BufferSize) {
currentIndex = 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 double currentIndexValue = values[currentIndex];
if ((currentIndexValue > currentMedian && currentMedian > value)
|| (currentMedian > currentIndexValue && value > currentMedian)) {
dirty = true;
}
values[currentIndex] = value;
}
bool isMedianValid() const
{
return valid;
}
double median()
{
if (dirty) {
dirty = false;
double sorted[BufferSize];
::memcpy(&sorted, &values, sizeof(sorted));
std::sort(sorted, sorted + static_cast<int>(BufferSize));
currentMedian = sorted[BufferSize / 2];
}
return currentMedian;
}
private:
double values[BufferSize];
double currentMedian;
int currentIndex;
bool valid;
bool dirty;
};
} // namespace QtConcurrent
QT_END_NAMESPACE
#endif // QT_NO_CONCURRENT
#endif
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