source: trunk/src/corelib/concurrent/qtconcurrentmedian.h@ 769

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#ifndef QTCONCURRENT_MEDIAN_H
#define QTCONCURRENT_MEDIAN_H

#include <QtCore/qglobal.h>

#ifndef QT_NO_CONCURRENT

#include <QtCore/qvector.h>
#include <QtCore/qalgorithms.h>

QT_BEGIN_HEADER
QT_BEGIN_NAMESPACE

QT_MODULE(Core)

#ifndef 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> sorted = values;
            qSort(sorted);
            currentMedian = sorted.at(bufferSize / 2 + 1);
        }
        return currentMedian;
    }
private:
    QVector<T> values;
    T currentMedian;
    int bufferSize;
    int currentIndex;
    bool valid;
    bool dirty;
};

} // namespace QtConcurrent

#endif //qdoc

QT_END_NAMESPACE
QT_END_HEADER

#endif // QT_NO_CONCURRENT

#endif