libs/common/MovingMedian.h

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#ifndef MOVING_MEDIAN_H
#define MOVING_MEDIAN_H

#include <deque>
#include <algorithm>


namespace qrk
{
    template<class T> class MovingMedian
    {
    public:
        MovingMedian(size_t size, T initial_value = 0)
            : buffer_size_(size), median_index_(size >> 1)
        {
            if (buffer_size_ == 0) {
                buffer_size_ = 1;
            }
            buffer_set(buffer_size_, initial_value);
        }


        void setMedianValue(T value)
        {
            buffer_set(buffer_size_, value);
        }


        T median(void)
        {
            return median_;
        }


        T push_back(T value)
        {
            buffer_.pop_front();
            buffer_.push_back(value);

            // 中央値を求める
            // !!! 可能ならば、コピーを除去する
            std::deque<T> copied = buffer_;
            std::nth_element(copied.begin(),
                             copied.begin() + median_index_, copied.end());
            median_ = copied[median_index_];

            return median_;
        }

    private:
        MovingMedian(const MovingMedian& rhs);
        MovingMedian& operator = (const MovingMedian& rhs);

        std::deque<T> buffer_;
        size_t buffer_size_;
        T median_;
        int median_index_;


        void buffer_set(size_t size, T& value)
        {
            buffer_.clear();
            buffer_.assign(size, value);
            median_ = value;
        }
    };
}

#endif /* !MOVING_MEDIAN_H */