moving_average_filter.hpp

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/*
 * eDSP, A cross-platform Digital Signal Processing library written in modern C++.
 * Copyright (C) 2018 Mohammed Boujemaoui Boulaghmoudi, All rights reserved.
 *
 * This program is free software: you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation, either version 3 of the License, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of  MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along width
 * this program.  If not, see <http://www.gnu.org/licenses/>
 *
 * File: moving_average_filter.hpp
 * Date: 14/6/2018
 * Authors: Mohammed Boujemaoui
 */
#ifndef EDSP_FILTER_MOVING_AVERAGE_FILTER_H
#define EDSP_FILTER_MOVING_AVERAGE_FILTER_H

#include <edsp/types/ring_buffer.hpp>

namespace edsp { namespace filter {

    template <typename T, typename Allocator = std::allocator<T>>
    class moving_average {
    public:
        using size_type  = std::size_t;
        using value_type = T;

        explicit moving_average(size_type N);

        size_type size() const;

        void resize(size_type N);

        void reset();

        template <typename InputIt, typename OutputIt>
        void filter(InputIt first, InputIt last, OutputIt d_first);

        value_type tick(value_type tick);

    private:
        edsp::ring_buffer<T, Allocator> window_;
        T accumulated_{0};
    };

    template <typename T, typename Allocator>
    moving_average<T, Allocator>::moving_average(size_type N) : window_(N, T()) {}

    template <typename T, typename Allocator>
    typename moving_average<T, Allocator>::size_type moving_average<T, Allocator>::size() const {
        return window_.capacity();
    }

    template <typename T, typename Allocator>
    void moving_average<T, Allocator>::reset() {
        window_.clear();
    }

    template <typename T, typename Allocator>
    template <typename InputIt, typename OutputIt>
    void moving_average<T, Allocator>::filter(InputIt first, InputIt last, OutputIt d_first) {
        if (window_.full()) {
            for (; first != last; ++d_first, ++first) {
                accumulated_ -= window_.front();
                accumulated_ += *first;
                window_.push_back(*first);
                *d_first = accumulated_ / static_cast<T>(window_.size());
            }
        } else {
            for (; first != last; ++d_first, ++first) {
                accumulated_ += *first;
                window_.push_back(*first);
                *d_first = accumulated_ / static_cast<T>(window_.size());
            }
        };
    }

    template <typename T, typename Allocator>
    void moving_average<T, Allocator>::resize(size_type N) {
        window_.resize(N);
    }

    template<typename T, typename Allocator>
    typename moving_average<T, Allocator>::value_type moving_average<T, Allocator>::tick(value_type tick) {
        if (window_.full()) {
            accumulated_ -= window_.front();
            accumulated_ += tick;
            window_.push_back(tick);
        } else {
            accumulated_ += tick;
            window_.push_back(tick);
        };
        return accumulated_ / static_cast<T>(window_.size());
    }

    }} // namespace edsp::filter

#endif // EDSP_FILTER_MOVING_AVERAGE_FILTER_H