moving-average.hpp

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/*
 * Copyright (C) 2023  Christopher J. Howard
 *
 * This file is part of Antkeeper source code.
 *
 * Antkeeper source code 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.
 *
 * Antkeeper source code 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 with Antkeeper source code.  If not, see <http://www.gnu.org/licenses/>.
 */
 
#ifndef ANTKEEPER_MATH_MOVING_AVERAGE_HPP
#define ANTKEEPER_MATH_MOVING_AVERAGE_HPP
 
#include <algorithm>
#include <cstdint>
#include <vector>
 
namespace math {
 
template <class T>
class moving_average
{
public:
    using sample_type = T;
    
    explicit moving_average(std::size_t capacity):
        m_samples(capacity)
    {}
    moving_average() noexcept = default;
    
    sample_type operator()(sample_type value) noexcept
    {
        m_sum += value;
        if (m_sample_index < m_samples.size())
        {
            m_samples[m_sample_index] = value;
            ++m_sample_index;
            m_average = m_sum / static_cast<sample_type>(m_sample_index);
        }
        else
        {
            sample_type& sample = m_samples[m_sample_index % m_samples.size()];
            m_sum -= sample;
            sample = value;
            ++m_sample_index;
            m_average = m_sum / static_cast<sample_type>(m_samples.size());
        }
        
        return m_average;
    }
    
    void reset() noexcept
    {
        m_sample_index = 0;
        m_sum = sample_type{0};
        m_average = sample_type{0};
    }
    
    void reserve(std::size_t capacity)
    {
        m_samples.resize(capacity, sample_type{0});
    }
    
    void resize(std::size_t size)
    {
        if (size > m_samples.size())
        {
            m_samples.resize(size);
        }
        m_sample_index = size;
    }
    
    [[nodiscard]] inline constexpr sample_type* data() const noexcept
    {
        return m_samples.data();
    }
    
    [[nodiscard]] inline sample_type average() const noexcept
    {
        return m_average;
    }
    
    [[nodiscard]] inline sample_type sum() const noexcept
    {
        return m_sum;
    }
    
    [[nodiscard]] inline std::size_t size() const noexcept
    {
        return std::min<std::size_t>(m_sample_index, m_samples.size());
    }
    
    [[nodiscard]] inline constexpr std::size_t capacity() const noexcept
    {
        return m_samples.size();
    }
    
    [[nodiscard]] inline constexpr bool empty() const noexcept
    {
        return !m_sample_index;
    }
    
    [[nodiscard]] inline constexpr bool full() const noexcept
    {
        return m_sample_index >= m_samples.size();
    }
    
private:
    std::vector<sample_type> m_samples;
    std::size_t m_sample_index{0};
    sample_type m_sum{0};
    sample_type m_average{0};
};
 
} // namespace math
 
#endif // ANTKEEPER_MATH_MOVING_AVERAGE_HPP