dft.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: dft.hpp
 * Date: 09/06/18
 * Author: Mohammed Boujemaoui
 */

#ifndef EDSP_DFT_HPP
#define EDSP_DFT_HPP

#include <edsp/spectral/internal/fft_impl.hpp>

namespace edsp { inline namespace spectral {

    template <typename Integer>
    constexpr Integer make_fft_size(Integer real_size) noexcept {
        return std::floor(real_size / 2) + 1;
    }

    template <typename Integer>
    constexpr Integer make_ifft_size(Integer complex_size) noexcept {
        return 2 * (complex_size - 1);
    }

    template <typename InputIt, typename OutputIt>
    inline void cdft(InputIt first, InputIt last, OutputIt d_first) {
        using complex_t    = meta::value_type_t<InputIt>;
        using underlying_t = typename complex_t::value_type;
        const auto nfft    = static_cast<typename fft_impl<underlying_t>::size_type>(std::distance(first, last));
        fft_impl<underlying_t> plan(nfft);
        plan.dft(&(*first), &(*d_first));
    }

    template <typename InputIt, typename OutputIt>
    inline void cidft(InputIt first, InputIt last, OutputIt d_first) {
        using complex_t    = meta::value_type_t<InputIt>;
        using underlying_t = typename complex_t::value_type;
        const auto nfft    = static_cast<typename fft_impl<underlying_t>::size_type>(std::distance(first, last));
        fft_impl<underlying_t> plan(nfft);
        plan.idft(&(*first), &(*d_first));
        plan.idft_scale(&(*d_first));
    }

    template <typename InputIt, typename OutputIt>
    void dft(InputIt first, InputIt last, OutputIt d_first) {
        using value_type = typename std::iterator_traits<InputIt>::value_type;
        fft_impl<value_type> plan(std::distance(first, last));
        plan.dft(&(*first), &(*d_first));
    }

    template <typename InputIt, typename OutputIt>
    void idft(InputIt first, InputIt last, OutputIt d_first) {
        using value_type = typename std::iterator_traits<OutputIt>::value_type;
        const auto nfft =
            static_cast<typename fft_impl<value_type>::size_type>(make_ifft_size(std::distance(first, last)));
        fft_impl<value_type> plan(nfft);
        plan.idft(&(*first), &(*d_first));
        plan.idft_scale(&(*d_first));
    }

}} // namespace edsp::spectral

#endif // EDSP_DFT_HPP