portapack-mayhem/firmware/baseband/block_decimator.hpp

/*
 * Copyright (C) 2015 Jared Boone, ShareBrained Technology, Inc.
 *
 * This file is part of PortaPack.
 *
 * 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 2, 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 with this program; see the file COPYING.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street,
 * Boston, MA 02110-1301, USA.
 */

#ifndef __BLOCK_DECIMATOR_H__
#define __BLOCK_DECIMATOR_H__

#include <cstdint>
#include <cstddef>
#include <array>

#include "dsp_types.hpp"
#include "complex.hpp"

template <typename T, size_t N>
class BlockDecimator {
   public:
    constexpr BlockDecimator(
        const size_t factor)
        : factor_{factor} {
    }

    void set_input_sampling_rate(const uint32_t new_sampling_rate) {
        if (new_sampling_rate != input_sampling_rate()) {
            input_sampling_rate_ = new_sampling_rate;
            reset_state();
        }
    }

    uint32_t input_sampling_rate() const {
        return input_sampling_rate_;
    }

    void set_factor(const size_t new_factor) {
        if (new_factor != factor()) {
            factor_ = new_factor;
            reset_state();
        }
    }

    size_t factor() const {
        return factor_;
    }

    uint32_t output_sampling_rate() const {
        return input_sampling_rate() / factor();
    }

    template <typename BlockCallback>
    void feed(const buffer_t<T>& src, BlockCallback callback) {
        /* NOTE: Input block size must be >= factor */

        set_input_sampling_rate(src.sampling_rate);

        while (src_i < src.count) {
            buffer[dst_i++] = src.p[src_i];
            if (dst_i == buffer.size()) {
                callback({buffer.data(), buffer.size(), output_sampling_rate()});
                reset_state();
                dst_i = 0;
            }

            src_i += factor();
        }

        src_i -= src.count;
    }

   private:
    std::array<T, N> buffer{};
    uint32_t input_sampling_rate_{0};
    size_t factor_{1};
    size_t src_i{0};
    size_t dst_i{0};

    void reset_state() {
        src_i = 0;
        dst_i = 0;
    }
};

#endif /*__BLOCK_DECIMATOR_H__*/