repetition_decoder_impl.cc

/* -*- c++ -*- */
/*
 * Copyright 2014 Free Software Foundation, Inc.
 *
 * This file is part of GNU Radio
 *
 * GNU Radio 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, or (at your option)
 * any later version.
 *
 * GNU Radio 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 GNU Radio; see the file COPYING.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street,
 * Boston, MA 02110-1301, USA.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "repetition_decoder_impl.h"
#include <math.h>
#include <stdio.h>
#include <volk/volk.h>
#include <boost/assign/list_of.hpp>
#include <sstream>
#include <vector>

namespace gr {
namespace fec {
namespace code {

generic_decoder::sptr repetition_decoder::make(int frame_size, int rep, float ap_prob)
{
    return generic_decoder::sptr(new repetition_decoder_impl(frame_size, rep, ap_prob));
}

repetition_decoder_impl::repetition_decoder_impl(int frame_size, int rep, float ap_prob)
    : generic_decoder("repetition_decoder")
{
    // Set max frame size here; all buffers and settings will be
    // based on this value.
    d_max_frame_size = frame_size;
    set_frame_size(frame_size);

    if (rep < 0)
        throw std::runtime_error("repetition_encoder: repetition rate must be >= 0");
    if ((ap_prob < 0) || (ap_prob > 1.0))
        throw std::runtime_error(
            "repetition_encoder: a priori probability rate must be in [0, 1]");

    d_rep = rep;
    d_ap_prob = ap_prob;
    d_trials.resize(d_rep);
}

repetition_decoder_impl::~repetition_decoder_impl() {}

int repetition_decoder_impl::get_output_size()
{
    // unpacked bits
    return d_frame_size;
}

int repetition_decoder_impl::get_input_size() { return d_frame_size * d_rep; }

int repetition_decoder_impl::get_input_item_size() { return sizeof(float); }

const char* repetition_decoder_impl::get_input_conversion() { return "none"; }

float repetition_decoder_impl::get_shift() { return 0; }

bool repetition_decoder_impl::set_frame_size(unsigned int frame_size)
{
    bool ret = true;
    if (frame_size > d_max_frame_size) {
        GR_LOG_INFO(d_logger,
                    boost::format("tried to set frame to %1%; max possible is %2%") %
                        frame_size % d_max_frame_size);
        frame_size = d_max_frame_size;
        ret = false;
    }

    d_frame_size = frame_size;

    return ret;
}

double repetition_decoder_impl::rate() { return 1.0 / static_cast<double>(d_rep); }

void repetition_decoder_impl::generic_work(void* inbuffer, void* outbuffer)
{
    const float* in = (const float*)inbuffer;
    unsigned char* out = (unsigned char*)outbuffer;

    for (unsigned int i = 0; i < d_frame_size; i++) {
        for (unsigned int r = 0; r < d_rep; r++) {
            d_trials[r] = (in[d_rep * i + r] > 0) ? 1.0f : 0.0f;
        }
        float res = std::count(d_trials.begin(), d_trials.end(), 1.0f);
        if ((res / static_cast<float>(d_rep)) > d_ap_prob)
            out[i] = 1;
        else
            out[i] = 0;
    }
}

} /* namespace code */
} /* namespace fec */
} /* namespace gr */