/* -*- c++ -*- */
/*
 * Copyright 2015 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 <gnuradio/fec/polar_decoder_sc_systematic.h>
#include <gnuradio/io_signature.h>
#include <volk/volk.h>

namespace gr {
namespace fec {
namespace code {

generic_decoder::sptr polar_decoder_sc_systematic::make(
    int block_size, int num_info_bits, std::vector<int> frozen_bit_positions)
{
    return generic_decoder::sptr(
        new polar_decoder_sc_systematic(block_size, num_info_bits, frozen_bit_positions));
}

polar_decoder_sc_systematic::polar_decoder_sc_systematic(
    int block_size, int num_info_bits, std::vector<int> frozen_bit_positions)
    : polar_decoder_common(
          block_size, num_info_bits, frozen_bit_positions, std::vector<char>())
{
    d_llr_vec = (float*)volk_malloc(sizeof(float) * block_size * (block_power() + 1),
                                    volk_get_alignment());
    memset(d_llr_vec, 0, sizeof(float) * block_size * (block_power() + 1));
    d_u_hat_vec = (unsigned char*)volk_malloc(block_size * (block_power() + 1),
                                              volk_get_alignment());
    memset(d_u_hat_vec, 0, sizeof(unsigned char) * block_size * (block_power() + 1));
    d_frame_vec = (unsigned char*)volk_malloc(block_size, volk_get_alignment());
    memset(d_frame_vec, 0, sizeof(unsigned char) * block_size);
}

polar_decoder_sc_systematic::~polar_decoder_sc_systematic()
{
    volk_free(d_llr_vec);
    volk_free(d_u_hat_vec);
    volk_free(d_frame_vec);
}

void polar_decoder_sc_systematic::generic_work(void* in_buffer, void* out_buffer)
{
    const float* in = (const float*)in_buffer;
    unsigned char* out = (unsigned char*)out_buffer;

    initialize_decoder(d_u_hat_vec, d_llr_vec, in);
    sc_decode(d_llr_vec, d_u_hat_vec);
    volk_encode_block(d_frame_vec, d_u_hat_vec);
    extract_info_bits_reversed(out, d_frame_vec);
}

void polar_decoder_sc_systematic::sc_decode(float* llrs, unsigned char* u)
{
    for (int i = 0; i < block_size(); i++) {
        butterfly(llrs, u, 0, i, i);
        u[i] = retrieve_bit_from_llr(llrs[i], i);
    }
}

unsigned char polar_decoder_sc_systematic::retrieve_bit_from_llr(float llr, const int pos)
{
    if (is_frozen_bit(pos)) {
        return next_frozen_bit();
    }
    return llr_bit_decision(llr);
}

void polar_decoder_sc_systematic::extract_info_bits_reversed(unsigned char* outbuf,
                                                             const unsigned char* inbuf)
{
    for (int i = 0; i < num_info_bits(); i++) {
        *outbuf++ = inbuf[d_info_bit_positions_reversed[i]];
    }
}

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