cc_encoder_impl.cc

/* -*- c++ -*- */
/*
 * Copyright 2013-2014 Free Software Foundation, Inc.
 *
 * This file is part of GNU Radio
 *
 * SPDX-License-Identifier: GPL-3.0-or-later
 *
 */

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

#include "cc_encoder_impl.h"
#include <gnuradio/fec/cc_common.h>
#include <gnuradio/fec/generic_encoder.h>
#include <volk/volk.h>
#include <volk/volk_typedefs.h>
#include <boost/assign/list_of.hpp>
#include <cmath>
#include <cstdio>
#include <sstream>
#include <vector>

namespace gr {
namespace fec {
namespace code {

generic_encoder::sptr cc_encoder::make(int frame_size,
                                       int k,
                                       int rate,
                                       std::vector<int> polys,
                                       int start_state,
                                       cc_mode_t mode,
                                       bool padded)
{
    return generic_encoder::sptr(
        new cc_encoder_impl(frame_size, k, rate, polys, start_state, mode, padded));
}

cc_encoder_impl::cc_encoder_impl(int frame_size,
                                 int k,
                                 int rate,
                                 std::vector<int> polys,
                                 int start_state,
                                 cc_mode_t mode,
                                 bool padded)
    : generic_encoder("cc_encoder"),
      d_rate(rate),
      d_k(k),
      d_polys(polys),
      d_start_state(start_state),
      d_mode(mode),
      d_padding(0)
{
    if (static_cast<size_t>(d_rate) != d_polys.size()) {
        throw std::runtime_error(
            "cc_encoder: Number of polynomials must be the same as the value of rate");
    }

    if (d_rate < 2) {
        throw std::runtime_error("cc_encoder: inverse rate r must be > 2");
    }

    if (k < 2 || k > 31) {
        throw std::runtime_error(
            "cc_encoder: constraint length K must in be the range [2, 31]");
    }

    if (d_start_state >= (1u << (d_k - 1))) {
        throw std::runtime_error("cc_encoder: start state is invalid; must be in range "
                                 "[0, 2^(K-1)-1] where K is the constraint length");
    }

    if (frame_size < 1) {
        throw std::runtime_error("cc_encoder: frame_size must be > 0");
    }

    if (mode != CC_STREAMING && mode != CC_TRUNCATED && mode != CC_TAILBITING &&
        mode != CC_TERMINATED) {
        throw std::runtime_error("cc_encoder: invalid mode passed");
    }

    partab_init();

    // set up a padding factor. If padding, extends the encoding
    // by this many bits to fit into a full byte.
    if (padded && (mode == CC_TERMINATED)) {
        d_padding = static_cast<int>(8.0f * ceilf(d_rate * (d_k - 1) / 8.0f) -
                                     (d_rate * (d_k - 1)));
    }

    d_max_frame_size = frame_size;
    set_frame_size(frame_size);
}

cc_encoder_impl::~cc_encoder_impl() {}

int cc_encoder_impl::get_output_size() { return d_output_size; }

int cc_encoder_impl::get_input_size() { return d_frame_size; }

bool cc_encoder_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;

    if (d_mode == CC_TERMINATED) {
        d_output_size = d_rate * (d_frame_size + d_k - 1) + d_padding;
    }
    /*
    else if(d_trunc_intrinsic) {
      int cnt = 0;
      for(int i = 0; i < d_rate; ++i) {
        if (d_polys[i] != 1) {
          cnt++;
        }
      }
      d_output_size = (d_rate * (d_frame_size)) + (cnt * (d_k - 1));
    }
    */
    else {
        d_output_size = d_rate * d_frame_size;
    }

    return ret;
}

double cc_encoder_impl::rate() { return static_cast<double>(d_rate); }

int cc_encoder_impl::parity(int x)
{
    x ^= (x >> 16);
    x ^= (x >> 8);
    return parityb(x);
}

int cc_encoder_impl::parityb(unsigned char x) { return Partab[x]; }

void cc_encoder_impl::partab_init(void)
{
    int i, cnt, ti;

    /* Initialize parity lookup table */
    for (i = 0; i < 256; i++) {
        cnt = 0;
        ti = i;
        while (ti) {
            if (ti & 1)
                cnt++;
            ti >>= 1;
        }
        Partab[i] = cnt & 1;
    }
}

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

    unsigned int my_state = d_start_state;

    if (d_mode == CC_TAILBITING) {
        for (unsigned int i = 0; i < d_k - 1; ++i) {
            my_state = (my_state << 1) | (in[d_frame_size - (d_k - 1) + i] & 1);
        }
    }

    for (unsigned int i = 0; i < d_frame_size; ++i) {
        my_state = (my_state << 1) | (in[i] & 1);
        for (unsigned int j = 0; j < d_rate; ++j) {
            out[i * d_rate + j] =
                (d_polys[j] < 0) ^ parity(my_state & abs(d_polys[j])) ? 1 : 0;
        }
    }

    if (d_mode == CC_TERMINATED) {
        for (unsigned int i = 0; i < d_k - 1; ++i) {
            my_state = (my_state << 1) | ((d_start_state >> (d_k - 2 - i)) & 1);
            for (unsigned int j = 0; j < d_rate; ++j) {
                out[(i + d_frame_size) * d_rate + j] =
                    (d_polys[j] < 0) ^ parity(my_state & abs(d_polys[j])) ? 1 : 0;
            }
        }
    }

    if (d_mode == CC_TRUNCATED) {
        my_state = d_start_state;
    }

    d_start_state = my_state;
}

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