lib/dvbt/dvbt_symbol_inner_interleaver_impl.cc

/* -*- c++ -*- */
/*
 * Copyright 2015,2016 Free Software Foundation, Inc.
 *
 * This 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.
 *
 * This software 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 software; 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 "dvbt_symbol_inner_interleaver_impl.h"
#include <gnuradio/io_signature.h>

namespace gr {
namespace dtv {

const char dvbt_symbol_inner_interleaver_impl::d_bit_perm_2k[] = { 4, 3, 9, 6, 2,
                                                                   8, 1, 5, 7, 0 };
const char dvbt_symbol_inner_interleaver_impl::d_bit_perm_8k[] = { 7, 1,  4, 2, 9,  6,
                                                                   8, 10, 0, 3, 11, 5 };

void dvbt_symbol_inner_interleaver_impl::generate_H()
{
    const int Mmax = d_fft_length;
    const int Nmax = d_payload_length;
    const int Nr = int(ceil(log2(d_fft_length)));
    int q = 0;

    for (int i = 0; i < Mmax; i++) {
        d_h[q] = ((i % 2) << (Nr - 1)) + calculate_R(i);
        if (d_h[q] < Nmax) {
            q++;
        }
    }
}

int dvbt_symbol_inner_interleaver_impl::H(int q) { return d_h[q]; }

int dvbt_symbol_inner_interleaver_impl::calculate_R(int i)
{
    const int Nr = int(ceil(log2(d_fft_length)));
    int reg = 0;

    if (i == 0) {
        reg = 0;
    } else if (i == 1) {
        reg = 0;
    } else {
        reg = 1;
        for (int k = 3; k <= i; k++) {
            char new_bit = 0;

            if (d_transmission_mode == T2k) {
                new_bit = (reg ^ (reg >> 3)) & 1;
            } else if (d_transmission_mode == T8k) {
                new_bit = (reg ^ (reg >> 1) ^ (reg >> 4) ^ (reg >> 6)) & 1;
            } else {
                new_bit = (reg ^ (reg >> 3)) & 1;
            }

            int mask = (1 << Nr) - 1;
            reg = ((reg >> 1) | (new_bit << (Nr - 2))) & mask;
        }
    }

    int newreg = 0;

    for (int k = 0; k < (Nr - 1); k++) {
        char bit = (reg >> k) & 1;
        newreg = newreg | (bit << d_bit_perm[k]);
    }

    return newreg;
}

dvbt_symbol_inner_interleaver::sptr dvbt_symbol_inner_interleaver::make(
    int nsize, dvbt_transmission_mode_t transmission, int direction)
{
    return gnuradio::get_initial_sptr(
        new dvbt_symbol_inner_interleaver_impl(nsize, transmission, direction));
}

/*
 * The private constructor
 */
dvbt_symbol_inner_interleaver_impl::dvbt_symbol_inner_interleaver_impl(
    int nsize, dvbt_transmission_mode_t transmission, int direction)
    : block("dvbt_symbol_inner_interleaver",
            io_signature::make(1, 1, sizeof(unsigned char) * nsize),
            io_signature::make(1, 1, sizeof(unsigned char) * nsize)),
      config(gr::dtv::MOD_16QAM,
             gr::dtv::NH,
             gr::dtv::C1_2,
             gr::dtv::C1_2,
             gr::dtv::GI_1_32,
             transmission),
      d_nsize(nsize),
      d_direction(direction),
      d_fft_length(0),
      d_payload_length(0),
      d_symbol_index(0)
{
    d_symbols_per_frame = config.d_symbols_per_frame;
    d_transmission_mode = config.d_transmission_mode;
    d_fft_length = config.d_fft_length;
    d_payload_length = config.d_payload_length;
    d_direction = direction;

    // Verify if transmission mode matches with size of block
    assert(d_payload_length == d_nsize);

    // Allocate memory for h vector
    d_h = new (std::nothrow) int[d_fft_length];
    if (d_h == NULL) {
        GR_LOG_FATAL(d_logger,
                     "Symbol Inner Interleaver, cannot allocate memory for d_h.");
        throw std::bad_alloc();
    }

    // Setup bit permutation vectors
    if (d_transmission_mode == T2k) {
        d_bit_perm = d_bit_perm_2k;
    } else if (d_transmission_mode == T8k) {
        d_bit_perm = d_bit_perm_8k;
    } else {
        d_bit_perm = d_bit_perm_2k;
    }

    // Generate the h function
    generate_H();
}

/*
 * Our virtual destructor.
 */
dvbt_symbol_inner_interleaver_impl::~dvbt_symbol_inner_interleaver_impl()
{
    delete[] d_h;
}

void dvbt_symbol_inner_interleaver_impl::forecast(int noutput_items,
                                                  gr_vector_int& ninput_items_required)
{
    ninput_items_required[0] = noutput_items;
}

int dvbt_symbol_inner_interleaver_impl::general_work(
    int noutput_items,
    gr_vector_int& ninput_items,
    gr_vector_const_void_star& input_items,
    gr_vector_void_star& output_items)
{
    const unsigned char* in = (unsigned char*)input_items[0];
    unsigned char* out = (unsigned char*)output_items[0];

    // Demod reference signals sends a tag per OFDM frame
    // containing the symbol index.
    std::vector<tag_t> tags;
    const uint64_t nread = this->nitems_read(0); // number of items read on port 0

    // Read all tags on the input buffer
    this->get_tags_in_range(
        tags, 0, nread, nread + noutput_items, pmt::string_to_symbol("symbol_index"));

    for (int k = 0; k < noutput_items; k++) {
        int blocks = k * d_nsize;

        if (d_direction) {
            // Interleave
            for (int q = 0; q < d_nsize; q++) {
                if (d_symbol_index % 2) {
                    out[blocks + q] = in[blocks + H(q)];
                } else {
                    out[blocks + H(q)] = in[blocks + q];
                }
            }

            ++d_symbol_index;
            d_symbol_index = d_symbol_index % d_symbols_per_frame;
        } else {
            // Deinterleave
            d_symbol_index = pmt::to_long(tags[k].value);

            for (int q = 0; q < d_nsize; q++) {
                if (d_symbol_index % 2) {
                    out[blocks + H(q)] = in[blocks + q];
                } else {
                    out[blocks + q] = in[blocks + H(q)];
                }
            }
        }
    }

    // Tell runtime system how many input items we consumed on
    // each input stream.
    consume_each(noutput_items);

    // Tell runtime system how many output items we produced.
    return noutput_items;
}

} /* namespace dtv */
} /* namespace gr */