/* -*- c++ -*- */
/*
 * Copyright 2007,2010,2012 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 "pn_correlator_cc_impl.h"
#include <gnuradio/io_signature.h>

namespace gr {
namespace digital {

pn_correlator_cc::sptr pn_correlator_cc::make(int degree, int mask, int seed)
{
    return gnuradio::get_initial_sptr(new pn_correlator_cc_impl(degree, mask, seed));
}

pn_correlator_cc_impl::pn_correlator_cc_impl(int degree, int mask, int seed)
    : sync_decimator("pn_correlator_cc",
                     io_signature::make(1, 1, sizeof(gr_complex)),
                     io_signature::make(1, 1, sizeof(gr_complex)),
                     (unsigned int)((1ULL << degree) - 1)), // PN code length
      d_pn(0.0f)
{
    d_len = (unsigned int)((1ULL << degree) - 1);
    if (mask == 0)
        mask = glfsr::glfsr_mask(degree);
    d_reference = new glfsr(mask, seed);
    for (int i = 0; i < d_len; i++) // initialize to last value in sequence
        d_pn = 2.0 * d_reference->next_bit() - 1.0;
}

pn_correlator_cc_impl::~pn_correlator_cc_impl() { delete d_reference; }

int pn_correlator_cc_impl::work(int noutput_items,
                                gr_vector_const_void_star& input_items,
                                gr_vector_void_star& output_items)
{
    const gr_complex* in = (const gr_complex*)input_items[0];
    gr_complex* out = (gr_complex*)output_items[0];
    gr_complex sum;

    for (int i = 0; i < noutput_items; i++) {
        sum = 0.0;

        for (int j = 0; j < d_len; j++) {
            if (j != 0) // retard PN generator one sample per period
                d_pn = 2.0 * d_reference->next_bit() - 1.0; // no conditionals
            sum += *in++ * d_pn;
        }

        *out++ = sum * gr_complex(1.0 / d_len, 0.0);
    }

    return noutput_items;
}

} /* namespace digital */
} /* namespace gr */
