/* -*- c++ -*- */
/*
 * Copyright 2006,2010,2012 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 "diff_decoder_bb_impl.h"
#include <gnuradio/io_signature.h>

namespace gr {
namespace digital {
diff_decoder_bb::sptr diff_decoder_bb::make(unsigned int modulus)
{
    return gnuradio::get_initial_sptr(new diff_decoder_bb_impl(modulus));
}

diff_decoder_bb_impl::diff_decoder_bb_impl(unsigned int modulus)
    : sync_block("diff_decoder_bb",
                 io_signature::make(1, 1, sizeof(unsigned char)),
                 io_signature::make(1, 1, sizeof(unsigned char))),
      d_modulus(modulus)
{
    set_history(2); // need to look at two inputs
}

diff_decoder_bb_impl::~diff_decoder_bb_impl() {}

int diff_decoder_bb_impl::work(int noutput_items,
                               gr_vector_const_void_star& input_items,
                               gr_vector_void_star& output_items)
{
    const unsigned char* in = (const unsigned char*)input_items[0];
    unsigned char* out = (unsigned char*)output_items[0];
    in += 1; // ensure that in[-1] is valid

    unsigned modulus = d_modulus;

    for (int i = 0; i < noutput_items; i++) {
        out[i] = (in[i] - in[i - 1]) % modulus;
    }

    return noutput_items;
}

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