/* -*- c++ -*- */

/*

 * Copyright 2006 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 <gr_diff_decoder_bb.h>

#include <gr_io_signature.h>

gr_diff_decoder_bb_sptr

gr_make_diff_decoder_bb (unsigned int modulus)

{

  return gr_diff_decoder_bb_sptr (new gr_diff_decoder_bb(modulus));

}

gr_diff_decoder_bb::gr_diff_decoder_bb (unsigned int modulus)

  : gr_sync_block ("diff_decoder_bb",

                   gr_make_io_signature (1, 1, sizeof (unsigned char)),

                   gr_make_io_signature (1, 1, sizeof (unsigned char))),

    d_modulus(modulus)

{

  set_history(2);        // need to look at two inputs

}

int

gr_diff_decoder_bb::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;

}