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

/*

 * Copyright 2008,2010 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.

 */

#ifndef INCLUDED_GR_ADDITIVE_SCRAMBLER_BB_H

#define INCLUDED_GR_ADDITIVE_SCRAMBLER_BB_H

#include <gr_core_api.h>

#include <gr_sync_block.h>

#include "gri_lfsr.h"

class gr_additive_scrambler_bb;

typedef boost::shared_ptr<gr_additive_scrambler_bb> gr_additive_scrambler_bb_sptr;

GR_CORE_API gr_additive_scrambler_bb_sptr gr_make_additive_scrambler_bb(int mask, int seed, int len, int count=0);

/*!

 * Scramble an input stream using an LFSR.  This block works on the LSB only

 * of the input data stream, i.e., on an "unpacked binary" stream, and 

 * produces the same format on its output.

 * 

 * \param mask     Polynomial mask for LFSR

 * \param seed     Initial shift register contents

 * \param len      Shift register length

 * \param count    Number of bits after which shift register is reset, 0=never

 *

 * The scrambler works by XORing the incoming bit stream by the output of

 * the LFSR.  Optionally, after 'count' bits have been processed, the shift

 * register is reset to the seed value.  This allows processing fixed length

 * vectors of samples.

 * 

 * \ingroup coding_blk

 */

class GR_CORE_API gr_additive_scrambler_bb : public gr_sync_block

{

  friend GR_CORE_API gr_additive_scrambler_bb_sptr gr_make_additive_scrambler_bb(int mask, int seed, int len, int count);

  gri_lfsr d_lfsr;

  int      d_count;

  int      d_bits;

  gr_additive_scrambler_bb(int mask, int seed, int len, int count);

public:

  int work(int noutput_items,

           gr_vector_const_void_star &input_items,

           gr_vector_void_star &output_items);

};

#endif /* INCLUDED_GR_ADDITIVE_SCRAMBLER_BB_H */