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

/*

 * Copyright 2002 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 _ATSC_SLIDING_CORRELATOR_H_

#define _ATSC_SLIDING_CORRELATOR_H_

#include <string.h>

extern const unsigned char atsc_pn511[511];

extern const unsigned char atsc_pn63[63];

/*!

 * \brief look for the PN 511 field sync pattern

 */

class atsci_sliding_correlator {

 public:

  atsci_sliding_correlator ();

  ~atsci_sliding_correlator (){};

  //! input hard decision bit, return correlation (0,511)

  // Result is the number of wrong bits.  

  // E.g., 0 -> perfect match; 511 -> all bits are wrong

  int input_bit (int bit);

  //! input sample, return correlation (0,511)

  // Result is the number of wrong bits.  

  // E.g., 0 -> perfect match; 511 -> all bits are wrong

  int input_int (int sample){

    return input_bit (sample < 0 ? 0 : 1);

  }

  //! input sample, return correlation (0,511)

  // Result is the number of wrong bits.  

  // E.g., 0 -> perfect match; 511 -> all bits are wrong

  int input_float (float sample){

    return input_bit (sample < 0 ? 0 : 1);

  }

  void reset () { input.reset (); }

 private:

  typedef unsigned long        srblock;

  static const int bits_per_char = 8;

  static const int srblock_bitsize = sizeof (srblock) * bits_per_char;

  static const int NSRBLOCKS = (511 + srblock_bitsize - 1) / srblock_bitsize;

  class shift_reg {

  public:

    shift_reg ()  { reset (); }

    void reset () { memset (d, 0, sizeof (d)); }

    void shift_in (int bit);

    srblock        d[NSRBLOCKS];

  };

  shift_reg        mask;                // pattern we're looking for

  shift_reg        input;                // current input window

  shift_reg        and_mask;        // bits to consider

};

#endif /* _ATSC_SLIDING_CORRELATOR_H_ */