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

/*

 * Copyright 2005,2006 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.

 */

#ifndef INCLUDED_GR_CORRELATE_ACCESS_CODE_BB_H

#define INCLUDED_GR_CORRELATE_ACCESS_CODE_BB_H

#include <gr_sync_block.h>

#include <string>

class gr_correlate_access_code_bb;

typedef boost::shared_ptr<gr_correlate_access_code_bb> gr_correlate_access_code_bb_sptr;

/*!

 * \param access_code is represented with 1 byte per bit, e.g., "010101010111000100"

 * \param threshold maximum number of bits that may be wrong

 */

gr_correlate_access_code_bb_sptr 

gr_make_correlate_access_code_bb (const std::string &access_code, int threshold);

/*!

 * \brief Examine input for specified access code, one bit at a time.

 * \ingroup sync_blk

 *

 * input:  stream of bits, 1 bit per input byte (data in LSB)

 * output: stream of bits, 2 bits per output byte (data in LSB, flag in next higher bit)

 *

 * Each output byte contains two valid bits, the data bit, and the

 * flag bit.  The LSB (bit 0) is the data bit, and is the original

 * input data, delayed 64 bits.  Bit 1 is the

 * flag bit and is 1 if the corresponding data bit is the first data

 * bit following the access code. Otherwise the flag bit is 0.

 */

class gr_correlate_access_code_bb : public gr_sync_block

{

  friend gr_correlate_access_code_bb_sptr 

  gr_make_correlate_access_code_bb (const std::string &access_code, int threshold);

 private:

  unsigned long long d_access_code;        // access code to locate start of packet

                                        //   access code is left justified in the word

  unsigned long long d_data_reg;        // used to look for access_code

  unsigned long long d_flag_reg;        // keep track of decisions

  unsigned long long d_flag_bit;        // mask containing 1 bit which is location of new flag

  unsigned long long d_mask;                // masks access_code bits (top N bits are set where

                                        //   N is the number of bits in the access code)

  unsigned int             d_threshold;        // how many bits may be wrong in sync vector

 protected:

  gr_correlate_access_code_bb(const std::string &access_code, int threshold);

 public:

  ~gr_correlate_access_code_bb();

  int work(int noutput_items,

           gr_vector_const_void_star &input_items,

           gr_vector_void_star &output_items);

  /*!

   * \param access_code is represented with 1 byte per bit, e.g., "010101010111000100"

   */

  bool set_access_code (const std::string &access_code);

};

#endif /* INCLUDED_GR_CORRELATE_ACCESS_CODE_BB_H */