glfsr.h

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/* -*- c++ -*- */
/*
 * Copyright 2007,2012 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.
 */

#ifndef INCLUDED_DIGITAL_GLFSR_H
#define INCLUDED_DIGITAL_GLFSR_H

#include <gnuradio/digital/api.h>

namespace gr {
  namespace digital {

    /*!
     * \brief Galois Linear Feedback Shift Register using specified polynomial mask
     * \ingroup waveform_generators_blk
     *
     * \details
     * Generates a maximal length pseudo-random sequence of length 2^degree-1
     */
    class DIGITAL_API glfsr
    {
    private:
      int d_shift_register;
      int d_mask;

    public:
      glfsr(int mask, int seed) { d_shift_register = seed; d_mask = mask; }
      ~glfsr();

      static int glfsr_mask(int degree);

      unsigned char next_bit()
      {
        unsigned char bit = d_shift_register & 1;
        d_shift_register >>= 1;
        if(bit)
          d_shift_register ^= d_mask;
        return bit;
      }

      int mask() const { return d_mask; }
    };

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

#endif /* INCLUDED_DIGITAL_GLFSR_H */