lfsr_15_1_0.h

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/* -*- c++ -*- */
/*
 * Copyright 2004 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_GRI_LFSR_15_1_0_H
#define INCLUDED_GRI_LFSR_15_1_0_H

#include <gnuradio/blocks/api.h>

namespace gr {
  namespace blocks {

    /*!
     * \brief Linear Feedback Shift Register using primitive polynomial x^15 + x + 1
     * \ingroup misc
     *
     * \details
     * Generates a maximal length pseudo-random sequence of length
     * 2^15 - 1 bits.
     */
    class BLOCKS_API lfsr_15_1_0
    {
    private:
      unsigned long d_sr;    // shift register

    public:
      lfsr_15_1_0() { reset(); }

      void reset() { d_sr = 0x7fff; }

      int next_bit()
      {
        d_sr = ((((d_sr >> 1) ^ d_sr) & 0x1) << 14) | (d_sr >> 1);
        return d_sr & 0x1;
      }

      int next_byte ()
      {
        int     v = 0;
        for(int i = 0; i < 8; i++) {
          v >>= 1;
          if(next_bit ())
            v |= 0x80;
        }
        return v;
      }
    };

  } /* namespace blocks */
} /* namespace gr */

#endif /* INCLUDED_GRI_LFSR_15_1_0_H */