additive_scrambler_bb.h

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/* -*- c++ -*- */
/*
 * Copyright 2008,2010,2012 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_ADDITIVE_SCRAMBLER_BB_H
#define INCLUDED_DIGITAL_ADDITIVE_SCRAMBLER_BB_H
 
#include <gnuradio/digital/api.h>
#include <gnuradio/sync_block.h>
 
namespace gr {
namespace digital {
 
/*!
 * \ingroup coding_blk
 *
 * \brief
 * Scramble an input stream using an LFSR.
 *
 * \details
 * This block scrambles up to 8 bits per byte of the input
 * data stream, starting at the LSB.
 *
 * The scrambler works by XORing the incoming bit stream by the
 * output of the LFSR. Optionally, after \p count bits have been
 * processed, the shift register is reset to the \p seed value.
 * This allows processing fixed length vectors of samples.
 *
 * Alternatively, the LFSR can be reset using a reset tag to
 * scramble variable length vectors. However, it cannot be reset
 * between bytes.
 *
 * For details on configuring the LFSR, see gr::digital::lfsr.
 */
class DIGITAL_API additive_scrambler_bb : virtual public sync_block
{
public:
    // gr::digital::additive_scrambler_bb::sptr
    typedef boost::shared_ptr<additive_scrambler_bb> sptr;
 
    /*!
     * \brief Create additive scrambler.
     *
     * \param mask   Polynomial mask for LFSR
     * \param seed   Initial shift register contents
     * \param len    Shift register length
     * \param count  Number of bytes after which shift register is reset, 0=never
     * \param bits_per_byte Number of bits per byte
     * \param reset_tag_key When a tag with this key is detected, the shift register is
     * reset (when this is set, count is ignored!)
     */
    static sptr make(int mask,
                     int seed,
                     int len,
                     int count = 0,
                     int bits_per_byte = 1,
                     const std::string& reset_tag_key = "");
 
    virtual int mask() const = 0;
    virtual int seed() const = 0;
    virtual int len() const = 0;
    virtual int count() const = 0;
    virtual int bits_per_byte() = 0;
};
 
} /* namespace digital */
} /* namespace gr */
 
#endif /* INCLUDED_DIGITAL_ADDITIVE_SCRAMBLER_BB_H */