/* -*- c++ -*- */
/* 
 * Copyright 2019 Thomas Kolb.
 * 
 * This 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.
 * 
 * This software 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 this software; see the file COPYING.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street,
 * Boston, MA 02110-1301, USA.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <gnuradio/io_signature.h>
#include "scrambler_impl.h"

namespace gr {
	namespace hamnet70 {

		scrambler::sptr
		scrambler::make(uint8_t start, uint8_t polynom)
		{
			return gnuradio::get_initial_sptr
				(new scrambler_impl(start, polynom));
		}

		/*
		 * The private constructor
		 */
		scrambler_impl::scrambler_impl(uint8_t start, uint8_t polynom)
			: gr::tagged_stream_block("scrambler",
					gr::io_signature::make(1, 1, sizeof(uint8_t)),
					gr::io_signature::make(1, 1, sizeof(uint8_t)), "packet_len"),
				d_start(start),
				d_polynom(polynom)
		{}

		/*
		 * Our virtual destructor.
		 */
		scrambler_impl::~scrambler_impl()
		{
		}

		int
		scrambler_impl::calculate_output_stream_length(const gr_vector_int &ninput_items)
		{
			int noutput_items = ninput_items[0];
			return noutput_items ;
		}

		int
		scrambler_impl::work (int noutput_items,
				gr_vector_int &ninput_items,
				gr_vector_const_void_star &input_items,
				gr_vector_void_star &output_items)
		{
			const uint8_t *in = (const uint8_t *) input_items[0];
			uint8_t *out = (uint8_t *) output_items[0];

			uint8_t lfsr = d_start;

			for(size_t i = 0; i < noutput_items; i++) {
				*out = *in ^ lfsr;

				if(lfsr & 0x1) {
					lfsr = (lfsr >> 1) ^ d_polynom;
				} else {
					lfsr >>= 1;
				}
			}

			// Tell runtime system how many output items we produced.
			return noutput_items;
		}

	} /* namespace hamnet70 */
} /* namespace gr */