/* -*- 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 <volk/volk.h>
#include <gnuradio/io_signature.h>
#include "async_scrambler_impl.h"

namespace gr {
	namespace hamnet70 {

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

		/*
		 * The private constructor
		 */
		async_scrambler_impl::async_scrambler_impl(uint8_t start, uint8_t polynom)
			: gr::block("async_scrambler",
					gr::io_signature::make(0, 0, 0),
					gr::io_signature::make(0, 0, 0)),
				d_start(start),
				d_polynom(polynom)
		{
			d_in_port = pmt::mp("pdu_in");
			d_out_port = pmt::mp("pdu_out");

			message_port_register_in(d_in_port);
			message_port_register_out(d_out_port);

			set_msg_handler(d_in_port, boost::bind(&async_scrambler_impl::scramble, this ,_1) );
		}

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

		void async_scrambler_impl::scramble(pmt::pmt_t pdu)
		{
			// extract input pdu
			pmt::pmt_t meta(pmt::car(pdu));
			pmt::pmt_t bytes(pmt::cdr(pdu));

			unsigned int crc;
			size_t pkt_len(0);
			const uint8_t* bytes_in = pmt::u8vector_elements(bytes, pkt_len);
			uint8_t* bytes_out = (uint8_t*)volk_malloc(pkt_len*sizeof(uint8_t),
					volk_get_alignment());

			uint8_t lfsr = d_start;
			for(size_t i = 0; i < pkt_len; i++) {
				bytes_out[i] = bytes_in[i] ^ lfsr;

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

			pmt::pmt_t output = pmt::init_u8vector(pkt_len, bytes_out); // this copies the values from bytes_out into the u8vector
			pmt::pmt_t msg_pair = pmt::cons(meta, output);
			message_port_pub(d_out_port, msg_pair);
			volk_free(bytes_out);
		}

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