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/* -*- c++ -*- */
/*
* @file
* @author (C) 2014 by Piotr Krysik <ptrkrysik@gmail.com>
* @section LICENSE
*
* Gr-gsm 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.
*
* Gr-gsm 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 gr-gsm; 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 <grgsm/gsmtap.h>
#include "control_channels_decoder_impl.h"
#define DATA_BYTES 23
namespace gr {
namespace gsm {
static int ubits2sbits(ubit_t *ubits, sbit_t *sbits, int count)
{
int i;
for (i = 0; i < count; i++) {
if (*ubits == 0x23) {
ubits++;
sbits++;
continue;
}
if ((*ubits++) & 1)
*sbits++ = -127;
else
*sbits++ = 127;
}
return count;
}
control_channels_decoder::sptr
control_channels_decoder::make()
{
return gnuradio::get_initial_sptr
(new control_channels_decoder_impl());
}
/*
* Constructor
*/
control_channels_decoder_impl::control_channels_decoder_impl()
: gr::block("control_channels_decoder",
gr::io_signature::make(0, 0, 0),
gr::io_signature::make(0, 0, 0)),
d_collected_bursts_num(0)
{
//setup input/output ports
message_port_register_in(pmt::mp("bursts"));
set_msg_handler(pmt::mp("bursts"), boost::bind(&control_channels_decoder_impl::decode, this, _1));
message_port_register_out(pmt::mp("msgs"));
}
control_channels_decoder_impl::~control_channels_decoder_impl()
{
}
void control_channels_decoder_impl::decode(pmt::pmt_t msg)
{
ubit_t bursts_u[116 * 4];
sbit_t bursts_s[116 * 4];
uint8_t result[23];
int n_errors, n_bits_total;
int8_t header_plus_data[sizeof(gsmtap_hdr)+DATA_BYTES];
d_bursts[d_collected_bursts_num] = msg;
d_collected_bursts_num++;
//get convecutive bursts
if(d_collected_bursts_num==4)
{
d_collected_bursts_num=0;
//reorganize data from input bursts
for(int ii = 0; ii < 4; ii++)
{
pmt::pmt_t header_plus_burst = pmt::cdr(d_bursts[ii]);
int8_t * burst_bits = (int8_t *)(pmt::blob_data(header_plus_burst))+sizeof(gsmtap_hdr);
memcpy(&bursts_u[ii*116], &burst_bits[3],58);
memcpy(&bursts_u[ii*116+58], &burst_bits[3+57+1+26],58);
}
//convert to soft bits
ubits2sbits(bursts_u, bursts_s, 116 * 4);
//decode
if (-1 == gsm0503_xcch_decode(result, bursts_s, &n_errors, &n_bits_total))
{
//Possibly an encrypted message
return;
}
//extract header of the first burst of the four bursts
pmt::pmt_t first_header_plus_burst = pmt::cdr(d_bursts[0]);
gsmtap_hdr * header = (gsmtap_hdr *)pmt::blob_data(first_header_plus_burst);
//copy header and data
memcpy(header_plus_data, header, sizeof(gsmtap_hdr));
memcpy(header_plus_data+sizeof(gsmtap_hdr), result, DATA_BYTES);
//set data type in the header
((gsmtap_hdr*)header_plus_data)->type = GSMTAP_TYPE_UM;
//prepare message
pmt::pmt_t msg_out = pmt::cons(pmt::PMT_NIL, pmt::make_blob(header_plus_data,DATA_BYTES+sizeof(gsmtap_hdr)));
//send message to the output
message_port_pub(pmt::mp("msgs"), msg_out);
}
return;
}
} /* namespace gsm */
} /* namespace gr */
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