128 lines
4.0 KiB
C++
128 lines
4.0 KiB
C++
/* -*- c++ -*- */
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/*
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* @file
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* @author (C) 2014 by Piotr Krysik <ptrkrysik@gmail.com>
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* @section LICENSE
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*
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* Gr-gsm is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 3, or (at your option)
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* any later version.
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*
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* Gr-gsm is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with gr-gsm; see the file COPYING. If not, write to
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* the Free Software Foundation, Inc., 51 Franklin Street,
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* Boston, MA 02110-1301, USA.
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*/
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#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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#include <gnuradio/io_signature.h>
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#include <grgsm/gsmtap.h>
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#include "control_channels_decoder_impl.h"
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#define DATA_BYTES 23
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namespace gr {
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namespace gsm {
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static int ubits2sbits(ubit_t *ubits, sbit_t *sbits, int count)
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{
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int i;
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for (i = 0; i < count; i++) {
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if (*ubits == 0x23) {
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ubits++;
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sbits++;
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continue;
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}
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if ((*ubits++) & 1)
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*sbits++ = -127;
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else
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*sbits++ = 127;
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}
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return count;
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}
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control_channels_decoder::sptr
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control_channels_decoder::make()
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{
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return gnuradio::get_initial_sptr
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(new control_channels_decoder_impl());
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}
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/*
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* Constructor
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*/
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control_channels_decoder_impl::control_channels_decoder_impl()
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: gr::block("control_channels_decoder",
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gr::io_signature::make(0, 0, 0),
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gr::io_signature::make(0, 0, 0)),
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d_collected_bursts_num(0)
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{
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//setup input/output ports
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message_port_register_in(pmt::mp("bursts"));
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set_msg_handler(pmt::mp("bursts"), boost::bind(&control_channels_decoder_impl::decode, this, _1));
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message_port_register_out(pmt::mp("msgs"));
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}
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control_channels_decoder_impl::~control_channels_decoder_impl()
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{
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}
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void control_channels_decoder_impl::decode(pmt::pmt_t msg)
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{
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ubit_t bursts_u[116 * 4];
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sbit_t bursts_s[116 * 4];
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uint8_t result[23];
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int n_errors, n_bits_total;
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int8_t header_plus_data[sizeof(gsmtap_hdr)+DATA_BYTES];
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d_bursts[d_collected_bursts_num] = msg;
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d_collected_bursts_num++;
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//get convecutive bursts
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if(d_collected_bursts_num==4)
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{
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d_collected_bursts_num=0;
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//reorganize data from input bursts
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for(int ii = 0; ii < 4; ii++)
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{
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pmt::pmt_t header_plus_burst = pmt::cdr(d_bursts[ii]);
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int8_t * burst_bits = (int8_t *)(pmt::blob_data(header_plus_burst))+sizeof(gsmtap_hdr);
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memcpy(&bursts_u[ii*116], &burst_bits[3],58);
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memcpy(&bursts_u[ii*116+58], &burst_bits[3+57+1+26],58);
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}
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//convert to soft bits
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ubits2sbits(bursts_u, bursts_s, 116 * 4);
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//decode
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gsm0503_xcch_decode(result, bursts_s, &n_errors, &n_bits_total);
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//extract header of the first burst of the four bursts
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pmt::pmt_t first_header_plus_burst = pmt::cdr(d_bursts[0]);
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gsmtap_hdr * header = (gsmtap_hdr *)pmt::blob_data(first_header_plus_burst);
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//copy header and data
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memcpy(header_plus_data, header, sizeof(gsmtap_hdr));
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memcpy(header_plus_data+sizeof(gsmtap_hdr), result, DATA_BYTES);
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//set data type in the header
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((gsmtap_hdr*)header_plus_data)->type = GSMTAP_TYPE_UM;
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//prepare message
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pmt::pmt_t msg_out = pmt::cons(pmt::PMT_NIL, pmt::make_blob(header_plus_data,DATA_BYTES+sizeof(gsmtap_hdr)));
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//send message to the output
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message_port_pub(pmt::mp("msgs"), msg_out);
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}
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return;
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}
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} /* namespace gsm */
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} /* namespace gr */
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