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/* -*- c++ -*- */
/*
* Copyright 2014 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.
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <gnuradio/io_signature.h>
#include <gnuradio/tags.h>
#include "hdlc_deframer_bp_impl.h"
namespace gr {
namespace digital {
hdlc_deframer_bp::sptr
hdlc_deframer_bp::make(int length_min=32,
int length_max=500)
{
return gnuradio::get_initial_sptr
(new hdlc_deframer_bp_impl(length_min, length_max));
}
/*
* The private constructor
*/
hdlc_deframer_bp_impl::hdlc_deframer_bp_impl(int length_min,
int length_max)
: gr::sync_block("hdlc_deframer_bp",
gr::io_signature::make(1, 1, sizeof(unsigned char)),
gr::io_signature::make(0, 0, 0)),
d_length_min(length_min),
d_length_max(length_max)
{
set_output_multiple(length_max*2);
message_port_register_out(pmt::mp("out"));
d_bytectr=0;
d_bitctr=0;
d_ones=0;
d_pktbuf = new unsigned char[length_max+2];
d_in_frame=false;
}
/*
* Our virtual destructor.
*/
hdlc_deframer_bp_impl::~hdlc_deframer_bp_impl()
{
}
unsigned int
hdlc_deframer_bp_impl::crc_ccitt(unsigned char *data, size_t len) {
unsigned int POLY=0x8408; //reflected 0x1021
unsigned short crc=0xFFFF;
for(size_t i=0; i<len; i++) {
crc ^= data[i];
for(size_t j=0; j<8; j++) {
if(crc&0x01) crc = (crc >> 1) ^ POLY;
else crc = (crc >> 1);
}
}
return crc ^ 0xFFFF;
}
int
hdlc_deframer_bp_impl::work(int noutput_items,
gr_vector_const_void_star &input_items,
gr_vector_void_star &output_items)
{
const unsigned char *in = (const unsigned char *) input_items[0];
unsigned char bit;
int n=0;
while (n < noutput_items) {
bit=*in;
if(d_ones>=5) {
if(bit) { //six ones is a frame delimiter
if(d_bytectr >= d_length_min) {
//check CRC, publish frame
unsigned short crc = d_pktbuf[d_bytectr-1] << 8
| d_pktbuf[d_bytectr-2];
unsigned short calc_crc = crc_ccitt(d_pktbuf, d_bytectr-2);
if (crc==calc_crc) {
pmt::pmt_t pdu(pmt::cons(pmt::PMT_NIL,
pmt::make_blob(&d_pktbuf[0], d_bytectr-2)));
message_port_pub(pmt::mp("out"), pdu);
}
else {
}
d_in_frame=false;
} else {
d_in_frame=true;
}
d_bitctr=0;
d_bytectr=0;
} else { //unstuff
}
} else { //not 5+ continuous ones
if(d_in_frame) {
if(d_bytectr > d_length_max) {
d_bytectr=0;
d_bitctr=0;
d_in_frame=false;
} else {
d_pktbuf[d_bytectr]>>=1;
if (bit) d_pktbuf[d_bytectr] |= 0x80;
d_bitctr++;
if (d_bitctr==8) {
d_bitctr=0;
d_bytectr++;
}
}
}
}
d_ones = (bit) ? d_ones+1 : 0;
in++;
n++;
}
return n;
}
} /* namespace digital */
} /* namespace gr */
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