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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(const std::string frame_tag_name,
int length_min=32,
int length_max=500)
{
return gnuradio::get_initial_sptr
(new hdlc_deframer_bp_impl(frame_tag_name, length_min, length_max));
}
/*
* The private constructor
*/
hdlc_deframer_bp_impl::hdlc_deframer_bp_impl(const std::string frame_tag_name,
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_frame_tag_name(frame_tag_name),
d_length_min(length_min),
d_length_max(length_max)
{
set_output_multiple(length_max*2);
message_port_register_out(pmt::mp("out"));
}
/*
* Our virtual destructor.
*/
hdlc_deframer_bp_impl::~hdlc_deframer_bp_impl()
{
}
//undo HDLC bit stuffing operation.
static void unstuff(std::vector<unsigned char> &pkt) {
int consec = 0;
for(size_t i=0; i<pkt.size(); i++) {
if(pkt[i]) {
consec++;
} else {
if(consec == 5) {
pkt.erase(pkt.begin()+i);
i--;
}
consec = 0;
}
}
}
//pack unpacked (1 bit per byte) data into bytes, in reverse bit order
//we reverse the bit order because HDLC uses LSbit format.
std::vector<unsigned char>
hdlc_deframer_bp_impl::pack(std::vector<unsigned char> &data)
{
std::vector<unsigned char> output(std::ceil(data.size()/8.0f), 0);
for(size_t i=0; i<data.size(); i++) {
output[i/8] |= (data[i]<<(i%8));
}
return output;
}
unsigned int
hdlc_deframer_bp_impl::crc_ccitt(std::vector<unsigned char> &data) {
unsigned int POLY=0x8408; //reflected 0x1021
unsigned short crc=0xFFFF;
for(size_t i=0; i<data.size(); 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];
//look for frame delimiter tags
std::vector<gr::tag_t> frame_tags;
uint64_t abs_sample_cnt = nitems_read(0);
get_tags_in_range(frame_tags, 0, abs_sample_cnt, abs_sample_cnt + noutput_items, pmt::string_to_symbol(d_frame_tag_name));
int end_pos = 0;
while(frame_tags.size() > 0) {
int start_pos = frame_tags[0].offset - abs_sample_cnt;
if(frame_tags.size() == 1) return start_pos; //start here next time
end_pos = frame_tags[1].offset - abs_sample_cnt;
int pkt_len = frame_tags[1].offset - frame_tags[0].offset - 8; //omit EOF delim
if(pkt_len > d_length_max) return end_pos; //arbitrary, too long for a real pkt
if(pkt_len <= d_length_min) return end_pos;
//get bit array
std::vector<unsigned char> pkt_bits(pkt_len);
memcpy(&pkt_bits[0], &in[start_pos], pkt_bits.size());
unstuff(pkt_bits);
//pack into bytes (and correct bit order)
std::vector<unsigned char> pkt_bytes = pack(pkt_bits);
//strip off the CRC
unsigned int crc = (int(pkt_bytes[pkt_bytes.size()-1]) << 8)
+ pkt_bytes[pkt_bytes.size()-2];
pkt_bytes.erase(pkt_bytes.end()-2, pkt_bytes.end());
unsigned int calc_crc = crc_ccitt(pkt_bytes);
if(crc == calc_crc) {
//publish
//TODO manage padding
pmt::pmt_t pdu(pmt::cons(pmt::PMT_NIL,
pmt::make_blob(&pkt_bytes[0], pkt_bytes.size())));
message_port_pub(pmt::mp("out"), pdu);
}
frame_tags.erase(frame_tags.begin());
}
// Tell runtime system how many output items we produced.
return end_pos;
}
} /* namespace digital */
} /* namespace gr */
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