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/* -*- c++ -*- */
/*
* Copyright 2014 Free Software Foundation, Inc.
*
* This file is part of GNU Radio
*
* SPDX-License-Identifier: GPL-3.0-or-later
*
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include "hdlc_framer_pb_impl.h"
#include <gnuradio/io_signature.h>
#include <gnuradio/tags.h>
namespace gr {
namespace digital {
hdlc_framer_pb::sptr hdlc_framer_pb::make(const std::string frame_tag_name)
{
return gnuradio::make_block_sptr<hdlc_framer_pb_impl>(frame_tag_name);
}
/*
* The private constructor
*/
hdlc_framer_pb_impl::hdlc_framer_pb_impl(const std::string frame_tag_name)
: gr::sync_block("hdlc_framer_pb",
gr::io_signature::make(0, 0, 0),
gr::io_signature::make(1, 1, sizeof(unsigned char))),
d_port(pmt::mp("in"))
{
message_port_register_in(d_port);
d_frame_tag = pmt::string_to_symbol(frame_tag_name);
std::stringstream str;
str << name() << unique_id();
d_me = pmt::string_to_symbol(str.str());
}
/*
* Our virtual destructor.
*/
hdlc_framer_pb_impl::~hdlc_framer_pb_impl() {}
// bit stuff
void hdlc_framer_pb_impl::stuff(std::vector<unsigned char>& pkt)
{
int consec = 0;
for (size_t i = 0; i < pkt.size(); i++) {
if (consec == 5) {
pkt.insert(pkt.begin() + i, 0);
consec = 0;
}
if (pkt[i] == 1)
consec++;
else
consec = 0;
}
}
// unpack packed (8 bits per byte) into bits, in LSbit order.
// TODO: handle non-multiple-of-8 bit lengths (pad low)
std::vector<unsigned char> hdlc_framer_pb_impl::unpack(std::vector<unsigned char>& data)
{
std::vector<unsigned char> output(data.size() * 8, 0);
for (size_t i = 0; i < data.size(); i++) {
for (size_t j = 0; j < 8; j++) {
output[i * 8 + j] = (data[i] >> j) & 1;
}
}
return output;
}
unsigned int hdlc_framer_pb_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_framer_pb_impl::work(int noutput_items,
gr_vector_const_void_star& input_items,
gr_vector_void_star& output_items)
{
unsigned char* out = (unsigned char*)output_items[0];
// send leftovers one chunk at a time.
// it'd be more efficient to send as much as possible, i.e.
// partial packets., but if we're to preserve tag boundaries
// this is much, much simpler.
int oidx = 0;
while (!d_leftovers.empty()) {
if ((size_t)noutput_items < (oidx + d_leftovers[0].size()))
return oidx;
memcpy(out + oidx, &d_leftovers[0][0], d_leftovers[0].size());
// start tag
add_item_tag(0,
nitems_written(0) + oidx,
d_frame_tag,
pmt::from_long(d_leftovers[0].size()),
d_me);
oidx += d_leftovers[0].size();
d_leftovers.erase(d_leftovers.begin());
}
// get PDU
pmt::pmt_t msg(delete_head_nowait(d_port));
if (msg.get() == NULL)
return oidx;
pmt::pmt_t len(pmt::car(msg)); // TODO for non-mult-8 nbits
pmt::pmt_t blob(pmt::cdr(msg));
if (!pmt::is_blob(blob))
throw std::runtime_error("HDLC framer: PMT must be blob");
std::vector<unsigned char> pkt(pmt::blob_length(blob));
memcpy(&pkt[0], (const unsigned char*)pmt::blob_data(blob), pkt.size());
// calc CRC
unsigned int crc = crc_ccitt(pkt);
// append CRC
pkt.insert(pkt.end(), crc & 0xFF);
pkt.insert(pkt.end(), (crc >> 8) & 0xFF);
// unpack to LSb bits
std::vector<unsigned char> pkt_bits = unpack(pkt);
// bitstuff
stuff(pkt_bits);
// add framing
const unsigned char framing[] = { 0, 1, 1, 1, 1, 1, 1, 0 };
std::vector<unsigned char> framing_vec(framing, framing + sizeof(framing));
pkt_bits.insert(pkt_bits.begin(), framing_vec.begin(), framing_vec.end());
pkt_bits.insert(pkt_bits.end(), framing_vec.begin(), framing_vec.end());
// make sure we have the space. unfortunately, we didn't know
// until now, since the stuffing must be calculated. we'll just
// save it for next time.
if ((size_t)noutput_items < (oidx + pkt_bits.size())) {
d_leftovers.insert(d_leftovers.end(), pkt_bits);
return oidx;
}
// produce
memcpy(out + oidx, &pkt_bits[0], pkt_bits.size());
// start tag
add_item_tag(
0, nitems_written(0) + oidx, d_frame_tag, pmt::from_long(pkt_bits.size()), d_me);
oidx += pkt_bits.size();
// return # output bits
return oidx;
}
} /* namespace digital */
} /* namespace gr */
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