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/* -*- c++ -*- */
/* Copyright 2016 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.
*/
#ifndef INCLUDED_DIGITAL_HEADER_FORMAT_CRC_H
#define INCLUDED_DIGITAL_HEADER_FORMAT_CRC_H
#include <pmt/pmt.h>
#include <gnuradio/digital/api.h>
#include <gnuradio/digital/header_format_default.h>
#include <boost/crc.hpp>
namespace gr {
namespace digital {
/*!
* \brief Header formatter that includes the payload length,
* packet number, and a CRC check on the header.
* \ingroup packet_operators_blk
*
* \details
*
* Child class of header_format_base. This version's header
* format looks like:
*
* \li length (12 bits): length of the payload
* \li number (12 bits): packet number
* \li CRC8 (8 bits): A CRC8 check on the header contents
*
* Instead of duplicating the payload length, we only add it once
* and use the CRC8 to make sure it's correctly received.
*
* \verbatim
| 0 -- 11 | 12 -- 23 | 24 -- 31 |
| len | pkt len | CRC8 |
\endverbatim
*
* Reimplements packet_header_default in the style of the
* header_format_base.
*/
class DIGITAL_API header_format_crc
: public header_format_base
{
public:
header_format_crc(const std::string &len_key_name="packet_len",
const std::string &num_key_name="packet_num");
virtual ~header_format_crc();
void set_header_num(unsigned header_num) { d_header_number = header_num; };
/*!
* \brief Encodes the header information in the given tags into
* bits and places them into \p out.
*
* \details
* Uses the following header format:
* - Bits 0-11: The packet length (what was stored in the tag with key \p len_tag_key)
* - Bits 12-23: The header number (counts up everytime this function is called)
* - Bit 24-31: 8-Bit CRC
*/
virtual bool format(int nbytes_in,
const unsigned char *input,
pmt::pmt_t &output,
pmt::pmt_t &info);
virtual bool parse(int nbits_in,
const unsigned char *input,
std::vector<pmt::pmt_t> &info,
int &nbits_processed);
/*!
* Returns the length of the formatted header in bits.
*/
virtual size_t header_nbits() const;
/*!
* Factory to create an async packet header formatter; returns
* an sptr to the object.
*/
static sptr make(const std::string &len_key_name="packet_len",
const std::string &num_key_name="packet_num");
protected:
uint16_t d_header_number;
pmt::pmt_t d_len_key_name;
pmt::pmt_t d_num_key_name;
boost::crc_optimal<8, 0x07, 0xFF, 0x00, false, false> d_crc_impl;
//! Verify that the header is valid
virtual bool header_ok();
/*! Get info from the header; return payload length and package
* rest of data in d_info dictionary.
*/
virtual int header_payload();
};
} // namespace digital
} // namespace gr
#endif /* INCLUDED_DIGITAL_HEADER_FORMAT_CRC_H */
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