gr::digital::header_format_crc Class Reference

Header formatter that includes the payload length, packet number, and a CRC check on the header. More...

#include <gnuradio/digital/header_format_crc.h>

Public Member Functions
	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)
virtual bool	format (int nbytes_in, const unsigned char *input, pmt::pmt_t &output, pmt::pmt_t &info)
	Encodes the header information in the given tags into bits and places them into out. More...
virtual bool	parse (int nbits_in, const unsigned char *input, std::vector< pmt::pmt_t > &info, int &nbits_processed)
virtual size_t	header_nbits () const
Public Member Functions inherited from gr::digital::header_format_base
	header_format_base ()
virtual	~header_format_base ()
sptr	base ()
sptr	formatter ()
size_t	header_nbytes () const

Static Public Member Functions
static sptr	make (const std::string &len_key_name="packet_len", const std::string &num_key_name="packet_num")

Protected Member Functions
virtual bool	header_ok ()
	Verify that the header is valid. More...
virtual int	header_payload ()
Protected Member Functions inherited from gr::digital::header_format_base
virtual void	enter_search ()
	Enter Search state of the state machine to find the access code. More...
virtual void	enter_have_sync ()
	Access code found, start getting the header. More...
virtual void	enter_have_header (int payload_len)
	Header found, setup for pulling in the hard decision bits. More...

Protected Attributes
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
Protected Attributes inherited from gr::digital::header_format_base
state_t	d_state
	state of the state machine More...
header_buffer	d_hdr_reg
	header_buffer object to hold header bits More...
pmt::pmt_t	d_info
	info captured from the header More...
gr::logger_ptr	d_logger
gr::logger_ptr	d_debug_logger

Additional Inherited Members
Public Types inherited from gr::digital::header_format_base
typedef boost::shared_ptr< header_format_base >	sptr
Protected Types inherited from gr::digital::header_format_base
enum	state_t { STATE_SYNC_SEARCH, STATE_HAVE_SYNC }

Detailed Description

Header formatter that includes the payload length, packet number, and a CRC check on the header.

Child class of header_format_base. This version's header format looks like:

• length (12 bits): length of the payload
• number (12 bits): packet number
• 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.

  |  0 -- 11 | 12 -- 23 | 24 -- 31 |
  |    len   | pkt len  |   CRC8   |

Reimplements packet_header_default in the style of the header_format_base.

Constructor & Destructor Documentation

gr::digital::header_format_crc::header_format_crc	(	const std::string &	len_key_name = "packet_len",
		const std::string &	num_key_name = "packet_num"
	)

virtual gr::digital::header_format_crc::~header_format_crc ( )

virtual

Member Function Documentation

virtual bool gr::digital::header_format_crc::format ( int  nbytes_in, const unsigned char *  input, pmt::pmt_t &  output, pmt::pmt_t &  info  )

virtual

Encodes the header information in the given tags into bits and places them into out.

Uses the following header format:

• Bits 0-11: The packet length (what was stored in the tag with key len_tag_key)
• Bits 12-23: The header number (counts up everytime this function is called)
• Bit 24-31: 8-Bit CRC

Implements gr::digital::header_format_base.

Reimplemented in gr::digital::header_format_ofdm.

virtual size_t gr::digital::header_format_crc::header_nbits ( ) const

virtual

Returns the length of the formatted header in bits.

Implements gr::digital::header_format_base.

Reimplemented in gr::digital::header_format_ofdm.

virtual bool gr::digital::header_format_crc::header_ok ( )

protectedvirtual

Verify that the header is valid.

Implements gr::digital::header_format_base.

virtual int gr::digital::header_format_crc::header_payload ( )

protectedvirtual

Get info from the header; return payload length and package rest of data in d_info dictionary.

Implements gr::digital::header_format_base.

Reimplemented in gr::digital::header_format_ofdm.

static sptr gr::digital::header_format_crc::make ( const std::string &  len_key_name = "packet_len", const std::string &  num_key_name = "packet_num"  )

static

Factory to create an async packet header formatter; returns an sptr to the object.

virtual bool gr::digital::header_format_crc::parse ( int  nbits_in, const unsigned char *  input, std::vector< pmt::pmt_t > &  info, int &  nbits_processed  )

virtual

Parses a header. This function is overloaded in the child class, which knows how to convert the incoming hard bits (0's and 1's) back into a packet header.

Parameters

nbits_in	The number of bits in the input array.
input	The input as hard decision bits.
info	A vector of pmt::dicts to hold any meta data or info about the PDU. When parsing the header, the formatter can add info from the header into this dict. Each packet has a single PMT dictionary of info, so the vector length is the number of packets received extracted during one call to this parser function.
nbits_processed	Number of input bits actually processed; If all goes well, this is nbits_in. A premature return after a bad header could be less than this.

MUST be overloaded.

Implements gr::digital::header_format_base.

Reimplemented in gr::digital::header_format_ofdm.

void gr::digital::header_format_crc::set_header_num ( unsigned  header_num )

inline

Member Data Documentation

boost::crc_optimal<8, 0x07, 0xFF, 0x00, false, false> gr::digital::header_format_crc::d_crc_impl

protected

uint16_t gr::digital::header_format_crc::d_header_number

protected

pmt::pmt_t gr::digital::header_format_crc::d_len_key_name

protected

pmt::pmt_t gr::digital::header_format_crc::d_num_key_name

protected

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The documentation for this class was generated from the following file:

• header_format_crc.h