Default header formatter for PDU formatting. More...

#include <gnuradio/digital/header_format_default.h>

Public Member Functions
	header_format_default (const std::string &access_code, int threshold, int bps)

virtual	~header_format_default ()

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)

virtual size_t	header_nbits () const

bool	set_access_code (const std::string &access_code)

unsigned long long	access_code () const

void	set_threshold (unsigned int thresh=0)

unsigned int	threshold () 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 &access_code, int threshold, int bps=1)

Protected Member Functions
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...

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...

Protected Attributes
uint64_t	d_access_code
	register to hold the access code More...

size_t	d_access_code_len
	length in bits of the access code More...

uint16_t	d_bps
	bits/sec of payload modulation More...

unsigned long long	d_data_reg
	used to look for access_code More...

unsigned long long	d_mask

unsigned int	d_threshold
	how many bits may be wrong in sync vector More...

int	d_pkt_len
	Length of the packet to put into the output buffer. More...

int	d_pkt_count
	Number of bytes bits already received. More...

int	d_nbits
	num bits processed since reset More...

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

Default header formatter for PDU formatting.

Used to handle the default packet header.

See the parent class header_format_base for details of how these classes operate.

The default header created in this base class consists of an access code and the packet length. The length is encoded as a 16-bit value repeated twice:

  | access code | hdr | payload |

Where the access code is <= 64 bits and hdr is:

  |  0 -- 15 | 16 -- 31 |
  | pkt len  | pkt len  |

The access code and header are formatted for network byte order.

This header generator does not calculate or append a CRC to the packet. Use the CRC32 Async block for that before adding the header. The header's length will then measure the payload plus the CRC length (4 bytes for a CRC32).

The default header parser produces a PMT dictionary that contains the following keys. All formatter blocks MUST produce these two values in any dictionary.

"payload symbols": the number of symbols in the payload. The payload decoder will have to know how this relates to the number of bits received. This block knows nothing about the payload modulation or the number of bits/symbol. Use the gr::digital::header_format_counter for that purpose.

See also: header_format_counter; header_format_crc; header_format_ofdm

Constructor & Destructor Documentation

◆ header_format_default()

gr::digital::header_format_default::header_format_default	(	const std::string &	access_code,
		int	threshold,
		int	bps
	)

◆ ~header_format_default()

virtual gr::digital::header_format_default::~header_format_default ( )

virtual

Member Function Documentation

◆ access_code()

unsigned long long gr::digital::header_format_default::access_code ( ) const

Returns the formatted access code as a 64-bit register.

◆ enter_have_header()

virtual void gr::digital::header_format_default::enter_have_header ( int payload_len )

protectedvirtual

Header found, setup for pulling in the hard decision bits.

Reimplemented from gr::digital::header_format_base.

◆ enter_have_sync()

virtual void gr::digital::header_format_default::enter_have_sync ( )

protectedvirtual

Access code found, start getting the header.

Reimplemented from gr::digital::header_format_base.

◆ format()

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

virtual

Creates a header from the access code and packet length and creates an output header as a PMT vector in the form:

  | access code | pkt len | pkt len |

Parameters

nbytes_in	The length (in bytes) of the `input` payload
input	An array of unsigned chars of the packet payload
output	A pmt::u8vector with the new header prepended onto the input data.
info	A pmt::dict containing meta data and info about the PDU (generally from the metadata portion of the input PDU). Data can be extracted from this for the header formatting or inserted.

Implements gr::digital::header_format_base.

Reimplemented in gr::digital::header_format_counter.

◆ header_nbits()

virtual size_t gr::digital::header_format_default::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_counter.

◆ header_ok()

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

protectedvirtual

Verify that the header is valid.

Implements gr::digital::header_format_base.

Reimplemented in gr::digital::header_format_counter.

◆ header_payload()

virtual int gr::digital::header_format_default::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_counter.

◆ make()

static sptr gr::digital::header_format_default::make	(	const std::string &	access_code,
		int	threshold,
		int	bps = `1`
	)

static

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

Parameters

access_code	An access code that is used to find and synchronize the start of a packet. Used in the parser and in other blocks like a corr_est block that helps trigger the receiver. Can be up to 64-bits long.
threshold	How many bits can be wrong in the access code and still count as correct.
bps	The number of bits/second used in the payload's modulator.

◆ parse()

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

virtual

Parses a header of the form:

  | access code | pkt len | pkt len | payload |

This is implemented as a state machine that starts off searching for the access code. Once found, the access code is used to find the start of the packet and the following header. This default header encodes the length of the payload a 16 bit integer twice. The state machine finds the header and checks that both payload length values are the same. It then goes into its final state that reads in the payload (based on the payload length) and produces a payload as a PMT u8 vector of packed bytes.

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.

Implements gr::digital::header_format_base.

◆ set_access_code()

bool gr::digital::header_format_default::set_access_code ( const std::string & access_code )

Updates the access code. Must be a string of 1's and 0's and <= 64 bits.

◆ set_threshold()

void gr::digital::header_format_default::set_threshold ( unsigned int thresh = 0 )

Sets the threshold for number of access code bits can be in error before detection. Defaults to 0.

◆ threshold()

unsigned int gr::digital::header_format_default::threshold ( ) const

Returns threshold value for access code detection.

Member Data Documentation

◆ d_access_code

uint64_t gr::digital::header_format_default::d_access_code

protected

register to hold the access code

◆ d_access_code_len

size_t gr::digital::header_format_default::d_access_code_len

protected

length in bits of the access code

◆ d_bps

uint16_t gr::digital::header_format_default::d_bps

protected

bits/sec of payload modulation

◆ d_data_reg

unsigned long long gr::digital::header_format_default::d_data_reg

protected

used to look for access_code

◆ d_mask

unsigned long long gr::digital::header_format_default::d_mask

protected

masks access_code bits (top N bits are set where N is the number of bits in the access code)

◆ d_nbits

int gr::digital::header_format_default::d_nbits

protected

num bits processed since reset

◆ d_pkt_count

int gr::digital::header_format_default::d_pkt_count

protected

Number of bytes bits already received.

◆ d_pkt_len

int gr::digital::header_format_default::d_pkt_len

protected

Length of the packet to put into the output buffer.

◆ d_threshold

unsigned int gr::digital::header_format_default::d_threshold

protected

how many bits may be wrong in sync vector

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

header_format_default.h

Public Member Functions

Static Public Member Functions

Protected Member Functions

Protected Attributes

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

◆ header_format_default()

◆ ~header_format_default()

Member Function Documentation

◆ access_code()

◆ enter_have_header()

◆ enter_have_sync()

◆ format()

◆ header_nbits()

◆ header_ok()

◆ header_payload()

◆ make()

◆ parse()

◆ set_access_code()

◆ set_threshold()

◆ threshold()

Member Data Documentation

◆ d_access_code

◆ d_access_code_len

◆ d_bps

◆ d_data_reg

◆ d_mask

◆ d_nbits

◆ d_pkt_count

◆ d_pkt_len

◆ d_threshold