#include <ddtMemoryAccessor.hpp>

	DdtMemoryAccessor ()

	DdtMemoryAccessor (const std::string &shm_id, const std::string &data_stream_identifier, DdtLogger *logger, const uint64_t time_window=0, const int32_t reading_interval=10)

virtual	~DdtMemoryAccessor ()

const uint32_t	ComputeChecksum (DataSampleShared *const data_sample_shared)

const uint32_t	ComputeChecksum (DataSample *const data_sample)

int32_t	OpenSharedMemory ()

void	CloseSharedMemory ()

void	WriteData (const int32_t writer_index, const int32_t topic_id, const int32_t sample_id, const uint8_t datavec, const int32_t datavec_size, const uint8_t metadata_vec, const int32_t metadatavec_size, const uint64_t timestamp)

void	StartReading ()

void	StopReading ()

void	SetSizeConstraints (const int32_t max_sample_size, const int32_t space)

void	Reattach ()

void	NewData ()

void	get_data_packet (std::string stream_identifier, uint32_t checksum, int32_t sample_length, int64_t writer_idx, uint64_t timestamp, DataSample *sample)

bool	get_data_available ()

int32_t	get_number_of_unread_elements ()

SignalT *	DataAvailableSignal ()

void	Reset ()

void	set_pub_unreg (const bool STATE)

void	set_compute_checksum (const bool compute_crc)

bool	get_compute_checksum () const

bool	get_is_initialized () const

Detailed Description

This class provides the functionalities to access created shared memories.

Constructor & Destructor Documentation

◆ DdtMemoryAccessor() [1/2]

DdtMemoryAccessor::DdtMemoryAccessor ( )

Constructor

◆ DdtMemoryAccessor() [2/2]

DdtMemoryAccessor::DdtMemoryAccessor	(	const std::string &	shm_id,
		const std::string &	data_stream_identifier,
		DdtLogger *	logger,
		const uint64_t	time_window = 0,
		const int32_t	reading_interval = 10 )

explicit

Constructor

Parameters

shm_id	The shared memory identifier.
data_stream_identifier	The data stream identifier.
logger	A DDT logger object (no transfer of ownership).
time_window	Specifies when data samples are dropped in [ms].
reading_interval	The reading interval in [ms].

◆ ~DdtMemoryAccessor()

DdtMemoryAccessor::~DdtMemoryAccessor ( )

virtual

Destructor

Member Function Documentation

◆ CloseSharedMemory()

void DdtMemoryAccessor::CloseSharedMemory ( )

Close shared memory specified by the stream identifier.

◆ ComputeChecksum() [1/2]

const uint32_t DdtMemoryAccessor::ComputeChecksum ( DataSample *const data_sample )

Computes a crc32 checksum based on the Slicing-by-16 algorithm.

Parameters

data_sample The data sample.

Returns: The computed checksum.

◆ ComputeChecksum() [2/2]

const uint32_t DdtMemoryAccessor::ComputeChecksum ( DataSampleShared *const data_sample_shared )

Computes a crc32 checksum based on the Slicing-by-16 algorithm.

Parameters

data_sample_shared The data sample.

Returns: The computed checksum.

◆ DataAvailableSignal()

SignalT * DdtMemoryAccessor::DataAvailableSignal ( )

Method for the connection to the data available signal.

Returns: Boost signal used for the event handling.

◆ get_compute_checksum()

bool DdtMemoryAccessor::get_compute_checksum ( ) const

Get compute_checksum.

Returns: Flag indicating if the checksum computation is switched on / off.

◆ get_data_available()

bool DdtMemoryAccessor::get_data_available ( )

Returns true if size of the packets list is > 0.

Returns: True if size of the packets list is > 0.

◆ get_data_packet()

void DdtMemoryAccessor::get_data_packet	(	std::string *	stream_identifier,
		uint32_t *	checksum,
		int32_t *	sample_length,
		int64_t *	writer_idx,
		uint64_t *	timestamp,
		DataSample **	sample )

The oldest DataPacket from the list is obtained by calling this function.

Parameters

stream_identifier	The data stream identifier.
checksum	The computed checksum.
sample_length	The length of the data sample.
writer_idx	The writer index.
timestamp	The timestamp of the data packet.
sample	The data sample.

The checksum computation is switched off per default. If the checksum is zero the writer did not compute it. In that case there is no need for the reader to perform the computation.

◆ get_is_initialized()

bool DdtMemoryAccessor::get_is_initialized ( ) const

Get is_initialized.

Returns: Flag indicating if initialization was successful.

◆ get_number_of_unread_elements()

int32_t DdtMemoryAccessor::get_number_of_unread_elements ( )

Returns the number of unread elements.

Returns: The number of unread elements.

◆ NewData()

void DdtMemoryAccessor::NewData ( )

This function is called from DdtDataSubscribers or from the data broker when new data was written into shared memory. It increases the number of unread elements.

◆ OpenSharedMemory()

int32_t DdtMemoryAccessor::OpenSharedMemory ( )

Opens an already created shared memory specified by the stream identifier.

Returns: 1 if SHM was opened successfully, -1 otherwise.

◆ Reattach()

void DdtMemoryAccessor::Reattach ( )

Reattaches to shared memory by closing and opening it again.

◆ Reset()

void DdtMemoryAccessor::Reset ( )

Resets the reader index and the number of unread elements after a publisher was restarted.

◆ set_compute_checksum()

void DdtMemoryAccessor::set_compute_checksum ( const bool compute_crc )

Sets compute_checksum.

Parameters

compute_crc Specifies if the checksum computation is switched on / off.

◆ set_pub_unreg()

void DdtMemoryAccessor::set_pub_unreg ( const bool STATE )

Sets the pub_unreg flag.

Parameters

STATE Specifies if a publisher was unregistered.

◆ SetSizeConstraints()

void DdtMemoryAccessor::SetSizeConstraints	(	const int32_t	max_sample_size,
		const int32_t	space )

Sets the maximum sample size and the additional space for the meta.

Parameters

max_sample_size	Maximum sample size.
space	Additional space required for the meta data.

◆ StartReading()

void DdtMemoryAccessor::StartReading ( )

Creates a thread for reading data from the shared memory.

◆ StopReading()

void DdtMemoryAccessor::StopReading ( )

Stops the reading thread.

◆ WriteData()

void DdtMemoryAccessor::WriteData	(	const int32_t	writer_index,
		const int32_t	topic_id,
		const int32_t	sample_id,
		const uint8_t *	datavec,
		const int32_t	datavec_size,
		const uint8_t *	metadata_vec,
		const int32_t	metadatavec_size,
		const uint64_t	timestamp )

Writes the data into shared memory.

Parameters

writer_index
topic_id	The topic ID.
sample_id	The sample ID.
datavec	A vector containing the data.
datavec_size	The size of the data vector.
metadata_vec	A vector containing the meta data.
metadatavec_size	The size of the meta data vector.
timestamp	The timestamp when the data was written into SHM.

The writer index of a DataPacket is set to -1 per default. If WriteData() is called from a publisher application the current writer index needs to be attached to the data packet. If WriteData() is called from a broker the received DataPacket contains the source writer index. Note: If the publisher stops publishing and get restarted, the reader index is not reset!

The checksum computation is switched off per default and will only be computed if a publisher is started with the checksum commandline parameter set to true

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

datatransfer/memoryaccessorlib/src/include/ddt/ddtMemoryAccessor.hpp
datatransfer/memoryaccessorlib/src/ddtMemoryAccessor.cpp