Data Transfers

Data transfers happen through the pushPacket() method call of a REDHAWK component’s port object. This method transfers the data from the uses-side port to the corresponding connected provides-side port. The data is marshaled by the middleware (omniORB) and placed on a queue for processing by the receiving component. The implementations of the pushPacket() methods are maximized for the efficiency of data throughput while providing network-accessible ingest/egress of data and minimizing the complexity of the implementation.

Each implementation maintains the required behavior of providing an Signal Related Information (SRI) object before receiving any data transfers. This is accomplished by calling the pushSRI() method of the port with an SRI object. In most cases, a component takes the ingest SRI object received from an input port, makes any required modifications as necessary, and passes this object down stream over its output port. If a component does not provide an SRI object before its first pushPacket(), the port creates a default SRI object with nominal values to pass out the port.

The following sections explain the different methods for transferring supported data types by a component.

Vector Data

A component usually ingests and egresses data from its ports in the service function. A component with a provides-port (input), grabs data from the port using the getPacket() method. This method returns a dataTransfer object (described in DataTransfer Member Descriptions) from the input port’s data queue or a null/None value if the queue is empty.

The following code snippet is an example of the getPacket() method.

/**
   Grab data from the port's getPacket method
 */
bulkio::InFloatPort::dataTransfer *pkt;
pkt = inFloatPort->getPacket( bulkio::Const::NON_BLOCKING );

// check if a valid packet was returned
if ( pkt == NULL ) {
  return NOOP;
}

// check if any SRI changes occurred
if ( pkt->sriChanged ) {
  outFloatPort->pushSRI( pkt->SRI );
}

...   perform some algorithm on the data:  pkt->dataBuffer ...

The following table describes DataTransfer members.

DataTransfer Member Descriptions

The following code snippet is an example of the pushPacket() method call for vector data with sample parameters.

std::vector<short> data;

...  perform algorithm and save results to data vector ...

BULKIO::PrecisionUTCTime tstamp = bulkio::time::utils::now();
outShortPort->pushPacket( data, tstamp, false, "sample" );

The following table describes pushPacket() parameters for vector data.

pushPacket() Parameter Descriptions for Vector Data

String Data/XML Document

The following code snippet is an example of the pushPacket() method call for string data with sample parameters.

std::string data;

... generate some text data to transfer ...

outStringPort->pushPacket( data.c_str(), false, "sample" );

The following table describes pushPacket() parameters for string data.

pushPacket() Parameter Descriptions for String Data

URL/File Data

The following code snippet is an example of the pushPacket() method call for file transfers with sample parameters.

std::string uri;

uri = "file:///data/samples.8t";

... open the file, fill with samples of data, close the file ...

BULKIO::PrecisionUTCTime tstamp = bulkio::time::utils::now();
outURLPort->pushPacket( uri.c_str(), tstamp, false, "sample" );

The following table describes pushPacket() parameters for file transfers.

pushPacket() Parameter Descriptions for File Transfers

Data files may be sent via the Bulk Input/Output (BulkIO) dataFile type. When using the BulkIO dataFile type, a filename is passed to the pushPacket() method. The location of the file is specified by a URI that either points to the local file system or the Software-Defined Radio (SDR) file system. To support portability, use of the SDR file system is recommended.

URI Options

The following table describes the URI path options.

URI Options

SDDS Stream Definition

The SDDS Stream Definition object defines a multicast connection source for data from a network interface. The methods for the SDDS Stream Definition Interface do not follow the normal BulkIO pushPacket() convention; instead, the interface defines attach() and detach() methods. The attach() and detach() methods are provided in the following code snippet.

/**
 *  SDDS Stream Definition Interface
 */

/**
  *  attach : request to an attachment to a specified network data source
  */
char  *attach( BULKIO::SDDSStreamDefinition stream, const char * userid );

/**
  * detach: unlatch from a network data source
  */
void  detach( const char* attachId );

The following tables describe the attach() and detach() methods and the SDDS Stream Definition Member.

char* attach()

void detach()

SDDS Stream Definition Member Descriptions