27.2 Ignoring Publications and Subscriptions

You can instruct Connext to locally ignore a publication or subscription. A publication/subscription is defined by the association of a Topic name, user data and partition set on the Publisher/Subscriber. After this call, any data written related to associated DataWriter/DataReader will be ignored.

The entity to ignore is identified by the handle argument. For ignore_publication(), the handle will be that of a DataWriter. For ignore_subscription(), that handle will be that of a DataReader.

This operation can be used to ignore local and remote entities:

• For local entities, you can obtain the handle argument by calling the get_instance_handle() operation for that particular entity.
• For remote entities, you can obtain the handle argument from the DDS_SampleInfo structure retrieved when reading DDS data samples available for the entity’s built-in DataReader.

DDS_ReturnCode_t ignore_publication  (const DDS_InstanceHandle_t &  handle)

DDS_ReturnCode_t ignore_subscription (const DDS_InstanceHandle_t &  handle)

Caution: There is no way to reverse these operations.

Figure 27.2: Ignoring Publications provides an example.

Figure 27.2: Ignoring Publications

class MyPublicationBuiltinTopicDataListener : public DDSDataReaderListener

{
	public:
	virtual void on_data_available(DDSDataReader *reader);
	// ......
};
void MyPublicationBuiltinTopicdataListener::on_data_available(
	DDSDataReader *reader) {
	DDSPublicationBuiltinTopicDataReader *builtinTopicDataReader =
		(DDS_PublicationBuiltinTopicDataReader *)reader;
	DDS_PublicationBuiltinTopicDataSeq data_seq;
	DDS_SampleInfoSeq info_seq;

	int = 0;
	if (builtinTopicDataReader->take(data_seq, info_seq,
		DDS_LENGTH_UNLIMITED, DDS_ANY_SAMPLE_STATE,
		DDS_ANY_VIEW_STATE, DDS_ANY_INSTANCE_STATE)
		!= DDS_RETCODE_OK)
	{
	// ... error
	}
	for (i = 0; i < data_seq.length(); ++i) {
		if (info_seq[i].valid_data) {
			// check user_data for access control
			if (data_seq[i].user_data[0] != 0x9) {
				if (builtinTopicDataReader->get_subscriber()
				->get_participant()
				->ignore_publication(
				info_seq[i].instance_handle)
					!= DDS_RETCODE_OK) {
					// ... error
				}
			}
		}
	}
if (builtinTopicDataReader->return_loan(data_seq, info_seq) !=
	DDS_RETCODE_OK) {
		...