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RTI Connext C API Version 7.4.0
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DDS_SUBSCRIPTION_MATCHED_STATUS More...
Data Fields | |
| DDS_Long | total_count |
| The total cumulative number of times that this DDS_DataReader discovered a "match" with a DDS_DataWriter. More... | |
| DDS_Long | total_count_change |
| The changes in total_count since the last time the listener was called or the status was read. More... | |
| DDS_Long | current_count |
| The current number of DataWriters with which the DDS_DataReader is matched. More... | |
| DDS_Long | current_count_peak |
| <<extension>> Greatest number of DataWriters that matched this DataReader simultaneously. More... | |
| DDS_Long | current_count_change |
| The change in current_count since the last time the listener was called or the status was read. More... | |
| DDS_InstanceHandle_t | last_publication_handle |
| This InstanceHandle can be used to look up which remote DDS_DataWriter was the last to cause this DataReader's status to change, using DDS_DataReader_get_matched_publication_data. More... | |
DDS_SUBSCRIPTION_MATCHED_STATUS
A "match" happens when the DDS_DataReader finds a DDS_DataWriter with the same DDS_Topic, same or compatible data type, and an offered QoS that is compatible with that requested by the DDS_DataReader. (For information on compatible data types, see the Extensible Types Guide.)
This status is also changed (and the listener, if any, called) when a match is ended. A local DDS_DataReader will become "unmatched" from a remote DDS_DataWriter when that DDS_DataWriter goes away for any of the following reasons:
The DDS_DomainParticipant containing the matched DDS_DataWriter has lost liveliness.
This DataReader or the matched DataWriter has changed QoS such that the entities are now incompatible.
This status may reflect changes from multiple match or unmatch events, and the DDS_SubscriptionMatchedStatus::current_count_change can be used to determine the number of changes since the listener was called back or the status was checked.
Note: A DataWriter's loss of liveliness (which is determined by DDS_LivelinessQosPolicyKind) does not trigger an unmatch event. So a DataWriter may still match even though its liveliness is lost.
| DDS_Long DDS_SubscriptionMatchedStatus::total_count |
The total cumulative number of times that this DDS_DataReader discovered a "match" with a DDS_DataWriter.
This number increases whenever a new match is discovered. It does not decrease when an existing match goes away for any of the reasons described in DDS_SubscriptionMatchedStatus.
| DDS_Long DDS_SubscriptionMatchedStatus::total_count_change |
The changes in total_count since the last time the listener was called or the status was read.
Note that this number will never be negative (because it's the total number of times the DataReader ever matched with a DataWriter).
| DDS_Long DDS_SubscriptionMatchedStatus::current_count |
The current number of DataWriters with which the DDS_DataReader is matched.
This number increases when a new match is discovered and decreases when an existing match goes away for any of the reasons described in DDS_SubscriptionMatchedStatus.
| DDS_Long DDS_SubscriptionMatchedStatus::current_count_peak |
<<extension>> Greatest number of DataWriters that matched this DataReader simultaneously.
That is, there was no moment in time when more than this many DataWriters matched this DataReader. (As a result, total_count can be higher than current_count_peak.)
| DDS_Long DDS_SubscriptionMatchedStatus::current_count_change |
The change in current_count since the last time the listener was called or the status was read.
Note that a negative current_count_change means that one or more DataWriters have become unmatched for one or more of the reasons described in DDS_SubscriptionMatchedStatus.
| DDS_InstanceHandle_t DDS_SubscriptionMatchedStatus::last_publication_handle |
This InstanceHandle can be used to look up which remote DDS_DataWriter was the last to cause this DataReader's status to change, using DDS_DataReader_get_matched_publication_data.
If the DataWriter no longer matches this DataReader due to any of the reasons in DDS_SubscriptionMatchedStatus except incompatible QoS, then the DataWriter has been purged from this DataReader's DomainParticipant discovery database. (See the "Discovery Overview" section of the User's Manual.) In that case, the DDS_DataReader_get_matched_publication_data method will not be able to return information about the DataWriter. The only way to get information about the lost DataWriter is if you cached the information previously.