Function dds_takecdr

Function Documentation

dds_return_t dds_takecdr(dds_entity_t reader_or_condition, struct ddsi_serdata **buf, uint32_t maxs, dds_sample_info_t *si, uint32_t mask)

Access the collection of serialized data values (of same type) and sample info from the data reader, readcondition or querycondition.

This call accesses the serialized data from the data reader, readcondition or querycondition and makes it available to the application. The serialized data is made available through ddsi_serdata structures. Once read the data is removed from the reader and cannot be ‘read’ or ‘taken’ again.

Return value provides information about the number of samples read, which will be <= maxs. Based on the count, the buffer will contain serialized data to be read only when valid_data bit in sample info structure is set. The buffer required for data values, could be allocated explicitly or can use the memory from data reader to prevent copy. In the latter case, buffer and sample_info should be returned back, once it is no longer using the data.

Parameters

  • reader_or_condition – [in] Reader, readcondition or querycondition entity.

  • buf – [out] An array of pointers to ddsi_serdata structures that contain the serialized data. The pointers can be NULL.

  • maxs – [in] Maximum number of samples to read.

  • si – [out] Pointer to an array of dds_sample_info_t returned for each data value.

  • mask – [in] Filter the data based on dds_sample_state_t|dds_view_state_t|dds_instance_state_t.

Return values

  • >=0 – Number of samples read.

  • DDS_RETCODE_ERROR – An internal error has occurred.

  • DDS_RETCODE_BAD_PARAMETER – One of the given arguments is not valid.

  • DDS_RETCODE_ILLEGAL_OPERATION – The operation is invoked on an inappropriate object.

  • DDS_RETCODE_ALREADY_DELETED – The entity has already been deleted.

  • DDS_RETCODE_PRECONDITION_NOT_MET – The precondition for this operation is not met.

Returns

A dds_return_t with the number of samples read or an error code.