FooDataReader Struct Reference
[DataReaders]

<<interface>> <<generic>> User data type-specific data reader. More...

Inheritance diagram for FooDataReader:

DDSDataReader DDSDomainEntity DDSEntity

List of all members.

Public Member Functions

virtual DDS_ReturnCode_t read (FooSeq &received_data, DDS_SampleInfoSeq &info_seq, DDS_Long max_samples, DDS_SampleStateMask sample_states, DDS_ViewStateMask view_states, DDS_InstanceStateMask instance_states)=0
 Access a collection of data samples from the DDSDataReader.
virtual DDS_ReturnCode_t take (FooSeq &received_data, DDS_SampleInfoSeq &info_seq, DDS_Long max_samples, DDS_SampleStateMask sample_states, DDS_ViewStateMask view_states, DDS_InstanceStateMask instance_states)=0
 Access a collection of data-samples from the DDSDataReader.
virtual DDS_ReturnCode_t read_w_condition (FooSeq &received_data, DDS_SampleInfoSeq &info_seq, DDS_Long max_samples, DDSReadCondition *condition)=0
 Accesses via FooDataReader::read the samples that match the criteria specified in the DDSReadCondition.
virtual DDS_ReturnCode_t take_w_condition (FooSeq &received_data, DDS_SampleInfoSeq &info_seq, DDS_Long max_samples, DDSReadCondition *condition)=0
 Analogous to FooDataReader::read_w_condition except it accesses samples via the FooDataReader::take operation.
virtual DDS_ReturnCode_t read_next_sample (Foo &received_data, DDS_SampleInfo &sample_info)=0
 Copies the next not-previously-accessed data value from the DDSDataReader.
virtual DDS_ReturnCode_t take_next_sample (Foo &received_data, DDS_SampleInfo &sample_info)=0
 Copies the next not-previously-accessed data value from the DDSDataReader.
virtual DDS_ReturnCode_t read_instance (FooSeq &received_data, DDS_SampleInfoSeq &info_seq, DDS_Long max_samples, const DDS_InstanceHandle_t &a_handle, DDS_SampleStateMask sample_states, DDS_ViewStateMask view_states, DDS_InstanceStateMask instance_states)=0
 Access a collection of data samples from the DDSDataReader.
virtual DDS_ReturnCode_t take_instance (FooSeq &received_data, DDS_SampleInfoSeq &info_seq, DDS_Long max_samples, const DDS_InstanceHandle_t &a_handle, DDS_SampleStateMask sample_states, DDS_ViewStateMask view_states, DDS_InstanceStateMask instance_states)=0
 Access a collection of data samples from the DDSDataReader.
virtual DDS_ReturnCode_t read_instance_w_condition (FooSeq &received_data, DDS_SampleInfoSeq &info_seq, DDS_Long max_samples, const DDS_InstanceHandle_t &previous_handle, DDSReadCondition *condition)=0
 Accesses via FooDataReader::read_instance the samples that match the criteria specified in the DDSReadCondition.
virtual DDS_ReturnCode_t take_instance_w_condition (FooSeq &received_data, DDS_SampleInfoSeq &info_seq, DDS_Long max_samples, const DDS_InstanceHandle_t &previous_handle, DDSReadCondition *condition)=0
 Accesses via FooDataReader::take_instance the samples that match the criteria specified in the DDSReadCondition.
virtual DDS_ReturnCode_t read_next_instance (FooSeq &received_data, DDS_SampleInfoSeq &info_seq, DDS_Long max_samples, const DDS_InstanceHandle_t &previous_handle, DDS_SampleStateMask sample_states, DDS_ViewStateMask view_states, DDS_InstanceStateMask instance_states)=0
 Access a collection of data samples from the DDSDataReader.
virtual DDS_ReturnCode_t take_next_instance (FooSeq &received_data, DDS_SampleInfoSeq &info_seq, DDS_Long max_samples, const DDS_InstanceHandle_t &previous_handle, DDS_SampleStateMask sample_states, DDS_ViewStateMask view_states, DDS_InstanceStateMask instance_states)=0
 Access a collection of data samples from the DDSDataReader.
virtual DDS_ReturnCode_t read_next_instance_w_condition (FooSeq &received_data, DDS_SampleInfoSeq &info_seq, DDS_Long max_samples, const DDS_InstanceHandle_t &previous_handle, DDSReadCondition *condition)=0
 Accesses via FooDataReader::read_next_instance the samples that match the criteria specified in the DDSReadCondition.
virtual DDS_ReturnCode_t take_next_instance_w_condition (FooSeq &received_data, DDS_SampleInfoSeq &info_seq, DDS_Long max_samples, const DDS_InstanceHandle_t &previous_handle, DDSReadCondition *condition)=0
 Accesses via FooDataReader::take_next_instance the samples that match the criteria specified in the DDSReadCondition.
virtual DDS_ReturnCode_t return_loan (FooSeq &received_data, DDS_SampleInfoSeq &info_seq)=0
 Indicates to the DDSDataReader that the application is done accessing the collection of received_data and info_seq obtained by some earlier invocation of read or take on the DDSDataReader.
virtual DDS_ReturnCode_t get_key_value (Foo &key_holder, const DDS_InstanceHandle_t handle)=0
 Retrieve the instance key that corresponds to an instance handle.
virtual DDS_InstanceHandle_t lookup_instance (const Foo &key_holder)=0
 Retrieves the instance handle that corresponds to an instance key_holder.

Static Public Member Functions

static FooDataReader * narrow (DDSDataReader *reader)
 Narrow the given DDSDataReader pointer to a FooDataReader pointer.

Detailed Description

<<interface>> <<generic>> User data type-specific data reader.

Defines the user data type specific reader interface generated for each application class.

The concrete user data type reader automatically generated by the implementation is an incarnation of this class.

See also:
DDSDataReader

Foo

FooDataWriter

rtiddsgen

Member Function Documentation

static FooDataReader* FooDataReader::narrow ( DDSDataReader *  reader  )  [static]

Narrow the given DDSDataReader pointer to a FooDataReader pointer.

virtual DDS_ReturnCode_t FooDataReader::read ( FooSeq &  received_data,
DDS_SampleInfoSeq &  info_seq,
DDS_Long  max_samples,
DDS_SampleStateMask  sample_states,
DDS_ViewStateMask  view_states,
DDS_InstanceStateMask  instance_states 
) [pure virtual]

Access a collection of data samples from the DDSDataReader.

This operation offers the same functionality and API as FooDataReader::take except that the samples returned remain in the DDSDataReader such that they can be retrieved again by means of a read or take operation.

Please refer to the documentation of FooDataReader::take() for details on the number of samples returned within the received_data and info_seq as well as the order in which the samples appear in these sequences.

The act of reading a sample changes its sample_state to DDS_READ_SAMPLE_STATE. If the sample belongs to the most recent generation of the instance, it will also set the view_state of the instance to be DDS_NOT_NEW_VIEW_STATE. It will not affect the instance_state of the instance.

Important: If the samples "returned" by this method are loaned from RTI Connext (see FooDataReader::take for more information on memory loaning), it is important that their contents not be changed. Because the memory in which the data is stored belongs to the middleware, any modifications made to the data will be seen the next time the same samples are read or taken; the samples will no longer reflect the state that was received from the network.

Parameters:
received_data <<inout>> User data type-specific FooSeq object where the received data samples will be returned.
info_seq <<inout>> A DDS_SampleInfoSeq object where the received sample info will be returned.
max_samples <<in>> The maximum number of samples to be returned. If the special value DDS_LENGTH_UNLIMITED is provided, as many samples will be returned as are available, up to the limits described in the documentation for FooDataReader::take().
sample_states <<in>> Data samples matching one of these sample_states are returned.
view_states <<in>> Data samples matching one of these view_state are returned.
instance_states <<in>> Data samples matching ones of these instance_state are returned.
Returns:
One of the Standard Return Codes, DDS_RETCODE_PRECONDITION_NOT_MET, DDS_RETCODE_NO_DATA or DDS_RETCODE_NOT_ENABLED.
See also:
FooDataReader::read_w_condition, FooDataReader::take, FooDataReader::take_w_condition

DDS_LENGTH_UNLIMITED

virtual DDS_ReturnCode_t FooDataReader::take ( FooSeq &  received_data,
DDS_SampleInfoSeq &  info_seq,
DDS_Long  max_samples,
DDS_SampleStateMask  sample_states,
DDS_ViewStateMask  view_states,
DDS_InstanceStateMask  instance_states 
) [pure virtual]

Access a collection of data-samples from the DDSDataReader.

The operation will return the list of samples received by the DDSDataReader since the last FooDataReader::take operation that match the specified DDS_SampleStateMask, DDS_ViewStateMask and DDS_InstanceStateMask.

This operation may fail with DDS_RETCODE_ERROR if DDS_DataReaderResourceLimitsQosPolicy::max_outstanding_reads limit has been exceeded.

The actual number of samples returned depends on the information that has been received by the middleware as well as the DDS_HistoryQosPolicy, DDS_ResourceLimitsQosPolicy, DDS_DataReaderResourceLimitsQosPolicy and the characteristics of the data-type that is associated with the DDSDataReader:

If the read or take succeeds and the number of samples returned has been limited (by means of a maximum limit, as listed above, or insufficient DDS_SampleInfo resources), the call will complete successfully and provide those samples the reader is able to return. The user may need to make additional calls, or return outstanding loaned buffers in the case of insuffificient resources, in order to access remaining samples.

Note that in the case where the DDSTopic associated with the DDSDataReader is bound to a data-type that has no key definition, then there will be at most one instance in the DDSDataReader. So the per-sample limits will apply.

The act of taking a sample removes it from RTI Connext so it cannot be read or taken again. If the sample belongs to the most recent generation of the instance, it will also set the view_state of the sample's instance to DDS_NOT_NEW_VIEW_STATE. It will not affect the instance_state of the sample's instance.

After FooDataReader::take completes, received_data and info_seq will be of the same length and contain the received data.

If the sequences are empty (maximum size equals 0) when the FooDataReader::take is called, the samples returned in the received_data and the corresponding info_seq are 'loaned' to the application from buffers provided by the DDSDataReader. The application can use them as desired and has guaranteed exclusive access to them.

Once the application completes its use of the samples it must 'return the loan' to the DDSDataReader by calling the FooDataReader::return_loan operation.

Important: When you loan data from the middleware, you must not keep any pointers to any part of the data samples or the DDS_SampleInfo objects after the call to FooDataReader::return_loan. Returning the loan places the objects back into a pool, allowing the middleware to overwrite them with new data.

Note: While you must call FooDataReader::return_loan at some point, you do not have to do so before the next FooDataReader::take call. However, failure to return the loan will eventually deplete the DDSDataReader of the buffers it needs to receive new samples and eventually samples will start to be lost. The total number of buffers available to the DDSDataReader is specified by the DDS_ResourceLimitsQosPolicy and the DDS_DataReaderResourceLimitsQosPolicy.

If the sequences are not empty (maximum size not equal to 0 and length not equal to 0) when FooDataReader::take is called, samples are copied to received_data and info_seq. The application will not need to call FooDataReader::return_loan.

The order of the samples returned to the caller depends on the DDS_PresentationQosPolicy.

In any case, the relative order between the samples of one instance is consistent with the DESTINATION_ORDER policy:

If the DDSDataReader has no samples that meet the constraints, the method will fail with DDS_RETCODE_NO_DATA.

In addition to the collection of samples, the read and take operations also use a collection of DDS_SampleInfo structures.

SEQUENCES USAGE IN TAKE AND READ

The initial (input) properties of the received_data and info_seq collections will determine the precise behavior of the read or take operation. For the purposes of this description, the collections are modeled as having these properties: The initial values of the owns, len and max_len properties for the received_data and info_seq collections govern the behavior of the read and take operations as specified by the following rules:

  1. The values of owns, len and max_len properties for the two collections must be identical. Otherwise read/take will fail with DDS_RETCODE_PRECONDITION_NOT_MET.

  2. On successful output, the values of owns, len and max_len will be the same for both collections.

  3. If the initial max_len==0, then the received_data and info_seq collections will be filled with elements that are loaned by the DDSDataReader. On output, owns will be FALSE, len will be set to the number of values returned, and max_len will be set to a value verifying max_len >= len. The use of this variant allows for zero-copy access to the data and the application will need to return the loan to the DDSDataWriter using FooDataReader::return_loan.

  4. If the initial max_len>0 and owns==FALSE, then the read or take operation will fail with DDS_RETCODE_PRECONDITION_NOT_MET. This avoids the potential hard-to-detect memory leaks caused by an application forgetting to return the loan.

  5. If initial max_len>0 and owns==TRUE, then the read or take operation will copy the received_data values and DDS_SampleInfo values into the elements already inside the collections. On output, owns will be TRUE, len will be set to the number of values copied and max_len will remain unchanged. The use of this variant forces a copy but the application can control where the copy is placed and the application will not need to return the loan. The number of samples copied depends on the relative values of max_len and max_samples:

    • If max_samples == LENGTH_UNLIMITED, then at most max_len values will be copied. The use of this variant lets the application limit the number of samples returned to what the sequence can accommodate.

    • If max_samples <= max_len, then at most max_samples values will be copied. The use of this variant lets the application limit the number of samples returned to fewer that what the sequence can accommodate.

    • If max_samples > max_len, then the read or take operation will fail with DDS_RETCODE_PRECONDITION_NOT_MET. This avoids the potential confusion where the application expects to be able to access up to max_samples, but that number can never be returned, even if they are available in the DDSDataReader, because the output sequence cannot accommodate them.

As described above, upon completion, the received_data and info_seq collections may contain elements loaned from the DDSDataReader. If this is the case, the application will need to use FooDataReader::return_loan to return the loan once it is no longer using the received_data in the collection. When FooDataReader::return_loan completes, the collection will have owns=FALSE and max_len=0. The application can determine whether it is necessary to return the loan or not based on how the state of the collections when the read/take operation was called or by accessing the owns property. However, in many cases it may be simpler to always call FooDataReader::return_loan, as this operation is harmless (i.e., it leaves all elements unchanged) if the collection does not have a loan.

To avoid potential memory leaks, the implementation of the Foo and DDS_SampleInfo collections should disallow changing the length of a collection for which owns==FALSE. Furthermore, deleting a collection for which owns==FALSE should be considered an error.

On output, the collection of Foo values and the collection of DDS_SampleInfo structures are of the same length and are in a one-to-one correspondence. Each DDS_SampleInfo provides information, such as the source_timestamp, the sample_state, view_state, and instance_state, etc., about the corresponding sample.

Some elements in the returned collection may not have valid data. If the instance_state in the DDS_SampleInfo is DDS_NOT_ALIVE_DISPOSED_INSTANCE_STATE or DDS_NOT_ALIVE_NO_WRITERS_INSTANCE_STATE, then the last sample for that instance in the collection (that is, the one whose DDS_SampleInfo has sample_rank==0) does not contain valid data.

Samples that contain no data do not count towards the limits imposed by the DDS_ResourceLimitsQosPolicy. The act of reading/taking a sample sets its sample_state to DDS_READ_SAMPLE_STATE.

If the sample belongs to the most recent generation of the instance, it will also set the view_state of the instance to DDS_NOT_NEW_VIEW_STATE. It will not affect the instance_state of the instance.

This operation must be provided on the specialized class that is generated for the particular application data-type that is being read (Foo). If the DDSDataReader has no samples that meet the constraints, the operations fails with DDS_RETCODE_NO_DATA.

For an example on how take can be used, please refer to the receive example.

Parameters:
received_data <<inout>> User data type-specific FooSeq object where the received data samples will be returned.

Parameters:
info_seq <<inout>> A DDS_SampleInfoSeq object where the received sample info will be returned.
max_samples <<in>> The maximum number of samples to be returned. If the special value DDS_LENGTH_UNLIMITED is provided, as many samples will be returned as are available, up to the limits described above.
sample_states <<in>> Data samples matching one of these sample_states are returned.
view_states <<in>> Data samples matching one of these view_state are returned.
instance_states <<in>> Data samples matching one of these instance_state are returned.
Returns:
One of the Standard Return Codes, DDS_RETCODE_PRECONDITION_NOT_MET, DDS_RETCODE_NO_DATA or DDS_RETCODE_NOT_ENABLED.
See also:
FooDataReader::read

FooDataReader::read_w_condition, FooDataReader::take_w_condition

DDS_LENGTH_UNLIMITED

virtual DDS_ReturnCode_t FooDataReader::read_w_condition ( FooSeq &  received_data,
DDS_SampleInfoSeq &  info_seq,
DDS_Long  max_samples,
DDSReadCondition *  condition 
) [pure virtual]

Accesses via FooDataReader::read the samples that match the criteria specified in the DDSReadCondition.

This operation is especially useful in combination with DDSQueryCondition to filter data samples based on the content.

The specified DDSReadCondition must be attached to the DDSDataReader; otherwise the operation will fail with DDS_RETCODE_PRECONDITION_NOT_MET.

In case the DDSReadCondition is a plain DDSReadCondition and not the specialized DDSQueryCondition, the operation is equivalent to calling FooDataReader::read and passing as sample_states, view_states and instance_states the value of the corresponding attributes in the read_condition. Using this operation, the application can avoid repeating the same parameters specified when creating the DDSReadCondition.

The samples are accessed with the same semantics as FooDataReader::read.

If the DDSDataReader has no samples that meet the constraints, the operation will fail with DDS_RETCODE_NO_DATA.

Parameters:
received_data <<inout>> user data type-specific FooSeq object where the received data samples will be returned.
info_seq <<inout>> a DDS_SampleInfoSeq object where the received sample info will be returned.
max_samples <<in>> The maximum number of samples to be returned. If the special value DDS_LENGTH_UNLIMITED is provided, as many samples will be returned as are available, up to the limits described in the documentation for FooDataReader::take().
condition <<in>> the DDSReadCondition to select samples of interest. Cannot be NULL.
Returns:
One of the Standard Return Codes, DDS_RETCODE_PRECONDITION_NOT_MET, DDS_RETCODE_NO_DATA or DDS_RETCODE_NOT_ENABLED.
See also:
FooDataReader::read

FooDataReader::take, FooDataReader::take_w_condition

DDS_LENGTH_UNLIMITED

virtual DDS_ReturnCode_t FooDataReader::take_w_condition ( FooSeq &  received_data,
DDS_SampleInfoSeq &  info_seq,
DDS_Long  max_samples,
DDSReadCondition *  condition 
) [pure virtual]

Analogous to FooDataReader::read_w_condition except it accesses samples via the FooDataReader::take operation.

This operation is analogous to FooDataReader::read_w_condition except that it accesses samples via the FooDataReader::take operation.

The specified DDSReadCondition must be attached to the DDSDataReader; otherwise the operation will fail with DDS_RETCODE_PRECONDITION_NOT_MET.

The samples are accessed with the same semantics as FooDataReader::take.

This operation is especially useful in combination with DDSQueryCondition to filter data samples based on the content.

If the DDSDataReader has no samples that meet the constraints, the method will fail with DDS_RETCODE_NO_DATA.

Parameters:
received_data <<inout>> user data type-specific FooSeq object where the received data samples will be returned.
info_seq <<inout>> a DDS_SampleInfoSeq object where the received sample info will be returned.
max_samples <<in>> The maximum number of samples to be returned. If the special value DDS_LENGTH_UNLIMITED is provided, as many samples will be returned as are available, up to the limits described in the documentation for FooDataReader::take().
condition <<in>> the DDSReadCondition to select samples of interest. Cannot be NULL.
Returns:
One of the Standard Return Codes, DDS_RETCODE_PRECONDITION_NOT_MET, DDS_RETCODE_NO_DATA or DDS_RETCODE_NOT_ENABLED.
See also:
FooDataReader::read_w_condition, FooDataReader::read

FooDataReader::take

DDS_LENGTH_UNLIMITED

virtual DDS_ReturnCode_t FooDataReader::read_next_sample ( Foo &  received_data,
DDS_SampleInfo &  sample_info 
) [pure virtual]

Copies the next not-previously-accessed data value from the DDSDataReader.

This operation copies the next not-previously-accessed data value from the DDSDataReader. This operation also copies the corresponding DDS_SampleInfo. The implied order among the samples stored in the DDSDataReader is the same as for the FooDataReader::read operation.

The FooDataReader::read_next_sample operation is semantically equivalent to the FooDataReader::read operation, where the input data sequences has max_len=1, the sample_states=NOT_READ, the view_states=ANY_VIEW_STATE, and the instance_states=ANY_INSTANCE_STATE.

The FooDataReader::read_next_sample operation provides a simplified API to 'read' samples, avoiding the need for the application to manage sequences and specify states.

If there is no unread data in the DDSDataReader, the operation will fail with DDS_RETCODE_NO_DATA and nothing is copied.

Parameters:
received_data <<inout>> user data type-specific Foo object where the next received data sample will be returned. The received_data must have been fully allocated. Otherwise, this operation may fail.
sample_info <<inout>> a DDS_SampleInfo object where the next received sample info will be returned.
Returns:
One of the Standard Return Codes, DDS_RETCODE_NO_DATA or DDS_RETCODE_NOT_ENABLED.
See also:
FooDataReader::read

virtual DDS_ReturnCode_t FooDataReader::take_next_sample ( Foo &  received_data,
DDS_SampleInfo &  sample_info 
) [pure virtual]

Copies the next not-previously-accessed data value from the DDSDataReader.

This operation copies the next not-previously-accessed data value from the DDSDataReader and 'removes' it from the DDSDataReader so that it is no longer accessible. This operation also copies the corresponding DDS_SampleInfo. This operation is analogous to the FooDataReader::read_next_sample except for the fact that the sample is removed from the DDSDataReader.

The FooDataReader::take_next_sample operation is semantically equivalent to the FooDataReader::take operation, where the input data sequences has max_len=1, the sample_states=NOT_READ, the view_states=ANY_VIEW_STATE, and the instance_states=ANY_INSTANCE_STATE.

The FooDataReader::read_next_sample operation provides a simplified API to 'take' samples, avoiding the need for the application to manage sequences and specify states.

If there is no unread data in the DDSDataReader, the operation will fail with DDS_RETCODE_NO_DATA and nothing is copied.

Parameters:
received_data <<inout>> user data type-specific Foo object where the next received data sample will be returned. The received_data must have been fully allocated. Otherwise, this operation may fail.
sample_info <<inout>> a DDS_SampleInfo object where the next received sample info will be returned.
Returns:
One of the Standard Return Codes, DDS_RETCODE_NO_DATA or DDS_RETCODE_NOT_ENABLED.
See also:
FooDataReader::take

virtual DDS_ReturnCode_t FooDataReader::read_instance ( FooSeq &  received_data,
DDS_SampleInfoSeq &  info_seq,
DDS_Long  max_samples,
const DDS_InstanceHandle_t &  a_handle,
DDS_SampleStateMask  sample_states,
DDS_ViewStateMask  view_states,
DDS_InstanceStateMask  instance_states 
) [pure virtual]

Access a collection of data samples from the DDSDataReader.

This operation accesses a collection of data values from the DDSDataReader. The behavior is identical to FooDataReader::read, except that all samples returned belong to the single specified instance whose handle is a_handle.

Upon successful completion, the data collection will contain samples all belonging to the same instance. The corresponding DDS_SampleInfo verifies DDS_SampleInfo::instance_handle == a_handle.

The FooDataReader::read_instance operation is semantically equivalent to the FooDataReader::read operation, except in building the collection, the DDSDataReader will check that the sample belongs to the specified instance and otherwise it will not place the sample in the returned collection.

The behavior of the FooDataReader::read_instance operation follows the same rules as the FooDataReader::read operation regarding the pre-conditions and post-conditions for the received_data and sample_info. Similar to the FooDataReader::read, the FooDataReader::read_instance operation may 'loan' elements to the output collections, which must then be returned by means of FooDataReader::return_loan.

Similar to the FooDataReader::read, this operation must be provided on the specialized class that is generated for the particular application data-type that is being taken.

If the DDSDataReader has no samples that meet the constraints, the method will fail with DDS_RETCODE_NO_DATA.

This operation may fail with DDS_RETCODE_BAD_PARAMETER if the DDS_InstanceHandle_t a_handle does not correspond to an existing data-object known to the DDSDataReader.

Parameters:
received_data <<inout>> user data type-specific FooSeq object where the received data samples will be returned.
info_seq <<inout>> a DDS_SampleInfoSeq object where the received sample info will be returned.
max_samples <<in>> The maximum number of samples to be returned. If the special value DDS_LENGTH_UNLIMITED is provided, as many samples will be returned as are available, up to the limits described in the documentation for FooDataReader::take().
a_handle <<in>> The specified instance to return samples for. The method will fail with DDS_RETCODE_BAD_PARAMETER if the handle does not correspond to an existing data-object known to the DDSDataReader.
sample_states <<in>> data samples matching ones of these sample_states are returned
view_states <<in>> data samples matching ones of these view_state are returned
instance_states <<in>> data samples matching ones of these instance_state are returned
Returns:
One of the Standard Return Codes, DDS_RETCODE_PRECONDITION_NOT_MET, DDS_RETCODE_NO_DATA or DDS_RETCODE_NOT_ENABLED.
See also:
FooDataReader::read

DDS_LENGTH_UNLIMITED

virtual DDS_ReturnCode_t FooDataReader::take_instance ( FooSeq &  received_data,
DDS_SampleInfoSeq &  info_seq,
DDS_Long  max_samples,
const DDS_InstanceHandle_t &  a_handle,
DDS_SampleStateMask  sample_states,
DDS_ViewStateMask  view_states,
DDS_InstanceStateMask  instance_states 
) [pure virtual]

Access a collection of data samples from the DDSDataReader.

This operation accesses a collection of data values from the DDSDataReader. The behavior is identical to FooDataReader::take, except for that all samples returned belong to the single specified instance whose handle is a_handle.

The semantics are the same for the FooDataReader::take operation, except in building the collection, the DDSDataReader will check that the sample belongs to the specified instance, and otherwise it will not place the sample in the returned collection.

The behavior of the FooDataReader::take_instance operation follows the same rules as the FooDataReader::read operation regarding the pre-conditions and post-conditions for the received_data and sample_info. Similar to the FooDataReader::read, the FooDataReader::take_instance operation may 'loan' elements to the output collections, which must then be returned by means of FooDataReader::return_loan.

Similar to the FooDataReader::read, this operation must be provided on the specialized class that is generated for the particular application data-type that is being taken.

If the DDSDataReader has no samples that meet the constraints, the method fails with DDS_RETCODE_NO_DATA.

This operation may fail with DDS_RETCODE_BAD_PARAMETER if the DDS_InstanceHandle_t a_handle does not correspond to an existing data-object known to the DDSDataReader.

Parameters:
received_data <<inout>> user data type-specific FooSeq object where the received data samples will be returned.
info_seq <<inout>> a DDS_SampleInfoSeq object where the received sample info will be returned.
max_samples <<in>> The maximum number of samples to be returned. If the special value DDS_LENGTH_UNLIMITED is provided, as many samples will be returned as are available, up to the limits described in the documentation for FooDataReader::take().
a_handle <<in>> The specified instance to return samples for. The method will fail with DDS_RETCODE_BAD_PARAMETER if the handle does not correspond to an existing data-object known to the DDSDataReader.
sample_states <<in>> data samples matching ones of these sample_states are returned
view_states <<in>> data samples matching ones of these view_state are returned
instance_states <<in>> data samples matching ones of these instance_state are returned
Returns:
One of the Standard Return Codes, DDS_RETCODE_PRECONDITION_NOT_MET, DDS_RETCODE_NO_DATA or DDS_RETCODE_NOT_ENABLED.
See also:
FooDataReader::take

DDS_LENGTH_UNLIMITED

virtual DDS_ReturnCode_t FooDataReader::read_instance_w_condition ( FooSeq &  received_data,
DDS_SampleInfoSeq &  info_seq,
DDS_Long  max_samples,
const DDS_InstanceHandle_t &  previous_handle,
DDSReadCondition *  condition 
) [pure virtual]

Accesses via FooDataReader::read_instance the samples that match the criteria specified in the DDSReadCondition.

This operation accesses a collection of data values from the DDSDataReader. The behavior is identical to FooDataReader::read_instance, except that all returned samples satisfy the specified condition. In other words, on success, all returned samples belong to belong the single specified instance whose handle is a_handle, and for which the specified DDSReadCondition evaluates to TRUE.

The behavior of the FooDataReader::read_instance_w_condition operation follows the same rules as the FooDataReader::read operation regarding the pre-conditions and post-conditions for the received_data and sample_info. Similar to the FooDataReader::read, the FooDataReader::read_instance_w_condition operation may 'loan' elements to the output collections, which must then be returned by means of FooDataReader::return_loan.

Similar to FooDataReader::read, this operation must be provided on the specialized class that is generated for the particular application data-type that is being taken.

If the DDSDataReader has no samples that meet the constraints, the method will fail with DDS_RETCODE_NO_DATA.

Parameters:
received_data <<inout>> user data type-specific FooSeq object where the received data samples will be returned.
info_seq <<inout>> a DDS_SampleInfoSeq object where the received sample info will be returned.
max_samples <<in>> The maximum number of samples to be returned. If the special value DDS_LENGTH_UNLIMITED is provided, as many samples will be returned as are available, up to the limits described in the documentation for FooDataReader::take().
previous_handle <<in>> The 'next smallest' instance with a value greater than this value that has available samples will be returned.
condition <<in>> the DDSReadCondition to select samples of interest. Cannot be NULL.
Returns:
One of the Standard Return Codes, DDS_RETCODE_PRECONDITION_NOT_MET DDS_RETCODE_NO_DATA or DDS_RETCODE_NOT_ENABLED.
See also:
FooDataReader::read_next_instance

DDS_LENGTH_UNLIMITED

virtual DDS_ReturnCode_t FooDataReader::take_instance_w_condition ( FooSeq &  received_data,
DDS_SampleInfoSeq &  info_seq,
DDS_Long  max_samples,
const DDS_InstanceHandle_t &  previous_handle,
DDSReadCondition *  condition 
) [pure virtual]

Accesses via FooDataReader::take_instance the samples that match the criteria specified in the DDSReadCondition.

This operation accesses a collection of data values from the DDSDataReader and 'removes' them from the DDSDataReader. The behavior is identical to FooDataReader::take_instance, except that all returned samples satisfy the specified condition. In other words, on success, all returned samples belong to belong the single specified instance whose handle is a_handle, and for which the specified DDSReadCondition evaluates to TRUE.

The operation has the same behavior as FooDataReader::read_instance_w_condition, except that the samples are 'taken' from the DDSDataReader such that they are no longer accessible via subsequent 'read' or 'take' operations.

The behavior of the FooDataReader::take_instance_w_condition operation follows the same rules as the FooDataReader::read operation regarding the pre-conditions and post-conditions for the received_data and sample_info. Similar to the FooDataReader::read, the FooDataReader::take_instance_w_condition operation may 'loan' elements to the output collections, which must then be returned by means of FooDataReader::return_loan.

Similar to the FooDataReader::read, this operation must be provided on the specialized class that is generated for the particular application data-type that is being taken.

If the DDSDataReader has no samples that meet the constraints, the method will fail with DDS_RETCODE_NO_DATA.

Parameters:
received_data <<inout>> user data type-specific FooSeq object where the received data samples will be returned.
info_seq <<inout>> a DDS_SampleInfoSeq object where the received sample info will be returned.
max_samples <<in>> The maximum number of samples to be returned. If the special value DDS_LENGTH_UNLIMITED is provided, as many samples will be returned as are available, up to the limits described in the documentation for FooDataReader::take().
previous_handle <<in>> The 'next smallest' instance with a value greater than this value that has available samples will be returned.
condition <<in>> the DDSReadCondition to select samples of interest. Cannot be NULL.
Returns:
One of the Standard Return Codes, DDS_RETCODE_PRECONDITION_NOT_MET, or DDS_RETCODE_NO_DATA, DDS_RETCODE_NOT_ENABLED.
See also:
FooDataReader::take_next_instance

DDS_LENGTH_UNLIMITED

virtual DDS_ReturnCode_t FooDataReader::read_next_instance ( FooSeq &  received_data,
DDS_SampleInfoSeq &  info_seq,
DDS_Long  max_samples,
const DDS_InstanceHandle_t &  previous_handle,
DDS_SampleStateMask  sample_states,
DDS_ViewStateMask  view_states,
DDS_InstanceStateMask  instance_states 
) [pure virtual]

Access a collection of data samples from the DDSDataReader.

This operation accesses a collection of data values from the DDSDataReader where all the samples belong to a single instance. The behavior is similar to FooDataReader::read_instance, except that the actual instance is not directly specified. Rather, the samples will all belong to the 'next' instance with instance_handle 'greater' than the specified 'previous_handle' that has available samples.

This operation implies the existence of a total order 'greater-than' relationship between the instance handles. The specifics of this relationship are not all important and are implementation specific. The important thing is that, according to the middleware, all instances are ordered relative to each other. This ordering is between the instance handles; It should not depend on the state of the instance (e.g. whether it has data or not) and must be defined even for instance handles that do not correspond to instances currently managed by the DDSDataReader. For the purposes of the ordering, it should be 'as if' each instance handle was represented as unique integer.

The behavior of FooDataReader::read_next_instance is 'as if' the DDSDataReader invoked FooDataReader::read_instance, passing the smallest instance_handle among all the ones that: (a) are greater than previous_handle, and (b) have available samples (i.e. samples that meet the constraints imposed by the specified states).

The special value DDS_HANDLE_NIL is guaranteed to be 'less than' any valid instance_handle. So the use of the parameter value previous_handle == DDS_HANDLE_NIL will return the samples for the instance which has the smallest instance_handle among all the instances that contain available samples.

The operation FooDataReader::read_next_instance is intended to be used in an application-driven iteration, where the application starts by passing previous_handle == DDS_HANDLE_NIL, examines the samples returned, and then uses the instance_handle returned in the DDS_SampleInfo as the value of the previous_handle argument to the next call to FooDataReader::read_next_instance. The iteration continues until FooDataReader::read_next_instance fails with the value DDS_RETCODE_NO_DATA.

Note that it is possible to call the FooDataReader::read_next_instance operation with a previous_handle that does not correspond to an instance currently managed by the DDSDataReader. This is because as stated earlier the 'greater-than' relationship is defined even for handles not managed by the DDSDataReader. One practical situation where this may occur is when an application is iterating though all the instances, takes all the samples of a DDS_NOT_ALIVE_NO_WRITERS_INSTANCE_STATE instance, returns the loan (at which point the instance information may be removed, and thus the handle becomes invalid), and tries to read the next instance.

The behavior of the FooDataReader::read_next_instance operation follows the same rules as the FooDataReader::read operation regarding the pre-conditions and post-conditions for the received_data and sample_info. Similar to the FooDataReader::read, the FooDataReader::read_instance operation may 'loan' elements to the output collections, which must then be returned by means of FooDataReader::return_loan.

Similar to the FooDataReader::read, this operation must be provided on the specialized class that is generated for the particular application data-type that is being taken.

If the DDSDataReader has no samples that meet the constraints, the method will fail with DDS_RETCODE_NO_DATA.

Parameters:
received_data <<inout>> user data type-specific FooSeq object where the received data samples will be returned.
info_seq <<inout>> a DDS_SampleInfoSeq object where the received sample info will be returned.
max_samples <<in>> The maximum number of samples to be returned. If the special value DDS_LENGTH_UNLIMITED is provided, as many samples will be returned as are available, up to the limits described in the documentation for FooDataReader::take().
previous_handle <<in>> The 'next smallest' instance with a value greater than this value that has available samples will be returned.
sample_states <<in>> data samples matching ones of these sample_states are returned
view_states <<in>> data samples matching ones of these view_state are returned
instance_states <<in>> data samples matching ones of these instance_state are returned
Returns:
One of the Standard Return Codes, DDS_RETCODE_PRECONDITION_NOT_MET DDS_RETCODE_NO_DATA or DDS_RETCODE_NOT_ENABLED.
See also:
FooDataReader::read

DDS_LENGTH_UNLIMITED

virtual DDS_ReturnCode_t FooDataReader::take_next_instance ( FooSeq &  received_data,
DDS_SampleInfoSeq &  info_seq,
DDS_Long  max_samples,
const DDS_InstanceHandle_t &  previous_handle,
DDS_SampleStateMask  sample_states,
DDS_ViewStateMask  view_states,
DDS_InstanceStateMask  instance_states 
) [pure virtual]

Access a collection of data samples from the DDSDataReader.

This operation accesses a collection of data values from the DDSDataReader and 'removes' them from the DDSDataReader.

This operation has the same behavior as FooDataReader::read_next_instance, except that the samples are 'taken' from the DDSDataReader such that they are no longer accessible via subsequent 'read' or 'take' operations.

Similar to the operation FooDataReader::read_next_instance, it is possible to call FooDataReader::take_next_instance with a previous_handle that does not correspond to an instance currently managed by the DDSDataReader.

The behavior of the FooDataReader::take_next_instance operation follows the same rules as the FooDataReader::read operation regarding the pre-conditions and post-conditions for the received_data and sample_info. Similar to the FooDataReader::read, the FooDataReader::take_next_instance operation may 'loan' elements to the output collections, which must then be returned by means of FooDataReader::return_loan.

Similar to the FooDataReader::read, this operation must be provided on the specialized class that is generated for the particular application data-type that is being taken.

If the DDSDataReader has no samples that meet the constraints, the method will fail with DDS_RETCODE_NO_DATA.

Parameters:
received_data <<inout>> user data type-specific FooSeq object where the received data samples will be returned.
info_seq <<inout>> a DDS_SampleInfoSeq object where the received sample info will be returned.
max_samples <<in>> The maximum number of samples to be returned. If the special value DDS_LENGTH_UNLIMITED is provided, as many samples will be returned as are available, up to the limits described in the documentation for FooDataReader::take().
previous_handle <<in>> The 'next smallest' instance with a value greater than this value that has available samples will be returned.
sample_states <<in>> data samples matching ones of these sample_states are returned
view_states <<in>> data samples matching ones of these view_state are returned
instance_states <<in>> data samples matching ones of these instance_state are returned
Returns:
One of the Standard Return Codes, DDS_RETCODE_PRECONDITION_NOT_MET, DDS_RETCODE_NO_DATA or DDS_RETCODE_NOT_ENABLED.
See also:
FooDataReader::take

DDS_LENGTH_UNLIMITED

virtual DDS_ReturnCode_t FooDataReader::read_next_instance_w_condition ( FooSeq &  received_data,
DDS_SampleInfoSeq &  info_seq,
DDS_Long  max_samples,
const DDS_InstanceHandle_t &  previous_handle,
DDSReadCondition *  condition 
) [pure virtual]

Accesses via FooDataReader::read_next_instance the samples that match the criteria specified in the DDSReadCondition.

This operation accesses a collection of data values from the DDSDataReader. The behavior is identical to FooDataReader::read_next_instance, except that all returned samples satisfy the specified condition. In other words, on success, all returned samples belong to the same instance, and the instance is the instance with 'smallest' instance_handle among the ones that verify: (a) instance_handle >= previous_handle, and (b) have samples for which the specified DDSReadCondition evaluates to TRUE.

Similar to the operation FooDataReader::read_next_instance, it is possible to call FooDataReader::read_next_instance_w_condition with a previous_handle that does not correspond to an instance currently managed by the DDSDataReader.

The behavior of the FooDataReader::read_next_instance_w_condition operation follows the same rules as the FooDataReader::read operation regarding the pre-conditions and post-conditions for the received_data and sample_info. Similar to the FooDataReader::read, the FooDataReader::read_next_instance_w_condition operation may 'loan' elements to the output collections, which must then be returned by means of FooDataReader::return_loan.

Similar to the FooDataReader::read, this operation must be provided on the specialized class that is generated for the particular application data-type that is being taken.

If the DDSDataReader has no samples that meet the constraints, the method will fail with DDS_RETCODE_NO_DATA.

Parameters:
received_data <<inout>> user data type-specific FooSeq object where the received data samples will be returned.
info_seq <<inout>> a DDS_SampleInfoSeq object where the received sample info will be returned.
max_samples <<in>> The maximum number of samples to be returned. If the special value DDS_LENGTH_UNLIMITED is provided, as many samples will be returned as are available, up to the limits described in the documentation for FooDataReader::take().
previous_handle <<in>> The 'next smallest' instance with a value greater than this value that has available samples will be returned.
condition <<in>> the DDSReadCondition to select samples of interest. Cannot be NULL.
Returns:
One of the Standard Return Codes, DDS_RETCODE_PRECONDITION_NOT_MET DDS_RETCODE_NO_DATA or DDS_RETCODE_NOT_ENABLED.
See also:
FooDataReader::read_next_instance

DDS_LENGTH_UNLIMITED

virtual DDS_ReturnCode_t FooDataReader::take_next_instance_w_condition ( FooSeq &  received_data,
DDS_SampleInfoSeq &  info_seq,
DDS_Long  max_samples,
const DDS_InstanceHandle_t &  previous_handle,
DDSReadCondition *  condition 
) [pure virtual]

Accesses via FooDataReader::take_next_instance the samples that match the criteria specified in the DDSReadCondition.

This operation accesses a collection of data values from the DDSDataReader and 'removes' them from the DDSDataReader.

The operation has the same behavior as FooDataReader::read_next_instance_w_condition, except that the samples are 'taken' from the DDSDataReader such that they are no longer accessible via subsequent 'read' or 'take' operations.

Similar to the operation FooDataReader::read_next_instance, it is possible to call FooDataReader::take_next_instance_w_condition with a previous_handle that does not correspond to an instance currently managed by the DDSDataReader.

The behavior of the FooDataReader::take_next_instance_w_condition operation follows the same rules as the FooDataReader::read operation regarding the pre-conditions and post-conditions for the received_data and sample_info. Similar to FooDataReader::read, the FooDataReader::take_next_instance_w_condition operation may 'loan' elements to the output collections, which must then be returned by means of FooDataReader::return_loan.

Similar to the FooDataReader::read, this operation must be provided on the specialized class that is generated for the particular application data-type that is being taken.

If the DDSDataReader has no samples that meet the constraints, the method will fail with DDS_RETCODE_NO_DATA.

Parameters:
received_data <<inout>> user data type-specific FooSeq object where the received data samples will be returned.
info_seq <<inout>> a DDS_SampleInfoSeq object where the received sample info will be returned.
max_samples <<in>> The maximum number of samples to be returned. If the special value DDS_LENGTH_UNLIMITED is provided, as many samples will be returned as are available, up to the limits described in the documentation for FooDataReader::take().
previous_handle <<in>> The 'next smallest' instance with a value greater than this value that has available samples will be returned.
condition <<in>> the DDSReadCondition to select samples of interest. Cannot be NULL.
Returns:
One of the Standard Return Codes, DDS_RETCODE_PRECONDITION_NOT_MET, or DDS_RETCODE_NO_DATA, DDS_RETCODE_NOT_ENABLED.
See also:
FooDataReader::take_next_instance

DDS_LENGTH_UNLIMITED

virtual DDS_ReturnCode_t FooDataReader::return_loan ( FooSeq &  received_data,
DDS_SampleInfoSeq &  info_seq 
) [pure virtual]

Indicates to the DDSDataReader that the application is done accessing the collection of received_data and info_seq obtained by some earlier invocation of read or take on the DDSDataReader.

This operation indicates to the DDSDataReader that the application is done accessing the collection of received_data and info_seq obtained by some earlier invocation of read or take on the DDSDataReader.

The received_data and info_seq must belong to a single related "pair"; that is, they should correspond to a pair returned from a single call to read or take. The received_data and info_seq must also have been obtained from the same DDSDataReader to which they are returned. If either of these conditions is not met, the operation will fail with DDS_RETCODE_PRECONDITION_NOT_MET.

The operation FooDataReader::return_loan allows implementations of the read and take operations to "loan" buffers from the DDSDataReader to the application and in this manner provide "zerocopy" access to the data. During the loan, the DDSDataReader will guarantee that the data and sample-information are not modified.

It is not necessary for an application to return the loans immediately after the read or take calls. However, as these buffers correspond to internal resources inside the DDSDataReader, the application should not retain them indefinitely.

The use of FooDataReader::return_loan is only necessary if the read or take calls "loaned" buffers to the application. This only occurs if the received_data and info_Seq collections had max_len=0 at the time read or take was called.

The application may also examine the "owns" property of the collection to determine where there is an outstanding loan. However, calling FooDataReader::return_loan on a collection that does not have a loan is safe and has no side effects.

If the collections had a loan, upon completion of FooDataReader::return_loan, the collections will have max_len=0.

Similar to read, this operation must be provided on the specialized class that is generated for the particular application data-type that is being taken.

Parameters:
received_data <<in>> user data type-specific FooSeq object where the received data samples was obtained from earlier invocation of read or take on the DDSDataReader.

Parameters:
info_seq <<in>> a DDS_SampleInfoSeq object where the received sample info was obtained from earlier invocation of read or take on the DDSDataReader.
Returns:
One of the Standard Return Codes, DDS_RETCODE_PRECONDITION_NOT_MET or DDS_RETCODE_NOT_ENABLED.

virtual DDS_ReturnCode_t FooDataReader::get_key_value ( Foo &  key_holder,
const DDS_InstanceHandle_t  handle 
) [pure virtual]

Retrieve the instance key that corresponds to an instance handle.

Useful for keyed data types.

The operation will only fill the fields that form the key inside the key_holder instance.

For keyed data types, this operation may fail with DDS_RETCODE_BAD_PARAMETER if the handle does not correspond to an existing data-object known to the DDSDataReader.

Parameters:
key_holder <<inout>> a user data type specific key holder, whose key fields are filled by this operation. If Foo has no key, this method has no effect.
handle <<in>> the instance whose key is to be retrieved. If Foo has a key, handle must represent an existing instance of type Foo known to the DDSDataReader. Otherwise, this method will fail with DDS_RETCODE_BAD_PARAMETER. If Foo has a key and handle is DDS_HANDLE_NIL, this method will fail with DDS_RETCODE_BAD_PARAMETER. If Foo has a key and handle represents an instance of another type or an instance of type Foo that has been unregistered, this method will fail with DDS_RETCODE_BAD_PARAMETER. If Foo has no key, this method has no effect.
Returns:
One of the Standard Return Codes or DDS_RETCODE_NOT_ENABLED.
See also:
FooDataWriter::get_key_value

virtual DDS_InstanceHandle_t FooDataReader::lookup_instance ( const Foo &  key_holder  )  [pure virtual]

Retrieves the instance handle that corresponds to an instance key_holder.

Useful for keyed data types.

This operation takes as a parameter an instance and returns a handle that can be used in subsequent operations that accept an instance handle as an argument. The instance parameter is only used for the purpose of examining the fields that define the key. This operation does not register the instance in question. If the instance has not been previously registered, or if for any other reason the Service is unable to provide an instance handle, the Service will return the special value HANDLE_NIL.

Parameters:
key_holder <<in>> a user data type specific key holder.
Returns:
the instance handle associated with this instance. If Foo has no key, this method has no effect and returns DDS_HANDLE_NIL

RTI Connext C++ API Version 4.5f Copyright © 17 Mar 2012 Real-Time Innovations, Inc