class <DataElement-Namespace>::<DataElementInterface>

The interface serves Adaptive Applications to provide diagnostic data for read accesses by Diagnostic Management. After instantiation via an instance specifier, the application must actively offer the service so that incoming read requests can be received [SWS_DM_00597]. Incoming requests are processed via the asynchronous read method, which provides the requested output data or negative response codes in a future value [SWS_DM_00596]. Because copy and move operations are deleted, each instance is permanently bound to its context.

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Context

The generated C++ class <DataElementInterface> acts within the functional cluster diag (AUTOSAR Adaptive Platform) as a standardized server interface for providing readable diagnostic data AUTOSAR_AP_SWS_Diagnostics p. 68. Specifically, it maps a DiagnosticDataElementInterface in the role read, via which an Adaptive Application transmits data values for diagnostic requests (such as UDS ReadDataByIdentifier) to the Diagnostic Manager (DM) [SWS_DM_00596].

Essential interaction partners are the Diagnostic Management of the platform daemon, which coordinates incoming diagnostic requests, and the implementing Adaptive Application, which inherits from this interface and implements the provision logic. Instantiation and assignment to the software architecture are performed via a modeled port prototype that is connected via an ara::core::InstanceSpecifier [SWS_DM_00587]. The output data is encapsulated in a type-specific structure whose arguments are represented by corresponding output elements [SWS_DM_80023], [SWS_DM_00581].

Lifecycle

An instance is created via the constructor by specifying the ara::core::InstanceSpecifier and the concurrency mode ara::diag::ConcurrencyType [SWS_DM_00587]. To maintain unique mapping within the process, both the copy constructor and the move constructor are deleted [SWS_DM_01661], [SWS_DM_01662]. Likewise, the copy and move assignment operators are explicitly deleted [SWS_DM_01659], [SWS_DM_01660]. An instance thus remains fixed at its created address.

Regarding operation, the object undergoes defined phases:

• Not Offered: After construction, the object is initially in an inactive state in which the DM does not deliver read requests.
• Offered: Calling Offer() activates the service with the DM so that incoming read requests are forwarded [SWS_DM_00597].
• Deregistered: Calling StopOffer() deactivates the forwarding of future diagnostic requests by the DM [SWS_DM_00617].
• Destruction: The virtual destructor ~<DataElementInterface>() terminates the lifecycle of the interface instance [SWS_DM_00588].

While the constructor is specified as thread-safe [SWS_DM_00587], Offer(), StopOffer(), Read(), and the destructor are not thread-safe [SWS_DM_00597], [SWS_DM_00617], [SWS_DM_00596], [SWS_DM_00588]. The parameter concurrencyType in the constructor determines whether the handler implementation is implemented thread-safe (kConcurrent) or not thread-safe (kNotConcurrent) [SWS_DM_00587].

State diagram: State phases of an interface instance between initialization, publication state, and destruction. Sources: [SWS_DM_00587], [SWS_DM_00597], [SWS_DM_00617], [SWS_DM_00588].

Usage Path

The regular flow for data retrieval follows a fixed sequence of steps:

1. Instantiation: The application instantiates the derived handler class with the desired instanceSpec and concurrencyType [SWS_DM_00587].
2. Service release: The application calls Offer(), enabling the DM to forward read requests [SWS_DM_00597].
3. Processing of read requests: When a read request arrives at the DM, it calls the pure virtual method Read(metaInfo, cancellationHandler) on the handler [SWS_DM_00596]. The application evaluates metaInfo and can check via cancellationHandler.IsCanceled() whether the conversation was canceled, or register a callback via cancellationHandler.SetNotifier [SWS_DM_00596].
4. Feedback: Interpretation: The actual determination of the output data is typically expected to occur asynchronously; the result is provided in an ara::core::Future with the corresponding ReadOutput object [SWS_DM_00596], [SWS_DM_00581]. Question Q-ce317bd1275e4fd9 (open)
5. Service termination: Prior to shutdown, the application calls StopOffer() to prevent forwarding [SWS_DM_00617], followed by object destruction [SWS_DM_00588].

Sequence diagram: Call sequence from service registration through asynchronous reading to deregistration. Sources: [SWS_DM_00597], [SWS_DM_00596], [SWS_DM_00617].

Error Scenarios

In case of error, the different lifecycle phases must be considered separately:

Integrity violations can occur as early as construction, signaled via specific violations [SWS_DM_00587]:

• InstanceSpecifierMappingIntegrityViolation: The instance specifier cannot be resolved in the model of the executable or does not reference an PortPrototype.
• PortInterfaceMappingViolation: A PortPrototype typed by the DiagnosticDataElementInterface is not referenced by an DiagnosticDataPortMapping.
• ProcessMappingViolation: A matching InstanceRef exists, but no matching modeled process corresponding to the runtime process was found.
• InstanceSpecifierAlreadyInUseViolation: The constructor was called with an InstanceSpecifier that is already in use in the current process.

If Offer() is called for an already offered service, the method returns an ara::core::Result with the error code DiagOfferErrc::kAlreadyOffered (rollback semantics) [SWS_DM_00597].

If a read request cannot be answered successfully in Read(), the returned ara::core::Future must contain a corresponding ISO 14229-1 Negative Response Code (NRC) via DiagUdsNrcErrc or an ApApplicationError [SWS_DM_00596].