AUTOSAR Adaptive Platform R20-11：ARAComAPI详解

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AUTOSAR EXP ARAComAPI.pdf 是一个关于AUTOSAR (AUTomotive Open System Architecture) 的关键文档，特别关注的是ARA (Adaptive Radio Access) Com API (Application Programming Interface) 的详细解释。AUTOSAR 是一个全球性的汽车行业软件平台标准，旨在促进车辆电子系统的标准化和互操作性。 ARAComAPI是该标准的一部分，针对智能驾驶车辆中的无线通信功能，它定义了接口和方法来处理适应性无线接入，如蜂窝网络连接。此文档的重要性在于它为开发者提供了关于如何利用ARAComAPI进行高效、安全的车载通信的指导，包括： 1. **术语澄清**：文档在多个版本中更新了术语，例如将"(Un)Checked Exception"替换为更明确的表述，确保开发者理解异常处理的最佳实践。 2. **实例说明**：对于InstanceSpecifier（实例标识符），文档提供了详细的使用和转移规则，这对于正确配置和管理不同的系统组件至关重要。 3. **访问权限**：在R19-11版本中，增加了从Get和SetHandler获取当前字段值的功能，增强了API的灵活性和功能性。 4. **事件处理**：文档在2019年调整了对事件接收的解释，可能反映了ARAComAPI在实时通信中的新行为或优化。 5. **接口结构与样本代码**：版本18-10引入了实例标识符的概念，并重新组织了章节结构，以便于用户理解和使用。此外，添加了示例代码，用于展示如何通过ARAComAPI正确地发送和接收事件，以及创建和使用代理和骨架。 6. **参考指南**：文档曾提及"AUTOSAR_RS_CPP14Guidelines"，但未给出具体说明，这可能是之前的编程指南或编码规范，说明文档可能还需配合其他规范来实现最佳实践。这份文档是智能驾驶车辆开发人员必备的技术参考资料，它帮助开发者遵循AUTOSAR标准，实现高效、稳定且兼容的车载通信功能，以支持自动驾驶和车联网技术的发展。

Explanation of ara::com API

AUTOSAR AP R20-11

Being able to provide their own implementations allows to optimize for their chosen

memory model.

For most of the types ara::com provides a default mapping to existing C++ types

in ara/com/types.h. This default mapping decision could be reused by an AP product

vendor.

The default mapping provided by ara::com even has a real benefit for a product

vendor, who wants to implement its own variant: He can validate the functional behavior

of his own implementation against the implementation of the default mapping.

5.4 Error Notification

ara::com API follows the concepts of error handling described in chapter "Error han-

dling" in [4]. Checked Errors will be returned via ara::core::ErrorCode directly

or an ara::core::ErrorCode embedded into a ara::core::Result, which ei-

ther holds a valid return value or the ara::core::ErrorCode.

The functionality provided with ara::core::Result and ara::core::Future (de-

tails, see subsubsection 6.2.4.2) allow the user of ara::com to chose between excep-

tion based or return code based error handling to some degree.

5.4.1 Checked Errors/Exceptions

Checked Errors within ara::com API can only occur in the context of a call of

a service interface method and is therefore fully covered in subsection 6.2.4 and

subsection 6.3.4.

5.4.2 Unchecked Errors/Exceptions

Unchecked Errors within ara::com API can occur in the context of any ara::com

API call.

The ara::com API does not throw any Execption. The only way to have exceptions

is calling the get method of ara::core::Future, if the user decides to use this

approach.

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Explanation of ara::com API

AUTOSAR AP R20-11

The method “LogCurrentState” is a one way method, which means, that no feedback

is returned to the caller, if the method is executed at all and with which outcome. It

instructs the service RadarService to output its current state into its local log files.

6.1 Instance Identifiers

Instance identifiers, which get used at proxy and as well at skeleton side, are such a

central concept, that their explanation is drawn here — before the detailed description

of ara::com proxies and skeletons in upcoming chapters.

Instance identifiers are used within ara::com, on client/proxy side, when a specific

instance of a service shall be searched for or — at the server/skeleton side — when a

specific instance of a service is created.

At ara::com API level the instance identifier is generally a technical binding specific

identifier.

Therefore the concrete content/structure of which such an instance identifier consists,

is totally technology specific: So f.i. SOME/IP is using 16 bit unsigned integer identifiers

to distinguish different instances of the same service type, while DDS (DDS-RPC) uses

string<256> as service_instance_name.

Independant of the binding technology the abstract facade of any concrete instance

identifier shall apply to this signature at ara::com API level in namespace ara::-

com:

1 class InstanceIdentifier {

2 public:

4 explicit InstanceIdentifier(const ara::core:string_view value);

5 const ara::core:string_view toString() const;

6 bool operator==(const InstanceIdentifier& other) const;

7 bool operator<(const InstanceIdentifier& other) const;

8 InstanceIdentifier& operator=(const InstanceIdentifier& other);

9 };

Listing 6.2: InstanceIdentifier class

As you can see the instance identifier interface ara::com::InstanceIdentifier

provides a ctor taking a string, which means it can be constructed from a string rep-

resentation and it does provide a toString() method, which allows to get a stringified

representation of the technology specific ara::com::InstanceIdentifier.

This pair of ctor taking a string representation and the possibility to write out the

string representation makes the ara::com::InstanceIdentifier "serializable".

This allows it to be transferred, persisted, later re-used, ... (more on potential use

cases later).

Introspection into this string (trying to interpret the content) makes no sense for the user

of ara::com. As mentioned: The content will be highly middleware product/binding

specific!

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Explanation of ara::com API

AUTOSAR AP R20-11

Since it is a core feature, that the technical binding used by an ara::com based appli-

cation is defined/specified by the integrator during deployment any expectations from

an ara::com software developer regarding its content/structure are typically invalid.

Logging it/tracing it out to a log channel might be helpful for debug analysis however.

Then, where does the software-developer get such a highly binding specific ara::-

com::InstanceIdentifier to be used in ara::com API calls?

The answer is: By an ara:com provided functionality, which translates a logical local

name used typically by the software developer in his realm into the technology/bind-

ing specific ara::com::InstanceIdentifier. This indirection masters both chal-

lenges:

• developer using ara::com does not need to know anything about bindings and

their specifics

• Integrators can adapt bindings in deployments

The local name from which the ara::com::InstanceIdentifier is constructed

comes basically from AUTOSAR meta-model, describing your software component

model.

The requirement for this local name — we will call it "instance specifier" from now on

— is, that it is unambiguous within an executable. It has basically the form:

The C++ representation of such an "instance specifier" is the class ara::core::In-

stanceSpecifier. Structurally it looks similar to the ara::com::InstanceIden-

tifier:

1 class InstanceSpecifier {

2 public:

3 // ctor to build specifier from AUTOSAR short name identifier

4 // with ’/’ as separator between package names

5 explicit InstanceSpecifier(const ara::core:string_view value);

6 const ara::core:string_view toString() const;

7 bool operator==(const InstanceSpecifier& other) const;

8 bool operator<(const InstanceSpecifier& other) const;

9 InstanceSpecifier& operator=(const InstanceSpecifier& other);

10 };

Listing 6.3: InstanceSpecifier class

If the unambiguousness is ensured, the integrator/deployer can assign a dedicated

technical binding with its specific instance IDs to those "instance specifier" via a "man-

ifest file", which is specifically used for a distinct instantiation/execution of the exe-

cutable.

This explicitly allows, to start the same executable N times, each time with a different

manifest, which maps the same ara::core::InstanceSpecifier differently.

Details about the ara::com relation to the meta-model and the nature of nested con-

texts can be read more detailed in section 9.4.

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