Non-functional requirements

[JojoEffect]

• C++ 11 standard
• Use PROTOBUF and proto definitions (be aware of newer features)
• Minimal 3rd party libs versions:
  • Protobuf v3.19 in DEV
• Configurable functions
  • buffer/memory size on init
  • Validation of given data fields/sets
  • Storage of linked raw data (should the library be responsible for the availability of the linked raw data inside the provided data sets?)
• separate handling of reads and writes on the lib
  • write should be able to run in real-time context
    • real time mutex - ceiling priority, priority inheritance
      • int initRTMutex(pthread_mutex_t *mutex) { pthread_mutexattr_t mutexAttr; pthread_mutexattr_init(&mutexAttr); pthread_mutexattr_setpshared(&mutexAttr, PTHREAD_PROCESS_SHARED); pthread_mutexattr_setrobust_np(&mutexAttr, PTHREAD_MUTEX_ROBUST_NP); pthread_mutexattr_setprotocol(&mutexAttr, PTHREAD_PRIO_INHERIT); pthread_mutex_init(mutex, &mutexAttr); }
    • avoid memory alloc on write
  • read should run in NON-real-time
• Deployment
  • Sources
  • Conan package
  • Microservices
    • with VLP API
    • optional with gRPC API
    • optional with OPC UA API

[dschnabel]

Protobuf offers these functionalities:

1. Generate language-dependent structures and headers from proto definitions which can be incorporated into user code (e.g. C++, C#, Python, Node.js, ...)
2. Serialize structures for storage or network transfer

Different versions of protobuf may generate slightly different structures even if the same proto definition file is used. This has implications if these structures are shared between applications (e.g. using gRPC).

Also, best practice requires that generated protobuf structures and headers are not being checked into source control, only the proto definition files. This means that every time somebody wants to compile and run the user code, protobuf needs to re-generate the structures and headers, if they are not yet present. As a result, the protobuf compiler (protoc) becomes a compile time requirement because without the generated files, the user code will not compile. Problems can occur, if the user code was implemented against an API generated by a different version of protoc. For this reason, protobuf checks the variable PROTOBUF_VERSION and prints these errors:

• This file was generated by a newer version of protoc which is incompatible with your Protocol Buffer headers. Please update your headers.
• This file was generated by an older version of protoc which is incompatible with your Protocol Buffer headers. Please regenerate this file with a newer version of protoc.

In general, protobuf tries to keep API compatibility between versions, so a tight version match is not needed. However, it is still recommended to use similar protobuf versions for code generation.

For this reason, I think we need to agree on a protobuf version to use in this project.

[dschnabel]

C++ 11 standard

The library makes use of these C++17 features:

• std::variant (see here),
• std::visit (see here),
• std::string_view (see here)

These will have to be re-written to work with C++11.