AIDL Server

Finally, we can create a server which exposes the service:

birthday_service/src/server.rs:

//! Birthday service.
use birthdayservice::BirthdayService;
use com_example_birthdayservice::aidl::com::example::birthdayservice::IBirthdayService::BnBirthdayService;
use com_example_birthdayservice::binder;

const SERVICE_IDENTIFIER: &str = "birthdayservice";

/// Entry point for birthday service.
fn main() {
    let birthday_service = BirthdayService;
    let birthday_service_binder = BnBirthdayService::new_binder(
        birthday_service,
        binder::BinderFeatures::default(),
    );
    binder::add_service(SERVICE_IDENTIFIER, birthday_service_binder.as_binder())
        .expect("Failed to register service");
    binder::ProcessState::join_thread_pool();
}

birthday_service/Android.bp:

rust_binary {
    name: "birthday_server",
    crate_name: "birthday_server",
    srcs: ["src/server.rs"],
    rustlibs: [
        "com.example.birthdayservice-rust",
        "libbinder_rs",
        "libbirthdayservice",
    ],
    prefer_rlib: true, // To avoid dynamic link error.
}

The process for taking a user-defined service implementation (in this case the BirthdayService type, which implements the IBirthdayService) and starting it as a Binder service has multiple steps, and may appear more complicated than students are used to if they've used Binder from C++ or another language. Explain to students why each step is necessary.

  1. Create an instance of your service type (BirthdayService).
  2. Wrap the service object in corresponding Bn* type (BnBirthdayService in this case). This type is generated by Binder and provides the common Binder functionality that would be provided by the BnBinder base class in C++. We don't have inheritance in Rust, so instead we use composition, putting our BirthdayService within the generated BnBinderService.
  3. Call add_service, giving it a service identifier and your service object (the BnBirthdayService object in the example).
  4. Call join_thread_pool to add the current thread to Binder's thread pool and start listening for connections.