Improvement: Async Stream Receive API

[bharatGoswami8]

What

Rust COM API library offers the async receive APIs but for this user need to poll always and in that it may miss some samples to overcome that we are introducing a stream API which will provide a stream of data as soon as event trigger.

How

#349

Estimates for realization

0

Category

• Affects Detailed Design

Requirements / Architecture

• Requirements / Architecture are not affected by this change?

[bharatGoswami8]

Hi @artemsheinacn ,

But why would I implement it using an additional thread and more memory consumption if I can just keep using my implementation of streaming API which provides proper error-state detection?

I did not get second statement, do you mean you have internal implementation for streaming the data using COM-API ?

[artemsheinacn]

Yes, I do https://github.com/eclipse-score/feo/blob/242a28c5de30bee532e4d9094325a30ccabaca37/src/feo/src/signalling/direct/mw_com/mod.rs#L89
It was a temporary solution and may be unsound, but it asserts that there is no events overflow:

assert!(
                sample_container.sample_count() + self.received.borrow().len() <= self.received.borrow().capacity(),
                "must not allocate, configuration error"
            );

[bharatGoswami8]

Yes, I do https://github.com/eclipse-score/feo/blob/242a28c5de30bee532e4d9094325a30ccabaca37/src/feo/src/signalling/direct/mw_com/mod.rs#L89 It was a temporary solution and may be unsound, but it asserts that there is no events overflow:

assert!(
                sample_container.sample_count() + self.received.borrow().len() <= self.received.borrow().capacity(),
                "must not allocate, configuration error"
            );

@artemsheinacn ,
Understood, it is user specific requirement where user do not want to overwrite the value in internal container, this request we can also consider if other contributor agree, so what i feel one more bool parameter in API which ask user do you want to overwrite container when it is full or not if true then it can return a error when container is full.

fn to_stream<'a>(
        &'a self,
        max_samples: usize,
        **is_container_overwrite: bool,**
    ) -> impl Stream<Item = Result<Self::Sample<'a>>> + 'a;

[artemsheinacn]

Maybe it makes sense to define it as an enum like so:

enum OverflowStrategy {
   Replace,
   Panic,
   Resize,
   ...
}

fn to_stream<'a>(
        &'a self,
        max_samples: usize,
        container_overflow_strategy: OverflowStrategy,
    ) -> impl Stream<Item = Result<Self::Sample<'a>>> + 'a;

[bharatGoswami8]

Maybe it makes sense to define it as an enum like so:

enum OverflowStrategy {
   Replace,
   Panic,
   Resize,
   ...
}

fn to_stream<'a>(
        &'a self,
        max_samples: usize,
        container_overflow_strategy: OverflowStrategy,
    ) -> impl Stream<Item = Result<Self::Sample<'a>>> + 'a;

@artemsheinacn ,
I agree, though I’m still concerned that runtime resizing might not be the best approach. However, I’d like to see how others feel about this API extension. Could you add a comment to the PR with this suggestion so we can get more feedback?