[ESI] Add optional non-blocking write API to `WriteChannelPort`

[mortbopet]

[teqdruid]

Could you implement this for cosim and trace (and add tests as well)?

Also, is there a reason this should be optional?

[mortbopet]

Could you implement this for cosim and trace (and add tests as well)? Also, is there a reason this should be optional?

If we want everything to implement this, I don't think we can call it "non-blocking". Since neither cosim nor trace seems to have an analogue for a non-blocking write, we'd have to change the wording to indicate that it's a failable write... where the default implementation would just call write.

  /// A basic failable write API. Returns true if the data was written.
  virtual bool tryWrite(const MessageData &data) {
    write(data);
    return true;
  }

[teqdruid]

Could you implement this for cosim and trace (and add tests as well)? Also, is there a reason this should be optional?

If we want everything to implement this, I don't think we can call it "non-blocking". Since neither cosim nor trace seems to have an analogue for a non-blocking write, we'd have to change the wording to indicate that it's a failable write...

"failable" isn't specific enough. The only reason that this method should "fail" is if it "fails" to write or write to a buffer instantaneously and the caller should try again later (my interpretation of the term "non-blocking"). So I think 'non-blocking' is the correct verbiage here. We should, however, specify that it is not valid for a backend to always return false.

As for cosim/trace having no analog... they have no notion of backpressure, which is probably a bad thing since somewhere there's gotta be an infinitely large buffer, which is clearly not realistic. We should probably implement a cosim backpressure mechanism to indicate that the simulated hardware is backpressuring. So yeah, they don't have an analog yet.

where the default implementation would just call write.

  /// A basic failable write API. Returns true if the data was written.
  virtual bool tryWrite(const MessageData &data) {
    write(data);
    return true;
  }

write() can block, so that would be an invalid default implementation. It's fine for cosim/trace, but not as a default. Defaults shouldn't do something which is only valid for a subset of implementations. Since -- as I mentioned above -- we should implement so backpressure mechanism in the (near/midterm) future, I would just copy that implementation into both backends. For extra credit, implement a pseudorandom backpressure on the trace backend.

[teqdruid]

Thanks!