[async] Help with implementing `future::Stream::poll_next` with multiple child streams

help
1

I've got an type with the following structure

struct MultiStream {
    s1: Receiver<()>,
    s2: Receiver<()>,
    // .. more receivers
}

To impl Stream for this type I need to implement poll_next. At the moment my strategy is to poll all streams, and if there are multiple successes, storing those temporarily so I can return Poll::Ready(Item) without doing any work on future iterations.

What I would love is something like select! but that worked on Poll rather than on futures.

Does anyone have any general advice?

2

It sounds like you're trying to reimplement SelectAll.

3

Urgh knew it would exist somewhere, thanks!

EDIT Hmm my use case is actually more complicated than the example I gave: I have a mixture of different types which return different Items, and some of my stream are actually futures (specifically a future that indicates a connection is closed, so there will be no more events on any of my streams). I think I'm going to have to roll something custom.

4

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