Provide Sink to AsyncWrite adaptor

[hutchisr]

tokio-util provides StreamReader and ReaderStream to convert a Stream to AsyncRead or AsyncRead to Stream, but there aren't corresponding tools for Sink and AsyncWrite. The codec module does appear to provide a way to go from an AsyncWrite to a Sink but nothing for going from Sink to AsyncWrite.

I've run into a situation where I want to generate an archive (which takes an AsyncWrite) and stream it somewhere else (as opposed to writing it to the filesystem), but without being able to create something like a channel with the send side being an AsyncWrite I don't see a way to do this.

[Darksonn]

This is indeed somewhat tricky to do. It's rather easy to make something that cuts the byte stream into chunks arbitrarily, but if you want more structure in the messages given to the sink, it gets tricky. The logic would be similar to an FramedRead.

[themaxdavitt]

I ran into a similar issue recently and I was able to use rw-stream-sink, although that comes with two noteworthy caveats: 1. it only accepts a type that implements both Sink and Stream and 2. you need to use the compatibility traits since it returns futures-io versions of the AsyncRead/AsyncWrite traits.

Example code (if you use their hidden Wrapper type):

RwStreamSink::new(Wrapper(read, write)).compat()

[minghuaw]

Would it be possible to define something that looks like Framed where user specifies a codec on how to split byte stream into chunks?

[Darksonn]

Yeah, that probably would not be impossible.