tokio_util: Convert MyStream<T> into MyAsync<Bytes>

[ph633x]

Hello dear tokio friends!

First of all, thanks for this amazing project.

My scenario might seem a little weird, for which I apologize and am open for suggestions:

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I have Decoder for some type T> However, in my decoder, I don't consume the stream. Instead, I just look at the first Bytes, parse them into a type T, and keep the bytes there "untouched" by not 'splitting` them.

In the usage side, I get a TcpStream, frame it with FramedRead and my Decoder, make a decision based on the value of type T, and then convert the FramedRead back into a TcpStream with into_inner. My return type must be something that implements AsyncRead and AsyncWrite, not necessarily the actual input TcpStream.

The problem is that, into_inner discards the bytes I had already "read", which are available via get_read_buf.

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I thought about creating a new type wrapping the TcpStream and the Bytes in get_read_buf and implement AsyncRead for it. Upon reading, first takes the leftover bytes, and then read from the inner TcpStream.

But I am not sure if that's the best way nor how to best implement such a solution.

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Would you happen to know the best way to solve this?

Thank you very much.
Leo.

[Darksonn]

You could put the Bytes object into a Cursor and combine it with the tcp stream using AsyncReadExt::chain.

[ph633x]

True! That's great idea. Thanks for pointing that out.

On top that:

Would this non-consuming decoder be idiomatic usage of tokio_util?

[Darksonn]

If you're only going to read a single element in this way, it would make more sense to do it yourself with the ordinary read methods.

[ph633x]

Pretty much. Actually, I need to read (or peek) the first n elements.

But indeed, maybe read_exact and then chain with TCP stream via Cursor.

I like it :).

Thanks.