No obvious way to set a read limit for read_until

[Wesmania]

In standard library, it's possible to call BufRead's read_until with a read limit using a pattern like this:

reader.by_ref().take(limit).read_until(byte, buf)

The by_ref() call allows us to reuse the reader later. The same pattern works in async_std, as its ReadExt trait implements by_ref:

reader.by_ref().take(limit).read_until(byte, buf).await

Tokio only implements by_ref for *Half traits, which means the above one-liner doesn't work after wrappeng them in a BufReader. I don't see any other way of imposing a read limit on read_until in Tokio other than reimplementing it.

I suppose the simplest (end-user wise) way to fix this would be to implement by_ref in AsyncReadExt for any AsyncRead. I have no idea how hard it is, #2716 mentions some trouble implementing by_ref for TcpStream.

[Darksonn]

Note that reader.by_ref() is equivalent to (&mut reader), so you should be able to do this:

(&mut reader).take(limit).read_until(byte, buf).await

The TcpStream::by_ref discussion is unrelated. Adding it would be very easy.

[Wesmania]

It works for me, thanks. I suppose by_ref is just there for chaining.