Stream::read: partial read OR returning the expected size of the buffer

[melekes]

The problem I'm facing right now is where I'm passing a buffer to Stream::read, which is not big enough (Error::ErrShortBuffer). Note there's no indication of the expected size => you're forced to guess the number.

Also note it's different from TcpStream https://doc.rust-lang.org/std/io/trait.Read.html#tymethod.read, which partially reads the data and does not put any restrictions on the size of the buffer (i.e. you, the caller, is in control of how fast you're consuming data).

I can see that the code in Pion is identical to one here, but I nonetheless think we need to change something.

Either

1. switch to "tcp stream" partial reading model
2. indicate the expected buffer size by changing ErrShortBuffer to be ErrShortBuffer { min: usize }

Comments and suggestions are welcome.

[melekes]

There's also talk about auto-tuning buffer size, which is slightly related pion/sctp#218 (comment)

[melekes]

sctp/src/queue/reassembly_queue.rs

Line 282 in ed21dae

self.subtract_num_bytes(to_copy);

also, why are we subtracting n_bytes before we've actually successfully written them to client's buffer?

[algesten]

I prefer 1. Make it as Rust-y as possible. If we for some reason need to have an in between transition period, we can do 2.

[k0nserv]

I agree with @algesten, matching other Rust APIs, especially from the standard lib is good idea I think

[k0nserv]

We have migrated this crate to the monorepo(webrtc-rs/webrtc) please re-open this issue over there.