IO traits in v0.3

[Darksonn]

I am opening this issue to have a place to keep track of our plans for the AsyncRead/AsyncWrite traits in v0.3. Some questions to address:

• What to do about vectored IO?
• What to do about io_uring?
• What to do about the traits from the futures crate?

Related dicussions:

• Refactor AsyncBufRead Possibly refactor AsyncBufRead #2428
• Technical notes regarding io_uring io_uring #2411

Old discussions: #1271, #1272, #1297, #1551

[carllerche]

I believe the questions that must be answered by 0.3 have been.

• vectored I/O has been removed from traits and will be added back to structs at some point in the future.
• io_uring -> punt until after 1.0
• I/O traits in the futures crate -> not implement. We are only depending on traits in std.

[carllerche]

• vectored writes has been brought back, vectored reads can be done in a forwards-compatible way.
• io_uring` support will be added in a forwards-compatible way.
• std will not include async I/O traits.

We can close this I think.

[kaimast]

vectored writes has been brought back, vectored reads can be done in a forwards-compatible way.

Where is this now? I cannot find a write_vectored or write_all_vectored in the AsyncWriteExt.

[Darksonn]

We have poll_write_vectored on AsyncWrite, but there's currently no helper for it on the extension trait.

[0x5459]

vectored writes has been brought back, vectored reads can be done in a forwards-compatible way.

Please forgive my ignorance, I don't know how to vectored reads in a forwards-compatible way.

std read_vectored + tokio::task::spawn_blocking?

[Darksonn]

By "forwards-compatible" I mean that it can be added to Tokio in the future.

Tokio doesn't come with helpers for it, but async_io can be used to execute any custom IO operation.