Compio IO crate

[George-Miao]

This PR adds compio-io and async Read/Write counterpart traits like those in tokio, futures and monoio.

• The traits
• Extension traits
• Buf{Reader/Writer}
• Util functions
• Tests

[George-Miao]

Should we use RPITIT/AFIT as they're stablizing? Or stick with GAT and adopt later? @Berrysoft

[Berrysoft]

Do you know how long does it take to stablize?

[George-Miao]

Do you know how long does it take to stablize?

I just checked, there's some concerns during FCP, but I do expect them to be resolved soon, maybe in one or two weeks.

[Berrysoft]

I prefer to use them after they're stablized.

[George-Miao]

I prefer to use them after they're stablized.

Then I'll use assoc type for now.

[Berrysoft]

I changed my mind. I think we can just use AFIT, and wait for the rust team to stabilize it.

[George-Miao]

I changed my mind. I think we can just use AFIT, and wait for the rust team to stabilize it.

I'm thinking if we need to support dyn by adding separate trait returning boxed future instead of generated anonymous future. Dyn traits can depend on non-dyn version, makes it effectively free for trait implementor. Here's an example.

[Berrysoft]

Is such trait object safe?

[George-Miao]

Is such trait object safe?

Yes. The main reason why AFIT/RPITIT cannot be made into dyn object is because of its anonymous assoc type, which cannot be specified. I'm using box dyn to erase that type here.

[George-Miao]

@Berrysoft how do you like the traits?

BTW is it possible to stop the CI for this specific PR during drafting? I'm using nightly but the CI isn't happy about that.

[George-Miao]

A side note: because compio is a thread-per-core runtime, we can safely disregard the lint comes with AFIT. We just need to remove it in some future version of rust.

[Berrysoft]

LGTM.

[George-Miao]

Ok I forgot one important thing. Methods in AsyncReadDyn and AsyncWriteDyn are parameterized, meaning they're not object safe. We have to give up on the dyn traits.

[Berrysoft]

I think we also need read_to_end and read_to_string.