Unseal Buffer trait

[morbridge]

Hi!

I find Buffer trait and SpareCapacity quite nice. But having the trait sealed is quite limiting.

Any plans to unseal the the trait so it can be used for own buffer types and own read-like methods? Are the internals too unstable? Would this have any memory safety issues?

I think tokio, bytes, async-std could use this technique too (although, I'm not sure if it's okay for them to depend on rustix)

[sunfishcode]

I've been experimenting with the Buffer trait in a standalone buffer-trait crate, which has an unsealed trait and a more complete API.

Crates like bytes probably won't ever want a dependency on rustix, so buffer-trait is the more likely path forward here. If buffer-trait becomes popular, perhaps rustix should switch to it too.

Also, there has been some interest in the Buffer trait from some Rust folks, as a possible alternative to BorrowedBuf, though there isn't yet an RFC.