FreeBSD nix::sys::event::Kqueue access to inner type

[eesekaj]

An important functionality is missing in 0.27 for Kqueue.

1. "field 0 of Kqueue is private"
   There is no way it is possible to close the fd of the kqueue (OwnedFd should do it but in some cases it a raw fd is needed). as_raw_fd() is needed.
2. An access to the inner type (a raw fd) is needed otherwise it breaks functionality of programs which depends on this functionality. Some programs uses fd number to identify the instance when there are multiple sources.

pub struct Kqueue(OwnedFd); pub struct Epoll(pub OwnedFd);
It would be great to have the same for KQueue.

[SteveLauC]

Kinda similar to #1998

Would implementing AsFd for Kqueue solve the problem for your use case?

impl std::os::fd::AsFd for Kqueue {
    fn as_fd(&self) -> BorrowedFd<'_> {
        self.0.as_fd()
    }
}

Some programs use fd number to identify the instance when there are multiple sources.

BorrowedFd itself is not PartialEq, but we can call as_raw_fd() on it to extract the inner RawFd

---

Maybe we should also do this to Epoll, cc @JonathanWoollett-Light

[asomers]

Why is there ever a problem for close? Are you trying to close the underlying file descriptor without dropping the struct? I don't know of any good reasons to do that.

[SteveLauC]

I believe impl From<Kqueue> for OwnedFd would fix this issue, and why this? To be consistent with the std:

impl From<ChildStderr> for OwnedFd
impl From<ChildStdin> for OwnedFd
impl From<ChildStdout> for OwnedFd
impl From<File> for OwnedFd
impl From<PidFd> for OwnedFd
impl From<TcpListener> for OwnedFd

[eesekaj]

I was away for a while due to some problems.

The developers (including me) decided to stop using nix crate in our projects and use libc crate only, to avoid abstractions like libc -> nix -> own abstraction. Also taking into account that the some implementations in nix crate not what is required.

Thank you.