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use std::fs::File;
use std::io::{self, Read, Write};
#[cfg(not(target_os = "hermit"))]
use std::os::fd::{AsRawFd, FromRawFd, RawFd};
// can use `std::os::fd` and be merged with the above.
#[cfg(target_os = "hermit")]
use std::os::hermit::io::{AsRawFd, FromRawFd, RawFd};
use crate::sys::unix::pipe;
use crate::sys::Selector;
use crate::{Interest, Token};
/// Waker backed by a unix pipe.
///
/// Waker controls both the sending and receiving ends and empties the pipe
/// if writing to it (waking) fails.
#[derive(Debug)]
pub(crate) struct Waker {
sender: File,
receiver: File,
}
impl Waker {
#[allow(dead_code)] // Not used by the `poll(2)` implementation.
pub(crate) fn new(selector: &Selector, token: Token) -> io::Result<Waker> {
let waker = Waker::new_unregistered()?;
selector.register(waker.receiver.as_raw_fd(), token, Interest::READABLE)?;
Ok(waker)
}
pub(crate) fn new_unregistered() -> io::Result<Waker> {
let [receiver, sender] = pipe::new_raw()?;
let sender = unsafe { File::from_raw_fd(sender) };
let receiver = unsafe { File::from_raw_fd(receiver) };
Ok(Waker { sender, receiver })
}
pub(crate) fn wake(&self) -> io::Result<()> {
// The epoll emulation on some illumos systems currently requires
// the pipe buffer to be completely empty for an edge-triggered
// wakeup on the pipe read side.
#[cfg(target_os = "illumos")]
self.empty();
match (&self.sender).write(&[1]) {
Ok(_) => Ok(()),
Err(ref err) if err.kind() == io::ErrorKind::WouldBlock => {
// The reading end is full so we'll empty the buffer and try
// again.
self.empty();
self.wake()
}
Err(ref err) if err.kind() == io::ErrorKind::Interrupted => self.wake(),
Err(err) => Err(err),
}
}
#[allow(dead_code)] // Only used by the `poll(2)` implementation.
pub(crate) fn ack_and_reset(&self) {
self.empty();
}
/// Empty the pipe's buffer, only need to call this if `wake` fails.
/// This ignores any errors.
fn empty(&self) {
let mut buf = [0; 4096];
loop {
match (&self.receiver).read(&mut buf) {
Ok(n) if n > 0 => continue,
_ => return,
}
}
}
}
impl AsRawFd for Waker {
fn as_raw_fd(&self) -> RawFd {
self.receiver.as_raw_fd()
}
}