base_tokio/sys/linux/
event.rs

1// Copyright 2024 The ChromiumOS Authors
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5use std::os::fd::AsRawFd;
6
7use tokio::io::unix::AsyncFd;
8
9/// An async version of `base::Event`.
10pub struct EventTokio(AsyncFd<base::SafeDescriptor>);
11
12impl EventTokio {
13    /// WARNING: Sets O_NONBLOCK internally, which will also affect all clones of the `Event`.
14    pub fn new(event: base::Event) -> anyhow::Result<Self> {
15        let fd: base::SafeDescriptor = event.into();
16        base::add_fd_flags(fd.as_raw_fd(), libc::O_NONBLOCK)?;
17        Ok(Self(AsyncFd::new(fd)?))
18    }
19
20    /// Blocks until the event is signaled and clears the signal.
21    ///
22    /// It is undefined behavior to wait on an event from multiple threads or processes
23    /// simultaneously.
24    pub async fn wait(&self) -> std::io::Result<()> {
25        loop {
26            let mut guard = self.0.readable().await?;
27            let io_result = guard.try_io(|inner| {
28                let mut buf: u64 = 0;
29                // SAFETY: This is safe because we made this fd and the pointer we pass can not
30                // overflow because we give the syscall's size parameter properly.
31                let ret = unsafe {
32                    libc::read(
33                        inner.as_raw_fd(),
34                        &mut buf as *mut u64 as *mut libc::c_void,
35                        std::mem::size_of::<u64>(),
36                    )
37                };
38                if ret < 0 {
39                    return Err(std::io::Error::last_os_error());
40                }
41                if ret as usize != std::mem::size_of::<u64>() {
42                    return Err(std::io::Error::from(std::io::ErrorKind::UnexpectedEof));
43                }
44                Ok(())
45            });
46
47            match io_result {
48                Ok(result) => return result,
49                Err(_would_block) => continue,
50            }
51        }
52    }
53}
base_tokio/sys/linux/event.rs

base_tokio/sys/linux/
event.rs
