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//! Uses the `timerfd` crate to sleep using an OS timer.
//!
//! Run with:
//!
//! ```
//! cargo run --example linux-timerfd
//! ```
#[cfg(target_os = "linux")]
fn main() -> std::io::Result<()> {
use std::io;
use std::os::unix::io::AsRawFd;
use std::time::{Duration, Instant};
use async_io::Async;
use futures_lite::future;
use rustix::fd::BorrowedFd;
use timerfd::{SetTimeFlags, TimerFd, TimerState};
/// Sleeps using an OS timer.
async fn sleep(dur: Duration) -> io::Result<()> {
// Create an OS timer.
let mut timer = TimerFd::new()?;
timer.set_state(TimerState::Oneshot(dur), SetTimeFlags::Default);
// When the OS timer fires, a 64-bit integer can be read from it.
Async::new(timer)?
.read_with(|t| {
// Safety: We assume `as_raw_fd()` returns a valid fd. When we
// can depend on Rust >= 1.63, where `AsFd` is stabilized, and
// when `TimerFd` implements it, we can remove this unsafe and
// simplify this.
let fd = unsafe { BorrowedFd::borrow_raw(t.as_raw_fd()) };
rustix::io::read(fd, &mut [0u8; 8]).map_err(io::Error::from)
})
.await?;
Ok(())
}
future::block_on(async {
let start = Instant::now();
println!("Sleeping...");
// Sleep for a second using an OS timer.
sleep(Duration::from_secs(1)).await?;
println!("Woke up after {:?}", start.elapsed());
Ok(())
})
}
#[cfg(not(target_os = "linux"))]
fn main() {
println!("This example works only on Linux!");
}
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