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//! Timer API via file descriptors.
//!
//! Timer FD is a Linux-only API to create timers and get expiration
//! notifications through file descriptors.
//!
//! For more documentation, please read [timerfd_create(2)](https://man7.org/linux/man-pages/man2/timerfd_create.2.html).
//!
//! # Examples
//!
//! Create a new one-shot timer that expires after 1 second.
//! ```
//! # use std::os::unix::io::AsRawFd;
//! # use nix::sys::timerfd::{TimerFd, ClockId, TimerFlags, TimerSetTimeFlags,
//! # Expiration};
//! # use nix::sys::time::{TimeSpec, TimeValLike};
//! # use nix::unistd::read;
//! #
//! // We create a new monotonic timer.
//! let timer = TimerFd::new(ClockId::CLOCK_MONOTONIC, TimerFlags::empty())
//! .unwrap();
//!
//! // We set a new one-shot timer in 1 seconds.
//! timer.set(
//! Expiration::OneShot(TimeSpec::seconds(1)),
//! TimerSetTimeFlags::empty()
//! ).unwrap();
//!
//! // We wait for the timer to expire.
//! timer.wait().unwrap();
//! ```
use crate::sys::time::timer::TimerSpec;
pub use crate::sys::time::timer::{Expiration, TimerSetTimeFlags};
use crate::unistd::read;
use crate::{errno::Errno, Result};
use libc::c_int;
use std::os::unix::io::{AsRawFd, FromRawFd, RawFd};
/// A timerfd instance. This is also a file descriptor, you can feed it to
/// other interfaces consuming file descriptors, epoll for example.
#[derive(Debug)]
pub struct TimerFd {
fd: RawFd,
}
impl AsRawFd for TimerFd {
fn as_raw_fd(&self) -> RawFd {
self.fd
}
}
impl FromRawFd for TimerFd {
unsafe fn from_raw_fd(fd: RawFd) -> Self {
TimerFd { fd }
}
}
libc_enum! {
/// The type of the clock used to mark the progress of the timer. For more
/// details on each kind of clock, please refer to [timerfd_create(2)](https://man7.org/linux/man-pages/man2/timerfd_create.2.html).
#[repr(i32)]
#[non_exhaustive]
pub enum ClockId {
CLOCK_REALTIME,
CLOCK_MONOTONIC,
CLOCK_BOOTTIME,
CLOCK_REALTIME_ALARM,
CLOCK_BOOTTIME_ALARM,
}
}
libc_bitflags! {
/// Additional flags to change the behaviour of the file descriptor at the
/// time of creation.
pub struct TimerFlags: c_int {
TFD_NONBLOCK;
TFD_CLOEXEC;
}
}
impl TimerFd {
/// Creates a new timer based on the clock defined by `clockid`. The
/// underlying fd can be assigned specific flags with `flags` (CLOEXEC,
/// NONBLOCK). The underlying fd will be closed on drop.
pub fn new(clockid: ClockId, flags: TimerFlags) -> Result<Self> {
Errno::result(unsafe { libc::timerfd_create(clockid as i32, flags.bits()) })
.map(|fd| Self { fd })
}
/// Sets a new alarm on the timer.
///
/// # Types of alarm
///
/// There are 3 types of alarms you can set:
///
/// - one shot: the alarm will trigger once after the specified amount of
/// time.
/// Example: I want an alarm to go off in 60s and then disable itself.
///
/// - interval: the alarm will trigger every specified interval of time.
/// Example: I want an alarm to go off every 60s. The alarm will first
/// go off 60s after I set it and every 60s after that. The alarm will
/// not disable itself.
///
/// - interval delayed: the alarm will trigger after a certain amount of
/// time and then trigger at a specified interval.
/// Example: I want an alarm to go off every 60s but only start in 1h.
/// The alarm will first trigger 1h after I set it and then every 60s
/// after that. The alarm will not disable itself.
///
/// # Relative vs absolute alarm
///
/// If you do not set any `TimerSetTimeFlags`, then the `TimeSpec` you pass
/// to the `Expiration` you want is relative. If however you want an alarm
/// to go off at a certain point in time, you can set `TFD_TIMER_ABSTIME`.
/// Then the one shot TimeSpec and the delay TimeSpec of the delayed
/// interval are going to be interpreted as absolute.
///
/// # Disabling alarms
///
/// Note: Only one alarm can be set for any given timer. Setting a new alarm
/// actually removes the previous one.
///
/// Note: Setting a one shot alarm with a 0s TimeSpec disables the alarm
/// altogether.
pub fn set(&self, expiration: Expiration, flags: TimerSetTimeFlags) -> Result<()> {
let timerspec: TimerSpec = expiration.into();
Errno::result(unsafe {
libc::timerfd_settime(
self.fd,
flags.bits(),
timerspec.as_ref(),
std::ptr::null_mut(),
)
})
.map(drop)
}
/// Get the parameters for the alarm currently set, if any.
pub fn get(&self) -> Result<Option<Expiration>> {
let mut timerspec = TimerSpec::none();
Errno::result(unsafe { libc::timerfd_gettime(self.fd, timerspec.as_mut()) }).map(|_| {
if timerspec.as_ref().it_interval.tv_sec == 0
&& timerspec.as_ref().it_interval.tv_nsec == 0
&& timerspec.as_ref().it_value.tv_sec == 0
&& timerspec.as_ref().it_value.tv_nsec == 0
{
None
} else {
Some(timerspec.into())
}
})
}
/// Remove the alarm if any is set.
pub fn unset(&self) -> Result<()> {
Errno::result(unsafe {
libc::timerfd_settime(
self.fd,
TimerSetTimeFlags::empty().bits(),
TimerSpec::none().as_ref(),
std::ptr::null_mut(),
)
})
.map(drop)
}
/// Wait for the configured alarm to expire.
///
/// Note: If the alarm is unset, then you will wait forever.
pub fn wait(&self) -> Result<()> {
while let Err(e) = read(self.fd, &mut [0u8; 8]) {
if e != Errno::EINTR {
return Err(e);
}
}
Ok(())
}
}
impl Drop for TimerFd {
fn drop(&mut self) {
if !std::thread::panicking() {
let result = Errno::result(unsafe { libc::close(self.fd) });
if let Err(Errno::EBADF) = result {
panic!("close of TimerFd encountered EBADF");
}
}
}
}
|
