//! 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)](http://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::TimeSpec;
use crate::unistd::read;
use crate::{errno::Errno, Error, Result};
use bitflags::bitflags;
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)](http://man7.org/linux/man-pages/man2/timerfd_create.2.html).
#[repr(i32)]
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;
}
}
bitflags! {
/// Flags that are used for arming the timer.
pub struct TimerSetTimeFlags: libc::c_int {
const TFD_TIMER_ABSTIME = libc::TFD_TIMER_ABSTIME;
}
}
#[derive(Debug, Clone, Copy)]
struct TimerSpec(libc::itimerspec);
impl TimerSpec {
pub fn none() -> Self {
Self(libc::itimerspec {
it_interval: libc::timespec {
tv_sec: 0,
tv_nsec: 0,
},
it_value: libc::timespec {
tv_sec: 0,
tv_nsec: 0,
},
})
}
}
impl AsRef<libc::itimerspec> for TimerSpec {
fn as_ref(&self) -> &libc::itimerspec {
&self.0
}
}
impl From<Expiration> for TimerSpec {
fn from(expiration: Expiration) -> TimerSpec {
match expiration {
Expiration::OneShot(t) => TimerSpec(libc::itimerspec {
it_interval: libc::timespec {
tv_sec: 0,
tv_nsec: 0,
},
it_value: *t.as_ref(),
}),
Expiration::IntervalDelayed(start, interval) => TimerSpec(libc::itimerspec {
it_interval: *interval.as_ref(),
it_value: *start.as_ref(),
}),
Expiration::Interval(t) => TimerSpec(libc::itimerspec {
it_interval: *t.as_ref(),
it_value: *t.as_ref(),
}),
}
}
}
impl From<TimerSpec> for Expiration {
fn from(timerspec: TimerSpec) -> Expiration {
match timerspec {
TimerSpec(libc::itimerspec {
it_interval:
libc::timespec {
tv_sec: 0,
tv_nsec: 0,
},
it_value: ts,
}) => Expiration::OneShot(ts.into()),
TimerSpec(libc::itimerspec {
it_interval: int_ts,
it_value: val_ts,
}) => {
if (int_ts.tv_sec == val_ts.tv_sec) && (int_ts.tv_nsec == val_ts.tv_nsec) {
Expiration::Interval(int_ts.into())
} else {
Expiration::IntervalDelayed(val_ts.into(), int_ts.into())
}
}
}
}
}
/// An enumeration allowing the definition of the expiration time of an alarm,
/// recurring or not.
#[derive(Debug, Clone, Copy, PartialEq)]
pub enum Expiration {
OneShot(TimeSpec),
IntervalDelayed(TimeSpec, TimeSpec),
Interval(TimeSpec),
}
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 disables 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();
let timerspec_ptr: *mut libc::itimerspec = &mut timerspec.0;
Errno::result(unsafe { libc::timerfd_gettime(self.fd, timerspec_ptr) }).map(|_| {
if timerspec.0.it_interval.tv_sec == 0
&& timerspec.0.it_interval.tv_nsec == 0
&& timerspec.0.it_value.tv_sec == 0
&& timerspec.0.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<()> {
loop {
if let Err(e) = read(self.fd, &mut [0u8; 8]) {
match e {
Error::Sys(Errno::EINTR) => continue,
_ => return Err(e),
}
} else {
break;
}
}
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(Error::Sys(Errno::EBADF)) = result {
panic!("close of TimerFd encountered EBADF");
}
}
}
}