nix/sys/
timerfd.rs

1//! Timer API via file descriptors.
2//!
3//! Timer FD is a Linux-only API to create timers and get expiration
4//! notifications through file descriptors.
5//!
6//! For more documentation, please read [timerfd_create(2)](https://man7.org/linux/man-pages/man2/timerfd_create.2.html).
7//!
8//! # Examples
9//!
10//! Create a new one-shot timer that expires after 1 second.
11//! ```
12//! # use std::os::unix::io::AsRawFd;
13//! # use nix::sys::timerfd::{TimerFd, ClockId, TimerFlags, TimerSetTimeFlags,
14//! #    Expiration};
15//! # use nix::sys::time::{TimeSpec, TimeValLike};
16//! # use nix::unistd::read;
17//! #
18//! // We create a new monotonic timer.
19//! let timer = TimerFd::new(ClockId::CLOCK_MONOTONIC, TimerFlags::empty())
20//!     .unwrap();
21//!
22//! // We set a new one-shot timer in 1 seconds.
23//! timer.set(
24//!     Expiration::OneShot(TimeSpec::seconds(1)),
25//!     TimerSetTimeFlags::empty()
26//! ).unwrap();
27//!
28//! // We wait for the timer to expire.
29//! timer.wait().unwrap();
30//! ```
31use crate::sys::time::timer::TimerSpec;
32pub use crate::sys::time::timer::{Expiration, TimerSetTimeFlags};
33use crate::unistd::read;
34use crate::{errno::Errno, Result};
35use libc::c_int;
36use std::os::unix::io::{AsRawFd, FromRawFd, RawFd};
37
38/// A timerfd instance. This is also a file descriptor, you can feed it to
39/// other interfaces consuming file descriptors, epoll for example.
40#[derive(Debug)]
41pub struct TimerFd {
42    fd: RawFd,
43}
44
45impl AsRawFd for TimerFd {
46    fn as_raw_fd(&self) -> RawFd {
47        self.fd
48    }
49}
50
51impl FromRawFd for TimerFd {
52    unsafe fn from_raw_fd(fd: RawFd) -> Self {
53        TimerFd { fd }
54    }
55}
56
57libc_enum! {
58    /// The type of the clock used to mark the progress of the timer. For more
59    /// details on each kind of clock, please refer to [timerfd_create(2)](https://man7.org/linux/man-pages/man2/timerfd_create.2.html).
60    #[repr(i32)]
61    #[non_exhaustive]
62    pub enum ClockId {
63        /// A settable system-wide real-time clock.
64        CLOCK_REALTIME,
65        /// A non-settable monotonically increasing clock.
66        ///
67        /// Does not change after system startup.
68        /// Does not measure time while the system is suspended.
69        CLOCK_MONOTONIC,
70        /// Like `CLOCK_MONOTONIC`, except that `CLOCK_BOOTTIME` includes the time
71        /// that the system was suspended.
72        CLOCK_BOOTTIME,
73        /// Like `CLOCK_REALTIME`, but will wake the system if it is suspended.
74        CLOCK_REALTIME_ALARM,
75        /// Like `CLOCK_BOOTTIME`, but will wake the system if it is suspended.
76        CLOCK_BOOTTIME_ALARM,
77    }
78}
79
80libc_bitflags! {
81    /// Additional flags to change the behaviour of the file descriptor at the
82    /// time of creation.
83    pub struct TimerFlags: c_int {
84        /// Set the `O_NONBLOCK` flag on the open file description referred to by the new file descriptor.
85        TFD_NONBLOCK;
86        /// Set the `FD_CLOEXEC` flag on the file descriptor.
87        TFD_CLOEXEC;
88    }
89}
90
91impl TimerFd {
92    /// Creates a new timer based on the clock defined by `clockid`. The
93    /// underlying fd can be assigned specific flags with `flags` (CLOEXEC,
94    /// NONBLOCK). The underlying fd will be closed on drop.
95    pub fn new(clockid: ClockId, flags: TimerFlags) -> Result<Self> {
96        Errno::result(unsafe { libc::timerfd_create(clockid as i32, flags.bits()) })
97            .map(|fd| Self { fd })
98    }
99
100    /// Sets a new alarm on the timer.
101    ///
102    /// # Types of alarm
103    ///
104    /// There are 3 types of alarms you can set:
105    ///
106    ///   - one shot: the alarm will trigger once after the specified amount of
107    /// time.
108    ///     Example: I want an alarm to go off in 60s and then disable itself.
109    ///
110    ///   - interval: the alarm will trigger every specified interval of time.
111    ///     Example: I want an alarm to go off every 60s. The alarm will first
112    ///     go off 60s after I set it and every 60s after that. The alarm will
113    ///     not disable itself.
114    ///
115    ///   - interval delayed: the alarm will trigger after a certain amount of
116    ///     time and then trigger at a specified interval.
117    ///     Example: I want an alarm to go off every 60s but only start in 1h.
118    ///     The alarm will first trigger 1h after I set it and then every 60s
119    ///     after that. The alarm will not disable itself.
120    ///
121    /// # Relative vs absolute alarm
122    ///
123    /// If you do not set any `TimerSetTimeFlags`, then the `TimeSpec` you pass
124    /// to the `Expiration` you want is relative. If however you want an alarm
125    /// to go off at a certain point in time, you can set `TFD_TIMER_ABSTIME`.
126    /// Then the one shot TimeSpec and the delay TimeSpec of the delayed
127    /// interval are going to be interpreted as absolute.
128    ///
129    /// # Disabling alarms
130    ///
131    /// Note: Only one alarm can be set for any given timer. Setting a new alarm
132    /// actually removes the previous one.
133    ///
134    /// Note: Setting a one shot alarm with a 0s TimeSpec disables the alarm
135    /// altogether.
136    pub fn set(&self, expiration: Expiration, flags: TimerSetTimeFlags) -> Result<()> {
137        let timerspec: TimerSpec = expiration.into();
138        Errno::result(unsafe {
139            libc::timerfd_settime(
140                self.fd,
141                flags.bits(),
142                timerspec.as_ref(),
143                std::ptr::null_mut(),
144            )
145        })
146        .map(drop)
147    }
148
149    /// Get the parameters for the alarm currently set, if any.
150    pub fn get(&self) -> Result<Option<Expiration>> {
151        let mut timerspec = TimerSpec::none();
152        Errno::result(unsafe { libc::timerfd_gettime(self.fd, timerspec.as_mut()) }).map(|_| {
153            if timerspec.as_ref().it_interval.tv_sec == 0
154                && timerspec.as_ref().it_interval.tv_nsec == 0
155                && timerspec.as_ref().it_value.tv_sec == 0
156                && timerspec.as_ref().it_value.tv_nsec == 0
157            {
158                None
159            } else {
160                Some(timerspec.into())
161            }
162        })
163    }
164
165    /// Remove the alarm if any is set.
166    pub fn unset(&self) -> Result<()> {
167        Errno::result(unsafe {
168            libc::timerfd_settime(
169                self.fd,
170                TimerSetTimeFlags::empty().bits(),
171                TimerSpec::none().as_ref(),
172                std::ptr::null_mut(),
173            )
174        })
175        .map(drop)
176    }
177
178    /// Wait for the configured alarm to expire.
179    ///
180    /// Note: If the alarm is unset, then you will wait forever.
181    pub fn wait(&self) -> Result<()> {
182        while let Err(e) = read(self.fd, &mut [0u8; 8]) {
183            if e != Errno::EINTR {
184                return Err(e);
185            }
186        }
187
188        Ok(())
189    }
190}
191
192impl Drop for TimerFd {
193    fn drop(&mut self) {
194        if !std::thread::panicking() {
195            let result = Errno::result(unsafe { libc::close(self.fd) });
196            if let Err(Errno::EBADF) = result {
197                panic!("close of TimerFd encountered EBADF");
198            }
199        }
200    }
201}
nix/sys/timerfd.rs

nix/sys/
timerfd.rs
