nix/sys/
timerfd.rs

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
//! 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::{AsFd, AsRawFd, BorrowedFd, FromRawFd, OwnedFd, RawFd};

/// A timerfd instance. This is also a file descriptor, you can feed it to
/// other interfaces taking file descriptors as arguments, [`epoll`] for example.
///
/// [`epoll`]: crate::sys::epoll
#[derive(Debug)]
pub struct TimerFd {
    fd: OwnedFd,
}

impl AsFd for TimerFd {
    fn as_fd(&self) -> BorrowedFd<'_> {
        self.fd.as_fd()
    }
}

impl FromRawFd for TimerFd {
    unsafe fn from_raw_fd(fd: RawFd) -> Self {
        TimerFd {
            fd: unsafe { OwnedFd::from_raw_fd(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 {
        /// A settable system-wide real-time clock.
        CLOCK_REALTIME,
        /// A non-settable monotonically increasing clock.
        ///
        /// Does not change after system startup.
        /// Does not measure time while the system is suspended.
        CLOCK_MONOTONIC,
        /// Like `CLOCK_MONOTONIC`, except that `CLOCK_BOOTTIME` includes the time
        /// that the system was suspended.
        CLOCK_BOOTTIME,
        /// Like `CLOCK_REALTIME`, but will wake the system if it is suspended.
        CLOCK_REALTIME_ALARM,
        /// Like `CLOCK_BOOTTIME`, but will wake the system if it is suspended.
        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 {
        /// Set the `O_NONBLOCK` flag on the open file description referred to by the new file descriptor.
        TFD_NONBLOCK;
        /// Set the `FD_CLOEXEC` flag on the file descriptor.
        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.
    #[doc(alias("timerfd_create"))]
    pub fn new(clockid: ClockId, flags: TimerFlags) -> Result<Self> {
        Errno::result(unsafe {
            libc::timerfd_create(clockid as i32, flags.bits())
        })
        .map(|fd| Self {
            fd: unsafe { OwnedFd::from_raw_fd(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.
    ///
    /// # Cancel on a clock change
    ///
    /// If you set a `TFD_TIMER_CANCEL_ON_SET` alongside `TFD_TIMER_ABSTIME`
    /// and the clock for this timer is `CLOCK_REALTIME` or `CLOCK_REALTIME_ALARM`,
    /// then this timer is marked as cancelable if the real-time clock undergoes
    /// a discontinuous change.
    ///
    /// # 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.
    #[doc(alias("timerfd_settime"))]
    pub fn set(
        &self,
        expiration: Expiration,
        flags: TimerSetTimeFlags,
    ) -> Result<()> {
        let timerspec: TimerSpec = expiration.into();
        Errno::result(unsafe {
            libc::timerfd_settime(
                self.fd.as_fd().as_raw_fd(),
                flags.bits(),
                timerspec.as_ref(),
                std::ptr::null_mut(),
            )
        })
        .map(drop)
    }

    /// Get the parameters for the alarm currently set, if any.
    #[doc(alias("timerfd_gettime"))]
    pub fn get(&self) -> Result<Option<Expiration>> {
        let mut timerspec = TimerSpec::none();
        Errno::result(unsafe {
            libc::timerfd_gettime(
                self.fd.as_fd().as_raw_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.
    #[doc(alias("timerfd_settime"))]
    pub fn unset(&self) -> Result<()> {
        Errno::result(unsafe {
            libc::timerfd_settime(
                self.fd.as_fd().as_raw_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.as_fd().as_raw_fd(), &mut [0u8; 8]) {
            if e == Errno::ECANCELED {
                break;
            }
            if e != Errno::EINTR {
                return Err(e);
            }
        }

        Ok(())
    }
}