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| 1 | +//! Timer API via signals. |
| 2 | +//! |
| 3 | +//! Timer is a POSIX API to create timers and get expiration notifications |
| 4 | +//! through queued Unix signals, for the current process. This is similar to |
| 5 | +//! Linux's timerfd mechanism, except that API is specific to Linux and makes |
| 6 | +//! use of file polling. |
| 7 | +//! |
| 8 | +//! For more documentation, please read [timer_create](https://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_create.html). |
| 9 | +//! |
| 10 | +//! # Examples |
| 11 | +//! |
| 12 | +//! Create an interval timer that signals SIGALARM every 250 milliseconds. |
| 13 | +//! |
| 14 | +//! ```no_run |
| 15 | +//! use nix::sys::signal::{self, SigEvent, SigHandler, SigevNotify, Signal}; |
| 16 | +//! use nix::sys::timer::{Expiration, Timer, TimerSetTimeFlags}; |
| 17 | +//! use nix::time::ClockId; |
| 18 | +//! use std::convert::TryFrom; |
| 19 | +//! use std::sync::atomic::{AtomicU64, Ordering}; |
| 20 | +//! use std::thread::yield_now; |
| 21 | +//! use std::time::Duration; |
| 22 | +//! |
| 23 | +//! const SIG: Signal = Signal::SIGALRM; |
| 24 | +//! static ALARMS: AtomicU64 = AtomicU64::new(0); |
| 25 | +//! |
| 26 | +//! extern "C" fn handle_alarm(signal: libc::c_int) { |
| 27 | +//! let signal = Signal::try_from(signal).unwrap(); |
| 28 | +//! if signal == SIG { |
| 29 | +//! ALARMS.fetch_add(1, Ordering::Relaxed); |
| 30 | +//! } |
| 31 | +//! } |
| 32 | +//! |
| 33 | +//! fn main() { |
| 34 | +//! let clockid = ClockId::CLOCK_MONOTONIC; |
| 35 | +//! let sigevent = SigEvent::new(SigevNotify::SigevSignal { |
| 36 | +//! signal: SIG, |
| 37 | +//! si_value: 0, |
| 38 | +//! }); |
| 39 | +//! |
| 40 | +//! let mut timer = Timer::new(clockid, sigevent).unwrap(); |
| 41 | +//! let expiration = Expiration::Interval(Duration::from_millis(250).into()); |
| 42 | +//! let flags = TimerSetTimeFlags::empty(); |
| 43 | +//! timer.set(expiration, flags).expect("could not set timer"); |
| 44 | +//! |
| 45 | +//! let handler = SigHandler::Handler(handle_alarm); |
| 46 | +//! unsafe { signal::signal(SIG, handler) }.unwrap(); |
| 47 | +//! |
| 48 | +//! loop { |
| 49 | +//! let alarms = ALARMS.load(Ordering::Relaxed); |
| 50 | +//! if alarms >= 10 { |
| 51 | +//! println!("total alarms handled: {}", alarms); |
| 52 | +//! break; |
| 53 | +//! } |
| 54 | +//! yield_now() |
| 55 | +//! } |
| 56 | +//! } |
| 57 | +//! ``` |
| 58 | +use crate::sys::signal::SigEvent; |
| 59 | +use crate::sys::time::timer::TimerSpec; |
| 60 | +pub use crate::sys::time::timer::{Expiration, TimerSetTimeFlags}; |
| 61 | +use crate::time::ClockId; |
| 62 | +use crate::{errno::Errno, Result}; |
| 63 | +use core::mem; |
| 64 | + |
| 65 | +/// A Unix signal per-process timer. |
| 66 | +#[derive(Debug)] |
| 67 | +#[repr(transparent)] |
| 68 | +pub struct Timer(libc::timer_t); |
| 69 | + |
| 70 | +impl Timer { |
| 71 | + /// Creates a new timer based on the clock defined by `clockid`. The details |
| 72 | + /// of the signal and its handler are defined by the passed `sigevent`. |
| 73 | + pub fn new(clockid: ClockId, mut sigevent: SigEvent) -> Result<Self> { |
| 74 | + let mut timer_id: mem::MaybeUninit<libc::timer_t> = mem::MaybeUninit::uninit(); |
| 75 | + Errno::result(unsafe { |
| 76 | + libc::timer_create( |
| 77 | + clockid.as_raw(), |
| 78 | + sigevent.as_mut_ptr(), |
| 79 | + timer_id.as_mut_ptr(), |
| 80 | + ) |
| 81 | + }) |
| 82 | + .map(|_| { |
| 83 | + // SAFETY: libc::timer_create is responsible for initializing |
| 84 | + // timer_id. |
| 85 | + unsafe { Self(timer_id.assume_init()) } |
| 86 | + }) |
| 87 | + } |
| 88 | + |
| 89 | + /// Set a new alarm on the timer. |
| 90 | + /// |
| 91 | + /// # Types of alarm |
| 92 | + /// |
| 93 | + /// There are 3 types of alarms you can set: |
| 94 | + /// |
| 95 | + /// - one shot: the alarm will trigger once after the specified amount of |
| 96 | + /// time. |
| 97 | + /// Example: I want an alarm to go off in 60s and then disable itself. |
| 98 | + /// |
| 99 | + /// - interval: the alarm will trigger every specified interval of time. |
| 100 | + /// Example: I want an alarm to go off every 60s. The alarm will first |
| 101 | + /// go off 60s after I set it and every 60s after that. The alarm will |
| 102 | + /// not disable itself. |
| 103 | + /// |
| 104 | + /// - interval delayed: the alarm will trigger after a certain amount of |
| 105 | + /// time and then trigger at a specified interval. |
| 106 | + /// Example: I want an alarm to go off every 60s but only start in 1h. |
| 107 | + /// The alarm will first trigger 1h after I set it and then every 60s |
| 108 | + /// after that. The alarm will not disable itself. |
| 109 | + /// |
| 110 | + /// # Relative vs absolute alarm |
| 111 | + /// |
| 112 | + /// If you do not set any `TimerSetTimeFlags`, then the `TimeSpec` you pass |
| 113 | + /// to the `Expiration` you want is relative. If however you want an alarm |
| 114 | + /// to go off at a certain point in time, you can set `TFD_TIMER_ABSTIME`. |
| 115 | + /// Then the one shot TimeSpec and the delay TimeSpec of the delayed |
| 116 | + /// interval are going to be interpreted as absolute. |
| 117 | + /// |
| 118 | + /// # Disabling alarms |
| 119 | + /// |
| 120 | + /// Note: Only one alarm can be set for any given timer. Setting a new alarm |
| 121 | + /// actually removes the previous one. |
| 122 | + /// |
| 123 | + /// Note: Setting a one shot alarm with a 0s TimeSpec disable the alarm |
| 124 | + /// altogether. |
| 125 | + pub fn set(&mut self, expiration: Expiration, flags: TimerSetTimeFlags) -> Result<()> { |
| 126 | + let timerspec: TimerSpec = expiration.into(); |
| 127 | + Errno::result(unsafe { |
| 128 | + libc::timer_settime( |
| 129 | + self.0, |
| 130 | + flags.bits(), |
| 131 | + timerspec.as_ref(), |
| 132 | + core::ptr::null_mut(), |
| 133 | + ) |
| 134 | + }) |
| 135 | + .map(drop) |
| 136 | + } |
| 137 | + |
| 138 | + /// Get the parameters for the alarm currently set, if any. |
| 139 | + pub fn get(&self) -> Result<Option<Expiration>> { |
| 140 | + let mut timerspec = TimerSpec::none(); |
| 141 | + Errno::result(unsafe { libc::timer_gettime(self.0, timerspec.as_mut()) }).map(|_| { |
| 142 | + if timerspec.as_ref().it_interval.tv_sec == 0 |
| 143 | + && timerspec.as_ref().it_interval.tv_nsec == 0 |
| 144 | + && timerspec.as_ref().it_value.tv_sec == 0 |
| 145 | + && timerspec.as_ref().it_value.tv_nsec == 0 |
| 146 | + { |
| 147 | + None |
| 148 | + } else { |
| 149 | + Some(timerspec.into()) |
| 150 | + } |
| 151 | + }) |
| 152 | + } |
| 153 | + |
| 154 | + /// Return the number of timers that have overrun |
| 155 | + /// |
| 156 | + /// Each timer is able to queue one signal to the process at a time, meaning |
| 157 | + /// if the signal is not handled before the next expiration the timer has |
| 158 | + /// 'overrun'. This function returns how many times that has happened to |
| 159 | + /// this timer, up to `libc::DELAYTIMER_MAX`. If more than the maximum |
| 160 | + /// number of overruns have happened the return is capped to the maximum. |
| 161 | + pub fn overruns(&self) -> i32 { |
| 162 | + unsafe { libc::timer_getoverrun(self.0) } |
| 163 | + } |
| 164 | +} |
| 165 | + |
| 166 | +impl Drop for Timer { |
| 167 | + fn drop(&mut self) { |
| 168 | + if !std::thread::panicking() { |
| 169 | + let result = Errno::result(unsafe { libc::timer_delete(self.0) }); |
| 170 | + if let Err(Errno::EINVAL) = result { |
| 171 | + panic!("close of Timer encountered EINVAL"); |
| 172 | + } |
| 173 | + } |
| 174 | + } |
| 175 | +} |
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