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//! A rust interface to the Linux kernel's timerfd API.
//!
//! # Example
//!
//! ```
//! use timerfd::{TimerFd, TimerState, SetTimeFlags};
//! use std::time::Duration;
//!
//! // Create a new timerfd
//! // (unwrap is actually fine here for most usecases)
//! let mut tfd = TimerFd::new().unwrap();
//!
//! // The timer is initially disarmed
//! assert_eq!(tfd.get_state(), TimerState::Disarmed);
//!
//! // Set the timer
//! tfd.set_state(TimerState::Oneshot(Duration::new(1, 0)), SetTimeFlags::Default);
//!
//! // Observe that the timer is now set
//! match tfd.get_state() {
//! TimerState::Oneshot(d) => println!("Remaining: {:?}", d),
//! _ => unreachable!(),
//! }
//!
//! // Wait for the remaining time
//! tfd.read();
//!
//! // It was a oneshot timer, so it's now disarmed
//! assert_eq!(tfd.get_state(), TimerState::Disarmed);
//! ```
//!
//! # Usage
//!
//! Unfortunately, this example can't show why you would use
//! timerfd in the first place: Because it creates a file descriptor
//! that you can monitor with `select(2)`, `poll(2)` and `epoll(2)`.
//!
//! In other words, the primary advantage this offers over any other
//! timer implementation is that it implements the `AsFd`/`AsRawFd` traits.
//!
//! The file descriptor becomes ready/readable whenever the timer expires.
#![warn(missing_debug_implementations)]
extern crate rustix;
use std::os::unix::prelude::*;
use std::time::Duration;
use std::io::Result as IoResult;
use std::fmt;
use rustix::fd::{AsFd, BorrowedFd, OwnedFd};
use rustix::time::{Itimerspec, TimerfdClockId};
#[derive(Clone, PartialEq, Eq)]
pub enum ClockId {
/// Available clocks:
///
/// A settable system-wide real-time clock.
Realtime = TimerfdClockId::Realtime as isize,
/// This clock is like CLOCK_REALTIME, but will wake the system if it is suspended. The
/// caller must have the CAP_WAKE_ALARM capability in order to set a timer against this
/// clock.
RealtimeAlarm = TimerfdClockId::RealtimeAlarm as isize,
/// A nonsettable monotonically increasing clock that measures time from some unspecified
/// point in the past that does not change after system startup.
Monotonic = TimerfdClockId::Monotonic as isize,
/// Like CLOCK_MONOTONIC, this is a monotonically increasing clock. However, whereas the
/// CLOCK_MONOTONIC clock does not measure the time while a system is suspended, the
/// CLOCK_BOOTTIME clock does include the time during which the system is suspended. This
/// is useful for applications that need to be suspend-aware. CLOCK_REALTIME is not
/// suitable for such applications, since that clock is affected by discon‐ tinuous
/// changes to the system clock.
Boottime = TimerfdClockId::Boottime as isize,
/// This clock is like CLOCK_BOOTTIME, but will wake the system if it is suspended. The
/// caller must have the CAP_WAKE_ALARM capability in order to set a timer against this
/// clock.
BoottimeAlarm = TimerfdClockId::BoottimeAlarm as isize,
}
fn clock_name (clock: &ClockId) -> &'static str {
match *clock {
ClockId::Realtime => "CLOCK_REALTIME",
ClockId::RealtimeAlarm => "CLOCK_REALTIME_ALARM",
ClockId::Monotonic => "CLOCK_MONOTONIC",
ClockId::Boottime => "CLOCK_BOOTTIME",
ClockId::BoottimeAlarm => "CLOCK_BOOTTIME_ALARM",
}
}
impl fmt::Display for ClockId {
fn fmt (&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(f, "{}", clock_name(self))
}
}
impl fmt::Debug for ClockId {
fn fmt (&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(f, "{} ({})", self.clone() as isize, clock_name(self))
}
}
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum SetTimeFlags {
/// Flags to `timerfd_settime(2)`.
///
/// The default is zero, i. e. all bits unset.
Default,
/// Interpret new_value.it_value as an absolute value on the timer's clock. The timer will
/// expire when the value of the timer's clock reaches the value specified in
/// new_value.it_value.
Abstime,
/// If this flag is specified along with TFD_TIMER_ABSTIME and the clock for this timer is
/// CLOCK_REALTIME or CLOCK_REALTIME_ALARM, then mark this timer as cancelable if the
/// real-time clock undergoes a discontinuous change (settimeofday(2), clock_settime(2),
/// or similar). When such changes occur, a current or future read(2) from the file
/// descriptor will fail with the error ECANCELED.
///
/// `TFD_TIMER_CANCEL_ON_SET` is useless without `TFD_TIMER_ABSTIME` set, cf. `fs/timerfd.c`.
/// Thus `TimerCancelOnSet`` implies `Abstime`.
TimerCancelOnSet,
}
use rustix::time::{TimerfdFlags, TimerfdTimerFlags};
mod structs;
/// Holds the state of a `TimerFd`.
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum TimerState {
/// The timer is disarmed and will not fire.
Disarmed,
/// The timer will fire once after the specified duration
/// and then disarm.
Oneshot(Duration),
/// The timer will fire once after `current` and then
/// automatically rearm with `interval` as its duration.
Periodic {
current: Duration,
interval: Duration,
}
}
/// Represents a timerfd.
///
/// See also [`timerfd_create(2)`].
///
/// [`timerfd_create(2)`]: http://man7.org/linux/man-pages/man2/timerfd_create.2.html
#[derive(Debug)]
pub struct TimerFd(OwnedFd);
impl TimerFd {
/// Creates a new `TimerFd`.
///
/// By default, it uses the monotonic clock, is blocking and does not close on exec.
/// The parameters allow you to change that.
///
/// # Errors
///
/// On Linux 2.6.26 and earlier, nonblocking and cloexec are not supported and setting them
/// will return an error of kind `ErrorKind::InvalidInput`.
///
/// This can also fail in various cases of resource exhaustion. Please check
/// `timerfd_create(2)` for details.
pub fn new_custom(clock: ClockId, nonblocking: bool, cloexec: bool) -> IoResult<TimerFd> {
let mut flags = TimerfdFlags::empty();
if nonblocking {
flags |= TimerfdFlags::NONBLOCK;
}
if cloexec {
flags |= TimerfdFlags::CLOEXEC;
}
let clock = match clock {
ClockId::Realtime => TimerfdClockId::Realtime,
ClockId::RealtimeAlarm => TimerfdClockId::RealtimeAlarm,
ClockId::Monotonic => TimerfdClockId::Monotonic,
ClockId::Boottime => TimerfdClockId::Boottime,
ClockId::BoottimeAlarm => TimerfdClockId::BoottimeAlarm,
};
let fd = rustix::time::timerfd_create(clock, flags)?;
Ok(TimerFd(fd))
}
/// Creates a new `TimerFd` with default settings.
///
/// Use `new_custom` to specify custom settings.
pub fn new() -> IoResult<TimerFd> {
TimerFd::new_custom(ClockId::Monotonic, false, false)
}
/// Sets this timerfd to a given `TimerState` and returns the old state.
pub fn set_state(&mut self, state: TimerState, sflags: SetTimeFlags) -> TimerState {
let flags = match sflags {
SetTimeFlags::Default => TimerfdTimerFlags::empty(),
SetTimeFlags::Abstime => TimerfdTimerFlags::ABSTIME,
SetTimeFlags::TimerCancelOnSet => {
TimerfdTimerFlags::ABSTIME | TimerfdTimerFlags::CANCEL_ON_SET
}
};
let new: Itimerspec = state.into();
let old = rustix::time::timerfd_settime(&self.0, flags, &new)
.expect("Looks like timerfd_settime failed in some undocumented way");
old.into()
}
/// Returns the current `TimerState`.
pub fn get_state(&self) -> TimerState {
let state = rustix::time::timerfd_gettime(&self.0)
.expect("Looks like timerfd_gettime failed in some undocumented way");
state.into()
}
/// Read from this timerfd.
///
/// Returns the number of timer expirations since the last read.
/// If this timerfd is operating in blocking mode (the default), it will
/// not return zero but instead block until the timer has expired at least once.
pub fn read(&self) -> u64 {
let mut buffer = [0_u8; 8];
loop {
match rustix::io::read(&self.0, &mut buffer) {
Ok(8) => {
let value = u64::from_ne_bytes(buffer);
assert_ne!(value, 0);
return value;
}
Err(rustix::io::Errno::WOULDBLOCK) => return 0,
Err(rustix::io::Errno::INTR) => (),
Err(e) => panic!("Unexpected read error: {}", e),
_ => unreachable!(),
}
}
}
}
impl AsRawFd for TimerFd {
fn as_raw_fd(&self) -> RawFd {
self.0.as_raw_fd()
}
}
impl FromRawFd for TimerFd {
unsafe fn from_raw_fd(fd: RawFd) -> Self {
TimerFd(FromRawFd::from_raw_fd(fd))
}
}
impl AsFd for TimerFd {
fn as_fd(&self) -> BorrowedFd<'_> {
self.0.as_fd()
}
}
impl From<TimerFd> for OwnedFd {
fn from(fd: TimerFd) -> OwnedFd {
fd.0
}
}
#[cfg(test)]
mod tests {
extern crate rustix;
use super::{ClockId, Duration, SetTimeFlags, TimerFd, TimerState};
#[test]
fn clockid_new_custom () {
fn __test_clockid (clockid: ClockId) {
let tfd = TimerFd::new_custom(clockid, true, false).unwrap();
assert_eq!(tfd.get_state(), TimerState::Disarmed);
}
__test_clockid(ClockId::Realtime);
__test_clockid(ClockId::Monotonic);
__test_clockid(ClockId::Boottime);
//__test_clockid(ClockId::RealtimeAlarm); // requires CAP_WAKE_ALARM
//__test_clockid(ClockId::BoottimeAlarm); // requires CAP_WAKE_ALARM
}
const TEST_TIMER_OFFSET: u64 = 100; // seconds from now
/// trivial monotonic timer some seconds into the future
#[test]
fn timerfd_settime_flags_default () {
let mut tfd = TimerFd::new().unwrap();
assert_eq!(tfd.get_state(), TimerState::Disarmed);
tfd.set_state(TimerState::Oneshot(Duration::new(TEST_TIMER_OFFSET, 0)),
SetTimeFlags::Default);
assert!(match tfd.get_state() { TimerState::Oneshot(_) => true, _ => false });
}
/// timer set from realtime clock
#[test]
fn timerfd_settime_flags_abstime () {
let mut tfd = TimerFd::new_custom(ClockId::Realtime, true, true).unwrap();
assert_eq!(tfd.get_state(), TimerState::Disarmed);
let now = rustix::time::clock_gettime(rustix::time::ClockId::Realtime);
tfd.set_state(TimerState::Oneshot(Duration::new(now.tv_sec as u64 + TEST_TIMER_OFFSET, 0)),
SetTimeFlags::Abstime);
assert!(match tfd.get_state() { TimerState::Oneshot(_) => true, _ => false });
}
/// same as abstime, with `TimerCancelOnSet`
#[test]
fn timerfd_settime_flags_abstime_cancel () {
let mut tfd = TimerFd::new_custom(ClockId::Realtime, true, true).unwrap();
assert_eq!(tfd.get_state(), TimerState::Disarmed);
let now = rustix::time::clock_gettime(rustix::time::ClockId::Realtime);
tfd.set_state(TimerState::Oneshot(Duration::new(now.tv_sec as u64 + TEST_TIMER_OFFSET, 0)),
SetTimeFlags::TimerCancelOnSet);
assert!(match tfd.get_state() { TimerState::Oneshot(_) => true, _ => false });
}
}