Struct TimerFd

pub struct TimerFd { /* private fields */ }

A timerfd instance. This is also a file descriptor, you can feed it to other interfaces taking file descriptors as arguments, epoll for example.

Implementations

impl TimerFd

pub fn new(clockid: ClockId, flags: TimerFlags) -> Result<Self>

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 set( &self, expiration: Expiration, flags: TimerSetTimeFlags, ) -> Result<()>

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.

pub fn get(&self) -> Result<Option<Expiration>>

Get the parameters for the alarm currently set, if any.

pub fn unset(&self) -> Result<()>

Remove the alarm if any is set.

pub fn wait(&self) -> Result<()>

Wait for the configured alarm to expire.

Note: If the alarm is unset, then you will wait forever.

Trait Implementations

impl AsFd for TimerFd

fn as_fd(&self) -> BorrowedFd<'_>

Borrows the file descriptor.

impl Debug for TimerFd

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl FromRawFd for TimerFd

unsafe fn from_raw_fd(fd: RawFd) -> Self

Constructs a new instance of Self from the given raw file descriptor.