class Timer

Timers need a constexpr constructor, as it is valid to construct them in static storage.

TODO(https://fxbug.dev/328306129): The default value for the clock_id parameter should be

removed, thus forcing users of the Timer class to explicitly declare the clock they wish

to use.

Timers are not moved or copied.

Construct a timer that will run on |dispatcher| and call |callback| whenever the timer is

triggered. If |type| is Periodic the timer will restart itself after calling |callback|. To

prevent this, call Start with a duration of zero. This can be done inside |callback| to prevent

further timer callbacks. Caller must ensure that |dispatcher| remains running for the lifetime

of the Timer object or until Stop has been called on the timer.

Equivalent to Set with no slack

The deadline parameter should be interpreted differently depending on the clock_id_ field.

If clock_id_ is set to ZX_CLOCK_MONOTONIC, deadline is a zx_instant_mono_t.

If clock_id_ is set to ZX_CLOCK_BOOT, deadline is a zx_instant_boot_t.

Private accessors for timer tests.

This function returns a zx_instant_mono_t if the expected_clock_id is ZX_CLOCK_MONOTONIC and a

zx_instant_boot_t if the expected_clock_id is ZX_CLOCK_BOOT.

Destroying the timer will synchronously Stop the timer before completing destruction.

Start the timer with |interval| amount of time before the timer triggers. The same interval is

used when restarting the timer if it is periodic. Calling Start with an |interval| of zero on a

periodic timer will allow the timer to trigger at its next scheduled time but it will not

restart after that. Calling Start with an |interval| of zero on a one-shot timer has no effect.

Calling Start with |interval| greater than zero will adjust the timer interval to the new value

AND postpone any upcoming trigger to not be called until |interval| amount of time has passed.

For periodic timers this will also adjust the interval of all future timer triggers. This can

safely be done from the timer callback.

Returns |ZX_OK| on success.

Returns |ZX_ERR_BAD_STATE| if the dispatcher is shutting down.

Returns |ZX_ERR_NOT_SUPPORTED| if not supported by the dispatcher.

Stop a running timer synchronously, blocking until the stop is complete. When Stop returns the

callback provided in the constructor is guaranteed to not run again until Start is called. If

the callback is currently running it will run to completion before Stop returns.

Set up a timer that executes once

This function specifies a callback function to be run after a specified

deadline passes. The function will be called one time.

deadline: specifies when the timer should be executed

callback: the function to call when the timer expires

arg: the argument to pass to the callback

The timer function is declared as:

void callback(Timer *, zx_time_t now, void *arg) { ... }

Cancel a pending timer

Returns true if the timer was canceled before it was

scheduled in a cpu and false otherwise or if the timer

was not scheduled at all.

Special helper routine to simultaneously try to acquire a spinlock and

check for timer cancel, which is needed in a few special cases. Returns

ZX_OK if spinlock was acquired, ZX_ERR_TIMED_OUT if timer was canceled.

A OneShot timer will only fire once for each call to Start. A Periodic timer will fire

regularly at the interval specified in the Start call.