Module timer 

Thread-pool timers: CreateThreadpoolTimer / SetThreadpoolTimer / WaitForThreadpoolTimerCallbacks / CloseThreadpoolTimer.

Two types share this machinery, and they differ in the one property that matters when writing the callback:

• ThreadpoolTimer fires exactly once per arming, and re-arming from inside its own callback is applied only after that callback returns, so repetition driven that way never overlaps itself.
• ThreadpoolPeriodicTimer repeats on a fixed period, and the pool may queue the next callback while the previous one is still running. Its callback must tolerate overlapping with itself.

The platform models both with one object and a period argument. This crate separates them so that concurrency contract belongs to a type rather than to an argument that is easy to skim past.

Choosing between them

Want a fixed cadence, and the callback is short or safe to overlap? Use ThreadpoolPeriodicTimer. Want the next delay measured from when the previous callback finished, with no overlap possible? Use a ThreadpoolTimer and re-arm it from inside its own callback with TimerFiring::rearm_after.

Due times

Relative due times (ThreadpoolTimer::set_after) count only time the system is awake, so sleep and hibernation do not consume the delay. Absolute due times (ThreadpoolTimer::set_at) name a wall-clock instant, which sleep and hibernation do pass through: a timer set for an instant that elapsed while the machine slept fires promptly on resume.

Structs

PeriodicTick

One tick of a ThreadpoolPeriodicTimer, handed to its callback.

ThreadpoolPeriodicTimer

An owned repeating thread-pool timer.

ThreadpoolTimer

An owned one-shot thread-pool timer.

TimerFiring

One firing of a ThreadpoolTimer, handed to its callback.