include "timers.m";
timers := load Timers Timers->PATH;

Timer: adt
{
   timeout: chan of int;
   start:   fn(msec: int): ref Timer;
   stop:    fn(t: self ref Timer);
};

init:     fn(minms: int): int;
shutdown: fn();

The module must first be initialised by calling init, which starts a process to manage the interval timers and returns its process ID. Before exit, the caller must shut the timing process down either by calling shutdown, which stops it synchronously; by using the process ID returned by init to kill it; or by killing the process group of the process that called init (since the timing processes remain in that group). Minms gives the minimum granularity of timing requests in milliseconds.

Timer.start(msec)

Returns a Timer that will expire in msec milliseconds, measured with the granularity of either sys-sleep(2) or the granularity set by init, whichever is greater.

t.timeout

An arbitrary integer value is sent on this channel when the timer t expires.

t.stop()

The timer t is stopped and removed from the interval timing queue, if it has not already expired.

Each Timer value times a single interval. When a timer t expires, the timing process attempts, at that and each subsequent timing interval, to send on t.timeout until the expiry message is delivered or the timer is stopped.

t := Timer.start(600);
alt {
data := <-input =>
	t.stop();
	# process the data
<-t.timeout =>
	# request timed out
}