TIMERS(2)TIMERS(2)NAMEtimers - interval timersSYNOPSIS
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();
DESCRIPTION
Timers provides simple interval timing. Timeouts are notified by a
message sent on a channel, allowing them to provide timeouts in alt
statements.
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 mil‐
liseconds.
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.
EXAMPLE
Wait for data to be sent on an input channel, but give up if it does
not arrive within 600 milliseconds:
t := Timer.start(600);
alt {
data := <-input =>
t.stop();
# process the data
<-t.timeout =>
# request timed out
}
SEE ALSOsys-millisec(2), sys-sleep(2)TIMERS(2)
