TIMERS(2) TIMERS(2)
NAME
timers - interval timers
SYNOPSIS
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 noti-
fied by a message sent on a channel, allowing them to pro-
vide 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 tim-
ing 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 sub-
sequent timing interval, to send on t.timeout until the
expiry message is delivered or the timer is stopped.
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TIMERS(2) TIMERS(2)
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 ALSO
sys-millisec(2), sys-sleep(2)
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