ref: e81c54ba2ecc673a4d5f8aed0e9b52841fe07b0d
dir: /man/2/timers/
.TH TIMERS 2 .SH NAME timers \- interval timers .SH SYNOPSIS .EX 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(); .EE .SH DESCRIPTION .B Timers provides simple interval timing. Timeouts are notified by a message sent on a channel, allowing them to provide timeouts in .B alt statements. .PP The module must first be initialised by calling .BR 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 .BR shutdown , which stops it synchronously; by using the process ID returned by .B init to kill it; or by killing the process group of the process that called .BR init (since the timing processes remain in that group). .I Minms gives the minimum granularity of timing requests in milliseconds. .TP .BI Timer.start( msec ) Returns a .B Timer that will expire in .I msec milliseconds, measured with the granularity of either .IR sys-sleep (2) or the granularity set by .BR init , whichever is greater. .TP .IB t .timeout An arbitrary integer value is sent on this channel when the timer .I t expires. .TP .IB t .stop() The timer .I t is stopped and removed from the interval timing queue, if it has not already expired. .PP Each .B Timer value times a single interval. When a timer .I t expires, the timing process attempts, at that and each subsequent timing interval, to send on .IB t .timeout until the expiry message is delivered or the timer is stopped. .SH EXAMPLE Wait for data to be sent on an input channel, but give up if it does not arrive within 600 milliseconds: .IP .EX t := Timer.start(600); alt { data := <-input => t.stop(); # process the data <-t.timeout => # request timed out } .EE .SH SEE ALSO .IR sys-millisec (2), .IR sys-sleep (2)