DEFINITION MODULE TimerHandler ;
Description: provides a simple timer handler for the
It also provides the Executive with a basic
round robin scheduler.
EXPORT QUALIFIED TicksPerSecond, GetTicks,
Sleep, ArmEvent, WaitOn, Cancel, ReArmEvent ;
TicksPerSecond = 25 ; (* Number of ticks per second. *)
GetTicks - returns the number of ticks since boottime.
PROCEDURE GetTicks () : CARDINAL ;
Sleep - suspends the current process for a time, t.
The time is measured in ticks.
PROCEDURE Sleep (t: CARDINAL) ;
ArmEvent - initializes an event, e, to occur at time, t.
The time, t, is measured in ticks.
The event is NOT placed onto the event queue.
PROCEDURE ArmEvent (t: CARDINAL) : EVENT ;
WaitOn - places event, e, onto the event queue and then the calling
process suspends. It is resumed up by either the event
expiring or the event, e, being cancelled.
TRUE is returned if the event was cancelled
FALSE is returned if the event expires.
PROCEDURE WaitOn (e: EVENT) : BOOLEAN ;
Cancel - cancels the event, e, on the event queue and makes
the appropriate process runnable again.
TRUE is returned if the event was cancelled and
FALSE is returned is the event was not found or
no process was waiting on this event.
PROCEDURE Cancel (e: EVENT) : BOOLEAN ;
ReArmEvent - removes an event, e, from the event queue. A new time
is given to this event and it is then re-inserted onto the
event queue in the correct place.
TRUE is returned if this occurred
FALSE is returned if the event was not found.
PROCEDURE ReArmEvent (e: EVENT; t: CARDINAL) : BOOLEAN ;