DEFINITION MODULE TimerHandler ;
(* It also provides the Executive with a basic round robin scheduler. *)
EXPORT QUALIFIED TicksPerSecond, GetTicks,
EVENT,
Sleep, ArmEvent, WaitOn, Cancel, ReArmEvent ;
CONST
TicksPerSecond (const)
TicksPerSecond = 25 ; (* Number of ticks per second. *)
TYPE
EVENT (type)
EVENT ;
(*
GetTicks - returns the number of ticks since boottime.
*)
GetTicks
PROCEDURE GetTicks () : CARDINAL ;
(*
Sleep - suspends the current process for a time, t.
The time is measured in ticks.
*)
Sleep
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.
*)
ArmEvent
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.
The event, e, is always assigned to NIL when the function
finishes.
*)
WaitOn
PROCEDURE WaitOn (VAR 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.
*)
Cancel
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.
*)
ReArmEvent
PROCEDURE ReArmEvent (e: EVENT; t: CARDINAL) : BOOLEAN ;
END TimerHandler.