The GNU Modula-2 front end to GCC

gm2-libs-coroutines/TimerHandler

DEFINITION MODULE TimerHandler ;

(*
    Description: provides a simple timer handler for the
                 Executive.
                 It also provides the Executive with a basic
                 round robin scheduler.
*)

EXPORT QUALIFIED TicksPerSecond, GetTicks,
                 EVENT,
                 Sleep, ArmEvent, WaitOn, Cancel, ReArmEvent ;


CONST

   TicksPerSecond =   25 ;  (* Number of ticks per second.         *)

TYPE

   EVENT ;


(*
   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 ;


END TimerHandler.