Quelle flaredispenser.vdmpp Sprache: VDM

\begin{vdm_al}
class FlareDispenser is subclass of GLOBAL, BaseThread

values

responseDB : map MissileType to Plan =
  {<MissileA> |-> [mk_(<FlareOneA>,900),
                   mk_(<FlareTwoA>,500),
                   mk_(<DoNothingA>,100),
                   mk_(<FlareOneA>,500)],
   <MissileB> |-> [mk_(<FlareTwoB>,500),
                   mk_(<FlareTwoB>,700)],
   <MissileC> |-> [mk_(<FlareOneC>,400),
                   mk_(<DoNothingC>,100),
                   mk_(<FlareTwoC>,400),
                   mk_(<FlareOneC>,500)] };

missilePriority : map MissileType to nat =
  {<None>     |-> 0,
   <MissileA> |-> 1,
   <MissileB> |-> 2,
   <MissileC> |-> 3 }

types

public Plan = seq of PlanStep;

public PlanStep = FlareType * Time;

instance variables

public curplan : Plan := [];
curprio        : nat := 0;
busy           : bool := false;
aperture       : Angle;
eventid        : [EventId];

operations

public FlareDispenser: Angle * [ThreadDef] ==> FlareDispenser
FlareDispenser(ang, tDef) ==
(aperture := ang;

  if tDef <> nil
  then (period := tDef.p;
        isPeriodic := tDef.isP;
       );
  BaseThread(self);
);

pure public GetAngle: () ==> nat
GetAngle() ==
  return aperture;

public addThreat: EventId * MissileType * Time ==> ()
addThreat (evid, pmt, ptime) ==
  if missilePriority(pmt) > curprio
  then (dcl newplan : Plan :=  [],
            newtime : Time := ptime;
        -- construct an absolute time plan
        for mk_(fltp, fltime) in responseDB(pmt) do
          (newplan := newplan ^ [mk_ (fltp, newtime)];
           newtime := newtime + fltime );
        -- immediately release the first action
        def mk_(fltp, fltime) = hd newplan;
            t = World`timerRef.GetTime() in
          releaseFlare(evid,fltp,fltime,t);
         -- store the rest of the plan
         curplan := tl newplan;
         eventid := evid;
         curprio := missilePriority(pmt);
         busy := true )
pre pmt in set dom missilePriority and
    pmt in set dom responseDB;

protected Step: () ==> ()
Step () ==
  (if len curplan > 0
   then (dcl curtime : Time := World`timerRef.GetTime(),
             done : bool := false;
         while not done do
           (dcl first : PlanStep := hd curplan,
                next : Plan := tl curplan;
            let mk_(fltp, fltime) = first in
              if fltime <= curtime
              then (releaseFlare(eventid,fltp,fltime,curtime);
                    curplan := next;
                    if len next = 0
                    then (curprio := 0;
                          done := true;
                          busy := false ) )
              else done := true ) ) );

private releaseFlare: EventId * FlareType * Time * Time ==> ()
releaseFlare (evid, pfltp, pt1, pt2) ==
  World`env.handleEvent(evid,pfltp,aperture,pt1,pt2);

public isFinished: () ==> ()
isFinished () == skip;

sync

mutex (Step);
mutex (addThreat);
per isFinished => not busy

end FlareDispenser
\end{vdm_al}

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