Copyright (C) 1992, Digital Equipment Corporation
All rights reserved.
See the file COPYRIGHT for a full description.
Last modified on Wed Oct 13 17:36:52 PDT 1993 by sfreeman
GENERIC MODULE FreeList(Elem);
where Elem is an Image.T and so has a field
next: Elem.T := NIL;
and a method.
destroy();
New (): Elem.T;
returns an Elem.T object, possibly from the free list. Elem.Ts from
this procedure will be put onto the free list and destroy() will be
called.
Free(t: Elem.T)
explicitly calls t.destroy() and puts it on the free list
IMPORT WeakRef, PictureRep;
VAR
freeMu := NEW(MUTEX);
free : Elem.T := NIL;
PROCEDURE New (): Elem.T =
VAR res: Elem.T := NIL;
BEGIN
LOCK freeMu DO
IF free # NIL THEN res := free; free := res.next; END;
END;
IF res = NIL THEN res := NEW(T); END;
EVAL WeakRef.FromRef(res, CleanUp);
RETURN res;
END New;
PROCEDURE CleanUp (<*UNUSED*> READONLY w: WeakRef.T; r: REFANY) =
BEGIN
Free(NARROW(r, Elem.T));
END CleanUp;
PROCEDURE Free (t: Elem.T) =
BEGIN
t.destroy();
LOCK freeMu DO t.next := free; free := t; END;
END Free;
BEGIN
END FreeList.