Copyright (C) 1992, Digital Equipment Corporation
All rights reserved.
See the file COPYRIGHT for a full description.
by Steve Glassman, Mark Manasse and Greg Nelson
Last modified on Mon Feb 24 13:59:53 PST 1992 by muller
modified on Wed Sep 11 15:53:09 PDT 1991 by msm
<*PRAGMA LL*>
INTERFACE XScrollQueue; (* = RingBuffer(XScrollQElt) *)
IMPORT PaintPrivate;
TYPE
T = RECORD
lo, hi: CARDINAL := 0;
buff : REF ARRAY OF PaintPrivate.ScrollRec := NIL
END;
buff[lo..hi-1] circularly are the active entries; lo = hi => the queue
is empty; lo # hi => buff # NIL.
CONST Empty = T{0, 0, NIL};
<*INLINE*> PROCEDURE IsEmpty (READONLY rb: T): BOOLEAN;
Return whether rb is empty.
PROCEDURE Insert (VAR rb: T; READONLY e: PaintPrivate.ScrollRec);
Insert e into rb, extending rb if necessary.
EXCEPTION Exhausted;
PROCEDURE Remove (VAR rb: T): PaintPrivate.ScrollRec RAISES {Exhausted};
Raise the exception if br is empty, else remove the oldest element of rb
and return it.
END XScrollQueue.