Sync

Task/Queue-Definition/Component-Pascal/queue-definition-1.component

@@ -0,0 +1,63 @@
+MODULE Queue;
+IMPORT StdLog,Boxes;
+
+TYPE
+	Queue* = POINTER TO RECORD
+		first,last: LONGINT;
+		queue: POINTER TO ARRAY OF Boxes.Object;
+	END;
+	
+	PROCEDURE NewQueue*(cap: LONGINT): Queue;
+	VAR
+		q: Queue;
+	BEGIN
+		NEW(q);q.first := 0; q.last := 0;
+		NEW(q.queue,cap);
+		RETURN q		
+	END NewQueue;
+	
+	PROCEDURE (q: Queue) IsEmpty*(): BOOLEAN, NEW;
+	VAR
+	BEGIN
+		RETURN (q.first = q.last)
+	END IsEmpty;
+	
+	PROCEDURE (q: Queue) Push*(o: Boxes.Object),NEW;
+	VAR
+		i,j,oldSize,newSize: LONGINT;
+		queue: POINTER TO ARRAY OF Boxes.Object;
+	BEGIN
+		IF q.IsEmpty() THEN
+			q.queue[q.last] := o;
+			q.last := (q.last + 1) MOD LEN(q.queue)
+		ELSE
+			q.queue[q.last] := o;
+			q.last := (q.last + 1) MOD LEN(q.queue);
+			IF q.first = q.last THEN
+				(* grow queue *)
+				newSize := LEN(q.queue) + (LEN(q.queue) DIV 2);
+				(* new queue*)
+				NEW(queue,newSize);
+				(* move data from old queue to new queue *)
+				i := q.first; j := 0;oldSize := LEN(q.queue) - q.first + q.last;
+				WHILE (j < oldSize ) & (j < LEN(queue) - 1) DO
+					queue[j] := q.queue[i];
+					i := (i + 1) MOD LEN(q.queue);INC(j)
+				END;
+				q.queue := queue;q.first := 0;q.last := j
+			END
+		END;
+	END Push;
+	
+	PROCEDURE (q: Queue) Pop*(): Boxes.Object, NEW;
+	VAR
+		o: Boxes.Object;
+	BEGIN
+		ASSERT(~q.IsEmpty());
+		o := q.queue[q.first];
+		q.queue[q.first] := NIL;
+		q.first := (q.first + 1) MOD LEN(q.queue);
+		RETURN o;
+	END Pop;
+
+END Queue.