gistfile1.txt

readers-writers : monitor;
begin
readercount : integer;
busy : boolean;
OKtoread, OKtowrite : condition;

procedure startread;

	begin
	if busy then OKtoread.wait;
	readercount := readercount + 1;
	OKtoread.signal;
	(* Once one reader can start, they all can *)
	end startread;

procedure endread;

	begin
	readercount := readercount - 1;
	if readercount = 0 then OKtowrite.signal;
	end endread;

procedure startwrite;

	begin
	if busy OR readercount != 0 then OKtowrite.wait;
	busy := true;
	end startwrite;

procedure endwrite;

	begin
	busy := false;
	if OKtoread.queue then OKtoread.signal
		else OKtowrite.signal;
	end endwrite;

begin (* initialization *)
readercount := 0;
busy := false;
end;

end readers-writers;