Path: utzoo!utgpu!watserv1!watmath!att!rutgers!cs.utexas.edu!uunet!mcrware!jejones
From: jejones@mcrware.UUCP (James Jones)
Newsgroups: comp.os.os9
Subject: Re: ttyfly() for os9? (try#2)
Summary: check out GS_RDY getstat call
Keywords: pending input
Message-ID: <2588@mcrware.UUCP>
Date: 31 Aug 90 16:12:24 GMT
References: <1990Aug30.152825.21217@cs.utk.edu>
Reply-To: jejones@mcrware.UUCP (James Jones)
Organization: Microware Systems Corp., Des Moines, Iowa
Lines: 28

What you need to check out is the GS_RDY getstat call, which tells you how
many characters are waiting to be read.  (For historical reasons, it tech-
nically thinks not having any characters waiting is an "error," but that
doesn't get in the way.)

For efficiency's sake, I'd seriously suggest buffer the waiting characters,
so in C, you'd have something like

static char	mybuf[MYBUFSIZE];	/* or whatever */
static char *next;
static int	chleft;

ttyfly()
{
	if (--chleft < 0) {
		if ((chleft = _gs_rdy(0)) < 0)
			return 0;
		if (chleft > MYBUFSIZE)
			chleft = MYBUFSIZE;				/* Code defensively! */
		chleft = read(0, mybuf, chleft);
		if (chleft <= 0)
			return 0;
		next = mybuf;
	}
	return *next++;
}

	James Jones