Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!decwrl!decvax!ima!haddock!karl
From: karl@haddock.ima.isc.com (Karl Heuer)
Newsgroups: comp.lang.c
Subject: Re: 4.3 curses - how to discard "premature" input?
Message-ID: <11820@haddock.ima.isc.com>
Date: 21 Feb 89 20:41:55 GMT
References: <15336@oberon.USC.EDU> <697@sactoh0.UUCP> <1047@auspex.UUCP>
Reply-To: karl@haddock.ima.isc.com (Karl Heuer)
Distribution: usa
Organization: Interactive Systems, Boston
Lines: 41

In article <1047@auspex.UUCP> guy@auspex.UUCP (Guy Harris) writes:
>[fflush(stdin) doesn't work in 4.3BSD or ANSI C, and in any case doesn't
>touch the characters buffered at the driver level.]

Since there is no standard way to do this, I created my own interface (named
`clrbfi', after the TOPS-10 ttcall with the same functionality) which serves
as a portable wrapper around a non-portable operation.  The enclosed code
should work on BSD, USG, and V8 systems.  I'd like to include the conditional
code for MSDOS, too, but I don't know how to do it there.  (Suggestions by
e-mail, please.)

Karl W. Z. Heuer (ima!haddock!karl or karl@haddock.isc.com), The Walking Lint
-------- cut here --------
/*
 * Clear input buffer on terminal.  Result is 0 if successful, else -1 (e.g.
 * if the specified descriptor or stream is not a tty).
 */
#if defined(_S_USG)
#include <sys/termio.h>
#define	ioarg	struct termio
#define	GET	TCGETA
#define	SET	TCSETAF
#else
#include <sgtty.h>
#define	ioarg	struct sgttyb
#define	GET	TIOCGETP
#define	SET	TIOCSETP
#endif

extern int ioctl();

int clrbfi(f) int f; {
    ioarg io;
    return ((ioctl(f, GET, &io) >= 0 && ioctl(f, SET, &io) >= 0) ? 0 : -1);
}

#include <stdio.h>
int fclrbfi(fp) FILE *fp; {
    fp->_cnt = 0;
    return (clrbfi(fileno(fp)));
}