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Major signal overhaul.  We no longer longjmp all over the place.
Instead, routines responsible to gathering user input (or in some
cases outputting data) catch the signals and set flags as needed.
Because of this some handlers are install without the SA_RESTART
flag so syscalls are not restarted and we can check the flag.  All
signal handlers are now safe.

This should make the flow of control a bit more grokable but the
code is still ugly.

/*	$OpenBSD: tty.c,v 1.13 2001/11/20 20:50:00 millert Exp $	*/
/*	$NetBSD: tty.c,v 1.7 1997/07/09 05:25:46 mikel Exp $	*/

/*
 * Copyright (c) 1980, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#ifndef lint
#if 0
static char sccsid[] = "@(#)tty.c	8.2 (Berkeley) 4/20/95";
#else
static char rcsid[] = "$OpenBSD: tty.c,v 1.13 2001/11/20 20:50:00 millert Exp $";
#endif
#endif /* not lint */

/*
 * Mail -- a mail program
 *
 * Generally useful tty stuff.
 */

#include "rcv.h"
#include "extern.h"
#include <sys/ioctl.h>
#include <errno.h>

static	cc_t		c_erase;	/* Current erase char */
static	cc_t		c_kill;		/* Current kill char */
#ifndef TIOCSTI
static	int		ttyset;		/* We must now do erase/kill */
#endif
static	volatile sig_atomic_t	ttysignal;	/* Interrupted by a signal? */

/*
 * Read all relevant header fields.
 */

int
grabh(hp, gflags)
	struct header *hp;
	int gflags;
{
	struct termios ttybuf;
#ifndef TIOCSTI
	struct sigaction savequit;
#else
# ifdef	TIOCEXT
	int extproc;
	int flag;
# endif /* TIOCEXT */
#endif
	struct sigaction savetstp;
	struct sigaction savettou;
	struct sigaction savettin;
	struct sigaction act;
	char *s;
	int error;

	sigemptyset(&act.sa_mask);
	act.sa_flags = SA_RESTART;
	act.sa_handler = SIG_DFL;
	(void)sigaction(SIGTSTP, &act, &savetstp);
	(void)sigaction(SIGTTOU, &act, &savettou);
	(void)sigaction(SIGTTIN, &act, &savettin);
	error = 1;
#ifndef TIOCSTI
	ttyset = 0;
#endif
	if (tcgetattr(fileno(stdin), &ttybuf) < 0) {
		warn("tcgetattr");
		return(-1);
	}
	c_erase = ttybuf.c_cc[VERASE];
	c_kill = ttybuf.c_cc[VKILL];
#ifndef TIOCSTI
	ttybuf.c_cc[VERASE] = 0;
	ttybuf.c_cc[VKILL] = 0;
	act.sa_handler = SIG_IGN;
	if (sigaction(SIGQUIT, &act, &savequit) == 0 &&
	    savequit.sa_handler == SIG_DFL)
		(void)sigaction(SIGQUIT, &savequit, NULL);
#else
# ifdef	TIOCEXT
	extproc = ((ttybuf.c_lflag & EXTPROC) ? 1 : 0);
	if (extproc) {
		flag = 0;
		if (ioctl(fileno(stdin), TIOCEXT, &flag) < 0)
			warn("TIOCEXT: off");
	}
# endif /* TIOCEXT */
#endif
	if (gflags & GTO) {
#ifndef TIOCSTI
		if (!ttyset && hp->h_to != NIL)
			ttyset++, tcsetattr(fileno(stdin), TCSADRAIN, &ttybuf);
#endif
		s = readtty("To: ", detract(hp->h_to, 0));
		if (s == NULL)
			goto out;
		hp->h_to = extract(s, GTO);
	}
	if (gflags & GSUBJECT) {
#ifndef TIOCSTI
		if (!ttyset && hp->h_subject != NULL)
			ttyset++, tcsetattr(fileno(stdin), TCSADRAIN, &ttybuf);
#endif
		s = readtty("Subject: ", hp->h_subject);
		if (s == NULL)
			goto out;
		hp->h_subject = s;
	}
	if (gflags & GCC) {
#ifndef TIOCSTI
		if (!ttyset && hp->h_cc != NIL)
			ttyset++, tcsetattr(fileno(stdin), TCSADRAIN, &ttybuf);
#endif
		s = readtty("Cc: ", detract(hp->h_cc, 0));
		if (s == NULL)
			goto out;
		hp->h_cc = extract(s, GCC);
	}
	if (gflags & GBCC) {
#ifndef TIOCSTI
		if (!ttyset && hp->h_bcc != NIL)
			ttyset++, tcsetattr(fileno(stdin), TCSADRAIN, &ttybuf);
#endif
		s = readtty("Bcc: ", detract(hp->h_bcc, 0));
		if (s == NULL)
			goto out;
		hp->h_bcc = extract(s, GBCC);
	}
	error = 0;
out:
	(void)sigaction(SIGTSTP, &savetstp, NULL);
	(void)sigaction(SIGTTOU, &savettou, NULL);
	(void)sigaction(SIGTTIN, &savettin, NULL);
#ifndef TIOCSTI
	ttybuf.c_cc[VERASE] = c_erase;
	ttybuf.c_cc[VKILL] = c_kill;
	if (ttyset)
		tcsetattr(fileno(stdin), TCSADRAIN, &ttybuf);
	(void)sigaction(SIGQUIT, &savequit, NULL);
#else
# ifdef	TIOCEXT
	if (extproc) {
		flag = 1;
		if (ioctl(fileno(stdin), TIOCEXT, &flag) < 0)
			warn("TIOCEXT: on");
	}
# endif /* TIOCEXT */
#endif
	return(error);
}

/*
 * Read up a header from standard input.
 * The source string has the preliminary contents to
 * be read.
 *
 */

char *
readtty(pr, src)
	char pr[], src[];
{
	struct sigaction act, oact;
	sigset_t oset;
	char ch, canonb[BUFSIZ];
	char *cp, *cp2;
	int c;

	fputs(pr, stdout);
	fflush(stdout);
	if (src != NULL && strlen(src) > BUFSIZ - 2) {
		puts("too long to edit");
		return(src);
	}
#ifndef TIOCSTI
	if (src != NULL)
		cp = copy(src, canonb);
	else
		cp = copy("", canonb);
	fputs(canonb, stdout);
	fflush(stdout);
#else
	cp = src == NULL ? "" : src;
	while ((c = *cp++) != '\0') {
		if ((c_erase != _POSIX_VDISABLE && c == c_erase) ||
		    (c_kill != _POSIX_VDISABLE && c == c_kill)) {
			ch = '\\';
			ioctl(0, TIOCSTI, &ch);
		}
		ch = c;
		ioctl(0, TIOCSTI, &ch);
	}
	cp = canonb;
	*cp = 0;
#endif
	cp2 = cp;
	while (cp2 < canonb + BUFSIZ)
		*cp2++ = 0;
	cp2 = cp;
	sigemptyset(&act.sa_mask);
	act.sa_flags = 0;		/* Note: will not restart syscalls */
	act.sa_handler = ttyint;
	(void)sigaction(SIGINT, &act, &oact);
	act.sa_handler = ttystop;
	(void)sigaction(SIGTSTP, &act, NULL);
	(void)sigaction(SIGTTOU, &act, NULL);
	(void)sigaction(SIGTTIN, &act, NULL);
	(void)sigprocmask(SIG_UNBLOCK, &intset, &oset);
	clearerr(stdin);
	while (cp2 < canonb + BUFSIZ) {
		c = getc(stdin);
		switch (ttysignal) {
			case SIGINT:
				ttysignal = 0;
				cp2 = NULL;
				c = EOF;
				/* FALLTHROUGH */
			case 0:
				break;
			default:
				ttysignal = 0;
				goto redo;
		}
		if (c == EOF || c == '\n')
			break;
		*cp2++ = c;
	}
	act.sa_handler = SIG_DFL;
	sigemptyset(&act.sa_mask);
	act.sa_flags = SA_RESTART;
	(void)sigprocmask(SIG_SETMASK, &oset, NULL);
	(void)sigaction(SIGTSTP, &act, NULL);
	(void)sigaction(SIGTTOU, &act, NULL);
	(void)sigaction(SIGTTIN, &act, NULL);
	(void)sigaction(SIGTTIN, &oact, NULL);
	if (cp2 == NULL)
		return(NULL);			/* user hit ^C */
	*cp2 = '\0';
	if (c == EOF && ferror(stdin)) {
redo:
		cp = strlen(canonb) > 0 ? canonb : NULL;
		clearerr(stdin);
		/* XXX - make iterative, not recursive */
		return(readtty(pr, cp));
	}
#ifndef TIOCSTI
	if (cp == NULL || *cp == '\0')
		return(src);
	cp2 = cp;
	if (!ttyset)
		return(strlen(canonb) > 0 ? savestr(canonb) : NULL);
	while (*cp != '\0') {
		c = *cp++;
		if (c_erase != _POSIX_VDISABLE && c == c_erase) {
			if (cp2 == canonb)
				continue;
			if (cp2[-1] == '\\') {
				cp2[-1] = c;
				continue;
			}
			cp2--;
			continue;
		}
		if (c_kill != _POSIX_VDISABLE && c == c_kill) {
			if (cp2 == canonb)
				continue;
			if (cp2[-1] == '\\') {
				cp2[-1] = c;
				continue;
			}
			cp2 = canonb;
			continue;
		}
		*cp2++ = c;
	}
	*cp2 = '\0';
#endif
	if (equal("", canonb))
		return("");
	return(savestr(canonb));
}

/*
 * Receipt continuation.
 */
void
ttystop(s)
	int s;
{
	struct sigaction act, oact;
	sigset_t nset;
	int save_errno;

	/*
	 * Save old handler and set to default.
	 * Unblock receipt of 's' and then resend it.
	 */
	save_errno = errno;
	(void)sigemptyset(&act.sa_mask);
	act.sa_flags = SA_RESTART;
	act.sa_handler = SIG_DFL;
	(void)sigaction(s, &act, &oact);
	(void)sigemptyset(&nset);
	(void)sigaddset(&nset, s);
	(void)sigprocmask(SIG_UNBLOCK, &nset, NULL);
	(void)kill(0, s);
	(void)sigprocmask(SIG_BLOCK, &nset, NULL);
	(void)sigaction(s, &oact, NULL);
	ttysignal = s;
	errno = save_errno;
}

/*ARGSUSED*/
void
ttyint(s)
	int s;
{

	ttysignal = s;
}