/*
 * Copyright (c) 1989 The Regents of the University of California.
 * All rights reserved.
 *
 * %sccs.include.redist.c%
 */

#ifndef lint
static char sccsid[] = "@(#)ttymsg.c	5.9 (Berkeley) 08/01/91";
#endif /* not lint */

#include <sys/types.h>
#include <sys/uio.h>
#include <signal.h>
#include <fcntl.h>
#include <dirent.h>
#include <errno.h>
#include <paths.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

/*
 * Display the contents of a uio structure on a terminal.  Used by wall(1),
 * syslogd(8), and talk(1).  Forks and finishes in child if write would block, 
 * waiting up to tmout seconds.  Returns pointer to error string on unexpected 
 * error; string is not newline-terminated.  Various "normal" errors are 
 * ignored (exclusive-use, lack of permission, etc.).
 */
char *
ttymsg(iov, iovcnt, line, tmout)
	struct iovec *iov;
	int iovcnt;
	char *line;
	int tmout;
{
	static char device[MAXNAMLEN] = _PATH_DEV;
	static char errbuf[1024];
	register int cnt, fd, left, wret;
	struct iovec localiov[6];
	int forked = 0;

	if (iovcnt > 6)
		return ("too many iov's (change code in wall/ttymsg.c)");
	/*
	 * open will fail on slip lines or exclusive-use lines
	 * if not running as root; not an error.
	 */
	(void) strcpy(device + sizeof(_PATH_DEV) - 1, line);
	if ((fd = open(device, O_WRONLY|O_NONBLOCK, 0)) < 0) {
		if (errno == EBUSY || errno == EACCES)
			return (NULL);
		(void) snprintf(errbuf, sizeof(errbuf),
		    "%s: %s", device, strerror(errno));
		return (errbuf);
	}

	for (cnt = left = 0; cnt < iovcnt; ++cnt)
		left += iov[cnt].iov_len;

	for (;;) {
		wret = writev(fd, iov, iovcnt);
		if (wret >= left)
			break;
		if (wret >= 0) {
			left -= wret;
			if (iov != localiov) {
				bcopy(iov, localiov, 
				    iovcnt * sizeof(struct iovec));
				iov = localiov;
			}
			for (cnt = 0; wret >= iov->iov_len; ++cnt) {
				wret -= iov->iov_len;
				++iov;
				--iovcnt;
			}
			if (wret) {
				iov->iov_base += wret;
				iov->iov_len -= wret;
			}
			continue;
		}
		if (errno == EWOULDBLOCK) {
			int cpid, off = 0;

			if (forked) {
				(void) close(fd);
				_exit(1);
			}
			cpid = fork();
			if (cpid < 0) {
				(void) snprintf(errbuf, sizeof(errbuf),
				    "fork: %s", strerror(errno));
				(void) close(fd);
				return (errbuf);
			}
			if (cpid) {	/* parent */
				(void) close(fd);
				return (NULL);
			}
			forked++;
			/* wait at most tmout seconds */
			(void) signal(SIGALRM, SIG_DFL);
			(void) signal(SIGTERM, SIG_DFL); /* XXX */
			(void) sigsetmask(0);
			(void) alarm((u_int)tmout);
			(void) fcntl(fd, O_NONBLOCK, &off);
			continue;
		} 
		/*
		 * We get ENODEV on a slip line if we're running as root,
		 * and EIO if the line just went away.
		 */
		if (errno == ENODEV || errno == EIO)
			break;
		(void) close(fd);
		if (forked)
			_exit(1);
		(void) snprintf(errbuf, sizeof(errbuf),
		    "%s: %s", device, strerror(errno));
		return (errbuf);
	}

	(void) close(fd);
	if (forked)
		_exit(0);
	return (NULL);
}