1/*-
2 * Copyright (c) 1992, 1993, 1994
3 *	The Regents of the University of California.  All rights reserved.
4 * Copyright (c) 1992, 1993, 1994, 1995, 1996
5 *	Keith Bostic.  All rights reserved.
6 *
7 * See the LICENSE file for redistribution information.
8 */
9
10#include "config.h"
11
12#ifndef lint
13static const char sccsid[] = "$Id: ex_undo.c,v 10.7 2001/06/25 15:19:21 skimo Exp $";
14#endif /* not lint */
15
16#include <sys/types.h>
17#include <sys/queue.h>
18#include <sys/time.h>
19
20#include <bitstring.h>
21#include <limits.h>
22#include <stdio.h>
23#include <stdlib.h>
24
25#include "../common/common.h"
26
27/*
28 * ex_undo -- u
29 *	Undo the last change.
30 *
31 * PUBLIC: int ex_undo __P((SCR *, EXCMD *));
32 */
33int
34ex_undo(SCR *sp, EXCMD *cmdp)
35{
36	EXF *ep;
37	MARK m;
38
39	/*
40	 * !!!
41	 * Historic undo always set the previous context mark.
42	 */
43	m.lno = sp->lno;
44	m.cno = sp->cno;
45	if (mark_set(sp, ABSMARK1, &m, 1))
46		return (1);
47
48	/*
49	 * !!!
50	 * Multiple undo isn't available in ex, as there's no '.' command.
51	 * Whether 'u' is undo or redo is toggled each time, unless there
52	 * was a change since the last undo, in which case it's an undo.
53	 */
54	ep = sp->ep;
55	if (!F_ISSET(ep, F_UNDO)) {
56		F_SET(ep, F_UNDO);
57		ep->lundo = FORWARD;
58	}
59	switch (ep->lundo) {
60	case BACKWARD:
61		if (log_forward(sp, &m))
62			return (1);
63		ep->lundo = FORWARD;
64		break;
65	case FORWARD:
66		if (log_backward(sp, &m))
67			return (1);
68		ep->lundo = BACKWARD;
69		break;
70	case NOTSET:
71		abort();
72	}
73	sp->lno = m.lno;
74	sp->cno = m.cno;
75	return (0);
76}
77