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#include <sys/types.h>
13#include <sys/queue.h>
14#include <sys/time.h>
15
16#include <bitstring.h>
17#include <limits.h>
18#include <stdio.h>
19#include <stdlib.h>
20
21#include "../common/common.h"
22
23/*
24 * ex_undo -- u
25 *	Undo the last change.
26 *
27 * PUBLIC: int ex_undo(SCR *, EXCMD *);
28 */
29int
30ex_undo(SCR *sp, EXCMD *cmdp)
31{
32	EXF *ep;
33	MARK m;
34
35	/*
36	 * !!!
37	 * Historic undo always set the previous context mark.
38	 */
39	m.lno = sp->lno;
40	m.cno = sp->cno;
41	if (mark_set(sp, ABSMARK1, &m, 1))
42		return (1);
43
44	/*
45	 * !!!
46	 * Multiple undo isn't available in ex, as there's no '.' command.
47	 * Whether 'u' is undo or redo is toggled each time, unless there
48	 * was a change since the last undo, in which case it's an undo.
49	 */
50	ep = sp->ep;
51	if (!F_ISSET(ep, F_UNDO)) {
52		F_SET(ep, F_UNDO);
53		ep->lundo = FORWARD;
54	}
55	switch (ep->lundo) {
56	case BACKWARD:
57		if (log_forward(sp, &m))
58			return (1);
59		ep->lundo = FORWARD;
60		break;
61	case FORWARD:
62		if (log_backward(sp, &m))
63			return (1);
64		ep->lundo = BACKWARD;
65		break;
66	case NOTSET:
67		abort();
68	}
69	sp->lno = m.lno;
70	sp->cno = m.cno;
71	return (0);
72}
73