ex_undo.c revision 19304 
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[] = "@(#)ex_undo.c	10.6 (Berkeley) 3/6/96";
14#endif /* not lint */
15
16#include <sys/types.h>
17#include <sys/queue.h>
18
19#include <bitstring.h>
20#include <limits.h>
21#include <stdio.h>
22#include <stdlib.h>
23
24#include "../common/common.h"
25
26/*
27 * ex_undo -- u
28 *	Undo the last change.
29 *
30 * PUBLIC: int ex_undo __P((SCR *, EXCMD *));
31 */
32int
33ex_undo(sp, cmdp)
34	SCR *sp;
35	EXCMD *cmdp;
36{
37	EXF *ep;
38	MARK m;
39
40	/*
41	 * !!!
42	 * Historic undo always set the previous context mark.
43	 */
44	m.lno = sp->lno;
45	m.cno = sp->cno;
46	if (mark_set(sp, ABSMARK1, &m, 1))
47		return (1);
48
49	/*
50	 * !!!
51	 * Multiple undo isn't available in ex, as there's no '.' command.
52	 * Whether 'u' is undo or redo is toggled each time, unless there
53	 * was a change since the last undo, in which case it's an undo.
54	 */
55	ep = sp->ep;
56	if (!F_ISSET(ep, F_UNDO)) {
57		F_SET(ep, F_UNDO);
58		ep->lundo = FORWARD;
59	}
60	switch (ep->lundo) {
61	case BACKWARD:
62		if (log_forward(sp, &m))
63			return (1);
64		ep->lundo = FORWARD;
65		break;
66	case FORWARD:
67		if (log_backward(sp, &m))
68			return (1);
69		ep->lundo = BACKWARD;
70		break;
71	case NOTSET:
72		abort();
73	}
74	sp->lno = m.lno;
75	sp->cno = m.cno;
76	return (0);
77}
78