1 files changed, 77 insertions, 0 deletions
diff --git a/contrib/nvi/ex/ex_undo.c b/contrib/nvi/ex/ex_undo.c
new file mode 100644
index 0000000..0b0b5b2
--- /dev/null
+++ b/contrib/nvi/ex/ex_undo.c
@@ -0,0 +1,77 @@
+/*-
+ * Copyright (c) 1992, 1993, 1994
+ *	The Regents of the University of California.  All rights reserved.
+ * Copyright (c) 1992, 1993, 1994, 1995, 1996
+ *	Keith Bostic.  All rights reserved.
+ *
+ * See the LICENSE file for redistribution information.
+ */
+
+#include "config.h"
+
+#ifndef lint
+static const char sccsid[] = "@(#)ex_undo.c	10.6 (Berkeley) 3/6/96";
+#endif /* not lint */
+
+#include <sys/types.h>
+#include <sys/queue.h>
+
+#include <bitstring.h>
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "../common/common.h"
+
+/*
+ * ex_undo -- u
+ *	Undo the last change.
+ *
+ * PUBLIC: int ex_undo __P((SCR *, EXCMD *));
+ */
+int
+ex_undo(sp, cmdp)
+	SCR *sp;
+	EXCMD *cmdp;
+{
+	EXF *ep;
+	MARK m;
+
+	/*
+	 * !!!
+	 * Historic undo always set the previous context mark.
+	 */
+	m.lno = sp->lno;
+	m.cno = sp->cno;
+	if (mark_set(sp, ABSMARK1, &m, 1))
+		return (1);
+
+	/*
+	 * !!!
+	 * Multiple undo isn't available in ex, as there's no '.' command.
+	 * Whether 'u' is undo or redo is toggled each time, unless there
+	 * was a change since the last undo, in which case it's an undo.
+	 */
+	ep = sp->ep;
+	if (!F_ISSET(ep, F_UNDO)) {
+		F_SET(ep, F_UNDO);
+		ep->lundo = FORWARD;
+	}
+	switch (ep->lundo) {
+	case BACKWARD:
+		if (log_forward(sp, &m))
+			return (1);
+		ep->lundo = FORWARD;
+		break;
+	case FORWARD:
+		if (log_backward(sp, &m))
+			return (1);
+		ep->lundo = BACKWARD;
+		break;
+	case NOTSET:
+		abort();
+	}
+	sp->lno = m.lno;
+	sp->cno = m.cno;
+	return (0);
+}