xref: /vim-8.2.3635/src/undo.c (revision cd5c8f82)
1 /* vi:set ts=8 sts=4 sw=4 noet:
2  *
3  * VIM - Vi IMproved	by Bram Moolenaar
4  *
5  * Do ":help uganda"  in Vim to read copying and usage conditions.
6  * Do ":help credits" in Vim to see a list of people who contributed.
7  * See README.txt for an overview of the Vim source code.
8  */
9 
10 /*
11  * undo.c: multi level undo facility
12  *
13  * The saved lines are stored in a list of lists (one for each buffer):
14  *
15  * b_u_oldhead------------------------------------------------+
16  *							      |
17  *							      V
18  *		  +--------------+    +--------------+	  +--------------+
19  * b_u_newhead--->| u_header	 |    | u_header     |	  | u_header	 |
20  *		  |	uh_next------>|     uh_next------>|	uh_next---->NULL
21  *	   NULL<--------uh_prev  |<---------uh_prev  |<---------uh_prev  |
22  *		  |	uh_entry |    |     uh_entry |	  |	uh_entry |
23  *		  +--------|-----+    +--------|-----+	  +--------|-----+
24  *			   |		       |		   |
25  *			   V		       V		   V
26  *		  +--------------+    +--------------+	  +--------------+
27  *		  | u_entry	 |    | u_entry      |	  | u_entry	 |
28  *		  |	ue_next  |    |     ue_next  |	  |	ue_next  |
29  *		  +--------|-----+    +--------|-----+	  +--------|-----+
30  *			   |		       |		   |
31  *			   V		       V		   V
32  *		  +--------------+	      NULL		  NULL
33  *		  | u_entry	 |
34  *		  |	ue_next  |
35  *		  +--------|-----+
36  *			   |
37  *			   V
38  *			  etc.
39  *
40  * Each u_entry list contains the information for one undo or redo.
41  * curbuf->b_u_curhead points to the header of the last undo (the next redo),
42  * or is NULL if nothing has been undone (end of the branch).
43  *
44  * For keeping alternate undo/redo branches the uh_alt field is used.  Thus at
45  * each point in the list a branch may appear for an alternate to redo.  The
46  * uh_seq field is numbered sequentially to be able to find a newer or older
47  * branch.
48  *
49  *		   +---------------+	+---------------+
50  * b_u_oldhead --->| u_header	   |	| u_header	|
51  *		   |   uh_alt_next ---->|   uh_alt_next ----> NULL
52  *	   NULL <----- uh_alt_prev |<------ uh_alt_prev |
53  *		   |   uh_prev	   |	|   uh_prev	|
54  *		   +-----|---------+	+-----|---------+
55  *			 |		      |
56  *			 V		      V
57  *		   +---------------+	+---------------+
58  *		   | u_header	   |	| u_header	|
59  *		   |   uh_alt_next |	|   uh_alt_next |
60  * b_u_newhead --->|   uh_alt_prev |	|   uh_alt_prev |
61  *		   |   uh_prev	   |	|   uh_prev	|
62  *		   +-----|---------+	+-----|---------+
63  *			 |		      |
64  *			 V		      V
65  *		       NULL		+---------------+    +---------------+
66  *					| u_header	|    | u_header      |
67  *					|   uh_alt_next ---->|	 uh_alt_next |
68  *					|   uh_alt_prev |<------ uh_alt_prev |
69  *					|   uh_prev	|    |	 uh_prev     |
70  *					+-----|---------+    +-----|---------+
71  *					      |			   |
72  *					     etc.		  etc.
73  *
74  *
75  * All data is allocated and will all be freed when the buffer is unloaded.
76  */
77 
78 /* Uncomment the next line for including the u_check() function.  This warns
79  * for errors in the debug information. */
80 /* #define U_DEBUG 1 */
81 #define UH_MAGIC 0x18dade	/* value for uh_magic when in use */
82 #define UE_MAGIC 0xabc123	/* value for ue_magic when in use */
83 
84 /* Size of buffer used for encryption. */
85 #define CRYPT_BUF_SIZE 8192
86 
87 #include "vim.h"
88 
89 /* Structure passed around between functions.
90  * Avoids passing cryptstate_T when encryption not available. */
91 typedef struct {
92     buf_T	*bi_buf;
93     FILE	*bi_fp;
94 #ifdef FEAT_CRYPT
95     cryptstate_T *bi_state;
96     char_u	*bi_buffer; /* CRYPT_BUF_SIZE, NULL when not buffering */
97     size_t	bi_used;    /* bytes written to/read from bi_buffer */
98     size_t	bi_avail;   /* bytes available in bi_buffer */
99 #endif
100 } bufinfo_T;
101 
102 
103 static long get_undolevel(void);
104 static void u_unch_branch(u_header_T *uhp);
105 static u_entry_T *u_get_headentry(void);
106 static void u_getbot(void);
107 static void u_doit(int count);
108 static void u_undoredo(int undo);
109 static void u_undo_end(int did_undo, int absolute);
110 static void u_add_time(char_u *buf, size_t buflen, time_t tt);
111 static void u_freeheader(buf_T *buf, u_header_T *uhp, u_header_T **uhpp);
112 static void u_freebranch(buf_T *buf, u_header_T *uhp, u_header_T **uhpp);
113 static void u_freeentries(buf_T *buf, u_header_T *uhp, u_header_T **uhpp);
114 static void u_freeentry(u_entry_T *, long);
115 #ifdef FEAT_PERSISTENT_UNDO
116 static void corruption_error(char *mesg, char_u *file_name);
117 static void u_free_uhp(u_header_T *uhp);
118 static int undo_write(bufinfo_T *bi, char_u *ptr, size_t len);
119 # ifdef FEAT_CRYPT
120 static int undo_flush(bufinfo_T *bi);
121 # endif
122 static int fwrite_crypt(bufinfo_T *bi, char_u *ptr, size_t len);
123 static int undo_write_bytes(bufinfo_T *bi, long_u nr, int len);
124 static void put_header_ptr(bufinfo_T *bi, u_header_T *uhp);
125 static int undo_read_4c(bufinfo_T *bi);
126 static int undo_read_2c(bufinfo_T *bi);
127 static int undo_read_byte(bufinfo_T *bi);
128 static time_t undo_read_time(bufinfo_T *bi);
129 static int undo_read(bufinfo_T *bi, char_u *buffer, size_t size);
130 static char_u *read_string_decrypt(bufinfo_T *bi, int len);
131 static int serialize_header(bufinfo_T *bi, char_u *hash);
132 static int serialize_uhp(bufinfo_T *bi, u_header_T *uhp);
133 static u_header_T *unserialize_uhp(bufinfo_T *bi, char_u *file_name);
134 static int serialize_uep(bufinfo_T *bi, u_entry_T *uep);
135 static u_entry_T *unserialize_uep(bufinfo_T *bi, int *error, char_u *file_name);
136 static void serialize_pos(bufinfo_T *bi, pos_T pos);
137 static void unserialize_pos(bufinfo_T *bi, pos_T *pos);
138 static void serialize_visualinfo(bufinfo_T *bi, visualinfo_T *info);
139 static void unserialize_visualinfo(bufinfo_T *bi, visualinfo_T *info);
140 #endif
141 
142 #define U_ALLOC_LINE(size) lalloc((long_u)(size), FALSE)
143 static char_u *u_save_line(linenr_T);
144 
145 /* used in undo_end() to report number of added and deleted lines */
146 static long	u_newcount, u_oldcount;
147 
148 /*
149  * When 'u' flag included in 'cpoptions', we behave like vi.  Need to remember
150  * the action that "u" should do.
151  */
152 static int	undo_undoes = FALSE;
153 
154 static int	lastmark = 0;
155 
156 #if defined(U_DEBUG) || defined(PROTO)
157 /*
158  * Check the undo structures for being valid.  Print a warning when something
159  * looks wrong.
160  */
161 static int seen_b_u_curhead;
162 static int seen_b_u_newhead;
163 static int header_count;
164 
165     static void
166 u_check_tree(u_header_T *uhp,
167 	u_header_T *exp_uh_next,
168 	u_header_T *exp_uh_alt_prev)
169 {
170     u_entry_T *uep;
171 
172     if (uhp == NULL)
173 	return;
174     ++header_count;
175     if (uhp == curbuf->b_u_curhead && ++seen_b_u_curhead > 1)
176     {
177 	EMSG("b_u_curhead found twice (looping?)");
178 	return;
179     }
180     if (uhp == curbuf->b_u_newhead && ++seen_b_u_newhead > 1)
181     {
182 	EMSG("b_u_newhead found twice (looping?)");
183 	return;
184     }
185 
186     if (uhp->uh_magic != UH_MAGIC)
187 	EMSG("uh_magic wrong (may be using freed memory)");
188     else
189     {
190 	/* Check pointers back are correct. */
191 	if (uhp->uh_next.ptr != exp_uh_next)
192 	{
193 	    EMSG("uh_next wrong");
194 	    smsg((char_u *)"expected: 0x%x, actual: 0x%x",
195 					       exp_uh_next, uhp->uh_next.ptr);
196 	}
197 	if (uhp->uh_alt_prev.ptr != exp_uh_alt_prev)
198 	{
199 	    EMSG("uh_alt_prev wrong");
200 	    smsg((char_u *)"expected: 0x%x, actual: 0x%x",
201 				       exp_uh_alt_prev, uhp->uh_alt_prev.ptr);
202 	}
203 
204 	/* Check the undo tree at this header. */
205 	for (uep = uhp->uh_entry; uep != NULL; uep = uep->ue_next)
206 	{
207 	    if (uep->ue_magic != UE_MAGIC)
208 	    {
209 		EMSG("ue_magic wrong (may be using freed memory)");
210 		break;
211 	    }
212 	}
213 
214 	/* Check the next alt tree. */
215 	u_check_tree(uhp->uh_alt_next.ptr, uhp->uh_next.ptr, uhp);
216 
217 	/* Check the next header in this branch. */
218 	u_check_tree(uhp->uh_prev.ptr, uhp, NULL);
219     }
220 }
221 
222     static void
223 u_check(int newhead_may_be_NULL)
224 {
225     seen_b_u_newhead = 0;
226     seen_b_u_curhead = 0;
227     header_count = 0;
228 
229     u_check_tree(curbuf->b_u_oldhead, NULL, NULL);
230 
231     if (seen_b_u_newhead == 0 && curbuf->b_u_oldhead != NULL
232 	    && !(newhead_may_be_NULL && curbuf->b_u_newhead == NULL))
233 	EMSGN("b_u_newhead invalid: 0x%x", curbuf->b_u_newhead);
234     if (curbuf->b_u_curhead != NULL && seen_b_u_curhead == 0)
235 	EMSGN("b_u_curhead invalid: 0x%x", curbuf->b_u_curhead);
236     if (header_count != curbuf->b_u_numhead)
237     {
238 	EMSG("b_u_numhead invalid");
239 	smsg((char_u *)"expected: %ld, actual: %ld",
240 			       (long)header_count, (long)curbuf->b_u_numhead);
241     }
242 }
243 #endif
244 
245 /*
246  * Save the current line for both the "u" and "U" command.
247  * Careful: may trigger autocommands that reload the buffer.
248  * Returns OK or FAIL.
249  */
250     int
251 u_save_cursor(void)
252 {
253     return (u_save((linenr_T)(curwin->w_cursor.lnum - 1),
254 				      (linenr_T)(curwin->w_cursor.lnum + 1)));
255 }
256 
257 /*
258  * Save the lines between "top" and "bot" for both the "u" and "U" command.
259  * "top" may be 0 and bot may be curbuf->b_ml.ml_line_count + 1.
260  * Careful: may trigger autocommands that reload the buffer.
261  * Returns FAIL when lines could not be saved, OK otherwise.
262  */
263     int
264 u_save(linenr_T top, linenr_T bot)
265 {
266     if (undo_off)
267 	return OK;
268 
269     if (top > curbuf->b_ml.ml_line_count
270 	    || top >= bot
271 	    || bot > curbuf->b_ml.ml_line_count + 1)
272 	return FALSE;	/* rely on caller to do error messages */
273 
274     if (top + 2 == bot)
275 	u_saveline((linenr_T)(top + 1));
276 
277     return (u_savecommon(top, bot, (linenr_T)0, FALSE));
278 }
279 
280 /*
281  * Save the line "lnum" (used by ":s" and "~" command).
282  * The line is replaced, so the new bottom line is lnum + 1.
283  * Careful: may trigger autocommands that reload the buffer.
284  * Returns FAIL when lines could not be saved, OK otherwise.
285  */
286     int
287 u_savesub(linenr_T lnum)
288 {
289     if (undo_off)
290 	return OK;
291 
292     return (u_savecommon(lnum - 1, lnum + 1, lnum + 1, FALSE));
293 }
294 
295 /*
296  * A new line is inserted before line "lnum" (used by :s command).
297  * The line is inserted, so the new bottom line is lnum + 1.
298  * Careful: may trigger autocommands that reload the buffer.
299  * Returns FAIL when lines could not be saved, OK otherwise.
300  */
301     int
302 u_inssub(linenr_T lnum)
303 {
304     if (undo_off)
305 	return OK;
306 
307     return (u_savecommon(lnum - 1, lnum, lnum + 1, FALSE));
308 }
309 
310 /*
311  * Save the lines "lnum" - "lnum" + nlines (used by delete command).
312  * The lines are deleted, so the new bottom line is lnum, unless the buffer
313  * becomes empty.
314  * Careful: may trigger autocommands that reload the buffer.
315  * Returns FAIL when lines could not be saved, OK otherwise.
316  */
317     int
318 u_savedel(linenr_T lnum, long nlines)
319 {
320     if (undo_off)
321 	return OK;
322 
323     return (u_savecommon(lnum - 1, lnum + nlines,
324 		     nlines == curbuf->b_ml.ml_line_count ? 2 : lnum, FALSE));
325 }
326 
327 /*
328  * Return TRUE when undo is allowed.  Otherwise give an error message and
329  * return FALSE.
330  */
331     int
332 undo_allowed(void)
333 {
334     /* Don't allow changes when 'modifiable' is off.  */
335     if (!curbuf->b_p_ma)
336     {
337 	EMSG(_(e_modifiable));
338 	return FALSE;
339     }
340 
341 #ifdef HAVE_SANDBOX
342     /* In the sandbox it's not allowed to change the text. */
343     if (sandbox != 0)
344     {
345 	EMSG(_(e_sandbox));
346 	return FALSE;
347     }
348 #endif
349 
350     /* Don't allow changes in the buffer while editing the cmdline.  The
351      * caller of getcmdline() may get confused. */
352     if (textlock != 0)
353     {
354 	EMSG(_(e_secure));
355 	return FALSE;
356     }
357 
358     return TRUE;
359 }
360 
361 /*
362  * Get the undolevle value for the current buffer.
363  */
364     static long
365 get_undolevel(void)
366 {
367     if (curbuf->b_p_ul == NO_LOCAL_UNDOLEVEL)
368 	return p_ul;
369     return curbuf->b_p_ul;
370 }
371 
372 /*
373  * Common code for various ways to save text before a change.
374  * "top" is the line above the first changed line.
375  * "bot" is the line below the last changed line.
376  * "newbot" is the new bottom line.  Use zero when not known.
377  * "reload" is TRUE when saving for a buffer reload.
378  * Careful: may trigger autocommands that reload the buffer.
379  * Returns FAIL when lines could not be saved, OK otherwise.
380  */
381     int
382 u_savecommon(
383     linenr_T	top,
384     linenr_T	bot,
385     linenr_T	newbot,
386     int		reload)
387 {
388     linenr_T	lnum;
389     long	i;
390     u_header_T	*uhp;
391     u_header_T	*old_curhead;
392     u_entry_T	*uep;
393     u_entry_T	*prev_uep;
394     long	size;
395 
396     if (!reload)
397     {
398 	/* When making changes is not allowed return FAIL.  It's a crude way
399 	 * to make all change commands fail. */
400 	if (!undo_allowed())
401 	    return FAIL;
402 
403 #ifdef FEAT_NETBEANS_INTG
404 	/*
405 	 * Netbeans defines areas that cannot be modified.  Bail out here when
406 	 * trying to change text in a guarded area.
407 	 */
408 	if (netbeans_active())
409 	{
410 	    if (netbeans_is_guarded(top, bot))
411 	    {
412 		EMSG(_(e_guarded));
413 		return FAIL;
414 	    }
415 	    if (curbuf->b_p_ro)
416 	    {
417 		EMSG(_(e_nbreadonly));
418 		return FAIL;
419 	    }
420 	}
421 #endif
422 
423 #ifdef FEAT_AUTOCMD
424 	/*
425 	 * Saving text for undo means we are going to make a change.  Give a
426 	 * warning for a read-only file before making the change, so that the
427 	 * FileChangedRO event can replace the buffer with a read-write version
428 	 * (e.g., obtained from a source control system).
429 	 */
430 	change_warning(0);
431 	if (bot > curbuf->b_ml.ml_line_count + 1)
432 	{
433 	    /* This happens when the FileChangedRO autocommand changes the
434 	     * file in a way it becomes shorter. */
435 	    EMSG(_("E881: Line count changed unexpectedly"));
436 	    return FAIL;
437 	}
438 #endif
439     }
440 
441 #ifdef U_DEBUG
442     u_check(FALSE);
443 #endif
444 
445     size = bot - top - 1;
446 
447     /*
448      * If curbuf->b_u_synced == TRUE make a new header.
449      */
450     if (curbuf->b_u_synced)
451     {
452 #ifdef FEAT_JUMPLIST
453 	/* Need to create new entry in b_changelist. */
454 	curbuf->b_new_change = TRUE;
455 #endif
456 
457 	if (get_undolevel() >= 0)
458 	{
459 	    /*
460 	     * Make a new header entry.  Do this first so that we don't mess
461 	     * up the undo info when out of memory.
462 	     */
463 	    uhp = (u_header_T *)U_ALLOC_LINE(sizeof(u_header_T));
464 	    if (uhp == NULL)
465 		goto nomem;
466 #ifdef U_DEBUG
467 	    uhp->uh_magic = UH_MAGIC;
468 #endif
469 	}
470 	else
471 	    uhp = NULL;
472 
473 	/*
474 	 * If we undid more than we redid, move the entry lists before and
475 	 * including curbuf->b_u_curhead to an alternate branch.
476 	 */
477 	old_curhead = curbuf->b_u_curhead;
478 	if (old_curhead != NULL)
479 	{
480 	    curbuf->b_u_newhead = old_curhead->uh_next.ptr;
481 	    curbuf->b_u_curhead = NULL;
482 	}
483 
484 	/*
485 	 * free headers to keep the size right
486 	 */
487 	while (curbuf->b_u_numhead > get_undolevel()
488 					       && curbuf->b_u_oldhead != NULL)
489 	{
490 	    u_header_T	    *uhfree = curbuf->b_u_oldhead;
491 
492 	    if (uhfree == old_curhead)
493 		/* Can't reconnect the branch, delete all of it. */
494 		u_freebranch(curbuf, uhfree, &old_curhead);
495 	    else if (uhfree->uh_alt_next.ptr == NULL)
496 		/* There is no branch, only free one header. */
497 		u_freeheader(curbuf, uhfree, &old_curhead);
498 	    else
499 	    {
500 		/* Free the oldest alternate branch as a whole. */
501 		while (uhfree->uh_alt_next.ptr != NULL)
502 		    uhfree = uhfree->uh_alt_next.ptr;
503 		u_freebranch(curbuf, uhfree, &old_curhead);
504 	    }
505 #ifdef U_DEBUG
506 	    u_check(TRUE);
507 #endif
508 	}
509 
510 	if (uhp == NULL)		/* no undo at all */
511 	{
512 	    if (old_curhead != NULL)
513 		u_freebranch(curbuf, old_curhead, NULL);
514 	    curbuf->b_u_synced = FALSE;
515 	    return OK;
516 	}
517 
518 	uhp->uh_prev.ptr = NULL;
519 	uhp->uh_next.ptr = curbuf->b_u_newhead;
520 	uhp->uh_alt_next.ptr = old_curhead;
521 	if (old_curhead != NULL)
522 	{
523 	    uhp->uh_alt_prev.ptr = old_curhead->uh_alt_prev.ptr;
524 	    if (uhp->uh_alt_prev.ptr != NULL)
525 		uhp->uh_alt_prev.ptr->uh_alt_next.ptr = uhp;
526 	    old_curhead->uh_alt_prev.ptr = uhp;
527 	    if (curbuf->b_u_oldhead == old_curhead)
528 		curbuf->b_u_oldhead = uhp;
529 	}
530 	else
531 	    uhp->uh_alt_prev.ptr = NULL;
532 	if (curbuf->b_u_newhead != NULL)
533 	    curbuf->b_u_newhead->uh_prev.ptr = uhp;
534 
535 	uhp->uh_seq = ++curbuf->b_u_seq_last;
536 	curbuf->b_u_seq_cur = uhp->uh_seq;
537 	uhp->uh_time = vim_time();
538 	uhp->uh_save_nr = 0;
539 	curbuf->b_u_time_cur = uhp->uh_time + 1;
540 
541 	uhp->uh_walk = 0;
542 	uhp->uh_entry = NULL;
543 	uhp->uh_getbot_entry = NULL;
544 	uhp->uh_cursor = curwin->w_cursor;	/* save cursor pos. for undo */
545 #ifdef FEAT_VIRTUALEDIT
546 	if (virtual_active() && curwin->w_cursor.coladd > 0)
547 	    uhp->uh_cursor_vcol = getviscol();
548 	else
549 	    uhp->uh_cursor_vcol = -1;
550 #endif
551 
552 	/* save changed and buffer empty flag for undo */
553 	uhp->uh_flags = (curbuf->b_changed ? UH_CHANGED : 0) +
554 		       ((curbuf->b_ml.ml_flags & ML_EMPTY) ? UH_EMPTYBUF : 0);
555 
556 	/* save named marks and Visual marks for undo */
557 	mch_memmove(uhp->uh_namedm, curbuf->b_namedm, sizeof(pos_T) * NMARKS);
558 	uhp->uh_visual = curbuf->b_visual;
559 
560 	curbuf->b_u_newhead = uhp;
561 	if (curbuf->b_u_oldhead == NULL)
562 	    curbuf->b_u_oldhead = uhp;
563 	++curbuf->b_u_numhead;
564     }
565     else
566     {
567 	if (get_undolevel() < 0)	/* no undo at all */
568 	    return OK;
569 
570 	/*
571 	 * When saving a single line, and it has been saved just before, it
572 	 * doesn't make sense saving it again.  Saves a lot of memory when
573 	 * making lots of changes inside the same line.
574 	 * This is only possible if the previous change didn't increase or
575 	 * decrease the number of lines.
576 	 * Check the ten last changes.  More doesn't make sense and takes too
577 	 * long.
578 	 */
579 	if (size == 1)
580 	{
581 	    uep = u_get_headentry();
582 	    prev_uep = NULL;
583 	    for (i = 0; i < 10; ++i)
584 	    {
585 		if (uep == NULL)
586 		    break;
587 
588 		/* If lines have been inserted/deleted we give up.
589 		 * Also when the line was included in a multi-line save. */
590 		if ((curbuf->b_u_newhead->uh_getbot_entry != uep
591 			    ? (uep->ue_top + uep->ue_size + 1
592 				!= (uep->ue_bot == 0
593 				    ? curbuf->b_ml.ml_line_count + 1
594 				    : uep->ue_bot))
595 			    : uep->ue_lcount != curbuf->b_ml.ml_line_count)
596 			|| (uep->ue_size > 1
597 			    && top >= uep->ue_top
598 			    && top + 2 <= uep->ue_top + uep->ue_size + 1))
599 		    break;
600 
601 		/* If it's the same line we can skip saving it again. */
602 		if (uep->ue_size == 1 && uep->ue_top == top)
603 		{
604 		    if (i > 0)
605 		    {
606 			/* It's not the last entry: get ue_bot for the last
607 			 * entry now.  Following deleted/inserted lines go to
608 			 * the re-used entry. */
609 			u_getbot();
610 			curbuf->b_u_synced = FALSE;
611 
612 			/* Move the found entry to become the last entry.  The
613 			 * order of undo/redo doesn't matter for the entries
614 			 * we move it over, since they don't change the line
615 			 * count and don't include this line.  It does matter
616 			 * for the found entry if the line count is changed by
617 			 * the executed command. */
618 			prev_uep->ue_next = uep->ue_next;
619 			uep->ue_next = curbuf->b_u_newhead->uh_entry;
620 			curbuf->b_u_newhead->uh_entry = uep;
621 		    }
622 
623 		    /* The executed command may change the line count. */
624 		    if (newbot != 0)
625 			uep->ue_bot = newbot;
626 		    else if (bot > curbuf->b_ml.ml_line_count)
627 			uep->ue_bot = 0;
628 		    else
629 		    {
630 			uep->ue_lcount = curbuf->b_ml.ml_line_count;
631 			curbuf->b_u_newhead->uh_getbot_entry = uep;
632 		    }
633 		    return OK;
634 		}
635 		prev_uep = uep;
636 		uep = uep->ue_next;
637 	    }
638 	}
639 
640 	/* find line number for ue_bot for previous u_save() */
641 	u_getbot();
642     }
643 
644 #if !defined(UNIX) && !defined(WIN32)
645 	/*
646 	 * With Amiga we can't handle big undo's, because
647 	 * then u_alloc_line would have to allocate a block larger than 32K
648 	 */
649     if (size >= 8000)
650 	goto nomem;
651 #endif
652 
653     /*
654      * add lines in front of entry list
655      */
656     uep = (u_entry_T *)U_ALLOC_LINE(sizeof(u_entry_T));
657     if (uep == NULL)
658 	goto nomem;
659     vim_memset(uep, 0, sizeof(u_entry_T));
660 #ifdef U_DEBUG
661     uep->ue_magic = UE_MAGIC;
662 #endif
663 
664     uep->ue_size = size;
665     uep->ue_top = top;
666     if (newbot != 0)
667 	uep->ue_bot = newbot;
668     /*
669      * Use 0 for ue_bot if bot is below last line.
670      * Otherwise we have to compute ue_bot later.
671      */
672     else if (bot > curbuf->b_ml.ml_line_count)
673 	uep->ue_bot = 0;
674     else
675     {
676 	uep->ue_lcount = curbuf->b_ml.ml_line_count;
677 	curbuf->b_u_newhead->uh_getbot_entry = uep;
678     }
679 
680     if (size > 0)
681     {
682 	if ((uep->ue_array = (char_u **)U_ALLOC_LINE(
683 					    sizeof(char_u *) * size)) == NULL)
684 	{
685 	    u_freeentry(uep, 0L);
686 	    goto nomem;
687 	}
688 	for (i = 0, lnum = top + 1; i < size; ++i)
689 	{
690 	    fast_breakcheck();
691 	    if (got_int)
692 	    {
693 		u_freeentry(uep, i);
694 		return FAIL;
695 	    }
696 	    if ((uep->ue_array[i] = u_save_line(lnum++)) == NULL)
697 	    {
698 		u_freeentry(uep, i);
699 		goto nomem;
700 	    }
701 	}
702     }
703     else
704 	uep->ue_array = NULL;
705     uep->ue_next = curbuf->b_u_newhead->uh_entry;
706     curbuf->b_u_newhead->uh_entry = uep;
707     curbuf->b_u_synced = FALSE;
708     undo_undoes = FALSE;
709 
710 #ifdef U_DEBUG
711     u_check(FALSE);
712 #endif
713     return OK;
714 
715 nomem:
716     msg_silent = 0;	/* must display the prompt */
717     if (ask_yesno((char_u *)_("No undo possible; continue anyway"), TRUE)
718 								       == 'y')
719     {
720 	undo_off = TRUE;	    /* will be reset when character typed */
721 	return OK;
722     }
723     do_outofmem_msg((long_u)0);
724     return FAIL;
725 }
726 
727 #if defined(FEAT_PERSISTENT_UNDO) || defined(PROTO)
728 
729 # define UF_START_MAGIC	    "Vim\237UnDo\345"  /* magic at start of undofile */
730 # define UF_START_MAGIC_LEN	9
731 # define UF_HEADER_MAGIC	0x5fd0	/* magic at start of header */
732 # define UF_HEADER_END_MAGIC	0xe7aa	/* magic after last header */
733 # define UF_ENTRY_MAGIC		0xf518	/* magic at start of entry */
734 # define UF_ENTRY_END_MAGIC	0x3581	/* magic after last entry */
735 # define UF_VERSION		2	/* 2-byte undofile version number */
736 # define UF_VERSION_CRYPT	0x8002	/* idem, encrypted */
737 
738 /* extra fields for header */
739 # define UF_LAST_SAVE_NR	1
740 
741 /* extra fields for uhp */
742 # define UHP_SAVE_NR		1
743 
744 static char_u e_not_open[] = N_("E828: Cannot open undo file for writing: %s");
745 
746 /*
747  * Compute the hash for the current buffer text into hash[UNDO_HASH_SIZE].
748  */
749     void
750 u_compute_hash(char_u *hash)
751 {
752     context_sha256_T	ctx;
753     linenr_T		lnum;
754     char_u		*p;
755 
756     sha256_start(&ctx);
757     for (lnum = 1; lnum <= curbuf->b_ml.ml_line_count; ++lnum)
758     {
759 	p = ml_get(lnum);
760 	sha256_update(&ctx, p, (UINT32_T)(STRLEN(p) + 1));
761     }
762     sha256_finish(&ctx, hash);
763 }
764 
765 /*
766  * Return an allocated string of the full path of the target undofile.
767  * When "reading" is TRUE find the file to read, go over all directories in
768  * 'undodir'.
769  * When "reading" is FALSE use the first name where the directory exists.
770  * Returns NULL when there is no place to write or no file to read.
771  */
772     char_u *
773 u_get_undo_file_name(char_u *buf_ffname, int reading)
774 {
775     char_u	*dirp;
776     char_u	dir_name[IOSIZE + 1];
777     char_u	*munged_name = NULL;
778     char_u	*undo_file_name = NULL;
779     int		dir_len;
780     char_u	*p;
781     stat_T	st;
782     char_u	*ffname = buf_ffname;
783 #ifdef HAVE_READLINK
784     char_u	fname_buf[MAXPATHL];
785 #endif
786 
787     if (ffname == NULL)
788 	return NULL;
789 
790 #ifdef HAVE_READLINK
791     /* Expand symlink in the file name, so that we put the undo file with the
792      * actual file instead of with the symlink. */
793     if (resolve_symlink(ffname, fname_buf) == OK)
794 	ffname = fname_buf;
795 #endif
796 
797     /* Loop over 'undodir'.  When reading find the first file that exists.
798      * When not reading use the first directory that exists or ".". */
799     dirp = p_udir;
800     while (*dirp != NUL)
801     {
802 	dir_len = copy_option_part(&dirp, dir_name, IOSIZE, ",");
803 	if (dir_len == 1 && dir_name[0] == '.')
804 	{
805 	    /* Use same directory as the ffname,
806 	     * "dir/name" -> "dir/.name.un~" */
807 	    undo_file_name = vim_strnsave(ffname, (int)(STRLEN(ffname) + 5));
808 	    if (undo_file_name == NULL)
809 		break;
810 	    p = gettail(undo_file_name);
811 #ifdef VMS
812 	    /* VMS can not handle more than one dot in the filenames
813 	     * use "dir/name" -> "dir/_un_name" - add _un_
814 	     * at the beginning to keep the extension */
815 	    mch_memmove(p + 4,  p, STRLEN(p) + 1);
816 	    mch_memmove(p, "_un_", 4);
817 
818 #else
819 	    /* Use same directory as the ffname,
820 	     * "dir/name" -> "dir/.name.un~" */
821 	    mch_memmove(p + 1, p, STRLEN(p) + 1);
822 	    *p = '.';
823 	    STRCAT(p, ".un~");
824 #endif
825 	}
826 	else
827 	{
828 	    dir_name[dir_len] = NUL;
829 	    if (mch_isdir(dir_name))
830 	    {
831 		if (munged_name == NULL)
832 		{
833 		    munged_name = vim_strsave(ffname);
834 		    if (munged_name == NULL)
835 			return NULL;
836 		    for (p = munged_name; *p != NUL; MB_PTR_ADV(p))
837 			if (vim_ispathsep(*p))
838 			    *p = '%';
839 		}
840 		undo_file_name = concat_fnames(dir_name, munged_name, TRUE);
841 	    }
842 	}
843 
844 	/* When reading check if the file exists. */
845 	if (undo_file_name != NULL && (!reading
846 			       || mch_stat((char *)undo_file_name, &st) >= 0))
847 	    break;
848 	vim_free(undo_file_name);
849 	undo_file_name = NULL;
850     }
851 
852     vim_free(munged_name);
853     return undo_file_name;
854 }
855 
856     static void
857 corruption_error(char *mesg, char_u *file_name)
858 {
859     EMSG3(_("E825: Corrupted undo file (%s): %s"), mesg, file_name);
860 }
861 
862     static void
863 u_free_uhp(u_header_T *uhp)
864 {
865     u_entry_T	*nuep;
866     u_entry_T	*uep;
867 
868     uep = uhp->uh_entry;
869     while (uep != NULL)
870     {
871 	nuep = uep->ue_next;
872 	u_freeentry(uep, uep->ue_size);
873 	uep = nuep;
874     }
875     vim_free(uhp);
876 }
877 
878 /*
879  * Write a sequence of bytes to the undo file.
880  * Buffers and encrypts as needed.
881  * Returns OK or FAIL.
882  */
883     static int
884 undo_write(bufinfo_T *bi, char_u *ptr, size_t len)
885 {
886 #ifdef FEAT_CRYPT
887     if (bi->bi_buffer != NULL)
888     {
889 	size_t	len_todo = len;
890 	char_u  *p = ptr;
891 
892 	while (bi->bi_used + len_todo >= CRYPT_BUF_SIZE)
893 	{
894 	    size_t	n = CRYPT_BUF_SIZE - bi->bi_used;
895 
896 	    mch_memmove(bi->bi_buffer + bi->bi_used, p, n);
897 	    len_todo -= n;
898 	    p += n;
899 	    bi->bi_used = CRYPT_BUF_SIZE;
900 	    if (undo_flush(bi) == FAIL)
901 		return FAIL;
902 	}
903 	if (len_todo > 0)
904 	{
905 	    mch_memmove(bi->bi_buffer + bi->bi_used, p, len_todo);
906 	    bi->bi_used += len_todo;
907 	}
908 	return OK;
909     }
910 #endif
911     if (fwrite(ptr, len, (size_t)1, bi->bi_fp) != 1)
912 	return FAIL;
913     return OK;
914 }
915 
916 #ifdef FEAT_CRYPT
917     static int
918 undo_flush(bufinfo_T *bi)
919 {
920     if (bi->bi_buffer != NULL && bi->bi_used > 0)
921     {
922 	crypt_encode_inplace(bi->bi_state, bi->bi_buffer, bi->bi_used);
923 	if (fwrite(bi->bi_buffer, bi->bi_used, (size_t)1, bi->bi_fp) != 1)
924 	    return FAIL;
925 	bi->bi_used = 0;
926     }
927     return OK;
928 }
929 #endif
930 
931 /*
932  * Write "ptr[len]" and crypt the bytes when needed.
933  * Returns OK or FAIL.
934  */
935     static int
936 fwrite_crypt(bufinfo_T *bi, char_u *ptr, size_t len)
937 {
938 #ifdef FEAT_CRYPT
939     char_u  *copy;
940     char_u  small_buf[100];
941     size_t  i;
942 
943     if (bi->bi_state != NULL && bi->bi_buffer == NULL)
944     {
945 	/* crypting every piece of text separately */
946 	if (len < 100)
947 	    copy = small_buf;  /* no malloc()/free() for short strings */
948 	else
949 	{
950 	    copy = lalloc(len, FALSE);
951 	    if (copy == NULL)
952 		return 0;
953 	}
954 	crypt_encode(bi->bi_state, ptr, len, copy);
955 	i = fwrite(copy, len, (size_t)1, bi->bi_fp);
956 	if (copy != small_buf)
957 	    vim_free(copy);
958 	return i == 1 ? OK : FAIL;
959     }
960 #endif
961     return undo_write(bi, ptr, len);
962 }
963 
964 /*
965  * Write a number, MSB first, in "len" bytes.
966  * Must match with undo_read_?c() functions.
967  * Returns OK or FAIL.
968  */
969     static int
970 undo_write_bytes(bufinfo_T *bi, long_u nr, int len)
971 {
972     char_u  buf[8];
973     int	    i;
974     int	    bufi = 0;
975 
976     for (i = len - 1; i >= 0; --i)
977 	buf[bufi++] = (char_u)(nr >> (i * 8));
978     return undo_write(bi, buf, (size_t)len);
979 }
980 
981 /*
982  * Write the pointer to an undo header.  Instead of writing the pointer itself
983  * we use the sequence number of the header.  This is converted back to
984  * pointers when reading. */
985     static void
986 put_header_ptr(bufinfo_T *bi, u_header_T *uhp)
987 {
988     undo_write_bytes(bi, (long_u)(uhp != NULL ? uhp->uh_seq : 0), 4);
989 }
990 
991     static int
992 undo_read_4c(bufinfo_T *bi)
993 {
994 #ifdef FEAT_CRYPT
995     if (bi->bi_buffer != NULL)
996     {
997 	char_u  buf[4];
998 	int	n;
999 
1000 	undo_read(bi, buf, (size_t)4);
1001 	n = ((unsigned)buf[0] << 24) + (buf[1] << 16) + (buf[2] << 8) + buf[3];
1002 	return n;
1003     }
1004 #endif
1005     return get4c(bi->bi_fp);
1006 }
1007 
1008     static int
1009 undo_read_2c(bufinfo_T *bi)
1010 {
1011 #ifdef FEAT_CRYPT
1012     if (bi->bi_buffer != NULL)
1013     {
1014 	char_u  buf[2];
1015 	int	n;
1016 
1017 	undo_read(bi, buf, (size_t)2);
1018 	n = (buf[0] << 8) + buf[1];
1019 	return n;
1020     }
1021 #endif
1022     return get2c(bi->bi_fp);
1023 }
1024 
1025     static int
1026 undo_read_byte(bufinfo_T *bi)
1027 {
1028 #ifdef FEAT_CRYPT
1029     if (bi->bi_buffer != NULL)
1030     {
1031 	char_u  buf[1];
1032 
1033 	undo_read(bi, buf, (size_t)1);
1034 	return buf[0];
1035     }
1036 #endif
1037     return getc(bi->bi_fp);
1038 }
1039 
1040     static time_t
1041 undo_read_time(bufinfo_T *bi)
1042 {
1043 #ifdef FEAT_CRYPT
1044     if (bi->bi_buffer != NULL)
1045     {
1046 	char_u  buf[8];
1047 	time_t	n = 0;
1048 	int	i;
1049 
1050 	undo_read(bi, buf, (size_t)8);
1051 	for (i = 0; i < 8; ++i)
1052 	    n = (n << 8) + buf[i];
1053 	return n;
1054     }
1055 #endif
1056     return get8ctime(bi->bi_fp);
1057 }
1058 
1059 /*
1060  * Read "buffer[size]" from the undo file.
1061  * Return OK or FAIL.
1062  */
1063     static int
1064 undo_read(bufinfo_T *bi, char_u *buffer, size_t size)
1065 {
1066 #ifdef FEAT_CRYPT
1067     if (bi->bi_buffer != NULL)
1068     {
1069 	int	size_todo = (int)size;
1070 	char_u	*p = buffer;
1071 
1072 	while (size_todo > 0)
1073 	{
1074 	    size_t n;
1075 
1076 	    if (bi->bi_used >= bi->bi_avail)
1077 	    {
1078 		n = fread(bi->bi_buffer, 1, (size_t)CRYPT_BUF_SIZE, bi->bi_fp);
1079 		if (n == 0)
1080 		{
1081 		    /* Error may be checked for only later.  Fill with zeros,
1082 		     * so that the reader won't use garbage. */
1083 		    vim_memset(p, 0, size_todo);
1084 		    return FAIL;
1085 		}
1086 		bi->bi_avail = n;
1087 		bi->bi_used = 0;
1088 		crypt_decode_inplace(bi->bi_state, bi->bi_buffer, bi->bi_avail);
1089 	    }
1090 	    n = size_todo;
1091 	    if (n > bi->bi_avail - bi->bi_used)
1092 		n = bi->bi_avail - bi->bi_used;
1093 	    mch_memmove(p, bi->bi_buffer + bi->bi_used, n);
1094 	    bi->bi_used += n;
1095 	    size_todo -= (int)n;
1096 	    p += n;
1097 	}
1098 	return OK;
1099     }
1100 #endif
1101     if (fread(buffer, (size_t)size, 1, bi->bi_fp) != 1)
1102 	return FAIL;
1103     return OK;
1104 }
1105 
1106 /*
1107  * Read a string of length "len" from "bi->bi_fd".
1108  * "len" can be zero to allocate an empty line.
1109  * Decrypt the bytes if needed.
1110  * Append a NUL.
1111  * Returns a pointer to allocated memory or NULL for failure.
1112  */
1113     static char_u *
1114 read_string_decrypt(bufinfo_T *bi, int len)
1115 {
1116     char_u  *ptr = alloc((unsigned)len + 1);
1117 
1118     if (ptr != NULL)
1119     {
1120 	if (len > 0 && undo_read(bi, ptr, len) == FAIL)
1121 	{
1122 	    vim_free(ptr);
1123 	    return NULL;
1124 	}
1125 	ptr[len] = NUL;
1126 #ifdef FEAT_CRYPT
1127 	if (bi->bi_state != NULL && bi->bi_buffer == NULL)
1128 	    crypt_decode_inplace(bi->bi_state, ptr, len);
1129 #endif
1130     }
1131     return ptr;
1132 }
1133 
1134 /*
1135  * Writes the (not encrypted) header and initializes encryption if needed.
1136  */
1137     static int
1138 serialize_header(bufinfo_T *bi, char_u *hash)
1139 {
1140     int		len;
1141     buf_T	*buf = bi->bi_buf;
1142     FILE	*fp = bi->bi_fp;
1143     char_u	time_buf[8];
1144 
1145     /* Start writing, first the magic marker and undo info version. */
1146     if (fwrite(UF_START_MAGIC, (size_t)UF_START_MAGIC_LEN, (size_t)1, fp) != 1)
1147 	return FAIL;
1148 
1149     /* If the buffer is encrypted then all text bytes following will be
1150      * encrypted.  Numbers and other info is not crypted. */
1151 #ifdef FEAT_CRYPT
1152     if (*buf->b_p_key != NUL)
1153     {
1154 	char_u *header;
1155 	int    header_len;
1156 
1157 	undo_write_bytes(bi, (long_u)UF_VERSION_CRYPT, 2);
1158 	bi->bi_state = crypt_create_for_writing(crypt_get_method_nr(buf),
1159 					  buf->b_p_key, &header, &header_len);
1160 	if (bi->bi_state == NULL)
1161 	    return FAIL;
1162 	len = (int)fwrite(header, (size_t)header_len, (size_t)1, fp);
1163 	vim_free(header);
1164 	if (len != 1)
1165 	{
1166 	    crypt_free_state(bi->bi_state);
1167 	    bi->bi_state = NULL;
1168 	    return FAIL;
1169 	}
1170 
1171 	if (crypt_whole_undofile(crypt_get_method_nr(buf)))
1172 	{
1173 	    bi->bi_buffer = alloc(CRYPT_BUF_SIZE);
1174 	    if (bi->bi_buffer == NULL)
1175 	    {
1176 		crypt_free_state(bi->bi_state);
1177 		bi->bi_state = NULL;
1178 		return FAIL;
1179 	    }
1180 	    bi->bi_used = 0;
1181 	}
1182     }
1183     else
1184 #endif
1185 	undo_write_bytes(bi, (long_u)UF_VERSION, 2);
1186 
1187 
1188     /* Write a hash of the buffer text, so that we can verify it is still the
1189      * same when reading the buffer text. */
1190     if (undo_write(bi, hash, (size_t)UNDO_HASH_SIZE) == FAIL)
1191 	return FAIL;
1192 
1193     /* buffer-specific data */
1194     undo_write_bytes(bi, (long_u)buf->b_ml.ml_line_count, 4);
1195     len = buf->b_u_line_ptr != NULL ? (int)STRLEN(buf->b_u_line_ptr) : 0;
1196     undo_write_bytes(bi, (long_u)len, 4);
1197     if (len > 0 && fwrite_crypt(bi, buf->b_u_line_ptr, (size_t)len) == FAIL)
1198 	return FAIL;
1199     undo_write_bytes(bi, (long_u)buf->b_u_line_lnum, 4);
1200     undo_write_bytes(bi, (long_u)buf->b_u_line_colnr, 4);
1201 
1202     /* Undo structures header data */
1203     put_header_ptr(bi, buf->b_u_oldhead);
1204     put_header_ptr(bi, buf->b_u_newhead);
1205     put_header_ptr(bi, buf->b_u_curhead);
1206 
1207     undo_write_bytes(bi, (long_u)buf->b_u_numhead, 4);
1208     undo_write_bytes(bi, (long_u)buf->b_u_seq_last, 4);
1209     undo_write_bytes(bi, (long_u)buf->b_u_seq_cur, 4);
1210     time_to_bytes(buf->b_u_time_cur, time_buf);
1211     undo_write(bi, time_buf, 8);
1212 
1213     /* Optional fields. */
1214     undo_write_bytes(bi, 4, 1);
1215     undo_write_bytes(bi, UF_LAST_SAVE_NR, 1);
1216     undo_write_bytes(bi, (long_u)buf->b_u_save_nr_last, 4);
1217 
1218     undo_write_bytes(bi, 0, 1);  /* end marker */
1219 
1220     return OK;
1221 }
1222 
1223     static int
1224 serialize_uhp(bufinfo_T *bi, u_header_T *uhp)
1225 {
1226     int		i;
1227     u_entry_T	*uep;
1228     char_u	time_buf[8];
1229 
1230     if (undo_write_bytes(bi, (long_u)UF_HEADER_MAGIC, 2) == FAIL)
1231 	return FAIL;
1232 
1233     put_header_ptr(bi, uhp->uh_next.ptr);
1234     put_header_ptr(bi, uhp->uh_prev.ptr);
1235     put_header_ptr(bi, uhp->uh_alt_next.ptr);
1236     put_header_ptr(bi, uhp->uh_alt_prev.ptr);
1237     undo_write_bytes(bi, uhp->uh_seq, 4);
1238     serialize_pos(bi, uhp->uh_cursor);
1239 #ifdef FEAT_VIRTUALEDIT
1240     undo_write_bytes(bi, (long_u)uhp->uh_cursor_vcol, 4);
1241 #else
1242     undo_write_bytes(bi, (long_u)0, 4);
1243 #endif
1244     undo_write_bytes(bi, (long_u)uhp->uh_flags, 2);
1245     /* Assume NMARKS will stay the same. */
1246     for (i = 0; i < NMARKS; ++i)
1247 	serialize_pos(bi, uhp->uh_namedm[i]);
1248     serialize_visualinfo(bi, &uhp->uh_visual);
1249     time_to_bytes(uhp->uh_time, time_buf);
1250     undo_write(bi, time_buf, 8);
1251 
1252     /* Optional fields. */
1253     undo_write_bytes(bi, 4, 1);
1254     undo_write_bytes(bi, UHP_SAVE_NR, 1);
1255     undo_write_bytes(bi, (long_u)uhp->uh_save_nr, 4);
1256 
1257     undo_write_bytes(bi, 0, 1);  /* end marker */
1258 
1259     /* Write all the entries. */
1260     for (uep = uhp->uh_entry; uep != NULL; uep = uep->ue_next)
1261     {
1262 	undo_write_bytes(bi, (long_u)UF_ENTRY_MAGIC, 2);
1263 	if (serialize_uep(bi, uep) == FAIL)
1264 	    return FAIL;
1265     }
1266     undo_write_bytes(bi, (long_u)UF_ENTRY_END_MAGIC, 2);
1267     return OK;
1268 }
1269 
1270     static u_header_T *
1271 unserialize_uhp(bufinfo_T *bi, char_u *file_name)
1272 {
1273     u_header_T	*uhp;
1274     int		i;
1275     u_entry_T	*uep, *last_uep;
1276     int		c;
1277     int		error;
1278 
1279     uhp = (u_header_T *)U_ALLOC_LINE(sizeof(u_header_T));
1280     if (uhp == NULL)
1281 	return NULL;
1282     vim_memset(uhp, 0, sizeof(u_header_T));
1283 #ifdef U_DEBUG
1284     uhp->uh_magic = UH_MAGIC;
1285 #endif
1286     uhp->uh_next.seq = undo_read_4c(bi);
1287     uhp->uh_prev.seq = undo_read_4c(bi);
1288     uhp->uh_alt_next.seq = undo_read_4c(bi);
1289     uhp->uh_alt_prev.seq = undo_read_4c(bi);
1290     uhp->uh_seq = undo_read_4c(bi);
1291     if (uhp->uh_seq <= 0)
1292     {
1293 	corruption_error("uh_seq", file_name);
1294 	vim_free(uhp);
1295 	return NULL;
1296     }
1297     unserialize_pos(bi, &uhp->uh_cursor);
1298 #ifdef FEAT_VIRTUALEDIT
1299     uhp->uh_cursor_vcol = undo_read_4c(bi);
1300 #else
1301     (void)undo_read_4c(bi);
1302 #endif
1303     uhp->uh_flags = undo_read_2c(bi);
1304     for (i = 0; i < NMARKS; ++i)
1305 	unserialize_pos(bi, &uhp->uh_namedm[i]);
1306     unserialize_visualinfo(bi, &uhp->uh_visual);
1307     uhp->uh_time = undo_read_time(bi);
1308 
1309     /* Optional fields. */
1310     for (;;)
1311     {
1312 	int len = undo_read_byte(bi);
1313 	int what;
1314 
1315 	if (len == 0)
1316 	    break;
1317 	what = undo_read_byte(bi);
1318 	switch (what)
1319 	{
1320 	    case UHP_SAVE_NR:
1321 		uhp->uh_save_nr = undo_read_4c(bi);
1322 		break;
1323 	    default:
1324 		/* field not supported, skip */
1325 		while (--len >= 0)
1326 		    (void)undo_read_byte(bi);
1327 	}
1328     }
1329 
1330     /* Unserialize the uep list. */
1331     last_uep = NULL;
1332     while ((c = undo_read_2c(bi)) == UF_ENTRY_MAGIC)
1333     {
1334 	error = FALSE;
1335 	uep = unserialize_uep(bi, &error, file_name);
1336 	if (last_uep == NULL)
1337 	    uhp->uh_entry = uep;
1338 	else
1339 	    last_uep->ue_next = uep;
1340 	last_uep = uep;
1341 	if (uep == NULL || error)
1342 	{
1343 	    u_free_uhp(uhp);
1344 	    return NULL;
1345 	}
1346     }
1347     if (c != UF_ENTRY_END_MAGIC)
1348     {
1349 	corruption_error("entry end", file_name);
1350 	u_free_uhp(uhp);
1351 	return NULL;
1352     }
1353 
1354     return uhp;
1355 }
1356 
1357 /*
1358  * Serialize "uep".
1359  */
1360     static int
1361 serialize_uep(
1362     bufinfo_T	*bi,
1363     u_entry_T	*uep)
1364 {
1365     int		i;
1366     size_t	len;
1367 
1368     undo_write_bytes(bi, (long_u)uep->ue_top, 4);
1369     undo_write_bytes(bi, (long_u)uep->ue_bot, 4);
1370     undo_write_bytes(bi, (long_u)uep->ue_lcount, 4);
1371     undo_write_bytes(bi, (long_u)uep->ue_size, 4);
1372     for (i = 0; i < uep->ue_size; ++i)
1373     {
1374 	len = STRLEN(uep->ue_array[i]);
1375 	if (undo_write_bytes(bi, (long_u)len, 4) == FAIL)
1376 	    return FAIL;
1377 	if (len > 0 && fwrite_crypt(bi, uep->ue_array[i], len) == FAIL)
1378 	    return FAIL;
1379     }
1380     return OK;
1381 }
1382 
1383     static u_entry_T *
1384 unserialize_uep(bufinfo_T *bi, int *error, char_u *file_name)
1385 {
1386     int		i;
1387     u_entry_T	*uep;
1388     char_u	**array = NULL;
1389     char_u	*line;
1390     int		line_len;
1391 
1392     uep = (u_entry_T *)U_ALLOC_LINE(sizeof(u_entry_T));
1393     if (uep == NULL)
1394 	return NULL;
1395     vim_memset(uep, 0, sizeof(u_entry_T));
1396 #ifdef U_DEBUG
1397     uep->ue_magic = UE_MAGIC;
1398 #endif
1399     uep->ue_top = undo_read_4c(bi);
1400     uep->ue_bot = undo_read_4c(bi);
1401     uep->ue_lcount = undo_read_4c(bi);
1402     uep->ue_size = undo_read_4c(bi);
1403     if (uep->ue_size > 0)
1404     {
1405 	if (uep->ue_size < LONG_MAX / (int)sizeof(char_u *))
1406 	    array = (char_u **)U_ALLOC_LINE(sizeof(char_u *) * uep->ue_size);
1407 	if (array == NULL)
1408 	{
1409 	    *error = TRUE;
1410 	    return uep;
1411 	}
1412 	vim_memset(array, 0, sizeof(char_u *) * uep->ue_size);
1413     }
1414     uep->ue_array = array;
1415 
1416     for (i = 0; i < uep->ue_size; ++i)
1417     {
1418 	line_len = undo_read_4c(bi);
1419 	if (line_len >= 0)
1420 	    line = read_string_decrypt(bi, line_len);
1421 	else
1422 	{
1423 	    line = NULL;
1424 	    corruption_error("line length", file_name);
1425 	}
1426 	if (line == NULL)
1427 	{
1428 	    *error = TRUE;
1429 	    return uep;
1430 	}
1431 	array[i] = line;
1432     }
1433     return uep;
1434 }
1435 
1436 /*
1437  * Serialize "pos".
1438  */
1439     static void
1440 serialize_pos(bufinfo_T *bi, pos_T pos)
1441 {
1442     undo_write_bytes(bi, (long_u)pos.lnum, 4);
1443     undo_write_bytes(bi, (long_u)pos.col, 4);
1444 #ifdef FEAT_VIRTUALEDIT
1445     undo_write_bytes(bi, (long_u)pos.coladd, 4);
1446 #else
1447     undo_write_bytes(bi, (long_u)0, 4);
1448 #endif
1449 }
1450 
1451 /*
1452  * Unserialize the pos_T at the current position.
1453  */
1454     static void
1455 unserialize_pos(bufinfo_T *bi, pos_T *pos)
1456 {
1457     pos->lnum = undo_read_4c(bi);
1458     if (pos->lnum < 0)
1459 	pos->lnum = 0;
1460     pos->col = undo_read_4c(bi);
1461     if (pos->col < 0)
1462 	pos->col = 0;
1463 #ifdef FEAT_VIRTUALEDIT
1464     pos->coladd = undo_read_4c(bi);
1465     if (pos->coladd < 0)
1466 	pos->coladd = 0;
1467 #else
1468     (void)undo_read_4c(bi);
1469 #endif
1470 }
1471 
1472 /*
1473  * Serialize "info".
1474  */
1475     static void
1476 serialize_visualinfo(bufinfo_T *bi, visualinfo_T *info)
1477 {
1478     serialize_pos(bi, info->vi_start);
1479     serialize_pos(bi, info->vi_end);
1480     undo_write_bytes(bi, (long_u)info->vi_mode, 4);
1481     undo_write_bytes(bi, (long_u)info->vi_curswant, 4);
1482 }
1483 
1484 /*
1485  * Unserialize the visualinfo_T at the current position.
1486  */
1487     static void
1488 unserialize_visualinfo(bufinfo_T *bi, visualinfo_T *info)
1489 {
1490     unserialize_pos(bi, &info->vi_start);
1491     unserialize_pos(bi, &info->vi_end);
1492     info->vi_mode = undo_read_4c(bi);
1493     info->vi_curswant = undo_read_4c(bi);
1494 }
1495 
1496 /*
1497  * Write the undo tree in an undo file.
1498  * When "name" is not NULL, use it as the name of the undo file.
1499  * Otherwise use buf->b_ffname to generate the undo file name.
1500  * "buf" must never be null, buf->b_ffname is used to obtain the original file
1501  * permissions.
1502  * "forceit" is TRUE for ":wundo!", FALSE otherwise.
1503  * "hash[UNDO_HASH_SIZE]" must be the hash value of the buffer text.
1504  */
1505     void
1506 u_write_undo(
1507     char_u	*name,
1508     int		forceit,
1509     buf_T	*buf,
1510     char_u	*hash)
1511 {
1512     u_header_T	*uhp;
1513     char_u	*file_name;
1514     int		mark;
1515 #ifdef U_DEBUG
1516     int		headers_written = 0;
1517 #endif
1518     int		fd;
1519     FILE	*fp = NULL;
1520     int		perm;
1521     int		write_ok = FALSE;
1522 #ifdef UNIX
1523     int		st_old_valid = FALSE;
1524     stat_T	st_old;
1525     stat_T	st_new;
1526 #endif
1527     bufinfo_T	bi;
1528 
1529     vim_memset(&bi, 0, sizeof(bi));
1530 
1531     if (name == NULL)
1532     {
1533 	file_name = u_get_undo_file_name(buf->b_ffname, FALSE);
1534 	if (file_name == NULL)
1535 	{
1536 	    if (p_verbose > 0)
1537 	    {
1538 		verbose_enter();
1539 		smsg((char_u *)
1540 		   _("Cannot write undo file in any directory in 'undodir'"));
1541 		verbose_leave();
1542 	    }
1543 	    return;
1544 	}
1545     }
1546     else
1547 	file_name = name;
1548 
1549     /*
1550      * Decide about the permission to use for the undo file.  If the buffer
1551      * has a name use the permission of the original file.  Otherwise only
1552      * allow the user to access the undo file.
1553      */
1554     perm = 0600;
1555     if (buf->b_ffname != NULL)
1556     {
1557 #ifdef UNIX
1558 	if (mch_stat((char *)buf->b_ffname, &st_old) >= 0)
1559 	{
1560 	    perm = st_old.st_mode;
1561 	    st_old_valid = TRUE;
1562 	}
1563 #else
1564 	perm = mch_getperm(buf->b_ffname);
1565 	if (perm < 0)
1566 	    perm = 0600;
1567 #endif
1568     }
1569 
1570     /* strip any s-bit and executable bit */
1571     perm = perm & 0666;
1572 
1573     /* If the undo file already exists, verify that it actually is an undo
1574      * file, and delete it. */
1575     if (mch_getperm(file_name) >= 0)
1576     {
1577 	if (name == NULL || !forceit)
1578 	{
1579 	    /* Check we can read it and it's an undo file. */
1580 	    fd = mch_open((char *)file_name, O_RDONLY|O_EXTRA, 0);
1581 	    if (fd < 0)
1582 	    {
1583 		if (name != NULL || p_verbose > 0)
1584 		{
1585 		    if (name == NULL)
1586 			verbose_enter();
1587 		    smsg((char_u *)
1588 		      _("Will not overwrite with undo file, cannot read: %s"),
1589 								   file_name);
1590 		    if (name == NULL)
1591 			verbose_leave();
1592 		}
1593 		goto theend;
1594 	    }
1595 	    else
1596 	    {
1597 		char_u	mbuf[UF_START_MAGIC_LEN];
1598 		int	len;
1599 
1600 		len = read_eintr(fd, mbuf, UF_START_MAGIC_LEN);
1601 		close(fd);
1602 		if (len < UF_START_MAGIC_LEN
1603 		      || memcmp(mbuf, UF_START_MAGIC, UF_START_MAGIC_LEN) != 0)
1604 		{
1605 		    if (name != NULL || p_verbose > 0)
1606 		    {
1607 			if (name == NULL)
1608 			    verbose_enter();
1609 			smsg((char_u *)
1610 			_("Will not overwrite, this is not an undo file: %s"),
1611 								   file_name);
1612 			if (name == NULL)
1613 			    verbose_leave();
1614 		    }
1615 		    goto theend;
1616 		}
1617 	    }
1618 	}
1619 	mch_remove(file_name);
1620     }
1621 
1622     /* If there is no undo information at all, quit here after deleting any
1623      * existing undo file. */
1624     if (buf->b_u_numhead == 0 && buf->b_u_line_ptr == NULL)
1625     {
1626 	if (p_verbose > 0)
1627 	    verb_msg((char_u *)_("Skipping undo file write, nothing to undo"));
1628 	goto theend;
1629     }
1630 
1631     fd = mch_open((char *)file_name,
1632 			    O_CREAT|O_EXTRA|O_WRONLY|O_EXCL|O_NOFOLLOW, perm);
1633     if (fd < 0)
1634     {
1635 	EMSG2(_(e_not_open), file_name);
1636 	goto theend;
1637     }
1638     (void)mch_setperm(file_name, perm);
1639     if (p_verbose > 0)
1640     {
1641 	verbose_enter();
1642 	smsg((char_u *)_("Writing undo file: %s"), file_name);
1643 	verbose_leave();
1644     }
1645 
1646 #ifdef U_DEBUG
1647     /* Check there is no problem in undo info before writing. */
1648     u_check(FALSE);
1649 #endif
1650 
1651 #ifdef UNIX
1652     /*
1653      * Try to set the group of the undo file same as the original file. If
1654      * this fails, set the protection bits for the group same as the
1655      * protection bits for others.
1656      */
1657     if (st_old_valid
1658 	    && mch_stat((char *)file_name, &st_new) >= 0
1659 	    && st_new.st_gid != st_old.st_gid
1660 # ifdef HAVE_FCHOWN  /* sequent-ptx lacks fchown() */
1661 	    && fchown(fd, (uid_t)-1, st_old.st_gid) != 0
1662 # endif
1663        )
1664 	mch_setperm(file_name, (perm & 0707) | ((perm & 07) << 3));
1665 # if defined(HAVE_SELINUX) || defined(HAVE_SMACK)
1666     if (buf->b_ffname != NULL)
1667 	mch_copy_sec(buf->b_ffname, file_name);
1668 # endif
1669 #endif
1670 
1671     fp = fdopen(fd, "w");
1672     if (fp == NULL)
1673     {
1674 	EMSG2(_(e_not_open), file_name);
1675 	close(fd);
1676 	mch_remove(file_name);
1677 	goto theend;
1678     }
1679 
1680     /* Undo must be synced. */
1681     u_sync(TRUE);
1682 
1683     /*
1684      * Write the header.  Initializes encryption, if enabled.
1685      */
1686     bi.bi_buf = buf;
1687     bi.bi_fp = fp;
1688     if (serialize_header(&bi, hash) == FAIL)
1689 	goto write_error;
1690 
1691     /*
1692      * Iteratively serialize UHPs and their UEPs from the top down.
1693      */
1694     mark = ++lastmark;
1695     uhp = buf->b_u_oldhead;
1696     while (uhp != NULL)
1697     {
1698 	/* Serialize current UHP if we haven't seen it */
1699 	if (uhp->uh_walk != mark)
1700 	{
1701 	    uhp->uh_walk = mark;
1702 #ifdef U_DEBUG
1703 	    ++headers_written;
1704 #endif
1705 	    if (serialize_uhp(&bi, uhp) == FAIL)
1706 		goto write_error;
1707 	}
1708 
1709 	/* Now walk through the tree - algorithm from undo_time(). */
1710 	if (uhp->uh_prev.ptr != NULL && uhp->uh_prev.ptr->uh_walk != mark)
1711 	    uhp = uhp->uh_prev.ptr;
1712 	else if (uhp->uh_alt_next.ptr != NULL
1713 				     && uhp->uh_alt_next.ptr->uh_walk != mark)
1714 	    uhp = uhp->uh_alt_next.ptr;
1715 	else if (uhp->uh_next.ptr != NULL && uhp->uh_alt_prev.ptr == NULL
1716 					 && uhp->uh_next.ptr->uh_walk != mark)
1717 	    uhp = uhp->uh_next.ptr;
1718 	else if (uhp->uh_alt_prev.ptr != NULL)
1719 	    uhp = uhp->uh_alt_prev.ptr;
1720 	else
1721 	    uhp = uhp->uh_next.ptr;
1722     }
1723 
1724     if (undo_write_bytes(&bi, (long_u)UF_HEADER_END_MAGIC, 2) == OK)
1725 	write_ok = TRUE;
1726 #ifdef U_DEBUG
1727     if (headers_written != buf->b_u_numhead)
1728     {
1729 	EMSGN("Written %ld headers, ...", headers_written);
1730 	EMSGN("... but numhead is %ld", buf->b_u_numhead);
1731     }
1732 #endif
1733 
1734 #ifdef FEAT_CRYPT
1735     if (bi.bi_state != NULL && undo_flush(&bi) == FAIL)
1736 	write_ok = FALSE;
1737 #endif
1738 
1739 write_error:
1740     fclose(fp);
1741     if (!write_ok)
1742 	EMSG2(_("E829: write error in undo file: %s"), file_name);
1743 
1744 #if defined(MACOS_CLASSIC) || defined(WIN3264)
1745     /* Copy file attributes; for systems where this can only be done after
1746      * closing the file. */
1747     if (buf->b_ffname != NULL)
1748 	(void)mch_copy_file_attribute(buf->b_ffname, file_name);
1749 #endif
1750 #ifdef HAVE_ACL
1751     if (buf->b_ffname != NULL)
1752     {
1753 	vim_acl_T	    acl;
1754 
1755 	/* For systems that support ACL: get the ACL from the original file. */
1756 	acl = mch_get_acl(buf->b_ffname);
1757 	mch_set_acl(file_name, acl);
1758 	mch_free_acl(acl);
1759     }
1760 #endif
1761 
1762 theend:
1763 #ifdef FEAT_CRYPT
1764     if (bi.bi_state != NULL)
1765 	crypt_free_state(bi.bi_state);
1766     vim_free(bi.bi_buffer);
1767 #endif
1768     if (file_name != name)
1769 	vim_free(file_name);
1770 }
1771 
1772 /*
1773  * Load the undo tree from an undo file.
1774  * If "name" is not NULL use it as the undo file name.  This also means being
1775  * a bit more verbose.
1776  * Otherwise use curbuf->b_ffname to generate the undo file name.
1777  * "hash[UNDO_HASH_SIZE]" must be the hash value of the buffer text.
1778  */
1779     void
1780 u_read_undo(char_u *name, char_u *hash, char_u *orig_name)
1781 {
1782     char_u	*file_name;
1783     FILE	*fp;
1784     long	version, str_len;
1785     char_u	*line_ptr = NULL;
1786     linenr_T	line_lnum;
1787     colnr_T	line_colnr;
1788     linenr_T	line_count;
1789     long	num_head = 0;
1790     long	old_header_seq, new_header_seq, cur_header_seq;
1791     long	seq_last, seq_cur;
1792     long	last_save_nr = 0;
1793     short	old_idx = -1, new_idx = -1, cur_idx = -1;
1794     long	num_read_uhps = 0;
1795     time_t	seq_time;
1796     int		i, j;
1797     int		c;
1798     u_header_T	*uhp;
1799     u_header_T	**uhp_table = NULL;
1800     char_u	read_hash[UNDO_HASH_SIZE];
1801     char_u	magic_buf[UF_START_MAGIC_LEN];
1802 #ifdef U_DEBUG
1803     int		*uhp_table_used;
1804 #endif
1805 #ifdef UNIX
1806     stat_T	st_orig;
1807     stat_T	st_undo;
1808 #endif
1809     bufinfo_T	bi;
1810 
1811     vim_memset(&bi, 0, sizeof(bi));
1812     if (name == NULL)
1813     {
1814 	file_name = u_get_undo_file_name(curbuf->b_ffname, TRUE);
1815 	if (file_name == NULL)
1816 	    return;
1817 
1818 #ifdef UNIX
1819 	/* For safety we only read an undo file if the owner is equal to the
1820 	 * owner of the text file or equal to the current user. */
1821 	if (mch_stat((char *)orig_name, &st_orig) >= 0
1822 		&& mch_stat((char *)file_name, &st_undo) >= 0
1823 		&& st_orig.st_uid != st_undo.st_uid
1824 		&& st_undo.st_uid != getuid())
1825 	{
1826 	    if (p_verbose > 0)
1827 	    {
1828 		verbose_enter();
1829 		smsg((char_u *)_("Not reading undo file, owner differs: %s"),
1830 								   file_name);
1831 		verbose_leave();
1832 	    }
1833 	    return;
1834 	}
1835 #endif
1836     }
1837     else
1838 	file_name = name;
1839 
1840     if (p_verbose > 0)
1841     {
1842 	verbose_enter();
1843 	smsg((char_u *)_("Reading undo file: %s"), file_name);
1844 	verbose_leave();
1845     }
1846 
1847     fp = mch_fopen((char *)file_name, "r");
1848     if (fp == NULL)
1849     {
1850 	if (name != NULL || p_verbose > 0)
1851 	    EMSG2(_("E822: Cannot open undo file for reading: %s"), file_name);
1852 	goto error;
1853     }
1854     bi.bi_buf = curbuf;
1855     bi.bi_fp = fp;
1856 
1857     /*
1858      * Read the undo file header.
1859      */
1860     if (fread(magic_buf, UF_START_MAGIC_LEN, 1, fp) != 1
1861 		|| memcmp(magic_buf, UF_START_MAGIC, UF_START_MAGIC_LEN) != 0)
1862     {
1863 	EMSG2(_("E823: Not an undo file: %s"), file_name);
1864 	goto error;
1865     }
1866     version = get2c(fp);
1867     if (version == UF_VERSION_CRYPT)
1868     {
1869 #ifdef FEAT_CRYPT
1870 	if (*curbuf->b_p_key == NUL)
1871 	{
1872 	    EMSG2(_("E832: Non-encrypted file has encrypted undo file: %s"),
1873 								   file_name);
1874 	    goto error;
1875 	}
1876 	bi.bi_state = crypt_create_from_file(fp, curbuf->b_p_key);
1877 	if (bi.bi_state == NULL)
1878 	{
1879 	    EMSG2(_("E826: Undo file decryption failed: %s"), file_name);
1880 	    goto error;
1881 	}
1882 	if (crypt_whole_undofile(bi.bi_state->method_nr))
1883 	{
1884 	    bi.bi_buffer = alloc(CRYPT_BUF_SIZE);
1885 	    if (bi.bi_buffer == NULL)
1886 	    {
1887 		crypt_free_state(bi.bi_state);
1888 		bi.bi_state = NULL;
1889 		goto error;
1890 	    }
1891 	    bi.bi_avail = 0;
1892 	    bi.bi_used = 0;
1893 	}
1894 #else
1895 	EMSG2(_("E827: Undo file is encrypted: %s"), file_name);
1896 	goto error;
1897 #endif
1898     }
1899     else if (version != UF_VERSION)
1900     {
1901 	EMSG2(_("E824: Incompatible undo file: %s"), file_name);
1902 	goto error;
1903     }
1904 
1905     if (undo_read(&bi, read_hash, (size_t)UNDO_HASH_SIZE) == FAIL)
1906     {
1907 	corruption_error("hash", file_name);
1908 	goto error;
1909     }
1910     line_count = (linenr_T)undo_read_4c(&bi);
1911     if (memcmp(hash, read_hash, UNDO_HASH_SIZE) != 0
1912 				  || line_count != curbuf->b_ml.ml_line_count)
1913     {
1914 	if (p_verbose > 0 || name != NULL)
1915 	{
1916 	    if (name == NULL)
1917 		verbose_enter();
1918 	    give_warning((char_u *)
1919 		      _("File contents changed, cannot use undo info"), TRUE);
1920 	    if (name == NULL)
1921 		verbose_leave();
1922 	}
1923 	goto error;
1924     }
1925 
1926     /* Read undo data for "U" command. */
1927     str_len = undo_read_4c(&bi);
1928     if (str_len < 0)
1929 	goto error;
1930     if (str_len > 0)
1931 	line_ptr = read_string_decrypt(&bi, str_len);
1932     line_lnum = (linenr_T)undo_read_4c(&bi);
1933     line_colnr = (colnr_T)undo_read_4c(&bi);
1934     if (line_lnum < 0 || line_colnr < 0)
1935     {
1936 	corruption_error("line lnum/col", file_name);
1937 	goto error;
1938     }
1939 
1940     /* Begin general undo data */
1941     old_header_seq = undo_read_4c(&bi);
1942     new_header_seq = undo_read_4c(&bi);
1943     cur_header_seq = undo_read_4c(&bi);
1944     num_head = undo_read_4c(&bi);
1945     seq_last = undo_read_4c(&bi);
1946     seq_cur = undo_read_4c(&bi);
1947     seq_time = undo_read_time(&bi);
1948 
1949     /* Optional header fields. */
1950     for (;;)
1951     {
1952 	int len = undo_read_byte(&bi);
1953 	int what;
1954 
1955 	if (len == 0 || len == EOF)
1956 	    break;
1957 	what = undo_read_byte(&bi);
1958 	switch (what)
1959 	{
1960 	    case UF_LAST_SAVE_NR:
1961 		last_save_nr = undo_read_4c(&bi);
1962 		break;
1963 	    default:
1964 		/* field not supported, skip */
1965 		while (--len >= 0)
1966 		    (void)undo_read_byte(&bi);
1967 	}
1968     }
1969 
1970     /* uhp_table will store the freshly created undo headers we allocate
1971      * until we insert them into curbuf. The table remains sorted by the
1972      * sequence numbers of the headers.
1973      * When there are no headers uhp_table is NULL. */
1974     if (num_head > 0)
1975     {
1976 	if (num_head < LONG_MAX / (long)sizeof(u_header_T *))
1977 	    uhp_table = (u_header_T **)U_ALLOC_LINE(
1978 					     num_head * sizeof(u_header_T *));
1979 	if (uhp_table == NULL)
1980 	    goto error;
1981     }
1982 
1983     while ((c = undo_read_2c(&bi)) == UF_HEADER_MAGIC)
1984     {
1985 	if (num_read_uhps >= num_head)
1986 	{
1987 	    corruption_error("num_head too small", file_name);
1988 	    goto error;
1989 	}
1990 
1991 	uhp = unserialize_uhp(&bi, file_name);
1992 	if (uhp == NULL)
1993 	    goto error;
1994 	uhp_table[num_read_uhps++] = uhp;
1995     }
1996 
1997     if (num_read_uhps != num_head)
1998     {
1999 	corruption_error("num_head", file_name);
2000 	goto error;
2001     }
2002     if (c != UF_HEADER_END_MAGIC)
2003     {
2004 	corruption_error("end marker", file_name);
2005 	goto error;
2006     }
2007 
2008 #ifdef U_DEBUG
2009     uhp_table_used = (int *)alloc_clear(
2010 				     (unsigned)(sizeof(int) * num_head + 1));
2011 # define SET_FLAG(j) ++uhp_table_used[j]
2012 #else
2013 # define SET_FLAG(j)
2014 #endif
2015 
2016     /* We have put all of the headers into a table. Now we iterate through the
2017      * table and swizzle each sequence number we have stored in uh_*_seq into
2018      * a pointer corresponding to the header with that sequence number. */
2019     for (i = 0; i < num_head; i++)
2020     {
2021 	uhp = uhp_table[i];
2022 	if (uhp == NULL)
2023 	    continue;
2024 	for (j = 0; j < num_head; j++)
2025 	    if (uhp_table[j] != NULL && i != j
2026 			      && uhp_table[i]->uh_seq == uhp_table[j]->uh_seq)
2027 	    {
2028 		corruption_error("duplicate uh_seq", file_name);
2029 		goto error;
2030 	    }
2031 	for (j = 0; j < num_head; j++)
2032 	    if (uhp_table[j] != NULL
2033 				  && uhp_table[j]->uh_seq == uhp->uh_next.seq)
2034 	    {
2035 		uhp->uh_next.ptr = uhp_table[j];
2036 		SET_FLAG(j);
2037 		break;
2038 	    }
2039 	for (j = 0; j < num_head; j++)
2040 	    if (uhp_table[j] != NULL
2041 				  && uhp_table[j]->uh_seq == uhp->uh_prev.seq)
2042 	    {
2043 		uhp->uh_prev.ptr = uhp_table[j];
2044 		SET_FLAG(j);
2045 		break;
2046 	    }
2047 	for (j = 0; j < num_head; j++)
2048 	    if (uhp_table[j] != NULL
2049 			      && uhp_table[j]->uh_seq == uhp->uh_alt_next.seq)
2050 	    {
2051 		uhp->uh_alt_next.ptr = uhp_table[j];
2052 		SET_FLAG(j);
2053 		break;
2054 	    }
2055 	for (j = 0; j < num_head; j++)
2056 	    if (uhp_table[j] != NULL
2057 			      && uhp_table[j]->uh_seq == uhp->uh_alt_prev.seq)
2058 	    {
2059 		uhp->uh_alt_prev.ptr = uhp_table[j];
2060 		SET_FLAG(j);
2061 		break;
2062 	    }
2063 	if (old_header_seq > 0 && old_idx < 0 && uhp->uh_seq == old_header_seq)
2064 	{
2065 	    old_idx = i;
2066 	    SET_FLAG(i);
2067 	}
2068 	if (new_header_seq > 0 && new_idx < 0 && uhp->uh_seq == new_header_seq)
2069 	{
2070 	    new_idx = i;
2071 	    SET_FLAG(i);
2072 	}
2073 	if (cur_header_seq > 0 && cur_idx < 0 && uhp->uh_seq == cur_header_seq)
2074 	{
2075 	    cur_idx = i;
2076 	    SET_FLAG(i);
2077 	}
2078     }
2079 
2080     /* Now that we have read the undo info successfully, free the current undo
2081      * info and use the info from the file. */
2082     u_blockfree(curbuf);
2083     curbuf->b_u_oldhead = old_idx < 0 ? NULL : uhp_table[old_idx];
2084     curbuf->b_u_newhead = new_idx < 0 ? NULL : uhp_table[new_idx];
2085     curbuf->b_u_curhead = cur_idx < 0 ? NULL : uhp_table[cur_idx];
2086     curbuf->b_u_line_ptr = line_ptr;
2087     curbuf->b_u_line_lnum = line_lnum;
2088     curbuf->b_u_line_colnr = line_colnr;
2089     curbuf->b_u_numhead = num_head;
2090     curbuf->b_u_seq_last = seq_last;
2091     curbuf->b_u_seq_cur = seq_cur;
2092     curbuf->b_u_time_cur = seq_time;
2093     curbuf->b_u_save_nr_last = last_save_nr;
2094     curbuf->b_u_save_nr_cur = last_save_nr;
2095 
2096     curbuf->b_u_synced = TRUE;
2097     vim_free(uhp_table);
2098 
2099 #ifdef U_DEBUG
2100     for (i = 0; i < num_head; ++i)
2101 	if (uhp_table_used[i] == 0)
2102 	    EMSGN("uhp_table entry %ld not used, leaking memory", i);
2103     vim_free(uhp_table_used);
2104     u_check(TRUE);
2105 #endif
2106 
2107     if (name != NULL)
2108 	smsg((char_u *)_("Finished reading undo file %s"), file_name);
2109     goto theend;
2110 
2111 error:
2112     vim_free(line_ptr);
2113     if (uhp_table != NULL)
2114     {
2115 	for (i = 0; i < num_read_uhps; i++)
2116 	    if (uhp_table[i] != NULL)
2117 		u_free_uhp(uhp_table[i]);
2118 	vim_free(uhp_table);
2119     }
2120 
2121 theend:
2122 #ifdef FEAT_CRYPT
2123     if (bi.bi_state != NULL)
2124 	crypt_free_state(bi.bi_state);
2125     vim_free(bi.bi_buffer);
2126 #endif
2127     if (fp != NULL)
2128 	fclose(fp);
2129     if (file_name != name)
2130 	vim_free(file_name);
2131     return;
2132 }
2133 
2134 #endif /* FEAT_PERSISTENT_UNDO */
2135 
2136 
2137 /*
2138  * If 'cpoptions' contains 'u': Undo the previous undo or redo (vi compatible).
2139  * If 'cpoptions' does not contain 'u': Always undo.
2140  */
2141     void
2142 u_undo(int count)
2143 {
2144     /*
2145      * If we get an undo command while executing a macro, we behave like the
2146      * original vi. If this happens twice in one macro the result will not
2147      * be compatible.
2148      */
2149     if (curbuf->b_u_synced == FALSE)
2150     {
2151 	u_sync(TRUE);
2152 	count = 1;
2153     }
2154 
2155     if (vim_strchr(p_cpo, CPO_UNDO) == NULL)
2156 	undo_undoes = TRUE;
2157     else
2158 	undo_undoes = !undo_undoes;
2159     u_doit(count);
2160 }
2161 
2162 /*
2163  * If 'cpoptions' contains 'u': Repeat the previous undo or redo.
2164  * If 'cpoptions' does not contain 'u': Always redo.
2165  */
2166     void
2167 u_redo(int count)
2168 {
2169     if (vim_strchr(p_cpo, CPO_UNDO) == NULL)
2170 	undo_undoes = FALSE;
2171     u_doit(count);
2172 }
2173 
2174 /*
2175  * Undo or redo, depending on 'undo_undoes', 'count' times.
2176  */
2177     static void
2178 u_doit(int startcount)
2179 {
2180     int count = startcount;
2181 
2182     if (!undo_allowed())
2183 	return;
2184 
2185     u_newcount = 0;
2186     u_oldcount = 0;
2187     if (curbuf->b_ml.ml_flags & ML_EMPTY)
2188 	u_oldcount = -1;
2189     while (count--)
2190     {
2191 	/* Do the change warning now, so that it triggers FileChangedRO when
2192 	 * needed.  This may cause the file to be reloaded, that must happen
2193 	 * before we do anything, because it may change curbuf->b_u_curhead
2194 	 * and more. */
2195 	change_warning(0);
2196 
2197 	if (undo_undoes)
2198 	{
2199 	    if (curbuf->b_u_curhead == NULL)		/* first undo */
2200 		curbuf->b_u_curhead = curbuf->b_u_newhead;
2201 	    else if (get_undolevel() > 0)		/* multi level undo */
2202 		/* get next undo */
2203 		curbuf->b_u_curhead = curbuf->b_u_curhead->uh_next.ptr;
2204 	    /* nothing to undo */
2205 	    if (curbuf->b_u_numhead == 0 || curbuf->b_u_curhead == NULL)
2206 	    {
2207 		/* stick curbuf->b_u_curhead at end */
2208 		curbuf->b_u_curhead = curbuf->b_u_oldhead;
2209 		beep_flush();
2210 		if (count == startcount - 1)
2211 		{
2212 		    MSG(_("Already at oldest change"));
2213 		    return;
2214 		}
2215 		break;
2216 	    }
2217 
2218 	    u_undoredo(TRUE);
2219 	}
2220 	else
2221 	{
2222 	    if (curbuf->b_u_curhead == NULL || get_undolevel() <= 0)
2223 	    {
2224 		beep_flush();	/* nothing to redo */
2225 		if (count == startcount - 1)
2226 		{
2227 		    MSG(_("Already at newest change"));
2228 		    return;
2229 		}
2230 		break;
2231 	    }
2232 
2233 	    u_undoredo(FALSE);
2234 
2235 	    /* Advance for next redo.  Set "newhead" when at the end of the
2236 	     * redoable changes. */
2237 	    if (curbuf->b_u_curhead->uh_prev.ptr == NULL)
2238 		curbuf->b_u_newhead = curbuf->b_u_curhead;
2239 	    curbuf->b_u_curhead = curbuf->b_u_curhead->uh_prev.ptr;
2240 	}
2241     }
2242     u_undo_end(undo_undoes, FALSE);
2243 }
2244 
2245 /*
2246  * Undo or redo over the timeline.
2247  * When "step" is negative go back in time, otherwise goes forward in time.
2248  * When "sec" is FALSE make "step" steps, when "sec" is TRUE use "step" as
2249  * seconds.
2250  * When "file" is TRUE use "step" as a number of file writes.
2251  * When "absolute" is TRUE use "step" as the sequence number to jump to.
2252  * "sec" must be FALSE then.
2253  */
2254     void
2255 undo_time(
2256     long	step,
2257     int		sec,
2258     int		file,
2259     int		absolute)
2260 {
2261     long	    target;
2262     long	    closest;
2263     long	    closest_start;
2264     long	    closest_seq = 0;
2265     long	    val;
2266     u_header_T	    *uhp;
2267     u_header_T	    *last;
2268     int		    mark;
2269     int		    nomark;
2270     int		    round;
2271     int		    dosec = sec;
2272     int		    dofile = file;
2273     int		    above = FALSE;
2274     int		    did_undo = TRUE;
2275 
2276     /* First make sure the current undoable change is synced. */
2277     if (curbuf->b_u_synced == FALSE)
2278 	u_sync(TRUE);
2279 
2280     u_newcount = 0;
2281     u_oldcount = 0;
2282     if (curbuf->b_ml.ml_flags & ML_EMPTY)
2283 	u_oldcount = -1;
2284 
2285     /* "target" is the node below which we want to be.
2286      * Init "closest" to a value we can't reach. */
2287     if (absolute)
2288     {
2289 	if (step == 0)
2290 	{
2291 	    /* target 0 does not exist, got to 1 and above it. */
2292 	    target = 1;
2293 	    above = TRUE;
2294 	}
2295 	else
2296 	    target = step;
2297 	closest = -1;
2298     }
2299     else
2300     {
2301 	if (dosec)
2302 	    target = (long)(curbuf->b_u_time_cur) + step;
2303 	else if (dofile)
2304 	{
2305 	    if (step < 0)
2306 	    {
2307 		/* Going back to a previous write. If there were changes after
2308 		 * the last write, count that as moving one file-write, so
2309 		 * that ":earlier 1f" undoes all changes since the last save. */
2310 		uhp = curbuf->b_u_curhead;
2311 		if (uhp != NULL)
2312 		    uhp = uhp->uh_next.ptr;
2313 		else
2314 		    uhp = curbuf->b_u_newhead;
2315 		if (uhp != NULL && uhp->uh_save_nr != 0)
2316 		    /* "uh_save_nr" was set in the last block, that means
2317 		     * there were no changes since the last write */
2318 		    target = curbuf->b_u_save_nr_cur + step;
2319 		else
2320 		    /* count the changes since the last write as one step */
2321 		    target = curbuf->b_u_save_nr_cur + step + 1;
2322 		if (target <= 0)
2323 		    /* Go to before first write: before the oldest change. Use
2324 		     * the sequence number for that. */
2325 		    dofile = FALSE;
2326 	    }
2327 	    else
2328 	    {
2329 		/* Moving forward to a newer write. */
2330 		target = curbuf->b_u_save_nr_cur + step;
2331 		if (target > curbuf->b_u_save_nr_last)
2332 		{
2333 		    /* Go to after last write: after the latest change. Use
2334 		     * the sequence number for that. */
2335 		    target = curbuf->b_u_seq_last + 1;
2336 		    dofile = FALSE;
2337 		}
2338 	    }
2339 	}
2340 	else
2341 	    target = curbuf->b_u_seq_cur + step;
2342 	if (step < 0)
2343 	{
2344 	    if (target < 0)
2345 		target = 0;
2346 	    closest = -1;
2347 	}
2348 	else
2349 	{
2350 	    if (dosec)
2351 		closest = (long)(vim_time() + 1);
2352 	    else if (dofile)
2353 		closest = curbuf->b_u_save_nr_last + 2;
2354 	    else
2355 		closest = curbuf->b_u_seq_last + 2;
2356 	    if (target >= closest)
2357 		target = closest - 1;
2358 	}
2359     }
2360     closest_start = closest;
2361     closest_seq = curbuf->b_u_seq_cur;
2362 
2363     /*
2364      * May do this twice:
2365      * 1. Search for "target", update "closest" to the best match found.
2366      * 2. If "target" not found search for "closest".
2367      *
2368      * When using the closest time we use the sequence number in the second
2369      * round, because there may be several entries with the same time.
2370      */
2371     for (round = 1; round <= 2; ++round)
2372     {
2373 	/* Find the path from the current state to where we want to go.  The
2374 	 * desired state can be anywhere in the undo tree, need to go all over
2375 	 * it.  We put "nomark" in uh_walk where we have been without success,
2376 	 * "mark" where it could possibly be. */
2377 	mark = ++lastmark;
2378 	nomark = ++lastmark;
2379 
2380 	if (curbuf->b_u_curhead == NULL)	/* at leaf of the tree */
2381 	    uhp = curbuf->b_u_newhead;
2382 	else
2383 	    uhp = curbuf->b_u_curhead;
2384 
2385 	while (uhp != NULL)
2386 	{
2387 	    uhp->uh_walk = mark;
2388 	    if (dosec)
2389 		val = (long)(uhp->uh_time);
2390 	    else if (dofile)
2391 		val = uhp->uh_save_nr;
2392 	    else
2393 		val = uhp->uh_seq;
2394 
2395 	    if (round == 1 && !(dofile && val == 0))
2396 	    {
2397 		/* Remember the header that is closest to the target.
2398 		 * It must be at least in the right direction (checked with
2399 		 * "b_u_seq_cur").  When the timestamp is equal find the
2400 		 * highest/lowest sequence number. */
2401 		if ((step < 0 ? uhp->uh_seq <= curbuf->b_u_seq_cur
2402 			      : uhp->uh_seq > curbuf->b_u_seq_cur)
2403 			&& ((dosec && val == closest)
2404 			    ? (step < 0
2405 				? uhp->uh_seq < closest_seq
2406 				: uhp->uh_seq > closest_seq)
2407 			    : closest == closest_start
2408 				|| (val > target
2409 				    ? (closest > target
2410 					? val - target <= closest - target
2411 					: val - target <= target - closest)
2412 				    : (closest > target
2413 					? target - val <= closest - target
2414 					: target - val <= target - closest))))
2415 		{
2416 		    closest = val;
2417 		    closest_seq = uhp->uh_seq;
2418 		}
2419 	    }
2420 
2421 	    /* Quit searching when we found a match.  But when searching for a
2422 	     * time we need to continue looking for the best uh_seq. */
2423 	    if (target == val && !dosec)
2424 	    {
2425 		target = uhp->uh_seq;
2426 		break;
2427 	    }
2428 
2429 	    /* go down in the tree if we haven't been there */
2430 	    if (uhp->uh_prev.ptr != NULL && uhp->uh_prev.ptr->uh_walk != nomark
2431 					 && uhp->uh_prev.ptr->uh_walk != mark)
2432 		uhp = uhp->uh_prev.ptr;
2433 
2434 	    /* go to alternate branch if we haven't been there */
2435 	    else if (uhp->uh_alt_next.ptr != NULL
2436 		    && uhp->uh_alt_next.ptr->uh_walk != nomark
2437 		    && uhp->uh_alt_next.ptr->uh_walk != mark)
2438 		uhp = uhp->uh_alt_next.ptr;
2439 
2440 	    /* go up in the tree if we haven't been there and we are at the
2441 	     * start of alternate branches */
2442 	    else if (uhp->uh_next.ptr != NULL && uhp->uh_alt_prev.ptr == NULL
2443 		    && uhp->uh_next.ptr->uh_walk != nomark
2444 		    && uhp->uh_next.ptr->uh_walk != mark)
2445 	    {
2446 		/* If still at the start we don't go through this change. */
2447 		if (uhp == curbuf->b_u_curhead)
2448 		    uhp->uh_walk = nomark;
2449 		uhp = uhp->uh_next.ptr;
2450 	    }
2451 
2452 	    else
2453 	    {
2454 		/* need to backtrack; mark this node as useless */
2455 		uhp->uh_walk = nomark;
2456 		if (uhp->uh_alt_prev.ptr != NULL)
2457 		    uhp = uhp->uh_alt_prev.ptr;
2458 		else
2459 		    uhp = uhp->uh_next.ptr;
2460 	    }
2461 	}
2462 
2463 	if (uhp != NULL)    /* found it */
2464 	    break;
2465 
2466 	if (absolute)
2467 	{
2468 	    EMSGN(_("E830: Undo number %ld not found"), step);
2469 	    return;
2470 	}
2471 
2472 	if (closest == closest_start)
2473 	{
2474 	    if (step < 0)
2475 		MSG(_("Already at oldest change"));
2476 	    else
2477 		MSG(_("Already at newest change"));
2478 	    return;
2479 	}
2480 
2481 	target = closest_seq;
2482 	dosec = FALSE;
2483 	dofile = FALSE;
2484 	if (step < 0)
2485 	    above = TRUE;	/* stop above the header */
2486     }
2487 
2488     /* If we found it: Follow the path to go to where we want to be. */
2489     if (uhp != NULL)
2490     {
2491 	/*
2492 	 * First go up the tree as much as needed.
2493 	 */
2494 	while (!got_int)
2495 	{
2496 	    /* Do the change warning now, for the same reason as above. */
2497 	    change_warning(0);
2498 
2499 	    uhp = curbuf->b_u_curhead;
2500 	    if (uhp == NULL)
2501 		uhp = curbuf->b_u_newhead;
2502 	    else
2503 		uhp = uhp->uh_next.ptr;
2504 	    if (uhp == NULL || uhp->uh_walk != mark
2505 					 || (uhp->uh_seq == target && !above))
2506 		break;
2507 	    curbuf->b_u_curhead = uhp;
2508 	    u_undoredo(TRUE);
2509 	    uhp->uh_walk = nomark;	/* don't go back down here */
2510 	}
2511 
2512 	/*
2513 	 * And now go down the tree (redo), branching off where needed.
2514 	 */
2515 	while (!got_int)
2516 	{
2517 	    /* Do the change warning now, for the same reason as above. */
2518 	    change_warning(0);
2519 
2520 	    uhp = curbuf->b_u_curhead;
2521 	    if (uhp == NULL)
2522 		break;
2523 
2524 	    /* Go back to the first branch with a mark. */
2525 	    while (uhp->uh_alt_prev.ptr != NULL
2526 				     && uhp->uh_alt_prev.ptr->uh_walk == mark)
2527 		uhp = uhp->uh_alt_prev.ptr;
2528 
2529 	    /* Find the last branch with a mark, that's the one. */
2530 	    last = uhp;
2531 	    while (last->uh_alt_next.ptr != NULL
2532 				    && last->uh_alt_next.ptr->uh_walk == mark)
2533 		last = last->uh_alt_next.ptr;
2534 	    if (last != uhp)
2535 	    {
2536 		/* Make the used branch the first entry in the list of
2537 		 * alternatives to make "u" and CTRL-R take this branch. */
2538 		while (uhp->uh_alt_prev.ptr != NULL)
2539 		    uhp = uhp->uh_alt_prev.ptr;
2540 		if (last->uh_alt_next.ptr != NULL)
2541 		    last->uh_alt_next.ptr->uh_alt_prev.ptr =
2542 							last->uh_alt_prev.ptr;
2543 		last->uh_alt_prev.ptr->uh_alt_next.ptr = last->uh_alt_next.ptr;
2544 		last->uh_alt_prev.ptr = NULL;
2545 		last->uh_alt_next.ptr = uhp;
2546 		uhp->uh_alt_prev.ptr = last;
2547 
2548 		if (curbuf->b_u_oldhead == uhp)
2549 		    curbuf->b_u_oldhead = last;
2550 		uhp = last;
2551 		if (uhp->uh_next.ptr != NULL)
2552 		    uhp->uh_next.ptr->uh_prev.ptr = uhp;
2553 	    }
2554 	    curbuf->b_u_curhead = uhp;
2555 
2556 	    if (uhp->uh_walk != mark)
2557 		break;	    /* must have reached the target */
2558 
2559 	    /* Stop when going backwards in time and didn't find the exact
2560 	     * header we were looking for. */
2561 	    if (uhp->uh_seq == target && above)
2562 	    {
2563 		curbuf->b_u_seq_cur = target - 1;
2564 		break;
2565 	    }
2566 
2567 	    u_undoredo(FALSE);
2568 
2569 	    /* Advance "curhead" to below the header we last used.  If it
2570 	     * becomes NULL then we need to set "newhead" to this leaf. */
2571 	    if (uhp->uh_prev.ptr == NULL)
2572 		curbuf->b_u_newhead = uhp;
2573 	    curbuf->b_u_curhead = uhp->uh_prev.ptr;
2574 	    did_undo = FALSE;
2575 
2576 	    if (uhp->uh_seq == target)	/* found it! */
2577 		break;
2578 
2579 	    uhp = uhp->uh_prev.ptr;
2580 	    if (uhp == NULL || uhp->uh_walk != mark)
2581 	    {
2582 		/* Need to redo more but can't find it... */
2583 		internal_error("undo_time()");
2584 		break;
2585 	    }
2586 	}
2587     }
2588     u_undo_end(did_undo, absolute);
2589 }
2590 
2591 /*
2592  * u_undoredo: common code for undo and redo
2593  *
2594  * The lines in the file are replaced by the lines in the entry list at
2595  * curbuf->b_u_curhead. The replaced lines in the file are saved in the entry
2596  * list for the next undo/redo.
2597  *
2598  * When "undo" is TRUE we go up in the tree, when FALSE we go down.
2599  */
2600     static void
2601 u_undoredo(int undo)
2602 {
2603     char_u	**newarray = NULL;
2604     linenr_T	oldsize;
2605     linenr_T	newsize;
2606     linenr_T	top, bot;
2607     linenr_T	lnum;
2608     linenr_T	newlnum = MAXLNUM;
2609     long	i;
2610     u_entry_T	*uep, *nuep;
2611     u_entry_T	*newlist = NULL;
2612     int		old_flags;
2613     int		new_flags;
2614     pos_T	namedm[NMARKS];
2615     visualinfo_T visualinfo;
2616     int		empty_buffer;		    /* buffer became empty */
2617     u_header_T	*curhead = curbuf->b_u_curhead;
2618 
2619 #ifdef FEAT_AUTOCMD
2620     /* Don't want autocommands using the undo structures here, they are
2621      * invalid till the end. */
2622     block_autocmds();
2623 #endif
2624 
2625 #ifdef U_DEBUG
2626     u_check(FALSE);
2627 #endif
2628     old_flags = curhead->uh_flags;
2629     new_flags = (curbuf->b_changed ? UH_CHANGED : 0) +
2630 	       ((curbuf->b_ml.ml_flags & ML_EMPTY) ? UH_EMPTYBUF : 0);
2631     setpcmark();
2632 
2633     /*
2634      * save marks before undo/redo
2635      */
2636     mch_memmove(namedm, curbuf->b_namedm, sizeof(pos_T) * NMARKS);
2637     visualinfo = curbuf->b_visual;
2638     curbuf->b_op_start.lnum = curbuf->b_ml.ml_line_count;
2639     curbuf->b_op_start.col = 0;
2640     curbuf->b_op_end.lnum = 0;
2641     curbuf->b_op_end.col = 0;
2642 
2643     for (uep = curhead->uh_entry; uep != NULL; uep = nuep)
2644     {
2645 	top = uep->ue_top;
2646 	bot = uep->ue_bot;
2647 	if (bot == 0)
2648 	    bot = curbuf->b_ml.ml_line_count + 1;
2649 	if (top > curbuf->b_ml.ml_line_count || top >= bot
2650 				      || bot > curbuf->b_ml.ml_line_count + 1)
2651 	{
2652 #ifdef FEAT_AUTOCMD
2653 	    unblock_autocmds();
2654 #endif
2655 	    IEMSG(_("E438: u_undo: line numbers wrong"));
2656 	    changed();		/* don't want UNCHANGED now */
2657 	    return;
2658 	}
2659 
2660 	oldsize = bot - top - 1;    /* number of lines before undo */
2661 	newsize = uep->ue_size;	    /* number of lines after undo */
2662 
2663 	if (top < newlnum)
2664 	{
2665 	    /* If the saved cursor is somewhere in this undo block, move it to
2666 	     * the remembered position.  Makes "gwap" put the cursor back
2667 	     * where it was. */
2668 	    lnum = curhead->uh_cursor.lnum;
2669 	    if (lnum >= top && lnum <= top + newsize + 1)
2670 	    {
2671 		curwin->w_cursor = curhead->uh_cursor;
2672 		newlnum = curwin->w_cursor.lnum - 1;
2673 	    }
2674 	    else
2675 	    {
2676 		/* Use the first line that actually changed.  Avoids that
2677 		 * undoing auto-formatting puts the cursor in the previous
2678 		 * line. */
2679 		for (i = 0; i < newsize && i < oldsize; ++i)
2680 		    if (STRCMP(uep->ue_array[i], ml_get(top + 1 + i)) != 0)
2681 			break;
2682 		if (i == newsize && newlnum == MAXLNUM && uep->ue_next == NULL)
2683 		{
2684 		    newlnum = top;
2685 		    curwin->w_cursor.lnum = newlnum + 1;
2686 		}
2687 		else if (i < newsize)
2688 		{
2689 		    newlnum = top + i;
2690 		    curwin->w_cursor.lnum = newlnum + 1;
2691 		}
2692 	    }
2693 	}
2694 
2695 	empty_buffer = FALSE;
2696 
2697 	/* delete the lines between top and bot and save them in newarray */
2698 	if (oldsize > 0)
2699 	{
2700 	    if ((newarray = (char_u **)U_ALLOC_LINE(
2701 					 sizeof(char_u *) * oldsize)) == NULL)
2702 	    {
2703 		do_outofmem_msg((long_u)(sizeof(char_u *) * oldsize));
2704 		/*
2705 		 * We have messed up the entry list, repair is impossible.
2706 		 * we have to free the rest of the list.
2707 		 */
2708 		while (uep != NULL)
2709 		{
2710 		    nuep = uep->ue_next;
2711 		    u_freeentry(uep, uep->ue_size);
2712 		    uep = nuep;
2713 		}
2714 		break;
2715 	    }
2716 	    /* delete backwards, it goes faster in most cases */
2717 	    for (lnum = bot - 1, i = oldsize; --i >= 0; --lnum)
2718 	    {
2719 		/* what can we do when we run out of memory? */
2720 		if ((newarray[i] = u_save_line(lnum)) == NULL)
2721 		    do_outofmem_msg((long_u)0);
2722 		/* remember we deleted the last line in the buffer, and a
2723 		 * dummy empty line will be inserted */
2724 		if (curbuf->b_ml.ml_line_count == 1)
2725 		    empty_buffer = TRUE;
2726 		ml_delete(lnum, FALSE);
2727 	    }
2728 	}
2729 	else
2730 	    newarray = NULL;
2731 
2732 	/* insert the lines in u_array between top and bot */
2733 	if (newsize)
2734 	{
2735 	    for (lnum = top, i = 0; i < newsize; ++i, ++lnum)
2736 	    {
2737 		/*
2738 		 * If the file is empty, there is an empty line 1 that we
2739 		 * should get rid of, by replacing it with the new line
2740 		 */
2741 		if (empty_buffer && lnum == 0)
2742 		    ml_replace((linenr_T)1, uep->ue_array[i], TRUE);
2743 		else
2744 		    ml_append(lnum, uep->ue_array[i], (colnr_T)0, FALSE);
2745 		vim_free(uep->ue_array[i]);
2746 	    }
2747 	    vim_free((char_u *)uep->ue_array);
2748 	}
2749 
2750 	/* adjust marks */
2751 	if (oldsize != newsize)
2752 	{
2753 	    mark_adjust(top + 1, top + oldsize, (long)MAXLNUM,
2754 					       (long)newsize - (long)oldsize);
2755 	    if (curbuf->b_op_start.lnum > top + oldsize)
2756 		curbuf->b_op_start.lnum += newsize - oldsize;
2757 	    if (curbuf->b_op_end.lnum > top + oldsize)
2758 		curbuf->b_op_end.lnum += newsize - oldsize;
2759 	}
2760 
2761 	changed_lines(top + 1, 0, bot, newsize - oldsize);
2762 
2763 	/* set '[ and '] mark */
2764 	if (top + 1 < curbuf->b_op_start.lnum)
2765 	    curbuf->b_op_start.lnum = top + 1;
2766 	if (newsize == 0 && top + 1 > curbuf->b_op_end.lnum)
2767 	    curbuf->b_op_end.lnum = top + 1;
2768 	else if (top + newsize > curbuf->b_op_end.lnum)
2769 	    curbuf->b_op_end.lnum = top + newsize;
2770 
2771 	u_newcount += newsize;
2772 	u_oldcount += oldsize;
2773 	uep->ue_size = oldsize;
2774 	uep->ue_array = newarray;
2775 	uep->ue_bot = top + newsize + 1;
2776 
2777 	/*
2778 	 * insert this entry in front of the new entry list
2779 	 */
2780 	nuep = uep->ue_next;
2781 	uep->ue_next = newlist;
2782 	newlist = uep;
2783     }
2784 
2785     curhead->uh_entry = newlist;
2786     curhead->uh_flags = new_flags;
2787     if ((old_flags & UH_EMPTYBUF) && BUFEMPTY())
2788 	curbuf->b_ml.ml_flags |= ML_EMPTY;
2789     if (old_flags & UH_CHANGED)
2790 	changed();
2791     else
2792 #ifdef FEAT_NETBEANS_INTG
2793 	/* per netbeans undo rules, keep it as modified */
2794 	if (!isNetbeansModified(curbuf))
2795 #endif
2796 	unchanged(curbuf, FALSE);
2797 
2798     /*
2799      * restore marks from before undo/redo
2800      */
2801     for (i = 0; i < NMARKS; ++i)
2802     {
2803 	if (curhead->uh_namedm[i].lnum != 0)
2804 	    curbuf->b_namedm[i] = curhead->uh_namedm[i];
2805 	if (namedm[i].lnum != 0)
2806 	    curhead->uh_namedm[i] = namedm[i];
2807 	else
2808 	    curhead->uh_namedm[i].lnum = 0;
2809     }
2810     if (curhead->uh_visual.vi_start.lnum != 0)
2811     {
2812 	curbuf->b_visual = curhead->uh_visual;
2813 	curhead->uh_visual = visualinfo;
2814     }
2815 
2816     /*
2817      * If the cursor is only off by one line, put it at the same position as
2818      * before starting the change (for the "o" command).
2819      * Otherwise the cursor should go to the first undone line.
2820      */
2821     if (curhead->uh_cursor.lnum + 1 == curwin->w_cursor.lnum
2822 						 && curwin->w_cursor.lnum > 1)
2823 	--curwin->w_cursor.lnum;
2824     if (curwin->w_cursor.lnum <= curbuf->b_ml.ml_line_count)
2825     {
2826 	if (curhead->uh_cursor.lnum == curwin->w_cursor.lnum)
2827 	{
2828 	    curwin->w_cursor.col = curhead->uh_cursor.col;
2829 #ifdef FEAT_VIRTUALEDIT
2830 	    if (virtual_active() && curhead->uh_cursor_vcol >= 0)
2831 		coladvance((colnr_T)curhead->uh_cursor_vcol);
2832 	    else
2833 		curwin->w_cursor.coladd = 0;
2834 #endif
2835 	}
2836 	else
2837 	    beginline(BL_SOL | BL_FIX);
2838     }
2839     else
2840     {
2841 	/* We get here with the current cursor line being past the end (eg
2842 	 * after adding lines at the end of the file, and then undoing it).
2843 	 * check_cursor() will move the cursor to the last line.  Move it to
2844 	 * the first column here. */
2845 	curwin->w_cursor.col = 0;
2846 #ifdef FEAT_VIRTUALEDIT
2847 	curwin->w_cursor.coladd = 0;
2848 #endif
2849     }
2850 
2851     /* Make sure the cursor is on an existing line and column. */
2852     check_cursor();
2853 
2854     /* Remember where we are for "g-" and ":earlier 10s". */
2855     curbuf->b_u_seq_cur = curhead->uh_seq;
2856     if (undo)
2857 	/* We are below the previous undo.  However, to make ":earlier 1s"
2858 	 * work we compute this as being just above the just undone change. */
2859 	--curbuf->b_u_seq_cur;
2860 
2861     /* Remember where we are for ":earlier 1f" and ":later 1f". */
2862     if (curhead->uh_save_nr != 0)
2863     {
2864 	if (undo)
2865 	    curbuf->b_u_save_nr_cur = curhead->uh_save_nr - 1;
2866 	else
2867 	    curbuf->b_u_save_nr_cur = curhead->uh_save_nr;
2868     }
2869 
2870     /* The timestamp can be the same for multiple changes, just use the one of
2871      * the undone/redone change. */
2872     curbuf->b_u_time_cur = curhead->uh_time;
2873 
2874 #ifdef FEAT_AUTOCMD
2875     unblock_autocmds();
2876 #endif
2877 #ifdef U_DEBUG
2878     u_check(FALSE);
2879 #endif
2880 }
2881 
2882 /*
2883  * If we deleted or added lines, report the number of less/more lines.
2884  * Otherwise, report the number of changes (this may be incorrect
2885  * in some cases, but it's better than nothing).
2886  */
2887     static void
2888 u_undo_end(
2889     int		did_undo,	/* just did an undo */
2890     int		absolute)	/* used ":undo N" */
2891 {
2892     char	*msgstr;
2893     u_header_T	*uhp;
2894     char_u	msgbuf[80];
2895 
2896 #ifdef FEAT_FOLDING
2897     if ((fdo_flags & FDO_UNDO) && KeyTyped)
2898 	foldOpenCursor();
2899 #endif
2900 
2901     if (global_busy	    /* no messages now, wait until global is finished */
2902 	    || !messaging())  /* 'lazyredraw' set, don't do messages now */
2903 	return;
2904 
2905     if (curbuf->b_ml.ml_flags & ML_EMPTY)
2906 	--u_newcount;
2907 
2908     u_oldcount -= u_newcount;
2909     if (u_oldcount == -1)
2910 	msgstr = N_("more line");
2911     else if (u_oldcount < 0)
2912 	msgstr = N_("more lines");
2913     else if (u_oldcount == 1)
2914 	msgstr = N_("line less");
2915     else if (u_oldcount > 1)
2916 	msgstr = N_("fewer lines");
2917     else
2918     {
2919 	u_oldcount = u_newcount;
2920 	if (u_newcount == 1)
2921 	    msgstr = N_("change");
2922 	else
2923 	    msgstr = N_("changes");
2924     }
2925 
2926     if (curbuf->b_u_curhead != NULL)
2927     {
2928 	/* For ":undo N" we prefer a "after #N" message. */
2929 	if (absolute && curbuf->b_u_curhead->uh_next.ptr != NULL)
2930 	{
2931 	    uhp = curbuf->b_u_curhead->uh_next.ptr;
2932 	    did_undo = FALSE;
2933 	}
2934 	else if (did_undo)
2935 	    uhp = curbuf->b_u_curhead;
2936 	else
2937 	    uhp = curbuf->b_u_curhead->uh_next.ptr;
2938     }
2939     else
2940 	uhp = curbuf->b_u_newhead;
2941 
2942     if (uhp == NULL)
2943 	*msgbuf = NUL;
2944     else
2945 	u_add_time(msgbuf, sizeof(msgbuf), uhp->uh_time);
2946 
2947 #ifdef FEAT_CONCEAL
2948     {
2949 	win_T	*wp;
2950 
2951 	FOR_ALL_WINDOWS(wp)
2952 	{
2953 	    if (wp->w_buffer == curbuf && wp->w_p_cole > 0)
2954 		redraw_win_later(wp, NOT_VALID);
2955 	}
2956     }
2957 #endif
2958 
2959     smsg((char_u *)_("%ld %s; %s #%ld  %s"),
2960 	    u_oldcount < 0 ? -u_oldcount : u_oldcount,
2961 	    _(msgstr),
2962 	    did_undo ? _("before") : _("after"),
2963 	    uhp == NULL ? 0L : uhp->uh_seq,
2964 	    msgbuf);
2965 }
2966 
2967 /*
2968  * u_sync: stop adding to the current entry list
2969  */
2970     void
2971 u_sync(
2972     int	    force)	/* Also sync when no_u_sync is set. */
2973 {
2974     /* Skip it when already synced or syncing is disabled. */
2975     if (curbuf->b_u_synced || (!force && no_u_sync > 0))
2976 	return;
2977 #if defined(FEAT_XIM) && defined(FEAT_GUI_GTK)
2978     if (im_is_preediting())
2979 	return;		    /* XIM is busy, don't break an undo sequence */
2980 #endif
2981     if (get_undolevel() < 0)
2982 	curbuf->b_u_synced = TRUE;  /* no entries, nothing to do */
2983     else
2984     {
2985 	u_getbot();		    /* compute ue_bot of previous u_save */
2986 	curbuf->b_u_curhead = NULL;
2987     }
2988 }
2989 
2990 /*
2991  * ":undolist": List the leafs of the undo tree
2992  */
2993     void
2994 ex_undolist(exarg_T *eap UNUSED)
2995 {
2996     garray_T	ga;
2997     u_header_T	*uhp;
2998     int		mark;
2999     int		nomark;
3000     int		changes = 1;
3001     int		i;
3002 
3003     /*
3004      * 1: walk the tree to find all leafs, put the info in "ga".
3005      * 2: sort the lines
3006      * 3: display the list
3007      */
3008     mark = ++lastmark;
3009     nomark = ++lastmark;
3010     ga_init2(&ga, (int)sizeof(char *), 20);
3011 
3012     uhp = curbuf->b_u_oldhead;
3013     while (uhp != NULL)
3014     {
3015 	if (uhp->uh_prev.ptr == NULL && uhp->uh_walk != nomark
3016 						      && uhp->uh_walk != mark)
3017 	{
3018 	    if (ga_grow(&ga, 1) == FAIL)
3019 		break;
3020 	    vim_snprintf((char *)IObuff, IOSIZE, "%6ld %7ld  ",
3021 							uhp->uh_seq, changes);
3022 	    u_add_time(IObuff + STRLEN(IObuff), IOSIZE - STRLEN(IObuff),
3023 								uhp->uh_time);
3024 	    if (uhp->uh_save_nr > 0)
3025 	    {
3026 		while (STRLEN(IObuff) < 33)
3027 		    STRCAT(IObuff, " ");
3028 		vim_snprintf_add((char *)IObuff, IOSIZE,
3029 						   "  %3ld", uhp->uh_save_nr);
3030 	    }
3031 	    ((char_u **)(ga.ga_data))[ga.ga_len++] = vim_strsave(IObuff);
3032 	}
3033 
3034 	uhp->uh_walk = mark;
3035 
3036 	/* go down in the tree if we haven't been there */
3037 	if (uhp->uh_prev.ptr != NULL && uhp->uh_prev.ptr->uh_walk != nomark
3038 					 && uhp->uh_prev.ptr->uh_walk != mark)
3039 	{
3040 	    uhp = uhp->uh_prev.ptr;
3041 	    ++changes;
3042 	}
3043 
3044 	/* go to alternate branch if we haven't been there */
3045 	else if (uhp->uh_alt_next.ptr != NULL
3046 		&& uhp->uh_alt_next.ptr->uh_walk != nomark
3047 		&& uhp->uh_alt_next.ptr->uh_walk != mark)
3048 	    uhp = uhp->uh_alt_next.ptr;
3049 
3050 	/* go up in the tree if we haven't been there and we are at the
3051 	 * start of alternate branches */
3052 	else if (uhp->uh_next.ptr != NULL && uhp->uh_alt_prev.ptr == NULL
3053 		&& uhp->uh_next.ptr->uh_walk != nomark
3054 		&& uhp->uh_next.ptr->uh_walk != mark)
3055 	{
3056 	    uhp = uhp->uh_next.ptr;
3057 	    --changes;
3058 	}
3059 
3060 	else
3061 	{
3062 	    /* need to backtrack; mark this node as done */
3063 	    uhp->uh_walk = nomark;
3064 	    if (uhp->uh_alt_prev.ptr != NULL)
3065 		uhp = uhp->uh_alt_prev.ptr;
3066 	    else
3067 	    {
3068 		uhp = uhp->uh_next.ptr;
3069 		--changes;
3070 	    }
3071 	}
3072     }
3073 
3074     if (ga.ga_len == 0)
3075 	MSG(_("Nothing to undo"));
3076     else
3077     {
3078 	sort_strings((char_u **)ga.ga_data, ga.ga_len);
3079 
3080 	msg_start();
3081 	msg_puts_attr((char_u *)_("number changes  when               saved"),
3082 							      HL_ATTR(HLF_T));
3083 	for (i = 0; i < ga.ga_len && !got_int; ++i)
3084 	{
3085 	    msg_putchar('\n');
3086 	    if (got_int)
3087 		break;
3088 	    msg_puts(((char_u **)ga.ga_data)[i]);
3089 	}
3090 	msg_end();
3091 
3092 	ga_clear_strings(&ga);
3093     }
3094 }
3095 
3096 /*
3097  * Put the timestamp of an undo header in "buf[buflen]" in a nice format.
3098  */
3099     static void
3100 u_add_time(char_u *buf, size_t buflen, time_t tt)
3101 {
3102 #ifdef HAVE_STRFTIME
3103     struct tm	*curtime;
3104 
3105     if (vim_time() - tt >= 100)
3106     {
3107 	curtime = localtime(&tt);
3108 	if (vim_time() - tt < (60L * 60L * 12L))
3109 	    /* within 12 hours */
3110 	    (void)strftime((char *)buf, buflen, "%H:%M:%S", curtime);
3111 	else
3112 	    /* longer ago */
3113 	    (void)strftime((char *)buf, buflen, "%Y/%m/%d %H:%M:%S", curtime);
3114     }
3115     else
3116 #endif
3117 	vim_snprintf((char *)buf, buflen, _("%ld seconds ago"),
3118 						      (long)(vim_time() - tt));
3119 }
3120 
3121 /*
3122  * ":undojoin": continue adding to the last entry list
3123  */
3124     void
3125 ex_undojoin(exarg_T *eap UNUSED)
3126 {
3127     if (curbuf->b_u_newhead == NULL)
3128 	return;		    /* nothing changed before */
3129     if (curbuf->b_u_curhead != NULL)
3130     {
3131 	EMSG(_("E790: undojoin is not allowed after undo"));
3132 	return;
3133     }
3134     if (!curbuf->b_u_synced)
3135 	return;		    /* already unsynced */
3136     if (get_undolevel() < 0)
3137 	return;		    /* no entries, nothing to do */
3138     else
3139 	/* Append next change to the last entry */
3140 	curbuf->b_u_synced = FALSE;
3141 }
3142 
3143 /*
3144  * Called after writing or reloading the file and setting b_changed to FALSE.
3145  * Now an undo means that the buffer is modified.
3146  */
3147     void
3148 u_unchanged(buf_T *buf)
3149 {
3150     u_unch_branch(buf->b_u_oldhead);
3151     buf->b_did_warn = FALSE;
3152 }
3153 
3154 /*
3155  * After reloading a buffer which was saved for 'undoreload': Find the first
3156  * line that was changed and set the cursor there.
3157  */
3158     void
3159 u_find_first_changed(void)
3160 {
3161     u_header_T	*uhp = curbuf->b_u_newhead;
3162     u_entry_T   *uep;
3163     linenr_T	lnum;
3164 
3165     if (curbuf->b_u_curhead != NULL || uhp == NULL)
3166 	return;  /* undid something in an autocmd? */
3167 
3168     /* Check that the last undo block was for the whole file. */
3169     uep = uhp->uh_entry;
3170     if (uep->ue_top != 0 || uep->ue_bot != 0)
3171 	return;
3172 
3173     for (lnum = 1; lnum < curbuf->b_ml.ml_line_count
3174 					      && lnum <= uep->ue_size; ++lnum)
3175 	if (STRCMP(ml_get_buf(curbuf, lnum, FALSE),
3176 						uep->ue_array[lnum - 1]) != 0)
3177 	{
3178 	    CLEAR_POS(&(uhp->uh_cursor));
3179 	    uhp->uh_cursor.lnum = lnum;
3180 	    return;
3181 	}
3182     if (curbuf->b_ml.ml_line_count != uep->ue_size)
3183     {
3184 	/* lines added or deleted at the end, put the cursor there */
3185 	CLEAR_POS(&(uhp->uh_cursor));
3186 	uhp->uh_cursor.lnum = lnum;
3187     }
3188 }
3189 
3190 /*
3191  * Increase the write count, store it in the last undo header, what would be
3192  * used for "u".
3193  */
3194     void
3195 u_update_save_nr(buf_T *buf)
3196 {
3197     u_header_T	*uhp;
3198 
3199     ++buf->b_u_save_nr_last;
3200     buf->b_u_save_nr_cur = buf->b_u_save_nr_last;
3201     uhp = buf->b_u_curhead;
3202     if (uhp != NULL)
3203 	uhp = uhp->uh_next.ptr;
3204     else
3205 	uhp = buf->b_u_newhead;
3206     if (uhp != NULL)
3207 	uhp->uh_save_nr = buf->b_u_save_nr_last;
3208 }
3209 
3210     static void
3211 u_unch_branch(u_header_T *uhp)
3212 {
3213     u_header_T	*uh;
3214 
3215     for (uh = uhp; uh != NULL; uh = uh->uh_prev.ptr)
3216     {
3217 	uh->uh_flags |= UH_CHANGED;
3218 	if (uh->uh_alt_next.ptr != NULL)
3219 	    u_unch_branch(uh->uh_alt_next.ptr);	    /* recursive */
3220     }
3221 }
3222 
3223 /*
3224  * Get pointer to last added entry.
3225  * If it's not valid, give an error message and return NULL.
3226  */
3227     static u_entry_T *
3228 u_get_headentry(void)
3229 {
3230     if (curbuf->b_u_newhead == NULL || curbuf->b_u_newhead->uh_entry == NULL)
3231     {
3232 	IEMSG(_("E439: undo list corrupt"));
3233 	return NULL;
3234     }
3235     return curbuf->b_u_newhead->uh_entry;
3236 }
3237 
3238 /*
3239  * u_getbot(): compute the line number of the previous u_save
3240  *		It is called only when b_u_synced is FALSE.
3241  */
3242     static void
3243 u_getbot(void)
3244 {
3245     u_entry_T	*uep;
3246     linenr_T	extra;
3247 
3248     uep = u_get_headentry();	/* check for corrupt undo list */
3249     if (uep == NULL)
3250 	return;
3251 
3252     uep = curbuf->b_u_newhead->uh_getbot_entry;
3253     if (uep != NULL)
3254     {
3255 	/*
3256 	 * the new ue_bot is computed from the number of lines that has been
3257 	 * inserted (0 - deleted) since calling u_save. This is equal to the
3258 	 * old line count subtracted from the current line count.
3259 	 */
3260 	extra = curbuf->b_ml.ml_line_count - uep->ue_lcount;
3261 	uep->ue_bot = uep->ue_top + uep->ue_size + 1 + extra;
3262 	if (uep->ue_bot < 1 || uep->ue_bot > curbuf->b_ml.ml_line_count)
3263 	{
3264 	    IEMSG(_("E440: undo line missing"));
3265 	    uep->ue_bot = uep->ue_top + 1;  /* assume all lines deleted, will
3266 					     * get all the old lines back
3267 					     * without deleting the current
3268 					     * ones */
3269 	}
3270 
3271 	curbuf->b_u_newhead->uh_getbot_entry = NULL;
3272     }
3273 
3274     curbuf->b_u_synced = TRUE;
3275 }
3276 
3277 /*
3278  * Free one header "uhp" and its entry list and adjust the pointers.
3279  */
3280     static void
3281 u_freeheader(
3282     buf_T	    *buf,
3283     u_header_T	    *uhp,
3284     u_header_T	    **uhpp)	/* if not NULL reset when freeing this header */
3285 {
3286     u_header_T	    *uhap;
3287 
3288     /* When there is an alternate redo list free that branch completely,
3289      * because we can never go there. */
3290     if (uhp->uh_alt_next.ptr != NULL)
3291 	u_freebranch(buf, uhp->uh_alt_next.ptr, uhpp);
3292 
3293     if (uhp->uh_alt_prev.ptr != NULL)
3294 	uhp->uh_alt_prev.ptr->uh_alt_next.ptr = NULL;
3295 
3296     /* Update the links in the list to remove the header. */
3297     if (uhp->uh_next.ptr == NULL)
3298 	buf->b_u_oldhead = uhp->uh_prev.ptr;
3299     else
3300 	uhp->uh_next.ptr->uh_prev.ptr = uhp->uh_prev.ptr;
3301 
3302     if (uhp->uh_prev.ptr == NULL)
3303 	buf->b_u_newhead = uhp->uh_next.ptr;
3304     else
3305 	for (uhap = uhp->uh_prev.ptr; uhap != NULL;
3306 						 uhap = uhap->uh_alt_next.ptr)
3307 	    uhap->uh_next.ptr = uhp->uh_next.ptr;
3308 
3309     u_freeentries(buf, uhp, uhpp);
3310 }
3311 
3312 /*
3313  * Free an alternate branch and any following alternate branches.
3314  */
3315     static void
3316 u_freebranch(
3317     buf_T	    *buf,
3318     u_header_T	    *uhp,
3319     u_header_T	    **uhpp)	/* if not NULL reset when freeing this header */
3320 {
3321     u_header_T	    *tofree, *next;
3322 
3323     /* If this is the top branch we may need to use u_freeheader() to update
3324      * all the pointers. */
3325     if (uhp == buf->b_u_oldhead)
3326     {
3327 	while (buf->b_u_oldhead != NULL)
3328 	    u_freeheader(buf, buf->b_u_oldhead, uhpp);
3329 	return;
3330     }
3331 
3332     if (uhp->uh_alt_prev.ptr != NULL)
3333 	uhp->uh_alt_prev.ptr->uh_alt_next.ptr = NULL;
3334 
3335     next = uhp;
3336     while (next != NULL)
3337     {
3338 	tofree = next;
3339 	if (tofree->uh_alt_next.ptr != NULL)
3340 	    u_freebranch(buf, tofree->uh_alt_next.ptr, uhpp);   /* recursive */
3341 	next = tofree->uh_prev.ptr;
3342 	u_freeentries(buf, tofree, uhpp);
3343     }
3344 }
3345 
3346 /*
3347  * Free all the undo entries for one header and the header itself.
3348  * This means that "uhp" is invalid when returning.
3349  */
3350     static void
3351 u_freeentries(
3352     buf_T	    *buf,
3353     u_header_T	    *uhp,
3354     u_header_T	    **uhpp)	/* if not NULL reset when freeing this header */
3355 {
3356     u_entry_T	    *uep, *nuep;
3357 
3358     /* Check for pointers to the header that become invalid now. */
3359     if (buf->b_u_curhead == uhp)
3360 	buf->b_u_curhead = NULL;
3361     if (buf->b_u_newhead == uhp)
3362 	buf->b_u_newhead = NULL;  /* freeing the newest entry */
3363     if (uhpp != NULL && uhp == *uhpp)
3364 	*uhpp = NULL;
3365 
3366     for (uep = uhp->uh_entry; uep != NULL; uep = nuep)
3367     {
3368 	nuep = uep->ue_next;
3369 	u_freeentry(uep, uep->ue_size);
3370     }
3371 
3372 #ifdef U_DEBUG
3373     uhp->uh_magic = 0;
3374 #endif
3375     vim_free((char_u *)uhp);
3376     --buf->b_u_numhead;
3377 }
3378 
3379 /*
3380  * free entry 'uep' and 'n' lines in uep->ue_array[]
3381  */
3382     static void
3383 u_freeentry(u_entry_T *uep, long n)
3384 {
3385     while (n > 0)
3386 	vim_free(uep->ue_array[--n]);
3387     vim_free((char_u *)uep->ue_array);
3388 #ifdef U_DEBUG
3389     uep->ue_magic = 0;
3390 #endif
3391     vim_free((char_u *)uep);
3392 }
3393 
3394 /*
3395  * invalidate the undo buffer; called when storage has already been released
3396  */
3397     void
3398 u_clearall(buf_T *buf)
3399 {
3400     buf->b_u_newhead = buf->b_u_oldhead = buf->b_u_curhead = NULL;
3401     buf->b_u_synced = TRUE;
3402     buf->b_u_numhead = 0;
3403     buf->b_u_line_ptr = NULL;
3404     buf->b_u_line_lnum = 0;
3405 }
3406 
3407 /*
3408  * save the line "lnum" for the "U" command
3409  */
3410     void
3411 u_saveline(linenr_T lnum)
3412 {
3413     if (lnum == curbuf->b_u_line_lnum)	    /* line is already saved */
3414 	return;
3415     if (lnum < 1 || lnum > curbuf->b_ml.ml_line_count) /* should never happen */
3416 	return;
3417     u_clearline();
3418     curbuf->b_u_line_lnum = lnum;
3419     if (curwin->w_cursor.lnum == lnum)
3420 	curbuf->b_u_line_colnr = curwin->w_cursor.col;
3421     else
3422 	curbuf->b_u_line_colnr = 0;
3423     if ((curbuf->b_u_line_ptr = u_save_line(lnum)) == NULL)
3424 	do_outofmem_msg((long_u)0);
3425 }
3426 
3427 /*
3428  * clear the line saved for the "U" command
3429  * (this is used externally for crossing a line while in insert mode)
3430  */
3431     void
3432 u_clearline(void)
3433 {
3434     if (curbuf->b_u_line_ptr != NULL)
3435     {
3436 	vim_free(curbuf->b_u_line_ptr);
3437 	curbuf->b_u_line_ptr = NULL;
3438 	curbuf->b_u_line_lnum = 0;
3439     }
3440 }
3441 
3442 /*
3443  * Implementation of the "U" command.
3444  * Differentiation from vi: "U" can be undone with the next "U".
3445  * We also allow the cursor to be in another line.
3446  * Careful: may trigger autocommands that reload the buffer.
3447  */
3448     void
3449 u_undoline(void)
3450 {
3451     colnr_T t;
3452     char_u  *oldp;
3453 
3454     if (undo_off)
3455 	return;
3456 
3457     if (curbuf->b_u_line_ptr == NULL
3458 			|| curbuf->b_u_line_lnum > curbuf->b_ml.ml_line_count)
3459     {
3460 	beep_flush();
3461 	return;
3462     }
3463 
3464     /* first save the line for the 'u' command */
3465     if (u_savecommon(curbuf->b_u_line_lnum - 1,
3466 		       curbuf->b_u_line_lnum + 1, (linenr_T)0, FALSE) == FAIL)
3467 	return;
3468     oldp = u_save_line(curbuf->b_u_line_lnum);
3469     if (oldp == NULL)
3470     {
3471 	do_outofmem_msg((long_u)0);
3472 	return;
3473     }
3474     ml_replace(curbuf->b_u_line_lnum, curbuf->b_u_line_ptr, TRUE);
3475     changed_bytes(curbuf->b_u_line_lnum, 0);
3476     vim_free(curbuf->b_u_line_ptr);
3477     curbuf->b_u_line_ptr = oldp;
3478 
3479     t = curbuf->b_u_line_colnr;
3480     if (curwin->w_cursor.lnum == curbuf->b_u_line_lnum)
3481 	curbuf->b_u_line_colnr = curwin->w_cursor.col;
3482     curwin->w_cursor.col = t;
3483     curwin->w_cursor.lnum = curbuf->b_u_line_lnum;
3484     check_cursor_col();
3485 }
3486 
3487 /*
3488  * Free all allocated memory blocks for the buffer 'buf'.
3489  */
3490     void
3491 u_blockfree(buf_T *buf)
3492 {
3493     while (buf->b_u_oldhead != NULL)
3494 	u_freeheader(buf, buf->b_u_oldhead, NULL);
3495     vim_free(buf->b_u_line_ptr);
3496 }
3497 
3498 /*
3499  * u_save_line(): allocate memory and copy line 'lnum' into it.
3500  * Returns NULL when out of memory.
3501  */
3502     static char_u *
3503 u_save_line(linenr_T lnum)
3504 {
3505     return vim_strsave(ml_get(lnum));
3506 }
3507 
3508 /*
3509  * Check if the 'modified' flag is set, or 'ff' has changed (only need to
3510  * check the first character, because it can only be "dos", "unix" or "mac").
3511  * "nofile" and "scratch" type buffers are considered to always be unchanged.
3512  */
3513     int
3514 bufIsChanged(buf_T *buf)
3515 {
3516     return
3517 #ifdef FEAT_QUICKFIX
3518 	    !bt_dontwrite(buf) &&
3519 #endif
3520 	    (buf->b_changed || file_ff_differs(buf, TRUE));
3521 }
3522 
3523     int
3524 curbufIsChanged(void)
3525 {
3526     return
3527 #ifdef FEAT_QUICKFIX
3528 	!bt_dontwrite(curbuf) &&
3529 #endif
3530 	(curbuf->b_changed || file_ff_differs(curbuf, TRUE));
3531 }
3532 
3533 #if defined(FEAT_EVAL) || defined(PROTO)
3534 /*
3535  * For undotree(): Append the list of undo blocks at "first_uhp" to "list".
3536  * Recursive.
3537  */
3538     void
3539 u_eval_tree(u_header_T *first_uhp, list_T *list)
3540 {
3541     u_header_T  *uhp = first_uhp;
3542     dict_T	*dict;
3543 
3544     while (uhp != NULL)
3545     {
3546 	dict = dict_alloc();
3547 	if (dict == NULL)
3548 	    return;
3549 	dict_add_nr_str(dict, "seq", uhp->uh_seq, NULL);
3550 	dict_add_nr_str(dict, "time", (long)uhp->uh_time, NULL);
3551 	if (uhp == curbuf->b_u_newhead)
3552 	    dict_add_nr_str(dict, "newhead", 1, NULL);
3553 	if (uhp == curbuf->b_u_curhead)
3554 	    dict_add_nr_str(dict, "curhead", 1, NULL);
3555 	if (uhp->uh_save_nr > 0)
3556 	    dict_add_nr_str(dict, "save", uhp->uh_save_nr, NULL);
3557 
3558 	if (uhp->uh_alt_next.ptr != NULL)
3559 	{
3560 	    list_T	*alt_list = list_alloc();
3561 
3562 	    if (alt_list != NULL)
3563 	    {
3564 		/* Recursive call to add alternate undo tree. */
3565 		u_eval_tree(uhp->uh_alt_next.ptr, alt_list);
3566 		dict_add_list(dict, "alt", alt_list);
3567 	    }
3568 	}
3569 
3570 	list_append_dict(list, dict);
3571 	uhp = uhp->uh_prev.ptr;
3572     }
3573 }
3574 #endif
3575