xref: /freebsd/contrib/less/search.c (revision eb69d1f144a6fcc765d1b9d44a5ae8082353e70b)
1 /*
2  * Copyright (C) 1984-2017  Mark Nudelman
3  *
4  * You may distribute under the terms of either the GNU General Public
5  * License or the Less License, as specified in the README file.
6  *
7  * For more information, see the README file.
8  */
9 
10 
11 /*
12  * Routines to search a file for a pattern.
13  */
14 
15 #include "less.h"
16 #include "position.h"
17 #include "charset.h"
18 
19 #define	MINPOS(a,b)	(((a) < (b)) ? (a) : (b))
20 #define	MAXPOS(a,b)	(((a) > (b)) ? (a) : (b))
21 
22 extern int sigs;
23 extern int how_search;
24 extern int caseless;
25 extern int linenums;
26 extern int sc_height;
27 extern int jump_sline;
28 extern int bs_mode;
29 extern int ctldisp;
30 extern int status_col;
31 extern void *ml_search;
32 extern POSITION start_attnpos;
33 extern POSITION end_attnpos;
34 extern int utf_mode;
35 extern int screen_trashed;
36 #if HILITE_SEARCH
37 extern int hilite_search;
38 extern int size_linebuf;
39 extern int squished;
40 extern int can_goto_line;
41 static int hide_hilite;
42 static POSITION prep_startpos;
43 static POSITION prep_endpos;
44 static int is_caseless;
45 static int is_ucase_pattern;
46 
47 /*
48  * Structures for maintaining a set of ranges for hilites and filtered-out
49  * lines. Each range is stored as a node within a red-black tree, and we
50  * try to extend existing ranges (without creating overlaps) rather than
51  * create new nodes if possible. We remember the last node found by a
52  * search for constant-time lookup if the next search is near enough to
53  * the previous. To aid that, we overlay a secondary doubly-linked list
54  * on top of the red-black tree so we can find the preceding/succeeding
55  * nodes also in constant time.
56  *
57  * Each node is allocated from a series of pools, each pool double the size
58  * of the previous (for amortised constant time allocation). Since our only
59  * tree operations are clear and node insertion, not node removal, we don't
60  * need to maintain a usage bitmap or freelist and can just return nodes
61  * from the pool in-order until capacity is reached.
62  */
63 struct hilite
64 {
65 	POSITION hl_startpos;
66 	POSITION hl_endpos;
67 };
68 struct hilite_node
69 {
70 	struct hilite_node *parent;
71 	struct hilite_node *left;
72 	struct hilite_node *right;
73 	struct hilite_node *prev;
74 	struct hilite_node *next;
75 	int red;
76 	struct hilite r;
77 };
78 struct hilite_storage
79 {
80 	int capacity;
81 	int used;
82 	struct hilite_storage *next;
83 	struct hilite_node *nodes;
84 };
85 struct hilite_tree
86 {
87 	struct hilite_storage *first;
88 	struct hilite_storage *current;
89 	struct hilite_node *root;
90 	struct hilite_node *lookaside;
91 };
92 #define HILITE_INITIALIZER() { NULL, NULL, NULL, NULL }
93 #define HILITE_LOOKASIDE_STEPS 2
94 
95 static struct hilite_tree hilite_anchor = HILITE_INITIALIZER();
96 static struct hilite_tree filter_anchor = HILITE_INITIALIZER();
97 
98 #endif
99 
100 /*
101  * These are the static variables that represent the "remembered"
102  * search pattern and filter pattern.
103  */
104 struct pattern_info {
105 	PATTERN_TYPE compiled;
106 	char* text;
107 	int search_type;
108 };
109 
110 #if NO_REGEX
111 #define info_compiled(info) ((void*)0)
112 #else
113 #define info_compiled(info) ((info)->compiled)
114 #endif
115 
116 static struct pattern_info search_info;
117 static struct pattern_info filter_info;
118 
119 /*
120  * Are there any uppercase letters in this string?
121  */
122 	static int
123 is_ucase(str)
124 	char *str;
125 {
126 	char *str_end = str + strlen(str);
127 	LWCHAR ch;
128 
129 	while (str < str_end)
130 	{
131 		ch = step_char(&str, +1, str_end);
132 		if (IS_UPPER(ch))
133 			return (1);
134 	}
135 	return (0);
136 }
137 
138 /*
139  * Compile and save a search pattern.
140  */
141 	static int
142 set_pattern(info, pattern, search_type)
143 	struct pattern_info *info;
144 	char *pattern;
145 	int search_type;
146 {
147 #if !NO_REGEX
148 	if (pattern == NULL)
149 		CLEAR_PATTERN(info->compiled);
150 	else if (compile_pattern(pattern, search_type, &info->compiled) < 0)
151 		return -1;
152 #endif
153 	/* Pattern compiled successfully; save the text too. */
154 	if (info->text != NULL)
155 		free(info->text);
156 	info->text = NULL;
157 	if (pattern != NULL)
158 	{
159 		info->text = (char *) ecalloc(1, strlen(pattern)+1);
160 		strcpy(info->text, pattern);
161 	}
162 	info->search_type = search_type;
163 
164 	/*
165 	 * Ignore case if -I is set OR
166 	 * -i is set AND the pattern is all lowercase.
167 	 */
168 	is_ucase_pattern = is_ucase(pattern);
169 	if (is_ucase_pattern && caseless != OPT_ONPLUS)
170 		is_caseless = 0;
171 	else
172 		is_caseless = caseless;
173 	return 0;
174 }
175 
176 /*
177  * Discard a saved pattern.
178  */
179 	static void
180 clear_pattern(info)
181 	struct pattern_info *info;
182 {
183 	if (info->text != NULL)
184 		free(info->text);
185 	info->text = NULL;
186 #if !NO_REGEX
187 	uncompile_pattern(&info->compiled);
188 #endif
189 }
190 
191 /*
192  * Initialize saved pattern to nothing.
193  */
194 	static void
195 init_pattern(info)
196 	struct pattern_info *info;
197 {
198 	CLEAR_PATTERN(info->compiled);
199 	info->text = NULL;
200 	info->search_type = 0;
201 }
202 
203 /*
204  * Initialize search variables.
205  */
206 	public void
207 init_search()
208 {
209 	init_pattern(&search_info);
210 	init_pattern(&filter_info);
211 }
212 
213 /*
214  * Determine which text conversions to perform before pattern matching.
215  */
216 	static int
217 get_cvt_ops()
218 {
219 	int ops = 0;
220 	if (is_caseless || bs_mode == BS_SPECIAL)
221 	{
222 		if (is_caseless)
223 			ops |= CVT_TO_LC;
224 		if (bs_mode == BS_SPECIAL)
225 			ops |= CVT_BS;
226 		if (bs_mode != BS_CONTROL)
227 			ops |= CVT_CRLF;
228 	} else if (bs_mode != BS_CONTROL)
229 	{
230 		ops |= CVT_CRLF;
231 	}
232 	if (ctldisp == OPT_ONPLUS)
233 		ops |= CVT_ANSI;
234 	return (ops);
235 }
236 
237 /*
238  * Is there a previous (remembered) search pattern?
239  */
240 	static int
241 prev_pattern(info)
242 	struct pattern_info *info;
243 {
244 #if !NO_REGEX
245 	if ((info->search_type & SRCH_NO_REGEX) == 0)
246 		return (!is_null_pattern(info->compiled));
247 #endif
248 	return (info->text != NULL);
249 }
250 
251 #if HILITE_SEARCH
252 /*
253  * Repaint the hilites currently displayed on the screen.
254  * Repaint each line which contains highlighted text.
255  * If on==0, force all hilites off.
256  */
257 	public void
258 repaint_hilite(on)
259 	int on;
260 {
261 	int sindex;
262 	POSITION pos;
263 	int save_hide_hilite;
264 
265 	if (squished)
266 		repaint();
267 
268 	save_hide_hilite = hide_hilite;
269 	if (!on)
270 	{
271 		if (hide_hilite)
272 			return;
273 		hide_hilite = 1;
274 	}
275 
276 	if (!can_goto_line)
277 	{
278 		repaint();
279 		hide_hilite = save_hide_hilite;
280 		return;
281 	}
282 
283 	for (sindex = TOP;  sindex < TOP + sc_height-1;  sindex++)
284 	{
285 		pos = position(sindex);
286 		if (pos == NULL_POSITION)
287 			continue;
288 		(void) forw_line(pos);
289 		goto_line(sindex);
290 		put_line();
291 	}
292 	lower_left();
293 	hide_hilite = save_hide_hilite;
294 }
295 
296 /*
297  * Clear the attn hilite.
298  */
299 	public void
300 clear_attn()
301 {
302 	int sindex;
303 	POSITION old_start_attnpos;
304 	POSITION old_end_attnpos;
305 	POSITION pos;
306 	POSITION epos;
307 	int moved = 0;
308 
309 	if (start_attnpos == NULL_POSITION)
310 		return;
311 	old_start_attnpos = start_attnpos;
312 	old_end_attnpos = end_attnpos;
313 	start_attnpos = end_attnpos = NULL_POSITION;
314 
315 	if (!can_goto_line)
316 	{
317 		repaint();
318 		return;
319 	}
320 	if (squished)
321 		repaint();
322 
323 	for (sindex = TOP;  sindex < TOP + sc_height-1;  sindex++)
324 	{
325 		pos = position(sindex);
326 		if (pos == NULL_POSITION)
327 			continue;
328 		epos = position(sindex+1);
329 		if (pos <= old_end_attnpos &&
330 		     (epos == NULL_POSITION || epos > old_start_attnpos))
331 		{
332 			(void) forw_line(pos);
333 			goto_line(sindex);
334 			put_line();
335 			moved = 1;
336 		}
337 	}
338 	if (moved)
339 		lower_left();
340 }
341 #endif
342 
343 /*
344  * Hide search string highlighting.
345  */
346 	public void
347 undo_search()
348 {
349 	if (!prev_pattern(&search_info))
350 	{
351 		if (hilite_anchor.first == NULL)
352 		{
353 			error("No previous regular expression", NULL_PARG);
354 			return;
355 		}
356 		clr_hilite(); /* Next time, hilite_anchor.first will be NULL. */
357 	}
358 	clear_pattern(&search_info);
359 #if HILITE_SEARCH
360 	hide_hilite = !hide_hilite;
361 	repaint_hilite(1);
362 #endif
363 }
364 
365 #if HILITE_SEARCH
366 /*
367  * Clear the hilite list.
368  */
369 	public void
370 clr_hlist(anchor)
371 	struct hilite_tree *anchor;
372 {
373 	struct hilite_storage *hls;
374 	struct hilite_storage *nexthls;
375 
376 	for (hls = anchor->first;  hls != NULL;  hls = nexthls)
377 	{
378 		nexthls = hls->next;
379 		free((void*)hls->nodes);
380 		free((void*)hls);
381 	}
382 	anchor->first = NULL;
383 	anchor->current = NULL;
384 	anchor->root = NULL;
385 
386 	anchor->lookaside = NULL;
387 
388 	prep_startpos = prep_endpos = NULL_POSITION;
389 }
390 
391 	public void
392 clr_hilite()
393 {
394 	clr_hlist(&hilite_anchor);
395 }
396 
397 	public void
398 clr_filter()
399 {
400 	clr_hlist(&filter_anchor);
401 }
402 
403 	struct hilite_node*
404 hlist_last(anchor)
405 	struct hilite_tree *anchor;
406 {
407 	struct hilite_node *n = anchor->root;
408 	while (n != NULL && n->right != NULL)
409 		n = n->right;
410 	return n;
411 }
412 
413 	struct hilite_node*
414 hlist_next(n)
415 	struct hilite_node *n;
416 {
417 	return n->next;
418 }
419 
420 	struct hilite_node*
421 hlist_prev(n)
422 	struct hilite_node *n;
423 {
424 	return n->prev;
425 }
426 
427 /*
428  * Find the node covering pos, or the node after it if no node covers it,
429  * or return NULL if pos is after the last range. Remember the found node,
430  * to speed up subsequent searches for the same or similar positions (if
431  * we return NULL, remember the last node.)
432  */
433 	struct hilite_node*
434 hlist_find(anchor, pos)
435 	struct hilite_tree *anchor;
436 	POSITION pos;
437 {
438 	struct hilite_node *n, *m;
439 
440 	if (anchor->lookaside)
441 	{
442 		int steps = 0;
443 		int hit = 0;
444 
445 		n = anchor->lookaside;
446 
447 		for (;;)
448 		{
449 			if (pos < n->r.hl_endpos)
450 			{
451 				if (n->prev == NULL || pos >= n->prev->r.hl_endpos)
452 				{
453 					hit = 1;
454 					break;
455 				}
456 			} else if (n->next == NULL)
457 			{
458 				n = NULL;
459 				hit = 1;
460 				break;
461 			}
462 
463 			/*
464 			 * If we don't find the right node within a small
465 			 * distance, don't keep doing a linear search!
466 			 */
467 			if (steps >= HILITE_LOOKASIDE_STEPS)
468 				break;
469 			steps++;
470 
471 			if (pos < n->r.hl_endpos)
472 				anchor->lookaside = n = n->prev;
473 			else
474 				anchor->lookaside = n = n->next;
475 		}
476 
477 		if (hit)
478 			return n;
479 	}
480 
481 	n = anchor->root;
482 	m = NULL;
483 
484 	while (n != NULL)
485 	{
486 		if (pos < n->r.hl_startpos)
487 		{
488 			if (n->left != NULL)
489 			{
490 				m = n;
491 				n = n->left;
492 				continue;
493 			}
494 			break;
495 		}
496 		if (pos >= n->r.hl_endpos)
497 		{
498 			if (n->right != NULL)
499 			{
500 				n = n->right;
501 				continue;
502 			}
503 			if (m != NULL)
504 			{
505 				n = m;
506 			} else
507 			{
508 				m = n;
509 				n = NULL;
510 			}
511 		}
512 		break;
513 	}
514 
515 	if (n != NULL)
516 		anchor->lookaside = n;
517 	else if (m != NULL)
518 		anchor->lookaside = m;
519 
520 	return n;
521 }
522 
523 /*
524  * Should any characters in a specified range be highlighted?
525  */
526 	static int
527 is_hilited_range(pos, epos)
528 	POSITION pos;
529 	POSITION epos;
530 {
531 	struct hilite_node *n = hlist_find(&hilite_anchor, pos);
532 	return (n != NULL && (epos == NULL_POSITION || epos > n->r.hl_startpos));
533 }
534 
535 /*
536  * Is a line "filtered" -- that is, should it be hidden?
537  */
538 	public int
539 is_filtered(pos)
540 	POSITION pos;
541 {
542 	struct hilite_node *n;
543 
544 	if (ch_getflags() & CH_HELPFILE)
545 		return (0);
546 
547 	n = hlist_find(&filter_anchor, pos);
548 	return (n != NULL && pos >= n->r.hl_startpos);
549 }
550 
551 /*
552  * If pos is hidden, return the next position which isn't, otherwise
553  * just return pos.
554  */
555 	public POSITION
556 next_unfiltered(pos)
557 	POSITION pos;
558 {
559 	struct hilite_node *n;
560 
561 	if (ch_getflags() & CH_HELPFILE)
562 		return (pos);
563 
564 	n = hlist_find(&filter_anchor, pos);
565 	while (n != NULL && pos >= n->r.hl_startpos)
566 	{
567 		pos = n->r.hl_endpos;
568 		n = n->next;
569 	}
570 	return (pos);
571 }
572 
573 /*
574  * If pos is hidden, return the previous position which isn't or 0 if
575  * we're filtered right to the beginning, otherwise just return pos.
576  */
577 	public POSITION
578 prev_unfiltered(pos)
579 	POSITION pos;
580 {
581 	struct hilite_node *n;
582 
583 	if (ch_getflags() & CH_HELPFILE)
584 		return (pos);
585 
586 	n = hlist_find(&filter_anchor, pos);
587 	while (n != NULL && pos >= n->r.hl_startpos)
588 	{
589 		pos = n->r.hl_startpos;
590 		if (pos == 0)
591 			break;
592 		pos--;
593 		n = n->prev;
594 	}
595 	return (pos);
596 }
597 
598 
599 /*
600  * Should any characters in a specified range be highlighted?
601  * If nohide is nonzero, don't consider hide_hilite.
602  */
603 	public int
604 is_hilited(pos, epos, nohide, p_matches)
605 	POSITION pos;
606 	POSITION epos;
607 	int nohide;
608 	int *p_matches;
609 {
610 	int match;
611 
612 	if (p_matches != NULL)
613 		*p_matches = 0;
614 
615 	if (!status_col &&
616 	    start_attnpos != NULL_POSITION &&
617 	    pos < end_attnpos &&
618 	     (epos == NULL_POSITION || epos > start_attnpos))
619 		/*
620 		 * The attn line overlaps this range.
621 		 */
622 		return (1);
623 
624 	match = is_hilited_range(pos, epos);
625 	if (!match)
626 		return (0);
627 
628 	if (p_matches == NULL)
629 		/*
630 		 * Kinda kludgy way to recognize that caller is checking for
631 		 * hilite in status column. In this case we want to return
632 		 * hilite status even if hiliting is disabled or hidden.
633 		 */
634 		return (1);
635 
636 	/*
637 	 * Report matches, even if we're hiding highlights.
638 	 */
639 	*p_matches = 1;
640 
641 	if (hilite_search == 0)
642 		/*
643 		 * Not doing highlighting.
644 		 */
645 		return (0);
646 
647 	if (!nohide && hide_hilite)
648 		/*
649 		 * Highlighting is hidden.
650 		 */
651 		return (0);
652 
653 	return (1);
654 }
655 
656 /*
657  * Tree node storage: get the current block of nodes if it has spare
658  * capacity, or create a new one if not.
659  */
660 	static struct hilite_storage*
661 hlist_getstorage(anchor)
662 	struct hilite_tree *anchor;
663 {
664 	int capacity = 1;
665 	struct hilite_storage *s;
666 
667 	if (anchor->current)
668 	{
669 		if (anchor->current->used < anchor->current->capacity)
670 			return anchor->current;
671 		capacity = anchor->current->capacity * 2;
672 	}
673 
674 	s = (struct hilite_storage *) ecalloc(1, sizeof(struct hilite_storage));
675 	s->nodes = (struct hilite_node *) ecalloc(capacity, sizeof(struct hilite_node));
676 	s->capacity = capacity;
677 	s->used = 0;
678 	s->next = NULL;
679 	if (anchor->current)
680 		anchor->current->next = s;
681 	else
682 		anchor->first = s;
683 	anchor->current = s;
684 	return s;
685 }
686 
687 /*
688  * Tree node storage: retrieve a new empty node to be inserted into the
689  * tree.
690  */
691 	static struct hilite_node*
692 hlist_getnode(anchor)
693 	struct hilite_tree *anchor;
694 {
695 	struct hilite_storage *s = hlist_getstorage(anchor);
696 	return &s->nodes[s->used++];
697 }
698 
699 /*
700  * Rotate the tree left around a pivot node.
701  */
702 	static void
703 hlist_rotate_left(anchor, n)
704 	struct hilite_tree *anchor;
705 	struct hilite_node *n;
706 {
707 	struct hilite_node *np = n->parent;
708 	struct hilite_node *nr = n->right;
709 	struct hilite_node *nrl = n->right->left;
710 
711 	if (np != NULL)
712 	{
713 		if (n == np->left)
714 			np->left = nr;
715 		else
716 			np->right = nr;
717 	} else
718 	{
719 		anchor->root = nr;
720 	}
721 	nr->left = n;
722 	n->right = nrl;
723 
724 	nr->parent = np;
725 	n->parent = nr;
726 	if (nrl != NULL)
727 		nrl->parent = n;
728 }
729 
730 /*
731  * Rotate the tree right around a pivot node.
732  */
733 	static void
734 hlist_rotate_right(anchor, n)
735 	struct hilite_tree *anchor;
736 	struct hilite_node *n;
737 {
738 	struct hilite_node *np = n->parent;
739 	struct hilite_node *nl = n->left;
740 	struct hilite_node *nlr = n->left->right;
741 
742 	if (np != NULL)
743 	{
744 		if (n == np->right)
745 			np->right = nl;
746 		else
747 			np->left = nl;
748 	} else
749 	{
750 		anchor->root = nl;
751 	}
752 	nl->right = n;
753 	n->left = nlr;
754 
755 	nl->parent = np;
756 	n->parent = nl;
757 	if (nlr != NULL)
758 		nlr->parent = n;
759 }
760 
761 
762 /*
763  * Add a new hilite to a hilite list.
764  */
765 	static void
766 add_hilite(anchor, hl)
767 	struct hilite_tree *anchor;
768 	struct hilite *hl;
769 {
770 	struct hilite_node *p, *n, *u;
771 
772 	/* Ignore empty ranges. */
773 	if (hl->hl_startpos >= hl->hl_endpos)
774 		return;
775 
776 	p = anchor->root;
777 
778 	/* Inserting the very first node is trivial. */
779 	if (p == NULL)
780 	{
781 		n = hlist_getnode(anchor);
782 		n->r = *hl;
783 		anchor->root = n;
784 		anchor->lookaside = n;
785 		return;
786 	}
787 
788 	/*
789 	 * Find our insertion point. If we come across any overlapping
790 	 * or adjoining existing ranges, shrink our range and discard
791 	 * if it become empty.
792 	 */
793 	for (;;)
794 	{
795 		if (hl->hl_startpos < p->r.hl_startpos)
796 		{
797 			if (hl->hl_endpos > p->r.hl_startpos)
798 				hl->hl_endpos = p->r.hl_startpos;
799 			if (p->left != NULL)
800 			{
801 				p = p->left;
802 				continue;
803 			}
804 			break;
805 		}
806 		if (hl->hl_startpos < p->r.hl_endpos) {
807 			hl->hl_startpos = p->r.hl_endpos;
808 			if (hl->hl_startpos >= hl->hl_endpos)
809 				return;
810 		}
811 		if (p->right != NULL)
812 		{
813 			p = p->right;
814 			continue;
815 		}
816 		break;
817 	}
818 
819 	/*
820 	 * Now we're at the right leaf, again check for contiguous ranges
821 	 * and extend the existing node if possible to avoid the
822 	 * insertion. Otherwise insert a new node at the leaf.
823 	 */
824 	if (hl->hl_startpos < p->r.hl_startpos) {
825 		if (hl->hl_endpos == p->r.hl_startpos)
826 		{
827 			p->r.hl_startpos = hl->hl_startpos;
828 			return;
829 		}
830 		if (p->prev != NULL && p->prev->r.hl_endpos == hl->hl_startpos)
831 		{
832 			p->prev->r.hl_endpos = hl->hl_endpos;
833 			return;
834 		}
835 
836 		p->left = n = hlist_getnode(anchor);
837 		n->next = p;
838 		if (p->prev != NULL)
839 		{
840 			n->prev = p->prev;
841 			p->prev->next = n;
842 		}
843 		p->prev = n;
844 	} else {
845 		if (p->r.hl_endpos == hl->hl_startpos)
846 		{
847 			p->r.hl_endpos = hl->hl_endpos;
848 			return;
849 		}
850 		if (p->next != NULL && hl->hl_endpos == p->next->r.hl_startpos) {
851 			p->next->r.hl_startpos = hl->hl_startpos;
852 			return;
853 		}
854 
855 		p->right = n = hlist_getnode(anchor);
856 		n->prev = p;
857 		if (p->next != NULL)
858 		{
859 			n->next = p->next;
860 			p->next->prev = n;
861 		}
862 		p->next = n;
863 	}
864 	n->parent = p;
865 	n->red = 1;
866 	n->r = *hl;
867 
868 	/*
869 	 * The tree is in the correct order and covers the right ranges
870 	 * now, but may have become unbalanced. Rebalance it using the
871 	 * standard red-black tree constraints and operations.
872 	 */
873 	for (;;)
874 	{
875 		/* case 1 - current is root, root is always black */
876 		if (n->parent == NULL)
877 		{
878 			n->red = 0;
879 			break;
880 		}
881 
882 		/* case 2 - parent is black, we can always be red */
883 		if (!n->parent->red)
884 			break;
885 
886 		/*
887 		 * constraint: because the root must be black, if our
888 		 * parent is red it cannot be the root therefore we must
889 		 * have a grandparent
890 		 */
891 
892 		/*
893 		 * case 3 - parent and uncle are red, repaint them black,
894 		 * the grandparent red, and start again at the grandparent.
895 		 */
896 		u = n->parent->parent->left;
897 		if (n->parent == u)
898 			u = n->parent->parent->right;
899 		if (u != NULL && u->red)
900 		{
901 			n->parent->red = 0;
902 			u->red = 0;
903 			n = n->parent->parent;
904 			n->red = 1;
905 			continue;
906 		}
907 
908 		/*
909 		 * case 4 - parent is red but uncle is black, parent and
910 		 * grandparent on opposite sides. We need to start
911 		 * changing the structure now. This and case 5 will shorten
912 		 * our branch and lengthen the sibling, between them
913 		 * restoring balance.
914 		 */
915 		if (n == n->parent->right &&
916 		    n->parent == n->parent->parent->left)
917 		{
918 			hlist_rotate_left(anchor, n->parent);
919 			n = n->left;
920 		} else if (n == n->parent->left &&
921 			   n->parent == n->parent->parent->right)
922 		{
923 			hlist_rotate_right(anchor, n->parent);
924 			n = n->right;
925 		}
926 
927 		/*
928 		 * case 5 - parent is red but uncle is black, parent and
929 		 * grandparent on same side
930 		 */
931 		n->parent->red = 0;
932 		n->parent->parent->red = 1;
933 		if (n == n->parent->left)
934 			hlist_rotate_right(anchor, n->parent->parent);
935 		else
936 			hlist_rotate_left(anchor, n->parent->parent);
937 		break;
938 	}
939 }
940 
941 /*
942  * Hilight every character in a range of displayed characters.
943  */
944 	static void
945 create_hilites(linepos, start_index, end_index, chpos)
946 	POSITION linepos;
947 	int start_index;
948 	int end_index;
949 	int *chpos;
950 {
951 	struct hilite hl;
952 	int i;
953 
954 	/* Start the first hilite. */
955 	hl.hl_startpos = linepos + chpos[start_index];
956 
957 	/*
958 	 * Step through the displayed chars.
959 	 * If the source position (before cvt) of the char is one more
960 	 * than the source pos of the previous char (the usual case),
961 	 * just increase the size of the current hilite by one.
962 	 * Otherwise (there are backspaces or something involved),
963 	 * finish the current hilite and start a new one.
964 	 */
965 	for (i = start_index+1;  i <= end_index;  i++)
966 	{
967 		if (chpos[i] != chpos[i-1] + 1 || i == end_index)
968 		{
969 			hl.hl_endpos = linepos + chpos[i-1] + 1;
970 			add_hilite(&hilite_anchor, &hl);
971 			/* Start new hilite unless this is the last char. */
972 			if (i < end_index)
973 			{
974 				hl.hl_startpos = linepos + chpos[i];
975 			}
976 		}
977 	}
978 }
979 
980 /*
981  * Make a hilite for each string in a physical line which matches
982  * the current pattern.
983  * sp,ep delimit the first match already found.
984  */
985 	static void
986 hilite_line(linepos, line, line_len, chpos, sp, ep, cvt_ops)
987 	POSITION linepos;
988 	char *line;
989 	int line_len;
990 	int *chpos;
991 	char *sp;
992 	char *ep;
993 	int cvt_ops;
994 {
995 	char *searchp;
996 	char *line_end = line + line_len;
997 
998 	/*
999 	 * sp and ep delimit the first match in the line.
1000 	 * Mark the corresponding file positions, then
1001 	 * look for further matches and mark them.
1002 	 * {{ This technique, of calling match_pattern on subsequent
1003 	 *    substrings of the line, may mark more than is correct
1004 	 *    if the pattern starts with "^".  This bug is fixed
1005 	 *    for those regex functions that accept a notbol parameter
1006 	 *    (currently POSIX, PCRE and V8-with-regexec2). }}
1007 	 */
1008 	searchp = line;
1009 	do {
1010 		if (sp == NULL || ep == NULL)
1011 			return;
1012 		create_hilites(linepos, sp-line, ep-line, chpos);
1013 		/*
1014 		 * If we matched more than zero characters,
1015 		 * move to the first char after the string we matched.
1016 		 * If we matched zero, just move to the next char.
1017 		 */
1018 		if (ep > searchp)
1019 			searchp = ep;
1020 		else if (searchp != line_end)
1021 			searchp++;
1022 		else /* end of line */
1023 			break;
1024 	} while (match_pattern(info_compiled(&search_info), search_info.text,
1025 			searchp, line_end - searchp, &sp, &ep, 1, search_info.search_type));
1026 }
1027 #endif
1028 
1029 #if HILITE_SEARCH
1030 /*
1031  * Find matching text which is currently on screen and highlight it.
1032  */
1033 	static void
1034 hilite_screen()
1035 {
1036 	struct scrpos scrpos;
1037 
1038 	get_scrpos(&scrpos, TOP);
1039 	if (scrpos.pos == NULL_POSITION)
1040 		return;
1041 	prep_hilite(scrpos.pos, position(BOTTOM_PLUS_ONE), -1);
1042 	repaint_hilite(1);
1043 }
1044 
1045 /*
1046  * Change highlighting parameters.
1047  */
1048 	public void
1049 chg_hilite()
1050 {
1051 	/*
1052 	 * Erase any highlights currently on screen.
1053 	 */
1054 	clr_hilite();
1055 	hide_hilite = 0;
1056 
1057 	if (hilite_search == OPT_ONPLUS)
1058 		/*
1059 		 * Display highlights.
1060 		 */
1061 		hilite_screen();
1062 }
1063 #endif
1064 
1065 /*
1066  * Figure out where to start a search.
1067  */
1068 	static POSITION
1069 search_pos(search_type)
1070 	int search_type;
1071 {
1072 	POSITION pos;
1073 	int sindex;
1074 
1075 	if (empty_screen())
1076 	{
1077 		/*
1078 		 * Start at the beginning (or end) of the file.
1079 		 * The empty_screen() case is mainly for
1080 		 * command line initiated searches;
1081 		 * for example, "+/xyz" on the command line.
1082 		 * Also for multi-file (SRCH_PAST_EOF) searches.
1083 		 */
1084 		if (search_type & SRCH_FORW)
1085 		{
1086 			pos = ch_zero();
1087 		} else
1088 		{
1089 			pos = ch_length();
1090 			if (pos == NULL_POSITION)
1091 			{
1092 				(void) ch_end_seek();
1093 				pos = ch_length();
1094 			}
1095 		}
1096 		sindex = 0;
1097 	} else
1098 	{
1099 		int add_one = 0;
1100 
1101 		if (how_search == OPT_ON)
1102 		{
1103 			/*
1104 			 * Search does not include current screen.
1105 			 */
1106 			if (search_type & SRCH_FORW)
1107 				sindex = sc_height-1; /* BOTTOM_PLUS_ONE */
1108 			else
1109 				sindex = 0; /* TOP */
1110 		} else if (how_search == OPT_ONPLUS && !(search_type & SRCH_AFTER_TARGET))
1111 		{
1112 			/*
1113 			 * Search includes all of displayed screen.
1114 			 */
1115 			if (search_type & SRCH_FORW)
1116 				sindex = 0; /* TOP */
1117 			else
1118 				sindex = sc_height-1; /* BOTTOM_PLUS_ONE */
1119 		} else
1120 		{
1121 			/*
1122 			 * Search includes the part of current screen beyond the jump target.
1123 			 * It starts at the jump target (if searching backwards),
1124 			 * or at the jump target plus one (if forwards).
1125 			 */
1126 			sindex = sindex_from_sline(jump_sline);
1127 			if (search_type & SRCH_FORW)
1128 				add_one = 1;
1129 		}
1130 		pos = position(sindex);
1131 		if (add_one)
1132 			pos = forw_raw_line(pos, (char **)NULL, (int *)NULL);
1133 	}
1134 
1135 	/*
1136 	 * If the line is empty, look around for a plausible starting place.
1137 	 */
1138 	if (search_type & SRCH_FORW)
1139 	{
1140 		while (pos == NULL_POSITION)
1141 		{
1142 			if (++sindex >= sc_height)
1143 				break;
1144 			pos = position(sindex);
1145 		}
1146 	} else
1147 	{
1148 		while (pos == NULL_POSITION)
1149 		{
1150 			if (--sindex < 0)
1151 				break;
1152 			pos = position(sindex);
1153 		}
1154 	}
1155 	return (pos);
1156 }
1157 
1158 /*
1159  * Search a subset of the file, specified by start/end position.
1160  */
1161 	static int
1162 search_range(pos, endpos, search_type, matches, maxlines, plinepos, pendpos)
1163 	POSITION pos;
1164 	POSITION endpos;
1165 	int search_type;
1166 	int matches;
1167 	int maxlines;
1168 	POSITION *plinepos;
1169 	POSITION *pendpos;
1170 {
1171 	char *line;
1172 	char *cline;
1173 	int line_len;
1174 	LINENUM linenum;
1175 	char *sp, *ep;
1176 	int line_match;
1177 	int cvt_ops;
1178 	int cvt_len;
1179 	int *chpos;
1180 	POSITION linepos, oldpos;
1181 
1182 	linenum = find_linenum(pos);
1183 	oldpos = pos;
1184 	for (;;)
1185 	{
1186 		/*
1187 		 * Get lines until we find a matching one or until
1188 		 * we hit end-of-file (or beginning-of-file if we're
1189 		 * going backwards), or until we hit the end position.
1190 		 */
1191 		if (ABORT_SIGS())
1192 		{
1193 			/*
1194 			 * A signal aborts the search.
1195 			 */
1196 			return (-1);
1197 		}
1198 
1199 		if ((endpos != NULL_POSITION && pos >= endpos) || maxlines == 0)
1200 		{
1201 			/*
1202 			 * Reached end position without a match.
1203 			 */
1204 			if (pendpos != NULL)
1205 				*pendpos = pos;
1206 			return (matches);
1207 		}
1208 		if (maxlines > 0)
1209 			maxlines--;
1210 
1211 		if (search_type & SRCH_FORW)
1212 		{
1213 			/*
1214 			 * Read the next line, and save the
1215 			 * starting position of that line in linepos.
1216 			 */
1217 			linepos = pos;
1218 			pos = forw_raw_line(pos, &line, &line_len);
1219 			if (linenum != 0)
1220 				linenum++;
1221 		} else
1222 		{
1223 			/*
1224 			 * Read the previous line and save the
1225 			 * starting position of that line in linepos.
1226 			 */
1227 			pos = back_raw_line(pos, &line, &line_len);
1228 			linepos = pos;
1229 			if (linenum != 0)
1230 				linenum--;
1231 		}
1232 
1233 		if (pos == NULL_POSITION)
1234 		{
1235 			/*
1236 			 * Reached EOF/BOF without a match.
1237 			 */
1238 			if (pendpos != NULL)
1239 				*pendpos = oldpos;
1240 			return (matches);
1241 		}
1242 
1243 		/*
1244 		 * If we're using line numbers, we might as well
1245 		 * remember the information we have now (the position
1246 		 * and line number of the current line).
1247 		 * Don't do it for every line because it slows down
1248 		 * the search.  Remember the line number only if
1249 		 * we're "far" from the last place we remembered it.
1250 		 */
1251 		if (linenums && abs((int)(pos - oldpos)) > 2048)
1252 			add_lnum(linenum, pos);
1253 		oldpos = pos;
1254 
1255 		if (is_filtered(linepos))
1256 			continue;
1257 
1258 		/*
1259 		 * If it's a caseless search, convert the line to lowercase.
1260 		 * If we're doing backspace processing, delete backspaces.
1261 		 */
1262 		cvt_ops = get_cvt_ops();
1263 		cvt_len = cvt_length(line_len, cvt_ops);
1264 		cline = (char *) ecalloc(1, cvt_len);
1265 		chpos = cvt_alloc_chpos(cvt_len);
1266 		cvt_text(cline, line, chpos, &line_len, cvt_ops);
1267 
1268 #if HILITE_SEARCH
1269 		/*
1270 		 * Check to see if the line matches the filter pattern.
1271 		 * If so, add an entry to the filter list.
1272 		 */
1273 		if (((search_type & SRCH_FIND_ALL) ||
1274 		     prep_startpos == NULL_POSITION ||
1275 		     linepos < prep_startpos || linepos >= prep_endpos) &&
1276 		    prev_pattern(&filter_info)) {
1277 			int line_filter = match_pattern(info_compiled(&filter_info), filter_info.text,
1278 				cline, line_len, &sp, &ep, 0, filter_info.search_type);
1279 			if (line_filter)
1280 			{
1281 				struct hilite hl;
1282 				hl.hl_startpos = linepos;
1283 				hl.hl_endpos = pos;
1284 				add_hilite(&filter_anchor, &hl);
1285 				free(cline);
1286 				free(chpos);
1287 				continue;
1288 			}
1289 		}
1290 #endif
1291 
1292 		/*
1293 		 * Test the next line to see if we have a match.
1294 		 * We are successful if we either want a match and got one,
1295 		 * or if we want a non-match and got one.
1296 		 */
1297 		if (prev_pattern(&search_info))
1298 		{
1299 			line_match = match_pattern(info_compiled(&search_info), search_info.text,
1300 				cline, line_len, &sp, &ep, 0, search_type);
1301 			if (line_match)
1302 			{
1303 				/*
1304 				 * Got a match.
1305 				 */
1306 				if (search_type & SRCH_FIND_ALL)
1307 				{
1308 #if HILITE_SEARCH
1309 					/*
1310 					 * We are supposed to find all matches in the range.
1311 					 * Just add the matches in this line to the
1312 					 * hilite list and keep searching.
1313 					 */
1314 					hilite_line(linepos, cline, line_len, chpos, sp, ep, cvt_ops);
1315 #endif
1316 				} else if (--matches <= 0)
1317 				{
1318 					/*
1319 					 * Found the one match we're looking for.
1320 					 * Return it.
1321 					 */
1322 #if HILITE_SEARCH
1323 					if (hilite_search == OPT_ON)
1324 					{
1325 						/*
1326 						 * Clear the hilite list and add only
1327 						 * the matches in this one line.
1328 						 */
1329 						clr_hilite();
1330 						hilite_line(linepos, cline, line_len, chpos, sp, ep, cvt_ops);
1331 					}
1332 #endif
1333 					free(cline);
1334 					free(chpos);
1335 					if (plinepos != NULL)
1336 						*plinepos = linepos;
1337 					return (0);
1338 				}
1339 			}
1340 		}
1341 		free(cline);
1342 		free(chpos);
1343 	}
1344 }
1345 
1346 /*
1347  * search for a pattern in history. If found, compile that pattern.
1348  */
1349 	static int
1350 hist_pattern(search_type)
1351 	int search_type;
1352 {
1353 #if CMD_HISTORY
1354 	char *pattern;
1355 
1356 	set_mlist(ml_search, 0);
1357 	pattern = cmd_lastpattern();
1358 	if (pattern == NULL)
1359 		return (0);
1360 
1361 	if (set_pattern(&search_info, pattern, search_type) < 0)
1362 		return (0);
1363 
1364 #if HILITE_SEARCH
1365 	if (hilite_search == OPT_ONPLUS && !hide_hilite)
1366 		hilite_screen();
1367 #endif
1368 
1369 	return (1);
1370 #else /* CMD_HISTORY */
1371 	return (0);
1372 #endif /* CMD_HISTORY */
1373 }
1374 
1375 /*
1376  * Change the caseless-ness of searches.
1377  * Updates the internal search state to reflect a change in the -i flag.
1378  */
1379 	public void
1380 chg_caseless()
1381 {
1382 	if (!is_ucase_pattern)
1383 		/*
1384 		 * Pattern did not have uppercase.
1385 		 * Just set the search caselessness to the global caselessness.
1386 		 */
1387 		is_caseless = caseless;
1388 	else
1389 	{
1390 		/*
1391 		 * Pattern did have uppercase.
1392 		 * Regenerate the pattern using the new state.
1393 		 */
1394 		clear_pattern(&search_info);
1395 		hist_pattern(search_info.search_type);
1396 	}
1397 }
1398 
1399 /*
1400  * Search for the n-th occurrence of a specified pattern,
1401  * either forward or backward.
1402  * Return the number of matches not yet found in this file
1403  * (that is, n minus the number of matches found).
1404  * Return -1 if the search should be aborted.
1405  * Caller may continue the search in another file
1406  * if less than n matches are found in this file.
1407  */
1408 	public int
1409 search(search_type, pattern, n)
1410 	int search_type;
1411 	char *pattern;
1412 	int n;
1413 {
1414 	POSITION pos;
1415 
1416 	if (pattern == NULL || *pattern == '\0')
1417 	{
1418 		/*
1419 		 * A null pattern means use the previously compiled pattern.
1420 		 */
1421 		search_type |= SRCH_AFTER_TARGET;
1422 		if (!prev_pattern(&search_info) && !hist_pattern(search_type))
1423 		{
1424 			error("No previous regular expression", NULL_PARG);
1425 			return (-1);
1426 		}
1427 		if ((search_type & SRCH_NO_REGEX) !=
1428 		      (search_info.search_type & SRCH_NO_REGEX))
1429 		{
1430 			error("Please re-enter search pattern", NULL_PARG);
1431 			return -1;
1432 		}
1433 #if HILITE_SEARCH
1434 		if (hilite_search == OPT_ON || status_col)
1435 		{
1436 			/*
1437 			 * Erase the highlights currently on screen.
1438 			 * If the search fails, we'll redisplay them later.
1439 			 */
1440 			repaint_hilite(0);
1441 		}
1442 		if (hilite_search == OPT_ONPLUS && hide_hilite)
1443 		{
1444 			/*
1445 			 * Highlight any matches currently on screen,
1446 			 * before we actually start the search.
1447 			 */
1448 			hide_hilite = 0;
1449 			hilite_screen();
1450 		}
1451 		hide_hilite = 0;
1452 #endif
1453 	} else
1454 	{
1455 		/*
1456 		 * Compile the pattern.
1457 		 */
1458 		if (set_pattern(&search_info, pattern, search_type) < 0)
1459 			return (-1);
1460 #if HILITE_SEARCH
1461 		if (hilite_search || status_col)
1462 		{
1463 			/*
1464 			 * Erase the highlights currently on screen.
1465 			 * Also permanently delete them from the hilite list.
1466 			 */
1467 			repaint_hilite(0);
1468 			hide_hilite = 0;
1469 			clr_hilite();
1470 		}
1471 		if (hilite_search == OPT_ONPLUS || status_col)
1472 		{
1473 			/*
1474 			 * Highlight any matches currently on screen,
1475 			 * before we actually start the search.
1476 			 */
1477 			hilite_screen();
1478 		}
1479 #endif
1480 	}
1481 
1482 	/*
1483 	 * Figure out where to start the search.
1484 	 */
1485 	pos = search_pos(search_type);
1486 	if (pos == NULL_POSITION)
1487 	{
1488 		/*
1489 		 * Can't find anyplace to start searching from.
1490 		 */
1491 		if (search_type & SRCH_PAST_EOF)
1492 			return (n);
1493 		if (hilite_search == OPT_ON || status_col)
1494 			repaint_hilite(1);
1495 		error("Nothing to search", NULL_PARG);
1496 		return (-1);
1497 	}
1498 
1499 	n = search_range(pos, NULL_POSITION, search_type, n, -1,
1500 			&pos, (POSITION*)NULL);
1501 	if (n != 0)
1502 	{
1503 		/*
1504 		 * Search was unsuccessful.
1505 		 */
1506 #if HILITE_SEARCH
1507 		if ((hilite_search == OPT_ON || status_col) && n > 0)
1508 			/*
1509 			 * Redisplay old hilites.
1510 			 */
1511 			repaint_hilite(1);
1512 #endif
1513 		return (n);
1514 	}
1515 
1516 	if (!(search_type & SRCH_NO_MOVE))
1517 	{
1518 		/*
1519 		 * Go to the matching line.
1520 		 */
1521 		jump_loc(pos, jump_sline);
1522 	}
1523 
1524 #if HILITE_SEARCH
1525 	if (hilite_search == OPT_ON || status_col)
1526 		/*
1527 		 * Display new hilites in the matching line.
1528 		 */
1529 		repaint_hilite(1);
1530 #endif
1531 	return (0);
1532 }
1533 
1534 
1535 #if HILITE_SEARCH
1536 /*
1537  * Prepare hilites in a given range of the file.
1538  *
1539  * The pair (prep_startpos,prep_endpos) delimits a contiguous region
1540  * of the file that has been "prepared"; that is, scanned for matches for
1541  * the current search pattern, and hilites have been created for such matches.
1542  * If prep_startpos == NULL_POSITION, the prep region is empty.
1543  * If prep_endpos == NULL_POSITION, the prep region extends to EOF.
1544  * prep_hilite asks that the range (spos,epos) be covered by the prep region.
1545  */
1546 	public void
1547 prep_hilite(spos, epos, maxlines)
1548 	POSITION spos;
1549 	POSITION epos;
1550 	int maxlines;
1551 {
1552 	POSITION nprep_startpos = prep_startpos;
1553 	POSITION nprep_endpos = prep_endpos;
1554 	POSITION new_epos;
1555 	POSITION max_epos;
1556 	int result;
1557 	int i;
1558 
1559 /*
1560  * Search beyond where we're asked to search, so the prep region covers
1561  * more than we need.  Do one big search instead of a bunch of small ones.
1562  */
1563 #define	SEARCH_MORE (3*size_linebuf)
1564 
1565 	if (!prev_pattern(&search_info) && !is_filtering())
1566 		return;
1567 
1568 	/*
1569 	 * Make sure our prep region always starts at the beginning of
1570 	 * a line. (search_range takes care of the end boundary below.)
1571 	 */
1572 	spos = back_raw_line(spos+1, (char **)NULL, (int *)NULL);
1573 
1574 	/*
1575 	 * If we're limited to a max number of lines, figure out the
1576 	 * file position we should stop at.
1577 	 */
1578 	if (maxlines < 0)
1579 		max_epos = NULL_POSITION;
1580 	else
1581 	{
1582 		max_epos = spos;
1583 		for (i = 0;  i < maxlines;  i++)
1584 			max_epos = forw_raw_line(max_epos, (char **)NULL, (int *)NULL);
1585 	}
1586 
1587 	/*
1588 	 * Find two ranges:
1589 	 * The range that we need to search (spos,epos); and the range that
1590 	 * the "prep" region will then cover (nprep_startpos,nprep_endpos).
1591 	 */
1592 
1593 	if (prep_startpos == NULL_POSITION ||
1594 	    (epos != NULL_POSITION && epos < prep_startpos) ||
1595 	    spos > prep_endpos)
1596 	{
1597 		/*
1598 		 * New range is not contiguous with old prep region.
1599 		 * Discard the old prep region and start a new one.
1600 		 */
1601 		clr_hilite();
1602 		clr_filter();
1603 		if (epos != NULL_POSITION)
1604 			epos += SEARCH_MORE;
1605 		nprep_startpos = spos;
1606 	} else
1607 	{
1608 		/*
1609 		 * New range partially or completely overlaps old prep region.
1610 		 */
1611 		if (epos == NULL_POSITION)
1612 		{
1613 			/*
1614 			 * New range goes to end of file.
1615 			 */
1616 			;
1617 		} else if (epos > prep_endpos)
1618 		{
1619 			/*
1620 			 * New range ends after old prep region.
1621 			 * Extend prep region to end at end of new range.
1622 			 */
1623 			epos += SEARCH_MORE;
1624 		} else /* (epos <= prep_endpos) */
1625 		{
1626 			/*
1627 			 * New range ends within old prep region.
1628 			 * Truncate search to end at start of old prep region.
1629 			 */
1630 			epos = prep_startpos;
1631 		}
1632 
1633 		if (spos < prep_startpos)
1634 		{
1635 			/*
1636 			 * New range starts before old prep region.
1637 			 * Extend old prep region backwards to start at
1638 			 * start of new range.
1639 			 */
1640 			if (spos < SEARCH_MORE)
1641 				spos = 0;
1642 			else
1643 				spos -= SEARCH_MORE;
1644 			nprep_startpos = spos;
1645 		} else /* (spos >= prep_startpos) */
1646 		{
1647 			/*
1648 			 * New range starts within or after old prep region.
1649 			 * Trim search to start at end of old prep region.
1650 			 */
1651 			spos = prep_endpos;
1652 		}
1653 	}
1654 
1655 	if (epos != NULL_POSITION && max_epos != NULL_POSITION &&
1656 	    epos > max_epos)
1657 		/*
1658 		 * Don't go past the max position we're allowed.
1659 		 */
1660 		epos = max_epos;
1661 
1662 	if (epos == NULL_POSITION || epos > spos)
1663 	{
1664 		int search_type = SRCH_FORW | SRCH_FIND_ALL;
1665 		search_type |= (search_info.search_type & SRCH_NO_REGEX);
1666 		for (;;)
1667 		{
1668 			result = search_range(spos, epos, search_type, 0, maxlines, (POSITION*)NULL, &new_epos);
1669 			if (result < 0)
1670 				return;
1671 			if (prep_endpos == NULL_POSITION || new_epos > prep_endpos)
1672 				nprep_endpos = new_epos;
1673 
1674 			/*
1675 			 * Check both ends of the resulting prep region to
1676 			 * make sure they're not filtered. If they are,
1677 			 * keep going at least one more line until we find
1678 			 * something that isn't filtered, or hit the end.
1679 			 */
1680 			if (prep_endpos == NULL_POSITION || nprep_endpos > prep_endpos)
1681 			{
1682 				if (new_epos >= nprep_endpos && is_filtered(new_epos-1))
1683 				{
1684 					spos = nprep_endpos;
1685 					epos = forw_raw_line(nprep_endpos, (char **)NULL, (int *)NULL);
1686 					if (epos == NULL_POSITION)
1687 						break;
1688 					maxlines = 1;
1689 					continue;
1690 				}
1691 			}
1692 
1693 			if (prep_startpos == NULL_POSITION || nprep_startpos < prep_startpos)
1694 			{
1695 				if (nprep_startpos > 0 && is_filtered(nprep_startpos))
1696 				{
1697 					epos = nprep_startpos;
1698 					spos = back_raw_line(nprep_startpos, (char **)NULL, (int *)NULL);
1699 					if (spos == NULL_POSITION)
1700 						break;
1701 					nprep_startpos = spos;
1702 					maxlines = 1;
1703 					continue;
1704 				}
1705 			}
1706 			break;
1707 		}
1708 	}
1709 	prep_startpos = nprep_startpos;
1710 	prep_endpos = nprep_endpos;
1711 }
1712 
1713 /*
1714  * Set the pattern to be used for line filtering.
1715  */
1716 	public void
1717 set_filter_pattern(pattern, search_type)
1718 	char *pattern;
1719 	int search_type;
1720 {
1721 	clr_filter();
1722 	if (pattern == NULL || *pattern == '\0')
1723 		clear_pattern(&filter_info);
1724 	else
1725 		set_pattern(&filter_info, pattern, search_type);
1726 	screen_trashed = 1;
1727 }
1728 
1729 /*
1730  * Is there a line filter in effect?
1731  */
1732 	public int
1733 is_filtering()
1734 {
1735 	if (ch_getflags() & CH_HELPFILE)
1736 		return (0);
1737 	return prev_pattern(&filter_info);
1738 }
1739 #endif
1740 
1741 #if HAVE_V8_REGCOMP
1742 /*
1743  * This function is called by the V8 regcomp to report
1744  * errors in regular expressions.
1745  */
1746 public int reg_show_error = 1;
1747 
1748 	void
1749 regerror(s)
1750 	char *s;
1751 {
1752 	PARG parg;
1753 
1754 	if (!reg_show_error)
1755 		return;
1756 	parg.p_string = s;
1757 	error("%s", &parg);
1758 }
1759 #endif
1760 
1761