xref: /netbsd-src/lib/libedit/chared.c (revision 23c8222edbfb0f0932d88a8351d3a0cf817dfb9e)
1 /*	$NetBSD: chared.c,v 1.22 2004/08/13 12:10:38 mycroft Exp $	*/
2 
3 /*-
4  * Copyright (c) 1992, 1993
5  *	The Regents of the University of California.  All rights reserved.
6  *
7  * This code is derived from software contributed to Berkeley by
8  * Christos Zoulas of Cornell University.
9  *
10  * Redistribution and use in source and binary forms, with or without
11  * modification, are permitted provided that the following conditions
12  * are met:
13  * 1. Redistributions of source code must retain the above copyright
14  *    notice, this list of conditions and the following disclaimer.
15  * 2. Redistributions in binary form must reproduce the above copyright
16  *    notice, this list of conditions and the following disclaimer in the
17  *    documentation and/or other materials provided with the distribution.
18  * 3. Neither the name of the University nor the names of its contributors
19  *    may be used to endorse or promote products derived from this software
20  *    without specific prior written permission.
21  *
22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32  * SUCH DAMAGE.
33  */
34 
35 #include "config.h"
36 #if !defined(lint) && !defined(SCCSID)
37 #if 0
38 static char sccsid[] = "@(#)chared.c	8.1 (Berkeley) 6/4/93";
39 #else
40 __RCSID("$NetBSD: chared.c,v 1.22 2004/08/13 12:10:38 mycroft Exp $");
41 #endif
42 #endif /* not lint && not SCCSID */
43 
44 /*
45  * chared.c: Character editor utilities
46  */
47 #include <stdlib.h>
48 #include "el.h"
49 
50 /* value to leave unused in line buffer */
51 #define	EL_LEAVE	2
52 
53 /* cv_undo():
54  *	Handle state for the vi undo command
55  */
56 protected void
57 cv_undo(EditLine *el)
58 {
59 	c_undo_t *vu = &el->el_chared.c_undo;
60 	c_redo_t *r = &el->el_chared.c_redo;
61 	uint size;
62 
63 	/* Save entire line for undo */
64 	size = el->el_line.lastchar - el->el_line.buffer;
65 	vu->len = size;
66 	vu->cursor = el->el_line.cursor - el->el_line.buffer;
67 	memcpy(vu->buf, el->el_line.buffer, size);
68 
69 	/* save command info for redo */
70 	r->count = el->el_state.doingarg ? el->el_state.argument : 0;
71 	r->action = el->el_chared.c_vcmd.action;
72 	r->pos = r->buf;
73 	r->cmd = el->el_state.thiscmd;
74 	r->ch = el->el_state.thisch;
75 }
76 
77 /* cv_yank():
78  *	Save yank/delete data for paste
79  */
80 protected void
81 cv_yank(EditLine *el, const char *ptr, int size)
82 {
83 	c_kill_t *k = &el->el_chared.c_kill;
84 
85 	memcpy(k->buf, ptr, size +0u);
86 	k->last = k->buf + size;
87 }
88 
89 
90 /* c_insert():
91  *	Insert num characters
92  */
93 protected void
94 c_insert(EditLine *el, int num)
95 {
96 	char *cp;
97 
98 	if (el->el_line.lastchar + num >= el->el_line.limit) {
99 		if (!ch_enlargebufs(el, num +0u))
100 			return;		/* can't go past end of buffer */
101 	}
102 
103 	if (el->el_line.cursor < el->el_line.lastchar) {
104 		/* if I must move chars */
105 		for (cp = el->el_line.lastchar; cp >= el->el_line.cursor; cp--)
106 			cp[num] = *cp;
107 	}
108 	el->el_line.lastchar += num;
109 }
110 
111 
112 /* c_delafter():
113  *	Delete num characters after the cursor
114  */
115 protected void
116 c_delafter(EditLine *el, int num)
117 {
118 
119 	if (el->el_line.cursor + num > el->el_line.lastchar)
120 		num = el->el_line.lastchar - el->el_line.cursor;
121 
122 	if (el->el_map.current != el->el_map.emacs) {
123 		cv_undo(el);
124 		cv_yank(el, el->el_line.cursor, num);
125 	}
126 
127 	if (num > 0) {
128 		char *cp;
129 
130 		for (cp = el->el_line.cursor; cp <= el->el_line.lastchar; cp++)
131 			*cp = cp[num];
132 
133 		el->el_line.lastchar -= num;
134 	}
135 }
136 
137 
138 /* c_delafter1():
139  *	Delete the character after the cursor, do not yank
140  */
141 protected void
142 c_delafter1(EditLine *el)
143 {
144 	char *cp;
145 
146 	for (cp = el->el_line.cursor; cp <= el->el_line.lastchar; cp++)
147 		*cp = cp[1];
148 
149 	el->el_line.lastchar--;
150 }
151 
152 
153 /* c_delbefore():
154  *	Delete num characters before the cursor
155  */
156 protected void
157 c_delbefore(EditLine *el, int num)
158 {
159 
160 	if (el->el_line.cursor - num < el->el_line.buffer)
161 		num = el->el_line.cursor - el->el_line.buffer;
162 
163 	if (el->el_map.current != el->el_map.emacs) {
164 		cv_undo(el);
165 		cv_yank(el, el->el_line.cursor - num, num);
166 	}
167 
168 	if (num > 0) {
169 		char *cp;
170 
171 		for (cp = el->el_line.cursor - num;
172 		    cp <= el->el_line.lastchar;
173 		    cp++)
174 			*cp = cp[num];
175 
176 		el->el_line.lastchar -= num;
177 	}
178 }
179 
180 
181 /* c_delbefore1():
182  *	Delete the character before the cursor, do not yank
183  */
184 protected void
185 c_delbefore1(EditLine *el)
186 {
187 	char *cp;
188 
189 	for (cp = el->el_line.cursor - 1; cp <= el->el_line.lastchar; cp++)
190 		*cp = cp[1];
191 
192 	el->el_line.lastchar--;
193 }
194 
195 
196 /* ce__isword():
197  *	Return if p is part of a word according to emacs
198  */
199 protected int
200 ce__isword(int p)
201 {
202 	return (isalnum(p) || strchr("*?_-.[]~=", p) != NULL);
203 }
204 
205 
206 /* cv__isword():
207  *	Return if p is part of a word according to vi
208  */
209 protected int
210 cv__isword(int p)
211 {
212 	if (isalnum(p) || p == '_')
213 		return 1;
214 	if (isgraph(p))
215 		return 2;
216 	return 0;
217 }
218 
219 
220 /* cv__isWord():
221  *	Return if p is part of a big word according to vi
222  */
223 protected int
224 cv__isWord(int p)
225 {
226 	return (!isspace(p));
227 }
228 
229 
230 /* c__prev_word():
231  *	Find the previous word
232  */
233 protected char *
234 c__prev_word(char *p, char *low, int n, int (*wtest)(int))
235 {
236 	p--;
237 
238 	while (n--) {
239 		while ((p >= low) && !(*wtest)((unsigned char) *p))
240 			p--;
241 		while ((p >= low) && (*wtest)((unsigned char) *p))
242 			p--;
243 	}
244 
245 	/* cp now points to one character before the word */
246 	p++;
247 	if (p < low)
248 		p = low;
249 	/* cp now points where we want it */
250 	return (p);
251 }
252 
253 
254 /* c__next_word():
255  *	Find the next word
256  */
257 protected char *
258 c__next_word(char *p, char *high, int n, int (*wtest)(int))
259 {
260 	while (n--) {
261 		while ((p < high) && !(*wtest)((unsigned char) *p))
262 			p++;
263 		while ((p < high) && (*wtest)((unsigned char) *p))
264 			p++;
265 	}
266 	if (p > high)
267 		p = high;
268 	/* p now points where we want it */
269 	return (p);
270 }
271 
272 /* cv_next_word():
273  *	Find the next word vi style
274  */
275 protected char *
276 cv_next_word(EditLine *el, char *p, char *high, int n, int (*wtest)(int))
277 {
278 	int test;
279 
280 	while (n--) {
281 		test = (*wtest)((unsigned char) *p);
282 		while ((p < high) && (*wtest)((unsigned char) *p) == test)
283 			p++;
284 		/*
285 		 * vi historically deletes with cw only the word preserving the
286 		 * trailing whitespace! This is not what 'w' does..
287 		 */
288 		if (n || el->el_chared.c_vcmd.action != (DELETE|INSERT))
289 			while ((p < high) && isspace((unsigned char) *p))
290 				p++;
291 	}
292 
293 	/* p now points where we want it */
294 	if (p > high)
295 		return (high);
296 	else
297 		return (p);
298 }
299 
300 
301 /* cv_prev_word():
302  *	Find the previous word vi style
303  */
304 protected char *
305 cv_prev_word(char *p, char *low, int n, int (*wtest)(int))
306 {
307 	int test;
308 
309 	p--;
310 	while (n--) {
311 		while ((p > low) && isspace((unsigned char) *p))
312 			p--;
313 		test = (*wtest)((unsigned char) *p);
314 		while ((p >= low) && (*wtest)((unsigned char) *p) == test)
315 			p--;
316 	}
317 	p++;
318 
319 	/* p now points where we want it */
320 	if (p < low)
321 		return (low);
322 	else
323 		return (p);
324 }
325 
326 
327 #ifdef notdef
328 /* c__number():
329  *	Ignore character p points to, return number appearing after that.
330  * 	A '$' by itself means a big number; "$-" is for negative; '^' means 1.
331  * 	Return p pointing to last char used.
332  */
333 protected char *
334 c__number(
335     char *p,	/* character position */
336     int *num,	/* Return value	*/
337     int dval)	/* dval is the number to subtract from like $-3 */
338 {
339 	int i;
340 	int sign = 1;
341 
342 	if (*++p == '^') {
343 		*num = 1;
344 		return (p);
345 	}
346 	if (*p == '$') {
347 		if (*++p != '-') {
348 			*num = 0x7fffffff;	/* Handle $ */
349 			return (--p);
350 		}
351 		sign = -1;			/* Handle $- */
352 		++p;
353 	}
354 	for (i = 0; isdigit((unsigned char) *p); i = 10 * i + *p++ - '0')
355 		continue;
356 	*num = (sign < 0 ? dval - i : i);
357 	return (--p);
358 }
359 #endif
360 
361 /* cv_delfini():
362  *	Finish vi delete action
363  */
364 protected void
365 cv_delfini(EditLine *el)
366 {
367 	int size;
368 	int action = el->el_chared.c_vcmd.action;
369 
370 	if (action & INSERT)
371 		el->el_map.current = el->el_map.key;
372 
373 	if (el->el_chared.c_vcmd.pos == 0)
374 		/* sanity */
375 		return;
376 
377 	size = el->el_line.cursor - el->el_chared.c_vcmd.pos;
378 	if (size == 0)
379 		size = 1;
380 	el->el_line.cursor = el->el_chared.c_vcmd.pos;
381 	if (action & YANK) {
382 		if (size > 0)
383 			cv_yank(el, el->el_line.cursor, size);
384 		else
385 			cv_yank(el, el->el_line.cursor + size, -size);
386 	} else {
387 		if (size > 0) {
388 			c_delafter(el, size);
389 			re_refresh_cursor(el);
390 		} else  {
391 			c_delbefore(el, -size);
392 			el->el_line.cursor += size;
393 		}
394 	}
395 	el->el_chared.c_vcmd.action = NOP;
396 }
397 
398 
399 #ifdef notdef
400 /* ce__endword():
401  *	Go to the end of this word according to emacs
402  */
403 protected char *
404 ce__endword(char *p, char *high, int n)
405 {
406 	p++;
407 
408 	while (n--) {
409 		while ((p < high) && isspace((unsigned char) *p))
410 			p++;
411 		while ((p < high) && !isspace((unsigned char) *p))
412 			p++;
413 	}
414 
415 	p--;
416 	return (p);
417 }
418 #endif
419 
420 
421 /* cv__endword():
422  *	Go to the end of this word according to vi
423  */
424 protected char *
425 cv__endword(char *p, char *high, int n, int (*wtest)(int))
426 {
427 	int test;
428 
429 	p++;
430 
431 	while (n--) {
432 		while ((p < high) && isspace((unsigned char) *p))
433 			p++;
434 
435 		test = (*wtest)((unsigned char) *p);
436 		while ((p < high) && (*wtest)((unsigned char) *p) == test)
437 			p++;
438 	}
439 	p--;
440 	return (p);
441 }
442 
443 /* ch_init():
444  *	Initialize the character editor
445  */
446 protected int
447 ch_init(EditLine *el)
448 {
449 	el->el_line.buffer		= (char *) el_malloc(EL_BUFSIZ);
450 	if (el->el_line.buffer == NULL)
451 		return (-1);
452 
453 	(void) memset(el->el_line.buffer, 0, EL_BUFSIZ);
454 	el->el_line.cursor		= el->el_line.buffer;
455 	el->el_line.lastchar		= el->el_line.buffer;
456 	el->el_line.limit		= &el->el_line.buffer[EL_BUFSIZ - EL_LEAVE];
457 
458 	el->el_chared.c_undo.buf	= (char *) el_malloc(EL_BUFSIZ);
459 	if (el->el_chared.c_undo.buf == NULL)
460 		return (-1);
461 	(void) memset(el->el_chared.c_undo.buf, 0, EL_BUFSIZ);
462 	el->el_chared.c_undo.len	= -1;
463 	el->el_chared.c_undo.cursor	= 0;
464 	el->el_chared.c_redo.buf	= (char *) el_malloc(EL_BUFSIZ);
465 	if (el->el_chared.c_redo.buf == NULL)
466 		return (-1);
467 	el->el_chared.c_redo.pos	= el->el_chared.c_redo.buf;
468 	el->el_chared.c_redo.lim	= el->el_chared.c_redo.buf + EL_BUFSIZ;
469 	el->el_chared.c_redo.cmd	= ED_UNASSIGNED;
470 
471 	el->el_chared.c_vcmd.action	= NOP;
472 	el->el_chared.c_vcmd.pos	= el->el_line.buffer;
473 
474 	el->el_chared.c_kill.buf	= (char *) el_malloc(EL_BUFSIZ);
475 	if (el->el_chared.c_kill.buf == NULL)
476 		return (-1);
477 	(void) memset(el->el_chared.c_kill.buf, 0, EL_BUFSIZ);
478 	el->el_chared.c_kill.mark	= el->el_line.buffer;
479 	el->el_chared.c_kill.last	= el->el_chared.c_kill.buf;
480 
481 	el->el_map.current		= el->el_map.key;
482 
483 	el->el_state.inputmode		= MODE_INSERT; /* XXX: save a default */
484 	el->el_state.doingarg		= 0;
485 	el->el_state.metanext		= 0;
486 	el->el_state.argument		= 1;
487 	el->el_state.lastcmd		= ED_UNASSIGNED;
488 
489 	el->el_chared.c_macro.level	= -1;
490 	el->el_chared.c_macro.offset	= 0;
491 	el->el_chared.c_macro.macro	= (char **) el_malloc(EL_MAXMACRO *
492 	    sizeof(char *));
493 	if (el->el_chared.c_macro.macro == NULL)
494 		return (-1);
495 	return (0);
496 }
497 
498 /* ch_reset():
499  *	Reset the character editor
500  */
501 protected void
502 ch_reset(EditLine *el)
503 {
504 	el->el_line.cursor		= el->el_line.buffer;
505 	el->el_line.lastchar		= el->el_line.buffer;
506 
507 	el->el_chared.c_undo.len	= -1;
508 	el->el_chared.c_undo.cursor	= 0;
509 
510 	el->el_chared.c_vcmd.action	= NOP;
511 	el->el_chared.c_vcmd.pos	= el->el_line.buffer;
512 
513 	el->el_chared.c_kill.mark	= el->el_line.buffer;
514 
515 	el->el_map.current		= el->el_map.key;
516 
517 	el->el_state.inputmode		= MODE_INSERT; /* XXX: save a default */
518 	el->el_state.doingarg		= 0;
519 	el->el_state.metanext		= 0;
520 	el->el_state.argument		= 1;
521 	el->el_state.lastcmd		= ED_UNASSIGNED;
522 
523 	el->el_chared.c_macro.level	= -1;
524 
525 	el->el_history.eventno		= 0;
526 }
527 
528 /* ch_enlargebufs():
529  *	Enlarge line buffer to be able to hold twice as much characters.
530  *	Returns 1 if successful, 0 if not.
531  */
532 protected int
533 ch_enlargebufs(el, addlen)
534 	EditLine *el;
535 	size_t addlen;
536 {
537 	size_t sz, newsz;
538 	char *newbuffer, *oldbuf, *oldkbuf;
539 
540 	sz = el->el_line.limit - el->el_line.buffer + EL_LEAVE;
541 	newsz = sz * 2;
542 	/*
543 	 * If newly required length is longer than current buffer, we need
544 	 * to make the buffer big enough to hold both old and new stuff.
545 	 */
546 	if (addlen > sz) {
547 		while(newsz - sz < addlen)
548 			newsz *= 2;
549 	}
550 
551 	/*
552 	 * Reallocate line buffer.
553 	 */
554 	newbuffer = el_realloc(el->el_line.buffer, newsz);
555 	if (!newbuffer)
556 		return 0;
557 
558 	/* zero the newly added memory, leave old data in */
559 	(void) memset(&newbuffer[sz], 0, newsz - sz);
560 
561 	oldbuf = el->el_line.buffer;
562 
563 	el->el_line.buffer = newbuffer;
564 	el->el_line.cursor = newbuffer + (el->el_line.cursor - oldbuf);
565 	el->el_line.lastchar = newbuffer + (el->el_line.lastchar - oldbuf);
566 	/* don't set new size until all buffers are enlarged */
567 	el->el_line.limit  = &newbuffer[sz - EL_LEAVE];
568 
569 	/*
570 	 * Reallocate kill buffer.
571 	 */
572 	newbuffer = el_realloc(el->el_chared.c_kill.buf, newsz);
573 	if (!newbuffer)
574 		return 0;
575 
576 	/* zero the newly added memory, leave old data in */
577 	(void) memset(&newbuffer[sz], 0, newsz - sz);
578 
579 	oldkbuf = el->el_chared.c_kill.buf;
580 
581 	el->el_chared.c_kill.buf = newbuffer;
582 	el->el_chared.c_kill.last = newbuffer +
583 					(el->el_chared.c_kill.last - oldkbuf);
584 	el->el_chared.c_kill.mark = el->el_line.buffer +
585 					(el->el_chared.c_kill.mark - oldbuf);
586 
587 	/*
588 	 * Reallocate undo buffer.
589 	 */
590 	newbuffer = el_realloc(el->el_chared.c_undo.buf, newsz);
591 	if (!newbuffer)
592 		return 0;
593 
594 	/* zero the newly added memory, leave old data in */
595 	(void) memset(&newbuffer[sz], 0, newsz - sz);
596 	el->el_chared.c_undo.buf = newbuffer;
597 
598 	newbuffer = el_realloc(el->el_chared.c_redo.buf, newsz);
599 	if (!newbuffer)
600 		return 0;
601 	el->el_chared.c_redo.pos = newbuffer +
602 			(el->el_chared.c_redo.pos - el->el_chared.c_redo.buf);
603 	el->el_chared.c_redo.lim = newbuffer +
604 			(el->el_chared.c_redo.lim - el->el_chared.c_redo.buf);
605 	el->el_chared.c_redo.buf = newbuffer;
606 
607 	if (!hist_enlargebuf(el, sz, newsz))
608 		return 0;
609 
610 	/* Safe to set enlarged buffer size */
611 	el->el_line.limit  = &el->el_line.buffer[newsz - EL_LEAVE];
612 	return 1;
613 }
614 
615 /* ch_end():
616  *	Free the data structures used by the editor
617  */
618 protected void
619 ch_end(EditLine *el)
620 {
621 	el_free((ptr_t) el->el_line.buffer);
622 	el->el_line.buffer = NULL;
623 	el->el_line.limit = NULL;
624 	el_free((ptr_t) el->el_chared.c_undo.buf);
625 	el->el_chared.c_undo.buf = NULL;
626 	el_free((ptr_t) el->el_chared.c_redo.buf);
627 	el->el_chared.c_redo.buf = NULL;
628 	el->el_chared.c_redo.pos = NULL;
629 	el->el_chared.c_redo.lim = NULL;
630 	el->el_chared.c_redo.cmd = ED_UNASSIGNED;
631 	el_free((ptr_t) el->el_chared.c_kill.buf);
632 	el->el_chared.c_kill.buf = NULL;
633 	el_free((ptr_t) el->el_chared.c_macro.macro);
634 	el->el_chared.c_macro.macro = NULL;
635 	ch_reset(el);
636 }
637 
638 
639 /* el_insertstr():
640  *	Insert string at cursorI
641  */
642 public int
643 el_insertstr(EditLine *el, const char *s)
644 {
645 	size_t len;
646 
647 	if ((len = strlen(s)) == 0)
648 		return (-1);
649 	if (el->el_line.lastchar + len >= el->el_line.limit) {
650 		if (!ch_enlargebufs(el, len))
651 			return (-1);
652 	}
653 
654 	c_insert(el, (int)len);
655 	while (*s)
656 		*el->el_line.cursor++ = *s++;
657 	return (0);
658 }
659 
660 
661 /* el_deletestr():
662  *	Delete num characters before the cursor
663  */
664 public void
665 el_deletestr(EditLine *el, int n)
666 {
667 	if (n <= 0)
668 		return;
669 
670 	if (el->el_line.cursor < &el->el_line.buffer[n])
671 		return;
672 
673 	c_delbefore(el, n);		/* delete before dot */
674 	el->el_line.cursor -= n;
675 	if (el->el_line.cursor < el->el_line.buffer)
676 		el->el_line.cursor = el->el_line.buffer;
677 }
678 
679 /* c_gets():
680  *	Get a string
681  */
682 protected int
683 c_gets(EditLine *el, char *buf, const char *prompt)
684 {
685 	char ch;
686 	int len;
687 	char *cp = el->el_line.buffer;
688 
689 	if (prompt) {
690 		len = strlen(prompt);
691 		memcpy(cp, prompt, len + 0u);
692 		cp += len;
693 	}
694 	len = 0;
695 
696 	for (;;) {
697 		el->el_line.cursor = cp;
698 		*cp = ' ';
699 		el->el_line.lastchar = cp + 1;
700 		re_refresh(el);
701 
702 		if (el_getc(el, &ch) != 1) {
703 			ed_end_of_file(el, 0);
704 			len = -1;
705 			break;
706 		}
707 
708 		switch (ch) {
709 
710 		case 0010:	/* Delete and backspace */
711 		case 0177:
712 			if (len <= 0) {
713 				len = -1;
714 				break;
715 			}
716 			cp--;
717 			continue;
718 
719 		case 0033:	/* ESC */
720 		case '\r':	/* Newline */
721 		case '\n':
722 			buf[len] = ch;
723 			break;
724 
725 		default:
726 			if (len >= EL_BUFSIZ - 16)
727 				term_beep(el);
728 			else {
729 				buf[len++] = ch;
730 				*cp++ = ch;
731 			}
732 			continue;
733 		}
734 		break;
735 	}
736 
737 	el->el_line.buffer[0] = '\0';
738 	el->el_line.lastchar = el->el_line.buffer;
739 	el->el_line.cursor = el->el_line.buffer;
740 	return len;
741 }
742 
743 
744 /* c_hpos():
745  *	Return the current horizontal position of the cursor
746  */
747 protected int
748 c_hpos(EditLine *el)
749 {
750 	char *ptr;
751 
752 	/*
753 	 * Find how many characters till the beginning of this line.
754 	 */
755 	if (el->el_line.cursor == el->el_line.buffer)
756 		return (0);
757 	else {
758 		for (ptr = el->el_line.cursor - 1;
759 		     ptr >= el->el_line.buffer && *ptr != '\n';
760 		     ptr--)
761 			continue;
762 		return (el->el_line.cursor - ptr - 1);
763 	}
764 }
765