xref: /dragonfly/lib/libc/gen/fts.c (revision 4e7eb5cc)
1 /*-
2  * Copyright (c) 1990, 1993, 1994
3  *	The Regents of the University of California.  All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  * 3. All advertising materials mentioning features or use of this software
14  *    must display the following acknowledgement:
15  *	This product includes software developed by the University of
16  *	California, Berkeley and its contributors.
17  * 4. Neither the name of the University nor the names of its contributors
18  *    may be used to endorse or promote products derived from this software
19  *    without specific prior written permission.
20  *
21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31  * SUCH DAMAGE.
32  *
33  * $OpenBSD: fts.c,v 1.22 1999/10/03 19:22:22 millert Exp $
34  *
35  * $FreeBSD: src/lib/libc/gen/fts.c,v 1.14.2.4 2001/06/01 22:00:34 kris Exp $
36  * $DragonFly: src/lib/libc/gen/fts.c,v 1.3 2003/11/12 20:21:23 eirikn Exp $
37  *
38  * @(#)fts.c	8.6 (Berkeley) 8/14/94
39  * $FreeBSD: src/lib/libc/gen/fts.c,v 1.14.2.4 2001/06/01 22:00:34 kris Exp $
40  */
41 
42 #include <sys/param.h>
43 #include <sys/stat.h>
44 
45 #include <dirent.h>
46 #include <errno.h>
47 #include <fcntl.h>
48 #include <fts.h>
49 #include <stdlib.h>
50 #include <string.h>
51 #include <unistd.h>
52 
53 static FTSENT	*fts_alloc (FTS *, char *, int);
54 static FTSENT	*fts_build (FTS *, int);
55 static void	 fts_lfree (FTSENT *);
56 static void	 fts_load (FTS *, FTSENT *);
57 static size_t	 fts_maxarglen (char * const *);
58 static void	 fts_padjust (FTS *, FTSENT *);
59 static int	 fts_palloc (FTS *, size_t);
60 static FTSENT	*fts_sort (FTS *, FTSENT *, int);
61 static u_short	 fts_stat (FTS *, FTSENT *, int);
62 static int	 fts_safe_changedir (FTS *, FTSENT *, int, char *);
63 
64 #define	ISDOT(a)	(a[0] == '.' && (!a[1] || (a[1] == '.' && !a[2])))
65 
66 #define	CLR(opt)	(sp->fts_options &= ~(opt))
67 #define	ISSET(opt)	(sp->fts_options & (opt))
68 #define	SET(opt)	(sp->fts_options |= (opt))
69 
70 #define	FCHDIR(sp, fd)	(!ISSET(FTS_NOCHDIR) && fchdir(fd))
71 
72 /* fts_build flags */
73 #define	BCHILD		1		/* fts_children */
74 #define	BNAMES		2		/* fts_children, names only */
75 #define	BREAD		3		/* fts_read */
76 
77 FTS *
78 fts_open(argv, options, compar)
79 	char * const *argv;
80 	register int options;
81 	int (*compar) (const FTSENT **, const FTSENT **);
82 {
83 	register FTS *sp;
84 	register FTSENT *p, *root;
85 	register int nitems;
86 	FTSENT *parent, *tmp;
87 	int len;
88 
89 	/* Options check. */
90 	if (options & ~FTS_OPTIONMASK) {
91 		errno = EINVAL;
92 		return (NULL);
93 	}
94 
95 	/* Allocate/initialize the stream */
96 	if ((sp = malloc((u_int)sizeof(FTS))) == NULL)
97 		return (NULL);
98 	memset(sp, 0, sizeof(FTS));
99 	sp->fts_compar = compar;
100 	sp->fts_options = options;
101 
102 	/* Shush, GCC. */
103 	tmp = NULL;
104 
105 	/* Logical walks turn on NOCHDIR; symbolic links are too hard. */
106 	if (ISSET(FTS_LOGICAL))
107 		SET(FTS_NOCHDIR);
108 
109 	/*
110 	 * Start out with 1K of path space, and enough, in any case,
111 	 * to hold the user's paths.
112 	 */
113 	if (fts_palloc(sp, MAX(fts_maxarglen(argv), MAXPATHLEN)))
114 		goto mem1;
115 
116 	/* Allocate/initialize root's parent. */
117 	if ((parent = fts_alloc(sp, "", 0)) == NULL)
118 		goto mem2;
119 	parent->fts_level = FTS_ROOTPARENTLEVEL;
120 
121 	/* Allocate/initialize root(s). */
122 	for (root = NULL, nitems = 0; *argv != NULL; ++argv, ++nitems) {
123 		/* Don't allow zero-length paths. */
124 		if ((len = strlen(*argv)) == 0) {
125 			errno = ENOENT;
126 			goto mem3;
127 		}
128 
129 		p = fts_alloc(sp, *argv, len);
130 		p->fts_level = FTS_ROOTLEVEL;
131 		p->fts_parent = parent;
132 		p->fts_accpath = p->fts_name;
133 		p->fts_info = fts_stat(sp, p, ISSET(FTS_COMFOLLOW));
134 
135 		/* Command-line "." and ".." are real directories. */
136 		if (p->fts_info == FTS_DOT)
137 			p->fts_info = FTS_D;
138 
139 		/*
140 		 * If comparison routine supplied, traverse in sorted
141 		 * order; otherwise traverse in the order specified.
142 		 */
143 		if (compar) {
144 			p->fts_link = root;
145 			root = p;
146 		} else {
147 			p->fts_link = NULL;
148 			if (root == NULL)
149 				tmp = root = p;
150 			else {
151 				tmp->fts_link = p;
152 				tmp = p;
153 			}
154 		}
155 	}
156 	if (compar && nitems > 1)
157 		root = fts_sort(sp, root, nitems);
158 
159 	/*
160 	 * Allocate a dummy pointer and make fts_read think that we've just
161 	 * finished the node before the root(s); set p->fts_info to FTS_INIT
162 	 * so that everything about the "current" node is ignored.
163 	 */
164 	if ((sp->fts_cur = fts_alloc(sp, "", 0)) == NULL)
165 		goto mem3;
166 	sp->fts_cur->fts_link = root;
167 	sp->fts_cur->fts_info = FTS_INIT;
168 
169 	/*
170 	 * If using chdir(2), grab a file descriptor pointing to dot to ensure
171 	 * that we can get back here; this could be avoided for some paths,
172 	 * but almost certainly not worth the effort.  Slashes, symbolic links,
173 	 * and ".." are all fairly nasty problems.  Note, if we can't get the
174 	 * descriptor we run anyway, just more slowly.
175 	 */
176 	if (!ISSET(FTS_NOCHDIR) && (sp->fts_rfd = _open(".", O_RDONLY, 0)) < 0)
177 		SET(FTS_NOCHDIR);
178 
179 	return (sp);
180 
181 mem3:	fts_lfree(root);
182 	free(parent);
183 mem2:	free(sp->fts_path);
184 mem1:	free(sp);
185 	return (NULL);
186 }
187 
188 static void
189 fts_load(sp, p)
190 	FTS *sp;
191 	register FTSENT *p;
192 {
193 	register int len;
194 	register char *cp;
195 
196 	/*
197 	 * Load the stream structure for the next traversal.  Since we don't
198 	 * actually enter the directory until after the preorder visit, set
199 	 * the fts_accpath field specially so the chdir gets done to the right
200 	 * place and the user can access the first node.  From fts_open it's
201 	 * known that the path will fit.
202 	 */
203 	len = p->fts_pathlen = p->fts_namelen;
204 	memmove(sp->fts_path, p->fts_name, len + 1);
205 	if ((cp = strrchr(p->fts_name, '/')) && (cp != p->fts_name || cp[1])) {
206 		len = strlen(++cp);
207 		memmove(p->fts_name, cp, len + 1);
208 		p->fts_namelen = len;
209 	}
210 	p->fts_accpath = p->fts_path = sp->fts_path;
211 	sp->fts_dev = p->fts_dev;
212 }
213 
214 int
215 fts_close(sp)
216 	FTS *sp;
217 {
218 	register FTSENT *freep, *p;
219 	int saved_errno;
220 
221 	/*
222 	 * This still works if we haven't read anything -- the dummy structure
223 	 * points to the root list, so we step through to the end of the root
224 	 * list which has a valid parent pointer.
225 	 */
226 	if (sp->fts_cur) {
227 		for (p = sp->fts_cur; p->fts_level >= FTS_ROOTLEVEL;) {
228 			freep = p;
229 			p = p->fts_link != NULL ? p->fts_link : p->fts_parent;
230 			free(freep);
231 		}
232 		free(p);
233 	}
234 
235 	/* Free up child linked list, sort array, path buffer. */
236 	if (sp->fts_child)
237 		fts_lfree(sp->fts_child);
238 	if (sp->fts_array)
239 		free(sp->fts_array);
240 	free(sp->fts_path);
241 
242 	/* Return to original directory, save errno if necessary. */
243 	if (!ISSET(FTS_NOCHDIR)) {
244 		saved_errno = fchdir(sp->fts_rfd) ? errno : 0;
245 		(void)_close(sp->fts_rfd);
246 
247 		/* Set errno and return. */
248 		if (saved_errno != 0) {
249 			/* Free up the stream pointer. */
250 			free(sp);
251 			errno = saved_errno;
252 			return (-1);
253 		}
254 	}
255 
256 	/* Free up the stream pointer. */
257 	free(sp);
258 	return (0);
259 }
260 
261 /*
262  * Special case of "/" at the end of the path so that slashes aren't
263  * appended which would cause paths to be written as "....//foo".
264  */
265 #define	NAPPEND(p)							\
266 	(p->fts_path[p->fts_pathlen - 1] == '/'				\
267 	    ? p->fts_pathlen - 1 : p->fts_pathlen)
268 
269 FTSENT *
270 fts_read(sp)
271 	register FTS *sp;
272 {
273 	struct stat sb;
274 	register FTSENT *p, *tmp;
275 	register int instr;
276 	register char *t;
277 	int saved_errno;
278 
279 	/* If finished or unrecoverable error, return NULL. */
280 	if (sp->fts_cur == NULL || ISSET(FTS_STOP))
281 		return (NULL);
282 
283 	/* Set current node pointer. */
284 	p = sp->fts_cur;
285 
286 	/* Save and zero out user instructions. */
287 	instr = p->fts_instr;
288 	p->fts_instr = FTS_NOINSTR;
289 
290 	/* Any type of file may be re-visited; re-stat and re-turn. */
291 	if (instr == FTS_AGAIN) {
292 		p->fts_info = fts_stat(sp, p, 0);
293 		return (p);
294 	}
295 
296 	/*
297 	 * Following a symlink -- SLNONE test allows application to see
298 	 * SLNONE and recover.  If indirecting through a symlink, have
299 	 * keep a pointer to current location.  If unable to get that
300 	 * pointer, follow fails.
301 	 */
302 	if (instr == FTS_FOLLOW &&
303 	    (p->fts_info == FTS_SL || p->fts_info == FTS_SLNONE)) {
304 		p->fts_info = fts_stat(sp, p, 1);
305 		if (p->fts_info == FTS_D && !ISSET(FTS_NOCHDIR)) {
306 			if ((p->fts_symfd = _open(".", O_RDONLY, 0)) < 0) {
307 				p->fts_errno = errno;
308 				p->fts_info = FTS_ERR;
309 			} else
310 				p->fts_flags |= FTS_SYMFOLLOW;
311 		}
312 		return (p);
313 	}
314 
315 	/* Directory in pre-order. */
316 	if (p->fts_info == FTS_D) {
317 		/* If skipped or crossed mount point, do post-order visit. */
318 		if (instr == FTS_SKIP ||
319 		    (ISSET(FTS_XDEV) && p->fts_dev != sp->fts_dev)) {
320 			if (p->fts_flags & FTS_SYMFOLLOW)
321 				(void)_close(p->fts_symfd);
322 			if (sp->fts_child) {
323 				fts_lfree(sp->fts_child);
324 				sp->fts_child = NULL;
325 			}
326 			p->fts_info = FTS_DP;
327 			return (p);
328 		}
329 
330 		/* Rebuild if only read the names and now traversing. */
331 		if (sp->fts_child != NULL && ISSET(FTS_NAMEONLY)) {
332 			CLR(FTS_NAMEONLY);
333 			fts_lfree(sp->fts_child);
334 			sp->fts_child = NULL;
335 		}
336 
337 		/*
338 		 * Cd to the subdirectory.
339 		 *
340 		 * If have already read and now fail to chdir, whack the list
341 		 * to make the names come out right, and set the parent errno
342 		 * so the application will eventually get an error condition.
343 		 * Set the FTS_DONTCHDIR flag so that when we logically change
344 		 * directories back to the parent we don't do a chdir.
345 		 *
346 		 * If haven't read do so.  If the read fails, fts_build sets
347 		 * FTS_STOP or the fts_info field of the node.
348 		 */
349 		if (sp->fts_child != NULL) {
350 			if (fts_safe_changedir(sp, p, -1, p->fts_accpath)) {
351 				p->fts_errno = errno;
352 				p->fts_flags |= FTS_DONTCHDIR;
353 				for (p = sp->fts_child; p != NULL;
354 				    p = p->fts_link)
355 					p->fts_accpath =
356 					    p->fts_parent->fts_accpath;
357 			}
358 		} else if ((sp->fts_child = fts_build(sp, BREAD)) == NULL) {
359 			if (ISSET(FTS_STOP))
360 				return (NULL);
361 			return (p);
362 		}
363 		p = sp->fts_child;
364 		sp->fts_child = NULL;
365 		goto name;
366 	}
367 
368 	/* Move to the next node on this level. */
369 next:	tmp = p;
370 	if ((p = p->fts_link) != NULL) {
371 		free(tmp);
372 
373 		/*
374 		 * If reached the top, return to the original directory (or
375 		 * the root of the tree), and load the paths for the next root.
376 		 */
377 		if (p->fts_level == FTS_ROOTLEVEL) {
378 			if (FCHDIR(sp, sp->fts_rfd)) {
379 				SET(FTS_STOP);
380 				return (NULL);
381 			}
382 			fts_load(sp, p);
383 			return (sp->fts_cur = p);
384 		}
385 
386 		/*
387 		 * User may have called fts_set on the node.  If skipped,
388 		 * ignore.  If followed, get a file descriptor so we can
389 		 * get back if necessary.
390 		 */
391 		if (p->fts_instr == FTS_SKIP)
392 			goto next;
393 		if (p->fts_instr == FTS_FOLLOW) {
394 			p->fts_info = fts_stat(sp, p, 1);
395 			if (p->fts_info == FTS_D && !ISSET(FTS_NOCHDIR)) {
396 				if ((p->fts_symfd =
397 				    _open(".", O_RDONLY, 0)) < 0) {
398 					p->fts_errno = errno;
399 					p->fts_info = FTS_ERR;
400 				} else
401 					p->fts_flags |= FTS_SYMFOLLOW;
402 			}
403 			p->fts_instr = FTS_NOINSTR;
404 		}
405 
406 name:		t = sp->fts_path + NAPPEND(p->fts_parent);
407 		*t++ = '/';
408 		memmove(t, p->fts_name, p->fts_namelen + 1);
409 		return (sp->fts_cur = p);
410 	}
411 
412 	/* Move up to the parent node. */
413 	p = tmp->fts_parent;
414 	free(tmp);
415 
416 	if (p->fts_level == FTS_ROOTPARENTLEVEL) {
417 		/*
418 		 * Done; free everything up and set errno to 0 so the user
419 		 * can distinguish between error and EOF.
420 		 */
421 		free(p);
422 		errno = 0;
423 		return (sp->fts_cur = NULL);
424 	}
425 
426 	/* NUL terminate the pathname. */
427 	sp->fts_path[p->fts_pathlen] = '\0';
428 
429 	/*
430 	 * Return to the parent directory.  If at a root node or came through
431 	 * a symlink, go back through the file descriptor.  Otherwise, cd up
432 	 * one directory.
433 	 */
434 	if (p->fts_level == FTS_ROOTLEVEL) {
435 		if (FCHDIR(sp, sp->fts_rfd)) {
436 			SET(FTS_STOP);
437 			return (NULL);
438 		}
439 	} else if (p->fts_flags & FTS_SYMFOLLOW) {
440 		if (FCHDIR(sp, p->fts_symfd)) {
441 			saved_errno = errno;
442 			(void)_close(p->fts_symfd);
443 			errno = saved_errno;
444 			SET(FTS_STOP);
445 			return (NULL);
446 		}
447 		(void)_close(p->fts_symfd);
448 	} else if (!(p->fts_flags & FTS_DONTCHDIR) &&
449 		   fts_safe_changedir(sp, p->fts_parent, -1, "..")) {
450 		SET(FTS_STOP);
451 		return (NULL);
452 	}
453 	p->fts_info = p->fts_errno ? FTS_ERR : FTS_DP;
454 	return (sp->fts_cur = p);
455 }
456 
457 /*
458  * Fts_set takes the stream as an argument although it's not used in this
459  * implementation; it would be necessary if anyone wanted to add global
460  * semantics to fts using fts_set.  An error return is allowed for similar
461  * reasons.
462  */
463 /* ARGSUSED */
464 int
465 fts_set(sp, p, instr)
466 	FTS *sp;
467 	FTSENT *p;
468 	int instr;
469 {
470 	if (instr != 0 && instr != FTS_AGAIN && instr != FTS_FOLLOW &&
471 	    instr != FTS_NOINSTR && instr != FTS_SKIP) {
472 		errno = EINVAL;
473 		return (1);
474 	}
475 	p->fts_instr = instr;
476 	return (0);
477 }
478 
479 FTSENT *
480 fts_children(sp, instr)
481 	register FTS *sp;
482 	int instr;
483 {
484 	register FTSENT *p;
485 	int fd;
486 
487 	if (instr != 0 && instr != FTS_NAMEONLY) {
488 		errno = EINVAL;
489 		return (NULL);
490 	}
491 
492 	/* Set current node pointer. */
493 	p = sp->fts_cur;
494 
495 	/*
496 	 * Errno set to 0 so user can distinguish empty directory from
497 	 * an error.
498 	 */
499 	errno = 0;
500 
501 	/* Fatal errors stop here. */
502 	if (ISSET(FTS_STOP))
503 		return (NULL);
504 
505 	/* Return logical hierarchy of user's arguments. */
506 	if (p->fts_info == FTS_INIT)
507 		return (p->fts_link);
508 
509 	/*
510 	 * If not a directory being visited in pre-order, stop here.  Could
511 	 * allow FTS_DNR, assuming the user has fixed the problem, but the
512 	 * same effect is available with FTS_AGAIN.
513 	 */
514 	if (p->fts_info != FTS_D /* && p->fts_info != FTS_DNR */)
515 		return (NULL);
516 
517 	/* Free up any previous child list. */
518 	if (sp->fts_child != NULL)
519 		fts_lfree(sp->fts_child);
520 
521 	if (instr == FTS_NAMEONLY) {
522 		SET(FTS_NAMEONLY);
523 		instr = BNAMES;
524 	} else
525 		instr = BCHILD;
526 
527 	/*
528 	 * If using chdir on a relative path and called BEFORE fts_read does
529 	 * its chdir to the root of a traversal, we can lose -- we need to
530 	 * chdir into the subdirectory, and we don't know where the current
531 	 * directory is, so we can't get back so that the upcoming chdir by
532 	 * fts_read will work.
533 	 */
534 	if (p->fts_level != FTS_ROOTLEVEL || p->fts_accpath[0] == '/' ||
535 	    ISSET(FTS_NOCHDIR))
536 		return (sp->fts_child = fts_build(sp, instr));
537 
538 	if ((fd = _open(".", O_RDONLY, 0)) < 0)
539 		return (NULL);
540 	sp->fts_child = fts_build(sp, instr);
541 	if (fchdir(fd))
542 		return (NULL);
543 	(void)_close(fd);
544 	return (sp->fts_child);
545 }
546 
547 /*
548  * This is the tricky part -- do not casually change *anything* in here.  The
549  * idea is to build the linked list of entries that are used by fts_children
550  * and fts_read.  There are lots of special cases.
551  *
552  * The real slowdown in walking the tree is the stat calls.  If FTS_NOSTAT is
553  * set and it's a physical walk (so that symbolic links can't be directories),
554  * we can do things quickly.  First, if it's a 4.4BSD file system, the type
555  * of the file is in the directory entry.  Otherwise, we assume that the number
556  * of subdirectories in a node is equal to the number of links to the parent.
557  * The former skips all stat calls.  The latter skips stat calls in any leaf
558  * directories and for any files after the subdirectories in the directory have
559  * been found, cutting the stat calls by about 2/3.
560  */
561 static FTSENT *
562 fts_build(sp, type)
563 	register FTS *sp;
564 	int type;
565 {
566 	register struct dirent *dp;
567 	register FTSENT *p, *head;
568 	register int nitems;
569 	FTSENT *cur, *tail;
570 	DIR *dirp;
571 	void *oldaddr;
572 	int cderrno, descend, len, level, maxlen, nlinks, oflag, saved_errno,
573 	    nostat, doadjust;
574 	char *cp;
575 
576 	/* Set current node pointer. */
577 	cur = sp->fts_cur;
578 
579 	/*
580 	 * Open the directory for reading.  If this fails, we're done.
581 	 * If being called from fts_read, set the fts_info field.
582 	 */
583 #ifdef FTS_WHITEOUT
584 	if (ISSET(FTS_WHITEOUT))
585 		oflag = DTF_NODUP|DTF_REWIND;
586 	else
587 		oflag = DTF_HIDEW|DTF_NODUP|DTF_REWIND;
588 #else
589 #define __opendir2(path, flag) opendir(path)
590 #endif
591 	if ((dirp = __opendir2(cur->fts_accpath, oflag)) == NULL) {
592 		if (type == BREAD) {
593 			cur->fts_info = FTS_DNR;
594 			cur->fts_errno = errno;
595 		}
596 		return (NULL);
597 	}
598 
599 	/*
600 	 * Nlinks is the number of possible entries of type directory in the
601 	 * directory if we're cheating on stat calls, 0 if we're not doing
602 	 * any stat calls at all, -1 if we're doing stats on everything.
603 	 */
604 	if (type == BNAMES) {
605 		nlinks = 0;
606 		/* Be quiet about nostat, GCC. */
607 		nostat = 0;
608 	} else if (ISSET(FTS_NOSTAT) && ISSET(FTS_PHYSICAL)) {
609 		nlinks = cur->fts_nlink - (ISSET(FTS_SEEDOT) ? 0 : 2);
610 		nostat = 1;
611 	} else {
612 		nlinks = -1;
613 		nostat = 0;
614 	}
615 
616 #ifdef notdef
617 	(void)printf("nlinks == %d (cur: %d)\n", nlinks, cur->fts_nlink);
618 	(void)printf("NOSTAT %d PHYSICAL %d SEEDOT %d\n",
619 	    ISSET(FTS_NOSTAT), ISSET(FTS_PHYSICAL), ISSET(FTS_SEEDOT));
620 #endif
621 	/*
622 	 * If we're going to need to stat anything or we want to descend
623 	 * and stay in the directory, chdir.  If this fails we keep going,
624 	 * but set a flag so we don't chdir after the post-order visit.
625 	 * We won't be able to stat anything, but we can still return the
626 	 * names themselves.  Note, that since fts_read won't be able to
627 	 * chdir into the directory, it will have to return different path
628 	 * names than before, i.e. "a/b" instead of "b".  Since the node
629 	 * has already been visited in pre-order, have to wait until the
630 	 * post-order visit to return the error.  There is a special case
631 	 * here, if there was nothing to stat then it's not an error to
632 	 * not be able to stat.  This is all fairly nasty.  If a program
633 	 * needed sorted entries or stat information, they had better be
634 	 * checking FTS_NS on the returned nodes.
635 	 */
636 	cderrno = 0;
637 	if (nlinks || type == BREAD) {
638 		if (fts_safe_changedir(sp, cur, dirfd(dirp), NULL)) {
639 			if (nlinks && type == BREAD)
640 				cur->fts_errno = errno;
641 			cur->fts_flags |= FTS_DONTCHDIR;
642 			descend = 0;
643 			cderrno = errno;
644 			(void)closedir(dirp);
645 			dirp = NULL;
646 		} else
647 			descend = 1;
648 	} else
649 		descend = 0;
650 
651 	/*
652 	 * Figure out the max file name length that can be stored in the
653 	 * current path -- the inner loop allocates more path as necessary.
654 	 * We really wouldn't have to do the maxlen calculations here, we
655 	 * could do them in fts_read before returning the path, but it's a
656 	 * lot easier here since the length is part of the dirent structure.
657 	 *
658 	 * If not changing directories set a pointer so that can just append
659 	 * each new name into the path.
660 	 */
661 	len = NAPPEND(cur);
662 	if (ISSET(FTS_NOCHDIR)) {
663 		cp = sp->fts_path + len;
664 		*cp++ = '/';
665 	} else {
666 		/* GCC, you're too verbose. */
667 		cp = NULL;
668 	}
669 	len++;
670 	maxlen = sp->fts_pathlen - len;
671 
672 	level = cur->fts_level + 1;
673 
674 	/* Read the directory, attaching each entry to the `link' pointer. */
675 	doadjust = 0;
676 	for (head = tail = NULL, nitems = 0; dirp && (dp = readdir(dirp));) {
677 		if (!ISSET(FTS_SEEDOT) && ISDOT(dp->d_name))
678 			continue;
679 
680 		if ((p = fts_alloc(sp, dp->d_name, (int)dp->d_namlen)) == NULL)
681 			goto mem1;
682 		if (dp->d_namlen >= maxlen) {	/* include space for NUL */
683 			oldaddr = sp->fts_path;
684 			if (fts_palloc(sp, dp->d_namlen + len + 1)) {
685 				/*
686 				 * No more memory for path or structures.  Save
687 				 * errno, free up the current structure and the
688 				 * structures already allocated.
689 				 */
690 mem1:				saved_errno = errno;
691 				if (p)
692 					free(p);
693 				fts_lfree(head);
694 				(void)closedir(dirp);
695 				cur->fts_info = FTS_ERR;
696 				SET(FTS_STOP);
697 				errno = saved_errno;
698 				return (NULL);
699 			}
700 			/* Did realloc() change the pointer? */
701 			if (oldaddr != sp->fts_path) {
702 				doadjust = 1;
703 				if (ISSET(FTS_NOCHDIR))
704 					cp = sp->fts_path + len;
705 			}
706 			maxlen = sp->fts_pathlen - len;
707 		}
708 
709 		if (len + dp->d_namlen >= USHRT_MAX) {
710 			/*
711 			 * In an FTSENT, fts_pathlen is a u_short so it is
712 			 * possible to wraparound here.  If we do, free up
713 			 * the current structure and the structures already
714 			 * allocated, then error out with ENAMETOOLONG.
715 			 */
716 			free(p);
717 			fts_lfree(head);
718 			(void)closedir(dirp);
719 			cur->fts_info = FTS_ERR;
720 			SET(FTS_STOP);
721 			errno = ENAMETOOLONG;
722 			return (NULL);
723 		}
724 		p->fts_level = level;
725 		p->fts_parent = sp->fts_cur;
726 		p->fts_pathlen = len + dp->d_namlen;
727 
728 #ifdef FTS_WHITEOUT
729 		if (dp->d_type == DT_WHT)
730 			p->fts_flags |= FTS_ISW;
731 #endif
732 
733 		if (cderrno) {
734 			if (nlinks) {
735 				p->fts_info = FTS_NS;
736 				p->fts_errno = cderrno;
737 			} else
738 				p->fts_info = FTS_NSOK;
739 			p->fts_accpath = cur->fts_accpath;
740 		} else if (nlinks == 0
741 #ifdef DT_DIR
742 		    || (nostat &&
743 		    dp->d_type != DT_DIR && dp->d_type != DT_UNKNOWN)
744 #endif
745 		    ) {
746 			p->fts_accpath =
747 			    ISSET(FTS_NOCHDIR) ? p->fts_path : p->fts_name;
748 			p->fts_info = FTS_NSOK;
749 		} else {
750 			/* Build a file name for fts_stat to stat. */
751 			if (ISSET(FTS_NOCHDIR)) {
752 				p->fts_accpath = p->fts_path;
753 				memmove(cp, p->fts_name, p->fts_namelen + 1);
754 			} else
755 				p->fts_accpath = p->fts_name;
756 			/* Stat it. */
757 			p->fts_info = fts_stat(sp, p, 0);
758 
759 			/* Decrement link count if applicable. */
760 			if (nlinks > 0 && (p->fts_info == FTS_D ||
761 			    p->fts_info == FTS_DC || p->fts_info == FTS_DOT))
762 				--nlinks;
763 		}
764 
765 		/* We walk in directory order so "ls -f" doesn't get upset. */
766 		p->fts_link = NULL;
767 		if (head == NULL)
768 			head = tail = p;
769 		else {
770 			tail->fts_link = p;
771 			tail = p;
772 		}
773 		++nitems;
774 	}
775 	if (dirp)
776 		(void)closedir(dirp);
777 
778 	/*
779 	 * If realloc() changed the address of the path, adjust the
780 	 * addresses for the rest of the tree and the dir list.
781 	 */
782 	if (doadjust)
783 		fts_padjust(sp, head);
784 
785 	/*
786 	 * If not changing directories, reset the path back to original
787 	 * state.
788 	 */
789 	if (ISSET(FTS_NOCHDIR)) {
790 		if (len == sp->fts_pathlen || nitems == 0)
791 			--cp;
792 		*cp = '\0';
793 	}
794 
795 	/*
796 	 * If descended after called from fts_children or after called from
797 	 * fts_read and nothing found, get back.  At the root level we use
798 	 * the saved fd; if one of fts_open()'s arguments is a relative path
799 	 * to an empty directory, we wind up here with no other way back.  If
800 	 * can't get back, we're done.
801 	 */
802 	if (descend && (type == BCHILD || !nitems) &&
803 	    (cur->fts_level == FTS_ROOTLEVEL ?
804 	    FCHDIR(sp, sp->fts_rfd) :
805 	    fts_safe_changedir(sp, cur->fts_parent, -1, ".."))) {
806 		cur->fts_info = FTS_ERR;
807 		SET(FTS_STOP);
808 		return (NULL);
809 	}
810 
811 	/* If didn't find anything, return NULL. */
812 	if (!nitems) {
813 		if (type == BREAD)
814 			cur->fts_info = FTS_DP;
815 		return (NULL);
816 	}
817 
818 	/* Sort the entries. */
819 	if (sp->fts_compar && nitems > 1)
820 		head = fts_sort(sp, head, nitems);
821 	return (head);
822 }
823 
824 static u_short
825 fts_stat(sp, p, follow)
826 	FTS *sp;
827 	register FTSENT *p;
828 	int follow;
829 {
830 	register FTSENT *t;
831 	register dev_t dev;
832 	register ino_t ino;
833 	struct stat *sbp, sb;
834 	int saved_errno;
835 
836 	/* If user needs stat info, stat buffer already allocated. */
837 	sbp = ISSET(FTS_NOSTAT) ? &sb : p->fts_statp;
838 
839 #ifdef FTS_WHITEOUT
840 	/* check for whiteout */
841 	if (p->fts_flags & FTS_ISW) {
842 		if (sbp != &sb) {
843 			memset(sbp, '\0', sizeof (*sbp));
844 			sbp->st_mode = S_IFWHT;
845 		}
846 		return (FTS_W);
847 	}
848 #endif
849 
850 	/*
851 	 * If doing a logical walk, or application requested FTS_FOLLOW, do
852 	 * a stat(2).  If that fails, check for a non-existent symlink.  If
853 	 * fail, set the errno from the stat call.
854 	 */
855 	if (ISSET(FTS_LOGICAL) || follow) {
856 		if (stat(p->fts_accpath, sbp)) {
857 			saved_errno = errno;
858 			if (!lstat(p->fts_accpath, sbp)) {
859 				errno = 0;
860 				return (FTS_SLNONE);
861 			}
862 			p->fts_errno = saved_errno;
863 			goto err;
864 		}
865 	} else if (lstat(p->fts_accpath, sbp)) {
866 		p->fts_errno = errno;
867 err:		memset(sbp, 0, sizeof(struct stat));
868 		return (FTS_NS);
869 	}
870 
871 	if (S_ISDIR(sbp->st_mode)) {
872 		/*
873 		 * Set the device/inode.  Used to find cycles and check for
874 		 * crossing mount points.  Also remember the link count, used
875 		 * in fts_build to limit the number of stat calls.  It is
876 		 * understood that these fields are only referenced if fts_info
877 		 * is set to FTS_D.
878 		 */
879 		dev = p->fts_dev = sbp->st_dev;
880 		ino = p->fts_ino = sbp->st_ino;
881 		p->fts_nlink = sbp->st_nlink;
882 
883 		if (ISDOT(p->fts_name))
884 			return (FTS_DOT);
885 
886 		/*
887 		 * Cycle detection is done by brute force when the directory
888 		 * is first encountered.  If the tree gets deep enough or the
889 		 * number of symbolic links to directories is high enough,
890 		 * something faster might be worthwhile.
891 		 */
892 		for (t = p->fts_parent;
893 		    t->fts_level >= FTS_ROOTLEVEL; t = t->fts_parent)
894 			if (ino == t->fts_ino && dev == t->fts_dev) {
895 				p->fts_cycle = t;
896 				return (FTS_DC);
897 			}
898 		return (FTS_D);
899 	}
900 	if (S_ISLNK(sbp->st_mode))
901 		return (FTS_SL);
902 	if (S_ISREG(sbp->st_mode))
903 		return (FTS_F);
904 	return (FTS_DEFAULT);
905 }
906 
907 static FTSENT *
908 fts_sort(sp, head, nitems)
909 	FTS *sp;
910 	FTSENT *head;
911 	register int nitems;
912 {
913 	register FTSENT **ap, *p;
914 
915 	/*
916 	 * Construct an array of pointers to the structures and call qsort(3).
917 	 * Reassemble the array in the order returned by qsort.  If unable to
918 	 * sort for memory reasons, return the directory entries in their
919 	 * current order.  Allocate enough space for the current needs plus
920 	 * 40 so don't realloc one entry at a time.
921 	 */
922 	if (nitems > sp->fts_nitems) {
923 		sp->fts_nitems = nitems + 40;
924 		if ((sp->fts_array = reallocf(sp->fts_array,
925 		    sp->fts_nitems * sizeof(FTSENT *))) == NULL) {
926 			sp->fts_nitems = 0;
927 			return (head);
928 		}
929 	}
930 	for (ap = sp->fts_array, p = head; p; p = p->fts_link)
931 		*ap++ = p;
932 	qsort((void *)sp->fts_array, nitems, sizeof(FTSENT *), sp->fts_compar);
933 	for (head = *(ap = sp->fts_array); --nitems; ++ap)
934 		ap[0]->fts_link = ap[1];
935 	ap[0]->fts_link = NULL;
936 	return (head);
937 }
938 
939 static FTSENT *
940 fts_alloc(sp, name, namelen)
941 	FTS *sp;
942 	char *name;
943 	register int namelen;
944 {
945 	register FTSENT *p;
946 	size_t len;
947 
948 	/*
949 	 * The file name is a variable length array and no stat structure is
950 	 * necessary if the user has set the nostat bit.  Allocate the FTSENT
951 	 * structure, the file name and the stat structure in one chunk, but
952 	 * be careful that the stat structure is reasonably aligned.  Since the
953 	 * fts_name field is declared to be of size 1, the fts_name pointer is
954 	 * namelen + 2 before the first possible address of the stat structure.
955 	 */
956 	len = sizeof(FTSENT) + namelen;
957 	if (!ISSET(FTS_NOSTAT))
958 		len += sizeof(struct stat) + ALIGNBYTES;
959 	if ((p = malloc(len)) == NULL)
960 		return (NULL);
961 
962 	/* Copy the name and guarantee NUL termination. */
963 	memmove(p->fts_name, name, namelen);
964 	p->fts_name[namelen] = '\0';
965 
966 	if (!ISSET(FTS_NOSTAT))
967 		p->fts_statp = (struct stat *)ALIGN(p->fts_name + namelen + 2);
968 	p->fts_namelen = namelen;
969 	p->fts_path = sp->fts_path;
970 	p->fts_errno = 0;
971 	p->fts_flags = 0;
972 	p->fts_instr = FTS_NOINSTR;
973 	p->fts_number = 0;
974 	p->fts_pointer = NULL;
975 	return (p);
976 }
977 
978 static void
979 fts_lfree(head)
980 	register FTSENT *head;
981 {
982 	register FTSENT *p;
983 
984 	/* Free a linked list of structures. */
985 	while ((p = head)) {
986 		head = head->fts_link;
987 		free(p);
988 	}
989 }
990 
991 /*
992  * Allow essentially unlimited paths; find, rm, ls should all work on any tree.
993  * Most systems will allow creation of paths much longer than MAXPATHLEN, even
994  * though the kernel won't resolve them.  Add the size (not just what's needed)
995  * plus 256 bytes so don't realloc the path 2 bytes at a time.
996  */
997 static int
998 fts_palloc(sp, more)
999 	FTS *sp;
1000 	size_t more;
1001 {
1002 
1003 	sp->fts_pathlen += more + 256;
1004 	/*
1005 	 * Check for possible wraparound.  In an FTS, fts_pathlen is
1006 	 * a signed int but in an FTSENT it is an unsigned short.
1007 	 * We limit fts_pathlen to USHRT_MAX to be safe in both cases.
1008 	 */
1009 	if (sp->fts_pathlen < 0 || sp->fts_pathlen >= USHRT_MAX) {
1010 		if (sp->fts_path)
1011 			free(sp->fts_path);
1012 		sp->fts_path = NULL;
1013 		errno = ENAMETOOLONG;
1014 		return (1);
1015 	}
1016 	sp->fts_path = reallocf(sp->fts_path, sp->fts_pathlen);
1017 	return (sp->fts_path == NULL);
1018 }
1019 
1020 /*
1021  * When the path is realloc'd, have to fix all of the pointers in structures
1022  * already returned.
1023  */
1024 static void
1025 fts_padjust(sp, head)
1026 	FTS *sp;
1027 	FTSENT *head;
1028 {
1029 	FTSENT *p;
1030 	char *addr = sp->fts_path;
1031 
1032 #define	ADJUST(p) do {							\
1033 	if ((p)->fts_accpath != (p)->fts_name) {			\
1034 		(p)->fts_accpath =					\
1035 		    (char *)addr + ((p)->fts_accpath - (p)->fts_path);	\
1036 	}								\
1037 	(p)->fts_path = addr;						\
1038 } while (0)
1039 	/* Adjust the current set of children. */
1040 	for (p = sp->fts_child; p; p = p->fts_link)
1041 		ADJUST(p);
1042 
1043 	/* Adjust the rest of the tree, including the current level. */
1044 	for (p = head; p->fts_level >= FTS_ROOTLEVEL;) {
1045 		ADJUST(p);
1046 		p = p->fts_link ? p->fts_link : p->fts_parent;
1047 	}
1048 }
1049 
1050 static size_t
1051 fts_maxarglen(argv)
1052 	char * const *argv;
1053 {
1054 	size_t len, max;
1055 
1056 	for (max = 0; *argv; ++argv)
1057 		if ((len = strlen(*argv)) > max)
1058 			max = len;
1059 	return (max + 1);
1060 }
1061 
1062 /*
1063  * Change to dir specified by fd or p->fts_accpath without getting
1064  * tricked by someone changing the world out from underneath us.
1065  * Assumes p->fts_dev and p->fts_ino are filled in.
1066  */
1067 static int
1068 fts_safe_changedir(sp, p, fd, path)
1069 	FTS *sp;
1070 	FTSENT *p;
1071 	int fd;
1072 	char *path;
1073 {
1074 	int ret, oerrno, newfd;
1075 	struct stat sb;
1076 
1077 	newfd = fd;
1078 	if (ISSET(FTS_NOCHDIR))
1079 		return (0);
1080 	if (fd < 0 && (newfd = _open(path, O_RDONLY, 0)) < 0)
1081 		return (-1);
1082 	if (fstat(newfd, &sb)) {
1083 		ret = -1;
1084 		goto bail;
1085 	}
1086 	if (p->fts_dev != sb.st_dev || p->fts_ino != sb.st_ino) {
1087 		errno = ENOENT;		/* disinformation */
1088 		ret = -1;
1089 		goto bail;
1090 	}
1091 	ret = fchdir(newfd);
1092 bail:
1093 	oerrno = errno;
1094 	if (fd < 0)
1095 		(void)_close(newfd);
1096 	errno = oerrno;
1097 	return (ret);
1098 }
1099