xref: /freebsd/lib/libc/gen/fts.c (revision 6990ffd8a95caaba6858ad44ff1b3157d1efba8f)
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 
36 #if defined(LIBC_SCCS) && !defined(lint)
37 #if 0
38 static char sccsid[] = "@(#)fts.c	8.6 (Berkeley) 8/14/94";
39 #else
40 static char rcsid[] = "$FreeBSD$";
41 #endif
42 #endif /* LIBC_SCCS and not lint */
43 
44 #include "namespace.h"
45 #include <sys/types.h>
46 #include <sys/param.h>
47 #include <sys/stat.h>
48 
49 #include <dirent.h>
50 #include <errno.h>
51 #include <fcntl.h>
52 #include <fts.h>
53 #include <stdlib.h>
54 #include <string.h>
55 #include <unistd.h>
56 #include "un-namespace.h"
57 
58 static FTSENT	*fts_alloc __P((FTS *, char *, int));
59 static FTSENT	*fts_build __P((FTS *, int));
60 static void	 fts_lfree __P((FTSENT *));
61 static void	 fts_load __P((FTS *, FTSENT *));
62 static size_t	 fts_maxarglen __P((char * const *));
63 static void	 fts_padjust __P((FTS *, FTSENT *));
64 static int	 fts_palloc __P((FTS *, size_t));
65 static FTSENT	*fts_sort __P((FTS *, FTSENT *, int));
66 static u_short	 fts_stat __P((FTS *, FTSENT *, int));
67 static int	 fts_safe_changedir __P((FTS *, FTSENT *, int, char *));
68 
69 #define	ISDOT(a)	(a[0] == '.' && (!a[1] || (a[1] == '.' && !a[2])))
70 
71 #define	CLR(opt)	(sp->fts_options &= ~(opt))
72 #define	ISSET(opt)	(sp->fts_options & (opt))
73 #define	SET(opt)	(sp->fts_options |= (opt))
74 
75 #define	FCHDIR(sp, fd)	(!ISSET(FTS_NOCHDIR) && fchdir(fd))
76 
77 /* fts_build flags */
78 #define	BCHILD		1		/* fts_children */
79 #define	BNAMES		2		/* fts_children, names only */
80 #define	BREAD		3		/* fts_read */
81 
82 FTS *
83 fts_open(argv, options, compar)
84 	char * const *argv;
85 	register int options;
86 	int (*compar) __P((const FTSENT **, const FTSENT **));
87 {
88 	register FTS *sp;
89 	register FTSENT *p, *root;
90 	register int nitems;
91 	FTSENT *parent, *tmp;
92 	int len;
93 
94 	/* Options check. */
95 	if (options & ~FTS_OPTIONMASK) {
96 		errno = EINVAL;
97 		return (NULL);
98 	}
99 
100 	/* Allocate/initialize the stream */
101 	if ((sp = malloc((u_int)sizeof(FTS))) == NULL)
102 		return (NULL);
103 	memset(sp, 0, sizeof(FTS));
104 	sp->fts_compar = compar;
105 	sp->fts_options = options;
106 
107 	/* Shush, GCC. */
108 	tmp = NULL;
109 
110 	/* Logical walks turn on NOCHDIR; symbolic links are too hard. */
111 	if (ISSET(FTS_LOGICAL))
112 		SET(FTS_NOCHDIR);
113 
114 	/*
115 	 * Start out with 1K of path space, and enough, in any case,
116 	 * to hold the user's paths.
117 	 */
118 	if (fts_palloc(sp, MAX(fts_maxarglen(argv), MAXPATHLEN)))
119 		goto mem1;
120 
121 	/* Allocate/initialize root's parent. */
122 	if ((parent = fts_alloc(sp, "", 0)) == NULL)
123 		goto mem2;
124 	parent->fts_level = FTS_ROOTPARENTLEVEL;
125 
126 	/* Allocate/initialize root(s). */
127 	for (root = NULL, nitems = 0; *argv != NULL; ++argv, ++nitems) {
128 		/* Don't allow zero-length paths. */
129 		if ((len = strlen(*argv)) == 0) {
130 			errno = ENOENT;
131 			goto mem3;
132 		}
133 
134 		p = fts_alloc(sp, *argv, len);
135 		p->fts_level = FTS_ROOTLEVEL;
136 		p->fts_parent = parent;
137 		p->fts_accpath = p->fts_name;
138 		p->fts_info = fts_stat(sp, p, ISSET(FTS_COMFOLLOW));
139 
140 		/* Command-line "." and ".." are real directories. */
141 		if (p->fts_info == FTS_DOT)
142 			p->fts_info = FTS_D;
143 
144 		/*
145 		 * If comparison routine supplied, traverse in sorted
146 		 * order; otherwise traverse in the order specified.
147 		 */
148 		if (compar) {
149 			p->fts_link = root;
150 			root = p;
151 		} else {
152 			p->fts_link = NULL;
153 			if (root == NULL)
154 				tmp = root = p;
155 			else {
156 				tmp->fts_link = p;
157 				tmp = p;
158 			}
159 		}
160 	}
161 	if (compar && nitems > 1)
162 		root = fts_sort(sp, root, nitems);
163 
164 	/*
165 	 * Allocate a dummy pointer and make fts_read think that we've just
166 	 * finished the node before the root(s); set p->fts_info to FTS_INIT
167 	 * so that everything about the "current" node is ignored.
168 	 */
169 	if ((sp->fts_cur = fts_alloc(sp, "", 0)) == NULL)
170 		goto mem3;
171 	sp->fts_cur->fts_link = root;
172 	sp->fts_cur->fts_info = FTS_INIT;
173 
174 	/*
175 	 * If using chdir(2), grab a file descriptor pointing to dot to ensure
176 	 * that we can get back here; this could be avoided for some paths,
177 	 * but almost certainly not worth the effort.  Slashes, symbolic links,
178 	 * and ".." are all fairly nasty problems.  Note, if we can't get the
179 	 * descriptor we run anyway, just more slowly.
180 	 */
181 	if (!ISSET(FTS_NOCHDIR) && (sp->fts_rfd = _open(".", O_RDONLY, 0)) < 0)
182 		SET(FTS_NOCHDIR);
183 
184 	return (sp);
185 
186 mem3:	fts_lfree(root);
187 	free(parent);
188 mem2:	free(sp->fts_path);
189 mem1:	free(sp);
190 	return (NULL);
191 }
192 
193 static void
194 fts_load(sp, p)
195 	FTS *sp;
196 	register FTSENT *p;
197 {
198 	register int len;
199 	register char *cp;
200 
201 	/*
202 	 * Load the stream structure for the next traversal.  Since we don't
203 	 * actually enter the directory until after the preorder visit, set
204 	 * the fts_accpath field specially so the chdir gets done to the right
205 	 * place and the user can access the first node.  From fts_open it's
206 	 * known that the path will fit.
207 	 */
208 	len = p->fts_pathlen = p->fts_namelen;
209 	memmove(sp->fts_path, p->fts_name, len + 1);
210 	if ((cp = strrchr(p->fts_name, '/')) && (cp != p->fts_name || cp[1])) {
211 		len = strlen(++cp);
212 		memmove(p->fts_name, cp, len + 1);
213 		p->fts_namelen = len;
214 	}
215 	p->fts_accpath = p->fts_path = sp->fts_path;
216 	sp->fts_dev = p->fts_dev;
217 }
218 
219 int
220 fts_close(sp)
221 	FTS *sp;
222 {
223 	register FTSENT *freep, *p;
224 	int saved_errno;
225 
226 	/*
227 	 * This still works if we haven't read anything -- the dummy structure
228 	 * points to the root list, so we step through to the end of the root
229 	 * list which has a valid parent pointer.
230 	 */
231 	if (sp->fts_cur) {
232 		for (p = sp->fts_cur; p->fts_level >= FTS_ROOTLEVEL;) {
233 			freep = p;
234 			p = p->fts_link != NULL ? p->fts_link : p->fts_parent;
235 			free(freep);
236 		}
237 		free(p);
238 	}
239 
240 	/* Free up child linked list, sort array, path buffer. */
241 	if (sp->fts_child)
242 		fts_lfree(sp->fts_child);
243 	if (sp->fts_array)
244 		free(sp->fts_array);
245 	free(sp->fts_path);
246 
247 	/* Return to original directory, save errno if necessary. */
248 	if (!ISSET(FTS_NOCHDIR)) {
249 		saved_errno = fchdir(sp->fts_rfd) ? errno : 0;
250 		(void)_close(sp->fts_rfd);
251 
252 		/* Set errno and return. */
253 		if (saved_errno != 0) {
254 			/* Free up the stream pointer. */
255 			free(sp);
256 			errno = saved_errno;
257 			return (-1);
258 		}
259 	}
260 
261 	/* Free up the stream pointer. */
262 	free(sp);
263 	return (0);
264 }
265 
266 /*
267  * Special case of "/" at the end of the path so that slashes aren't
268  * appended which would cause paths to be written as "....//foo".
269  */
270 #define	NAPPEND(p)							\
271 	(p->fts_path[p->fts_pathlen - 1] == '/'				\
272 	    ? p->fts_pathlen - 1 : p->fts_pathlen)
273 
274 FTSENT *
275 fts_read(sp)
276 	register FTS *sp;
277 {
278 	struct stat sb;
279 	register FTSENT *p, *tmp;
280 	register int instr;
281 	register char *t;
282 	int saved_errno;
283 
284 	/* If finished or unrecoverable error, return NULL. */
285 	if (sp->fts_cur == NULL || ISSET(FTS_STOP))
286 		return (NULL);
287 
288 	/* Set current node pointer. */
289 	p = sp->fts_cur;
290 
291 	/* Save and zero out user instructions. */
292 	instr = p->fts_instr;
293 	p->fts_instr = FTS_NOINSTR;
294 
295 	/* Any type of file may be re-visited; re-stat and re-turn. */
296 	if (instr == FTS_AGAIN) {
297 		p->fts_info = fts_stat(sp, p, 0);
298 		return (p);
299 	}
300 
301 	/*
302 	 * Following a symlink -- SLNONE test allows application to see
303 	 * SLNONE and recover.  If indirecting through a symlink, have
304 	 * keep a pointer to current location.  If unable to get that
305 	 * pointer, follow fails.
306 	 */
307 	if (instr == FTS_FOLLOW &&
308 	    (p->fts_info == FTS_SL || p->fts_info == FTS_SLNONE)) {
309 		p->fts_info = fts_stat(sp, p, 1);
310 		if (p->fts_info == FTS_D && !ISSET(FTS_NOCHDIR)) {
311 			if ((p->fts_symfd = _open(".", O_RDONLY, 0)) < 0) {
312 				p->fts_errno = errno;
313 				p->fts_info = FTS_ERR;
314 			} else
315 				p->fts_flags |= FTS_SYMFOLLOW;
316 		}
317 		return (p);
318 	}
319 
320 	/* Directory in pre-order. */
321 	if (p->fts_info == FTS_D) {
322 		/* If skipped or crossed mount point, do post-order visit. */
323 		if (instr == FTS_SKIP ||
324 		    (ISSET(FTS_XDEV) && p->fts_dev != sp->fts_dev)) {
325 			if (p->fts_flags & FTS_SYMFOLLOW)
326 				(void)_close(p->fts_symfd);
327 			if (sp->fts_child) {
328 				fts_lfree(sp->fts_child);
329 				sp->fts_child = NULL;
330 			}
331 			p->fts_info = FTS_DP;
332 			return (p);
333 		}
334 
335 		/* Rebuild if only read the names and now traversing. */
336 		if (sp->fts_child != NULL && ISSET(FTS_NAMEONLY)) {
337 			CLR(FTS_NAMEONLY);
338 			fts_lfree(sp->fts_child);
339 			sp->fts_child = NULL;
340 		}
341 
342 		/*
343 		 * Cd to the subdirectory.
344 		 *
345 		 * If have already read and now fail to chdir, whack the list
346 		 * to make the names come out right, and set the parent errno
347 		 * so the application will eventually get an error condition.
348 		 * Set the FTS_DONTCHDIR flag so that when we logically change
349 		 * directories back to the parent we don't do a chdir.
350 		 *
351 		 * If haven't read do so.  If the read fails, fts_build sets
352 		 * FTS_STOP or the fts_info field of the node.
353 		 */
354 		if (sp->fts_child != NULL) {
355 			if (fts_safe_changedir(sp, p, -1, p->fts_accpath)) {
356 				p->fts_errno = errno;
357 				p->fts_flags |= FTS_DONTCHDIR;
358 				for (p = sp->fts_child; p != NULL;
359 				    p = p->fts_link)
360 					p->fts_accpath =
361 					    p->fts_parent->fts_accpath;
362 			}
363 		} else if ((sp->fts_child = fts_build(sp, BREAD)) == NULL) {
364 			if (ISSET(FTS_STOP))
365 				return (NULL);
366 			return (p);
367 		}
368 		p = sp->fts_child;
369 		sp->fts_child = NULL;
370 		goto name;
371 	}
372 
373 	/* Move to the next node on this level. */
374 next:	tmp = p;
375 	if ((p = p->fts_link) != NULL) {
376 		free(tmp);
377 
378 		/*
379 		 * If reached the top, return to the original directory (or
380 		 * the root of the tree), and load the paths for the next root.
381 		 */
382 		if (p->fts_level == FTS_ROOTLEVEL) {
383 			if (FCHDIR(sp, sp->fts_rfd)) {
384 				SET(FTS_STOP);
385 				return (NULL);
386 			}
387 			fts_load(sp, p);
388 			return (sp->fts_cur = p);
389 		}
390 
391 		/*
392 		 * User may have called fts_set on the node.  If skipped,
393 		 * ignore.  If followed, get a file descriptor so we can
394 		 * get back if necessary.
395 		 */
396 		if (p->fts_instr == FTS_SKIP)
397 			goto next;
398 		if (p->fts_instr == FTS_FOLLOW) {
399 			p->fts_info = fts_stat(sp, p, 1);
400 			if (p->fts_info == FTS_D && !ISSET(FTS_NOCHDIR)) {
401 				if ((p->fts_symfd =
402 				    _open(".", O_RDONLY, 0)) < 0) {
403 					p->fts_errno = errno;
404 					p->fts_info = FTS_ERR;
405 				} else
406 					p->fts_flags |= FTS_SYMFOLLOW;
407 			}
408 			p->fts_instr = FTS_NOINSTR;
409 		}
410 
411 name:		t = sp->fts_path + NAPPEND(p->fts_parent);
412 		*t++ = '/';
413 		memmove(t, p->fts_name, p->fts_namelen + 1);
414 		return (sp->fts_cur = p);
415 	}
416 
417 	/* Move up to the parent node. */
418 	p = tmp->fts_parent;
419 	free(tmp);
420 
421 	if (p->fts_level == FTS_ROOTPARENTLEVEL) {
422 		/*
423 		 * Done; free everything up and set errno to 0 so the user
424 		 * can distinguish between error and EOF.
425 		 */
426 		free(p);
427 		errno = 0;
428 		return (sp->fts_cur = NULL);
429 	}
430 
431 	/* NUL terminate the pathname. */
432 	sp->fts_path[p->fts_pathlen] = '\0';
433 
434 	/*
435 	 * Return to the parent directory.  If at a root node or came through
436 	 * a symlink, go back through the file descriptor.  Otherwise, cd up
437 	 * one directory.
438 	 */
439 	if (p->fts_level == FTS_ROOTLEVEL) {
440 		if (FCHDIR(sp, sp->fts_rfd)) {
441 			SET(FTS_STOP);
442 			return (NULL);
443 		}
444 	} else if (p->fts_flags & FTS_SYMFOLLOW) {
445 		if (FCHDIR(sp, p->fts_symfd)) {
446 			saved_errno = errno;
447 			(void)_close(p->fts_symfd);
448 			errno = saved_errno;
449 			SET(FTS_STOP);
450 			return (NULL);
451 		}
452 		(void)_close(p->fts_symfd);
453 	} else if (!(p->fts_flags & FTS_DONTCHDIR) &&
454 		   fts_safe_changedir(sp, p->fts_parent, -1, "..")) {
455 		SET(FTS_STOP);
456 		return (NULL);
457 	}
458 	p->fts_info = p->fts_errno ? FTS_ERR : FTS_DP;
459 	return (sp->fts_cur = p);
460 }
461 
462 /*
463  * Fts_set takes the stream as an argument although it's not used in this
464  * implementation; it would be necessary if anyone wanted to add global
465  * semantics to fts using fts_set.  An error return is allowed for similar
466  * reasons.
467  */
468 /* ARGSUSED */
469 int
470 fts_set(sp, p, instr)
471 	FTS *sp;
472 	FTSENT *p;
473 	int instr;
474 {
475 	if (instr != 0 && instr != FTS_AGAIN && instr != FTS_FOLLOW &&
476 	    instr != FTS_NOINSTR && instr != FTS_SKIP) {
477 		errno = EINVAL;
478 		return (1);
479 	}
480 	p->fts_instr = instr;
481 	return (0);
482 }
483 
484 FTSENT *
485 fts_children(sp, instr)
486 	register FTS *sp;
487 	int instr;
488 {
489 	register FTSENT *p;
490 	int fd;
491 
492 	if (instr != 0 && instr != FTS_NAMEONLY) {
493 		errno = EINVAL;
494 		return (NULL);
495 	}
496 
497 	/* Set current node pointer. */
498 	p = sp->fts_cur;
499 
500 	/*
501 	 * Errno set to 0 so user can distinguish empty directory from
502 	 * an error.
503 	 */
504 	errno = 0;
505 
506 	/* Fatal errors stop here. */
507 	if (ISSET(FTS_STOP))
508 		return (NULL);
509 
510 	/* Return logical hierarchy of user's arguments. */
511 	if (p->fts_info == FTS_INIT)
512 		return (p->fts_link);
513 
514 	/*
515 	 * If not a directory being visited in pre-order, stop here.  Could
516 	 * allow FTS_DNR, assuming the user has fixed the problem, but the
517 	 * same effect is available with FTS_AGAIN.
518 	 */
519 	if (p->fts_info != FTS_D /* && p->fts_info != FTS_DNR */)
520 		return (NULL);
521 
522 	/* Free up any previous child list. */
523 	if (sp->fts_child != NULL)
524 		fts_lfree(sp->fts_child);
525 
526 	if (instr == FTS_NAMEONLY) {
527 		SET(FTS_NAMEONLY);
528 		instr = BNAMES;
529 	} else
530 		instr = BCHILD;
531 
532 	/*
533 	 * If using chdir on a relative path and called BEFORE fts_read does
534 	 * its chdir to the root of a traversal, we can lose -- we need to
535 	 * chdir into the subdirectory, and we don't know where the current
536 	 * directory is, so we can't get back so that the upcoming chdir by
537 	 * fts_read will work.
538 	 */
539 	if (p->fts_level != FTS_ROOTLEVEL || p->fts_accpath[0] == '/' ||
540 	    ISSET(FTS_NOCHDIR))
541 		return (sp->fts_child = fts_build(sp, instr));
542 
543 	if ((fd = _open(".", O_RDONLY, 0)) < 0)
544 		return (NULL);
545 	sp->fts_child = fts_build(sp, instr);
546 	if (fchdir(fd))
547 		return (NULL);
548 	(void)_close(fd);
549 	return (sp->fts_child);
550 }
551 
552 /*
553  * This is the tricky part -- do not casually change *anything* in here.  The
554  * idea is to build the linked list of entries that are used by fts_children
555  * and fts_read.  There are lots of special cases.
556  *
557  * The real slowdown in walking the tree is the stat calls.  If FTS_NOSTAT is
558  * set and it's a physical walk (so that symbolic links can't be directories),
559  * we can do things quickly.  First, if it's a 4.4BSD file system, the type
560  * of the file is in the directory entry.  Otherwise, we assume that the number
561  * of subdirectories in a node is equal to the number of links to the parent.
562  * The former skips all stat calls.  The latter skips stat calls in any leaf
563  * directories and for any files after the subdirectories in the directory have
564  * been found, cutting the stat calls by about 2/3.
565  */
566 static FTSENT *
567 fts_build(sp, type)
568 	register FTS *sp;
569 	int type;
570 {
571 	register struct dirent *dp;
572 	register FTSENT *p, *head;
573 	register int nitems;
574 	FTSENT *cur, *tail;
575 	DIR *dirp;
576 	void *oldaddr;
577 	int cderrno, descend, len, level, maxlen, nlinks, oflag, saved_errno,
578 	    nostat, doadjust;
579 	char *cp;
580 
581 	/* Set current node pointer. */
582 	cur = sp->fts_cur;
583 
584 	/*
585 	 * Open the directory for reading.  If this fails, we're done.
586 	 * If being called from fts_read, set the fts_info field.
587 	 */
588 #ifdef FTS_WHITEOUT
589 	if (ISSET(FTS_WHITEOUT))
590 		oflag = DTF_NODUP|DTF_REWIND;
591 	else
592 		oflag = DTF_HIDEW|DTF_NODUP|DTF_REWIND;
593 #else
594 #define __opendir2(path, flag) opendir(path)
595 #endif
596 	if ((dirp = __opendir2(cur->fts_accpath, oflag)) == NULL) {
597 		if (type == BREAD) {
598 			cur->fts_info = FTS_DNR;
599 			cur->fts_errno = errno;
600 		}
601 		return (NULL);
602 	}
603 
604 	/*
605 	 * Nlinks is the number of possible entries of type directory in the
606 	 * directory if we're cheating on stat calls, 0 if we're not doing
607 	 * any stat calls at all, -1 if we're doing stats on everything.
608 	 */
609 	if (type == BNAMES) {
610 		nlinks = 0;
611 		/* Be quiet about nostat, GCC. */
612 		nostat = 0;
613 	} else if (ISSET(FTS_NOSTAT) && ISSET(FTS_PHYSICAL)) {
614 		nlinks = cur->fts_nlink - (ISSET(FTS_SEEDOT) ? 0 : 2);
615 		nostat = 1;
616 	} else {
617 		nlinks = -1;
618 		nostat = 0;
619 	}
620 
621 #ifdef notdef
622 	(void)printf("nlinks == %d (cur: %d)\n", nlinks, cur->fts_nlink);
623 	(void)printf("NOSTAT %d PHYSICAL %d SEEDOT %d\n",
624 	    ISSET(FTS_NOSTAT), ISSET(FTS_PHYSICAL), ISSET(FTS_SEEDOT));
625 #endif
626 	/*
627 	 * If we're going to need to stat anything or we want to descend
628 	 * and stay in the directory, chdir.  If this fails we keep going,
629 	 * but set a flag so we don't chdir after the post-order visit.
630 	 * We won't be able to stat anything, but we can still return the
631 	 * names themselves.  Note, that since fts_read won't be able to
632 	 * chdir into the directory, it will have to return different path
633 	 * names than before, i.e. "a/b" instead of "b".  Since the node
634 	 * has already been visited in pre-order, have to wait until the
635 	 * post-order visit to return the error.  There is a special case
636 	 * here, if there was nothing to stat then it's not an error to
637 	 * not be able to stat.  This is all fairly nasty.  If a program
638 	 * needed sorted entries or stat information, they had better be
639 	 * checking FTS_NS on the returned nodes.
640 	 */
641 	cderrno = 0;
642 	if (nlinks || type == BREAD) {
643 		if (fts_safe_changedir(sp, cur, dirfd(dirp), NULL)) {
644 			if (nlinks && type == BREAD)
645 				cur->fts_errno = errno;
646 			cur->fts_flags |= FTS_DONTCHDIR;
647 			descend = 0;
648 			cderrno = errno;
649 			(void)closedir(dirp);
650 			dirp = NULL;
651 		} else
652 			descend = 1;
653 	} else
654 		descend = 0;
655 
656 	/*
657 	 * Figure out the max file name length that can be stored in the
658 	 * current path -- the inner loop allocates more path as necessary.
659 	 * We really wouldn't have to do the maxlen calculations here, we
660 	 * could do them in fts_read before returning the path, but it's a
661 	 * lot easier here since the length is part of the dirent structure.
662 	 *
663 	 * If not changing directories set a pointer so that can just append
664 	 * each new name into the path.
665 	 */
666 	len = NAPPEND(cur);
667 	if (ISSET(FTS_NOCHDIR)) {
668 		cp = sp->fts_path + len;
669 		*cp++ = '/';
670 	} else {
671 		/* GCC, you're too verbose. */
672 		cp = NULL;
673 	}
674 	len++;
675 	maxlen = sp->fts_pathlen - len;
676 
677 	level = cur->fts_level + 1;
678 
679 	/* Read the directory, attaching each entry to the `link' pointer. */
680 	doadjust = 0;
681 	for (head = tail = NULL, nitems = 0; dirp && (dp = readdir(dirp));) {
682 		if (!ISSET(FTS_SEEDOT) && ISDOT(dp->d_name))
683 			continue;
684 
685 		if ((p = fts_alloc(sp, dp->d_name, (int)dp->d_namlen)) == NULL)
686 			goto mem1;
687 		if (dp->d_namlen >= maxlen) {	/* include space for NUL */
688 			oldaddr = sp->fts_path;
689 			if (fts_palloc(sp, dp->d_namlen + len + 1)) {
690 				/*
691 				 * No more memory for path or structures.  Save
692 				 * errno, free up the current structure and the
693 				 * structures already allocated.
694 				 */
695 mem1:				saved_errno = errno;
696 				if (p)
697 					free(p);
698 				fts_lfree(head);
699 				(void)closedir(dirp);
700 				cur->fts_info = FTS_ERR;
701 				SET(FTS_STOP);
702 				errno = saved_errno;
703 				return (NULL);
704 			}
705 			/* Did realloc() change the pointer? */
706 			if (oldaddr != sp->fts_path) {
707 				doadjust = 1;
708 				if (ISSET(FTS_NOCHDIR))
709 					cp = sp->fts_path + len;
710 			}
711 			maxlen = sp->fts_pathlen - len;
712 		}
713 
714 		if (len + dp->d_namlen >= USHRT_MAX) {
715 			/*
716 			 * In an FTSENT, fts_pathlen is a u_short so it is
717 			 * possible to wraparound here.  If we do, free up
718 			 * the current structure and the structures already
719 			 * allocated, then error out with ENAMETOOLONG.
720 			 */
721 			free(p);
722 			fts_lfree(head);
723 			(void)closedir(dirp);
724 			cur->fts_info = FTS_ERR;
725 			SET(FTS_STOP);
726 			errno = ENAMETOOLONG;
727 			return (NULL);
728 		}
729 		p->fts_level = level;
730 		p->fts_parent = sp->fts_cur;
731 		p->fts_pathlen = len + dp->d_namlen;
732 
733 #ifdef FTS_WHITEOUT
734 		if (dp->d_type == DT_WHT)
735 			p->fts_flags |= FTS_ISW;
736 #endif
737 
738 		if (cderrno) {
739 			if (nlinks) {
740 				p->fts_info = FTS_NS;
741 				p->fts_errno = cderrno;
742 			} else
743 				p->fts_info = FTS_NSOK;
744 			p->fts_accpath = cur->fts_accpath;
745 		} else if (nlinks == 0
746 #ifdef DT_DIR
747 		    || (nostat &&
748 		    dp->d_type != DT_DIR && dp->d_type != DT_UNKNOWN)
749 #endif
750 		    ) {
751 			p->fts_accpath =
752 			    ISSET(FTS_NOCHDIR) ? p->fts_path : p->fts_name;
753 			p->fts_info = FTS_NSOK;
754 		} else {
755 			/* Build a file name for fts_stat to stat. */
756 			if (ISSET(FTS_NOCHDIR)) {
757 				p->fts_accpath = p->fts_path;
758 				memmove(cp, p->fts_name, p->fts_namelen + 1);
759 			} else
760 				p->fts_accpath = p->fts_name;
761 			/* Stat it. */
762 			p->fts_info = fts_stat(sp, p, 0);
763 
764 			/* Decrement link count if applicable. */
765 			if (nlinks > 0 && (p->fts_info == FTS_D ||
766 			    p->fts_info == FTS_DC || p->fts_info == FTS_DOT))
767 				--nlinks;
768 		}
769 
770 		/* We walk in directory order so "ls -f" doesn't get upset. */
771 		p->fts_link = NULL;
772 		if (head == NULL)
773 			head = tail = p;
774 		else {
775 			tail->fts_link = p;
776 			tail = p;
777 		}
778 		++nitems;
779 	}
780 	if (dirp)
781 		(void)closedir(dirp);
782 
783 	/*
784 	 * If realloc() changed the address of the path, adjust the
785 	 * addresses for the rest of the tree and the dir list.
786 	 */
787 	if (doadjust)
788 		fts_padjust(sp, head);
789 
790 	/*
791 	 * If not changing directories, reset the path back to original
792 	 * state.
793 	 */
794 	if (ISSET(FTS_NOCHDIR)) {
795 		if (len == sp->fts_pathlen || nitems == 0)
796 			--cp;
797 		*cp = '\0';
798 	}
799 
800 	/*
801 	 * If descended after called from fts_children or after called from
802 	 * fts_read and nothing found, get back.  At the root level we use
803 	 * the saved fd; if one of fts_open()'s arguments is a relative path
804 	 * to an empty directory, we wind up here with no other way back.  If
805 	 * can't get back, we're done.
806 	 */
807 	if (descend && (type == BCHILD || !nitems) &&
808 	    (cur->fts_level == FTS_ROOTLEVEL ?
809 	    FCHDIR(sp, sp->fts_rfd) :
810 	    fts_safe_changedir(sp, cur->fts_parent, -1, ".."))) {
811 		cur->fts_info = FTS_ERR;
812 		SET(FTS_STOP);
813 		return (NULL);
814 	}
815 
816 	/* If didn't find anything, return NULL. */
817 	if (!nitems) {
818 		if (type == BREAD)
819 			cur->fts_info = FTS_DP;
820 		return (NULL);
821 	}
822 
823 	/* Sort the entries. */
824 	if (sp->fts_compar && nitems > 1)
825 		head = fts_sort(sp, head, nitems);
826 	return (head);
827 }
828 
829 static u_short
830 fts_stat(sp, p, follow)
831 	FTS *sp;
832 	register FTSENT *p;
833 	int follow;
834 {
835 	register FTSENT *t;
836 	register dev_t dev;
837 	register ino_t ino;
838 	struct stat *sbp, sb;
839 	int saved_errno;
840 
841 	/* If user needs stat info, stat buffer already allocated. */
842 	sbp = ISSET(FTS_NOSTAT) ? &sb : p->fts_statp;
843 
844 #ifdef FTS_WHITEOUT
845 	/* check for whiteout */
846 	if (p->fts_flags & FTS_ISW) {
847 		if (sbp != &sb) {
848 			memset(sbp, '\0', sizeof (*sbp));
849 			sbp->st_mode = S_IFWHT;
850 		}
851 		return (FTS_W);
852 	}
853 #endif
854 
855 	/*
856 	 * If doing a logical walk, or application requested FTS_FOLLOW, do
857 	 * a stat(2).  If that fails, check for a non-existent symlink.  If
858 	 * fail, set the errno from the stat call.
859 	 */
860 	if (ISSET(FTS_LOGICAL) || follow) {
861 		if (stat(p->fts_accpath, sbp)) {
862 			saved_errno = errno;
863 			if (!lstat(p->fts_accpath, sbp)) {
864 				errno = 0;
865 				return (FTS_SLNONE);
866 			}
867 			p->fts_errno = saved_errno;
868 			goto err;
869 		}
870 	} else if (lstat(p->fts_accpath, sbp)) {
871 		p->fts_errno = errno;
872 err:		memset(sbp, 0, sizeof(struct stat));
873 		return (FTS_NS);
874 	}
875 
876 	if (S_ISDIR(sbp->st_mode)) {
877 		/*
878 		 * Set the device/inode.  Used to find cycles and check for
879 		 * crossing mount points.  Also remember the link count, used
880 		 * in fts_build to limit the number of stat calls.  It is
881 		 * understood that these fields are only referenced if fts_info
882 		 * is set to FTS_D.
883 		 */
884 		dev = p->fts_dev = sbp->st_dev;
885 		ino = p->fts_ino = sbp->st_ino;
886 		p->fts_nlink = sbp->st_nlink;
887 
888 		if (ISDOT(p->fts_name))
889 			return (FTS_DOT);
890 
891 		/*
892 		 * Cycle detection is done by brute force when the directory
893 		 * is first encountered.  If the tree gets deep enough or the
894 		 * number of symbolic links to directories is high enough,
895 		 * something faster might be worthwhile.
896 		 */
897 		for (t = p->fts_parent;
898 		    t->fts_level >= FTS_ROOTLEVEL; t = t->fts_parent)
899 			if (ino == t->fts_ino && dev == t->fts_dev) {
900 				p->fts_cycle = t;
901 				return (FTS_DC);
902 			}
903 		return (FTS_D);
904 	}
905 	if (S_ISLNK(sbp->st_mode))
906 		return (FTS_SL);
907 	if (S_ISREG(sbp->st_mode))
908 		return (FTS_F);
909 	return (FTS_DEFAULT);
910 }
911 
912 static FTSENT *
913 fts_sort(sp, head, nitems)
914 	FTS *sp;
915 	FTSENT *head;
916 	register int nitems;
917 {
918 	register FTSENT **ap, *p;
919 
920 	/*
921 	 * Construct an array of pointers to the structures and call qsort(3).
922 	 * Reassemble the array in the order returned by qsort.  If unable to
923 	 * sort for memory reasons, return the directory entries in their
924 	 * current order.  Allocate enough space for the current needs plus
925 	 * 40 so don't realloc one entry at a time.
926 	 */
927 	if (nitems > sp->fts_nitems) {
928 		sp->fts_nitems = nitems + 40;
929 		if ((sp->fts_array = reallocf(sp->fts_array,
930 		    sp->fts_nitems * sizeof(FTSENT *))) == NULL) {
931 			sp->fts_nitems = 0;
932 			return (head);
933 		}
934 	}
935 	for (ap = sp->fts_array, p = head; p; p = p->fts_link)
936 		*ap++ = p;
937 	qsort((void *)sp->fts_array, nitems, sizeof(FTSENT *), sp->fts_compar);
938 	for (head = *(ap = sp->fts_array); --nitems; ++ap)
939 		ap[0]->fts_link = ap[1];
940 	ap[0]->fts_link = NULL;
941 	return (head);
942 }
943 
944 static FTSENT *
945 fts_alloc(sp, name, namelen)
946 	FTS *sp;
947 	char *name;
948 	register int namelen;
949 {
950 	register FTSENT *p;
951 	size_t len;
952 
953 	/*
954 	 * The file name is a variable length array and no stat structure is
955 	 * necessary if the user has set the nostat bit.  Allocate the FTSENT
956 	 * structure, the file name and the stat structure in one chunk, but
957 	 * be careful that the stat structure is reasonably aligned.  Since the
958 	 * fts_name field is declared to be of size 1, the fts_name pointer is
959 	 * namelen + 2 before the first possible address of the stat structure.
960 	 */
961 	len = sizeof(FTSENT) + namelen;
962 	if (!ISSET(FTS_NOSTAT))
963 		len += sizeof(struct stat) + ALIGNBYTES;
964 	if ((p = malloc(len)) == NULL)
965 		return (NULL);
966 
967 	/* Copy the name and guarantee NUL termination. */
968 	memmove(p->fts_name, name, namelen);
969 	p->fts_name[namelen] = '\0';
970 
971 	if (!ISSET(FTS_NOSTAT))
972 		p->fts_statp = (struct stat *)ALIGN(p->fts_name + namelen + 2);
973 	p->fts_namelen = namelen;
974 	p->fts_path = sp->fts_path;
975 	p->fts_errno = 0;
976 	p->fts_flags = 0;
977 	p->fts_instr = FTS_NOINSTR;
978 	p->fts_number = 0;
979 	p->fts_pointer = NULL;
980 	return (p);
981 }
982 
983 static void
984 fts_lfree(head)
985 	register FTSENT *head;
986 {
987 	register FTSENT *p;
988 
989 	/* Free a linked list of structures. */
990 	while ((p = head)) {
991 		head = head->fts_link;
992 		free(p);
993 	}
994 }
995 
996 /*
997  * Allow essentially unlimited paths; find, rm, ls should all work on any tree.
998  * Most systems will allow creation of paths much longer than MAXPATHLEN, even
999  * though the kernel won't resolve them.  Add the size (not just what's needed)
1000  * plus 256 bytes so don't realloc the path 2 bytes at a time.
1001  */
1002 static int
1003 fts_palloc(sp, more)
1004 	FTS *sp;
1005 	size_t more;
1006 {
1007 
1008 	sp->fts_pathlen += more + 256;
1009 	/*
1010 	 * Check for possible wraparound.  In an FTS, fts_pathlen is
1011 	 * a signed int but in an FTSENT it is an unsigned short.
1012 	 * We limit fts_pathlen to USHRT_MAX to be safe in both cases.
1013 	 */
1014 	if (sp->fts_pathlen < 0 || sp->fts_pathlen >= USHRT_MAX) {
1015 		if (sp->fts_path)
1016 			free(sp->fts_path);
1017 		sp->fts_path = NULL;
1018 		errno = ENAMETOOLONG;
1019 		return (1);
1020 	}
1021 	sp->fts_path = reallocf(sp->fts_path, sp->fts_pathlen);
1022 	return (sp->fts_path == NULL);
1023 }
1024 
1025 /*
1026  * When the path is realloc'd, have to fix all of the pointers in structures
1027  * already returned.
1028  */
1029 static void
1030 fts_padjust(sp, head)
1031 	FTS *sp;
1032 	FTSENT *head;
1033 {
1034 	FTSENT *p;
1035 	char *addr = sp->fts_path;
1036 
1037 #define	ADJUST(p) do {							\
1038 	if ((p)->fts_accpath != (p)->fts_name) {			\
1039 		(p)->fts_accpath =					\
1040 		    (char *)addr + ((p)->fts_accpath - (p)->fts_path);	\
1041 	}								\
1042 	(p)->fts_path = addr;						\
1043 } while (0)
1044 	/* Adjust the current set of children. */
1045 	for (p = sp->fts_child; p; p = p->fts_link)
1046 		ADJUST(p);
1047 
1048 	/* Adjust the rest of the tree, including the current level. */
1049 	for (p = head; p->fts_level >= FTS_ROOTLEVEL;) {
1050 		ADJUST(p);
1051 		p = p->fts_link ? p->fts_link : p->fts_parent;
1052 	}
1053 }
1054 
1055 static size_t
1056 fts_maxarglen(argv)
1057 	char * const *argv;
1058 {
1059 	size_t len, max;
1060 
1061 	for (max = 0; *argv; ++argv)
1062 		if ((len = strlen(*argv)) > max)
1063 			max = len;
1064 	return (max + 1);
1065 }
1066 
1067 /*
1068  * Change to dir specified by fd or p->fts_accpath without getting
1069  * tricked by someone changing the world out from underneath us.
1070  * Assumes p->fts_dev and p->fts_ino are filled in.
1071  */
1072 static int
1073 fts_safe_changedir(sp, p, fd, path)
1074 	FTS *sp;
1075 	FTSENT *p;
1076 	int fd;
1077 	char *path;
1078 {
1079 	int ret, oerrno, newfd;
1080 	struct stat sb;
1081 
1082 	newfd = fd;
1083 	if (ISSET(FTS_NOCHDIR))
1084 		return (0);
1085 	if (fd < 0 && (newfd = _open(path, O_RDONLY, 0)) < 0)
1086 		return (-1);
1087 	if (_fstat(newfd, &sb)) {
1088 		ret = -1;
1089 		goto bail;
1090 	}
1091 	if (p->fts_dev != sb.st_dev || p->fts_ino != sb.st_ino) {
1092 		errno = ENOENT;		/* disinformation */
1093 		ret = -1;
1094 		goto bail;
1095 	}
1096 	ret = fchdir(newfd);
1097 bail:
1098 	oerrno = errno;
1099 	if (fd < 0)
1100 		(void)_close(newfd);
1101 	errno = oerrno;
1102 	return (ret);
1103 }
1104