opendir.c revision 56698 
1/*
2 * Copyright (c) 1983, 1993
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 * $FreeBSD: head/lib/libc/gen/opendir.c 56698 2000-01-27 23:07:25Z jasone $
34 */
35
36#if defined(LIBC_SCCS) && !defined(lint)
37static char sccsid[] = "@(#)opendir.c	8.8 (Berkeley) 5/1/95";
38#endif /* LIBC_SCCS and not lint */
39
40#include <sys/param.h>
41#include <sys/mount.h>
42#include <sys/stat.h>
43
44#include <dirent.h>
45#include <errno.h>
46#include <fcntl.h>
47#include <stdlib.h>
48#include <unistd.h>
49
50/*
51 * Open a directory.
52 */
53DIR *
54opendir(name)
55	const char *name;
56{
57
58	return (__opendir2(name, DTF_HIDEW|DTF_NODUP));
59}
60
61DIR *
62__opendir2(name, flags)
63	const char *name;
64	int flags;
65{
66	DIR *dirp;
67	int fd;
68	int incr;
69	int saved_errno;
70	int unionstack;
71	struct stat statb;
72
73	/*
74	 * stat() before open() because opening of special files may be
75	 * harmful.  fstat() after open because the file may have changed.
76	 */
77	if (stat(name, &statb) != 0)
78		return (NULL);
79	if (!S_ISDIR(statb.st_mode)) {
80		errno = ENOTDIR;
81		return (NULL);
82	}
83	if ((fd = _open(name, O_RDONLY | O_NONBLOCK)) == -1)
84		return (NULL);
85	dirp = NULL;
86	if (fstat(fd, &statb) != 0)
87		goto fail;
88	if (!S_ISDIR(statb.st_mode)) {
89		errno = ENOTDIR;
90		goto fail;
91	}
92	if (_fcntl(fd, F_SETFD, FD_CLOEXEC) == -1 ||
93	    (dirp = malloc(sizeof(DIR))) == NULL)
94		goto fail;
95
96	/*
97	 * Use the system page size if that is a multiple of DIRBLKSIZ.
98	 * Hopefully this can be a big win someday by allowing page
99	 * trades to user space to be done by getdirentries().
100	 */
101	incr = getpagesize();
102	if ((incr % DIRBLKSIZ) != 0)
103		incr = DIRBLKSIZ;
104
105	/*
106	 * Determine whether this directory is the top of a union stack.
107	 */
108	if (flags & DTF_NODUP) {
109		struct statfs sfb;
110
111		if (fstatfs(fd, &sfb) < 0)
112			goto fail;
113		unionstack = !strcmp(sfb.f_fstypename, "union");
114	} else {
115		unionstack = 0;
116	}
117
118	if (unionstack) {
119		int len = 0;
120		int space = 0;
121		char *buf = 0;
122		char *ddptr = 0;
123		char *ddeptr;
124		int n;
125		struct dirent **dpv;
126
127		/*
128		 * The strategy here is to read all the directory
129		 * entries into a buffer, sort the buffer, and
130		 * remove duplicate entries by setting the inode
131		 * number to zero.
132		 */
133
134		do {
135			/*
136			 * Always make at least DIRBLKSIZ bytes
137			 * available to getdirentries
138			 */
139			if (space < DIRBLKSIZ) {
140				space += incr;
141				len += incr;
142				buf = reallocf(buf, len);
143				if (buf == NULL)
144					goto fail;
145				ddptr = buf + (len - space);
146			}
147
148			n = getdirentries(fd, ddptr, space, &dirp->dd_seek);
149			if (n > 0) {
150				ddptr += n;
151				space -= n;
152			}
153		} while (n > 0);
154
155		ddeptr = ddptr;
156		flags |= __DTF_READALL;
157
158		/*
159		 * Re-open the directory.
160		 * This has the effect of rewinding back to the
161		 * top of the union stack and is needed by
162		 * programs which plan to fchdir to a descriptor
163		 * which has also been read -- see fts.c.
164		 */
165		if (flags & DTF_REWIND) {
166			(void)_close(fd);
167			if ((fd = _open(name, O_RDONLY)) == -1) {
168				saved_errno = errno;
169				free(buf);
170				free(dirp);
171				errno = saved_errno;
172				return (NULL);
173			}
174		}
175
176		/*
177		 * There is now a buffer full of (possibly) duplicate
178		 * names.
179		 */
180		dirp->dd_buf = buf;
181
182		/*
183		 * Go round this loop twice...
184		 *
185		 * Scan through the buffer, counting entries.
186		 * On the second pass, save pointers to each one.
187		 * Then sort the pointers and remove duplicate names.
188		 */
189		for (dpv = 0;;) {
190			n = 0;
191			ddptr = buf;
192			while (ddptr < ddeptr) {
193				struct dirent *dp;
194
195				dp = (struct dirent *) ddptr;
196				if ((long)dp & 03L)
197					break;
198				if ((dp->d_reclen <= 0) ||
199				    (dp->d_reclen > (ddeptr + 1 - ddptr)))
200					break;
201				ddptr += dp->d_reclen;
202				if (dp->d_fileno) {
203					if (dpv)
204						dpv[n] = dp;
205					n++;
206				}
207			}
208
209			if (dpv) {
210				struct dirent *xp;
211
212				/*
213				 * This sort must be stable.
214				 */
215				mergesort(dpv, n, sizeof(*dpv), alphasort);
216
217				dpv[n] = NULL;
218				xp = NULL;
219
220				/*
221				 * Scan through the buffer in sort order,
222				 * zapping the inode number of any
223				 * duplicate names.
224				 */
225				for (n = 0; dpv[n]; n++) {
226					struct dirent *dp = dpv[n];
227
228					if ((xp == NULL) ||
229					    strcmp(dp->d_name, xp->d_name)) {
230						xp = dp;
231					} else {
232						dp->d_fileno = 0;
233					}
234					if (dp->d_type == DT_WHT &&
235					    (flags & DTF_HIDEW))
236						dp->d_fileno = 0;
237				}
238
239				free(dpv);
240				break;
241			} else {
242				dpv = malloc((n+1) * sizeof(struct dirent *));
243				if (dpv == NULL)
244					break;
245			}
246		}
247
248		dirp->dd_len = len;
249		dirp->dd_size = ddptr - dirp->dd_buf;
250	} else {
251		dirp->dd_len = incr;
252		dirp->dd_buf = malloc(dirp->dd_len);
253		if (dirp->dd_buf == NULL)
254			goto fail;
255		dirp->dd_seek = 0;
256		flags &= ~DTF_REWIND;
257	}
258
259	dirp->dd_loc = 0;
260	dirp->dd_fd = fd;
261	dirp->dd_flags = flags;
262
263	/*
264	 * Set up seek point for rewinddir.
265	 */
266	dirp->dd_rewind = telldir(dirp);
267
268	return (dirp);
269
270fail:
271	saved_errno = errno;
272	free(dirp);
273	(void)_close(fd);
274	errno = saved_errno;
275	return (NULL);
276}
277