opendir.c revision 23668 
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
34#if defined(LIBC_SCCS) && !defined(lint)
35static char sccsid[] = "@(#)opendir.c	8.8 (Berkeley) 5/1/95";
36#endif /* LIBC_SCCS and not lint */
37
38#include <sys/param.h>
39#include <sys/stat.h>
40#include <sys/mount.h>
41
42#include <dirent.h>
43#include <errno.h>
44#include <fcntl.h>
45#include <stdlib.h>
46#include <unistd.h>
47
48/*
49 * Open a directory.
50 */
51DIR *
52opendir(name)
53	const char *name;
54{
55	return (__opendir2(name, DTF_HIDEW|DTF_NODUP));
56}
57
58DIR *
59__opendir2(name, flags)
60	const char *name;
61	int flags;
62{
63	DIR *dirp;
64	int fd;
65	int incr;
66	int unionstack;
67	struct stat statb;
68
69	/*
70	 * stat() before open() because opening of special files may be
71	 * harmful.  fstat() after open because the file may have changed.
72	 */
73	if (stat(name, &statb) != 0)
74		return NULL;
75	if (!S_ISDIR(statb.st_mode)) {
76		errno = ENOTDIR;
77		return NULL;
78	}
79	if ((fd = open(name, O_RDONLY | O_NONBLOCK)) == -1)
80		return (NULL);
81	if (fstat(fd, &statb) || !S_ISDIR(statb.st_mode)) {
82		errno = ENOTDIR;
83		close(fd);
84		return (NULL);
85	}
86	if (fcntl(fd, F_SETFD, FD_CLOEXEC) == -1 ||
87	    (dirp = (DIR *)malloc(sizeof(DIR))) == NULL) {
88		close(fd);
89		return (NULL);
90	}
91
92	/*
93	 * Use the system page size if that is a multiple of DIRBLKSIZ
94	 * this could speed things up in some cases.
95	 * Hopefully this can be a big win someday by allowing page
96	 * trades to user space to be done by getdirentries().
97	 */
98	incr = getpagesize();
99	if ((incr % DIRBLKSIZ) != 0)
100		incr = DIRBLKSIZ;
101
102	/*
103	 * Determine whether this directory is the top of a union stack.
104	 */
105	if (flags & DTF_NODUP) {
106		struct statfs sfb;
107
108		if (fstatfs(fd, &sfb) < 0) {
109			free(dirp);
110			close(fd);
111			return (NULL);
112		}
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 = realloc(buf, len);
143				if (buf == NULL) {
144					free(dirp);
145					close(fd);
146					return (NULL);
147				}
148				ddptr = buf + (len - space);
149			}
150
151			n = getdirentries(fd, ddptr, space, &dirp->dd_seek);
152			if (n > 0) {
153				ddptr += n;
154				space -= n;
155			}
156		} while (n > 0);
157
158		ddeptr = ddptr;
159		flags |= __DTF_READALL;
160
161		/*
162		 * Re-open the directory.
163		 * This has the effect of rewinding back to the
164		 * top of the union stack and is needed by
165		 * programs which plan to fchdir to a descriptor
166		 * which has also been read -- see fts.c.
167		 */
168		if (flags & DTF_REWIND) {
169			(void) close(fd);
170			if ((fd = open(name, O_RDONLY)) == -1) {
171				free(buf);
172				free(dirp);
173				return (NULL);
174			}
175		}
176
177		/*
178		 * There is now a buffer full of (possibly) duplicate
179		 * names.
180		 */
181		dirp->dd_buf = buf;
182
183		/*
184		 * Go round this loop twice...
185		 *
186		 * Scan through the buffer, counting entries.
187		 * On the second pass, save pointers to each one.
188		 * Then sort the pointers and remove duplicate names.
189		 */
190		for (dpv = 0;;) {
191			n = 0;
192			ddptr = buf;
193			while (ddptr < ddeptr) {
194				struct dirent *dp;
195
196				dp = (struct dirent *) ddptr;
197				if ((int)dp & 03)
198					break;
199				if ((dp->d_reclen <= 0) ||
200				    (dp->d_reclen > (ddeptr + 1 - ddptr)))
201					break;
202				ddptr += dp->d_reclen;
203				if (dp->d_fileno) {
204					if (dpv)
205						dpv[n] = dp;
206					n++;
207				}
208			}
209
210			if (dpv) {
211				struct dirent *xp;
212
213				/*
214				 * This sort must be stable.
215				 */
216				mergesort(dpv, n, sizeof(*dpv), alphasort);
217
218				dpv[n] = NULL;
219				xp = NULL;
220
221				/*
222				 * Scan through the buffer in sort order,
223				 * zapping the inode number of any
224				 * duplicate names.
225				 */
226				for (n = 0; dpv[n]; n++) {
227					struct dirent *dp = dpv[n];
228
229					if ((xp == NULL) ||
230					    strcmp(dp->d_name, xp->d_name)) {
231						xp = dp;
232					} else {
233						dp->d_fileno = 0;
234					}
235					if (dp->d_type == DT_WHT &&
236					    (flags & DTF_HIDEW))
237						dp->d_fileno = 0;
238				}
239
240				free(dpv);
241				break;
242			} else {
243				dpv = malloc((n+1) * sizeof(struct dirent *));
244				if (dpv == NULL)
245					break;
246			}
247		}
248
249		dirp->dd_len = len;
250		dirp->dd_size = ddptr - dirp->dd_buf;
251	} else {
252		dirp->dd_len = incr;
253		dirp->dd_buf = malloc(dirp->dd_len);
254		if (dirp->dd_buf == NULL) {
255			free(dirp);
256			close (fd);
257			return (NULL);
258		}
259		dirp->dd_seek = 0;
260		flags &= ~DTF_REWIND;
261	}
262
263	dirp->dd_loc = 0;
264	dirp->dd_fd = fd;
265	dirp->dd_flags = flags;
266
267	/*
268	 * Set up seek point for rewinddir.
269	 */
270	dirp->dd_rewind = telldir(dirp);
271
272	return (dirp);
273}
274