getcwd.c revision 29476 
1/*
2 * Copyright (c) 1989, 1991, 1993, 1995
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[] = "@(#)getcwd.c	8.5 (Berkeley) 2/7/95";
36#endif /* LIBC_SCCS and not lint */
37
38#include <sys/param.h>
39#include <sys/stat.h>
40
41#include <dirent.h>
42#include <errno.h>
43#include <fcntl.h>
44#include <stdio.h>
45#include <stdlib.h>
46#include <string.h>
47#include <unistd.h>
48
49#define	ISDOT(dp) \
50	(dp->d_name[0] == '.' && (dp->d_name[1] == '\0' || \
51	    (dp->d_name[1] == '.' && dp->d_name[2] == '\0')))
52
53char *
54getcwd(pt, size)
55	char *pt;
56	size_t size;
57{
58	register struct dirent *dp;
59	register DIR *dir = NULL;
60	register dev_t dev;
61	register ino_t ino;
62	register int first;
63	register char *bpt, *bup;
64	struct stat s;
65	dev_t root_dev;
66	ino_t root_ino;
67	size_t ptsize, upsize;
68	int save_errno;
69	char *ept, *eup, *up, c;
70
71	/*
72	 * If no buffer specified by the user, allocate one as necessary.
73	 * If a buffer is specified, the size has to be non-zero.  The path
74	 * is built from the end of the buffer backwards.
75	 */
76	if (pt) {
77		ptsize = 0;
78		if (!size) {
79			errno = EINVAL;
80			return (NULL);
81		}
82		if (size == 1) {
83			errno = ERANGE;
84			return (NULL);
85		}
86		ept = pt + size;
87	} else {
88		if ((pt = malloc(ptsize = 1024 - 4)) == NULL)
89			return (NULL);
90		ept = pt + ptsize;
91	}
92	if (!__getcwd(pt, ept - pt)) {
93		if (*pt != '/') {
94			bpt = pt;
95			ept = pt + strlen(pt) - 1;
96			while (bpt < ept) {
97				c = *bpt;
98				*bpt++ = *ept;
99				*ept-- = c;
100			}
101		}
102		return (pt);
103	}
104	bpt = ept - 1;
105	*bpt = '\0';
106
107	/*
108	 * Allocate bytes (1024 - malloc space) for the string of "../"'s.
109	 * Should always be enough (it's 340 levels).  If it's not, allocate
110	 * as necessary.  Special case the first stat, it's ".", not "..".
111	 */
112	if ((up = malloc(upsize = 1024 - 4)) == NULL)
113		goto err;
114	eup = up + MAXPATHLEN;
115	bup = up;
116	up[0] = '.';
117	up[1] = '\0';
118
119	/* Save root values, so know when to stop. */
120	if (stat("/", &s))
121		goto err;
122	root_dev = s.st_dev;
123	root_ino = s.st_ino;
124
125	errno = 0;			/* XXX readdir has no error return. */
126
127	for (first = 1;; first = 0) {
128		/* Stat the current level. */
129		if (lstat(up, &s))
130			goto err;
131
132		/* Save current node values. */
133		ino = s.st_ino;
134		dev = s.st_dev;
135
136		/* Check for reaching root. */
137		if (root_dev == dev && root_ino == ino) {
138			*--bpt = '/';
139			/*
140			 * It's unclear that it's a requirement to copy the
141			 * path to the beginning of the buffer, but it's always
142			 * been that way and stuff would probably break.
143			 */
144			bcopy(bpt, pt, ept - bpt);
145			free(up);
146			return (pt);
147		}
148
149		/*
150		 * Build pointer to the parent directory, allocating memory
151		 * as necessary.  Max length is 3 for "../", the largest
152		 * possible component name, plus a trailing NULL.
153		 */
154		if (bup + 3  + MAXNAMLEN + 1 >= eup) {
155			if ((up = realloc(up, upsize *= 2)) == NULL)
156				goto err;
157			bup = up;
158			eup = up + upsize;
159		}
160		*bup++ = '.';
161		*bup++ = '.';
162		*bup = '\0';
163
164		/* Open and stat parent directory. */
165		if (!(dir = opendir(up)) || fstat(dirfd(dir), &s))
166			goto err;
167
168		/* Add trailing slash for next directory. */
169		*bup++ = '/';
170		*bup = '\0';
171
172		/*
173		 * If it's a mount point, have to stat each element because
174		 * the inode number in the directory is for the entry in the
175		 * parent directory, not the inode number of the mounted file.
176		 */
177		save_errno = 0;
178		if (s.st_dev == dev) {
179			for (;;) {
180				if (!(dp = readdir(dir)))
181					goto notfound;
182				if (dp->d_fileno == ino)
183					break;
184			}
185		} else
186			for (;;) {
187				if (!(dp = readdir(dir)))
188					goto notfound;
189				if (ISDOT(dp))
190					continue;
191				bcopy(dp->d_name, bup, dp->d_namlen + 1);
192
193				/* Save the first error for later. */
194				if (lstat(up, &s)) {
195					if (!save_errno)
196						save_errno = errno;
197					errno = 0;
198					continue;
199				}
200				if (s.st_dev == dev && s.st_ino == ino)
201					break;
202			}
203
204		/*
205		 * Check for length of the current name, preceding slash,
206		 * leading slash.
207		 */
208		if (bpt - pt < dp->d_namlen + (first ? 1 : 2)) {
209			size_t len, off;
210
211			if (!ptsize) {
212				errno = ERANGE;
213				goto err;
214			}
215			off = bpt - pt;
216			len = ept - bpt;
217			if ((pt = realloc(pt, ptsize *= 2)) == NULL)
218				goto err;
219			bpt = pt + off;
220			ept = pt + ptsize;
221			bcopy(bpt, ept - len, len);
222			bpt = ept - len;
223		}
224		if (!first)
225			*--bpt = '/';
226		bpt -= dp->d_namlen;
227		bcopy(dp->d_name, bpt, dp->d_namlen);
228		(void) closedir(dir);
229		dir = NULL;
230
231		/* Truncate any file name. */
232		*bup = '\0';
233	}
234
235notfound:
236	/*
237	 * If readdir set errno, use it, not any saved error; otherwise,
238	 * didn't find the current directory in its parent directory, set
239	 * errno to ENOENT.
240	 */
241	if (!errno)
242		errno = save_errno ? save_errno : ENOENT;
243	/* FALLTHROUGH */
244err:
245	if (ptsize)
246		free(pt);
247	if (dir)
248		(void) closedir(dir);
249	free(up);
250	return (NULL);
251}
252