getcwd.c revision 124208 
1/*
2 * Copyright (c) 1989, 1991, 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. Neither the name of the University nor the names of its contributors
14 *    may be used to endorse or promote products derived from this software
15 *    without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 */
29
30#include "includes.h"
31
32#if !defined(HAVE_GETCWD)
33
34#if defined(LIBC_SCCS) && !defined(lint)
35static char rcsid[] = "$OpenBSD: getcwd.c,v 1.9 2003/06/11 21:03:10 deraadt Exp $";
36#endif /* LIBC_SCCS and not lint */
37
38#include <sys/param.h>
39#include <sys/stat.h>
40#include <errno.h>
41#include <dirent.h>
42#include <sys/dir.h>
43#include <stdio.h>
44#include <stdlib.h>
45#include <string.h>
46#include "includes.h"
47
48#define	ISDOT(dp) \
49	(dp->d_name[0] == '.' && (dp->d_name[1] == '\0' || \
50	    (dp->d_name[1] == '.' && dp->d_name[2] == '\0')))
51
52char *
53getcwd(char *pt, size_t size)
54{
55	register struct dirent *dp;
56	register DIR *dir = NULL;
57	register dev_t dev;
58	register ino_t ino;
59	register int first;
60	register char *bpt, *bup;
61	struct stat s;
62	dev_t root_dev;
63	ino_t root_ino;
64	size_t ptsize, upsize;
65	int save_errno;
66	char *ept, *eup, *up;
67
68	/*
69	 * If no buffer specified by the user, allocate one as necessary.
70	 * If a buffer is specified, the size has to be non-zero.  The path
71	 * is built from the end of the buffer backwards.
72	 */
73	if (pt) {
74		ptsize = 0;
75		if (!size) {
76			errno = EINVAL;
77			return (NULL);
78		}
79		ept = pt + size;
80	} else {
81		if ((pt = malloc(ptsize = 1024 - 4)) == NULL)
82			return (NULL);
83		ept = pt + ptsize;
84	}
85	bpt = ept - 1;
86	*bpt = '\0';
87
88	/*
89	 * Allocate bytes (1024 - malloc space) for the string of "../"'s.
90	 * Should always be enough (it's 340 levels).  If it's not, allocate
91	 * as necessary.  Special * case the first stat, it's ".", not "..".
92	 */
93	if ((up = malloc(upsize = 1024 - 4)) == NULL)
94		goto err;
95	eup = up + MAXPATHLEN;
96	bup = up;
97	up[0] = '.';
98	up[1] = '\0';
99
100	/* Save root values, so know when to stop. */
101	if (stat("/", &s))
102		goto err;
103	root_dev = s.st_dev;
104	root_ino = s.st_ino;
105
106	errno = 0;			/* XXX readdir has no error return. */
107
108	for (first = 1;; first = 0) {
109		/* Stat the current level. */
110		if (lstat(up, &s))
111			goto err;
112
113		/* Save current node values. */
114		ino = s.st_ino;
115		dev = s.st_dev;
116
117		/* Check for reaching root. */
118		if (root_dev == dev && root_ino == ino) {
119			*--bpt = '/';
120			/*
121			 * It's unclear that it's a requirement to copy the
122			 * path to the beginning of the buffer, but it's always
123			 * been that way and stuff would probably break.
124			 */
125			memmove(pt, bpt, ept - bpt);
126			free(up);
127			return (pt);
128		}
129
130		/*
131		 * Build pointer to the parent directory, allocating memory
132		 * as necessary.  Max length is 3 for "../", the largest
133		 * possible component name, plus a trailing NUL.
134		 */
135		if (bup + 3  + MAXNAMLEN + 1 >= eup) {
136			char *nup;
137
138			if ((nup = realloc(up, upsize *= 2)) == NULL)
139				goto err;
140			up = nup;
141			bup = up;
142			eup = up + upsize;
143		}
144		*bup++ = '.';
145		*bup++ = '.';
146		*bup = '\0';
147
148		/* Open and stat parent directory.
149		 * RACE?? - replaced fstat(dirfd(dir), &s) w/ lstat(up,&s)
150                 */
151		if (!(dir = opendir(up)) || lstat(up,&s))
152			goto err;
153
154		/* Add trailing slash for next directory. */
155		*bup++ = '/';
156
157		/*
158		 * If it's a mount point, have to stat each element because
159		 * the inode number in the directory is for the entry in the
160		 * parent directory, not the inode number of the mounted file.
161		 */
162		save_errno = 0;
163		if (s.st_dev == dev) {
164			for (;;) {
165				if (!(dp = readdir(dir)))
166					goto notfound;
167				if (dp->d_fileno == ino)
168					break;
169			}
170		} else
171			for (;;) {
172				if (!(dp = readdir(dir)))
173					goto notfound;
174				if (ISDOT(dp))
175					continue;
176				memmove(bup, dp->d_name, dp->d_namlen + 1);
177
178				/* Save the first error for later. */
179				if (lstat(up, &s)) {
180					if (!save_errno)
181						save_errno = errno;
182					errno = 0;
183					continue;
184				}
185				if (s.st_dev == dev && s.st_ino == ino)
186					break;
187			}
188
189		/*
190		 * Check for length of the current name, preceding slash,
191		 * leading slash.
192		 */
193		if (bpt - pt < dp->d_namlen + (first ? 1 : 2)) {
194			size_t len, off;
195			char *npt;
196
197			if (!ptsize) {
198				errno = ERANGE;
199				goto err;
200			}
201			off = bpt - pt;
202			len = ept - bpt;
203			if ((npt = realloc(pt, ptsize *= 2)) == NULL)
204				goto err;
205			pt = npt;
206			bpt = pt + off;
207			ept = pt + ptsize;
208			memmove(ept - len, bpt, len);
209			bpt = ept - len;
210		}
211		if (!first)
212			*--bpt = '/';
213		bpt -= dp->d_namlen;
214		memmove(bpt, dp->d_name, dp->d_namlen);
215		(void)closedir(dir);
216
217		/* Truncate any file name. */
218		*bup = '\0';
219	}
220
221notfound:
222	/*
223	 * If readdir set errno, use it, not any saved error; otherwise,
224	 * didn't find the current directory in its parent directory, set
225	 * errno to ENOENT.
226	 */
227	if (!errno)
228		errno = save_errno ? save_errno : ENOENT;
229	/* FALLTHROUGH */
230err:
231	if (ptsize)
232		free(pt);
233	if (up)
234		free(up);
235	if (dir)
236		(void)closedir(dir);
237	return (NULL);
238}
239
240#endif /* !defined(HAVE_GETCWD) */
241