getcwd.c revision 126274 
1/* OPENBSD ORIGINAL: lib/libc/gen/getcwd.c */
2
3/*
4 * Copyright (c) 1989, 1991, 1993
5 *	The Regents of the University of California.  All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in the
14 *    documentation and/or other materials provided with the distribution.
15 * 3. Neither the name of the University nor the names of its contributors
16 *    may be used to endorse or promote products derived from this software
17 *    without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 */
31
32#include "includes.h"
33
34#if !defined(HAVE_GETCWD)
35
36#if defined(LIBC_SCCS) && !defined(lint)
37static char rcsid[] = "$OpenBSD: getcwd.c,v 1.9 2003/06/11 21:03:10 deraadt Exp $";
38#endif /* LIBC_SCCS and not lint */
39
40#include <sys/param.h>
41#include <sys/stat.h>
42#include <errno.h>
43#include <dirent.h>
44#include <sys/dir.h>
45#include <stdio.h>
46#include <stdlib.h>
47#include <string.h>
48#include "includes.h"
49
50#define	ISDOT(dp) \
51	(dp->d_name[0] == '.' && (dp->d_name[1] == '\0' || \
52	    (dp->d_name[1] == '.' && dp->d_name[2] == '\0')))
53
54char *
55getcwd(char *pt, size_t size)
56{
57	register struct dirent *dp;
58	register DIR *dir = NULL;
59	register dev_t dev;
60	register ino_t ino;
61	register int first;
62	register char *bpt, *bup;
63	struct stat s;
64	dev_t root_dev;
65	ino_t root_ino;
66	size_t ptsize, upsize;
67	int save_errno;
68	char *ept, *eup, *up;
69
70	/*
71	 * If no buffer specified by the user, allocate one as necessary.
72	 * If a buffer is specified, the size has to be non-zero.  The path
73	 * is built from the end of the buffer backwards.
74	 */
75	if (pt) {
76		ptsize = 0;
77		if (!size) {
78			errno = EINVAL;
79			return (NULL);
80		}
81		ept = pt + size;
82	} else {
83		if ((pt = malloc(ptsize = 1024 - 4)) == NULL)
84			return (NULL);
85		ept = pt + ptsize;
86	}
87	bpt = ept - 1;
88	*bpt = '\0';
89
90	/*
91	 * Allocate bytes (1024 - malloc space) for the string of "../"'s.
92	 * Should always be enough (it's 340 levels).  If it's not, allocate
93	 * as necessary.  Special * case the first stat, it's ".", not "..".
94	 */
95	if ((up = malloc(upsize = 1024 - 4)) == NULL)
96		goto err;
97	eup = up + MAXPATHLEN;
98	bup = up;
99	up[0] = '.';
100	up[1] = '\0';
101
102	/* Save root values, so know when to stop. */
103	if (stat("/", &s))
104		goto err;
105	root_dev = s.st_dev;
106	root_ino = s.st_ino;
107
108	errno = 0;			/* XXX readdir has no error return. */
109
110	for (first = 1;; first = 0) {
111		/* Stat the current level. */
112		if (lstat(up, &s))
113			goto err;
114
115		/* Save current node values. */
116		ino = s.st_ino;
117		dev = s.st_dev;
118
119		/* Check for reaching root. */
120		if (root_dev == dev && root_ino == ino) {
121			*--bpt = '/';
122			/*
123			 * It's unclear that it's a requirement to copy the
124			 * path to the beginning of the buffer, but it's always
125			 * been that way and stuff would probably break.
126			 */
127			memmove(pt, bpt, ept - bpt);
128			free(up);
129			return (pt);
130		}
131
132		/*
133		 * Build pointer to the parent directory, allocating memory
134		 * as necessary.  Max length is 3 for "../", the largest
135		 * possible component name, plus a trailing NUL.
136		 */
137		if (bup + 3  + MAXNAMLEN + 1 >= eup) {
138			char *nup;
139
140			if ((nup = realloc(up, upsize *= 2)) == NULL)
141				goto err;
142			up = nup;
143			bup = up;
144			eup = up + upsize;
145		}
146		*bup++ = '.';
147		*bup++ = '.';
148		*bup = '\0';
149
150		/* Open and stat parent directory.
151		 * RACE?? - replaced fstat(dirfd(dir), &s) w/ lstat(up,&s)
152                 */
153		if (!(dir = opendir(up)) || lstat(up,&s))
154			goto err;
155
156		/* Add trailing slash for next directory. */
157		*bup++ = '/';
158
159		/*
160		 * If it's a mount point, have to stat each element because
161		 * the inode number in the directory is for the entry in the
162		 * parent directory, not the inode number of the mounted file.
163		 */
164		save_errno = 0;
165		if (s.st_dev == dev) {
166			for (;;) {
167				if (!(dp = readdir(dir)))
168					goto notfound;
169				if (dp->d_fileno == ino)
170					break;
171			}
172		} else
173			for (;;) {
174				if (!(dp = readdir(dir)))
175					goto notfound;
176				if (ISDOT(dp))
177					continue;
178				memmove(bup, dp->d_name, dp->d_namlen + 1);
179
180				/* Save the first error for later. */
181				if (lstat(up, &s)) {
182					if (!save_errno)
183						save_errno = errno;
184					errno = 0;
185					continue;
186				}
187				if (s.st_dev == dev && s.st_ino == ino)
188					break;
189			}
190
191		/*
192		 * Check for length of the current name, preceding slash,
193		 * leading slash.
194		 */
195		if (bpt - pt < dp->d_namlen + (first ? 1 : 2)) {
196			size_t len, off;
197			char *npt;
198
199			if (!ptsize) {
200				errno = ERANGE;
201				goto err;
202			}
203			off = bpt - pt;
204			len = ept - bpt;
205			if ((npt = realloc(pt, ptsize *= 2)) == NULL)
206				goto err;
207			pt = npt;
208			bpt = pt + off;
209			ept = pt + ptsize;
210			memmove(ept - len, bpt, len);
211			bpt = ept - len;
212		}
213		if (!first)
214			*--bpt = '/';
215		bpt -= dp->d_namlen;
216		memmove(bpt, dp->d_name, dp->d_namlen);
217		(void)closedir(dir);
218
219		/* Truncate any file name. */
220		*bup = '\0';
221	}
222
223notfound:
224	/*
225	 * If readdir set errno, use it, not any saved error; otherwise,
226	 * didn't find the current directory in its parent directory, set
227	 * errno to ENOENT.
228	 */
229	if (!errno)
230		errno = save_errno ? save_errno : ENOENT;
231	/* FALLTHROUGH */
232err:
233	if (ptsize)
234		free(pt);
235	if (up)
236		free(up);
237	if (dir)
238		(void)closedir(dir);
239	return (NULL);
240}
241
242#endif /* !defined(HAVE_GETCWD) */
243