getcwd.c revision 323134 
1/*	$OpenBSD: getcwd.c,v 1.14 2005/08/08 08:05:34 espie Exp */
2/*
3 * Copyright (c) 1989, 1991, 1993
4 *	The Regents of the University of California.  All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 *    notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 * 3. Neither the name of the University nor the names of its contributors
15 *    may be used to endorse or promote products derived from this software
16 *    without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 * SUCH DAMAGE.
29 */
30
31/* OPENBSD ORIGINAL: lib/libc/gen/getcwd.c */
32
33#include "includes.h"
34
35#if !defined(HAVE_GETCWD)
36
37#include <sys/param.h>
38#include <sys/stat.h>
39#include <errno.h>
40#include <dirent.h>
41#include <sys/dir.h>
42#include <stdio.h>
43#include <stdlib.h>
44#include <string.h>
45#include "includes.h"
46
47#define	ISDOT(dp) \
48	(dp->d_name[0] == '.' && (dp->d_name[1] == '\0' || \
49	    (dp->d_name[1] == '.' && dp->d_name[2] == '\0')))
50
51char *
52getcwd(char *pt, size_t size)
53{
54	struct dirent *dp;
55	DIR *dir = NULL;
56	dev_t dev;
57	ino_t ino;
58	int first;
59	char *bpt, *bup;
60	struct stat s;
61	dev_t root_dev;
62	ino_t root_ino;
63	size_t ptsize, upsize;
64	int save_errno;
65	char *ept, *eup, *up;
66
67	/*
68	 * If no buffer specified by the user, allocate one as necessary.
69	 * If a buffer is specified, the size has to be non-zero.  The path
70	 * is built from the end of the buffer backwards.
71	 */
72	if (pt) {
73		ptsize = 0;
74		if (!size) {
75			errno = EINVAL;
76			return (NULL);
77		}
78		ept = pt + size;
79	} else {
80		if ((pt = malloc(ptsize = MAXPATHLEN)) == NULL)
81			return (NULL);
82		ept = pt + ptsize;
83	}
84	bpt = ept - 1;
85	*bpt = '\0';
86
87	/*
88	 * Allocate bytes for the string of "../"'s.
89	 * Should always be enough (it's 340 levels).  If it's not, allocate
90	 * as necessary.  Special * case the first stat, it's ".", not "..".
91	 */
92	if ((up = malloc(upsize = MAXPATHLEN)) == NULL)
93		goto err;
94	eup = up + upsize;
95	bup = up;
96	up[0] = '.';
97	up[1] = '\0';
98
99	/* Save root values, so know when to stop. */
100	if (stat("/", &s))
101		goto err;
102	root_dev = s.st_dev;
103	root_ino = s.st_ino;
104
105	errno = 0;			/* XXX readdir has no error return. */
106
107	for (first = 1;; first = 0) {
108		/* Stat the current level. */
109		if (lstat(up, &s))
110			goto err;
111
112		/* Save current node values. */
113		ino = s.st_ino;
114		dev = s.st_dev;
115
116		/* Check for reaching root. */
117		if (root_dev == dev && root_ino == ino) {
118			*--bpt = '/';
119			/*
120			 * It's unclear that it's a requirement to copy the
121			 * path to the beginning of the buffer, but it's always
122			 * been that way and stuff would probably break.
123			 */
124			memmove(pt, bpt, ept - bpt);
125			free(up);
126			return (pt);
127		}
128
129		/*
130		 * Build pointer to the parent directory, allocating memory
131		 * as necessary.  Max length is 3 for "../", the largest
132		 * possible component name, plus a trailing NUL.
133		 */
134		if (bup + 3  + MAXNAMLEN + 1 >= eup) {
135			char *nup;
136
137			if ((nup = realloc(up, upsize *= 2)) == NULL)
138				goto err;
139			bup = nup + (bup - up);
140			up = nup;
141			eup = up + upsize;
142		}
143		*bup++ = '.';
144		*bup++ = '.';
145		*bup = '\0';
146
147		/* Open and stat parent directory. */
148		if (!(dir = opendir(up)) || fstat(dirfd(dir), &s))
149			goto err;
150
151		/* Add trailing slash for next directory. */
152		*bup++ = '/';
153
154		/*
155		 * If it's a mount point, have to stat each element because
156		 * the inode number in the directory is for the entry in the
157		 * parent directory, not the inode number of the mounted file.
158		 */
159		save_errno = 0;
160		if (s.st_dev == dev) {
161			for (;;) {
162				if (!(dp = readdir(dir)))
163					goto notfound;
164				if (dp->d_fileno == ino)
165					break;
166			}
167		} else
168			for (;;) {
169				if (!(dp = readdir(dir)))
170					goto notfound;
171				if (ISDOT(dp))
172					continue;
173				memcpy(bup, dp->d_name, dp->d_namlen + 1);
174
175				/* Save the first error for later. */
176				if (lstat(up, &s)) {
177					if (!save_errno)
178						save_errno = errno;
179					errno = 0;
180					continue;
181				}
182				if (s.st_dev == dev && s.st_ino == ino)
183					break;
184			}
185
186		/*
187		 * Check for length of the current name, preceding slash,
188		 * leading slash.
189		 */
190		if (bpt - pt < dp->d_namlen + (first ? 1 : 2)) {
191			size_t len;
192			char *npt;
193
194			if (!ptsize) {
195				errno = ERANGE;
196				goto err;
197			}
198			len = ept - bpt;
199			if ((npt = realloc(pt, ptsize *= 2)) == NULL)
200				goto err;
201			bpt = npt + (bpt - pt);
202			pt = npt;
203			ept = pt + ptsize;
204			memmove(ept - len, bpt, len);
205			bpt = ept - len;
206		}
207		if (!first)
208			*--bpt = '/';
209		bpt -= dp->d_namlen;
210		memcpy(bpt, dp->d_name, dp->d_namlen);
211		(void)closedir(dir);
212
213		/* Truncate any file name. */
214		*bup = '\0';
215	}
216
217notfound:
218	/*
219	 * If readdir set errno, use it, not any saved error; otherwise,
220	 * didn't find the current directory in its parent directory, set
221	 * errno to ENOENT.
222	 */
223	if (!errno)
224		errno = save_errno ? save_errno : ENOENT;
225	/* FALLTHROUGH */
226err:
227	save_errno = errno;
228
229	if (ptsize)
230		free(pt);
231	free(up);
232	if (dir)
233		(void)closedir(dir);
234
235	errno = save_errno;
236
237	return (NULL);
238}
239
240#endif /* !defined(HAVE_GETCWD) */
241