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comparison src/realpath.c @ 428:3ecd8885ac67 r21-2-22

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Import from CVS: tag r21-2-22
author cvs
date Mon, 13 Aug 2007 11:28:15 +0200
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427:0a0253eac470 428:3ecd8885ac67
1 /*
2 * realpath.c -- canonicalize pathname by removing symlinks
3 * Copyright (C) 1993 Rick Sladkey <jrs@world.std.com>
4 *
5
6 This file is part of XEmacs.
7
8 XEmacs is free software; you can redistribute it and/or modify it
9 under the terms of the GNU General Public License as published by the
10 Free Software Foundation; either version 2, or (at your option) any
11 later version.
12
13 XEmacs is distributed in the hope that it will be useful, but WITHOUT
14 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
15 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
16 for more details.
17
18 You should have received a copy of the GNU General Public License
19 along with XEmacs; see the file COPYING. If not, write to
20 the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
21 Boston, MA 02111-1307, USA. */
22
23 /* Synched up with: Not in FSF. */
24
25 #include <config.h>
26
27 #include <sys/types.h>
28 #include <stdio.h>
29 #include <string.h>
30 #include <errno.h>
31 #ifdef HAVE_UNISTD_H
32 #include <unistd.h>
33 #endif
34 #ifdef _POSIX_VERSION
35 #include <limits.h> /* for PATH_MAX */
36 #else
37 #include <sys/param.h> /* for MAXPATHLEN */
38 #endif
39
40 #ifdef WINDOWSNT
41 #include <direct.h>
42 #endif
43
44 #include <sys/stat.h> /* for S_IFLNK */
45
46 #ifndef PATH_MAX
47 #ifdef _POSIX_VERSION
48 #define PATH_MAX _POSIX_PATH_MAX
49 #else
50 #ifdef MAXPATHLEN
51 #define PATH_MAX MAXPATHLEN
52 #else
53 #define PATH_MAX 1024
54 #endif
55 #endif
56 #endif
57
58 #define MAX_READLINKS 32
59
60 char *
61 xrealpath (const char *path, char resolved_path [])
62 {
63 char copy_path[PATH_MAX];
64 char *new_path = resolved_path;
65 char *max_path;
66 #ifdef S_IFLNK
67 int readlinks = 0;
68 char link_path[PATH_MAX];
69 int n;
70 #endif
71
72 /* Make a copy of the source path since we may need to modify it. */
73 strcpy(copy_path, path);
74 path = copy_path;
75 max_path = copy_path + PATH_MAX - 2;
76 #ifdef WINDOWSNT
77 /*
78 ** In NT we have two different cases: (1) the path name begins
79 ** with a drive letter, e.g., "C:"; and (2) the path name begins
80 ** with just a slash, which roots to the current drive. In the
81 ** first case we are going to leave things alone, in the second
82 ** case we will prepend the drive letter to the given path.
83 ** Note: So far in testing, I'm only seeing case #1, even though
84 ** I've tried to get the other cases to happen.
85 ** August Hill, 31 Aug 1997.
86 **
87 ** Check for a driver letter...C:/...
88 */
89 if (*(path + 1) == ':')
90 {
91 strncpy(new_path, path, 3);
92 new_path += 3;
93 path += 3;
94 }
95
96 /*
97 ** No drive letter, but a beginning slash? Prepend the drive
98 ** letter...
99 */
100 else if (*path == '/')
101 {
102 getcwd(new_path, PATH_MAX - 1);
103 new_path += 3;
104 path++;
105 }
106
107 /*
108 ** Just a path name, prepend the current directory
109 */
110 else
111 {
112 getcwd(new_path, PATH_MAX - 1);
113 new_path += strlen(new_path);
114 if (new_path[-1] != '/')
115 *new_path++ = '/';
116 }
117
118 #else
119 /* If it's a relative pathname use getwd for starters. */
120 if (*path != '/')
121 {
122 #ifdef HAVE_GETCWD
123 getcwd(new_path, PATH_MAX - 1);
124 #else
125 getwd(new_path);
126 #endif
127 new_path += strlen(new_path);
128 if (new_path[-1] != '/')
129 *new_path++ = '/';
130 }
131 else
132 {
133 *new_path++ = '/';
134 path++;
135 }
136 #endif
137 /* Expand each slash-separated pathname component. */
138 while (*path != '\0')
139 {
140 /* Ignore stray "/". */
141 if (*path == '/')
142 {
143 path++;
144 continue;
145 }
146
147 if (*path == '.')
148 {
149 /* Ignore ".". */
150 if (path[1] == '\0' || path[1] == '/')
151 {
152 path++;
153 continue;
154 }
155
156 if (path[1] == '.')
157 {
158 if (path[2] == '\0' || path[2] == '/')
159 {
160 path += 2;
161
162 /* Ignore ".." at root. */
163 if (new_path == resolved_path + 1)
164 continue;
165
166 /* Handle ".." by backing up. */
167 while ((--new_path)[-1] != '/')
168 ;
169 continue;
170 }
171 }
172 }
173
174 /* Safely copy the next pathname component. */
175 while (*path != '\0' && *path != '/')
176 {
177 if (path > max_path)
178 {
179 errno = ENAMETOOLONG;
180 return NULL;
181 }
182 *new_path++ = *path++;
183 }
184
185 #ifdef S_IFLNK
186 /* See if latest pathname component is a symlink. */
187 *new_path = '\0';
188 n = readlink(resolved_path, link_path, PATH_MAX - 1);
189
190 if (n < 0)
191 {
192 /* EINVAL means the file exists but isn't a symlink. */
193 if (errno != EINVAL)
194 return NULL;
195 }
196 else
197 {
198 /* Protect against infinite loops. */
199 if (readlinks++ > MAX_READLINKS)
200 {
201 errno = ELOOP;
202 return NULL;
203 }
204
205 /* Note: readlink doesn't add the null byte. */
206 link_path[n] = '\0';
207
208 if (*link_path == '/')
209 /* Start over for an absolute symlink. */
210 new_path = resolved_path;
211 else
212 /* Otherwise back up over this component. */
213 while (*(--new_path) != '/')
214 ;
215
216 /* Safe sex check. */
217 if (strlen(path) + n >= PATH_MAX)
218 {
219 errno = ENAMETOOLONG;
220 return NULL;
221 }
222
223 /* Insert symlink contents into path. */
224 strcat(link_path, path);
225 strcpy(copy_path, link_path);
226 path = copy_path;
227 }
228 #endif /* S_IFLNK */
229 *new_path++ = '/';
230 }
231
232 /* Delete trailing slash but don't whomp a lone slash. */
233 if (new_path != resolved_path + 1 && new_path[-1] == '/')
234 new_path--;
235
236 /* Make sure it's null terminated. */
237 *new_path = '\0';
238 return resolved_path;
239 }