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comparison src/realpath.c @ 0:376386a54a3c r19-14

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Import from CVS: tag r19-14
author cvs
date Mon, 13 Aug 2007 08:45:50 +0200
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-1:000000000000 0:376386a54a3c
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 #ifdef HAVE_CONFIG_H
26 #include <config.h>
27 #endif
28
29 #include <sys/types.h>
30 #if defined(HAVE_UNISTD_H) || defined(STDC_HEADERS)
31 #include <unistd.h>
32 #endif
33 #include <stdio.h>
34 #include <string.h>
35 #ifdef _POSIX_VERSION
36 #include <limits.h> /* for PATH_MAX */
37 #else
38 #include <sys/param.h> /* for MAXPATHLEN */
39 #endif
40 #include <errno.h>
41 #ifndef STDC_HEADERS
42 extern int errno;
43 #endif
44
45 #include <sys/stat.h> /* for S_IFLNK */
46
47 #ifndef PATH_MAX
48 #ifdef _POSIX_VERSION
49 #define PATH_MAX _POSIX_PATH_MAX
50 #else
51 #ifdef MAXPATHLEN
52 #define PATH_MAX MAXPATHLEN
53 #else
54 #define PATH_MAX 1024
55 #endif
56 #endif
57 #endif
58
59 #define MAX_READLINKS 32
60
61 #ifdef __STDC__
62 char *realpath(const char *path, char resolved_path [])
63 #else
64 char *realpath(path, resolved_path)
65 const char *path;
66 char resolved_path [];
67 #endif
68 {
69 char copy_path[PATH_MAX];
70 char link_path[PATH_MAX];
71 char *new_path = resolved_path;
72 char *max_path;
73 int readlinks = 0;
74 int n;
75
76 /* Make a copy of the source path since we may need to modify it. */
77 strcpy(copy_path, path);
78 path = copy_path;
79 max_path = copy_path + PATH_MAX - 2;
80 /* If it's a relative pathname use getwd for starters. */
81 if (*path != '/')
82 {
83 #ifdef HAVE_GETCWD
84 getcwd(new_path, PATH_MAX - 1);
85 #else
86 getwd(new_path);
87 #endif
88 new_path += strlen(new_path);
89 if (new_path[-1] != '/')
90 *new_path++ = '/';
91 }
92 else
93 {
94 *new_path++ = '/';
95 path++;
96 }
97
98 /* Expand each slash-separated pathname component. */
99 while (*path != '\0')
100 {
101 /* Ignore stray "/". */
102 if (*path == '/')
103 {
104 path++;
105 continue;
106 }
107
108 if (*path == '.')
109 {
110 /* Ignore ".". */
111 if (path[1] == '\0' || path[1] == '/')
112 {
113 path++;
114 continue;
115 }
116
117 if (path[1] == '.')
118 {
119 if (path[2] == '\0' || path[2] == '/')
120 {
121 path += 2;
122
123 /* Ignore ".." at root. */
124 if (new_path == resolved_path + 1)
125 continue;
126
127 /* Handle ".." by backing up. */
128 while ((--new_path)[-1] != '/')
129 ;
130 continue;
131 }
132 }
133 }
134
135 /* Safely copy the next pathname component. */
136 while (*path != '\0' && *path != '/')
137 {
138 if (path > max_path)
139 {
140 errno = ENAMETOOLONG;
141 return NULL;
142 }
143 *new_path++ = *path++;
144 }
145
146 #ifdef S_IFLNK
147 /* See if latest pathname component is a symlink. */
148 *new_path = '\0';
149 n = readlink(resolved_path, link_path, PATH_MAX - 1);
150
151 if (n < 0)
152 {
153 /* EINVAL means the file exists but isn't a symlink. */
154 if (errno != EINVAL)
155 return NULL;
156 }
157 else
158 {
159 /* Protect against infinite loops. */
160 if (readlinks++ > MAX_READLINKS)
161 {
162 errno = ELOOP;
163 return NULL;
164 }
165
166 /* Note: readlink doesn't add the null byte. */
167 link_path[n] = '\0';
168
169 if (*link_path == '/')
170 /* Start over for an absolute symlink. */
171 new_path = resolved_path;
172 else
173 /* Otherwise back up over this component. */
174 while (*(--new_path) != '/')
175 ;
176
177 /* Safe sex check. */
178 if (strlen(path) + n >= PATH_MAX)
179 {
180 errno = ENAMETOOLONG;
181 return NULL;
182 }
183
184 /* Insert symlink contents into path. */
185 strcat(link_path, path);
186 strcpy(copy_path, link_path);
187 path = copy_path;
188 }
189 #endif /* S_IFLNK */
190 *new_path++ = '/';
191 }
192
193 /* Delete trailing slash but don't whomp a lone slash. */
194 if (new_path != resolved_path + 1 && new_path[-1] == '/')
195 new_path--;
196
197 /* Make sure it's null terminated. */
198 *new_path = '\0';
199 return resolved_path;
200 }