1 /* Open a stream to a file.
2 Copyright (C) 2007-2022 Free Software Foundation, Inc.
3
4 This file is free software: you can redistribute it and/or modify
5 it under the terms of the GNU Lesser General Public License as
6 published by the Free Software Foundation; either version 2.1 of the
7 License, or (at your option) any later version.
8
9 This file is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 GNU Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public License
15 along with this program. If not, see <https://www.gnu.org/licenses/>. */
16
17 /* Written by Bruno Haible <bruno@clisp.org>, 2007. */
18
19 /* If the user's config.h happens to include <stdio.h>, let it include only
20 the system's <stdio.h> here, so that orig_fopen doesn't recurse to
21 rpl_fopen. */
22 #define _GL_ALREADY_INCLUDING_STDIO_H
23 #include <config.h>
24
25 /* Get the original definition of fopen. It might be defined as a macro. */
26 #include <stdio.h>
27 #undef _GL_ALREADY_INCLUDING_STDIO_H
28
29 static FILE *
30 orig_fopen (const char *filename, const char *mode)
31 {
32 return fopen (filename, mode);
33 }
34
35 /* Specification. */
36 /* Write "stdio.h" here, not <stdio.h>, otherwise OSF/1 5.1 DTK cc eliminates
37 this include because of the preliminary #include <stdio.h> above. */
38 #include "stdio.h"
39
40 #include <errno.h>
41 #include <fcntl.h>
42 #include <stdbool.h>
43 #include <string.h>
44 #include <unistd.h>
45 #include <sys/types.h>
46 #include <sys/stat.h>
47
48 FILE *
49 rpl_fopen (const char *filename, const char *mode)
50 {
51 int open_direction;
52 int open_flags;
53 #if GNULIB_FOPEN_GNU
54 bool open_flags_gnu;
55 # define BUF_SIZE 80
56 char fdopen_mode_buf[BUF_SIZE + 1];
57 #endif
58
59 #if defined _WIN32 && ! defined __CYGWIN__
60 if (strcmp (filename, "/dev/null") == 0)
61 filename = "NUL";
62 #endif
63
64 /* Parse the mode. */
65 open_direction = 0;
66 open_flags = 0;
67 #if GNULIB_FOPEN_GNU
68 open_flags_gnu = false;
69 #endif
70 {
71 const char *p = mode;
72 #if GNULIB_FOPEN_GNU
73 char *q = fdopen_mode_buf;
74 #endif
75
76 for (; *p != '\0'; p++)
77 {
78 switch (*p)
79 {
80 case 'r':
81 open_direction = O_RDONLY;
82 #if GNULIB_FOPEN_GNU
83 if (q < fdopen_mode_buf + BUF_SIZE)
84 *q++ = *p;
85 #endif
86 continue;
87 case 'w':
88 open_direction = O_WRONLY;
89 open_flags |= O_CREAT | O_TRUNC;
90 #if GNULIB_FOPEN_GNU
91 if (q < fdopen_mode_buf + BUF_SIZE)
92 *q++ = *p;
93 #endif
94 continue;
95 case 'a':
96 open_direction = O_WRONLY;
97 open_flags |= O_CREAT | O_APPEND;
98 #if GNULIB_FOPEN_GNU
99 if (q < fdopen_mode_buf + BUF_SIZE)
100 *q++ = *p;
101 #endif
102 continue;
103 case 'b':
104 /* While it is non-standard, O_BINARY is guaranteed by
105 gnulib <fcntl.h>. We can also assume that orig_fopen
106 supports the 'b' flag. */
107 open_flags |= O_BINARY;
108 #if GNULIB_FOPEN_GNU
109 if (q < fdopen_mode_buf + BUF_SIZE)
110 *q++ = *p;
111 #endif
112 continue;
113 case '+':
114 open_direction = O_RDWR;
115 #if GNULIB_FOPEN_GNU
116 if (q < fdopen_mode_buf + BUF_SIZE)
117 *q++ = *p;
118 #endif
119 continue;
120 #if GNULIB_FOPEN_GNU
121 case 'x':
122 open_flags |= O_EXCL;
123 open_flags_gnu = true;
124 continue;
125 case 'e':
126 open_flags |= O_CLOEXEC;
127 open_flags_gnu = true;
128 continue;
129 #endif
130 default:
131 break;
132 }
133 #if GNULIB_FOPEN_GNU
134 /* The rest of the mode string can be a platform-dependent extension.
135 Copy it unmodified. */
136 {
137 size_t len = strlen (p);
138 if (len > fdopen_mode_buf + BUF_SIZE - q)
139 len = fdopen_mode_buf + BUF_SIZE - q;
140 memcpy (q, p, len);
141 q += len;
142 }
143 #endif
144 break;
145 }
146 #if GNULIB_FOPEN_GNU
147 *q = '\0';
148 #endif
149 }
150
151 #if FOPEN_TRAILING_SLASH_BUG
152 /* Fail if the mode requires write access and the filename ends in a slash,
153 as POSIX says such a filename must name a directory
154 <https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_13>:
155 "A pathname that contains at least one non-<slash> character and that
156 ends with one or more trailing <slash> characters shall not be resolved
157 successfully unless the last pathname component before the trailing
158 <slash> characters names an existing directory"
159 If the named file already exists as a directory, then if a mode that
160 requires write access is specified, fopen() must fail because POSIX
161 <https://pubs.opengroup.org/onlinepubs/9699919799/functions/fopen.html>
162 says that it fails with errno = EISDIR in this case.
163 If the named file does not exist or does not name a directory, then
164 fopen() must fail since the file does not contain a '.' directory. */
165 {
166 size_t len = strlen (filename);
167 if (len > 0 && filename[len - 1] == '/')
168 {
169 int fd;
170 struct stat statbuf;
171 FILE *fp;
172
173 if (open_direction != O_RDONLY)
174 {
175 errno = EISDIR;
176 return NULL;
177 }
178
179 fd = open (filename, open_direction | open_flags,
180 S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH);
181 if (fd < 0)
182 return NULL;
183
184 if (fstat (fd, &statbuf) >= 0 && !S_ISDIR (statbuf.st_mode))
185 {
186 close (fd);
187 errno = ENOTDIR;
188 return NULL;
189 }
190
191 # if GNULIB_FOPEN_GNU
192 fp = fdopen (fd, fdopen_mode_buf);
193 # else
194 fp = fdopen (fd, mode);
195 # endif
196 if (fp == NULL)
197 {
198 int saved_errno = errno;
199 close (fd);
200 errno = saved_errno;
201 }
202 return fp;
203 }
204 }
205 #endif
206
207 #if GNULIB_FOPEN_GNU
208 if (open_flags_gnu)
209 {
210 int fd;
211 FILE *fp;
212
213 fd = open (filename, open_direction | open_flags,
214 S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH);
215 if (fd < 0)
216 return NULL;
217
218 fp = fdopen (fd, fdopen_mode_buf);
219 if (fp == NULL)
220 {
221 int saved_errno = errno;
222 close (fd);
223 errno = saved_errno;
224 }
225 return fp;
226 }
227 #endif
228
229 return orig_fopen (filename, mode);
230 }