fd.c: Introduce para_chdir().
[paraslash.git] / fd.c
1 /*
2 * Copyright (C) 2006-2007 Andre Noll <maan@systemlinux.org>
3 *
4 * Licensed under the GPL v2. For licencing details see COPYING.
5 */
6
7 /** \file fd.c helper functions for file descriptor handling */
8
9 #include <sys/types.h>
10 #include <dirent.h>
11 #include <sys/mman.h>
12 #include <fcntl.h>
13 #include <sys/select.h>
14
15 #include "para.h"
16 #include "error.h"
17 /**
18 * check whether a file exists
19 *
20 * \param fn the file name
21 *
22 * \return Non-zero iff file exists.
23 */
24 int file_exists(const char *fn)
25 {
26 struct stat statbuf;
27
28 return !stat(fn, &statbuf);
29 }
30
31 /**
32 * paraslash's wrapper for select(2)
33 *
34 * It calls select(2) (with no exceptfds) and starts over if select() was
35 * interrupted by a signal.
36 *
37 * \param n the highest-numbered descriptor in any of the two sets, plus 1
38 * \param readfds fds that should be checked for readability
39 * \param writefds fds that should be checked for writablility
40 * \param timeout_tv upper bound on the amount of time elapsed before select()
41 * returns
42 *
43 * \return The return value of the underlying select() call.
44 *
45 * All arguments are passed verbatim to select(2).
46 * \sa select(2) select_tut(2)
47 */
48 int para_select(int n, fd_set *readfds, fd_set *writefds,
49 struct timeval *timeout_tv)
50 {
51 int ret, err;
52 do {
53 ret = select(n, readfds, writefds, NULL, timeout_tv);
54 err = errno;
55 } while (ret < 0 && err == EINTR);
56 if (ret < 0)
57 PARA_CRIT_LOG("select error: %s, max_fileno: %d\n",
58 strerror(err), n);
59 return ret;
60 }
61
62 /**
63 * set a file descriptor to non-blocking mode
64 *
65 * \param fd The file descriptor
66 *
67 * \returns 1 on success, -E_F_GETFL, -E_F_SETFL, on errors.
68 */
69 int mark_fd_nonblock(int fd)
70 {
71 int flags = fcntl(fd, F_GETFL);
72 if (flags < 0)
73 return -E_F_GETFL;
74 if (fcntl(fd, F_SETFL, ((long)flags) | O_NONBLOCK) < 0)
75 return -E_F_SETFL;
76 return 1;
77 }
78
79 /**
80 * set a file descriptor in a fd_set
81 *
82 * \param fd the file descriptor to be set
83 * \param fds the file descriptor set
84 * \param max_fileno highest-numbered file descriptor
85 *
86 * This wrapper for FD_SET() passes its first two arguments to \p FD_SET. Upon
87 * return, \a max_fileno contains the maximum of the old_value and \a fd.
88 *
89 * \sa para_select
90 */
91 void para_fd_set(int fd, fd_set *fds, int *max_fileno)
92 {
93
94 if (fd < 0 || fd >= FD_SETSIZE) {
95 PARA_EMERG_LOG("fatal: tried to add invalid fd %d\n", fd);
96 exit(EXIT_FAILURE);
97 }
98 #if 0
99 {
100 int flags = fcntl(fd, F_GETFL);
101 if (!(flags & O_NONBLOCK)) {
102 PARA_EMERG_LOG("fd %d is a blocking file descriptor\n", fd);
103 exit(EXIT_FAILURE);
104 }
105 }
106 #endif
107 FD_SET(fd, fds);
108 *max_fileno = PARA_MAX(*max_fileno, fd);
109 }
110
111 /**
112 * paraslash's wrapper for fgets(3)
113 * \param line pointer to the buffer to store the line
114 * \param size the size of the buffer given by \a line
115 * \param f the stream to read from
116 *
117 * \return Unlike the standard fgets() function, an integer value
118 * is returned. On success, this function returns 1. On errors, -E_FGETS
119 * is returned. A zero return value indicates an end of file condition.
120 */
121 __must_check int para_fgets(char *line, int size, FILE *f)
122 {
123 again:
124 if (fgets(line, size, f))
125 return 1;
126 if (feof(f))
127 return 0;
128 if (!ferror(f))
129 return -E_FGETS;
130 if (errno != EINTR) {
131 PARA_ERROR_LOG("%s\n", strerror(errno));
132 return -E_FGETS;
133 }
134 clearerr(f);
135 goto again;
136 }
137
138 /**
139 * Paraslash's wrapper for mmap.
140 *
141 * \param length number of bytes to mmap
142 * \param prot either PROT_NONE or the bitwise OR of one or more of
143 * PROT_EXEC PROT_READ PROT_WRITE
144 * \param flags exactly one of MAP_SHARED and MAP_PRIVATE
145 * \param fd the file to mmap from
146 * \param offset mmap start
147 *
148 * \return This function either returns a valid pointer to the mapped area
149 * or calls exit() on errors.
150 */
151 void *para_mmap(size_t length, int prot, int flags, int fd, off_t offset)
152 {
153 void *ret = mmap(NULL, length, prot, flags, fd, offset);
154 if (ret != MAP_FAILED)
155 return ret;
156 PARA_EMERG_LOG("mmap failed: %s\n", strerror(errno));
157 PARA_EMERG_LOG("length: %zu, flags: %d, fd: %d, offset: %zu\n",
158 length, flags, fd, (size_t)offset);
159 exit(EXIT_FAILURE);
160 }
161
162 /**
163 * Wrapper for the open(2) system call.
164 *
165 * \param path The filename.
166 * \param flags The usual open(2) flags.
167 * \param mode Specifies the permissions to use.
168 *
169 * The mode parameter must be specified when O_CREAT is in the flags, and is ignored
170 * otherwise.
171 *
172 * \return Positive on success, negative on errors.
173 *
174 * \sa open(2).
175 */
176 int para_open(const char *path, int flags, mode_t mode)
177 {
178 int ret = open(path, flags, mode);
179
180 if (ret >= 0)
181 return ret;
182 switch (errno) {
183 case EEXIST:
184 ret = -E_EXIST;
185 break;
186 case EISDIR:
187 ret = -E_ISDIR;
188 break;
189 case ENOENT:
190 ret = -E_NOENT;
191 break;
192 case EPERM:
193 ret = -E_OPEN_PERM;
194 break;
195 };
196 PARA_ERROR_LOG("failed to open %s: %s\n", path, strerror(errno));
197 return -E_OPEN;
198 }
199
200 /**
201 * Wrapper for chdir(2).
202 *
203 * \param path the specified directory.
204 *
205 * \return Positive on success, negative on errors.
206 */
207 int para_chdir(const char *path)
208 {
209 int ret = chdir(path);
210
211 if (ret >= 0)
212 return 1;
213 switch (errno) {
214 case ENOENT:
215 return -E_NOENT;
216 case EACCES:
217 return -E_CHDIR_PERM;
218 };
219 return -E_CHDIR;
220 }
221
222 /**
223 * Save the cwd and open a given directory.
224 *
225 * \param dirname Path to the directory to open.
226 * \param dir Result pointer.
227 * \param cwd File descriptor of the current working directory.
228 *
229 * \return Positive on success, negative on errors.
230 *
231 * Opening the current directory (".") and calling fchdir() to return is
232 * usually faster and more reliable than saving cwd in some buffer and calling
233 * chdir() afterwards.
234 *
235 * If \a cwd is not \p NULL "." is opened and the resulting file descriptor is
236 * stored in \a cwd. If the function returns success, and \a cwd is not \p
237 * NULL, the caller must close this file descriptor (probably after calling
238 * fchdir(*cwd)).
239 *
240 * On errors, the function undos everything, so the caller needs neither close
241 * any files, nor change back to the original working directory.
242 *
243 * \sa getcwd(3).
244 *
245 */
246 int para_opendir(const char *dirname, DIR **dir, int *cwd)
247 {
248 int ret;
249
250 if (cwd) {
251 ret = para_open(".", O_RDONLY, 0);
252 if (ret < 0)
253 return ret;
254 *cwd = ret;
255 }
256 ret = para_chdir(dirname);
257 if (ret < 0)
258 goto close_cwd;
259 ret = -E_OPENDIR;
260 *dir = opendir(".");
261 if (!*dir)
262 goto change_to_orig_dir;
263 return 1;
264 /* Ignore return value of fchdir() and close(). We're busted anyway. */
265 change_to_orig_dir:
266 if (cwd)
267 fchdir(*cwd);
268 close_cwd:
269 if (cwd)
270 close(*cwd);
271 return ret;
272 }
273
274 /**
275 * A wrapper for fchdir().
276 *
277 * \param fd An open file descriptor
278 *
279 * \return Positive on success, negative on errors.
280 */
281 int para_fchdir(int fd)
282 {
283 if (fchdir(fd) < 0)
284 return -E_FCHDIR;
285 return 1;
286 }
287
288 /**
289 * A wrapper for mkdir(2).
290 *
291 * \param path Name of the directory to create.
292 * \param mode The permissions to use.
293 *
294 * \return positive on success, negative on errors.
295 */
296 int para_mkdir(const char *path, mode_t mode)
297 {
298 if (!mkdir(path, mode))
299 return 1;
300 if (errno == EEXIST)
301 return -E_EXIST;
302 if (errno == ENOSPC)
303 return -E_NOSPC;
304 if (errno == ENOTDIR)
305 return -E_NOTDIR;
306 if (errno == EPERM)
307 return -E_MKDIR_PERM;
308 return -E_MKDIR;
309 }