Get rid of E_FCHDIR.
[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 on success, the
44 * negative system error code on errors.
45 *
46 * All arguments are passed verbatim to select(2).
47 * \sa select(2) select_tut(2).
48 */
49 int para_select(int n, fd_set *readfds, fd_set *writefds,
50 struct timeval *timeout_tv)
51 {
52 int ret, err;
53 do {
54 ret = select(n, readfds, writefds, NULL, timeout_tv);
55 err = errno;
56 } while (ret < 0 && err == EINTR);
57 if (ret < 0)
58 return -ERRNO_TO_PARA_ERROR(errno);
59 return ret;
60 }
61
62 /**
63 * Set a file descriptor to non-blocking mode.
64 *
65 * \param fd The file descriptor.
66 *
67 * \return Standard.
68 */
69 int mark_fd_nonblock(int fd)
70 {
71 int flags = fcntl(fd, F_GETFL);
72 if (flags < 0)
73 return -ERRNO_TO_PARA_ERROR(errno);
74 flags = fcntl(fd, F_SETFL, ((long)flags) | O_NONBLOCK);
75 if (flags < 0)
76 return -ERRNO_TO_PARA_ERROR(errno);
77 return 1;
78 }
79
80 /**
81 * set a file descriptor in a fd_set
82 *
83 * \param fd the file descriptor to be set
84 * \param fds the file descriptor set
85 * \param max_fileno highest-numbered file descriptor
86 *
87 * This wrapper for FD_SET() passes its first two arguments to \p FD_SET. Upon
88 * return, \a max_fileno contains the maximum of the old_value and \a fd.
89 *
90 * \sa para_select
91 */
92 void para_fd_set(int fd, fd_set *fds, int *max_fileno)
93 {
94
95 if (fd < 0 || fd >= FD_SETSIZE) {
96 PARA_EMERG_LOG("fatal: tried to add invalid fd %d\n", fd);
97 exit(EXIT_FAILURE);
98 }
99 #if 0
100 {
101 int flags = fcntl(fd, F_GETFL);
102 if (!(flags & O_NONBLOCK)) {
103 PARA_EMERG_LOG("fd %d is a blocking file descriptor\n", fd);
104 exit(EXIT_FAILURE);
105 }
106 }
107 #endif
108 FD_SET(fd, fds);
109 *max_fileno = PARA_MAX(*max_fileno, fd);
110 }
111
112 /**
113 * paraslash's wrapper for fgets(3)
114 * \param line pointer to the buffer to store the line
115 * \param size the size of the buffer given by \a line
116 * \param f the stream to read from
117 *
118 * \return Unlike the standard fgets() function, an integer value
119 * is returned. On success, this function returns 1. On errors, -E_FGETS
120 * is returned. A zero return value indicates an end of file condition.
121 */
122 __must_check int para_fgets(char *line, int size, FILE *f)
123 {
124 again:
125 if (fgets(line, size, f))
126 return 1;
127 if (feof(f))
128 return 0;
129 if (!ferror(f))
130 return -E_FGETS;
131 if (errno != EINTR) {
132 PARA_ERROR_LOG("%s\n", strerror(errno));
133 return -E_FGETS;
134 }
135 clearerr(f);
136 goto again;
137 }
138
139 /**
140 * Paraslash's wrapper for mmap.
141 *
142 * \param length number of bytes to mmap
143 * \param prot either PROT_NONE or the bitwise OR of one or more of
144 * PROT_EXEC PROT_READ PROT_WRITE
145 * \param flags exactly one of MAP_SHARED and MAP_PRIVATE
146 * \param fd the file to mmap from
147 * \param offset mmap start
148 *
149 * \return This function either returns a valid pointer to the mapped area
150 * or calls exit() on errors.
151 */
152 void *para_mmap(size_t length, int prot, int flags, int fd, off_t offset)
153 {
154 void *ret = mmap(NULL, length, prot, flags, fd, offset);
155 if (ret != MAP_FAILED)
156 return ret;
157 PARA_EMERG_LOG("mmap failed: %s\n", strerror(errno));
158 PARA_EMERG_LOG("length: %zu, flags: %d, fd: %d, offset: %zu\n",
159 length, flags, fd, (size_t)offset);
160 exit(EXIT_FAILURE);
161 }
162
163 /**
164 * Wrapper for the open(2) system call.
165 *
166 * \param path The filename.
167 * \param flags The usual open(2) flags.
168 * \param mode Specifies the permissions to use.
169 *
170 * The mode parameter must be specified when O_CREAT is in the flags, and is ignored
171 * otherwise.
172 *
173 * \return The file descriptor on success, negative on errors.
174 *
175 * \sa open(2).
176 */
177 int para_open(const char *path, int flags, mode_t mode)
178 {
179 int ret = open(path, flags, mode);
180
181 if (ret >= 0)
182 return ret;
183 return -ERRNO_TO_PARA_ERROR(errno);
184 }
185
186 /**
187 * Wrapper for chdir(2).
188 *
189 * \param path the specified directory.
190 *
191 * \return Positive on success, negative on errors.
192 */
193 int para_chdir(const char *path)
194 {
195 int ret = chdir(path);
196
197 if (ret >= 0)
198 return 1;
199 return -ERRNO_TO_PARA_ERROR(errno);
200 }
201
202 /**
203 * Save the cwd and open a given directory.
204 *
205 * \param dirname Path to the directory to open.
206 * \param dir Result pointer.
207 * \param cwd File descriptor of the current working directory.
208 *
209 * \return Standard.
210 *
211 * Opening the current directory (".") and calling fchdir() to return is
212 * usually faster and more reliable than saving cwd in some buffer and calling
213 * chdir() afterwards.
214 *
215 * If \a cwd is not \p NULL "." is opened and the resulting file descriptor is
216 * stored in \a cwd. If the function returns success, and \a cwd is not \p
217 * NULL, the caller must close this file descriptor (probably after calling
218 * fchdir(*cwd)).
219 *
220 * On errors, the function undos everything, so the caller needs neither close
221 * any files, nor change back to the original working directory.
222 *
223 * \sa getcwd(3).
224 *
225 */
226 int para_opendir(const char *dirname, DIR **dir, int *cwd)
227 {
228 int ret;
229
230 if (cwd) {
231 ret = para_open(".", O_RDONLY, 0);
232 if (ret < 0)
233 return ret;
234 *cwd = ret;
235 }
236 ret = para_chdir(dirname);
237 if (ret < 0)
238 goto close_cwd;
239 *dir = opendir(".");
240 if (*dir)
241 return 1;
242 ret = -ERRNO_TO_PARA_ERROR(errno);
243 /* Ignore return value of fchdir() and close(). We're busted anyway. */
244 change_to_orig_dir:
245 if (cwd)
246 fchdir(*cwd);
247 close_cwd:
248 if (cwd)
249 close(*cwd);
250 return ret;
251 }
252
253 /**
254 * A wrapper for fchdir().
255 *
256 * \param fd An open file descriptor
257 *
258 * \return Standard.
259 */
260 int para_fchdir(int fd)
261 {
262 if (fchdir(fd) < 0)
263 return -ERRNO_TO_PARA_ERROR(errno);
264 return 1;
265 }
266
267 /**
268 * A wrapper for mkdir(2).
269 *
270 * \param path Name of the directory to create.
271 * \param mode The permissions to use.
272 *
273 * \return Standard.
274 */
275 int para_mkdir(const char *path, mode_t mode)
276 {
277 if (!mkdir(path, mode))
278 return 1;
279 return -ERRNO_TO_PARA_ERROR(errno);
280 }