1519ac5552dbf106d7edbec5faf2776066c7e0f1
[osl.git] / fd.c
1 /*
2 * Copyright (C) 2006-2008 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 "log.h"
16 #include "osl.h"
17 #include "error.h"
18
19 /**
20 * Wrapper for the write system call.
21 *
22 * \param fd The file descriptor to write to.
23 * \param buf The buffer to write.
24 * \param size The length of \a buf in bytes.
25 *
26 * This function writes out the given buffer and retries if an interrupt
27 * occurred during the write.
28 *
29 * \return On success, the number of bytes written is returned, otherwise, a
30 * negative error code is returned.
31 *
32 * \sa write(2).
33 */
34 static ssize_t __write(int fd, const void *buf, size_t size)
35 {
36 ssize_t ret;
37
38 for (;;) {
39 ret = write(fd, buf, size);
40 if ((ret < 0) && (errno == EAGAIN || errno == EINTR))
41 continue;
42 return ret >= 0? ret : -ERRNO_TO_ERROR(errno);
43 }
44 }
45
46 /**
47 * Write a buffer to a file descriptor, re-write on short writes.
48 *
49 * \param fd The file descriptor.
50 * \param buf The buffer to be sent.
51 * \param len The length of \a buf.
52 *
53 * \return Standard. In any case, the number of bytes that have been written is
54 * stored in \a len.
55 */
56 int write_all(int fd, const char *buf, size_t *len)
57 {
58 size_t total = *len;
59
60 assert(total);
61 *len = 0;
62 while (*len < total) {
63 int ret = __write(fd, buf + *len, total - *len);
64 if (ret < 0)
65 return ret;
66 *len += ret;
67 }
68 return 1;
69 }
70
71 /**
72 * Wrapper for the open(2) system call.
73 *
74 * \param path The filename.
75 * \param flags The usual open(2) flags.
76 * \param mode Specifies the permissions to use.
77 *
78 * The mode parameter must be specified when O_CREAT is in the flags, and is
79 * ignored otherwise.
80 *
81 * \return The file descriptor on success, negative on errors.
82 *
83 * \sa open(2).
84 */
85 int osl_open(const char *path, int flags, mode_t mode)
86 {
87 int ret = open(path, flags, mode);
88
89 if (ret >= 0)
90 return ret;
91 return -ERRNO_TO_ERROR(errno);
92 }
93
94 /**
95 * Open a file, write the given buffer and close the file.
96 *
97 * \param filename Full path to the file to open.
98 * \param buf The buffer to write to the file.
99 * \param size The size of \a buf.
100 *
101 * \return Standard.
102 */
103 int write_file(const char *filename, const void *buf, size_t size)
104 {
105 int ret, fd;
106
107 ret = osl_open(filename, O_WRONLY | O_CREAT | O_EXCL, 0644);
108 if (ret < 0)
109 return ret;
110 fd = ret;
111 ret = write_all(fd, buf, &size);
112 if (ret < 0)
113 goto out;
114 ret = 1;
115 out:
116 close(fd);
117 return ret;
118 }
119
120 /**
121 * Wrapper for chdir(2).
122 *
123 * \param path The specified directory.
124 *
125 * \return Standard.
126 */
127 static int para_chdir(const char *path)
128 {
129 int ret = chdir(path);
130
131 if (ret >= 0)
132 return 1;
133 return -ERRNO_TO_ERROR(errno);
134 }
135
136 /**
137 * Save the cwd and open a given directory.
138 *
139 * \param dirname Path to the directory to open.
140 * \param dir Result pointer.
141 * \param cwd File descriptor of the current working directory.
142 *
143 * \return Standard.
144 *
145 * Opening the current directory (".") and calling fchdir() to return is
146 * usually faster and more reliable than saving cwd in some buffer and calling
147 * chdir() afterwards.
148 *
149 * If \a cwd is not \p NULL "." is opened and the resulting file descriptor is
150 * stored in \a cwd. If the function returns success, and \a cwd is not \p
151 * NULL, the caller must close this file descriptor (probably after calling
152 * fchdir(*cwd)).
153 *
154 * On errors, the function undos everything, so the caller needs neither close
155 * any files, nor change back to the original working directory.
156 *
157 * \sa getcwd(3).
158 *
159 */
160 int para_opendir(const char *dirname, DIR **dir, int *cwd)
161 {
162 int ret;
163
164 if (cwd) {
165 ret = osl_open(".", O_RDONLY, 0);
166 if (ret < 0)
167 return ret;
168 *cwd = ret;
169 }
170 ret = para_chdir(dirname);
171 if (ret < 0)
172 goto close_cwd;
173 *dir = opendir(".");
174 if (*dir)
175 return 1;
176 ret = -ERRNO_TO_ERROR(errno);
177 /* Ignore return value of fchdir() and close(). We're busted anyway. */
178 if (cwd)
179 fchdir(*cwd);
180 close_cwd:
181 if (cwd)
182 close(*cwd);
183 return ret;
184 }
185
186 /**
187 * A wrapper for fchdir().
188 *
189 * \param fd An open file descriptor.
190 *
191 * \return Standard.
192 */
193 int para_fchdir(int fd)
194 {
195 if (fchdir(fd) < 0)
196 return -ERRNO_TO_ERROR(errno);
197 return 1;
198 }
199
200 /**
201 * Open a file and map it into memory.
202 *
203 * \param path Name of the regular file to map.
204 * \param open_mode Either \p O_RDONLY or \p O_RDWR.
205 * \param map On success, the mapping is returned here.
206 * \param size size of the mapping.
207 * \param fd_ptr The file descriptor of the mapping.
208 *
209 * If \a fd_ptr is \p NULL, the file descriptor resulting from the underlying
210 * open call is closed after mmap(). Otherwise the file is kept open and the
211 * file descriptor is returned in \a fd_ptr.
212 *
213 * \return Standard.
214 *
215 * \sa osl_open(), mmap(2).
216 */
217 int mmap_full_file(const char *path, int open_mode, void **map,
218 size_t *size, int *fd_ptr)
219 {
220 int fd, ret, mmap_prot, mmap_flags;
221 struct stat file_status;
222
223 if (open_mode == O_RDONLY) {
224 mmap_prot = PROT_READ;
225 mmap_flags = MAP_PRIVATE;
226 } else {
227 mmap_prot = PROT_READ | PROT_WRITE;
228 mmap_flags = MAP_SHARED;
229 }
230 ret = osl_open(path, open_mode, 0);
231 if (ret < 0)
232 return ret;
233 fd = ret;
234 if (fstat(fd, &file_status) < 0) {
235 ret = -ERRNO_TO_ERROR(errno);
236 goto out;
237 }
238 *size = file_status.st_size;
239 ret = -E_OSL_EMPTY;
240 DEBUG_LOG("%s: size %zu\n", path, *size);
241 if (!*size)
242 goto out;
243 *map = mmap(NULL, *size, mmap_prot, mmap_flags, fd, 0);
244 if (*map == MAP_FAILED) {
245 *map = NULL;
246 ret = -E_OSL_MMAP;
247 goto out;
248 }
249 ret = 1;
250 out:
251 if (ret < 0 || !fd_ptr)
252 close(fd);
253 else
254 *fd_ptr = fd;
255 return ret;
256 }
257
258 /**
259 * A wrapper for munmap(2).
260 *
261 * \param start The start address of the memory mapping.
262 * \param length The size of the mapping.
263 *
264 * \return Positive on success, \p -E_MUNMAP on errors.
265 *
266 * \sa munmap(2), mmap_full_file().
267 */
268 int osl_munmap(void *start, size_t length)
269 {
270 int err;
271 if (munmap(start, length) >= 0)
272 return 1;
273 err = errno;
274 ERROR_LOG("munmap (%p/%zu) failed: %s\n", start, length,
275 strerror(err));
276 return -ERRNO_TO_ERROR(err);
277 }
278
279 /**
280 * Allocate a sufficiently large string and print into it.
281 *
282 * \param fmt A usual format string.
283 *
284 * Produce output according to \p fmt. No artificial bound on the length of the
285 * resulting string is imposed.
286 *
287 * \return This function either returns a pointer to a string that must be
288 * freed by the caller or \p NULL if memory allocation failed.
289 *
290 * \sa printf(3).
291 */
292 __must_check __printf_1_2 __malloc char *make_message(const char *fmt, ...)
293 {
294 int n;
295 size_t size = 100;
296 char *p = malloc(size);
297
298 if (!p)
299 return NULL;
300 while (1) {
301 char *q;
302 va_list ap;
303 /* Try to print in the allocated space. */
304 va_start(ap, fmt);
305 n = vsnprintf(p, size, fmt, ap);
306 va_end(ap);
307 /* If that worked, return the string. */
308 if (n > -1 && n < size)
309 break;
310 /* Else try again with more space. */
311 if (n > -1) /* glibc 2.1 */
312 size = n + 1; /* precisely what is needed */
313 else /* glibc 2.0 */
314 size *= 2; /* twice the old size */
315 q = realloc(p, size);
316 if (!q) {
317 free(p);
318 return NULL;
319 }
320 p = q;
321 }
322 return p;
323 }
324
325 /**
326 * A wrapper for truncate(2)
327 *
328 * \param path Name of the regular file to truncate
329 * \param size Number of bytes to \b shave \b off
330 *
331 * Truncate the regular file named by \a path by \a size bytes.
332 *
333 * \return Standard.
334 *
335 * \sa truncate(2)
336 */
337 int truncate_file(const char *path, off_t size)
338 {
339 int ret;
340 struct stat statbuf;
341
342 ret = -E_OSL_STAT;
343 if (stat(path, &statbuf) < 0)
344 goto out;
345 ret = -E_OSL_BAD_SIZE;
346 if (statbuf.st_size < size)
347 goto out;
348 ret = -E_OSL_TRUNC;
349 if (truncate(path, statbuf.st_size - size) < 0)
350 goto out;
351 ret = 1;
352 out:
353 return ret;
354 }
355