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