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[adu.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 \brief Helper functions for file descriptor handling. */
8
9 #include <sys/types.h>
10 #include <dirent.h>
11 #include <sys/mman.h>
12 #include <string.h>
13
14 #include "adu.h"
15 #include "error.h"
16 #include "string.h"
17
18 /**
19 * Wrapper for the write system call.
20 *
21 * \param fd The file descriptor to write to.
22 * \param buf The buffer to write.
23 * \param size The length of \a buf in bytes.
24 *
25 * This function writes out the given buffer and retries if an interrupt
26 * occurred during the write.
27 *
28 * \return Standard.
29 *
30 * \sa write(2).
31 */
32 ssize_t __write(int fd, const void *buf, size_t size)
33 {
34 ssize_t ret;
35
36 for (;;) {
37 ret = write(fd, buf, size);
38 if ((ret < 0) && (errno == EAGAIN || errno == EINTR))
39 continue;
40 return ret >= 0? ret : -ERRNO_TO_ERROR(errno);
41 }
42 }
43
44 /**
45 * Write the whole buffer to a file descriptor.
46 *
47 * \param fd The file descriptor to write to.
48 * \param buf The buffer to write.
49 * \param size The length of \a buf in bytes.
50 *
51 * This function writes the given buffer and continues on short writes and
52 * when interrupted by a signal.
53 *
54 * \return Standard.
55 */
56 static ssize_t write_all(int fd, const void *buf, size_t size)
57 {
58 // DEBUG_LOG("writing %zu bytes\n", size);
59 const char *b = buf;
60 while (size) {
61 ssize_t ret = __write(fd, b, size);
62 // DEBUG_LOG("ret: %zd\n", ret);
63 if (ret < 0)
64 return ret;
65 b += ret;
66 size -= 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 static int __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 adu_write_file(const char *filename, const void *buf, size_t size)
104 {
105 int ret, fd;
106
107 ret = __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 int __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 adu_opendir(const char *dirname, DIR **dir, int *cwd)
161 {
162 int ret;
163
164 if (cwd) {
165 ret = __open(".", O_RDONLY, 0);
166 if (ret < 0)
167 return ret;
168 *cwd = ret;
169 }
170 ret = __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 adu_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 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 = __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_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_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 adu_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 __must_check __malloc static char *adu_dirname(const char *name)
280 {
281 char *p, *ret;
282
283 if (!name || !*name)
284 return NULL;
285 ret = adu_strdup(name);
286 p = strrchr(ret, '/');
287 if (!p)
288 *ret = '\0';
289 else
290 *p = '\0';
291 return ret;
292 }
293
294 /**
295 * Recursive mkdir
296 *
297 * \param p Full path that should be created.
298 *
299 * \param mode Use this mode when creating directories.
300 *
301 * \return 0 if successful, -E_MKDIR on errors.
302 */
303 int mkpath(const char *p, mode_t mode)
304 {
305 char *parent, *path;
306 int ret = -E_MKDIR;
307
308 DEBUG_LOG("%s\n", p);
309 if (strcmp(p, ".") == 0 || strcmp(p, "/") == 0 || strcmp(p, "") == 0) {
310 DEBUG_LOG("reached beginning of path\n");
311 return 0;
312 }
313 path = adu_strdup(p);
314 parent = adu_dirname(p);
315 if (!parent)
316 goto out;
317 ret = mkpath(parent, mode);
318 if (ret < 0)
319 goto out;
320 INFO_LOG("making dir %s\n", path);
321 ret = 0;
322 if ((mkdir(path, mode) == -1) && (errno != EEXIST))
323 ret = -E_MKDIR;
324 out:
325 free(parent);
326 free(path);
327 return ret;
328 }