Add create.c.
[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 Helper functions for file descriptor handling. */
8
9 #include <sys/types.h>
10 #include <dirent.h>
11 #include <sys/mman.h>
12
13 #include "adu.h"
14 #include "error.h"
15
16 /**
17 * Wrapper for the write system call.
18 *
19 * \param fd The file descriptor to write to.
20 * \param buf The buffer to write.
21 * \param size The length of \a buf in bytes.
22 *
23 * This function writes out the given buffer and retries if an interrupt
24 * occurred during the write.
25 *
26 * \return Standard.
27 *
28 * \sa write(2).
29 */
30 ssize_t __write(int fd, const void *buf, size_t size)
31 {
32 ssize_t ret;
33
34 for (;;) {
35 ret = write(fd, buf, size);
36 if ((ret < 0) && (errno == EAGAIN || errno == EINTR))
37 continue;
38 return ret >= 0? ret : -ERRNO_TO_ERROR(errno);
39 }
40 }
41
42 /**
43 * Write the whole buffer to a file descriptor.
44 *
45 * \param fd The file descriptor to write to.
46 * \param buf The buffer to write.
47 * \param size The length of \a buf in bytes.
48 *
49 * This function writes the given buffer and continues on short writes and
50 * when interrupted by a signal.
51 *
52 * \return Standard.
53 */
54 static ssize_t write_all(int fd, const void *buf, size_t size)
55 {
56 // DEBUG_LOG("writing %zu bytes\n", size);
57 const char *b = buf;
58 while (size) {
59 ssize_t ret = __write(fd, b, size);
60 // DEBUG_LOG("ret: %zd\n", ret);
61 if (ret < 0)
62 return ret;
63 b += ret;
64 size -= ret;
65 }
66 return 1;
67 }
68
69 /**
70 * Wrapper for the open(2) system call.
71 *
72 * \param path The filename.
73 * \param flags The usual open(2) flags.
74 * \param mode Specifies the permissions to use.
75 *
76 * The mode parameter must be specified when O_CREAT is in the flags, and is
77 * ignored otherwise.
78 *
79 * \return The file descriptor on success, negative on errors.
80 *
81 * \sa open(2).
82 */
83 static int __open(const char *path, int flags, mode_t mode)
84 {
85 int ret = open(path, flags, mode);
86
87 if (ret >= 0)
88 return ret;
89 return -ERRNO_TO_ERROR(errno);
90 }
91
92 /**
93 * Open a file, write the given buffer and close the file.
94 *
95 * \param filename Full path to the file to open.
96 * \param buf The buffer to write to the file.
97 * \param size The size of \a buf.
98 *
99 * \return Standard.
100 */
101 int adu_write_file(const char *filename, const void *buf, size_t size)
102 {
103 int ret, fd;
104
105 ret = __open(filename, O_WRONLY | O_CREAT | O_EXCL, 0644);
106 if (ret < 0)
107 return ret;
108 fd = ret;
109 ret = write_all(fd, buf, size);
110 if (ret < 0)
111 goto out;
112 ret = 1;
113 out:
114 close(fd);
115 return ret;
116 }
117
118 /**
119 * Wrapper for chdir(2).
120 *
121 * \param path The specified directory.
122 *
123 * \return Standard.
124 */
125 int __chdir(const char *path)
126 {
127 int ret = chdir(path);
128
129 if (ret >= 0)
130 return 1;
131 return -ERRNO_TO_ERROR(errno);
132 }
133
134 /**
135 * Save the cwd and open a given directory.
136 *
137 * \param dirname Path to the directory to open.
138 * \param dir Result pointer.
139 * \param cwd File descriptor of the current working directory.
140 *
141 * \return Standard.
142 *
143 * Opening the current directory (".") and calling fchdir() to return is
144 * usually faster and more reliable than saving cwd in some buffer and calling
145 * chdir() afterwards.
146 *
147 * If \a cwd is not \p NULL "." is opened and the resulting file descriptor is
148 * stored in \a cwd. If the function returns success, and \a cwd is not \p
149 * NULL, the caller must close this file descriptor (probably after calling
150 * fchdir(*cwd)).
151 *
152 * On errors, the function undos everything, so the caller needs neither close
153 * any files, nor change back to the original working directory.
154 *
155 * \sa getcwd(3).
156 *
157 */
158 int adu_opendir(const char *dirname, DIR **dir, int *cwd)
159 {
160 int ret;
161
162 if (cwd) {
163 ret = __open(".", O_RDONLY, 0);
164 if (ret < 0)
165 return ret;
166 *cwd = ret;
167 }
168 ret = __chdir(dirname);
169 if (ret < 0)
170 goto close_cwd;
171 *dir = opendir(".");
172 if (*dir)
173 return 1;
174 ret = -ERRNO_TO_ERROR(errno);
175 /* Ignore return value of fchdir() and close(). We're busted anyway. */
176 if (cwd)
177 fchdir(*cwd);
178 close_cwd:
179 if (cwd)
180 close(*cwd);
181 return ret;
182 }
183
184 /**
185 * A wrapper for fchdir().
186 *
187 * \param fd An open file descriptor.
188 *
189 * \return Standard.
190 */
191 int adu_fchdir(int fd)
192 {
193 if (fchdir(fd) < 0)
194 return -ERRNO_TO_ERROR(errno);
195 return 1;
196 }
197
198 /**
199 * Open a file and map it into memory.
200 *
201 * \param path Name of the regular file to map.
202 * \param open_mode Either \p O_RDONLY or \p O_RDWR.
203 * \param map On success, the mapping is returned here.
204 * \param size size of the mapping.
205 * \param fd_ptr The file descriptor of the mapping.
206 *
207 * If \a fd_ptr is \p NULL, the file descriptor resulting from the underlying
208 * open call is closed after mmap(). Otherwise the file is kept open and the
209 * file descriptor is returned in \a fd_ptr.
210 *
211 * \return Standard.
212 *
213 * \sa mmap(2).
214 */
215 int mmap_full_file(const char *path, int open_mode, void **map,
216 size_t *size, int *fd_ptr)
217 {
218 int fd, ret, mmap_prot, mmap_flags;
219 struct stat file_status;
220
221 if (open_mode == O_RDONLY) {
222 mmap_prot = PROT_READ;
223 mmap_flags = MAP_PRIVATE;
224 } else {
225 mmap_prot = PROT_READ | PROT_WRITE;
226 mmap_flags = MAP_SHARED;
227 }
228 ret = __open(path, open_mode, 0);
229 if (ret < 0)
230 return ret;
231 fd = ret;
232 if (fstat(fd, &file_status) < 0) {
233 ret = -ERRNO_TO_ERROR(errno);
234 goto out;
235 }
236 *size = file_status.st_size;
237 ret = -E_EMPTY;
238 DEBUG_LOG("%s: size %zu\n", path, *size);
239 if (!*size)
240 goto out;
241 *map = mmap(NULL, *size, mmap_prot, mmap_flags, fd, 0);
242 if (*map == MAP_FAILED) {
243 *map = NULL;
244 ret = -E_MMAP;
245 goto out;
246 }
247 ret = 1;
248 out:
249 if (ret < 0 || !fd_ptr)
250 close(fd);
251 else
252 *fd_ptr = fd;
253 return ret;
254 }
255
256 /**
257 * A wrapper for munmap(2).
258 *
259 * \param start The start address of the memory mapping.
260 * \param length The size of the mapping.
261 *
262 * \return Positive on success, \p -E_MUNMAP on errors.
263 *
264 * \sa munmap(2), mmap_full_file().
265 */
266 int adu_munmap(void *start, size_t length)
267 {
268 int err;
269 if (munmap(start, length) >= 0)
270 return 1;
271 err = errno;
272 ERROR_LOG("munmap (%p/%zu) failed: %s\n", start, length,
273 strerror(err));
274 return -ERRNO_TO_ERROR(err);
275 }