Return -E_OSL_NOENT if stat/open fails with errno == ENOENT.
[osl.git] / util.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 util.c Helper functions needed by both libosl and oslfsck. */
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 "util.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 : -E_OSL_WRITE;
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 == ENOENT? -E_OSL_NOENT : -E_OSL_OPEN;
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 * Open a file and map it into memory.
122 *
123 * \param path Name of the regular file to map.
124 * \param open_mode Either \p O_RDONLY or \p O_RDWR.
125 * \param map On success, the mapping is returned here.
126 * \param size size of the mapping.
127 * \param fd_ptr The file descriptor of the mapping.
128 *
129 * If \a fd_ptr is \p NULL, the file descriptor resulting from the underlying
130 * open call is closed after mmap(). Otherwise the file is kept open and the
131 * file descriptor is returned in \a fd_ptr.
132 *
133 * \return Standard.
134 *
135 * \sa osl_open(), mmap(2).
136 */
137 int mmap_full_file(const char *path, int open_mode, void **map,
138 size_t *size, int *fd_ptr)
139 {
140 int fd, ret, mmap_prot, mmap_flags;
141 struct stat file_status;
142
143 if (open_mode == O_RDONLY) {
144 mmap_prot = PROT_READ;
145 mmap_flags = MAP_PRIVATE;
146 } else {
147 mmap_prot = PROT_READ | PROT_WRITE;
148 mmap_flags = MAP_SHARED;
149 }
150 ret = osl_open(path, open_mode, 0);
151 if (ret < 0)
152 return ret;
153 fd = ret;
154 if (fstat(fd, &file_status) < 0) {
155 ret = errno == ENOENT? -E_OSL_NOENT : -E_OSL_STAT;
156 goto out;
157 }
158 *size = file_status.st_size;
159 ret = -E_OSL_EMPTY;
160 DEBUG_LOG("%s: size %zu\n", path, *size);
161 if (!*size)
162 goto out;
163 *map = mmap(NULL, *size, mmap_prot, mmap_flags, fd, 0);
164 if (*map == MAP_FAILED) {
165 *map = NULL;
166 ret = -E_OSL_MMAP;
167 goto out;
168 }
169 ret = 1;
170 out:
171 if (ret < 0 || !fd_ptr)
172 close(fd);
173 else
174 *fd_ptr = fd;
175 return ret;
176 }
177
178 /**
179 * A wrapper for munmap(2).
180 *
181 * \param start The start address of the memory mapping.
182 * \param length The size of the mapping.
183 *
184 * \return Positive on success, \p -E_MUNMAP on errors.
185 *
186 * \sa munmap(2), mmap_full_file().
187 */
188 int osl_munmap(void *start, size_t length)
189 {
190 int err;
191 if (munmap(start, length) >= 0)
192 return 1;
193 err = errno;
194 ERROR_LOG("munmap (%p/%zu) failed: %s\n", start, length,
195 strerror(err));
196 return -E_OSL_MUNMAP;
197 }
198
199 /**
200 * Allocate a sufficiently large string and print into it.
201 *
202 * \param fmt A usual format string.
203 *
204 * Produce output according to \p fmt. No artificial bound on the length of the
205 * resulting string is imposed.
206 *
207 * \return This function either returns a pointer to a string that must be
208 * freed by the caller or \p NULL if memory allocation failed.
209 *
210 * \sa printf(3).
211 */
212 __must_check __printf_1_2 __malloc char *make_message(const char *fmt, ...)
213 {
214 int n;
215 size_t size = 100;
216 char *p = malloc(size);
217
218 if (!p)
219 return NULL;
220 while (1) {
221 char *q;
222 va_list ap;
223 /* Try to print in the allocated space. */
224 va_start(ap, fmt);
225 n = vsnprintf(p, size, fmt, ap);
226 va_end(ap);
227 /* If that worked, return the string. */
228 if (n > -1 && n < size)
229 break;
230 /* Else try again with more space. */
231 if (n > -1) /* glibc 2.1 */
232 size = n + 1; /* precisely what is needed */
233 else /* glibc 2.0 */
234 size *= 2; /* twice the old size */
235 q = realloc(p, size);
236 if (!q) {
237 free(p);
238 return NULL;
239 }
240 p = q;
241 }
242 return p;
243 }
244
245 /**
246 * A wrapper for truncate(2)
247 *
248 * \param path Name of the regular file to truncate
249 * \param size Number of bytes to \b shave \b off
250 *
251 * Truncate the regular file named by \a path by \a size bytes.
252 *
253 * \return Standard.
254 *
255 * \sa truncate(2)
256 */
257 int truncate_file(const char *path, off_t size)
258 {
259 int ret;
260 struct stat statbuf;
261
262 ret = osl_stat(path, &statbuf);
263 if (ret < 0)
264 return ret;
265 ret = -E_OSL_BAD_SIZE;
266 if (statbuf.st_size < size)
267 return ret;
268 if (truncate(path, statbuf.st_size - size) < 0)
269 return -E_OSL_TRUNCATE;
270 return 1;
271 }