Initial git import.
[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 "error.h"
17
18 /**
19 * Write a buffer to a file descriptor, re-write on short writes.
20 *
21 * \param fd The file descriptor.
22 * \param buf The buffer to be sent.
23 * \param len The length of \a buf.
24 *
25 * \return Standard. In any case, the number of bytes that have been written is
26 * stored in \a len.
27 */
28 int write_all(int fd, const char *buf, size_t *len)
29 {
30 size_t total = *len;
31
32 assert(total);
33 *len = 0;
34 while (*len < total) {
35 int ret = write(fd, buf + *len, total - *len);
36 if (ret == -1)
37 return -ERRNO_TO_ERROR(errno);
38 *len += ret;
39 }
40 return 1;
41 }
42
43 /**
44 * Wrapper for the open(2) system call.
45 *
46 * \param path The filename.
47 * \param flags The usual open(2) flags.
48 * \param mode Specifies the permissions to use.
49 *
50 * The mode parameter must be specified when O_CREAT is in the flags, and is
51 * ignored otherwise.
52 *
53 * \return The file descriptor on success, negative on errors.
54 *
55 * \sa open(2).
56 */
57 int para_open(const char *path, int flags, mode_t mode)
58 {
59 int ret = open(path, flags, mode);
60
61 if (ret >= 0)
62 return ret;
63 return -ERRNO_TO_ERROR(errno);
64 }
65
66 /**
67 * Wrapper for chdir(2).
68 *
69 * \param path The specified directory.
70 *
71 * \return Standard.
72 */
73 static int para_chdir(const char *path)
74 {
75 int ret = chdir(path);
76
77 if (ret >= 0)
78 return 1;
79 return -ERRNO_TO_ERROR(errno);
80 }
81
82 /**
83 * Save the cwd and open a given directory.
84 *
85 * \param dirname Path to the directory to open.
86 * \param dir Result pointer.
87 * \param cwd File descriptor of the current working directory.
88 *
89 * \return Standard.
90 *
91 * Opening the current directory (".") and calling fchdir() to return is
92 * usually faster and more reliable than saving cwd in some buffer and calling
93 * chdir() afterwards.
94 *
95 * If \a cwd is not \p NULL "." is opened and the resulting file descriptor is
96 * stored in \a cwd. If the function returns success, and \a cwd is not \p
97 * NULL, the caller must close this file descriptor (probably after calling
98 * fchdir(*cwd)).
99 *
100 * On errors, the function undos everything, so the caller needs neither close
101 * any files, nor change back to the original working directory.
102 *
103 * \sa getcwd(3).
104 *
105 */
106 int para_opendir(const char *dirname, DIR **dir, int *cwd)
107 {
108 int ret;
109
110 if (cwd) {
111 ret = para_open(".", O_RDONLY, 0);
112 if (ret < 0)
113 return ret;
114 *cwd = ret;
115 }
116 ret = para_chdir(dirname);
117 if (ret < 0)
118 goto close_cwd;
119 *dir = opendir(".");
120 if (*dir)
121 return 1;
122 ret = -ERRNO_TO_ERROR(errno);
123 /* Ignore return value of fchdir() and close(). We're busted anyway. */
124 if (cwd)
125 fchdir(*cwd);
126 close_cwd:
127 if (cwd)
128 close(*cwd);
129 return ret;
130 }
131
132 /**
133 * A wrapper for fchdir().
134 *
135 * \param fd An open file descriptor.
136 *
137 * \return Standard.
138 */
139 int para_fchdir(int fd)
140 {
141 if (fchdir(fd) < 0)
142 return -ERRNO_TO_ERROR(errno);
143 return 1;
144 }
145
146 /**
147 * A wrapper for mkdir(2).
148 *
149 * \param path Name of the directory to create.
150 * \param mode The permissions to use.
151 *
152 * \return Standard.
153 */
154 int para_mkdir(const char *path, mode_t mode)
155 {
156 if (!mkdir(path, mode))
157 return 1;
158 return -ERRNO_TO_ERROR(errno);
159 }
160
161 /**
162 * Open a file and map it into memory.
163 *
164 * \param path Name of the regular file to map.
165 * \param open_mode Either \p O_RDONLY or \p O_RDWR.
166 * \param map On success, the mapping is returned here.
167 * \param size size of the mapping.
168 * \param fd_ptr The file descriptor of the mapping.
169 *
170 * If \a fd_ptr is \p NULL, the file descriptor resulting from the underlying
171 * open call is closed after mmap(). Otherwise the file is kept open and the
172 * file descriptor is returned in \a fd_ptr.
173 *
174 * \return Standard.
175 *
176 * \sa para_open(), mmap(2).
177 */
178 int mmap_full_file(const char *path, int open_mode, void **map,
179 size_t *size, int *fd_ptr)
180 {
181 int fd, ret, mmap_prot, mmap_flags;
182 struct stat file_status;
183
184 if (open_mode == O_RDONLY) {
185 mmap_prot = PROT_READ;
186 mmap_flags = MAP_PRIVATE;
187 } else {
188 mmap_prot = PROT_READ | PROT_WRITE;
189 mmap_flags = MAP_SHARED;
190 }
191 ret = para_open(path, open_mode, 0);
192 if (ret < 0)
193 return ret;
194 fd = ret;
195 if (fstat(fd, &file_status) < 0) {
196 ret = -ERRNO_TO_ERROR(errno);
197 goto out;
198 }
199 *size = file_status.st_size;
200 ret = -E_EMPTY;
201 DEBUG_LOG("%s: size %zu\n", path, *size);
202 if (!*size)
203 goto out;
204 *map = mmap(NULL, *size, mmap_prot, mmap_flags, fd, 0);
205 if (*map == MAP_FAILED) {
206 *map = NULL;
207 ret = -E_MMAP;
208 goto out;
209 }
210 ret = 1;
211 out:
212 if (ret < 0 || !fd_ptr)
213 close(fd);
214 else
215 *fd_ptr = fd;
216 return ret;
217 }
218
219 /**
220 * A wrapper for munmap(2).
221 *
222 * \param start The start address of the memory mapping.
223 * \param length The size of the mapping.
224 *
225 * \return Positive on success, \p -E_MUNMAP on errors.
226 *
227 * \sa munmap(2), mmap_full_file().
228 */
229 int para_munmap(void *start, size_t length)
230 {
231 int err;
232 if (munmap(start, length) >= 0)
233 return 1;
234 err = errno;
235 ERROR_LOG("munmap (%p/%zu) failed: %s\n", start, length,
236 strerror(err));
237 return -ERRNO_TO_ERROR(err);
238 }