Add para_readv(), a simple wrapper for readv().
[paraslash.git] / fd.c
1 /*
2 * Copyright (C) 2006-2009 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 <regex.h>
10 #include <sys/types.h>
11 #include <dirent.h>
12 #include <sys/mman.h>
13 #include <fcntl.h>
14 #include <sys/select.h>
15
16 #include "para.h"
17 #include "error.h"
18 #include "string.h"
19
20 /**
21 * Write a buffer to a file descriptor, re-write on short writes.
22 *
23 * \param fd The file descriptor.
24 * \param buf The buffer to be sent.
25 * \param len The length of \a buf.
26 *
27 * \return Standard. In any case, the number of bytes that have been written is
28 * stored in \a len.
29 */
30 int write_all(int fd, const char *buf, size_t *len)
31 {
32 size_t total = *len;
33
34 assert(total);
35 *len = 0;
36 while (*len < total) {
37 int ret = write(fd, buf + *len, total - *len);
38 if (ret == -1)
39 return -ERRNO_TO_PARA_ERROR(errno);
40 *len += ret;
41 }
42 return 1;
43 }
44
45 /**
46 * Write a buffer to a non-blocking file descriptor.
47 *
48 * \param fd The file descriptor.
49 * \param buf the buffer to write.
50 * \param len the number of bytes of \a buf.
51 * \param max_bytes_per_write Do not write more than that many bytes at once.
52 *
53 * If \a max_bytes_per_write is non-zero, do not send more than that many bytes
54 * per write().
55 *
56 * EAGAIN is not considered an error condition. For example CCID3 has a
57 * sending wait queue which fills up and is emptied asynchronously. The EAGAIN
58 * case means that there is currently no space in the wait queue, but this can
59 * change at any moment.
60 *
61 * \return Negative on errors, number of bytes written else.
62 */
63 int write_nonblock(int fd, const char *buf, size_t len,
64 size_t max_bytes_per_write)
65 {
66 size_t written = 0;
67 int ret = 0;
68
69 while (written < len) {
70 size_t num = len - written;
71
72 if (max_bytes_per_write && max_bytes_per_write < num)
73 num = max_bytes_per_write;
74 ret = write(fd, buf + written, num);
75 if (ret < 0 && errno == EAGAIN)
76 return written;
77 if (ret < 0)
78 return -ERRNO_TO_PARA_ERROR(errno);
79 written += ret;
80 }
81 return written;
82 }
83
84 /**
85 * Simple wrapper for readv().
86 *
87 * \param fd The file descriptor to read from.
88 * \param iov Scatter/gather array used in readv().
89 * \param iovcnt Number of elements in \a iov.
90 *
91 * \return A negative error code on errors, the return value of the underlying
92 * call to readv() otherwise.
93 *
94 * \sa readv(2).
95 */
96 int para_readv(int fd, struct iovec *iov, int iovcnt)
97 {
98 int ret = readv(fd, iov, iovcnt);
99
100 if (ret < 0)
101 return -ERRNO_TO_PARA_ERROR(errno);
102 return ret;
103 }
104
105 /**
106 * Check whether a file exists.
107 *
108 * \param fn The file name.
109 *
110 * \return Non-zero iff file exists.
111 */
112 int file_exists(const char *fn)
113 {
114 struct stat statbuf;
115
116 return !stat(fn, &statbuf);
117 }
118
119 /**
120 * Paraslash's wrapper for select(2).
121 *
122 * It calls select(2) (with no exceptfds) and starts over if select() was
123 * interrupted by a signal.
124 *
125 * \param n The highest-numbered descriptor in any of the two sets, plus 1.
126 * \param readfds fds that should be checked for readability.
127 * \param writefds fds that should be checked for writablility.
128 * \param timeout_tv upper bound on the amount of time elapsed before select()
129 * returns.
130 *
131 * \return The return value of the underlying select() call on success, the
132 * negative system error code on errors.
133 *
134 * All arguments are passed verbatim to select(2).
135 * \sa select(2) select_tut(2).
136 */
137 int para_select(int n, fd_set *readfds, fd_set *writefds,
138 struct timeval *timeout_tv)
139 {
140 int ret;
141 do
142 ret = select(n, readfds, writefds, NULL, timeout_tv);
143 while (ret < 0 && errno == EINTR);
144 if (ret < 0)
145 return -ERRNO_TO_PARA_ERROR(errno);
146 return ret;
147 }
148
149 /**
150 * Set a file descriptor to blocking mode.
151 *
152 * \param fd The file descriptor.
153 *
154 * \return Standard.
155 */
156 __must_check int mark_fd_blocking(int fd)
157 {
158 int flags = fcntl(fd, F_GETFL);
159 if (flags < 0)
160 return -ERRNO_TO_PARA_ERROR(errno);
161 flags = fcntl(fd, F_SETFL, ((long)flags) & ~O_NONBLOCK);
162 if (flags < 0)
163 return -ERRNO_TO_PARA_ERROR(errno);
164 return 1;
165 }
166
167 /**
168 * Set a file descriptor to non-blocking mode.
169 *
170 * \param fd The file descriptor.
171 *
172 * \return Standard.
173 */
174 __must_check int mark_fd_nonblocking(int fd)
175 {
176 int flags = fcntl(fd, F_GETFL);
177 if (flags < 0)
178 return -ERRNO_TO_PARA_ERROR(errno);
179 flags = fcntl(fd, F_SETFL, ((long)flags) | O_NONBLOCK);
180 if (flags < 0)
181 return -ERRNO_TO_PARA_ERROR(errno);
182 return 1;
183 }
184
185 /**
186 * Set a file descriptor in a fd_set.
187 *
188 * \param fd The file descriptor to be set.
189 * \param fds The file descriptor set.
190 * \param max_fileno Highest-numbered file descriptor.
191 *
192 * This wrapper for FD_SET() passes its first two arguments to \p FD_SET. Upon
193 * return, \a max_fileno contains the maximum of the old_value and \a fd.
194 *
195 * \sa para_select.
196 */
197 void para_fd_set(int fd, fd_set *fds, int *max_fileno)
198 {
199 assert(fd >= 0 && fd < FD_SETSIZE);
200 #if 0
201 {
202 int flags = fcntl(fd, F_GETFL);
203 if (!(flags & O_NONBLOCK)) {
204 PARA_EMERG_LOG("fd %d is a blocking file descriptor\n", fd);
205 exit(EXIT_FAILURE);
206 }
207 }
208 #endif
209 FD_SET(fd, fds);
210 *max_fileno = PARA_MAX(*max_fileno, fd);
211 }
212
213 /**
214 * Paraslash's wrapper for fgets(3).
215 *
216 * \param line Pointer to the buffer to store the line.
217 * \param size The size of the buffer given by \a line.
218 * \param f The stream to read from.
219 *
220 * \return Unlike the standard fgets() function, an integer value
221 * is returned. On success, this function returns 1. On errors, -E_FGETS
222 * is returned. A zero return value indicates an end of file condition.
223 */
224 __must_check int para_fgets(char *line, int size, FILE *f)
225 {
226 again:
227 if (fgets(line, size, f))
228 return 1;
229 if (feof(f))
230 return 0;
231 if (!ferror(f))
232 return -E_FGETS;
233 if (errno != EINTR) {
234 PARA_ERROR_LOG("%s\n", strerror(errno));
235 return -E_FGETS;
236 }
237 clearerr(f);
238 goto again;
239 }
240
241 /**
242 * Paraslash's wrapper for mmap.
243 *
244 * \param length Number of bytes to mmap.
245 * \param prot Either PROT_NONE or the bitwise OR of one or more of
246 * PROT_EXEC PROT_READ PROT_WRITE.
247 * \param flags Exactly one of MAP_SHARED and MAP_PRIVATE.
248 * \param fd The file to mmap from.
249 * \param offset Mmap start.
250 * \param map Result pointer.
251 *
252 * \return Standard.
253 *
254 * \sa mmap(2).
255 */
256 int para_mmap(size_t length, int prot, int flags, int fd, off_t offset,
257 void *map)
258 {
259 void **m = map;
260
261 errno = EINVAL;
262 if (!length)
263 goto err;
264 *m = mmap(NULL, length, prot, flags, fd, offset);
265 if (*m != MAP_FAILED)
266 return 1;
267 err:
268 *m = NULL;
269 return -ERRNO_TO_PARA_ERROR(errno);
270 }
271
272 /**
273 * Wrapper for the open(2) system call.
274 *
275 * \param path The filename.
276 * \param flags The usual open(2) flags.
277 * \param mode Specifies the permissions to use.
278 *
279 * The mode parameter must be specified when O_CREAT is in the flags, and is
280 * ignored otherwise.
281 *
282 * \return The file descriptor on success, negative on errors.
283 *
284 * \sa open(2).
285 */
286 int para_open(const char *path, int flags, mode_t mode)
287 {
288 int ret = open(path, flags, mode);
289
290 if (ret >= 0)
291 return ret;
292 return -ERRNO_TO_PARA_ERROR(errno);
293 }
294
295 /**
296 * Wrapper for chdir(2).
297 *
298 * \param path The specified directory.
299 *
300 * \return Standard.
301 */
302 int para_chdir(const char *path)
303 {
304 int ret = chdir(path);
305
306 if (ret >= 0)
307 return 1;
308 return -ERRNO_TO_PARA_ERROR(errno);
309 }
310
311 /**
312 * Save the cwd and open a given directory.
313 *
314 * \param dirname Path to the directory to open.
315 * \param dir Result pointer.
316 * \param cwd File descriptor of the current working directory.
317 *
318 * \return Standard.
319 *
320 * Opening the current directory (".") and calling fchdir() to return is
321 * usually faster and more reliable than saving cwd in some buffer and calling
322 * chdir() afterwards.
323 *
324 * If \a cwd is not \p NULL "." is opened and the resulting file descriptor is
325 * stored in \a cwd. If the function returns success, and \a cwd is not \p
326 * NULL, the caller must close this file descriptor (probably after calling
327 * fchdir(*cwd)).
328 *
329 * On errors, the function undos everything, so the caller needs neither close
330 * any files, nor change back to the original working directory.
331 *
332 * \sa getcwd(3).
333 *
334 */
335 int para_opendir(const char *dirname, DIR **dir, int *cwd)
336 {
337 int ret;
338
339 if (cwd) {
340 ret = para_open(".", O_RDONLY, 0);
341 if (ret < 0)
342 return ret;
343 *cwd = ret;
344 }
345 ret = para_chdir(dirname);
346 if (ret < 0)
347 goto close_cwd;
348 *dir = opendir(".");
349 if (*dir)
350 return 1;
351 ret = -ERRNO_TO_PARA_ERROR(errno);
352 /* Ignore return value of fchdir() and close(). We're busted anyway. */
353 if (cwd) {
354 int __a_unused ret2 = fchdir(*cwd); /* STFU, gcc */
355 }
356 close_cwd:
357 if (cwd)
358 close(*cwd);
359 return ret;
360 }
361
362 /**
363 * A wrapper for fchdir().
364 *
365 * \param fd An open file descriptor.
366 *
367 * \return Standard.
368 */
369 int para_fchdir(int fd)
370 {
371 if (fchdir(fd) < 0)
372 return -ERRNO_TO_PARA_ERROR(errno);
373 return 1;
374 }
375
376 /**
377 * A wrapper for mkdir(2).
378 *
379 * \param path Name of the directory to create.
380 * \param mode The permissions to use.
381 *
382 * \return Standard.
383 */
384 int para_mkdir(const char *path, mode_t mode)
385 {
386 if (!mkdir(path, mode))
387 return 1;
388 return -ERRNO_TO_PARA_ERROR(errno);
389 }
390
391 /**
392 * Open a file and map it into memory.
393 *
394 * \param path Name of the regular file to map.
395 * \param open_mode Either \p O_RDONLY or \p O_RDWR.
396 * \param map On success, the mapping is returned here.
397 * \param size size of the mapping.
398 * \param fd_ptr The file descriptor of the mapping.
399 *
400 * If \a fd_ptr is \p NULL, the file descriptor resulting from the underlying
401 * open call is closed after mmap(). Otherwise the file is kept open and the
402 * file descriptor is returned in \a fd_ptr.
403 *
404 * \return Standard.
405 *
406 * \sa para_open(), mmap(2).
407 */
408 int mmap_full_file(const char *path, int open_mode, void **map,
409 size_t *size, int *fd_ptr)
410 {
411 int fd, ret, mmap_prot, mmap_flags;
412 struct stat file_status;
413
414 if (open_mode == O_RDONLY) {
415 mmap_prot = PROT_READ;
416 mmap_flags = MAP_PRIVATE;
417 } else {
418 mmap_prot = PROT_READ | PROT_WRITE;
419 mmap_flags = MAP_SHARED;
420 }
421 ret = para_open(path, open_mode, 0);
422 if (ret < 0)
423 return ret;
424 fd = ret;
425 if (fstat(fd, &file_status) < 0) {
426 ret = -ERRNO_TO_PARA_ERROR(errno);
427 goto out;
428 }
429 *size = file_status.st_size;
430 ret = para_mmap(*size, mmap_prot, mmap_flags, fd, 0, map);
431 out:
432 if (ret < 0 || !fd_ptr)
433 close(fd);
434 else
435 *fd_ptr = fd;
436 return ret;
437 }
438
439 /**
440 * A wrapper for munmap(2).
441 *
442 * \param start The start address of the memory mapping.
443 * \param length The size of the mapping.
444 *
445 * \return Standard.
446 *
447 * \sa munmap(2), mmap_full_file().
448 */
449 int para_munmap(void *start, size_t length)
450 {
451 int err;
452 if (munmap(start, length) >= 0)
453 return 1;
454 err = errno;
455 PARA_ERROR_LOG("munmap (%p/%zu) failed: %s\n", start, length,
456 strerror(err));
457 return -ERRNO_TO_PARA_ERROR(err);
458 }
459
460 /**
461 * Check a file descriptor for writability.
462 *
463 * \param fd The file descriptor.
464 *
465 * \return positive if fd is ready for writing, zero if it isn't, negative if
466 * an error occurred.
467 */
468
469 int write_ok(int fd)
470 {
471 struct timeval tv;
472 fd_set wfds;
473
474 FD_ZERO(&wfds);
475 FD_SET(fd, &wfds);
476 tv.tv_sec = 0;
477 tv.tv_usec = 0;
478 return para_select(fd + 1, NULL, &wfds, &tv);
479 }
480
481 /**
482 * Ensure that file descriptors 0, 1, and 2 are valid.
483 *
484 * Common approach that opens /dev/null until it gets a file descriptor greater
485 * than two.
486 *
487 * \sa okir's Black Hats Manual.
488 */
489 void valid_fd_012(void)
490 {
491 while (1) {
492 int fd = open("/dev/null", O_RDWR);
493 if (fd < 0)
494 exit(EXIT_FAILURE);
495 if (fd > 2) {
496 close(fd);
497 break;
498 }
499 }
500 }
501
502 /**
503 * Traverse the given directory recursively.
504 *
505 * \param dirname The directory to traverse.
506 * \param func The function to call for each entry.
507 * \param private_data Pointer to an arbitrary data structure.
508 *
509 * For each regular file under \a dirname, the supplied function \a func is
510 * called. The full path of the regular file and the \a private_data pointer
511 * are passed to \a func. Directories for which the calling process has no
512 * permissions to change to are silently ignored.
513 *
514 * \return Standard.
515 */
516 int for_each_file_in_dir(const char *dirname,
517 int (*func)(const char *, void *), void *private_data)
518 {
519 DIR *dir;
520 struct dirent *entry;
521 int cwd_fd, ret2, ret = para_opendir(dirname, &dir, &cwd_fd);
522
523 if (ret < 0)
524 return ret == -ERRNO_TO_PARA_ERROR(EACCES)? 1 : ret;
525 /* scan cwd recursively */
526 while ((entry = readdir(dir))) {
527 mode_t m;
528 char *tmp;
529 struct stat s;
530
531 if (!strcmp(entry->d_name, "."))
532 continue;
533 if (!strcmp(entry->d_name, ".."))
534 continue;
535 if (lstat(entry->d_name, &s) == -1)
536 continue;
537 m = s.st_mode;
538 if (!S_ISREG(m) && !S_ISDIR(m))
539 continue;
540 tmp = make_message("%s/%s", dirname, entry->d_name);
541 if (!S_ISDIR(m)) {
542 ret = func(tmp, private_data);
543 free(tmp);
544 if (ret < 0)
545 goto out;
546 continue;
547 }
548 /* directory */
549 ret = for_each_file_in_dir(tmp, func, private_data);
550 free(tmp);
551 if (ret < 0)
552 goto out;
553 }
554 ret = 1;
555 out:
556 closedir(dir);
557 ret2 = para_fchdir(cwd_fd);
558 if (ret2 < 0 && ret >= 0)
559 ret = ret2;
560 close(cwd_fd);
561 return ret;
562 }