Merge branch 'maint'
[paraslash.git] / fd.c
1 /*
2 * Copyright (C) 2006-2010 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 #include <sys/uio.h>
16
17 #include "para.h"
18 #include "error.h"
19 #include "string.h"
20
21 /**
22 * Write a buffer to a file descriptor, re-write on short writes.
23 *
24 * \param fd The file descriptor.
25 * \param buf The buffer to be sent.
26 * \param len The length of \a buf.
27 *
28 * \return Standard. In any case, the number of bytes that have been written is
29 * stored in \a len.
30 */
31 int write_all(int fd, const char *buf, size_t *len)
32 {
33 size_t total = *len;
34
35 assert(total);
36 *len = 0;
37 while (*len < total) {
38 int ret = write(fd, buf + *len, total - *len);
39 if (ret == -1)
40 return -ERRNO_TO_PARA_ERROR(errno);
41 *len += ret;
42 }
43 return 1;
44 }
45
46 /**
47 * Write a buffer to a non-blocking file descriptor.
48 *
49 * \param fd The file descriptor.
50 * \param buf the buffer to write.
51 * \param len the number of bytes of \a buf.
52 * \param max_bytes_per_write Do not write more than that many bytes at once.
53 *
54 * If \a max_bytes_per_write is non-zero, do not send more than that many bytes
55 * per write().
56 *
57 * EAGAIN is not considered an error condition. For example CCID3 has a
58 * sending wait queue which fills up and is emptied asynchronously. The EAGAIN
59 * case means that there is currently no space in the wait queue, but this can
60 * change at any moment.
61 *
62 * \return Negative on errors, number of bytes written else.
63 */
64 int write_nonblock(int fd, const char *buf, size_t len,
65 size_t max_bytes_per_write)
66 {
67 size_t written = 0;
68 int ret = 0;
69
70 while (written < len) {
71 size_t num = len - written;
72
73 if (max_bytes_per_write && max_bytes_per_write < num)
74 num = max_bytes_per_write;
75 ret = write(fd, buf + written, num);
76 if (ret < 0 && errno == EAGAIN)
77 return written;
78 if (ret < 0)
79 return -ERRNO_TO_PARA_ERROR(errno);
80 written += ret;
81 }
82 return written;
83 }
84
85 /**
86 * Simple wrapper for readv().
87 *
88 * \param fd The file descriptor to read from.
89 * \param iov Scatter/gather array used in readv().
90 * \param iovcnt Number of elements in \a iov.
91 *
92 * \return A negative error code on errors, the return value of the underlying
93 * call to readv() otherwise.
94 *
95 * \sa readv(2).
96 */
97 int para_readv(int fd, struct iovec *iov, int iovcnt)
98 {
99 int ret = readv(fd, iov, iovcnt);
100
101 if (ret < 0)
102 return -ERRNO_TO_PARA_ERROR(errno);
103 return ret;
104 }
105
106 /**
107 * Check whether a file exists.
108 *
109 * \param fn The file name.
110 *
111 * \return Non-zero iff file exists.
112 */
113 int file_exists(const char *fn)
114 {
115 struct stat statbuf;
116
117 return !stat(fn, &statbuf);
118 }
119
120 /**
121 * Paraslash's wrapper for select(2).
122 *
123 * It calls select(2) (with no exceptfds) and starts over if select() was
124 * interrupted by a signal.
125 *
126 * \param n The highest-numbered descriptor in any of the two sets, plus 1.
127 * \param readfds fds that should be checked for readability.
128 * \param writefds fds that should be checked for writablility.
129 * \param timeout_tv upper bound on the amount of time elapsed before select()
130 * returns.
131 *
132 * \return The return value of the underlying select() call on success, the
133 * negative system error code on errors.
134 *
135 * All arguments are passed verbatim to select(2).
136 * \sa select(2) select_tut(2).
137 */
138 int para_select(int n, fd_set *readfds, fd_set *writefds,
139 struct timeval *timeout_tv)
140 {
141 int ret;
142 do
143 ret = select(n, readfds, writefds, NULL, timeout_tv);
144 while (ret < 0 && errno == EINTR);
145 if (ret < 0)
146 return -ERRNO_TO_PARA_ERROR(errno);
147 return ret;
148 }
149
150 /**
151 * Set a file descriptor to blocking mode.
152 *
153 * \param fd The file descriptor.
154 *
155 * \return Standard.
156 */
157 __must_check int mark_fd_blocking(int fd)
158 {
159 int flags = fcntl(fd, F_GETFL);
160 if (flags < 0)
161 return -ERRNO_TO_PARA_ERROR(errno);
162 flags = fcntl(fd, F_SETFL, ((long)flags) & ~O_NONBLOCK);
163 if (flags < 0)
164 return -ERRNO_TO_PARA_ERROR(errno);
165 return 1;
166 }
167
168 /**
169 * Set a file descriptor to non-blocking mode.
170 *
171 * \param fd The file descriptor.
172 *
173 * \return Standard.
174 */
175 __must_check int mark_fd_nonblocking(int fd)
176 {
177 int flags = fcntl(fd, F_GETFL);
178 if (flags < 0)
179 return -ERRNO_TO_PARA_ERROR(errno);
180 flags = fcntl(fd, F_SETFL, ((long)flags) | O_NONBLOCK);
181 if (flags < 0)
182 return -ERRNO_TO_PARA_ERROR(errno);
183 return 1;
184 }
185
186 /**
187 * Set a file descriptor in a fd_set.
188 *
189 * \param fd The file descriptor to be set.
190 * \param fds The file descriptor set.
191 * \param max_fileno Highest-numbered file descriptor.
192 *
193 * This wrapper for FD_SET() passes its first two arguments to \p FD_SET. Upon
194 * return, \a max_fileno contains the maximum of the old_value and \a fd.
195 *
196 * \sa para_select.
197 */
198 void para_fd_set(int fd, fd_set *fds, int *max_fileno)
199 {
200 assert(fd >= 0 && fd < FD_SETSIZE);
201 #if 0
202 {
203 int flags = fcntl(fd, F_GETFL);
204 if (!(flags & O_NONBLOCK)) {
205 PARA_EMERG_LOG("fd %d is a blocking file descriptor\n", fd);
206 exit(EXIT_FAILURE);
207 }
208 }
209 #endif
210 FD_SET(fd, fds);
211 *max_fileno = PARA_MAX(*max_fileno, fd);
212 }
213
214 /**
215 * Paraslash's wrapper for fgets(3).
216 *
217 * \param line Pointer to the buffer to store the line.
218 * \param size The size of the buffer given by \a line.
219 * \param f The stream to read from.
220 *
221 * \return Unlike the standard fgets() function, an integer value
222 * is returned. On success, this function returns 1. On errors, -E_FGETS
223 * is returned. A zero return value indicates an end of file condition.
224 */
225 __must_check int para_fgets(char *line, int size, FILE *f)
226 {
227 again:
228 if (fgets(line, size, f))
229 return 1;
230 if (feof(f))
231 return 0;
232 if (!ferror(f))
233 return -E_FGETS;
234 if (errno != EINTR) {
235 PARA_ERROR_LOG("%s\n", strerror(errno));
236 return -E_FGETS;
237 }
238 clearerr(f);
239 goto again;
240 }
241
242 /**
243 * Paraslash's wrapper for mmap.
244 *
245 * \param length Number of bytes to mmap.
246 * \param prot Either PROT_NONE or the bitwise OR of one or more of
247 * PROT_EXEC PROT_READ PROT_WRITE.
248 * \param flags Exactly one of MAP_SHARED and MAP_PRIVATE.
249 * \param fd The file to mmap from.
250 * \param offset Mmap start.
251 * \param map Result pointer.
252 *
253 * \return Standard.
254 *
255 * \sa mmap(2).
256 */
257 int para_mmap(size_t length, int prot, int flags, int fd, off_t offset,
258 void *map)
259 {
260 void **m = map;
261
262 errno = EINVAL;
263 if (!length)
264 goto err;
265 *m = mmap(NULL, length, prot, flags, fd, offset);
266 if (*m != MAP_FAILED)
267 return 1;
268 err:
269 *m = NULL;
270 return -ERRNO_TO_PARA_ERROR(errno);
271 }
272
273 /**
274 * Wrapper for the open(2) system call.
275 *
276 * \param path The filename.
277 * \param flags The usual open(2) flags.
278 * \param mode Specifies the permissions to use.
279 *
280 * The mode parameter must be specified when O_CREAT is in the flags, and is
281 * ignored otherwise.
282 *
283 * \return The file descriptor on success, negative on errors.
284 *
285 * \sa open(2).
286 */
287 int para_open(const char *path, int flags, mode_t mode)
288 {
289 int ret = open(path, flags, mode);
290
291 if (ret >= 0)
292 return ret;
293 return -ERRNO_TO_PARA_ERROR(errno);
294 }
295
296 /**
297 * Wrapper for chdir(2).
298 *
299 * \param path The specified directory.
300 *
301 * \return Standard.
302 */
303 int para_chdir(const char *path)
304 {
305 int ret = chdir(path);
306
307 if (ret >= 0)
308 return 1;
309 return -ERRNO_TO_PARA_ERROR(errno);
310 }
311
312 /**
313 * Save the cwd and open a given directory.
314 *
315 * \param dirname Path to the directory to open.
316 * \param dir Result pointer.
317 * \param cwd File descriptor of the current working directory.
318 *
319 * \return Standard.
320 *
321 * Opening the current directory (".") and calling fchdir() to return is
322 * usually faster and more reliable than saving cwd in some buffer and calling
323 * chdir() afterwards.
324 *
325 * If \a cwd is not \p NULL "." is opened and the resulting file descriptor is
326 * stored in \a cwd. If the function returns success, and \a cwd is not \p
327 * NULL, the caller must close this file descriptor (probably after calling
328 * fchdir(*cwd)).
329 *
330 * On errors, the function undos everything, so the caller needs neither close
331 * any files, nor change back to the original working directory.
332 *
333 * \sa getcwd(3).
334 *
335 */
336 int para_opendir(const char *dirname, DIR **dir, int *cwd)
337 {
338 int ret;
339
340 if (cwd) {
341 ret = para_open(".", O_RDONLY, 0);
342 if (ret < 0)
343 return ret;
344 *cwd = ret;
345 }
346 ret = para_chdir(dirname);
347 if (ret < 0)
348 goto close_cwd;
349 *dir = opendir(".");
350 if (*dir)
351 return 1;
352 ret = -ERRNO_TO_PARA_ERROR(errno);
353 /* Ignore return value of fchdir() and close(). We're busted anyway. */
354 if (cwd) {
355 int __a_unused ret2 = fchdir(*cwd); /* STFU, gcc */
356 }
357 close_cwd:
358 if (cwd)
359 close(*cwd);
360 return ret;
361 }
362
363 /**
364 * A wrapper for fchdir().
365 *
366 * \param fd An open file descriptor.
367 *
368 * \return Standard.
369 */
370 int para_fchdir(int fd)
371 {
372 if (fchdir(fd) < 0)
373 return -ERRNO_TO_PARA_ERROR(errno);
374 return 1;
375 }
376
377 /**
378 * A wrapper for mkdir(2).
379 *
380 * \param path Name of the directory to create.
381 * \param mode The permissions to use.
382 *
383 * \return Standard.
384 */
385 int para_mkdir(const char *path, mode_t mode)
386 {
387 if (!mkdir(path, mode))
388 return 1;
389 return -ERRNO_TO_PARA_ERROR(errno);
390 }
391
392 /**
393 * Open a file and map it into memory.
394 *
395 * \param path Name of the regular file to map.
396 * \param open_mode Either \p O_RDONLY or \p O_RDWR.
397 * \param map On success, the mapping is returned here.
398 * \param size size of the mapping.
399 * \param fd_ptr The file descriptor of the mapping.
400 *
401 * If \a fd_ptr is \p NULL, the file descriptor resulting from the underlying
402 * open call is closed after mmap(). Otherwise the file is kept open and the
403 * file descriptor is returned in \a fd_ptr.
404 *
405 * \return Standard.
406 *
407 * \sa para_open(), mmap(2).
408 */
409 int mmap_full_file(const char *path, int open_mode, void **map,
410 size_t *size, int *fd_ptr)
411 {
412 int fd, ret, mmap_prot, mmap_flags;
413 struct stat file_status;
414
415 if (open_mode == O_RDONLY) {
416 mmap_prot = PROT_READ;
417 mmap_flags = MAP_PRIVATE;
418 } else {
419 mmap_prot = PROT_READ | PROT_WRITE;
420 mmap_flags = MAP_SHARED;
421 }
422 ret = para_open(path, open_mode, 0);
423 if (ret < 0)
424 return ret;
425 fd = ret;
426 if (fstat(fd, &file_status) < 0) {
427 ret = -ERRNO_TO_PARA_ERROR(errno);
428 goto out;
429 }
430 *size = file_status.st_size;
431 ret = para_mmap(*size, mmap_prot, mmap_flags, fd, 0, map);
432 out:
433 if (ret < 0 || !fd_ptr)
434 close(fd);
435 else
436 *fd_ptr = fd;
437 return ret;
438 }
439
440 /**
441 * A wrapper for munmap(2).
442 *
443 * \param start The start address of the memory mapping.
444 * \param length The size of the mapping.
445 *
446 * \return Standard.
447 *
448 * \sa munmap(2), mmap_full_file().
449 */
450 int para_munmap(void *start, size_t length)
451 {
452 int err;
453 if (munmap(start, length) >= 0)
454 return 1;
455 err = errno;
456 PARA_ERROR_LOG("munmap (%p/%zu) failed: %s\n", start, length,
457 strerror(err));
458 return -ERRNO_TO_PARA_ERROR(err);
459 }
460
461 /**
462 * Check a file descriptor for writability.
463 *
464 * \param fd The file descriptor.
465 *
466 * \return positive if fd is ready for writing, zero if it isn't, negative if
467 * an error occurred.
468 */
469
470 int write_ok(int fd)
471 {
472 struct timeval tv;
473 fd_set wfds;
474
475 FD_ZERO(&wfds);
476 FD_SET(fd, &wfds);
477 tv.tv_sec = 0;
478 tv.tv_usec = 0;
479 return para_select(fd + 1, NULL, &wfds, &tv);
480 }
481
482 /**
483 * Ensure that file descriptors 0, 1, and 2 are valid.
484 *
485 * Common approach that opens /dev/null until it gets a file descriptor greater
486 * than two.
487 *
488 * \sa okir's Black Hats Manual.
489 */
490 void valid_fd_012(void)
491 {
492 while (1) {
493 int fd = open("/dev/null", O_RDWR);
494 if (fd < 0)
495 exit(EXIT_FAILURE);
496 if (fd > 2) {
497 close(fd);
498 break;
499 }
500 }
501 }
502
503 /**
504 * Traverse the given directory recursively.
505 *
506 * \param dirname The directory to traverse.
507 * \param func The function to call for each entry.
508 * \param private_data Pointer to an arbitrary data structure.
509 *
510 * For each regular file under \a dirname, the supplied function \a func is
511 * called. The full path of the regular file and the \a private_data pointer
512 * are passed to \a func. Directories for which the calling process has no
513 * permissions to change to are silently ignored.
514 *
515 * \return Standard.
516 */
517 int for_each_file_in_dir(const char *dirname,
518 int (*func)(const char *, void *), void *private_data)
519 {
520 DIR *dir;
521 struct dirent *entry;
522 int cwd_fd, ret2, ret = para_opendir(dirname, &dir, &cwd_fd);
523
524 if (ret < 0)
525 return ret == -ERRNO_TO_PARA_ERROR(EACCES)? 1 : ret;
526 /* scan cwd recursively */
527 while ((entry = readdir(dir))) {
528 mode_t m;
529 char *tmp;
530 struct stat s;
531
532 if (!strcmp(entry->d_name, "."))
533 continue;
534 if (!strcmp(entry->d_name, ".."))
535 continue;
536 if (lstat(entry->d_name, &s) == -1)
537 continue;
538 m = s.st_mode;
539 if (!S_ISREG(m) && !S_ISDIR(m))
540 continue;
541 tmp = make_message("%s/%s", dirname, entry->d_name);
542 if (!S_ISDIR(m)) {
543 ret = func(tmp, private_data);
544 free(tmp);
545 if (ret < 0)
546 goto out;
547 continue;
548 }
549 /* directory */
550 ret = for_each_file_in_dir(tmp, func, private_data);
551 free(tmp);
552 if (ret < 0)
553 goto out;
554 }
555 ret = 1;
556 out:
557 closedir(dir);
558 ret2 = para_fchdir(cwd_fd);
559 if (ret2 < 0 && ret >= 0)
560 ret = ret2;
561 close(cwd_fd);
562 return ret;
563 }