Merge branch 't/nonblock_api'
[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/uio.h>
15
16 #include "para.h"
17 #include "error.h"
18 #include "string.h"
19 #include "fd.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 * Read from a non-blocking file descriptor into multiple buffers.
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 * \param rfds An optional fd set pointer.
92 * \param num_bytes Result pointer. Contains the number of bytes read from \a fd.
93 *
94 * If \a rfds is not \p NULL and the (non-blocking) file descriptor \a fd is
95 * not set in \a rfds, this function returns early without doing anything.
96 * Otherwise The function tries to read up to \a sz bytes from \a fd. As for
97 * write_nonblock(), EAGAIN is not considered an error condition. However, EOF
98 * is.
99 *
100 * \return Zero or a negative error code. If the underlying call to readv(2)
101 * returned zero (indicating an end of file condition) or failed for some
102 * reason other than \p EAGAIN, a negative return value is returned.
103 *
104 * In any case, \a num_bytes contains the number of bytes that have been
105 * successfully read from \a fd (zero if the first readv() call failed with
106 * EAGAIN). Note that even if the function returns negative, some data might
107 * have been read before the error occured. In this case \a num_bytes is
108 * positive.
109 *
110 * \sa \ref write_nonblock(), read(2), readv(2).
111 */
112 int readv_nonblock(int fd, struct iovec *iov, int iovcnt, fd_set *rfds,
113 size_t *num_bytes)
114 {
115 int ret, i, j;
116
117 *num_bytes = 0;
118 /*
119 * Avoid a shortcoming of select(): Reads from a non-blocking fd might
120 * return EAGAIN even if FD_ISSET() returns true. However, FD_ISSET()
121 * returning false definitely means that no data can currently be read.
122 * This is the common case, so it is worth to avoid the overhead of the
123 * read() system call in this case.
124 */
125 if (rfds && !FD_ISSET(fd, rfds))
126 return 0;
127
128 for (i = 0, j = 0; i < iovcnt;) {
129
130 /* fix up the first iov */
131 assert(j < iov[i].iov_len);
132 iov[i].iov_base += j;
133 iov[i].iov_len -= j;
134 ret = readv(fd, iov + i, iovcnt - i);
135 iov[i].iov_base -= j;
136 iov[i].iov_len += j;
137
138 if (ret == 0)
139 return -E_EOF;
140 if (ret < 0) {
141 if (errno == EAGAIN)
142 return 0;
143 return -ERRNO_TO_PARA_ERROR(errno);
144 }
145 *num_bytes += ret;
146 while (ret > 0) {
147 if (ret < iov[i].iov_len - j) {
148 j += ret;
149 break;
150 }
151 ret -= iov[i].iov_len - j;
152 j = 0;
153 if (++i >= iovcnt)
154 break;
155 }
156 }
157 return 0;
158 }
159
160 /**
161 * Read from a non-blocking file descriptor into a single buffer.
162 *
163 * \param fd The file descriptor to read from.
164 * \param buf The buffer to read data to.
165 * \param sz The size of \a buf.
166 * \param rfds \see \ref readv_nonblock().
167 * \param num_bytes \see \ref readv_nonblock().
168 *
169 * This is a simple wrapper for readv_nonblock() which uses an iovec with a single
170 * buffer.
171 *
172 * \return The return value of the underlying call to readv_nonblock().
173 */
174 int read_nonblock(int fd, void *buf, size_t sz, fd_set *rfds, size_t *num_bytes)
175 {
176 struct iovec iov = {.iov_base = buf, .iov_len = sz};
177 return readv_nonblock(fd, &iov, 1, rfds, num_bytes);
178 }
179
180 /**
181 * Read a buffer and check its content for a pattern.
182 *
183 * \param fd The file descriptor to receive from.
184 * \param pattern The expected pattern.
185 * \param bufsize The size of the internal buffer.
186 * \param rfds Passed to read_nonblock().
187 *
188 * This function tries to read at most \a bufsize bytes from the non-blocking
189 * file descriptor \a fd. If at least \p strlen(\a pattern) bytes have been
190 * received, the beginning of the received buffer is compared with \a pattern,
191 * ignoring case.
192 *
193 * \return Positive if \a pattern was received, negative on errors, zero if no data
194 * was available to read.
195 *
196 * \sa \ref read_nonblock(), \sa strncasecmp(3).
197 */
198 int read_pattern(int fd, const char *pattern, size_t bufsize, fd_set *rfds)
199 {
200 size_t n, len;
201 char *buf = para_malloc(bufsize + 1);
202 int ret = read_nonblock(fd, buf, bufsize, rfds, &n);
203
204 buf[n] = '\0';
205 if (ret < 0)
206 goto out;
207 ret = 0;
208 if (n == 0)
209 goto out;
210 ret = -E_READ_PATTERN;
211 len = strlen(pattern);
212 if (n < len)
213 goto out;
214 if (strncasecmp(buf, pattern, len) != 0)
215 goto out;
216 ret = 1;
217 out:
218 if (ret < 0) {
219 PARA_NOTICE_LOG("%s\n", para_strerror(-ret));
220 PARA_NOTICE_LOG("recvd %zu bytes: %s\n", n, buf);
221 }
222 free(buf);
223 return ret;
224 }
225
226 /**
227 * Check whether a file exists.
228 *
229 * \param fn The file name.
230 *
231 * \return Non-zero iff file exists.
232 */
233 int file_exists(const char *fn)
234 {
235 struct stat statbuf;
236
237 return !stat(fn, &statbuf);
238 }
239
240 /**
241 * Paraslash's wrapper for select(2).
242 *
243 * It calls select(2) (with no exceptfds) and starts over if select() was
244 * interrupted by a signal.
245 *
246 * \param n The highest-numbered descriptor in any of the two sets, plus 1.
247 * \param readfds fds that should be checked for readability.
248 * \param writefds fds that should be checked for writablility.
249 * \param timeout_tv upper bound on the amount of time elapsed before select()
250 * returns.
251 *
252 * \return The return value of the underlying select() call on success, the
253 * negative system error code on errors.
254 *
255 * All arguments are passed verbatim to select(2).
256 * \sa select(2) select_tut(2).
257 */
258 int para_select(int n, fd_set *readfds, fd_set *writefds,
259 struct timeval *timeout_tv)
260 {
261 int ret;
262 do
263 ret = select(n, readfds, writefds, NULL, timeout_tv);
264 while (ret < 0 && errno == EINTR);
265 if (ret < 0)
266 return -ERRNO_TO_PARA_ERROR(errno);
267 return ret;
268 }
269
270 /**
271 * Set a file descriptor to blocking mode.
272 *
273 * \param fd The file descriptor.
274 *
275 * \return Standard.
276 */
277 __must_check int mark_fd_blocking(int fd)
278 {
279 int flags = fcntl(fd, F_GETFL);
280 if (flags < 0)
281 return -ERRNO_TO_PARA_ERROR(errno);
282 flags = fcntl(fd, F_SETFL, ((long)flags) & ~O_NONBLOCK);
283 if (flags < 0)
284 return -ERRNO_TO_PARA_ERROR(errno);
285 return 1;
286 }
287
288 /**
289 * Set a file descriptor to non-blocking mode.
290 *
291 * \param fd The file descriptor.
292 *
293 * \return Standard.
294 */
295 __must_check int mark_fd_nonblocking(int fd)
296 {
297 int flags = fcntl(fd, F_GETFL);
298 if (flags < 0)
299 return -ERRNO_TO_PARA_ERROR(errno);
300 flags = fcntl(fd, F_SETFL, ((long)flags) | O_NONBLOCK);
301 if (flags < 0)
302 return -ERRNO_TO_PARA_ERROR(errno);
303 return 1;
304 }
305
306 /**
307 * Set a file descriptor in a fd_set.
308 *
309 * \param fd The file descriptor to be set.
310 * \param fds The file descriptor set.
311 * \param max_fileno Highest-numbered file descriptor.
312 *
313 * This wrapper for FD_SET() passes its first two arguments to \p FD_SET. Upon
314 * return, \a max_fileno contains the maximum of the old_value and \a fd.
315 *
316 * \sa para_select.
317 */
318 void para_fd_set(int fd, fd_set *fds, int *max_fileno)
319 {
320 assert(fd >= 0 && fd < FD_SETSIZE);
321 #if 0
322 {
323 int flags = fcntl(fd, F_GETFL);
324 if (!(flags & O_NONBLOCK)) {
325 PARA_EMERG_LOG("fd %d is a blocking file descriptor\n", fd);
326 exit(EXIT_FAILURE);
327 }
328 }
329 #endif
330 FD_SET(fd, fds);
331 *max_fileno = PARA_MAX(*max_fileno, fd);
332 }
333
334 /**
335 * Paraslash's wrapper for fgets(3).
336 *
337 * \param line Pointer to the buffer to store the line.
338 * \param size The size of the buffer given by \a line.
339 * \param f The stream to read from.
340 *
341 * \return Unlike the standard fgets() function, an integer value
342 * is returned. On success, this function returns 1. On errors, -E_FGETS
343 * is returned. A zero return value indicates an end of file condition.
344 */
345 __must_check int para_fgets(char *line, int size, FILE *f)
346 {
347 again:
348 if (fgets(line, size, f))
349 return 1;
350 if (feof(f))
351 return 0;
352 if (!ferror(f))
353 return -E_FGETS;
354 if (errno != EINTR) {
355 PARA_ERROR_LOG("%s\n", strerror(errno));
356 return -E_FGETS;
357 }
358 clearerr(f);
359 goto again;
360 }
361
362 /**
363 * Paraslash's wrapper for mmap.
364 *
365 * \param length Number of bytes to mmap.
366 * \param prot Either PROT_NONE or the bitwise OR of one or more of
367 * PROT_EXEC PROT_READ PROT_WRITE.
368 * \param flags Exactly one of MAP_SHARED and MAP_PRIVATE.
369 * \param fd The file to mmap from.
370 * \param offset Mmap start.
371 * \param map Result pointer.
372 *
373 * \return Standard.
374 *
375 * \sa mmap(2).
376 */
377 int para_mmap(size_t length, int prot, int flags, int fd, off_t offset,
378 void *map)
379 {
380 void **m = map;
381
382 errno = EINVAL;
383 if (!length)
384 goto err;
385 *m = mmap(NULL, length, prot, flags, fd, offset);
386 if (*m != MAP_FAILED)
387 return 1;
388 err:
389 *m = NULL;
390 return -ERRNO_TO_PARA_ERROR(errno);
391 }
392
393 /**
394 * Wrapper for the open(2) system call.
395 *
396 * \param path The filename.
397 * \param flags The usual open(2) flags.
398 * \param mode Specifies the permissions to use.
399 *
400 * The mode parameter must be specified when O_CREAT is in the flags, and is
401 * ignored otherwise.
402 *
403 * \return The file descriptor on success, negative on errors.
404 *
405 * \sa open(2).
406 */
407 int para_open(const char *path, int flags, mode_t mode)
408 {
409 int ret = open(path, flags, mode);
410
411 if (ret >= 0)
412 return ret;
413 return -ERRNO_TO_PARA_ERROR(errno);
414 }
415
416 /**
417 * Wrapper for chdir(2).
418 *
419 * \param path The specified directory.
420 *
421 * \return Standard.
422 */
423 int para_chdir(const char *path)
424 {
425 int ret = chdir(path);
426
427 if (ret >= 0)
428 return 1;
429 return -ERRNO_TO_PARA_ERROR(errno);
430 }
431
432 /**
433 * Save the cwd and open a given directory.
434 *
435 * \param dirname Path to the directory to open.
436 * \param dir Result pointer.
437 * \param cwd File descriptor of the current working directory.
438 *
439 * \return Standard.
440 *
441 * Opening the current directory (".") and calling fchdir() to return is
442 * usually faster and more reliable than saving cwd in some buffer and calling
443 * chdir() afterwards.
444 *
445 * If \a cwd is not \p NULL "." is opened and the resulting file descriptor is
446 * stored in \a cwd. If the function returns success, and \a cwd is not \p
447 * NULL, the caller must close this file descriptor (probably after calling
448 * fchdir(*cwd)).
449 *
450 * On errors, the function undos everything, so the caller needs neither close
451 * any files, nor change back to the original working directory.
452 *
453 * \sa getcwd(3).
454 *
455 */
456 int para_opendir(const char *dirname, DIR **dir, int *cwd)
457 {
458 int ret;
459
460 if (cwd) {
461 ret = para_open(".", O_RDONLY, 0);
462 if (ret < 0)
463 return ret;
464 *cwd = ret;
465 }
466 ret = para_chdir(dirname);
467 if (ret < 0)
468 goto close_cwd;
469 *dir = opendir(".");
470 if (*dir)
471 return 1;
472 ret = -ERRNO_TO_PARA_ERROR(errno);
473 /* Ignore return value of fchdir() and close(). We're busted anyway. */
474 if (cwd) {
475 int __a_unused ret2 = fchdir(*cwd); /* STFU, gcc */
476 }
477 close_cwd:
478 if (cwd)
479 close(*cwd);
480 return ret;
481 }
482
483 /**
484 * A wrapper for fchdir().
485 *
486 * \param fd An open file descriptor.
487 *
488 * \return Standard.
489 */
490 int para_fchdir(int fd)
491 {
492 if (fchdir(fd) < 0)
493 return -ERRNO_TO_PARA_ERROR(errno);
494 return 1;
495 }
496
497 /**
498 * A wrapper for mkdir(2).
499 *
500 * \param path Name of the directory to create.
501 * \param mode The permissions to use.
502 *
503 * \return Standard.
504 */
505 int para_mkdir(const char *path, mode_t mode)
506 {
507 if (!mkdir(path, mode))
508 return 1;
509 return -ERRNO_TO_PARA_ERROR(errno);
510 }
511
512 /**
513 * Open a file and map it into memory.
514 *
515 * \param path Name of the regular file to map.
516 * \param open_mode Either \p O_RDONLY or \p O_RDWR.
517 * \param map On success, the mapping is returned here.
518 * \param size size of the mapping.
519 * \param fd_ptr The file descriptor of the mapping.
520 *
521 * If \a fd_ptr is \p NULL, the file descriptor resulting from the underlying
522 * open call is closed after mmap(). Otherwise the file is kept open and the
523 * file descriptor is returned in \a fd_ptr.
524 *
525 * \return Standard.
526 *
527 * \sa para_open(), mmap(2).
528 */
529 int mmap_full_file(const char *path, int open_mode, void **map,
530 size_t *size, int *fd_ptr)
531 {
532 int fd, ret, mmap_prot, mmap_flags;
533 struct stat file_status;
534
535 if (open_mode == O_RDONLY) {
536 mmap_prot = PROT_READ;
537 mmap_flags = MAP_PRIVATE;
538 } else {
539 mmap_prot = PROT_READ | PROT_WRITE;
540 mmap_flags = MAP_SHARED;
541 }
542 ret = para_open(path, open_mode, 0);
543 if (ret < 0)
544 return ret;
545 fd = ret;
546 if (fstat(fd, &file_status) < 0) {
547 ret = -ERRNO_TO_PARA_ERROR(errno);
548 goto out;
549 }
550 *size = file_status.st_size;
551 ret = para_mmap(*size, mmap_prot, mmap_flags, fd, 0, map);
552 out:
553 if (ret < 0 || !fd_ptr)
554 close(fd);
555 else
556 *fd_ptr = fd;
557 return ret;
558 }
559
560 /**
561 * A wrapper for munmap(2).
562 *
563 * \param start The start address of the memory mapping.
564 * \param length The size of the mapping.
565 *
566 * \return Standard.
567 *
568 * \sa munmap(2), mmap_full_file().
569 */
570 int para_munmap(void *start, size_t length)
571 {
572 int err;
573 if (munmap(start, length) >= 0)
574 return 1;
575 err = errno;
576 PARA_ERROR_LOG("munmap (%p/%zu) failed: %s\n", start, length,
577 strerror(err));
578 return -ERRNO_TO_PARA_ERROR(err);
579 }
580
581 /**
582 * Check a file descriptor for writability.
583 *
584 * \param fd The file descriptor.
585 *
586 * \return positive if fd is ready for writing, zero if it isn't, negative if
587 * an error occurred.
588 */
589
590 int write_ok(int fd)
591 {
592 struct timeval tv;
593 fd_set wfds;
594
595 FD_ZERO(&wfds);
596 FD_SET(fd, &wfds);
597 tv.tv_sec = 0;
598 tv.tv_usec = 0;
599 return para_select(fd + 1, NULL, &wfds, &tv);
600 }
601
602 /**
603 * Ensure that file descriptors 0, 1, and 2 are valid.
604 *
605 * Common approach that opens /dev/null until it gets a file descriptor greater
606 * than two.
607 *
608 * \sa okir's Black Hats Manual.
609 */
610 void valid_fd_012(void)
611 {
612 while (1) {
613 int fd = open("/dev/null", O_RDWR);
614 if (fd < 0)
615 exit(EXIT_FAILURE);
616 if (fd > 2) {
617 close(fd);
618 break;
619 }
620 }
621 }
622
623 /**
624 * Traverse the given directory recursively.
625 *
626 * \param dirname The directory to traverse.
627 * \param func The function to call for each entry.
628 * \param private_data Pointer to an arbitrary data structure.
629 *
630 * For each regular file under \a dirname, the supplied function \a func is
631 * called. The full path of the regular file and the \a private_data pointer
632 * are passed to \a func. Directories for which the calling process has no
633 * permissions to change to are silently ignored.
634 *
635 * \return Standard.
636 */
637 int for_each_file_in_dir(const char *dirname,
638 int (*func)(const char *, void *), void *private_data)
639 {
640 DIR *dir;
641 struct dirent *entry;
642 int cwd_fd, ret2, ret = para_opendir(dirname, &dir, &cwd_fd);
643
644 if (ret < 0)
645 return ret == -ERRNO_TO_PARA_ERROR(EACCES)? 1 : ret;
646 /* scan cwd recursively */
647 while ((entry = readdir(dir))) {
648 mode_t m;
649 char *tmp;
650 struct stat s;
651
652 if (!strcmp(entry->d_name, "."))
653 continue;
654 if (!strcmp(entry->d_name, ".."))
655 continue;
656 if (lstat(entry->d_name, &s) == -1)
657 continue;
658 m = s.st_mode;
659 if (!S_ISREG(m) && !S_ISDIR(m))
660 continue;
661 tmp = make_message("%s/%s", dirname, entry->d_name);
662 if (!S_ISDIR(m)) {
663 ret = func(tmp, private_data);
664 free(tmp);
665 if (ret < 0)
666 goto out;
667 continue;
668 }
669 /* directory */
670 ret = for_each_file_in_dir(tmp, func, private_data);
671 free(tmp);
672 if (ret < 0)
673 goto out;
674 }
675 ret = 1;
676 out:
677 closedir(dir);
678 ret2 = para_fchdir(cwd_fd);
679 if (ret2 < 0 && ret >= 0)
680 ret = ret2;
681 close(cwd_fd);
682 return ret;
683 }