Merge branch 'maint'
[paraslash.git] / fd.c
1 /*
2 * Copyright (C) 2006 Andre Noll <maan@tuebingen.mpg.de>
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
14 #include "para.h"
15 #include "error.h"
16 #include "string.h"
17 #include "fd.h"
18
19 /**
20 * Write an array of buffers to a file descriptor.
21 *
22 * \param fd The file descriptor.
23 * \param iov Pointer to one or more buffers.
24 * \param iovcnt The number of buffers.
25 *
26 * EAGAIN/EWOULDBLOCK is not considered a fatal error condition. For example
27 * DCCP CCID3 has a sending wait queue which fills up and is emptied
28 * asynchronously. The EAGAIN case means that there is currently no space in
29 * the wait queue, but this can change at any moment.
30 *
31 * \return Negative on fatal errors, number of bytes written else.
32 *
33 * For blocking file descriptors, this function returns either the sum of all
34 * buffer sizes, or the error code of the fatal error that caused the last
35 * write call to fail.
36 *
37 * For nonblocking file descriptors there is a third possibility: Any positive
38 * return value less than the sum of the buffer sizes indicates that some bytes
39 * have been written but the next write would block.
40 *
41 * \sa writev(2), \ref xwrite().
42 */
43 int xwritev(int fd, struct iovec *iov, int iovcnt)
44 {
45 size_t written = 0;
46 int i;
47 struct iovec saved_iov, *curiov;
48
49 i = 0;
50 curiov = iov;
51 saved_iov = *curiov;
52 while (i < iovcnt && curiov->iov_len > 0) {
53 ssize_t ret = writev(fd, curiov, iovcnt - i);
54 if (ret >= 0) {
55 written += ret;
56 while (ret > 0) {
57 if (ret < curiov->iov_len) {
58 curiov->iov_base += ret;
59 curiov->iov_len -= ret;
60 break;
61 }
62 ret -= curiov->iov_len;
63 *curiov = saved_iov;
64 i++;
65 if (i >= iovcnt)
66 return written;
67 curiov++;
68 saved_iov = *curiov;
69 }
70 continue;
71 }
72 if (errno == EINTR)
73 /*
74 * The write() call was interrupted by a signal before
75 * any data was written. Try again.
76 */
77 continue;
78 if (errno == EAGAIN || errno == EWOULDBLOCK)
79 /*
80 * We don't consider this an error. Note that POSIX
81 * allows either error to be returned, and does not
82 * require these constants to have the same value.
83 */
84 return written;
85 /* fatal error */
86 return -ERRNO_TO_PARA_ERROR(errno);
87 }
88 return written;
89 }
90
91 /**
92 * Write a buffer to a file descriptor, re-writing on short writes.
93 *
94 * \param fd The file descriptor.
95 * \param buf The buffer to write.
96 * \param len The number of bytes to write.
97 *
98 * This is a simple wrapper for \ref xwritev().
99 *
100 * \return The return value of the underlying call to \ref xwritev().
101 */
102 int xwrite(int fd, const char *buf, size_t len)
103 {
104 struct iovec iov = {.iov_base = (void *)buf, .iov_len = len};
105 return xwritev(fd, &iov, 1);
106 }
107
108 /**
109 * Write all data to a file descriptor.
110 *
111 * \param fd The file descriptor.
112 * \param buf The buffer to be sent.
113 * \param len The length of \a buf.
114 *
115 * This is like \ref xwrite() but returns \p -E_SHORT_WRITE if not
116 * all data could be written.
117 *
118 * \return Number of bytes written on success, negative error code else.
119 */
120 int write_all(int fd, const char *buf, size_t len)
121 {
122 int ret = xwrite(fd, buf, len);
123
124 if (ret < 0)
125 return ret;
126 if (ret != len)
127 return -E_SHORT_WRITE;
128 return ret;
129 }
130
131 /**
132 * Write a buffer given by a format string.
133 *
134 * \param fd The file descriptor.
135 * \param fmt A format string.
136 *
137 * \return The return value of the underlying call to \ref write_all().
138 */
139 __printf_2_3 int write_va_buffer(int fd, const char *fmt, ...)
140 {
141 char *msg;
142 int ret;
143 va_list ap;
144
145 va_start(ap, fmt);
146 ret = xvasprintf(&msg, fmt, ap);
147 va_end(ap);
148 ret = write_all(fd, msg, ret);
149 free(msg);
150 return ret;
151 }
152
153 /**
154 * Read from a non-blocking file descriptor into multiple buffers.
155 *
156 * \param fd The file descriptor to read from.
157 * \param iov Scatter/gather array used in readv().
158 * \param iovcnt Number of elements in \a iov.
159 * \param rfds An optional fd set pointer.
160 * \param num_bytes Result pointer. Contains the number of bytes read from \a fd.
161 *
162 * If \a rfds is not \p NULL and the (non-blocking) file descriptor \a fd is
163 * not set in \a rfds, this function returns early without doing anything.
164 * Otherwise The function tries to read up to \a sz bytes from \a fd, where \a
165 * sz is the sum of the lengths of all vectors in \a iov. As for xwrite(),
166 * \p EAGAIN is not considered an error condition. However, \p EOF is.
167 *
168 * \return Zero or a negative error code. If the underlying call to readv(2)
169 * returned zero (indicating an end of file condition) or failed for some
170 * reason other than \p EAGAIN, a negative error code is returned.
171 *
172 * In any case, \a num_bytes contains the number of bytes that have been
173 * successfully read from \a fd (zero if the first readv() call failed with
174 * EAGAIN). Note that even if the function returns negative, some data might
175 * have been read before the error occurred. In this case \a num_bytes is
176 * positive.
177 *
178 * \sa \ref xwrite(), read(2), readv(2).
179 */
180 int readv_nonblock(int fd, struct iovec *iov, int iovcnt, fd_set *rfds,
181 size_t *num_bytes)
182 {
183 int ret, i, j;
184
185 *num_bytes = 0;
186 /*
187 * Avoid a shortcoming of select(): Reads from a non-blocking fd might
188 * return EAGAIN even if FD_ISSET() returns true. However, FD_ISSET()
189 * returning false definitely means that no data can currently be read.
190 * This is the common case, so it is worth to avoid the overhead of the
191 * read() system call in this case.
192 */
193 if (rfds && !FD_ISSET(fd, rfds))
194 return 0;
195
196 for (i = 0, j = 0; i < iovcnt;) {
197
198 /* fix up the first iov */
199 assert(j < iov[i].iov_len);
200 iov[i].iov_base += j;
201 iov[i].iov_len -= j;
202 ret = readv(fd, iov + i, iovcnt - i);
203 iov[i].iov_base -= j;
204 iov[i].iov_len += j;
205
206 if (ret == 0)
207 return -E_EOF;
208 if (ret < 0) {
209 if (errno == EAGAIN)
210 return 0;
211 return -ERRNO_TO_PARA_ERROR(errno);
212 }
213 *num_bytes += ret;
214 while (ret > 0) {
215 if (ret < iov[i].iov_len - j) {
216 j += ret;
217 break;
218 }
219 ret -= iov[i].iov_len - j;
220 j = 0;
221 if (++i >= iovcnt)
222 break;
223 }
224 }
225 return 0;
226 }
227
228 /**
229 * Read from a non-blocking file descriptor into a single buffer.
230 *
231 * \param fd The file descriptor to read from.
232 * \param buf The buffer to read data to.
233 * \param sz The size of \a buf.
234 * \param rfds \see \ref readv_nonblock().
235 * \param num_bytes \see \ref readv_nonblock().
236 *
237 * This is a simple wrapper for readv_nonblock() which uses an iovec with a single
238 * buffer.
239 *
240 * \return The return value of the underlying call to readv_nonblock().
241 */
242 int read_nonblock(int fd, void *buf, size_t sz, fd_set *rfds, size_t *num_bytes)
243 {
244 struct iovec iov = {.iov_base = buf, .iov_len = sz};
245 return readv_nonblock(fd, &iov, 1, rfds, num_bytes);
246 }
247
248 /**
249 * Read a buffer and check its content for a pattern.
250 *
251 * \param fd The file descriptor to receive from.
252 * \param pattern The expected pattern.
253 * \param bufsize The size of the internal buffer.
254 * \param rfds Passed to read_nonblock().
255 *
256 * This function tries to read at most \a bufsize bytes from the non-blocking
257 * file descriptor \a fd. If at least \p strlen(\a pattern) bytes have been
258 * received, the beginning of the received buffer is compared with \a pattern,
259 * ignoring case.
260 *
261 * \return Positive if \a pattern was received, negative on errors, zero if no data
262 * was available to read.
263 *
264 * \sa \ref read_nonblock(), \sa strncasecmp(3).
265 */
266 int read_pattern(int fd, const char *pattern, size_t bufsize, fd_set *rfds)
267 {
268 size_t n, len;
269 char *buf = para_malloc(bufsize + 1);
270 int ret = read_nonblock(fd, buf, bufsize, rfds, &n);
271
272 buf[n] = '\0';
273 if (ret < 0)
274 goto out;
275 ret = 0;
276 if (n == 0)
277 goto out;
278 ret = -E_READ_PATTERN;
279 len = strlen(pattern);
280 if (n < len)
281 goto out;
282 if (strncasecmp(buf, pattern, len) != 0)
283 goto out;
284 ret = 1;
285 out:
286 if (ret < 0) {
287 PARA_NOTICE_LOG("%s\n", para_strerror(-ret));
288 PARA_NOTICE_LOG("recvd %zu bytes: %s\n", n, buf);
289 }
290 free(buf);
291 return ret;
292 }
293
294 /**
295 * Check whether a file exists.
296 *
297 * \param fn The file name.
298 *
299 * \return Non-zero iff file exists.
300 */
301 int file_exists(const char *fn)
302 {
303 struct stat statbuf;
304
305 return !stat(fn, &statbuf);
306 }
307
308 /**
309 * Paraslash's wrapper for select(2).
310 *
311 * It calls select(2) (with no exceptfds) and starts over if select() was
312 * interrupted by a signal.
313 *
314 * \param n The highest-numbered descriptor in any of the two sets, plus 1.
315 * \param readfds fds that should be checked for readability.
316 * \param writefds fds that should be checked for writablility.
317 * \param timeout_tv upper bound on the amount of time elapsed before select()
318 * returns.
319 *
320 * \return The return value of the underlying select() call on success, the
321 * negative system error code on errors.
322 *
323 * All arguments are passed verbatim to select(2).
324 * \sa select(2) select_tut(2).
325 */
326 int para_select(int n, fd_set *readfds, fd_set *writefds,
327 struct timeval *timeout_tv)
328 {
329 int ret;
330 do
331 ret = select(n, readfds, writefds, NULL, timeout_tv);
332 while (ret < 0 && errno == EINTR);
333 if (ret < 0)
334 return -ERRNO_TO_PARA_ERROR(errno);
335 return ret;
336 }
337
338 /**
339 * Set a file descriptor to blocking mode.
340 *
341 * \param fd The file descriptor.
342 *
343 * \return Standard.
344 */
345 __must_check int mark_fd_blocking(int fd)
346 {
347 int flags = fcntl(fd, F_GETFL);
348 if (flags < 0)
349 return -ERRNO_TO_PARA_ERROR(errno);
350 flags = fcntl(fd, F_SETFL, ((long)flags) & ~O_NONBLOCK);
351 if (flags < 0)
352 return -ERRNO_TO_PARA_ERROR(errno);
353 return 1;
354 }
355
356 /**
357 * Set a file descriptor to non-blocking mode.
358 *
359 * \param fd The file descriptor.
360 *
361 * \return Standard.
362 */
363 __must_check int mark_fd_nonblocking(int fd)
364 {
365 int flags = fcntl(fd, F_GETFL);
366 if (flags < 0)
367 return -ERRNO_TO_PARA_ERROR(errno);
368 flags = fcntl(fd, F_SETFL, ((long)flags) | O_NONBLOCK);
369 if (flags < 0)
370 return -ERRNO_TO_PARA_ERROR(errno);
371 return 1;
372 }
373
374 /**
375 * Set a file descriptor in a fd_set.
376 *
377 * \param fd The file descriptor to be set.
378 * \param fds The file descriptor set.
379 * \param max_fileno Highest-numbered file descriptor.
380 *
381 * This wrapper for FD_SET() passes its first two arguments to \p FD_SET. Upon
382 * return, \a max_fileno contains the maximum of the old_value and \a fd.
383 *
384 * \sa para_select.
385 */
386 void para_fd_set(int fd, fd_set *fds, int *max_fileno)
387 {
388 assert(fd >= 0 && fd < FD_SETSIZE);
389 #if 0
390 {
391 int flags = fcntl(fd, F_GETFL);
392 if (!(flags & O_NONBLOCK)) {
393 PARA_EMERG_LOG("fd %d is a blocking file descriptor\n", fd);
394 exit(EXIT_FAILURE);
395 }
396 }
397 #endif
398 FD_SET(fd, fds);
399 *max_fileno = PARA_MAX(*max_fileno, fd);
400 }
401
402 /**
403 * Paraslash's wrapper for fgets(3).
404 *
405 * \param line Pointer to the buffer to store the line.
406 * \param size The size of the buffer given by \a line.
407 * \param f The stream to read from.
408 *
409 * \return Unlike the standard fgets() function, an integer value
410 * is returned. On success, this function returns 1. On errors, -E_FGETS
411 * is returned. A zero return value indicates an end of file condition.
412 */
413 __must_check int para_fgets(char *line, int size, FILE *f)
414 {
415 again:
416 if (fgets(line, size, f))
417 return 1;
418 if (feof(f))
419 return 0;
420 if (!ferror(f))
421 return -E_FGETS;
422 if (errno != EINTR) {
423 PARA_ERROR_LOG("%s\n", strerror(errno));
424 return -E_FGETS;
425 }
426 clearerr(f);
427 goto again;
428 }
429
430 /**
431 * Paraslash's wrapper for mmap.
432 *
433 * \param length Number of bytes to mmap.
434 * \param prot Either PROT_NONE or the bitwise OR of one or more of
435 * PROT_EXEC PROT_READ PROT_WRITE.
436 * \param flags Exactly one of MAP_SHARED and MAP_PRIVATE.
437 * \param fd The file to mmap from.
438 * \param offset Mmap start.
439 * \param map Result pointer.
440 *
441 * \return Standard.
442 *
443 * \sa mmap(2).
444 */
445 int para_mmap(size_t length, int prot, int flags, int fd, off_t offset,
446 void *map)
447 {
448 void **m = map;
449
450 errno = EINVAL;
451 if (!length)
452 goto err;
453 *m = mmap(NULL, length, prot, flags, fd, offset);
454 if (*m != MAP_FAILED)
455 return 1;
456 err:
457 *m = NULL;
458 return -ERRNO_TO_PARA_ERROR(errno);
459 }
460
461 /**
462 * Wrapper for the open(2) system call.
463 *
464 * \param path The filename.
465 * \param flags The usual open(2) flags.
466 * \param mode Specifies the permissions to use.
467 *
468 * The mode parameter must be specified when O_CREAT is in the flags, and is
469 * ignored otherwise.
470 *
471 * \return The file descriptor on success, negative on errors.
472 *
473 * \sa open(2).
474 */
475 int para_open(const char *path, int flags, mode_t mode)
476 {
477 int ret = open(path, flags, mode);
478
479 if (ret >= 0)
480 return ret;
481 return -ERRNO_TO_PARA_ERROR(errno);
482 }
483
484 /**
485 * Wrapper for chdir(2).
486 *
487 * \param path The specified directory.
488 *
489 * \return Standard.
490 */
491 int para_chdir(const char *path)
492 {
493 int ret = chdir(path);
494
495 if (ret >= 0)
496 return 1;
497 return -ERRNO_TO_PARA_ERROR(errno);
498 }
499
500 /**
501 * Save the cwd and open a given directory.
502 *
503 * \param dirname Path to the directory to open.
504 * \param dir Result pointer.
505 * \param cwd File descriptor of the current working directory.
506 *
507 * \return Standard.
508 *
509 * Opening the current directory (".") and calling fchdir() to return is
510 * usually faster and more reliable than saving cwd in some buffer and calling
511 * chdir() afterwards.
512 *
513 * If \a cwd is not \p NULL "." is opened and the resulting file descriptor is
514 * stored in \a cwd. If the function returns success, and \a cwd is not \p
515 * NULL, the caller must close this file descriptor (probably after calling
516 * fchdir(*cwd)).
517 *
518 * On errors, the function undos everything, so the caller needs neither close
519 * any files, nor change back to the original working directory.
520 *
521 * \sa getcwd(3).
522 *
523 */
524 static int para_opendir(const char *dirname, DIR **dir, int *cwd)
525 {
526 int ret;
527
528 *dir = NULL;
529 if (cwd) {
530 ret = para_open(".", O_RDONLY, 0);
531 if (ret < 0)
532 return ret;
533 *cwd = ret;
534 }
535 ret = para_chdir(dirname);
536 if (ret < 0)
537 goto close_cwd;
538 *dir = opendir(".");
539 if (*dir)
540 return 1;
541 ret = -ERRNO_TO_PARA_ERROR(errno);
542 /* Ignore return value of fchdir() and close(). We're busted anyway. */
543 if (cwd) {
544 int __a_unused ret2 = fchdir(*cwd); /* STFU, gcc */
545 }
546 close_cwd:
547 if (cwd)
548 close(*cwd);
549 return ret;
550 }
551
552 /**
553 * A wrapper for fchdir().
554 *
555 * \param fd An open file descriptor.
556 *
557 * \return Standard.
558 */
559 static int para_fchdir(int fd)
560 {
561 if (fchdir(fd) < 0)
562 return -ERRNO_TO_PARA_ERROR(errno);
563 return 1;
564 }
565
566 /**
567 * A wrapper for mkdir(2).
568 *
569 * \param path Name of the directory to create.
570 * \param mode The permissions to use.
571 *
572 * \return Standard.
573 */
574 int para_mkdir(const char *path, mode_t mode)
575 {
576 if (!mkdir(path, mode))
577 return 1;
578 return -ERRNO_TO_PARA_ERROR(errno);
579 }
580
581 /**
582 * Open a file and map it into memory.
583 *
584 * \param path Name of the regular file to map.
585 * \param open_mode Either \p O_RDONLY or \p O_RDWR.
586 * \param map On success, the mapping is returned here.
587 * \param size size of the mapping.
588 * \param fd_ptr The file descriptor of the mapping.
589 *
590 * If \a fd_ptr is \p NULL, the file descriptor resulting from the underlying
591 * open call is closed after mmap(). Otherwise the file is kept open and the
592 * file descriptor is returned in \a fd_ptr.
593 *
594 * \return Standard.
595 *
596 * \sa para_open(), mmap(2).
597 */
598 int mmap_full_file(const char *path, int open_mode, void **map,
599 size_t *size, int *fd_ptr)
600 {
601 int fd, ret, mmap_prot, mmap_flags;
602 struct stat file_status;
603
604 if (open_mode == O_RDONLY) {
605 mmap_prot = PROT_READ;
606 mmap_flags = MAP_PRIVATE;
607 } else {
608 mmap_prot = PROT_READ | PROT_WRITE;
609 mmap_flags = MAP_SHARED;
610 }
611 ret = para_open(path, open_mode, 0);
612 if (ret < 0)
613 return ret;
614 fd = ret;
615 if (fstat(fd, &file_status) < 0) {
616 ret = -ERRNO_TO_PARA_ERROR(errno);
617 goto out;
618 }
619 *size = file_status.st_size;
620 /*
621 * If the file is empty, *size is zero and mmap() would return EINVAL
622 * (Invalid argument). This error is common enough to spend an extra
623 * error code which explicitly states the problem.
624 */
625 ret = -E_EMPTY;
626 if (*size == 0)
627 goto out;
628 /*
629 * If fd refers to a directory, mmap() returns ENODEV (No such device),
630 * at least on Linux. "Is a directory" seems to be more to the point.
631 */
632 ret = -ERRNO_TO_PARA_ERROR(EISDIR);
633 if (S_ISDIR(file_status.st_mode))
634 goto out;
635
636 ret = para_mmap(*size, mmap_prot, mmap_flags, fd, 0, map);
637 out:
638 if (ret < 0 || !fd_ptr)
639 close(fd);
640 else
641 *fd_ptr = fd;
642 return ret;
643 }
644
645 /**
646 * A wrapper for munmap(2).
647 *
648 * \param start The start address of the memory mapping.
649 * \param length The size of the mapping.
650 *
651 * \return Standard.
652 *
653 * \sa munmap(2), mmap_full_file().
654 */
655 int para_munmap(void *start, size_t length)
656 {
657 int err;
658
659 if (!start)
660 return 0;
661 if (munmap(start, length) >= 0)
662 return 1;
663 err = errno;
664 PARA_ERROR_LOG("munmap (%p/%zu) failed: %s\n", start, length,
665 strerror(err));
666 return -ERRNO_TO_PARA_ERROR(err);
667 }
668
669 /**
670 * Check a file descriptor for writability.
671 *
672 * \param fd The file descriptor.
673 *
674 * \return positive if fd is ready for writing, zero if it isn't, negative if
675 * an error occurred.
676 */
677
678 int write_ok(int fd)
679 {
680 struct timeval tv;
681 fd_set wfds;
682
683 FD_ZERO(&wfds);
684 FD_SET(fd, &wfds);
685 tv.tv_sec = 0;
686 tv.tv_usec = 0;
687 return para_select(fd + 1, NULL, &wfds, &tv);
688 }
689
690 /**
691 * Ensure that file descriptors 0, 1, and 2 are valid.
692 *
693 * Common approach that opens /dev/null until it gets a file descriptor greater
694 * than two.
695 *
696 * \sa okir's Black Hats Manual.
697 */
698 void valid_fd_012(void)
699 {
700 while (1) {
701 int fd = open("/dev/null", O_RDWR);
702 if (fd < 0)
703 exit(EXIT_FAILURE);
704 if (fd > 2) {
705 close(fd);
706 break;
707 }
708 }
709 }
710
711 /**
712 * Traverse the given directory recursively.
713 *
714 * \param dirname The directory to traverse.
715 * \param func The function to call for each entry.
716 * \param private_data Pointer to an arbitrary data structure.
717 *
718 * For each regular file under \a dirname, the supplied function \a func is
719 * called. The full path of the regular file and the \a private_data pointer
720 * are passed to \a func. Directories for which the calling process has no
721 * permissions to change to are silently ignored.
722 *
723 * \return Standard.
724 */
725 int for_each_file_in_dir(const char *dirname,
726 int (*func)(const char *, void *), void *private_data)
727 {
728 DIR *dir;
729 struct dirent *entry;
730 int cwd_fd, ret2, ret = para_opendir(dirname, &dir, &cwd_fd);
731
732 if (ret < 0)
733 return ret == -ERRNO_TO_PARA_ERROR(EACCES)? 1 : ret;
734 /* scan cwd recursively */
735 while ((entry = readdir(dir))) {
736 mode_t m;
737 char *tmp;
738 struct stat s;
739
740 if (!strcmp(entry->d_name, "."))
741 continue;
742 if (!strcmp(entry->d_name, ".."))
743 continue;
744 if (lstat(entry->d_name, &s) == -1)
745 continue;
746 m = s.st_mode;
747 if (!S_ISREG(m) && !S_ISDIR(m))
748 continue;
749 tmp = make_message("%s/%s", dirname, entry->d_name);
750 if (!S_ISDIR(m)) {
751 ret = func(tmp, private_data);
752 free(tmp);
753 if (ret < 0)
754 goto out;
755 continue;
756 }
757 /* directory */
758 ret = for_each_file_in_dir(tmp, func, private_data);
759 free(tmp);
760 if (ret < 0)
761 goto out;
762 }
763 ret = 1;
764 out:
765 closedir(dir);
766 ret2 = para_fchdir(cwd_fd);
767 if (ret2 < 0 && ret >= 0)
768 ret = ret2;
769 close(cwd_fd);
770 return ret;
771 }