Merge branch 'maint'
[paraslash.git] / fd.c
1 /* Copyright (C) 2006 Andre Noll <maan@tuebingen.mpg.de>, see file COPYING. */
2
3 /** \file fd.c Helper functions for file descriptor handling. */
4
5 #include <regex.h>
6 #include <sys/types.h>
7 #include <dirent.h>
8 #include <sys/mman.h>
9
10 #include "para.h"
11 #include "error.h"
12 #include "string.h"
13 #include "fd.h"
14
15 /**
16 * Change the name or location of a file.
17 *
18 * \param oldpath File to be moved.
19 * \param newpath Destination.
20 *
21 * This is just a simple wrapper for the rename(2) system call which returns a
22 * paraslash error code and prints an error message on failure.
23 *
24 * \return Standard.
25 *
26 * \sa rename(2).
27 */
28 int xrename(const char *oldpath, const char *newpath)
29 {
30 int ret = rename(oldpath, newpath);
31
32 if (ret >= 0)
33 return 1;
34 ret = -ERRNO_TO_PARA_ERROR(errno);
35 PARA_ERROR_LOG("failed to rename %s -> %s\n", oldpath, newpath);
36 return ret;
37 }
38
39 /**
40 * Write an array of buffers to a file descriptor.
41 *
42 * \param fd The file descriptor.
43 * \param iov Pointer to one or more buffers.
44 * \param iovcnt The number of buffers.
45 *
46 * EAGAIN/EWOULDBLOCK is not considered a fatal error condition. For example
47 * DCCP CCID3 has a sending wait queue which fills up and is emptied
48 * asynchronously. The EAGAIN case means that there is currently no space in
49 * the wait queue, but this can change at any moment.
50 *
51 * \return Negative on fatal errors, number of bytes written else.
52 *
53 * For blocking file descriptors, this function returns either the sum of all
54 * buffer sizes, or the error code of the fatal error that caused the last
55 * write call to fail.
56 *
57 * For nonblocking file descriptors there is a third possibility: Any positive
58 * return value less than the sum of the buffer sizes indicates that some bytes
59 * have been written but the next write would block.
60 *
61 * \sa writev(2), \ref xwrite().
62 */
63 int xwritev(int fd, struct iovec *iov, int iovcnt)
64 {
65 size_t written = 0;
66 int i;
67 struct iovec saved_iov, *curiov;
68
69 i = 0;
70 curiov = iov;
71 saved_iov = *curiov;
72 while (i < iovcnt && curiov->iov_len > 0) {
73 ssize_t ret = writev(fd, curiov, iovcnt - i);
74 if (ret >= 0) {
75 written += ret;
76 while (ret > 0) {
77 if (ret < curiov->iov_len) {
78 curiov->iov_base += ret;
79 curiov->iov_len -= ret;
80 break;
81 }
82 ret -= curiov->iov_len;
83 *curiov = saved_iov;
84 i++;
85 if (i >= iovcnt)
86 return written;
87 curiov++;
88 saved_iov = *curiov;
89 }
90 continue;
91 }
92 if (errno == EINTR)
93 /*
94 * The write() call was interrupted by a signal before
95 * any data was written. Try again.
96 */
97 continue;
98 if (errno == EAGAIN || errno == EWOULDBLOCK)
99 /*
100 * We don't consider this an error. Note that POSIX
101 * allows either error to be returned, and does not
102 * require these constants to have the same value.
103 */
104 return written;
105 /* fatal error */
106 return -ERRNO_TO_PARA_ERROR(errno);
107 }
108 return written;
109 }
110
111 /**
112 * Write a buffer to a file descriptor, re-writing on short writes.
113 *
114 * \param fd The file descriptor.
115 * \param buf The buffer to write.
116 * \param len The number of bytes to write.
117 *
118 * This is a simple wrapper for \ref xwritev().
119 *
120 * \return The return value of the underlying call to \ref xwritev().
121 */
122 int xwrite(int fd, const char *buf, size_t len)
123 {
124 struct iovec iov = {.iov_base = (void *)buf, .iov_len = len};
125 return xwritev(fd, &iov, 1);
126 }
127
128 /**
129 * Write all data to a file descriptor.
130 *
131 * \param fd The file descriptor.
132 * \param buf The buffer to be sent.
133 * \param len The length of \a buf.
134 *
135 * This is like \ref xwrite() but returns \p -E_SHORT_WRITE if not
136 * all data could be written.
137 *
138 * \return Number of bytes written on success, negative error code else.
139 */
140 int write_all(int fd, const char *buf, size_t len)
141 {
142 int ret = xwrite(fd, buf, len);
143
144 if (ret < 0)
145 return ret;
146 if (ret != len)
147 return -E_SHORT_WRITE;
148 return ret;
149 }
150
151 /**
152 * Write a buffer given by a format string.
153 *
154 * \param fd The file descriptor.
155 * \param fmt A format string.
156 *
157 * \return The return value of the underlying call to \ref write_all().
158 */
159 __printf_2_3 int write_va_buffer(int fd, const char *fmt, ...)
160 {
161 char *msg;
162 int ret;
163 va_list ap;
164
165 va_start(ap, fmt);
166 ret = xvasprintf(&msg, fmt, ap);
167 va_end(ap);
168 ret = write_all(fd, msg, ret);
169 free(msg);
170 return ret;
171 }
172
173 /**
174 * Read from a non-blocking file descriptor into multiple buffers.
175 *
176 * \param fd The file descriptor to read from.
177 * \param iov Scatter/gather array used in readv().
178 * \param iovcnt Number of elements in \a iov.
179 * \param num_bytes Result pointer. Contains the number of bytes read from \a fd.
180 *
181 * This function tries to read up to sz bytes from fd, where sz is the sum of
182 * the lengths of all vectors in iov. Like \ref xwrite(), EAGAIN and EINTR are
183 * not considered error conditions. However, EOF is.
184 *
185 * \return Zero or a negative error code. If the underlying call to readv(2)
186 * returned zero (indicating an end of file condition) or failed for some
187 * reason other than EAGAIN or EINTR, a negative error code is returned.
188 *
189 * In any case, \a num_bytes contains the number of bytes that have been
190 * successfully read from \a fd (zero if the first readv() call failed with
191 * EAGAIN). Note that even if the function returns negative, some data might
192 * have been read before the error occurred. In this case \a num_bytes is
193 * positive.
194 *
195 * \sa \ref xwrite(), read(2), readv(2).
196 */
197 int readv_nonblock(int fd, struct iovec *iov, int iovcnt, size_t *num_bytes)
198 {
199 int ret, i, j;
200
201 *num_bytes = 0;
202 for (i = 0, j = 0; i < iovcnt;) {
203 /* fix up the first iov */
204 assert(j < iov[i].iov_len);
205 iov[i].iov_base += j;
206 iov[i].iov_len -= j;
207 ret = readv(fd, iov + i, iovcnt - i);
208 iov[i].iov_base -= j;
209 iov[i].iov_len += j;
210
211 if (ret == 0)
212 return -E_EOF;
213 if (ret < 0) {
214 if (errno == EAGAIN || errno == EINTR)
215 return 0;
216 return -ERRNO_TO_PARA_ERROR(errno);
217 }
218 *num_bytes += ret;
219 while (ret > 0) {
220 if (ret < iov[i].iov_len - j) {
221 j += ret;
222 break;
223 }
224 ret -= iov[i].iov_len - j;
225 j = 0;
226 if (++i >= iovcnt)
227 break;
228 }
229 }
230 return 0;
231 }
232
233 /**
234 * Read from a non-blocking file descriptor into a single buffer.
235 *
236 * \param fd The file descriptor to read from.
237 * \param buf The buffer to read data to.
238 * \param sz The size of \a buf.
239 * \param num_bytes \see \ref readv_nonblock().
240 *
241 * This is a simple wrapper for readv_nonblock() which uses an iovec with a single
242 * buffer.
243 *
244 * \return The return value of the underlying call to readv_nonblock().
245 */
246 int read_nonblock(int fd, void *buf, size_t sz, size_t *num_bytes)
247 {
248 struct iovec iov = {.iov_base = buf, .iov_len = sz};
249 return readv_nonblock(fd, &iov, 1, num_bytes);
250 }
251
252 /**
253 * Read a buffer and check its content for a pattern.
254 *
255 * \param fd The file descriptor to receive from.
256 * \param pattern The expected pattern.
257 * \param bufsize The size of the internal buffer.
258 *
259 * This function tries to read at most \a bufsize bytes from the non-blocking
260 * file descriptor \a fd. If at least \p strlen(\a pattern) bytes have been
261 * received, the beginning of the received buffer is compared with \a pattern,
262 * ignoring case.
263 *
264 * \return Positive if \a pattern was received, negative on errors, zero if no data
265 * was available to read.
266 *
267 * \sa \ref read_nonblock(), \sa strncasecmp(3).
268 */
269 int read_pattern(int fd, const char *pattern, size_t bufsize)
270 {
271 size_t n, len;
272 char *buf = alloc(bufsize + 1);
273 int ret = read_nonblock(fd, buf, bufsize, &n);
274
275 buf[n] = '\0';
276 if (ret < 0)
277 goto out;
278 ret = 0;
279 if (n == 0)
280 goto out;
281 ret = -E_READ_PATTERN;
282 len = strlen(pattern);
283 if (n < len)
284 goto out;
285 if (strncasecmp(buf, pattern, len) != 0)
286 goto out;
287 ret = 1;
288 out:
289 if (ret < 0) {
290 PARA_NOTICE_LOG("%s\n", para_strerror(-ret));
291 PARA_NOTICE_LOG("recvd %zu bytes: %s\n", n, buf);
292 }
293 free(buf);
294 return ret;
295 }
296
297 /**
298 * Check whether a file exists.
299 *
300 * \param fn The file name.
301 *
302 * \return True iff file exists.
303 */
304 bool file_exists(const char *fn)
305 {
306 struct stat statbuf;
307
308 return !stat(fn, &statbuf);
309 }
310
311 /**
312 * Set a file descriptor to blocking mode.
313 *
314 * \param fd The file descriptor.
315 *
316 * \return Standard.
317 */
318 __must_check int mark_fd_blocking(int fd)
319 {
320 int flags = fcntl(fd, F_GETFL);
321 if (flags < 0)
322 return -ERRNO_TO_PARA_ERROR(errno);
323 flags = fcntl(fd, F_SETFL, ((long)flags) & ~O_NONBLOCK);
324 if (flags < 0)
325 return -ERRNO_TO_PARA_ERROR(errno);
326 return 1;
327 }
328
329 /**
330 * Set a file descriptor to non-blocking mode.
331 *
332 * \param fd The file descriptor.
333 *
334 * \return Standard.
335 */
336 __must_check int mark_fd_nonblocking(int fd)
337 {
338 int flags = fcntl(fd, F_GETFL);
339 if (flags < 0)
340 return -ERRNO_TO_PARA_ERROR(errno);
341 flags = fcntl(fd, F_SETFL, ((long)flags) | O_NONBLOCK);
342 if (flags < 0)
343 return -ERRNO_TO_PARA_ERROR(errno);
344 return 1;
345 }
346
347 /**
348 * Paraslash's wrapper for mmap.
349 *
350 * \param length Number of bytes to mmap.
351 * \param prot Either PROT_NONE or the bitwise OR of one or more of
352 * PROT_EXEC PROT_READ PROT_WRITE.
353 * \param flags Exactly one of MAP_SHARED and MAP_PRIVATE.
354 * \param fd The file to mmap from.
355 * \param map Result pointer.
356 *
357 * \return Standard.
358 *
359 * \sa mmap(2).
360 */
361 int para_mmap(size_t length, int prot, int flags, int fd, void *map)
362 {
363 void **m = map;
364
365 errno = EINVAL;
366 if (!length)
367 goto err;
368 *m = mmap(NULL, length, prot, flags, fd, (off_t)0);
369 if (*m != MAP_FAILED)
370 return 1;
371 err:
372 *m = NULL;
373 return -ERRNO_TO_PARA_ERROR(errno);
374 }
375
376 /**
377 * Wrapper for the open(2) system call.
378 *
379 * \param path The filename.
380 * \param flags The usual open(2) flags.
381 * \param mode Specifies the permissions to use.
382 *
383 * The mode parameter must be specified when O_CREAT is in the flags, and is
384 * ignored otherwise.
385 *
386 * \return The file descriptor on success, negative on errors.
387 *
388 * \sa open(2).
389 */
390 int para_open(const char *path, int flags, mode_t mode)
391 {
392 int ret = open(path, flags, mode);
393
394 if (ret >= 0)
395 return ret;
396 return -ERRNO_TO_PARA_ERROR(errno);
397 }
398
399 /**
400 * Wrapper for chdir(2).
401 *
402 * \param path The specified directory.
403 *
404 * \return Standard.
405 */
406 int para_chdir(const char *path)
407 {
408 int ret = chdir(path);
409
410 if (ret >= 0)
411 return 1;
412 return -ERRNO_TO_PARA_ERROR(errno);
413 }
414
415 /**
416 * Save the cwd and open a given directory.
417 *
418 * \param dirname Path to the directory to open.
419 * \param dir Result pointer.
420 * \param cwd File descriptor of the current working directory.
421 *
422 * \return Standard.
423 *
424 * Opening the current directory (".") and calling fchdir() to return is
425 * usually faster and more reliable than saving cwd in some buffer and calling
426 * chdir() afterwards.
427 *
428 * If \a cwd is not \p NULL "." is opened and the resulting file descriptor is
429 * stored in \a cwd. If the function returns success, and \a cwd is not \p
430 * NULL, the caller must close this file descriptor (probably after calling
431 * fchdir(*cwd)).
432 *
433 * On errors, the function undos everything, so the caller needs neither close
434 * any files, nor change back to the original working directory.
435 *
436 * \sa getcwd(3).
437 *
438 */
439 static int para_opendir(const char *dirname, DIR **dir, int *cwd)
440 {
441 int ret;
442
443 *dir = NULL;
444 if (cwd) {
445 ret = para_open(".", O_RDONLY, 0);
446 if (ret < 0)
447 return ret;
448 *cwd = ret;
449 }
450 ret = para_chdir(dirname);
451 if (ret < 0)
452 goto close_cwd;
453 *dir = opendir(".");
454 if (*dir)
455 return 1;
456 ret = -ERRNO_TO_PARA_ERROR(errno);
457 /* Ignore return value of fchdir() and close(). We're busted anyway. */
458 if (cwd) {
459 int __a_unused ret2 = fchdir(*cwd); /* STFU, gcc */
460 }
461 close_cwd:
462 if (cwd)
463 close(*cwd);
464 return ret;
465 }
466
467 /**
468 * A wrapper for mkdir(2).
469 *
470 * \param path Name of the directory to create.
471 * \param mode The permissions to use.
472 *
473 * \return Standard.
474 */
475 int para_mkdir(const char *path, mode_t mode)
476 {
477 if (!mkdir(path, mode))
478 return 1;
479 return -ERRNO_TO_PARA_ERROR(errno);
480 }
481
482 /**
483 * Open a file and map it into memory.
484 *
485 * \param path Name of the regular file to map.
486 * \param open_mode Either \p O_RDONLY or \p O_RDWR.
487 * \param map On success, the mapping is returned here.
488 * \param size size of the mapping.
489 * \param fd_ptr The file descriptor of the mapping.
490 *
491 * If \a fd_ptr is \p NULL, the file descriptor resulting from the underlying
492 * open call is closed after mmap(). Otherwise the file is kept open and the
493 * file descriptor is returned in \a fd_ptr.
494 *
495 * \return Standard.
496 *
497 * \sa para_open(), mmap(2).
498 */
499 int mmap_full_file(const char *path, int open_mode, void **map,
500 size_t *size, int *fd_ptr)
501 {
502 int fd, ret, mmap_prot, mmap_flags;
503 struct stat file_status;
504
505 if (open_mode == O_RDONLY) {
506 mmap_prot = PROT_READ;
507 mmap_flags = MAP_PRIVATE;
508 } else {
509 mmap_prot = PROT_READ | PROT_WRITE;
510 mmap_flags = MAP_SHARED;
511 }
512 ret = para_open(path, open_mode, 0);
513 if (ret < 0)
514 return ret;
515 fd = ret;
516 if (fstat(fd, &file_status) < 0) {
517 ret = -ERRNO_TO_PARA_ERROR(errno);
518 goto out;
519 }
520 *size = file_status.st_size;
521 /*
522 * If the file is empty, *size is zero and mmap() would return EINVAL
523 * (Invalid argument). This error is common enough to spend an extra
524 * error code which explicitly states the problem.
525 */
526 ret = -E_EMPTY;
527 if (*size == 0)
528 goto out;
529 /*
530 * If fd refers to a directory, mmap() returns ENODEV (No such device),
531 * at least on Linux. "Is a directory" seems to be more to the point.
532 */
533 ret = -ERRNO_TO_PARA_ERROR(EISDIR);
534 if (S_ISDIR(file_status.st_mode))
535 goto out;
536
537 ret = para_mmap(*size, mmap_prot, mmap_flags, fd, map);
538 out:
539 if (ret < 0 || !fd_ptr)
540 close(fd);
541 else
542 *fd_ptr = fd;
543 return ret;
544 }
545
546 /**
547 * A wrapper for munmap(2).
548 *
549 * \param start The start address of the memory mapping.
550 * \param length The size of the mapping.
551 *
552 * \return Standard.
553 *
554 * \sa munmap(2), \ref mmap_full_file().
555 */
556 int para_munmap(void *start, size_t length)
557 {
558 int err;
559
560 if (!start)
561 return 0;
562 if (munmap(start, length) >= 0)
563 return 1;
564 err = errno;
565 PARA_ERROR_LOG("munmap (%p/%zu) failed: %s\n", start, length,
566 strerror(err));
567 return -ERRNO_TO_PARA_ERROR(err);
568 }
569
570 /**
571 * Simple wrapper for poll(2).
572 *
573 * It calls poll(2) and starts over if the call was interrupted by a signal.
574 *
575 * \param fds See poll(2).
576 * \param nfds See poll(2).
577 * \param timeout See poll(2).
578 *
579 * \return The return value of the underlying poll() call on success, the
580 * negative paraslash error code on errors.
581 *
582 * All arguments are passed verbatim to poll(2).
583 */
584 int xpoll(struct pollfd *fds, nfds_t nfds, int timeout)
585 {
586 int ret;
587
588 do
589 ret = poll(fds, nfds, timeout);
590 while (ret < 0 && errno == EINTR);
591 return ret < 0? -ERRNO_TO_PARA_ERROR(errno) : ret;
592 }
593
594 /**
595 * Check a file descriptor for readability.
596 *
597 * \param fd The file descriptor.
598 *
599 * \return positive if fd is ready for reading, zero if it isn't, negative if
600 * an error occurred.
601 *
602 * \sa \ref write_ok().
603 */
604 int read_ok(int fd)
605 {
606 struct pollfd pfd = {.fd = fd, .events = POLLIN};
607 int ret = xpoll(&pfd, 1, 0);
608 return ret < 0? ret : pfd.revents & POLLIN;
609 }
610
611 /**
612 * Check a file descriptor for writability.
613 *
614 * \param fd The file descriptor.
615 *
616 * \return positive if fd is ready for writing, zero if it isn't, negative if
617 * an error occurred.
618 *
619 * \sa \ref read_ok().
620 */
621 int write_ok(int fd)
622 {
623 struct pollfd pfd = {.fd = fd, .events = POLLOUT};
624 int ret = xpoll(&pfd, 1, 0);
625 return ret < 0? ret : pfd.revents & POLLOUT;
626 }
627
628 /**
629 * Ensure that file descriptors 0, 1, and 2 are valid.
630 *
631 * Common approach that opens /dev/null until it gets a file descriptor greater
632 * than two.
633 */
634 void valid_fd_012(void)
635 {
636 while (1) {
637 int fd = open("/dev/null", O_RDWR);
638 if (fd < 0)
639 exit(EXIT_FAILURE);
640 if (fd > 2) {
641 close(fd);
642 break;
643 }
644 }
645 }
646
647 /**
648 * Traverse the given directory recursively.
649 *
650 * \param dirname The directory to traverse.
651 * \param func The function to call for each entry.
652 * \param private_data Pointer to an arbitrary data structure.
653 *
654 * For each regular file under \a dirname, the supplied function \a func is
655 * called. The full path of the regular file and the \a private_data pointer
656 * are passed to \a func. Directories for which the calling process has no
657 * permissions to change to are silently ignored.
658 *
659 * \return Standard.
660 */
661 int for_each_file_in_dir(const char *dirname,
662 int (*func)(const char *, void *), void *private_data)
663 {
664 DIR *dir;
665 struct dirent *entry;
666 int cwd_fd, ret = para_opendir(dirname, &dir, &cwd_fd);
667
668 if (ret < 0)
669 return ret == -ERRNO_TO_PARA_ERROR(EACCES)? 1 : ret;
670 /* scan cwd recursively */
671 while ((entry = readdir(dir))) {
672 mode_t m;
673 char *tmp;
674 struct stat s;
675
676 if (!strcmp(entry->d_name, "."))
677 continue;
678 if (!strcmp(entry->d_name, ".."))
679 continue;
680 if (lstat(entry->d_name, &s) == -1)
681 continue;
682 m = s.st_mode;
683 if (!S_ISREG(m) && !S_ISDIR(m))
684 continue;
685 tmp = make_message("%s/%s", dirname, entry->d_name);
686 if (!S_ISDIR(m)) {
687 ret = func(tmp, private_data);
688 free(tmp);
689 if (ret < 0)
690 goto out;
691 continue;
692 }
693 /* directory */
694 ret = for_each_file_in_dir(tmp, func, private_data);
695 free(tmp);
696 if (ret < 0)
697 goto out;
698 }
699 ret = 1;
700 out:
701 closedir(dir);
702 if (fchdir(cwd_fd) < 0 && ret >= 0)
703 ret = -ERRNO_TO_PARA_ERROR(errno);
704 close(cwd_fd);
705 return ret;
706 }