2 * Copyright (C) 2006 Andre Noll <maan@tuebingen.mpg.de>
4 * Licensed under the GPL v2. For licencing details see COPYING.
7 /** \file fd.c Helper functions for file descriptor handling. */
10 #include <sys/types.h>
20 * Write an array of buffers to a file descriptor.
22 * \param fd The file descriptor.
23 * \param iov Pointer to one or more buffers.
24 * \param iovcnt The number of buffers.
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.
31 * \return Negative on fatal errors, number of bytes written else.
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
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.
41 * \sa writev(2), \ref xwrite().
43 int xwritev(int fd, struct iovec *iov, int iovcnt)
47 struct iovec saved_iov, *curiov;
52 while (i < iovcnt && curiov->iov_len > 0) {
53 ssize_t ret = writev(fd, curiov, iovcnt - i);
57 if (ret < curiov->iov_len) {
58 curiov->iov_base += ret;
59 curiov->iov_len -= ret;
62 ret -= curiov->iov_len;
74 * The write() call was interrupted by a signal before
75 * any data was written. Try again.
78 if (errno == EAGAIN || errno == EWOULDBLOCK)
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.
86 return -ERRNO_TO_PARA_ERROR(errno);
92 * Write a buffer to a file descriptor, re-writing on short writes.
94 * \param fd The file descriptor.
95 * \param buf The buffer to write.
96 * \param len The number of bytes to write.
98 * This is a simple wrapper for \ref xwritev().
100 * \return The return value of the underlying call to \ref xwritev().
102 int xwrite(int fd, const char *buf, size_t len)
104 struct iovec iov = {.iov_base = (void *)buf, .iov_len = len};
105 return xwritev(fd, &iov, 1);
109 * Write all data to a file descriptor.
111 * \param fd The file descriptor.
112 * \param buf The buffer to be sent.
113 * \param len The length of \a buf.
115 * This is like \ref xwrite() but returns \p -E_SHORT_WRITE if not
116 * all data could be written.
118 * \return Number of bytes written on success, negative error code else.
120 int write_all(int fd, const char *buf, size_t len)
122 int ret = xwrite(fd, buf, len);
127 return -E_SHORT_WRITE;
132 * Write a buffer given by a format string.
134 * \param fd The file descriptor.
135 * \param fmt A format string.
137 * \return The return value of the underlying call to \ref write_all().
139 __printf_2_3 int write_va_buffer(int fd, const char *fmt, ...)
146 ret = xvasprintf(&msg, fmt, ap);
147 ret = write_all(fd, msg, ret);
153 * Read from a non-blocking file descriptor into multiple buffers.
155 * \param fd The file descriptor to read from.
156 * \param iov Scatter/gather array used in readv().
157 * \param iovcnt Number of elements in \a iov.
158 * \param rfds An optional fd set pointer.
159 * \param num_bytes Result pointer. Contains the number of bytes read from \a fd.
161 * If \a rfds is not \p NULL and the (non-blocking) file descriptor \a fd is
162 * not set in \a rfds, this function returns early without doing anything.
163 * Otherwise The function tries to read up to \a sz bytes from \a fd, where \a
164 * sz is the sum of the lengths of all vectors in \a iov. As for xwrite(),
165 * \p EAGAIN is not considered an error condition. However, \p EOF is.
167 * \return Zero or a negative error code. If the underlying call to readv(2)
168 * returned zero (indicating an end of file condition) or failed for some
169 * reason other than \p EAGAIN, a negative error code is returned.
171 * In any case, \a num_bytes contains the number of bytes that have been
172 * successfully read from \a fd (zero if the first readv() call failed with
173 * EAGAIN). Note that even if the function returns negative, some data might
174 * have been read before the error occurred. In this case \a num_bytes is
177 * \sa \ref xwrite(), read(2), readv(2).
179 int readv_nonblock(int fd, struct iovec *iov, int iovcnt, fd_set *rfds,
186 * Avoid a shortcoming of select(): Reads from a non-blocking fd might
187 * return EAGAIN even if FD_ISSET() returns true. However, FD_ISSET()
188 * returning false definitely means that no data can currently be read.
189 * This is the common case, so it is worth to avoid the overhead of the
190 * read() system call in this case.
192 if (rfds && !FD_ISSET(fd, rfds))
195 for (i = 0, j = 0; i < iovcnt;) {
197 /* fix up the first iov */
198 assert(j < iov[i].iov_len);
199 iov[i].iov_base += j;
201 ret = readv(fd, iov + i, iovcnt - i);
202 iov[i].iov_base -= j;
210 return -ERRNO_TO_PARA_ERROR(errno);
214 if (ret < iov[i].iov_len - j) {
218 ret -= iov[i].iov_len - j;
228 * Read from a non-blocking file descriptor into a single buffer.
230 * \param fd The file descriptor to read from.
231 * \param buf The buffer to read data to.
232 * \param sz The size of \a buf.
233 * \param rfds \see \ref readv_nonblock().
234 * \param num_bytes \see \ref readv_nonblock().
236 * This is a simple wrapper for readv_nonblock() which uses an iovec with a single
239 * \return The return value of the underlying call to readv_nonblock().
241 int read_nonblock(int fd, void *buf, size_t sz, fd_set *rfds, size_t *num_bytes)
243 struct iovec iov = {.iov_base = buf, .iov_len = sz};
244 return readv_nonblock(fd, &iov, 1, rfds, num_bytes);
248 * Read a buffer and check its content for a pattern.
250 * \param fd The file descriptor to receive from.
251 * \param pattern The expected pattern.
252 * \param bufsize The size of the internal buffer.
253 * \param rfds Passed to read_nonblock().
255 * This function tries to read at most \a bufsize bytes from the non-blocking
256 * file descriptor \a fd. If at least \p strlen(\a pattern) bytes have been
257 * received, the beginning of the received buffer is compared with \a pattern,
260 * \return Positive if \a pattern was received, negative on errors, zero if no data
261 * was available to read.
263 * \sa \ref read_nonblock(), \sa strncasecmp(3).
265 int read_pattern(int fd, const char *pattern, size_t bufsize, fd_set *rfds)
268 char *buf = para_malloc(bufsize + 1);
269 int ret = read_nonblock(fd, buf, bufsize, rfds, &n);
277 ret = -E_READ_PATTERN;
278 len = strlen(pattern);
281 if (strncasecmp(buf, pattern, len) != 0)
286 PARA_NOTICE_LOG("%s\n", para_strerror(-ret));
287 PARA_NOTICE_LOG("recvd %zu bytes: %s\n", n, buf);
294 * Check whether a file exists.
296 * \param fn The file name.
298 * \return Non-zero iff file exists.
300 int file_exists(const char *fn)
304 return !stat(fn, &statbuf);
308 * Paraslash's wrapper for select(2).
310 * It calls select(2) (with no exceptfds) and starts over if select() was
311 * interrupted by a signal.
313 * \param n The highest-numbered descriptor in any of the two sets, plus 1.
314 * \param readfds fds that should be checked for readability.
315 * \param writefds fds that should be checked for writablility.
316 * \param timeout_tv upper bound on the amount of time elapsed before select()
319 * \return The return value of the underlying select() call on success, the
320 * negative system error code on errors.
322 * All arguments are passed verbatim to select(2).
323 * \sa select(2) select_tut(2).
325 int para_select(int n, fd_set *readfds, fd_set *writefds,
326 struct timeval *timeout_tv)
330 ret = select(n, readfds, writefds, NULL, timeout_tv);
331 while (ret < 0 && errno == EINTR);
333 return -ERRNO_TO_PARA_ERROR(errno);
338 * Set a file descriptor to blocking mode.
340 * \param fd The file descriptor.
344 __must_check int mark_fd_blocking(int fd)
346 int flags = fcntl(fd, F_GETFL);
348 return -ERRNO_TO_PARA_ERROR(errno);
349 flags = fcntl(fd, F_SETFL, ((long)flags) & ~O_NONBLOCK);
351 return -ERRNO_TO_PARA_ERROR(errno);
356 * Set a file descriptor to non-blocking mode.
358 * \param fd The file descriptor.
362 __must_check int mark_fd_nonblocking(int fd)
364 int flags = fcntl(fd, F_GETFL);
366 return -ERRNO_TO_PARA_ERROR(errno);
367 flags = fcntl(fd, F_SETFL, ((long)flags) | O_NONBLOCK);
369 return -ERRNO_TO_PARA_ERROR(errno);
374 * Set a file descriptor in a fd_set.
376 * \param fd The file descriptor to be set.
377 * \param fds The file descriptor set.
378 * \param max_fileno Highest-numbered file descriptor.
380 * This wrapper for FD_SET() passes its first two arguments to \p FD_SET. Upon
381 * return, \a max_fileno contains the maximum of the old_value and \a fd.
385 void para_fd_set(int fd, fd_set *fds, int *max_fileno)
387 assert(fd >= 0 && fd < FD_SETSIZE);
390 int flags = fcntl(fd, F_GETFL);
391 if (!(flags & O_NONBLOCK)) {
392 PARA_EMERG_LOG("fd %d is a blocking file descriptor\n", fd);
398 *max_fileno = PARA_MAX(*max_fileno, fd);
402 * Paraslash's wrapper for fgets(3).
404 * \param line Pointer to the buffer to store the line.
405 * \param size The size of the buffer given by \a line.
406 * \param f The stream to read from.
408 * \return Unlike the standard fgets() function, an integer value
409 * is returned. On success, this function returns 1. On errors, -E_FGETS
410 * is returned. A zero return value indicates an end of file condition.
412 __must_check int para_fgets(char *line, int size, FILE *f)
415 if (fgets(line, size, f))
421 if (errno != EINTR) {
422 PARA_ERROR_LOG("%s\n", strerror(errno));
430 * Paraslash's wrapper for mmap.
432 * \param length Number of bytes to mmap.
433 * \param prot Either PROT_NONE or the bitwise OR of one or more of
434 * PROT_EXEC PROT_READ PROT_WRITE.
435 * \param flags Exactly one of MAP_SHARED and MAP_PRIVATE.
436 * \param fd The file to mmap from.
437 * \param offset Mmap start.
438 * \param map Result pointer.
444 int para_mmap(size_t length, int prot, int flags, int fd, off_t offset,
452 *m = mmap(NULL, length, prot, flags, fd, offset);
453 if (*m != MAP_FAILED)
457 return -ERRNO_TO_PARA_ERROR(errno);
461 * Wrapper for the open(2) system call.
463 * \param path The filename.
464 * \param flags The usual open(2) flags.
465 * \param mode Specifies the permissions to use.
467 * The mode parameter must be specified when O_CREAT is in the flags, and is
470 * \return The file descriptor on success, negative on errors.
474 int para_open(const char *path, int flags, mode_t mode)
476 int ret = open(path, flags, mode);
480 return -ERRNO_TO_PARA_ERROR(errno);
484 * Wrapper for chdir(2).
486 * \param path The specified directory.
490 int para_chdir(const char *path)
492 int ret = chdir(path);
496 return -ERRNO_TO_PARA_ERROR(errno);
500 * Save the cwd and open a given directory.
502 * \param dirname Path to the directory to open.
503 * \param dir Result pointer.
504 * \param cwd File descriptor of the current working directory.
508 * Opening the current directory (".") and calling fchdir() to return is
509 * usually faster and more reliable than saving cwd in some buffer and calling
510 * chdir() afterwards.
512 * If \a cwd is not \p NULL "." is opened and the resulting file descriptor is
513 * stored in \a cwd. If the function returns success, and \a cwd is not \p
514 * NULL, the caller must close this file descriptor (probably after calling
517 * On errors, the function undos everything, so the caller needs neither close
518 * any files, nor change back to the original working directory.
523 static int para_opendir(const char *dirname, DIR **dir, int *cwd)
529 ret = para_open(".", O_RDONLY, 0);
534 ret = para_chdir(dirname);
540 ret = -ERRNO_TO_PARA_ERROR(errno);
541 /* Ignore return value of fchdir() and close(). We're busted anyway. */
543 int __a_unused ret2 = fchdir(*cwd); /* STFU, gcc */
552 * A wrapper for fchdir().
554 * \param fd An open file descriptor.
558 static int para_fchdir(int fd)
561 return -ERRNO_TO_PARA_ERROR(errno);
566 * A wrapper for mkdir(2).
568 * \param path Name of the directory to create.
569 * \param mode The permissions to use.
573 int para_mkdir(const char *path, mode_t mode)
575 if (!mkdir(path, mode))
577 return -ERRNO_TO_PARA_ERROR(errno);
581 * Open a file and map it into memory.
583 * \param path Name of the regular file to map.
584 * \param open_mode Either \p O_RDONLY or \p O_RDWR.
585 * \param map On success, the mapping is returned here.
586 * \param size size of the mapping.
587 * \param fd_ptr The file descriptor of the mapping.
589 * If \a fd_ptr is \p NULL, the file descriptor resulting from the underlying
590 * open call is closed after mmap(). Otherwise the file is kept open and the
591 * file descriptor is returned in \a fd_ptr.
595 * \sa para_open(), mmap(2).
597 int mmap_full_file(const char *path, int open_mode, void **map,
598 size_t *size, int *fd_ptr)
600 int fd, ret, mmap_prot, mmap_flags;
601 struct stat file_status;
603 if (open_mode == O_RDONLY) {
604 mmap_prot = PROT_READ;
605 mmap_flags = MAP_PRIVATE;
607 mmap_prot = PROT_READ | PROT_WRITE;
608 mmap_flags = MAP_SHARED;
610 ret = para_open(path, open_mode, 0);
614 if (fstat(fd, &file_status) < 0) {
615 ret = -ERRNO_TO_PARA_ERROR(errno);
618 *size = file_status.st_size;
620 * If the file is empty, *size is zero and mmap() would return EINVAL
621 * (Invalid argument). This error is common enough to spend an extra
622 * error code which explicitly states the problem.
628 * If fd refers to a directory, mmap() returns ENODEV (No such device),
629 * at least on Linux. "Is a directory" seems to be more to the point.
631 ret = -ERRNO_TO_PARA_ERROR(EISDIR);
632 if (S_ISDIR(file_status.st_mode))
635 ret = para_mmap(*size, mmap_prot, mmap_flags, fd, 0, map);
637 if (ret < 0 || !fd_ptr)
645 * A wrapper for munmap(2).
647 * \param start The start address of the memory mapping.
648 * \param length The size of the mapping.
652 * \sa munmap(2), mmap_full_file().
654 int para_munmap(void *start, size_t length)
660 if (munmap(start, length) >= 0)
663 PARA_ERROR_LOG("munmap (%p/%zu) failed: %s\n", start, length,
665 return -ERRNO_TO_PARA_ERROR(err);
669 * Check a file descriptor for writability.
671 * \param fd The file descriptor.
673 * \return positive if fd is ready for writing, zero if it isn't, negative if
686 return para_select(fd + 1, NULL, &wfds, &tv);
690 * Ensure that file descriptors 0, 1, and 2 are valid.
692 * Common approach that opens /dev/null until it gets a file descriptor greater
695 * \sa okir's Black Hats Manual.
697 void valid_fd_012(void)
700 int fd = open("/dev/null", O_RDWR);
711 * Traverse the given directory recursively.
713 * \param dirname The directory to traverse.
714 * \param func The function to call for each entry.
715 * \param private_data Pointer to an arbitrary data structure.
717 * For each regular file under \a dirname, the supplied function \a func is
718 * called. The full path of the regular file and the \a private_data pointer
719 * are passed to \a func. Directories for which the calling process has no
720 * permissions to change to are silently ignored.
724 int for_each_file_in_dir(const char *dirname,
725 int (*func)(const char *, void *), void *private_data)
728 struct dirent *entry;
729 int cwd_fd, ret2, ret = para_opendir(dirname, &dir, &cwd_fd);
732 return ret == -ERRNO_TO_PARA_ERROR(EACCES)? 1 : ret;
733 /* scan cwd recursively */
734 while ((entry = readdir(dir))) {
739 if (!strcmp(entry->d_name, "."))
741 if (!strcmp(entry->d_name, ".."))
743 if (lstat(entry->d_name, &s) == -1)
746 if (!S_ISREG(m) && !S_ISDIR(m))
748 tmp = make_message("%s/%s", dirname, entry->d_name);
750 ret = func(tmp, private_data);
757 ret = for_each_file_in_dir(tmp, func, private_data);
765 ret2 = para_fchdir(cwd_fd);
766 if (ret2 < 0 && ret >= 0)