2 * Copyright (C) 2006-2010 Andre Noll <maan@systemlinux.org>
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>
14 #include <sys/select.h>
22 * Write a buffer to a file descriptor, re-write on short writes.
24 * \param fd The file descriptor.
25 * \param buf The buffer to be sent.
26 * \param len The length of \a buf.
28 * \return Standard. In any case, the number of bytes that have been written is
31 int write_all(int fd, const char *buf, size_t *len)
37 while (*len < total) {
38 int ret = write(fd, buf + *len, total - *len);
40 return -ERRNO_TO_PARA_ERROR(errno);
47 * Write a buffer to a non-blocking file descriptor.
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.
54 * If \a max_bytes_per_write is non-zero, do not send more than that many bytes
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.
62 * \return Negative on errors, number of bytes written else.
64 int write_nonblock(int fd, const char *buf, size_t len,
65 size_t max_bytes_per_write)
70 while (written < len) {
71 size_t num = len - written;
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)
79 return -ERRNO_TO_PARA_ERROR(errno);
86 * Simple wrapper for readv().
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.
92 * \return A negative error code on errors, the return value of the underlying
93 * call to readv() otherwise.
97 int para_readv(int fd, struct iovec *iov, int iovcnt)
99 int ret = readv(fd, iov, iovcnt);
102 return -ERRNO_TO_PARA_ERROR(errno);
107 * Check whether a file exists.
109 * \param fn The file name.
111 * \return Non-zero iff file exists.
113 int file_exists(const char *fn)
117 return !stat(fn, &statbuf);
121 * Paraslash's wrapper for select(2).
123 * It calls select(2) (with no exceptfds) and starts over if select() was
124 * interrupted by a signal.
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()
132 * \return The return value of the underlying select() call on success, the
133 * negative system error code on errors.
135 * All arguments are passed verbatim to select(2).
136 * \sa select(2) select_tut(2).
138 int para_select(int n, fd_set *readfds, fd_set *writefds,
139 struct timeval *timeout_tv)
143 ret = select(n, readfds, writefds, NULL, timeout_tv);
144 while (ret < 0 && errno == EINTR);
146 return -ERRNO_TO_PARA_ERROR(errno);
151 * Set a file descriptor to blocking mode.
153 * \param fd The file descriptor.
157 __must_check int mark_fd_blocking(int fd)
159 int flags = fcntl(fd, F_GETFL);
161 return -ERRNO_TO_PARA_ERROR(errno);
162 flags = fcntl(fd, F_SETFL, ((long)flags) & ~O_NONBLOCK);
164 return -ERRNO_TO_PARA_ERROR(errno);
169 * Set a file descriptor to non-blocking mode.
171 * \param fd The file descriptor.
175 __must_check int mark_fd_nonblocking(int fd)
177 int flags = fcntl(fd, F_GETFL);
179 return -ERRNO_TO_PARA_ERROR(errno);
180 flags = fcntl(fd, F_SETFL, ((long)flags) | O_NONBLOCK);
182 return -ERRNO_TO_PARA_ERROR(errno);
187 * Set a file descriptor in a fd_set.
189 * \param fd The file descriptor to be set.
190 * \param fds The file descriptor set.
191 * \param max_fileno Highest-numbered file descriptor.
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.
198 void para_fd_set(int fd, fd_set *fds, int *max_fileno)
200 assert(fd >= 0 && fd < FD_SETSIZE);
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);
211 *max_fileno = PARA_MAX(*max_fileno, fd);
215 * Paraslash's wrapper for fgets(3).
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.
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.
225 __must_check int para_fgets(char *line, int size, FILE *f)
228 if (fgets(line, size, f))
234 if (errno != EINTR) {
235 PARA_ERROR_LOG("%s\n", strerror(errno));
243 * Paraslash's wrapper for mmap.
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.
257 int para_mmap(size_t length, int prot, int flags, int fd, off_t offset,
265 *m = mmap(NULL, length, prot, flags, fd, offset);
266 if (*m != MAP_FAILED)
270 return -ERRNO_TO_PARA_ERROR(errno);
274 * Wrapper for the open(2) system call.
276 * \param path The filename.
277 * \param flags The usual open(2) flags.
278 * \param mode Specifies the permissions to use.
280 * The mode parameter must be specified when O_CREAT is in the flags, and is
283 * \return The file descriptor on success, negative on errors.
287 int para_open(const char *path, int flags, mode_t mode)
289 int ret = open(path, flags, mode);
293 return -ERRNO_TO_PARA_ERROR(errno);
297 * Wrapper for chdir(2).
299 * \param path The specified directory.
303 int para_chdir(const char *path)
305 int ret = chdir(path);
309 return -ERRNO_TO_PARA_ERROR(errno);
313 * Save the cwd and open a given directory.
315 * \param dirname Path to the directory to open.
316 * \param dir Result pointer.
317 * \param cwd File descriptor of the current working directory.
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.
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
330 * On errors, the function undos everything, so the caller needs neither close
331 * any files, nor change back to the original working directory.
336 int para_opendir(const char *dirname, DIR **dir, int *cwd)
341 ret = para_open(".", O_RDONLY, 0);
346 ret = para_chdir(dirname);
352 ret = -ERRNO_TO_PARA_ERROR(errno);
353 /* Ignore return value of fchdir() and close(). We're busted anyway. */
355 int __a_unused ret2 = fchdir(*cwd); /* STFU, gcc */
364 * A wrapper for fchdir().
366 * \param fd An open file descriptor.
370 int para_fchdir(int fd)
373 return -ERRNO_TO_PARA_ERROR(errno);
378 * A wrapper for mkdir(2).
380 * \param path Name of the directory to create.
381 * \param mode The permissions to use.
385 int para_mkdir(const char *path, mode_t mode)
387 if (!mkdir(path, mode))
389 return -ERRNO_TO_PARA_ERROR(errno);
393 * Open a file and map it into memory.
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.
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.
407 * \sa para_open(), mmap(2).
409 int mmap_full_file(const char *path, int open_mode, void **map,
410 size_t *size, int *fd_ptr)
412 int fd, ret, mmap_prot, mmap_flags;
413 struct stat file_status;
415 if (open_mode == O_RDONLY) {
416 mmap_prot = PROT_READ;
417 mmap_flags = MAP_PRIVATE;
419 mmap_prot = PROT_READ | PROT_WRITE;
420 mmap_flags = MAP_SHARED;
422 ret = para_open(path, open_mode, 0);
426 if (fstat(fd, &file_status) < 0) {
427 ret = -ERRNO_TO_PARA_ERROR(errno);
430 *size = file_status.st_size;
431 ret = para_mmap(*size, mmap_prot, mmap_flags, fd, 0, map);
433 if (ret < 0 || !fd_ptr)
441 * A wrapper for munmap(2).
443 * \param start The start address of the memory mapping.
444 * \param length The size of the mapping.
448 * \sa munmap(2), mmap_full_file().
450 int para_munmap(void *start, size_t length)
453 if (munmap(start, length) >= 0)
456 PARA_ERROR_LOG("munmap (%p/%zu) failed: %s\n", start, length,
458 return -ERRNO_TO_PARA_ERROR(err);
462 * Check a file descriptor for writability.
464 * \param fd The file descriptor.
466 * \return positive if fd is ready for writing, zero if it isn't, negative if
479 return para_select(fd + 1, NULL, &wfds, &tv);
483 * Ensure that file descriptors 0, 1, and 2 are valid.
485 * Common approach that opens /dev/null until it gets a file descriptor greater
488 * \sa okir's Black Hats Manual.
490 void valid_fd_012(void)
493 int fd = open("/dev/null", O_RDWR);
504 * Traverse the given directory recursively.
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.
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.
517 int for_each_file_in_dir(const char *dirname,
518 int (*func)(const char *, void *), void *private_data)
521 struct dirent *entry;
522 int cwd_fd, ret2, ret = para_opendir(dirname, &dir, &cwd_fd);
525 return ret == -ERRNO_TO_PARA_ERROR(EACCES)? 1 : ret;
526 /* scan cwd recursively */
527 while ((entry = readdir(dir))) {
532 if (!strcmp(entry->d_name, "."))
534 if (!strcmp(entry->d_name, ".."))
536 if (lstat(entry->d_name, &s) == -1)
539 if (!S_ISREG(m) && !S_ISDIR(m))
541 tmp = make_message("%s/%s", dirname, entry->d_name);
543 ret = func(tmp, private_data);
550 ret = for_each_file_in_dir(tmp, func, private_data);
558 ret2 = para_fchdir(cwd_fd);
559 if (ret2 < 0 && ret >= 0)