2 * Copyright (C) 2006-2011 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>
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.
53 * EAGAIN is not considered an error condition. For example CCID3 has a
54 * sending wait queue which fills up and is emptied asynchronously. The EAGAIN
55 * case means that there is currently no space in the wait queue, but this can
56 * change at any moment.
58 * \return Negative on errors, number of bytes written else.
60 int write_nonblock(int fd
, const char *buf
, size_t len
)
65 while (written
< len
) {
66 size_t num
= len
- written
;
68 ret
= write(fd
, buf
+ written
, num
);
69 if (ret
< 0 && errno
== EAGAIN
)
72 return -ERRNO_TO_PARA_ERROR(errno
);
79 * Read from a non-blocking file descriptor into multiple buffers.
81 * \param fd The file descriptor to read from.
82 * \param iov Scatter/gather array used in readv().
83 * \param iovcnt Number of elements in \a iov.
84 * \param rfds An optional fd set pointer.
85 * \param num_bytes Result pointer. Contains the number of bytes read from \a fd.
87 * If \a rfds is not \p NULL and the (non-blocking) file descriptor \a fd is
88 * not set in \a rfds, this function returns early without doing anything.
89 * Otherwise The function tries to read up to \a sz bytes from \a fd. As for
90 * write_nonblock(), EAGAIN is not considered an error condition. However, EOF
93 * \return Zero or a negative error code. If the underlying call to readv(2)
94 * returned zero (indicating an end of file condition) or failed for some
95 * reason other than \p EAGAIN, a negative return value is returned.
97 * In any case, \a num_bytes contains the number of bytes that have been
98 * successfully read from \a fd (zero if the first readv() call failed with
99 * EAGAIN). Note that even if the function returns negative, some data might
100 * have been read before the error occurred. In this case \a num_bytes is
103 * \sa \ref write_nonblock(), read(2), readv(2).
105 int readv_nonblock(int fd
, struct iovec
*iov
, int iovcnt
, fd_set
*rfds
,
112 * Avoid a shortcoming of select(): Reads from a non-blocking fd might
113 * return EAGAIN even if FD_ISSET() returns true. However, FD_ISSET()
114 * returning false definitely means that no data can currently be read.
115 * This is the common case, so it is worth to avoid the overhead of the
116 * read() system call in this case.
118 if (rfds
&& !FD_ISSET(fd
, rfds
))
121 for (i
= 0, j
= 0; i
< iovcnt
;) {
123 /* fix up the first iov */
124 assert(j
< iov
[i
].iov_len
);
125 iov
[i
].iov_base
+= j
;
127 ret
= readv(fd
, iov
+ i
, iovcnt
- i
);
128 iov
[i
].iov_base
-= j
;
136 return -ERRNO_TO_PARA_ERROR(errno
);
140 if (ret
< iov
[i
].iov_len
- j
) {
144 ret
-= iov
[i
].iov_len
- j
;
154 * Read from a non-blocking file descriptor into a single buffer.
156 * \param fd The file descriptor to read from.
157 * \param buf The buffer to read data to.
158 * \param sz The size of \a buf.
159 * \param rfds \see \ref readv_nonblock().
160 * \param num_bytes \see \ref readv_nonblock().
162 * This is a simple wrapper for readv_nonblock() which uses an iovec with a single
165 * \return The return value of the underlying call to readv_nonblock().
167 int read_nonblock(int fd
, void *buf
, size_t sz
, fd_set
*rfds
, size_t *num_bytes
)
169 struct iovec iov
= {.iov_base
= buf
, .iov_len
= sz
};
170 return readv_nonblock(fd
, &iov
, 1, rfds
, num_bytes
);
174 * Read a buffer and check its content for a pattern.
176 * \param fd The file descriptor to receive from.
177 * \param pattern The expected pattern.
178 * \param bufsize The size of the internal buffer.
179 * \param rfds Passed to read_nonblock().
181 * This function tries to read at most \a bufsize bytes from the non-blocking
182 * file descriptor \a fd. If at least \p strlen(\a pattern) bytes have been
183 * received, the beginning of the received buffer is compared with \a pattern,
186 * \return Positive if \a pattern was received, negative on errors, zero if no data
187 * was available to read.
189 * \sa \ref read_nonblock(), \sa strncasecmp(3).
191 int read_pattern(int fd
, const char *pattern
, size_t bufsize
, fd_set
*rfds
)
194 char *buf
= para_malloc(bufsize
+ 1);
195 int ret
= read_nonblock(fd
, buf
, bufsize
, rfds
, &n
);
203 ret
= -E_READ_PATTERN
;
204 len
= strlen(pattern
);
207 if (strncasecmp(buf
, pattern
, len
) != 0)
212 PARA_NOTICE_LOG("%s\n", para_strerror(-ret
));
213 PARA_NOTICE_LOG("recvd %zu bytes: %s\n", n
, buf
);
220 * Check whether a file exists.
222 * \param fn The file name.
224 * \return Non-zero iff file exists.
226 int file_exists(const char *fn
)
230 return !stat(fn
, &statbuf
);
234 * Paraslash's wrapper for select(2).
236 * It calls select(2) (with no exceptfds) and starts over if select() was
237 * interrupted by a signal.
239 * \param n The highest-numbered descriptor in any of the two sets, plus 1.
240 * \param readfds fds that should be checked for readability.
241 * \param writefds fds that should be checked for writablility.
242 * \param timeout_tv upper bound on the amount of time elapsed before select()
245 * \return The return value of the underlying select() call on success, the
246 * negative system error code on errors.
248 * All arguments are passed verbatim to select(2).
249 * \sa select(2) select_tut(2).
251 int para_select(int n
, fd_set
*readfds
, fd_set
*writefds
,
252 struct timeval
*timeout_tv
)
256 ret
= select(n
, readfds
, writefds
, NULL
, timeout_tv
);
257 while (ret
< 0 && errno
== EINTR
);
259 return -ERRNO_TO_PARA_ERROR(errno
);
264 * Set a file descriptor to blocking mode.
266 * \param fd The file descriptor.
270 __must_check
int mark_fd_blocking(int fd
)
272 int flags
= fcntl(fd
, F_GETFL
);
274 return -ERRNO_TO_PARA_ERROR(errno
);
275 flags
= fcntl(fd
, F_SETFL
, ((long)flags
) & ~O_NONBLOCK
);
277 return -ERRNO_TO_PARA_ERROR(errno
);
282 * Set a file descriptor to non-blocking mode.
284 * \param fd The file descriptor.
288 __must_check
int mark_fd_nonblocking(int fd
)
290 int flags
= fcntl(fd
, F_GETFL
);
292 return -ERRNO_TO_PARA_ERROR(errno
);
293 flags
= fcntl(fd
, F_SETFL
, ((long)flags
) | O_NONBLOCK
);
295 return -ERRNO_TO_PARA_ERROR(errno
);
300 * Set a file descriptor in a fd_set.
302 * \param fd The file descriptor to be set.
303 * \param fds The file descriptor set.
304 * \param max_fileno Highest-numbered file descriptor.
306 * This wrapper for FD_SET() passes its first two arguments to \p FD_SET. Upon
307 * return, \a max_fileno contains the maximum of the old_value and \a fd.
311 void para_fd_set(int fd
, fd_set
*fds
, int *max_fileno
)
313 assert(fd
>= 0 && fd
< FD_SETSIZE
);
316 int flags
= fcntl(fd
, F_GETFL
);
317 if (!(flags
& O_NONBLOCK
)) {
318 PARA_EMERG_LOG("fd %d is a blocking file descriptor\n", fd
);
324 *max_fileno
= PARA_MAX(*max_fileno
, fd
);
328 * Paraslash's wrapper for fgets(3).
330 * \param line Pointer to the buffer to store the line.
331 * \param size The size of the buffer given by \a line.
332 * \param f The stream to read from.
334 * \return Unlike the standard fgets() function, an integer value
335 * is returned. On success, this function returns 1. On errors, -E_FGETS
336 * is returned. A zero return value indicates an end of file condition.
338 __must_check
int para_fgets(char *line
, int size
, FILE *f
)
341 if (fgets(line
, size
, f
))
347 if (errno
!= EINTR
) {
348 PARA_ERROR_LOG("%s\n", strerror(errno
));
356 * Paraslash's wrapper for mmap.
358 * \param length Number of bytes to mmap.
359 * \param prot Either PROT_NONE or the bitwise OR of one or more of
360 * PROT_EXEC PROT_READ PROT_WRITE.
361 * \param flags Exactly one of MAP_SHARED and MAP_PRIVATE.
362 * \param fd The file to mmap from.
363 * \param offset Mmap start.
364 * \param map Result pointer.
370 int para_mmap(size_t length
, int prot
, int flags
, int fd
, off_t offset
,
378 *m
= mmap(NULL
, length
, prot
, flags
, fd
, offset
);
379 if (*m
!= MAP_FAILED
)
383 return -ERRNO_TO_PARA_ERROR(errno
);
387 * Wrapper for the open(2) system call.
389 * \param path The filename.
390 * \param flags The usual open(2) flags.
391 * \param mode Specifies the permissions to use.
393 * The mode parameter must be specified when O_CREAT is in the flags, and is
396 * \return The file descriptor on success, negative on errors.
400 int para_open(const char *path
, int flags
, mode_t mode
)
402 int ret
= open(path
, flags
, mode
);
406 return -ERRNO_TO_PARA_ERROR(errno
);
410 * Wrapper for chdir(2).
412 * \param path The specified directory.
416 int para_chdir(const char *path
)
418 int ret
= chdir(path
);
422 return -ERRNO_TO_PARA_ERROR(errno
);
426 * Save the cwd and open a given directory.
428 * \param dirname Path to the directory to open.
429 * \param dir Result pointer.
430 * \param cwd File descriptor of the current working directory.
434 * Opening the current directory (".") and calling fchdir() to return is
435 * usually faster and more reliable than saving cwd in some buffer and calling
436 * chdir() afterwards.
438 * If \a cwd is not \p NULL "." is opened and the resulting file descriptor is
439 * stored in \a cwd. If the function returns success, and \a cwd is not \p
440 * NULL, the caller must close this file descriptor (probably after calling
443 * On errors, the function undos everything, so the caller needs neither close
444 * any files, nor change back to the original working directory.
449 static int para_opendir(const char *dirname
, DIR **dir
, int *cwd
)
454 ret
= para_open(".", O_RDONLY
, 0);
459 ret
= para_chdir(dirname
);
465 ret
= -ERRNO_TO_PARA_ERROR(errno
);
466 /* Ignore return value of fchdir() and close(). We're busted anyway. */
468 int __a_unused ret2
= fchdir(*cwd
); /* STFU, gcc */
477 * A wrapper for fchdir().
479 * \param fd An open file descriptor.
483 static int para_fchdir(int fd
)
486 return -ERRNO_TO_PARA_ERROR(errno
);
491 * A wrapper for mkdir(2).
493 * \param path Name of the directory to create.
494 * \param mode The permissions to use.
498 int para_mkdir(const char *path
, mode_t mode
)
500 if (!mkdir(path
, mode
))
502 return -ERRNO_TO_PARA_ERROR(errno
);
506 * Open a file and map it into memory.
508 * \param path Name of the regular file to map.
509 * \param open_mode Either \p O_RDONLY or \p O_RDWR.
510 * \param map On success, the mapping is returned here.
511 * \param size size of the mapping.
512 * \param fd_ptr The file descriptor of the mapping.
514 * If \a fd_ptr is \p NULL, the file descriptor resulting from the underlying
515 * open call is closed after mmap(). Otherwise the file is kept open and the
516 * file descriptor is returned in \a fd_ptr.
520 * \sa para_open(), mmap(2).
522 int mmap_full_file(const char *path
, int open_mode
, void **map
,
523 size_t *size
, int *fd_ptr
)
525 int fd
, ret
, mmap_prot
, mmap_flags
;
526 struct stat file_status
;
528 if (open_mode
== O_RDONLY
) {
529 mmap_prot
= PROT_READ
;
530 mmap_flags
= MAP_PRIVATE
;
532 mmap_prot
= PROT_READ
| PROT_WRITE
;
533 mmap_flags
= MAP_SHARED
;
535 ret
= para_open(path
, open_mode
, 0);
539 if (fstat(fd
, &file_status
) < 0) {
540 ret
= -ERRNO_TO_PARA_ERROR(errno
);
543 *size
= file_status
.st_size
;
544 ret
= para_mmap(*size
, mmap_prot
, mmap_flags
, fd
, 0, map
);
546 if (ret
< 0 || !fd_ptr
)
554 * A wrapper for munmap(2).
556 * \param start The start address of the memory mapping.
557 * \param length The size of the mapping.
561 * \sa munmap(2), mmap_full_file().
563 int para_munmap(void *start
, size_t length
)
569 if (munmap(start
, length
) >= 0)
572 PARA_ERROR_LOG("munmap (%p/%zu) failed: %s\n", start
, length
,
574 return -ERRNO_TO_PARA_ERROR(err
);
578 * Check a file descriptor for writability.
580 * \param fd The file descriptor.
582 * \return positive if fd is ready for writing, zero if it isn't, negative if
595 return para_select(fd
+ 1, NULL
, &wfds
, &tv
);
599 * Ensure that file descriptors 0, 1, and 2 are valid.
601 * Common approach that opens /dev/null until it gets a file descriptor greater
604 * \sa okir's Black Hats Manual.
606 void valid_fd_012(void)
609 int fd
= open("/dev/null", O_RDWR
);
620 * Traverse the given directory recursively.
622 * \param dirname The directory to traverse.
623 * \param func The function to call for each entry.
624 * \param private_data Pointer to an arbitrary data structure.
626 * For each regular file under \a dirname, the supplied function \a func is
627 * called. The full path of the regular file and the \a private_data pointer
628 * are passed to \a func. Directories for which the calling process has no
629 * permissions to change to are silently ignored.
633 int for_each_file_in_dir(const char *dirname
,
634 int (*func
)(const char *, void *), void *private_data
)
637 struct dirent
*entry
;
638 int cwd_fd
, ret2
, ret
= para_opendir(dirname
, &dir
, &cwd_fd
);
641 return ret
== -ERRNO_TO_PARA_ERROR(EACCES
)? 1 : ret
;
642 /* scan cwd recursively */
643 while ((entry
= readdir(dir
))) {
648 if (!strcmp(entry
->d_name
, "."))
650 if (!strcmp(entry
->d_name
, ".."))
652 if (lstat(entry
->d_name
, &s
) == -1)
655 if (!S_ISREG(m
) && !S_ISDIR(m
))
657 tmp
= make_message("%s/%s", dirname
, entry
->d_name
);
659 ret
= func(tmp
, private_data
);
666 ret
= for_each_file_in_dir(tmp
, func
, private_data
);
674 ret2
= para_fchdir(cwd_fd
);
675 if (ret2
< 0 && ret
>= 0)