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>
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 * Read from a non-blocking file descriptor into multiple buffers.
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.
91 * \param rfds An optional fd set pointer.
92 * \param num_bytes Result pointer. Contains the number of bytes read from \a fd.
94 * If \a rfds is not \p NULL and the (non-blocking) file descriptor \a fd is
95 * not set in \a rfds, this function returns early without doing anything.
96 * Otherwise The function tries to read up to \a sz bytes from \a fd. As for
97 * write_nonblock(), EAGAIN is not considered an error condition. However, EOF
100 * \return Zero or a negative error code. If the underlying call to readv(2)
101 * returned zero (indicating an end of file condition) or failed for some
102 * reason other than \p EAGAIN, a negative return value is returned.
104 * In any case, \a num_bytes contains the number of bytes that have been
105 * successfully read from \a fd (zero if the first readv() call failed with
106 * EAGAIN). Note that even if the function returns negative, some data might
107 * have been read before the error occured. In this case \a num_bytes is
110 * \sa \ref write_nonblock(), read(2), readv(2).
112 int readv_nonblock(int fd
, struct iovec
*iov
, int iovcnt
, fd_set
*rfds
,
119 * Avoid a shortcoming of select(): Reads from a non-blocking fd might
120 * return EAGAIN even if FD_ISSET() returns true. However, FD_ISSET()
121 * returning false definitely means that no data can currently be read.
122 * This is the common case, so it is worth to avoid the overhead of the
123 * read() system call in this case.
125 if (rfds
&& !FD_ISSET(fd
, rfds
))
128 for (i
= 0, j
= 0; i
< iovcnt
;) {
130 /* fix up the first iov */
131 assert(j
< iov
[i
].iov_len
);
132 iov
[i
].iov_base
+= j
;
134 ret
= readv(fd
, iov
+ i
, iovcnt
- i
);
135 iov
[i
].iov_base
-= j
;
143 return -ERRNO_TO_PARA_ERROR(errno
);
147 if (ret
< iov
[i
].iov_len
- j
) {
151 ret
-= iov
[i
].iov_len
- j
;
161 * Read from a non-blocking file descriptor into a single buffer.
163 * \param fd The file descriptor to read from.
164 * \param buf The buffer to read data to.
165 * \param sz The size of \a buf.
166 * \param rfds \see \ref readv_nonblock().
167 * \param num_bytes \see \ref readv_nonblock().
169 * This is a simple wrapper for readv_nonblock() which uses an iovec with a single
172 * \return The return value of the underlying call to readv_nonblock().
174 int read_nonblock(int fd
, void *buf
, size_t sz
, fd_set
*rfds
, size_t *num_bytes
)
176 struct iovec iov
= {.iov_base
= buf
, .iov_len
= sz
};
177 return readv_nonblock(fd
, &iov
, 1, rfds
, num_bytes
);
181 * Read a buffer and check its content for a pattern.
183 * \param fd The file descriptor to receive from.
184 * \param pattern The expected pattern.
185 * \param bufsize The size of the internal buffer.
186 * \param rfds Passed to read_nonblock().
188 * This function tries to read at most \a bufsize bytes from the non-blocking
189 * file descriptor \a fd. If at least \p strlen(\a pattern) bytes have been
190 * received, the beginning of the received buffer is compared with \a pattern,
193 * \return Positive if \a pattern was received, negative on errors, zero if no data
194 * was available to read.
196 * \sa \ref read_nonblock(), \sa strncasecmp(3).
198 int read_pattern(int fd
, const char *pattern
, size_t bufsize
, fd_set
*rfds
)
201 char *buf
= para_malloc(bufsize
+ 1);
202 int ret
= read_nonblock(fd
, buf
, bufsize
, rfds
, &n
);
210 ret
= -E_READ_PATTERN
;
211 len
= strlen(pattern
);
214 if (strncasecmp(buf
, pattern
, len
) != 0)
219 PARA_NOTICE_LOG("%s\n", para_strerror(-ret
));
220 PARA_NOTICE_LOG("recvd %zu bytes: %s\n", n
, buf
);
227 * Check whether a file exists.
229 * \param fn The file name.
231 * \return Non-zero iff file exists.
233 int file_exists(const char *fn
)
237 return !stat(fn
, &statbuf
);
241 * Paraslash's wrapper for select(2).
243 * It calls select(2) (with no exceptfds) and starts over if select() was
244 * interrupted by a signal.
246 * \param n The highest-numbered descriptor in any of the two sets, plus 1.
247 * \param readfds fds that should be checked for readability.
248 * \param writefds fds that should be checked for writablility.
249 * \param timeout_tv upper bound on the amount of time elapsed before select()
252 * \return The return value of the underlying select() call on success, the
253 * negative system error code on errors.
255 * All arguments are passed verbatim to select(2).
256 * \sa select(2) select_tut(2).
258 int para_select(int n
, fd_set
*readfds
, fd_set
*writefds
,
259 struct timeval
*timeout_tv
)
263 ret
= select(n
, readfds
, writefds
, NULL
, timeout_tv
);
264 while (ret
< 0 && errno
== EINTR
);
266 return -ERRNO_TO_PARA_ERROR(errno
);
271 * Set a file descriptor to blocking mode.
273 * \param fd The file descriptor.
277 __must_check
int mark_fd_blocking(int fd
)
279 int flags
= fcntl(fd
, F_GETFL
);
281 return -ERRNO_TO_PARA_ERROR(errno
);
282 flags
= fcntl(fd
, F_SETFL
, ((long)flags
) & ~O_NONBLOCK
);
284 return -ERRNO_TO_PARA_ERROR(errno
);
289 * Set a file descriptor to non-blocking mode.
291 * \param fd The file descriptor.
295 __must_check
int mark_fd_nonblocking(int fd
)
297 int flags
= fcntl(fd
, F_GETFL
);
299 return -ERRNO_TO_PARA_ERROR(errno
);
300 flags
= fcntl(fd
, F_SETFL
, ((long)flags
) | O_NONBLOCK
);
302 return -ERRNO_TO_PARA_ERROR(errno
);
307 * Set a file descriptor in a fd_set.
309 * \param fd The file descriptor to be set.
310 * \param fds The file descriptor set.
311 * \param max_fileno Highest-numbered file descriptor.
313 * This wrapper for FD_SET() passes its first two arguments to \p FD_SET. Upon
314 * return, \a max_fileno contains the maximum of the old_value and \a fd.
318 void para_fd_set(int fd
, fd_set
*fds
, int *max_fileno
)
320 assert(fd
>= 0 && fd
< FD_SETSIZE
);
323 int flags
= fcntl(fd
, F_GETFL
);
324 if (!(flags
& O_NONBLOCK
)) {
325 PARA_EMERG_LOG("fd %d is a blocking file descriptor\n", fd
);
331 *max_fileno
= PARA_MAX(*max_fileno
, fd
);
335 * Paraslash's wrapper for fgets(3).
337 * \param line Pointer to the buffer to store the line.
338 * \param size The size of the buffer given by \a line.
339 * \param f The stream to read from.
341 * \return Unlike the standard fgets() function, an integer value
342 * is returned. On success, this function returns 1. On errors, -E_FGETS
343 * is returned. A zero return value indicates an end of file condition.
345 __must_check
int para_fgets(char *line
, int size
, FILE *f
)
348 if (fgets(line
, size
, f
))
354 if (errno
!= EINTR
) {
355 PARA_ERROR_LOG("%s\n", strerror(errno
));
363 * Paraslash's wrapper for mmap.
365 * \param length Number of bytes to mmap.
366 * \param prot Either PROT_NONE or the bitwise OR of one or more of
367 * PROT_EXEC PROT_READ PROT_WRITE.
368 * \param flags Exactly one of MAP_SHARED and MAP_PRIVATE.
369 * \param fd The file to mmap from.
370 * \param offset Mmap start.
371 * \param map Result pointer.
377 int para_mmap(size_t length
, int prot
, int flags
, int fd
, off_t offset
,
385 *m
= mmap(NULL
, length
, prot
, flags
, fd
, offset
);
386 if (*m
!= MAP_FAILED
)
390 return -ERRNO_TO_PARA_ERROR(errno
);
394 * Wrapper for the open(2) system call.
396 * \param path The filename.
397 * \param flags The usual open(2) flags.
398 * \param mode Specifies the permissions to use.
400 * The mode parameter must be specified when O_CREAT is in the flags, and is
403 * \return The file descriptor on success, negative on errors.
407 int para_open(const char *path
, int flags
, mode_t mode
)
409 int ret
= open(path
, flags
, mode
);
413 return -ERRNO_TO_PARA_ERROR(errno
);
417 * Wrapper for chdir(2).
419 * \param path The specified directory.
423 int para_chdir(const char *path
)
425 int ret
= chdir(path
);
429 return -ERRNO_TO_PARA_ERROR(errno
);
433 * Save the cwd and open a given directory.
435 * \param dirname Path to the directory to open.
436 * \param dir Result pointer.
437 * \param cwd File descriptor of the current working directory.
441 * Opening the current directory (".") and calling fchdir() to return is
442 * usually faster and more reliable than saving cwd in some buffer and calling
443 * chdir() afterwards.
445 * If \a cwd is not \p NULL "." is opened and the resulting file descriptor is
446 * stored in \a cwd. If the function returns success, and \a cwd is not \p
447 * NULL, the caller must close this file descriptor (probably after calling
450 * On errors, the function undos everything, so the caller needs neither close
451 * any files, nor change back to the original working directory.
456 int para_opendir(const char *dirname
, DIR **dir
, int *cwd
)
461 ret
= para_open(".", O_RDONLY
, 0);
466 ret
= para_chdir(dirname
);
472 ret
= -ERRNO_TO_PARA_ERROR(errno
);
473 /* Ignore return value of fchdir() and close(). We're busted anyway. */
475 int __a_unused ret2
= fchdir(*cwd
); /* STFU, gcc */
484 * A wrapper for fchdir().
486 * \param fd An open file descriptor.
490 int para_fchdir(int fd
)
493 return -ERRNO_TO_PARA_ERROR(errno
);
498 * A wrapper for mkdir(2).
500 * \param path Name of the directory to create.
501 * \param mode The permissions to use.
505 int para_mkdir(const char *path
, mode_t mode
)
507 if (!mkdir(path
, mode
))
509 return -ERRNO_TO_PARA_ERROR(errno
);
513 * Open a file and map it into memory.
515 * \param path Name of the regular file to map.
516 * \param open_mode Either \p O_RDONLY or \p O_RDWR.
517 * \param map On success, the mapping is returned here.
518 * \param size size of the mapping.
519 * \param fd_ptr The file descriptor of the mapping.
521 * If \a fd_ptr is \p NULL, the file descriptor resulting from the underlying
522 * open call is closed after mmap(). Otherwise the file is kept open and the
523 * file descriptor is returned in \a fd_ptr.
527 * \sa para_open(), mmap(2).
529 int mmap_full_file(const char *path
, int open_mode
, void **map
,
530 size_t *size
, int *fd_ptr
)
532 int fd
, ret
, mmap_prot
, mmap_flags
;
533 struct stat file_status
;
535 if (open_mode
== O_RDONLY
) {
536 mmap_prot
= PROT_READ
;
537 mmap_flags
= MAP_PRIVATE
;
539 mmap_prot
= PROT_READ
| PROT_WRITE
;
540 mmap_flags
= MAP_SHARED
;
542 ret
= para_open(path
, open_mode
, 0);
546 if (fstat(fd
, &file_status
) < 0) {
547 ret
= -ERRNO_TO_PARA_ERROR(errno
);
550 *size
= file_status
.st_size
;
551 ret
= para_mmap(*size
, mmap_prot
, mmap_flags
, fd
, 0, map
);
553 if (ret
< 0 || !fd_ptr
)
561 * A wrapper for munmap(2).
563 * \param start The start address of the memory mapping.
564 * \param length The size of the mapping.
568 * \sa munmap(2), mmap_full_file().
570 int para_munmap(void *start
, size_t length
)
573 if (munmap(start
, length
) >= 0)
576 PARA_ERROR_LOG("munmap (%p/%zu) failed: %s\n", start
, length
,
578 return -ERRNO_TO_PARA_ERROR(err
);
582 * Check a file descriptor for writability.
584 * \param fd The file descriptor.
586 * \return positive if fd is ready for writing, zero if it isn't, negative if
599 return para_select(fd
+ 1, NULL
, &wfds
, &tv
);
603 * Ensure that file descriptors 0, 1, and 2 are valid.
605 * Common approach that opens /dev/null until it gets a file descriptor greater
608 * \sa okir's Black Hats Manual.
610 void valid_fd_012(void)
613 int fd
= open("/dev/null", O_RDWR
);
624 * Traverse the given directory recursively.
626 * \param dirname The directory to traverse.
627 * \param func The function to call for each entry.
628 * \param private_data Pointer to an arbitrary data structure.
630 * For each regular file under \a dirname, the supplied function \a func is
631 * called. The full path of the regular file and the \a private_data pointer
632 * are passed to \a func. Directories for which the calling process has no
633 * permissions to change to are silently ignored.
637 int for_each_file_in_dir(const char *dirname
,
638 int (*func
)(const char *, void *), void *private_data
)
641 struct dirent
*entry
;
642 int cwd_fd
, ret2
, ret
= para_opendir(dirname
, &dir
, &cwd_fd
);
645 return ret
== -ERRNO_TO_PARA_ERROR(EACCES
)? 1 : ret
;
646 /* scan cwd recursively */
647 while ((entry
= readdir(dir
))) {
652 if (!strcmp(entry
->d_name
, "."))
654 if (!strcmp(entry
->d_name
, ".."))
656 if (lstat(entry
->d_name
, &s
) == -1)
659 if (!S_ISREG(m
) && !S_ISDIR(m
))
661 tmp
= make_message("%s/%s", dirname
, entry
->d_name
);
663 ret
= func(tmp
, private_data
);
670 ret
= for_each_file_in_dir(tmp
, func
, private_data
);
678 ret2
= para_fchdir(cwd_fd
);
679 if (ret2
< 0 && ret
>= 0)