122 lines
3.3 KiB
C
122 lines
3.3 KiB
C
/*-
|
|
* Copyright (c) 2007-2009 Dag-Erling Coïdan Smørgrav
|
|
* All rights reserved.
|
|
*
|
|
* Redistribution and use in source and binary forms, with or without
|
|
* modification, are permitted provided that the following conditions
|
|
* are met:
|
|
* 1. Redistributions of source code must retain the above copyright
|
|
* notice, this list of conditions and the following disclaimer
|
|
* in this position and unchanged.
|
|
* 2. Redistributions in binary form must reproduce the above copyright
|
|
* notice, this list of conditions and the following disclaimer in the
|
|
* documentation and/or other materials provided with the distribution.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
|
|
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
|
|
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
* SUCH DAMAGE.
|
|
*/
|
|
|
|
#include <sys/cdefs.h>
|
|
__FBSDID("$FreeBSD$");
|
|
|
|
#include <sys/file.h>
|
|
#include <sys/stat.h>
|
|
|
|
#include <errno.h>
|
|
#include <stdarg.h>
|
|
#include <unistd.h>
|
|
|
|
#include <libutil.h>
|
|
|
|
/*
|
|
* Reliably open and lock a file.
|
|
*
|
|
* DO NOT, UNDER PAIN OF DEATH, modify this code without first reading the
|
|
* revision history and discussing your changes with <des@freebsd.org>.
|
|
* Don't be fooled by the code's apparent simplicity; there would be no
|
|
* need for this function if it was as easy to get right as you think.
|
|
*/
|
|
int
|
|
flopen(const char *path, int flags, ...)
|
|
{
|
|
int fd, operation, serrno, trunc;
|
|
struct stat sb, fsb;
|
|
mode_t mode;
|
|
|
|
#ifdef O_EXLOCK
|
|
flags &= ~O_EXLOCK;
|
|
#endif
|
|
|
|
mode = 0;
|
|
if (flags & O_CREAT) {
|
|
va_list ap;
|
|
|
|
va_start(ap, flags);
|
|
mode = (mode_t)va_arg(ap, int); /* mode_t promoted to int */
|
|
va_end(ap);
|
|
}
|
|
|
|
operation = LOCK_EX;
|
|
if (flags & O_NONBLOCK)
|
|
operation |= LOCK_NB;
|
|
|
|
trunc = (flags & O_TRUNC);
|
|
flags &= ~O_TRUNC;
|
|
|
|
for (;;) {
|
|
if ((fd = open(path, flags, mode)) == -1)
|
|
/* non-existent or no access */
|
|
return (-1);
|
|
if (flock(fd, operation) == -1) {
|
|
/* unsupported or interrupted */
|
|
serrno = errno;
|
|
(void)close(fd);
|
|
errno = serrno;
|
|
return (-1);
|
|
}
|
|
if (stat(path, &sb) == -1) {
|
|
/* disappeared from under our feet */
|
|
(void)close(fd);
|
|
continue;
|
|
}
|
|
if (fstat(fd, &fsb) == -1) {
|
|
/* can't happen [tm] */
|
|
serrno = errno;
|
|
(void)close(fd);
|
|
errno = serrno;
|
|
return (-1);
|
|
}
|
|
if (sb.st_dev != fsb.st_dev ||
|
|
sb.st_ino != fsb.st_ino) {
|
|
/* changed under our feet */
|
|
(void)close(fd);
|
|
continue;
|
|
}
|
|
if (trunc && ftruncate(fd, 0) != 0) {
|
|
/* can't happen [tm] */
|
|
serrno = errno;
|
|
(void)close(fd);
|
|
errno = serrno;
|
|
return (-1);
|
|
}
|
|
#ifdef DONT_EVEN_THINK_ABOUT_IT
|
|
if (fcntl(fd, F_SETFD, FD_CLOEXEC) != 0) {
|
|
serrno = errno;
|
|
(void)close(fd);
|
|
errno = serrno;
|
|
return (-1);
|
|
}
|
|
#endif
|
|
return (fd);
|
|
}
|
|
}
|