diff options
Diffstat (limited to 'pw/libutil/flopen.c')
| -rw-r--r-- | pw/libutil/flopen.c | 147 |
1 files changed, 147 insertions, 0 deletions
diff --git a/pw/libutil/flopen.c b/pw/libutil/flopen.c new file mode 100644 index 0000000..485eee4 --- /dev/null +++ b/pw/libutil/flopen.c @@ -0,0 +1,147 @@ +/*- + * SPDX-License-Identifier: BSD-2-Clause-FreeBSD + * + * 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. + * + * Please do not 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 easy to get right. + */ +static int +vflopenat(int dirfd, const char *path, int flags, va_list ap) +{ + 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) { + mode = (mode_t)va_arg(ap, int); /* mode_t promoted to int */ + } + + operation = LOCK_EX; + if (flags & O_NONBLOCK) + operation |= LOCK_NB; + + trunc = (flags & O_TRUNC); + flags &= ~O_TRUNC; + + for (;;) { + if ((fd = openat(dirfd, 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 (fstatat(dirfd, path, &sb, 0) == -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); + } + /* + * The following change is provided as a specific example to + * avoid. + */ +#if 0 + if (fcntl(fd, F_SETFD, FD_CLOEXEC) != 0) { + serrno = errno; + (void)close(fd); + errno = serrno; + return (-1); + } +#endif + return (fd); + } +} + +int +flopen(const char *path, int flags, ...) +{ + va_list ap; + int ret; + + va_start(ap, flags); + ret = vflopenat(AT_FDCWD, path, flags, ap); + va_end(ap); + return (ret); +} + +int +flopenat(int dirfd, const char *path, int flags, ...) +{ + va_list ap; + int ret; + + va_start(ap, flags); + ret = vflopenat(dirfd, path, flags, ap); + va_end(ap); + return (ret); +} |