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/* f_setlk -- locking part of fcntl
Copyright (C) 2014-2021 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <sys/types.h>
#include <sys/file.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
/* XXX
We need new RPCs to support POSIX.1 fcntl file locking!!
For the time being we support the whole-file case only,
with all kinds of WRONG WRONG WRONG semantics,
by using flock. This is definitely the Wrong Thing,
but it might be better than nothing (?). */
int
__f_setlk (int fd, int type, int whence, __off64_t start, __off64_t len, int wait)
{
int cmd = 0;
switch (type)
{
case F_RDLCK: cmd = LOCK_SH; break;
case F_WRLCK: cmd = LOCK_EX; break;
case F_UNLCK: cmd = LOCK_UN; break;
default:
errno = EINVAL;
return -1;
}
if (cmd != LOCK_UN && wait == 0)
cmd |= LOCK_NB;
if (whence == SEEK_CUR)
{
/* In case the target position is 0, we can support it below. */
__off64_t cur = __lseek64 (fd, 0, SEEK_CUR);
if (cur >= 0)
{
start = cur + start;
whence = SEEK_SET;
}
}
switch (whence)
{
case SEEK_SET:
if (start == 0 && len == 0) /* Whole file request. */
break;
/* It seems to be common for applications to lock the first
byte of the file when they are really doing whole-file locking.
So, since it's so wrong already, might as well do that too. */
if (start == 0 && len == 1)
break;
/* FALLTHROUGH */
case SEEK_CUR:
case SEEK_END:
errno = ENOTSUP;
return -1;
default:
errno = EINVAL;
return -1;
}
return __flock (fd, cmd);
}
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