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/* Copyright (C) 1994-2021 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 <bits/types.h>
#ifndef __OFF_T_MATCHES_OFF64_T
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
/* lockf is a simplified interface to fcntl's locking facilities. */
int
lockf (int fd, int cmd, off_t len)
{
/* lockf is always relative to the current file position. */
struct flock fl = {
.l_type = F_WRLCK,
.l_whence = SEEK_CUR,
.l_len = len
};
/* lockf() is a cancellation point but so is fcntl() if F_SETLKW is
used. Therefore we don't have to care about cancellation here,
the fcntl() function will take care of it. */
switch (cmd)
{
case F_TEST:
/* Test the lock: return 0 if FD is unlocked or locked by this process;
return -1, set errno to EACCES, if another process holds the lock. */
fl.l_type = F_RDLCK;
if (__fcntl (fd, F_GETLK, &fl) < 0)
return -1;
if (fl.l_type == F_UNLCK || fl.l_pid == __getpid ())
return 0;
__set_errno (EACCES);
return -1;
case F_ULOCK:
fl.l_type = F_UNLCK;
return __fcntl (fd, F_SETLK, &fl);
case F_LOCK:
return __fcntl (fd, F_SETLKW, &fl);
case F_TLOCK:
return __fcntl (fd, F_SETLK, &fl);
}
__set_errno (EINVAL);
return -1;
}
#endif
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