64 lines
2.0 KiB
C
64 lines
2.0 KiB
C
/* Copyright (C) 1994-2022 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
|