1/* Copyright (C) 1994-2020 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
8
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library; if not, see
16 <https://www.gnu.org/licenses/>. */
17
18#include <unistd.h>
19#include <fcntl.h>
20#include <errno.h>
21
22/* lockf is a simplified interface to fcntl's locking facilities. */
23int
24__lockf64 (int fd, int cmd, off64_t len64)
25{
26 /* lockf is always relative to the current file position. */
27 struct flock64 fl64 = {
28 .l_type = F_WRLCK,
29 .l_whence = SEEK_CUR,
30 .l_len = len64,
31 };
32
33 /* lockf() is a cancellation point but so is fcntl() if F_SETLKW is
34 used. Therefore we don't have to care about cancellation here,
35 the fcntl() function will take care of it. */
36 switch (cmd)
37 {
38 case F_TEST:
39 /* Test the lock: return 0 if FD is unlocked or locked by this process;
40 return -1, set errno to EACCES, if another process holds the lock. */
41 fl64.l_type = F_RDLCK;
42 if (__fcntl (fd, F_GETLK64, &fl64) < 0)
43 return -1;
44 if (fl64.l_type == F_UNLCK || fl64.l_pid == __getpid ())
45 return 0;
46 __set_errno (EACCES);
47 return -1;
48 case F_ULOCK:
49 fl64.l_type = F_UNLCK;
50 return __fcntl64 (fd, F_SETLK64, &fl64);
51 case F_LOCK:
52 return __fcntl64 (fd, F_SETLKW64, &fl64);
53 case F_TLOCK:
54 return __fcntl64 (fd, F_SETLK64, &fl64);
55 }
56 __set_errno (EINVAL);
57 return -1;
58}
59weak_alias (__lockf64, lockf64)
60#ifdef __OFF_T_MATCHES_OFF64_T
61weak_alias (lockf64, lockf)
62#endif
63