1/* Copyright (C) 1994-2019 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 <http://www.gnu.org/licenses/>. */
17
18#include <sys/types.h>
19#include <unistd.h>
20#include <fcntl.h>
21#include <errno.h>
22#include <string.h>
23
24/* lockf.c defines lockf64 as an alias if __OFF_T_MATCHES_OFF64_T. */
25#ifndef __OFF_T_MATCHES_OFF64_T
26
27/* lockf is a simplified interface to fcntl's locking facilities. */
28
29int
30lockf64 (int fd, int cmd, off64_t len64)
31{
32 struct flock fl;
33 off_t len = (off_t) len64;
34
35 if (len64 != (off64_t) len)
36 {
37 /* We can't represent the length. */
38 __set_errno (EOVERFLOW);
39 return -1;
40 }
41
42 memset ((char *) &fl, '\0', sizeof (fl));
43
44 /* lockf is always relative to the current file position. */
45 fl.l_whence = SEEK_CUR;
46 fl.l_start = 0;
47 fl.l_len = len;
48
49 switch (cmd)
50 {
51 case F_TEST:
52 /* Test the lock: return 0 if FD is unlocked or locked by this process;
53 return -1, set errno to EACCES, if another process holds the lock. */
54 fl.l_type = F_RDLCK;
55 if (__fcntl (fd, F_GETLK, &fl) < 0)
56 return -1;
57 if (fl.l_type == F_UNLCK || fl.l_pid == __getpid ())
58 return 0;
59 __set_errno (EACCES);
60 return -1;
61
62 case F_ULOCK:
63 fl.l_type = F_UNLCK;
64 cmd = F_SETLK;
65 break;
66 case F_LOCK:
67 fl.l_type = F_WRLCK;
68 cmd = F_SETLKW;
69 break;
70 case F_TLOCK:
71 fl.l_type = F_WRLCK;
72 cmd = F_SETLK;
73 break;
74
75 default:
76 __set_errno (EINVAL);
77 return -1;
78 }
79
80 return __fcntl (fd, cmd, &fl);
81}
82
83#endif
84