1 | /* f_setlk -- locking part of fcntl |
2 | Copyright (C) 2014-2022 Free Software Foundation, Inc. |
3 | This file is part of the GNU C Library. |
4 | |
5 | The GNU C Library is free software; you can redistribute it and/or |
6 | modify it under the terms of the GNU Lesser General Public |
7 | License as published by the Free Software Foundation; either |
8 | version 2.1 of the License, or (at your option) any later version. |
9 | |
10 | The GNU C Library is distributed in the hope that it will be useful, |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
13 | Lesser General Public License for more details. |
14 | |
15 | You should have received a copy of the GNU Lesser General Public |
16 | License along with the GNU C Library; if not, see |
17 | <https://www.gnu.org/licenses/>. */ |
18 | |
19 | #include <sys/types.h> |
20 | #include <sys/file.h> |
21 | #include <fcntl.h> |
22 | #include <unistd.h> |
23 | #include <errno.h> |
24 | |
25 | /* XXX |
26 | We need new RPCs to support POSIX.1 fcntl file locking!! |
27 | For the time being we support the whole-file case only, |
28 | with all kinds of WRONG WRONG WRONG semantics, |
29 | by using flock. This is definitely the Wrong Thing, |
30 | but it might be better than nothing (?). */ |
31 | int |
32 | __f_setlk (int fd, int type, int whence, __off64_t start, __off64_t len, int wait) |
33 | { |
34 | int cmd = 0; |
35 | |
36 | switch (type) |
37 | { |
38 | case F_RDLCK: cmd = LOCK_SH; break; |
39 | case F_WRLCK: cmd = LOCK_EX; break; |
40 | case F_UNLCK: cmd = LOCK_UN; break; |
41 | default: |
42 | errno = EINVAL; |
43 | return -1; |
44 | } |
45 | |
46 | if (cmd != LOCK_UN && wait == 0) |
47 | cmd |= LOCK_NB; |
48 | |
49 | if (whence == SEEK_CUR) |
50 | { |
51 | /* In case the target position is 0, we can support it below. */ |
52 | __off64_t cur = __lseek64 (fd: fd, offset: 0, SEEK_CUR); |
53 | |
54 | if (cur >= 0) |
55 | { |
56 | start = cur + start; |
57 | whence = SEEK_SET; |
58 | } |
59 | } |
60 | |
61 | switch (whence) |
62 | { |
63 | case SEEK_SET: |
64 | if (start == 0 && len == 0) /* Whole file request. */ |
65 | break; |
66 | /* It seems to be common for applications to lock the first |
67 | byte of the file when they are really doing whole-file locking. |
68 | So, since it's so wrong already, might as well do that too. */ |
69 | if (start == 0 && len == 1) |
70 | break; |
71 | /* FALLTHROUGH */ |
72 | case SEEK_CUR: |
73 | case SEEK_END: |
74 | errno = ENOTSUP; |
75 | return -1; |
76 | default: |
77 | errno = EINVAL; |
78 | return -1; |
79 | } |
80 | |
81 | return __flock (fd: fd, operation: cmd); |
82 | } |
83 | |