1 | /* clock_getres -- Get the resolution of a POSIX clockid_t. |
2 | Copyright (C) 1999-2022 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 <errno.h> |
20 | #include <stdint.h> |
21 | #include <time.h> |
22 | #include <unistd.h> |
23 | #include <sys/param.h> |
24 | #include <libc-internal.h> |
25 | #include <shlib-compat.h> |
26 | |
27 | static inline int |
28 | realtime_getres (struct timespec *res) |
29 | { |
30 | long int clk_tck = __sysconf (_SC_CLK_TCK); |
31 | |
32 | if (__glibc_likely (clk_tck != -1)) |
33 | { |
34 | /* This implementation assumes that the realtime clock has a |
35 | resolution higher than 1 second. This is the case for any |
36 | reasonable implementation. */ |
37 | if (res) |
38 | { |
39 | res->tv_sec = 0; |
40 | res->tv_nsec = 1000000000 / clk_tck; |
41 | } |
42 | return 0; |
43 | } |
44 | |
45 | return -1; |
46 | } |
47 | |
48 | |
49 | /* Get resolution of clock. */ |
50 | int |
51 | __clock_getres (clockid_t clock_id, struct timespec *res) |
52 | { |
53 | int retval = -1; |
54 | |
55 | switch (clock_id) |
56 | { |
57 | case CLOCK_REALTIME: |
58 | retval = realtime_getres (res); |
59 | break; |
60 | |
61 | default: |
62 | __set_errno (EINVAL); |
63 | break; |
64 | } |
65 | |
66 | return retval; |
67 | } |
68 | libc_hidden_def (__clock_getres) |
69 | |
70 | versioned_symbol (libc, __clock_getres, clock_getres, GLIBC_2_17); |
71 | /* clock_getres moved to libc in version 2.17; |
72 | old binaries may expect the symbol version it had in librt. */ |
73 | #if SHLIB_COMPAT (libc, GLIBC_2_2, GLIBC_2_17) |
74 | strong_alias (__clock_getres, __clock_getres_2); |
75 | compat_symbol (libc, __clock_getres_2, clock_getres, GLIBC_2_2); |
76 | #endif |
77 | |