1/* clock_getres -- Get the resolution of a POSIX clockid_t.
2 Copyright (C) 1999-2019 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 <http://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
26
27#if HP_TIMING_AVAIL
28static long int nsec; /* Clock frequency of the processor. */
29
30static int
31hp_timing_getres (struct timespec *res)
32{
33 if (__glibc_unlikely (nsec == 0))
34 {
35 hp_timing_t freq;
36
37 /* This can only happen if we haven't initialized the `nsec'
38 variable yet. Do this now. We don't have to protect this
39 code against multiple execution since all of them should
40 lead to the same result. */
41 freq = __get_clockfreq ();
42 if (__glibc_unlikely (freq == 0))
43 /* Something went wrong. */
44 return -1;
45
46 nsec = MAX (UINT64_C (1000000000) / freq, 1);
47 }
48
49 /* Fill in the values.
50 The seconds are always zero (unless we have a 1Hz machine). */
51 res->tv_sec = 0;
52 res->tv_nsec = nsec;
53
54 return 0;
55}
56#endif
57
58static inline int
59realtime_getres (struct timespec *res)
60{
61 long int clk_tck = __sysconf (_SC_CLK_TCK);
62
63 if (__glibc_likely (clk_tck != -1))
64 {
65 /* This implementation assumes that the realtime clock has a
66 resolution higher than 1 second. This is the case for any
67 reasonable implementation. */
68 res->tv_sec = 0;
69 res->tv_nsec = 1000000000 / clk_tck;
70 return 0;
71 }
72
73 return -1;
74}
75
76
77/* Get resolution of clock. */
78int
79__clock_getres (clockid_t clock_id, struct timespec *res)
80{
81 int retval = -1;
82
83 switch (clock_id)
84 {
85#ifdef SYSDEP_GETRES
86 SYSDEP_GETRES;
87#endif
88
89#ifndef HANDLED_REALTIME
90 case CLOCK_REALTIME:
91 retval = realtime_getres (res);
92 break;
93#endif /* handled REALTIME */
94
95 default:
96#ifdef SYSDEP_GETRES_CPU
97 SYSDEP_GETRES_CPU;
98#endif
99#if HP_TIMING_AVAIL
100 if ((clock_id & ((1 << CLOCK_IDFIELD_SIZE) - 1))
101 == CLOCK_THREAD_CPUTIME_ID)
102 retval = hp_timing_getres (res);
103 else
104#endif
105 __set_errno (EINVAL);
106 break;
107
108#if HP_TIMING_AVAIL && !defined HANDLED_CPUTIME
109 case CLOCK_PROCESS_CPUTIME_ID:
110 case CLOCK_THREAD_CPUTIME_ID:
111 retval = hp_timing_getres (res);
112 break;
113#endif
114 }
115
116 return retval;
117}
118weak_alias (__clock_getres, clock_getres)
119