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glibc/sysdeps/posix/clock_getres.c
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/* clock_getres -- Get the resolution of a POSIX clockid_t. | |
Copyright (C) 1999-2013 Free Software Foundation, Inc. | |
This file is part of the GNU C Library. | |
The GNU C Library is free software; you can redistribute it and/or | |
modify it under the terms of the GNU Lesser General Public | |
License as published by the Free Software Foundation; either | |
version 2.1 of the License, or (at your option) any later version. | |
The GNU C Library is distributed in the hope that it will be useful, | |
but WITHOUT ANY WARRANTY; without even the implied warranty of | |
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
Lesser General Public License for more details. | |
You should have received a copy of the GNU Lesser General Public | |
License along with the GNU C Library; if not, see | |
<http://www.gnu.org/licenses/>. */ | |
#include <errno.h> | |
#include <stdint.h> | |
#include <time.h> | |
#include <unistd.h> | |
#include <sys/param.h> | |
#include <libc-internal.h> | |
#if HP_TIMING_AVAIL | |
static long int nsec; /* Clock frequency of the processor. */ | |
static int | |
hp_timing_getres (struct timespec *res) | |
{ | |
if (__builtin_expect (nsec == 0, 0)) | |
{ | |
hp_timing_t freq; | |
/* This can only happen if we haven't initialized the `nsec' | |
variable yet. Do this now. We don't have to protect this | |
code against multiple execution since all of them should | |
lead to the same result. */ | |
freq = __get_clockfreq (); | |
if (__builtin_expect (freq == 0, 0)) | |
/* Something went wrong. */ | |
return -1; | |
nsec = MAX (UINT64_C (1000000000) / freq, 1); | |
} | |
/* Fill in the values. | |
The seconds are always zero (unless we have a 1Hz machine). */ | |
res->tv_sec = 0; | |
res->tv_nsec = nsec; | |
return 0; | |
} | |
#endif | |
static inline int | |
realtime_getres (struct timespec *res) | |
{ | |
long int clk_tck = sysconf (_SC_CLK_TCK); | |
if (__builtin_expect (clk_tck != -1, 1)) | |
{ | |
/* This implementation assumes that the realtime clock has a | |
resolution higher than 1 second. This is the case for any | |
reasonable implementation. */ | |
res->tv_sec = 0; | |
res->tv_nsec = 1000000000 / clk_tck; | |
return 0; | |
} | |
return -1; | |
} | |
/* Get resolution of clock. */ | |
int | |
__clock_getres (clockid_t clock_id, struct timespec *res) | |
{ | |
int retval = -1; | |
switch (clock_id) | |
{ | |
#ifdef SYSDEP_GETRES | |
SYSDEP_GETRES; | |
#endif | |
#ifndef HANDLED_REALTIME | |
case CLOCK_REALTIME: | |
retval = realtime_getres (res); | |
break; | |
#endif /* handled REALTIME */ | |
default: | |
#ifdef SYSDEP_GETRES_CPU | |
SYSDEP_GETRES_CPU; | |
#endif | |
#if HP_TIMING_AVAIL | |
if ((clock_id & ((1 << CLOCK_IDFIELD_SIZE) - 1)) | |
== CLOCK_THREAD_CPUTIME_ID) | |
retval = hp_timing_getres (res); | |
else | |
#endif | |
__set_errno (EINVAL); | |
break; | |
#if HP_TIMING_AVAIL && !defined HANDLED_CPUTIME | |
case CLOCK_PROCESS_CPUTIME_ID: | |
case CLOCK_THREAD_CPUTIME_ID: | |
retval = hp_timing_getres (res); | |
break; | |
#endif | |
} | |
return retval; | |
} | |
weak_alias (__clock_getres, clock_getres) |