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/* clock_getres -- Get the resolution of a POSIX clockid_t.
Copyright (C) 1999-2015 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 (__glibc_unlikely (nsec == 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 (__glibc_unlikely (freq == 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 (__glibc_likely (clk_tck != -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)
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