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/* clock_getres -- Get the resolution of a POSIX clockid_t.
Copyright (C) 1999-2025 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
<https://www.gnu.org/licenses/>. */
#include <errno.h>
#include <stdint.h>
#include <time.h>
#include <unistd.h>
#include <sys/param.h>
#include <libc-internal.h>
#include <shlib-compat.h>
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. */
if (res)
{
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)
{
case CLOCK_REALTIME:
retval = realtime_getres (res);
break;
default:
__set_errno (EINVAL);
break;
}
return retval;
}
libc_hidden_def (__clock_getres)
versioned_symbol (libc, __clock_getres, clock_getres, GLIBC_2_17);
/* clock_getres moved to libc in version 2.17;
old binaries may expect the symbol version it had in librt. */
#if SHLIB_COMPAT (libc, GLIBC_2_2, GLIBC_2_17)
strong_alias (__clock_getres, __clock_getres_2);
compat_symbol (libc, __clock_getres_2, clock_getres, GLIBC_2_2);
#endif
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