/* clock_getres -- Get the resolution of a POSIX clockid_t.

   Copyright (C) 1999-2018 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>

#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.  */

      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;

}

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