/* 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>

#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)

    {

    case CLOCK_REALTIME:

      retval = realtime_getres (res);

      break;

    default:

#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

    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)