/* Implementation of the SYSTEM_CLOCK intrinsic.
   Copyright (C) 2004-2013 Free Software Foundation, Inc.

This file is part of the GNU Fortran runtime library (libgfortran).

Libgfortran is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public
License as published by the Free Software Foundation; either
version 3 of the License, or (at your option) any later version.

Libgfortran 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 General Public License for more details.

Under Section 7 of GPL version 3, you are granted additional
permissions described in the GCC Runtime Library Exception, version
3.1, as published by the Free Software Foundation.

You should have received a copy of the GNU General Public License and
a copy of the GCC Runtime Library Exception along with this program;
see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
<http://www.gnu.org/licenses/>.  */

#include "libgfortran.h"

#include <limits.h>

#include "time_1.h"


/* POSIX states that CLOCK_REALTIME must be present if clock_gettime
   is available, others are optional.  */
#if defined(HAVE_CLOCK_GETTIME) || defined(HAVE_CLOCK_GETTIME_LIBRT)
#if defined(CLOCK_MONOTONIC) && defined(_POSIX_MONOTONIC_CLOCK) \
  && _POSIX_MONOTONIC_CLOCK >= 0
#define GF_CLOCK_MONOTONIC CLOCK_MONOTONIC
#else
#define GF_CLOCK_MONOTONIC CLOCK_REALTIME
#endif
#endif

/* Weakref trickery for clock_gettime().  On Glibc, clock_gettime()
   requires us to link in librt, which also pulls in libpthread.  In
   order to avoid this by default, only call clock_gettime() through a
   weak reference. 

   Some targets don't support weak undefined references; on these
   GTHREAD_USE_WEAK is 0. So we need to define it to 1 on other
   targets.  */
#ifndef GTHREAD_USE_WEAK
#define GTHREAD_USE_WEAK 1
#endif

#if SUPPORTS_WEAK && GTHREAD_USE_WEAK && defined(HAVE_CLOCK_GETTIME_LIBRT)
static int weak_gettime (clockid_t, struct timespec *) 
  __attribute__((__weakref__("clock_gettime")));
#endif


/* High resolution monotonic clock, falling back to the realtime clock
   if the target does not support such a clock.

   Arguments:
   secs     - OUTPUT, seconds
   nanosecs - OUTPUT, nanoseconds
   tk       - OUTPUT, clock resolution [counts/sec]

   If the target supports a monotonic clock, the OUTPUT arguments
   represent a monotonically incrementing clock starting from some
   unspecified time in the past.

   If a monotonic clock is not available, falls back to the realtime
   clock which is not monotonic.

   Return value: 0 for success, -1 for error. In case of error, errno
   is set.
*/
static int
gf_gettime_mono (time_t * secs, long * nanosecs, long * tck)
{
  int err;
#ifdef HAVE_CLOCK_GETTIME
  struct timespec ts;
  *tck = 1000000000;
  err = clock_gettime (GF_CLOCK_MONOTONIC, &ts);
  *secs = ts.tv_sec;
  *nanosecs = ts.tv_nsec;
  return err;
#else
#if defined(HAVE_CLOCK_GETTIME_LIBRT) && SUPPORTS_WEAK && GTHREAD_USE_WEAK
  if (weak_gettime)
    {
      struct timespec ts;
      *tck = 1000000000;
      err = weak_gettime (GF_CLOCK_MONOTONIC, &ts);
      *secs = ts.tv_sec;
      *nanosecs = ts.tv_nsec;
      return err;
    }
#endif
  *tck = 1000000;
  err = gf_gettime (secs, nanosecs);
  *nanosecs *= 1000;
  return err;
#endif
}

extern void system_clock_4 (GFC_INTEGER_4 *, GFC_INTEGER_4 *, GFC_INTEGER_4 *);
export_proto(system_clock_4);

extern void system_clock_8 (GFC_INTEGER_8 *, GFC_INTEGER_8 *, GFC_INTEGER_8 *);
export_proto(system_clock_8);


/* prefix(system_clock_4) is the INTEGER(4) version of the SYSTEM_CLOCK
   intrinsic subroutine.  It returns the number of clock ticks for the current
   system time, the number of ticks per second, and the maximum possible value
   for COUNT.  On the first call to SYSTEM_CLOCK, COUNT is set to zero. */

void
system_clock_4(GFC_INTEGER_4 *count, GFC_INTEGER_4 *count_rate,
	       GFC_INTEGER_4 *count_max)
{
  GFC_INTEGER_4 cnt;
  GFC_INTEGER_4 mx;

  time_t secs;
  long nanosecs, tck;

  if (sizeof (secs) < sizeof (GFC_INTEGER_4))
    internal_error (NULL, "secs too small");

  if (gf_gettime_mono (&secs, &nanosecs, &tck) == 0)
    {
      tck = tck>1000 ? 1000 : tck;
      GFC_UINTEGER_4 ucnt = (GFC_UINTEGER_4) secs * tck;
      ucnt += (nanosecs + 500000000 / tck) / (1000000000 / tck);
      if (ucnt > GFC_INTEGER_4_HUGE)
	cnt = ucnt - GFC_INTEGER_4_HUGE - 1;
      else
	cnt = ucnt;
      mx = GFC_INTEGER_4_HUGE;
    }
  else
    {
      if (count != NULL)
	*count = - GFC_INTEGER_4_HUGE;
      if (count_rate != NULL)
	*count_rate = 0;
      if (count_max != NULL)
	*count_max = 0;
      return;
    }

  if (count != NULL)
    *count = cnt;
  if (count_rate != NULL)
    *count_rate = tck;
  if (count_max != NULL)
    *count_max = mx;
}


/* INTEGER(8) version of the above routine.  */

void
system_clock_8 (GFC_INTEGER_8 *count, GFC_INTEGER_8 *count_rate,
		GFC_INTEGER_8 *count_max)
{
  GFC_INTEGER_8 cnt;
  GFC_INTEGER_8 mx;

  time_t secs;
  long nanosecs, tck;

  if (sizeof (secs) < sizeof (GFC_INTEGER_4))
    internal_error (NULL, "secs too small");

  if (gf_gettime_mono (&secs, &nanosecs, &tck) == 0)
    {
      GFC_UINTEGER_8 ucnt = (GFC_UINTEGER_8) secs * tck;
      ucnt += (nanosecs + 500000000 / tck) / (1000000000 / tck);
      if (ucnt > GFC_INTEGER_8_HUGE)
	cnt = ucnt - GFC_INTEGER_8_HUGE - 1;
      else
	cnt = ucnt;
      mx = GFC_INTEGER_8_HUGE;
    }
  else
    {
      if (count != NULL)
	*count = - GFC_INTEGER_8_HUGE;
      if (count_rate != NULL)
	*count_rate = 0;
      if (count_max != NULL)
	*count_max = 0;

      return;
    }

  if (count != NULL)
    *count = cnt;
  if (count_rate != NULL)
    *count_rate = tck;
  if (count_max != NULL)
    *count_max = mx;
}
