/*
     This file is part of GNUnet.
     Copyright (C) 2001-2013, 2018 GNUnet e.V.

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

     GNUnet 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
     Affero General Public License for more details.

     You should have received a copy of the GNU Affero General Public License
     along with this program.  If not, see <http://www.gnu.org/licenses/>.

     SPDX-License-Identifier: AGPL3.0-or-later
 */

/**
 * @file util/time.c
 * @author Christian Grothoff
 * @brief functions for handling time and time arithmetic
 */
#include "platform.h"
#include "gnunet_util_lib.h"
#if __STDC_NO_ATOMICS__
#define ATOMIC
#else
#ifdef HAVE_STDATOMIC_H
#include <stdatomic.h>
#define ATOMIC _Atomic
#else
#define __STDC_NO_ATOMICS__ 1
#define ATOMIC
#endif
#endif

#define LOG(kind, ...) GNUNET_log_from (kind, "util-time", __VA_ARGS__)

/**
 * Variable used to simulate clock skew.  Used for testing, never in production.
 */
static long long timestamp_offset;

/**
 * Set the timestamp offset for this instance.
 *
 * @param offset the offset to skew the locale time by
 */
void
GNUNET_TIME_set_offset (long long offset)
{
  timestamp_offset = offset;
}


/**
 * Get the timestamp offset for this instance.
 *
 * @return the offset we currently skew the locale time by
 */
long long
GNUNET_TIME_get_offset ()
{
  return timestamp_offset;
}


/**
 * Round a time value so that it is suitable for transmission
 * via JSON encodings.
 *
 * @param at time to round
 * @return #GNUNET_OK if time was already rounded, #GNUNET_NO if
 *         it was just now rounded
 */
int
GNUNET_TIME_round_abs (struct GNUNET_TIME_Absolute *at)
{
  if (at->abs_value_us == GNUNET_TIME_UNIT_FOREVER_ABS.abs_value_us)
    return GNUNET_OK;
  if (0 == at->abs_value_us % 1000000)
    return GNUNET_OK;
  at->abs_value_us -= at->abs_value_us % 1000000;
  return GNUNET_NO;
}


/**
 * Round a time value so that it is suitable for transmission
 * via JSON encodings.
 *
 * @param rt time to round
 * @return #GNUNET_OK if time was already rounded, #GNUNET_NO if
 *         it was just now rounded
 */
int
GNUNET_TIME_round_rel (struct GNUNET_TIME_Relative *rt)
{
  if (rt->rel_value_us == GNUNET_TIME_UNIT_FOREVER_REL.rel_value_us)
    return GNUNET_OK;
  if (0 == rt->rel_value_us % 1000000)
    return GNUNET_OK;
  rt->rel_value_us -= rt->rel_value_us % 1000000;
  return GNUNET_NO;
}


/**
 * Get the current time (works just as "time", just that we use the
 * unit of time that the cron-jobs use (and is 64 bit)).
 *
 * @return the current time
 */
struct GNUNET_TIME_Absolute
GNUNET_TIME_absolute_get ()
{
  struct GNUNET_TIME_Absolute ret;
  struct timeval tv;

  gettimeofday (&tv, NULL);
  ret.abs_value_us = (uint64_t) (((uint64_t) tv.tv_sec * 1000LL * 1000LL)
                                 + ((uint64_t) tv.tv_usec))
                     + timestamp_offset;
  return ret;
}


/**
 * Return relative time of 0ms.
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_get_zero_ ()
{
  static struct GNUNET_TIME_Relative zero;

  return zero;
}


/**
 * Return absolute time of 0ms.
 */
struct GNUNET_TIME_Absolute
GNUNET_TIME_absolute_get_zero_ ()
{
  static struct GNUNET_TIME_Absolute zero;

  return zero;
}


/**
 * Return relative time of 1us.
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_get_unit_ ()
{
  static struct GNUNET_TIME_Relative one = { 1 };

  return one;
}


/**
 * Return relative time of 1ms.
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_get_millisecond_ ()
{
  static struct GNUNET_TIME_Relative one = { 1000 };

  return one;
}


/**
 * Return relative time of 1s.
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_get_second_ ()
{
  static struct GNUNET_TIME_Relative one = { 1000 * 1000LL };

  return one;
}


/**
 * Return relative time of 1 minute.
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_get_minute_ ()
{
  static struct GNUNET_TIME_Relative one = { 60 * 1000 * 1000LL };

  return one;
}


/**
 * Return relative time of 1 hour.
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_get_hour_ ()
{
  static struct GNUNET_TIME_Relative one = { 60 * 60 * 1000 * 1000LL };

  return one;
}


/**
 * Return "forever".
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_get_forever_ ()
{
  static struct GNUNET_TIME_Relative forever = { UINT64_MAX };

  return forever;
}


/**
 * Return "forever".
 */
struct GNUNET_TIME_Absolute
GNUNET_TIME_absolute_get_forever_ ()
{
  static struct GNUNET_TIME_Absolute forever = { UINT64_MAX };

  return forever;
}


/**
 * Convert relative time to an absolute time in the
 * future.
 *
 * @return timestamp that is "rel" in the future, or FOREVER if rel==FOREVER (or if we would overflow)
 */
struct GNUNET_TIME_Absolute
GNUNET_TIME_relative_to_absolute (struct GNUNET_TIME_Relative rel)
{
  struct GNUNET_TIME_Absolute ret;

  if (rel.rel_value_us == UINT64_MAX)
    return GNUNET_TIME_UNIT_FOREVER_ABS;
  struct GNUNET_TIME_Absolute now = GNUNET_TIME_absolute_get ();

  if (rel.rel_value_us + now.abs_value_us < rel.rel_value_us)
  {
    GNUNET_break (0);  /* overflow... */
    return GNUNET_TIME_UNIT_FOREVER_ABS;
  }
  ret.abs_value_us = rel.rel_value_us + now.abs_value_us;
  return ret;
}


/**
 * Return the minimum of two relative time values.
 *
 * @param t1 first timestamp
 * @param t2 other timestamp
 * @return timestamp that is smaller
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_min (struct GNUNET_TIME_Relative t1,
                          struct GNUNET_TIME_Relative t2)
{
  return (t1.rel_value_us < t2.rel_value_us) ? t1 : t2;
}


/**
 * Return the maximum of two relative time values.
 *
 * @param t1 first timestamp
 * @param t2 other timestamp
 * @return timestamp that is larger
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_max (struct GNUNET_TIME_Relative t1,
                          struct GNUNET_TIME_Relative t2)
{
  return (t1.rel_value_us > t2.rel_value_us) ? t1 : t2;
}


/**
 * Return the minimum of two relative time values.
 *
 * @param t1 first timestamp
 * @param t2 other timestamp
 * @return timestamp that is smaller
 */
struct GNUNET_TIME_Absolute
GNUNET_TIME_absolute_min (struct GNUNET_TIME_Absolute t1,
                          struct GNUNET_TIME_Absolute t2)
{
  return (t1.abs_value_us < t2.abs_value_us) ? t1 : t2;
}


/**
 * Return the maximum of two relative time values.
 *
 * @param t1 first timestamp
 * @param t2 other timestamp
 * @return timestamp that is bigger
 */
struct GNUNET_TIME_Absolute
GNUNET_TIME_absolute_max (struct GNUNET_TIME_Absolute t1,
                          struct GNUNET_TIME_Absolute t2)
{
  return (t1.abs_value_us > t2.abs_value_us) ? t1 : t2;
}


/**
 * Given a timestamp in the future, how much time
 * remains until then?
 *
 * @return future - now, or 0 if now >= future, or FOREVER if future==FOREVER.
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_absolute_get_remaining (struct GNUNET_TIME_Absolute future)
{
  struct GNUNET_TIME_Relative ret;

  if (future.abs_value_us == UINT64_MAX)
    return GNUNET_TIME_UNIT_FOREVER_REL;
  struct GNUNET_TIME_Absolute now = GNUNET_TIME_absolute_get ();

  if (now.abs_value_us > future.abs_value_us)
    return GNUNET_TIME_UNIT_ZERO;
  ret.rel_value_us = future.abs_value_us - now.abs_value_us;
  return ret;
}


/**
 * Compute the time difference between the given start and end times.
 * Use this function instead of actual subtraction to ensure that
 * "FOREVER" and overflows are handled correctly.
 *
 * @return 0 if start >= end; FOREVER if end==FOREVER; otherwise end - start
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_absolute_get_difference (struct GNUNET_TIME_Absolute start,
                                     struct GNUNET_TIME_Absolute end)
{
  struct GNUNET_TIME_Relative ret;

  if (end.abs_value_us == UINT64_MAX)
    return GNUNET_TIME_UNIT_FOREVER_REL;
  if (end.abs_value_us < start.abs_value_us)
    return GNUNET_TIME_UNIT_ZERO;
  ret.rel_value_us = end.abs_value_us - start.abs_value_us;
  return ret;
}


/**
 * Get the duration of an operation as the
 * difference of the current time and the given start time "whence".
 *
 * @return 0 if whence > now, otherwise now-whence.
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_absolute_get_duration (struct GNUNET_TIME_Absolute whence)
{
  struct GNUNET_TIME_Absolute now;
  struct GNUNET_TIME_Relative ret;

  now = GNUNET_TIME_absolute_get ();
  if (whence.abs_value_us > now.abs_value_us)
    return GNUNET_TIME_UNIT_ZERO;
  ret.rel_value_us = now.abs_value_us - whence.abs_value_us;
  return ret;
}


/**
 * Add a given relative duration to the
 * given start time.
 *
 * @return FOREVER if either argument is FOREVER or on overflow; start+duration otherwise
 */
struct GNUNET_TIME_Absolute
GNUNET_TIME_absolute_add (struct GNUNET_TIME_Absolute start,
                          struct GNUNET_TIME_Relative duration)
{
  struct GNUNET_TIME_Absolute ret;

  if ((start.abs_value_us == UINT64_MAX) ||
      (duration.rel_value_us == UINT64_MAX))
    return GNUNET_TIME_UNIT_FOREVER_ABS;
  if (start.abs_value_us + duration.rel_value_us < start.abs_value_us)
  {
    GNUNET_break (0);
    return GNUNET_TIME_UNIT_FOREVER_ABS;
  }
  ret.abs_value_us = start.abs_value_us + duration.rel_value_us;
  return ret;
}


/**
 * Subtract a given relative duration from the
 * given start time.
 *
 * @param start some absolute time
 * @param duration some relative time to subtract
 * @return ZERO if start <= duration, or FOREVER if start time is FOREVER; start-duration otherwise
 */
struct GNUNET_TIME_Absolute
GNUNET_TIME_absolute_subtract (struct GNUNET_TIME_Absolute start,
                               struct GNUNET_TIME_Relative duration)
{
  struct GNUNET_TIME_Absolute ret;

  if (start.abs_value_us <= duration.rel_value_us)
    return GNUNET_TIME_UNIT_ZERO_ABS;
  if (start.abs_value_us == GNUNET_TIME_UNIT_FOREVER_ABS.abs_value_us)
    return GNUNET_TIME_UNIT_FOREVER_ABS;
  ret.abs_value_us = start.abs_value_us - duration.rel_value_us;
  return ret;
}


/**
 * Multiply relative time by a given factor.
 *
 * @return FOREVER if rel=FOREVER or on overflow; otherwise rel*factor
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_multiply (struct GNUNET_TIME_Relative rel,
                               unsigned long long factor)
{
  struct GNUNET_TIME_Relative ret;

  if (0 == factor)
    return GNUNET_TIME_UNIT_ZERO;
  if (rel.rel_value_us == GNUNET_TIME_UNIT_FOREVER_REL.rel_value_us)
    return GNUNET_TIME_UNIT_FOREVER_REL;
  ret.rel_value_us = rel.rel_value_us * factor;
  if (ret.rel_value_us / factor != rel.rel_value_us)
  {
    GNUNET_break (0);
    return GNUNET_TIME_UNIT_FOREVER_REL;
  }
  return ret;
}


/**
 * Multiply relative time by a given floating-point factor.  The factor must be
 * positive.
 *
 * @return FOREVER if rel=FOREVER or on overflow; otherwise rel*factor
 */
struct GNUNET_TIME_Relative
relative_multiply_double (struct GNUNET_TIME_Relative rel, double factor)
{
  struct GNUNET_TIME_Relative out;
  double m;

  GNUNET_assert (0 <= factor);

  if (0 == factor)
    return GNUNET_TIME_UNIT_ZERO;
  if (rel.rel_value_us == GNUNET_TIME_UNIT_FOREVER_REL.rel_value_us)
    return GNUNET_TIME_UNIT_FOREVER_REL;

  m = ((double) rel.rel_value_us) * factor;

  if (m >= (double) (GNUNET_TIME_UNIT_FOREVER_REL).rel_value_us)
  {
    GNUNET_break (0);
    return GNUNET_TIME_UNIT_FOREVER_REL;
  }

  out.rel_value_us = (uint64_t) m;
  return out;
}


/**
 * Saturating multiply relative time by a given factor.
 *
 * @param rel some duration
 * @param factor integer to multiply with
 * @return FOREVER if rel=FOREVER or on overflow; otherwise rel*factor
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_saturating_multiply (struct GNUNET_TIME_Relative rel,
                                          unsigned long long factor)
{
  struct GNUNET_TIME_Relative ret;

  if (0 == factor)
    return GNUNET_TIME_UNIT_ZERO;
  if (rel.rel_value_us == GNUNET_TIME_UNIT_FOREVER_REL.rel_value_us)
    return GNUNET_TIME_UNIT_FOREVER_REL;
  ret.rel_value_us = rel.rel_value_us * factor;
  if (ret.rel_value_us / factor != rel.rel_value_us)
  {
    return GNUNET_TIME_UNIT_FOREVER_REL;
  }
  return ret;
}


/**
 * Divide relative time by a given factor.
 *
 * @param rel some duration
 * @param factor integer to divide by
 * @return FOREVER if rel=FOREVER or factor==0; otherwise rel/factor
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_divide (struct GNUNET_TIME_Relative rel,
                             unsigned long long factor)
{
  struct GNUNET_TIME_Relative ret;

  if ((0 == factor) ||
      (rel.rel_value_us == GNUNET_TIME_UNIT_FOREVER_REL.rel_value_us))
    return GNUNET_TIME_UNIT_FOREVER_REL;
  ret.rel_value_us = rel.rel_value_us / factor;
  return ret;
}


/**
 * Calculate the estimate time of arrival/completion
 * for an operation.
 *
 * @param start when did the operation start?
 * @param finished how much has been done?
 * @param total how much must be done overall (same unit as for "finished")
 * @return remaining duration for the operation,
 *        assuming it continues at the same speed
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_calculate_eta (struct GNUNET_TIME_Absolute start,
                           uint64_t finished,
                           uint64_t total)
{
  struct GNUNET_TIME_Relative dur;
  double exp;
  struct GNUNET_TIME_Relative ret;

  GNUNET_break (finished <= total);
  if (finished >= total)
    return GNUNET_TIME_UNIT_ZERO;
  if (0 == finished)
    return GNUNET_TIME_UNIT_FOREVER_REL;
  dur = GNUNET_TIME_absolute_get_duration (start);
  exp = ((double) dur.rel_value_us) * ((double) total) / ((double) finished);
  ret.rel_value_us = ((uint64_t) exp) - dur.rel_value_us;
  return ret;
}


/**
 * Add relative times together.
 *
 * @param a1 first timestamp
 * @param a2 second timestamp
 * @return FOREVER if either argument is FOREVER or on overflow; a1+a2 otherwise
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_add (struct GNUNET_TIME_Relative a1,
                          struct GNUNET_TIME_Relative a2)
{
  struct GNUNET_TIME_Relative ret;

  if ((a1.rel_value_us == UINT64_MAX) || (a2.rel_value_us == UINT64_MAX))
    return GNUNET_TIME_UNIT_FOREVER_REL;
  if (a1.rel_value_us + a2.rel_value_us < a1.rel_value_us)
  {
    GNUNET_break (0);
    return GNUNET_TIME_UNIT_FOREVER_REL;
  }
  ret.rel_value_us = a1.rel_value_us + a2.rel_value_us;
  return ret;
}


/**
 * Subtract relative timestamp from the other.
 *
 * @param a1 first timestamp
 * @param a2 second timestamp
 * @return ZERO if a2>=a1 (including both FOREVER), FOREVER if a1 is FOREVER, a1-a2 otherwise
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_subtract (struct GNUNET_TIME_Relative a1,
                               struct GNUNET_TIME_Relative a2)
{
  struct GNUNET_TIME_Relative ret;

  if (a2.rel_value_us >= a1.rel_value_us)
    return GNUNET_TIME_UNIT_ZERO;
  if (a1.rel_value_us == UINT64_MAX)
    return GNUNET_TIME_UNIT_FOREVER_REL;
  ret.rel_value_us = a1.rel_value_us - a2.rel_value_us;
  return ret;
}


/**
 * Convert relative time to network byte order.
 *
 * @param a time to convert
 * @return time in network byte order
 */
struct GNUNET_TIME_RelativeNBO
GNUNET_TIME_relative_hton (struct GNUNET_TIME_Relative a)
{
  struct GNUNET_TIME_RelativeNBO ret;

  ret.rel_value_us__ = GNUNET_htonll (a.rel_value_us);
  return ret;
}


/**
 * Convert relative time from network byte order.
 *
 * @param a time to convert
 * @return time in host byte order
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_ntoh (struct GNUNET_TIME_RelativeNBO a)
{
  struct GNUNET_TIME_Relative ret;

  ret.rel_value_us = GNUNET_ntohll (a.rel_value_us__);
  return ret;
}


/**
 * Convert absolute time to network byte order.
 *
 * @param a time to convert
 * @return time in network byte order
 */
struct GNUNET_TIME_AbsoluteNBO
GNUNET_TIME_absolute_hton (struct GNUNET_TIME_Absolute a)
{
  struct GNUNET_TIME_AbsoluteNBO ret;

  ret.abs_value_us__ = GNUNET_htonll (a.abs_value_us);
  return ret;
}


/**
 * Convert absolute time from network byte order.
 *
 * @param a time to convert
 * @return time in host byte order
 */
struct GNUNET_TIME_Absolute
GNUNET_TIME_absolute_ntoh (struct GNUNET_TIME_AbsoluteNBO a)
{
  struct GNUNET_TIME_Absolute ret;

  ret.abs_value_us = GNUNET_ntohll (a.abs_value_us__);
  return ret;
}


/**
 * Return the current year (i.e. '2011').
 */
unsigned int
GNUNET_TIME_get_current_year ()
{
  time_t tp;
  struct tm *t;

  tp = time (NULL);
  t = gmtime (&tp);
  if (t == NULL)
    return 0;
  return t->tm_year + 1900;
}


/**
 * Convert an expiration time to the respective year (rounds)
 *
 * @param at absolute time
 * @return year a year (after 1970), 0 on error
 */
unsigned int
GNUNET_TIME_time_to_year (struct GNUNET_TIME_Absolute at)
{
  struct tm *t;
  time_t tp;

  tp = at.abs_value_us / 1000LL / 1000LL; /* microseconds to seconds */
  t = gmtime (&tp);
  if (t == NULL)
    return 0;
  return t->tm_year + 1900;
}


/**
 * Convert a year to an expiration time of January 1st of that year.
 *
 * @param year a year (after 1970, please ;-)).
 * @return absolute time for January 1st of that year.
 */
struct GNUNET_TIME_Absolute
GNUNET_TIME_year_to_time (unsigned int year)
{
  struct GNUNET_TIME_Absolute ret;
  time_t tp;
  struct tm t;

  memset (&t, 0, sizeof(t));
  if (year < 1900)
  {
    GNUNET_break (0);
    return GNUNET_TIME_absolute_get ();  /* now */
  }
  t.tm_year = year - 1900;
  t.tm_mday = 1;
  t.tm_mon = 0;
  t.tm_wday = 1;
  t.tm_yday = 1;
  tp = mktime (&t);
  GNUNET_break (tp != (time_t) -1);
  ret.abs_value_us = tp * 1000LL * 1000LL; /* seconds to microseconds */
  return ret;
}


/**
 * Randomized exponential back-off, starting at 1 ms
 * and going up by a factor of 2+r, where 0 <= r <= 0.5, up
 * to a maximum of the given threshold.
 *
 * @param r current backoff time, initially zero
 * @param threshold maximum value for backoff
 * @return the next backoff time
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_randomized_backoff (struct GNUNET_TIME_Relative rt,
                                struct GNUNET_TIME_Relative threshold)
{
  double r = (rand () % 500) / 1000.0;
  struct GNUNET_TIME_Relative t;

  t = relative_multiply_double (
    GNUNET_TIME_relative_max (GNUNET_TIME_UNIT_MILLISECONDS, rt),
    2 + r);
  return GNUNET_TIME_relative_min (threshold, t);
}


/**
 * Return a random time value between 0.5*r and 1.5*r.
 *
 * @param r input time for scaling
 * @return randomized time
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_randomize (struct GNUNET_TIME_Relative r)
{
  double d = ((rand () % 1001) - 500) / 1000.0;

  return relative_multiply_double (r, d);
}


/**
 * Obtain the current time and make sure it is monotonically
 * increasing.  Guards against systems without an RTC or
 * clocks running backwards and other nasty surprises. Does
 * not guarantee that the returned time is near the current
 * time returned by #GNUNET_TIME_absolute_get().  Two
 * subsequent calls (within a short time period) may return the
 * same value. Persists the last returned time on disk to
 * ensure that time never goes backwards. As a result, the
 * resulting value can be used to check if a message is the
 * "most recent" value and replays of older messages (from
 * the same origin) would be discarded.
 *
 * @param cfg configuration, used to determine where to
 *   store the time; user can also insist RTC is working
 *   nicely and disable the feature
 * @return monotonically increasing time
 */
struct GNUNET_TIME_Absolute
GNUNET_TIME_absolute_get_monotonic (
  const struct GNUNET_CONFIGURATION_Handle *cfg)
{
  static const struct GNUNET_CONFIGURATION_Handle *last_cfg;
  static struct GNUNET_TIME_Absolute last_time;
  static struct GNUNET_DISK_MapHandle *map_handle;
  static ATOMIC volatile uint64_t *map;
  struct GNUNET_TIME_Absolute now;

  now = GNUNET_TIME_absolute_get ();
  if (last_cfg != cfg)
  {
    char *filename;

    if (NULL != map_handle)
    {
      GNUNET_DISK_file_unmap (map_handle);
      map_handle = NULL;
    }
    map = NULL;

    last_cfg = cfg;
    if ((NULL != cfg) &&
        (GNUNET_OK ==
         GNUNET_CONFIGURATION_get_value_filename (cfg,
                                                  "util",
                                                  "MONOTONIC_TIME_FILENAME",
                                                  &filename)))
    {
      struct GNUNET_DISK_FileHandle *fh;

      fh = GNUNET_DISK_file_open (filename,
                                  GNUNET_DISK_OPEN_READWRITE
                                  | GNUNET_DISK_OPEN_CREATE,
                                  GNUNET_DISK_PERM_USER_WRITE
                                  | GNUNET_DISK_PERM_GROUP_WRITE
                                  | GNUNET_DISK_PERM_USER_READ
                                  | GNUNET_DISK_PERM_GROUP_READ);
      if (NULL == fh)
      {
        GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                    _ ("Failed to map `%s', cannot assure monotonic time!\n"),
                    filename);
      }
      else
      {
        off_t size;

        size = 0;
        GNUNET_break (GNUNET_OK == GNUNET_DISK_file_handle_size (fh, &size));
        if (size < (off_t) sizeof(*map))
        {
          struct GNUNET_TIME_AbsoluteNBO o;

          o = GNUNET_TIME_absolute_hton (now);
          if (sizeof(o) != GNUNET_DISK_file_write (fh, &o, sizeof(o)))
            size = 0;
          else
            size = sizeof(o);
        }
        if (size == sizeof(*map))
        {
          map = GNUNET_DISK_file_map (fh,
                                      &map_handle,
                                      GNUNET_DISK_MAP_TYPE_READWRITE,
                                      sizeof(*map));
          if (NULL == map)
            GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                        _ (
                          "Failed to map `%s', cannot assure monotonic time!\n"),
                        filename);
        }
        else
        {
          GNUNET_log (
            GNUNET_ERROR_TYPE_WARNING,
            _ (
              "Failed to setup monotonic time file `%s', cannot assure monotonic time!\n"),
            filename);
        }
      }
      GNUNET_DISK_file_close (fh);
      GNUNET_free (filename);
    }
  }
  if (NULL != map)
  {
    struct GNUNET_TIME_AbsoluteNBO mt;

#if __STDC_NO_ATOMICS__
#if __GNUC__
    mt.abs_value_us__ = __sync_fetch_and_or (map, 0);
#else
    mt.abs_value_us__ = *map;   /* godspeed, pray this is atomic */
#endif
#else
    mt.abs_value_us__ = atomic_load (map);
#endif
    last_time =
      GNUNET_TIME_absolute_max (GNUNET_TIME_absolute_ntoh (mt), last_time);
  }
  if (now.abs_value_us <= last_time.abs_value_us)
    now.abs_value_us = last_time.abs_value_us + 1;
  last_time = now;
  if (NULL != map)
  {
    uint64_t val = GNUNET_TIME_absolute_hton (now).abs_value_us__;
#if __STDC_NO_ATOMICS__
#if __GNUC__
    (void) __sync_lock_test_and_set (map, val);
#else
    *map = val;   /* godspeed, pray this is atomic */
#endif
#else
    atomic_store (map, val);
#endif
  }
  return now;
}


/**
 * Destructor
 */
void __attribute__ ((destructor))
GNUNET_util_time_fini ()
{
  (void) GNUNET_TIME_absolute_get_monotonic (NULL);
}


/* end of time.c */
