glib/gtimer.c - third_party/glib - Git at Google

 /* GLIB - Library of useful routines for C programming
  * Copyright (C) 1995-1997  Peter Mattis, Spencer Kimball and Josh MacDonald
  *
  * This 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.
  *
  * This 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 this library; if not, see <http://www.gnu.org/licenses/>.
  */

 /*
  * Modified by the GLib Team and others 1997-2000.  See the AUTHORS
  * file for a list of people on the GLib Team.  See the ChangeLog
  * files for a list of changes.  These files are distributed with
  * GLib at ftp://ftp.gtk.org/pub/gtk/.
  */

 /*
  * MT safe
  */

 #include "config.h"
 #include "glibconfig.h"

 #include <stdlib.h>

 #ifdef G_OS_UNIX
 #include <unistd.h>
 #endif /* G_OS_UNIX */

 #ifdef HAVE_SYS_TIME_H
 #include <sys/time.h>
 #endif
 #include <time.h>
 #ifndef G_OS_WIN32
 #include <errno.h>
 #endif /* G_OS_WIN32 */

 #ifdef G_OS_WIN32
 #include <windows.h>
 #endif /* G_OS_WIN32 */

 #include "gtimer.h"

 #include "gmem.h"
 #include "gstrfuncs.h"
 #include "gtestutils.h"
 #include "gmain.h"

 /**
  * SECTION:timers
  * @title: Timers
  * @short_description: keep track of elapsed time
  *
  * #GTimer records a start time, and counts microseconds elapsed since
  * that time. This is done somewhat differently on different platforms,
  * and can be tricky to get exactly right, so #GTimer provides a
  * portable/convenient interface.
  **/

 /**
  * GTimer:
  *
  * Opaque datatype that records a start time.
  **/
 struct _GTimer
 {
   guint64 start;
   guint64 end;

   guint active : 1;
 };

 /**
  * g_timer_new:
  *
  * Creates a new timer, and starts timing (i.e. g_timer_start() is
  * implicitly called for you).
  *
  * Returns: a new #GTimer.
  **/
 GTimer*
 g_timer_new (void)
 {
   GTimer *timer;

   timer = g_new (GTimer, 1);
   timer->active = TRUE;

   timer->start = g_get_monotonic_time ();

   return timer;
 }

 /**
  * g_timer_destroy:
  * @timer: a #GTimer to destroy.
  *
  * Destroys a timer, freeing associated resources.
  **/
 void
 g_timer_destroy (GTimer *timer)
 {
   g_return_if_fail (timer != NULL);

   g_free (timer);
 }

 /**
  * g_timer_start:
  * @timer: a #GTimer.
  *
  * Marks a start time, so that future calls to g_timer_elapsed() will
  * report the time since g_timer_start() was called. g_timer_new()
  * automatically marks the start time, so no need to call
  * g_timer_start() immediately after creating the timer.
  **/
 void
 g_timer_start (GTimer *timer)
 {
   g_return_if_fail (timer != NULL);

   timer->active = TRUE;

   timer->start = g_get_monotonic_time ();
 }

 /**
  * g_timer_stop:
  * @timer: a #GTimer.
  *
  * Marks an end time, so calls to g_timer_elapsed() will return the
  * difference between this end time and the start time.
  **/
 void
 g_timer_stop (GTimer *timer)
 {
   g_return_if_fail (timer != NULL);

   timer->active = FALSE;

   timer->end = g_get_monotonic_time ();
 }

 /**
  * g_timer_reset:
  * @timer: a #GTimer.
  *
  * This function is useless; it's fine to call g_timer_start() on an
  * already-started timer to reset the start time, so g_timer_reset()
  * serves no purpose.
  **/
 void
 g_timer_reset (GTimer *timer)
 {
   g_return_if_fail (timer != NULL);

   timer->start = g_get_monotonic_time ();
 }

 /**
  * g_timer_continue:
  * @timer: a #GTimer.
  *
  * Resumes a timer that has previously been stopped with
  * g_timer_stop(). g_timer_stop() must be called before using this
  * function.
  *
  * Since: 2.4
  **/
 void
 g_timer_continue (GTimer *timer)
 {
   guint64 elapsed;

   g_return_if_fail (timer != NULL);
   g_return_if_fail (timer->active == FALSE);

   /* Get elapsed time and reset timer start time
    *  to the current time minus the previously
    *  elapsed interval.
    */

   elapsed = timer->end - timer->start;

   timer->start = g_get_monotonic_time ();

   timer->start -= elapsed;

   timer->active = TRUE;
 }

 /**
  * g_timer_elapsed:
  * @timer: a #GTimer.
  * @microseconds: return location for the fractional part of seconds
  *                elapsed, in microseconds (that is, the total number
  *                of microseconds elapsed, modulo 1000000), or %NULL
  *
  * If @timer has been started but not stopped, obtains the time since
  * the timer was started. If @timer has been stopped, obtains the
  * elapsed time between the time it was started and the time it was
  * stopped. The return value is the number of seconds elapsed,
  * including any fractional part. The @microseconds out parameter is
  * essentially useless.
  *
  * Returns: seconds elapsed as a floating point value, including any
  *          fractional part.
  **/
 gdouble
 g_timer_elapsed (GTimer *timer,
 		 gulong *microseconds)
 {
   gdouble total;
   gint64 elapsed;

   g_return_val_if_fail (timer != NULL, 0);

   if (timer->active)
     timer->end = g_get_monotonic_time ();

   elapsed = timer->end - timer->start;

   total = elapsed / 1e6;

   if (microseconds)
     *microseconds = elapsed % 1000000;

   return total;
 }

 /**
  * g_usleep:
  * @microseconds: number of microseconds to pause
  *
  * Pauses the current thread for the given number of microseconds.
  *
  * There are 1 million microseconds per second (represented by the
  * #G_USEC_PER_SEC macro). g_usleep() may have limited precision,
  * depending on hardware and operating system; don't rely on the exact
  * length of the sleep.
  */
 void
 g_usleep (gulong microseconds)
 {
 #ifdef G_OS_WIN32
   /* Round up to the next millisecond */
   Sleep (microseconds ? (1 + (microseconds - 1) / 1000) : 0);
 #else
   struct timespec request, remaining;
   request.tv_sec = microseconds / G_USEC_PER_SEC;
   request.tv_nsec = 1000 * (microseconds % G_USEC_PER_SEC);
   while (nanosleep (&request, &remaining) == -1 && errno == EINTR)
     request = remaining;
 #endif
 }

 /**
  * g_time_val_add:
  * @time_: a #GTimeVal
  * @microseconds: number of microseconds to add to @time
  *
  * Adds the given number of microseconds to @time_. @microseconds can
  * also be negative to decrease the value of @time_.
  **/
 void
 g_time_val_add (GTimeVal *time_, glong microseconds)
 {
   g_return_if_fail (time_->tv_usec >= 0 && time_->tv_usec < G_USEC_PER_SEC);

   if (microseconds >= 0)
     {
       time_->tv_usec += microseconds % G_USEC_PER_SEC;
       time_->tv_sec += microseconds / G_USEC_PER_SEC;
       if (time_->tv_usec >= G_USEC_PER_SEC)
        {
          time_->tv_usec -= G_USEC_PER_SEC;
          time_->tv_sec++;
        }
     }
   else
     {
       microseconds *= -1;
       time_->tv_usec -= microseconds % G_USEC_PER_SEC;
       time_->tv_sec -= microseconds / G_USEC_PER_SEC;
       if (time_->tv_usec < 0)
        {
          time_->tv_usec += G_USEC_PER_SEC;
          time_->tv_sec--;
        }
     }
 }

 /* converts a broken down date representation, relative to UTC,
  * to a timestamp; it uses timegm() if it's available.
  */
 static time_t
 mktime_utc (struct tm *tm)
 {
   time_t retval;

 #ifndef HAVE_TIMEGM
   static const gint days_before[] =
   {
     0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334
   };
 #endif

 #ifndef HAVE_TIMEGM
   if (tm->tm_mon < 0 || tm->tm_mon > 11)
     return (time_t) -1;

   retval = (tm->tm_year - 70) * 365;
   retval += (tm->tm_year - 68) / 4;
   retval += days_before[tm->tm_mon] + tm->tm_mday - 1;

   if (tm->tm_year % 4 == 0 && tm->tm_mon < 2)
     retval -= 1;

   retval = ((((retval * 24) + tm->tm_hour) * 60) + tm->tm_min) * 60 + tm->tm_sec;
 #else
   retval = timegm (tm);
 #endif /* !HAVE_TIMEGM */

   return retval;
 }

 /**
  * g_time_val_from_iso8601:
  * @iso_date: an ISO 8601 encoded date string
  * @time_: (out): a #GTimeVal
  *
  * Converts a string containing an ISO 8601 encoded date and time
  * to a #GTimeVal and puts it into @time_.
  *
  * @iso_date must include year, month, day, hours, minutes, and
  * seconds. It can optionally include fractions of a second and a time
  * zone indicator. (In the absence of any time zone indication, the
  * timestamp is assumed to be in local time.)
  *
  * Any leading or trailing space in @iso_date is ignored.
  *
  * Returns: %TRUE if the conversion was successful.
  *
  * Since: 2.12
  */
 gboolean
 g_time_val_from_iso8601 (const gchar *iso_date,
 			 GTimeVal    *time_)
 {
   struct tm tm = {0};
   long val;
   long mday, mon, year;
   long hour, min, sec;

   g_return_val_if_fail (iso_date != NULL, FALSE);
   g_return_val_if_fail (time_ != NULL, FALSE);

   /* Ensure that the first character is a digit, the first digit
    * of the date, otherwise we don't have an ISO 8601 date
    */
   while (g_ascii_isspace (*iso_date))
     iso_date++;

   if (*iso_date == '\0')
     return FALSE;

   if (!g_ascii_isdigit (*iso_date) && *iso_date != '+')
     return FALSE;

   val = strtoul (iso_date, (char **)&iso_date, 10);
   if (*iso_date == '-')
     {
       /* YYYY-MM-DD */
       year = val;
       iso_date++;

       mon = strtoul (iso_date, (char **)&iso_date, 10);
       if (*iso_date++ != '-')
         return FALSE;

       mday = strtoul (iso_date, (char **)&iso_date, 10);
     }
   else
     {
       /* YYYYMMDD */
       mday = val % 100;
       mon = (val % 10000) / 100;
       year = val / 10000;
     }

   /* Validation. */
   if (year < 1900 || year > G_MAXINT)
     return FALSE;
   if (mon < 1 || mon > 12)
     return FALSE;
   if (mday < 1 || mday > 31)
     return FALSE;

   tm.tm_mday = mday;
   tm.tm_mon = mon - 1;
   tm.tm_year = year - 1900;

   if (*iso_date != 'T')
     return FALSE;

   iso_date++;

   /* If there is a 'T' then there has to be a time */
   if (!g_ascii_isdigit (*iso_date))
     return FALSE;

   val = strtoul (iso_date, (char **)&iso_date, 10);
   if (*iso_date == ':')
     {
       /* hh:mm:ss */
       hour = val;
       iso_date++;
       min = strtoul (iso_date, (char **)&iso_date, 10);

       if (*iso_date++ != ':')
         return FALSE;

       sec = strtoul (iso_date, (char **)&iso_date, 10);
     }
   else
     {
       /* hhmmss */
       sec = val % 100;
       min = (val % 10000) / 100;
       hour = val / 10000;
     }

   /* Validation. Allow up to 2 leap seconds when validating @sec. */
   if (hour > 23)
     return FALSE;
   if (min > 59)
     return FALSE;
   if (sec > 61)
     return FALSE;

   tm.tm_hour = hour;
   tm.tm_min = min;
   tm.tm_sec = sec;

   time_->tv_usec = 0;

   if (*iso_date == ',' || *iso_date == '.')
     {
       glong mul = 100000;

       while (mul >= 1 && g_ascii_isdigit (*++iso_date))
         {
           time_->tv_usec += (*iso_date - '0') * mul;
           mul /= 10;
         }

       /* Skip any remaining digits after we’ve reached our limit of precision. */
       while (g_ascii_isdigit (*iso_date))
         iso_date++;
     }

   /* Now parse the offset and convert tm to a time_t */
   if (*iso_date == 'Z')
     {
       iso_date++;
       time_->tv_sec = mktime_utc (&tm);
     }
   else if (*iso_date == '+' || *iso_date == '-')
     {
       gint sign = (*iso_date == '+') ? -1 : 1;

       val = strtoul (iso_date + 1, (char **)&iso_date, 10);

       if (*iso_date == ':')
         {
           /* hh:mm */
           hour = val;
           min = strtoul (iso_date + 1, (char **)&iso_date, 10);
         }
       else
         {
           /* hhmm */
           hour = val / 100;
           min = val % 100;
         }

       if (hour > 99)
         return FALSE;
       if (min > 59)
         return FALSE;

       time_->tv_sec = mktime_utc (&tm) + (time_t) (60 * (gint64) (60 * hour + min) * sign);
     }
   else
     {
       /* No "Z" or offset, so local time */
       tm.tm_isdst = -1; /* locale selects DST */
       time_->tv_sec = mktime (&tm);
     }

   while (g_ascii_isspace (*iso_date))
     iso_date++;

   return *iso_date == '\0';
 }

 /**
  * g_time_val_to_iso8601:
  * @time_: a #GTimeVal
  *
  * Converts @time_ into an RFC 3339 encoded string, relative to the
  * Coordinated Universal Time (UTC). This is one of the many formats
  * allowed by ISO 8601.
  *
  * ISO 8601 allows a large number of date/time formats, with or without
  * punctuation and optional elements. The format returned by this function
  * is a complete date and time, with optional punctuation included, the
  * UTC time zone represented as "Z", and the @tv_usec part included if
  * and only if it is nonzero, i.e. either
  * "YYYY-MM-DDTHH:MM:SSZ" or "YYYY-MM-DDTHH:MM:SS.fffffZ".
  *
  * This corresponds to the Internet date/time format defined by
  * [RFC 3339](https://www.ietf.org/rfc/rfc3339.txt),
  * and to either of the two most-precise formats defined by
  * the W3C Note
  * [Date and Time Formats](http://www.w3.org/TR/NOTE-datetime-19980827).
  * Both of these documents are profiles of ISO 8601.
  *
  * Use g_date_time_format() or g_strdup_printf() if a different
  * variation of ISO 8601 format is required.
  *
  * If @time_ represents a date which is too large to fit into a `struct tm`,
  * %NULL will be returned. This is platform dependent, but it is safe to assume
  * years up to 3000 are supported. The return value of g_time_val_to_iso8601()
  * has been nullable since GLib 2.54; before then, GLib would crash under the
  * same conditions.
  *
  * Returns: (nullable): a newly allocated string containing an ISO 8601 date,
  *    or %NULL if @time_ was too large
  *
  * Since: 2.12
  */
 gchar *
 g_time_val_to_iso8601 (GTimeVal *time_)
 {
   gchar *retval;
   struct tm *tm;
 #ifdef HAVE_GMTIME_R
   struct tm tm_;
 #endif
   time_t secs;

   g_return_val_if_fail (time_->tv_usec >= 0 && time_->tv_usec < G_USEC_PER_SEC, NULL);

   secs = time_->tv_sec;
 #ifdef _WIN32
   tm = gmtime (&secs);
 #else
 #ifdef HAVE_GMTIME_R
   tm = gmtime_r (&secs, &tm_);
 #else
   tm = gmtime (&secs);
 #endif
 #endif

   /* If the gmtime() call has failed, time_->tv_sec is too big. */
   if (tm == NULL)
     return NULL;

   if (time_->tv_usec != 0)
     {
       /* ISO 8601 date and time format, with fractionary seconds:
        *   YYYY-MM-DDTHH:MM:SS.MMMMMMZ
        */
       retval = g_strdup_printf ("%4d-%02d-%02dT%02d:%02d:%02d.%06ldZ",
                                 tm->tm_year + 1900,
                                 tm->tm_mon + 1,
                                 tm->tm_mday,
                                 tm->tm_hour,
                                 tm->tm_min,
                                 tm->tm_sec,
                                 time_->tv_usec);
     }
   else
     {
       /* ISO 8601 date and time format:
        *   YYYY-MM-DDTHH:MM:SSZ
        */
       retval = g_strdup_printf ("%4d-%02d-%02dT%02d:%02d:%02dZ",
                                 tm->tm_year + 1900,
                                 tm->tm_mon + 1,
                                 tm->tm_mday,
                                 tm->tm_hour,
                                 tm->tm_min,
                                 tm->tm_sec);
     }

   return retval;
 }
	/* GLIB - Library of useful routines for C programming
	* Copyright (C) 1995-1997 Peter Mattis, Spencer Kimball and Josh MacDonald
	*
	* This 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.
	*
	* This 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 this library; if not, see <http://www.gnu.org/licenses/>.
	*/

	/*
	* Modified by the GLib Team and others 1997-2000. See the AUTHORS
	* file for a list of people on the GLib Team. See the ChangeLog
	* files for a list of changes. These files are distributed with
	* GLib at ftp://ftp.gtk.org/pub/gtk/.
	*/

	/*
	* MT safe
	*/

	#include "config.h"
	#include "glibconfig.h"

	#include <stdlib.h>

	#ifdef G_OS_UNIX
	#include <unistd.h>
	#endif /* G_OS_UNIX */

	#ifdef HAVE_SYS_TIME_H
	#include <sys/time.h>
	#endif
	#include <time.h>
	#ifndef G_OS_WIN32
	#include <errno.h>
	#endif /* G_OS_WIN32 */

	#ifdef G_OS_WIN32
	#include <windows.h>
	#endif /* G_OS_WIN32 */

	#include "gtimer.h"

	#include "gmem.h"
	#include "gstrfuncs.h"
	#include "gtestutils.h"
	#include "gmain.h"

	/**
	* SECTION:timers
	* @title: Timers
	* @short_description: keep track of elapsed time
	*
	* #GTimer records a start time, and counts microseconds elapsed since
	* that time. This is done somewhat differently on different platforms,
	* and can be tricky to get exactly right, so #GTimer provides a
	* portable/convenient interface.
	**/

	/**
	* GTimer:
	*
	* Opaque datatype that records a start time.
	**/
	struct _GTimer
	{
	guint64 start;
	guint64 end;

	guint active : 1;
	};

	/**
	* g_timer_new:
	*
	* Creates a new timer, and starts timing (i.e. g_timer_start() is
	* implicitly called for you).
	*
	* Returns: a new #GTimer.
	**/
	GTimer*
	g_timer_new (void)
	{
	GTimer *timer;

	timer = g_new (GTimer, 1);
	timer->active = TRUE;

	timer->start = g_get_monotonic_time ();

	return timer;
	}

	/**
	* g_timer_destroy:
	* @timer: a #GTimer to destroy.
	*
	* Destroys a timer, freeing associated resources.
	**/
	void
	g_timer_destroy (GTimer *timer)
	{
	g_return_if_fail (timer != NULL);

	g_free (timer);
	}

	/**
	* g_timer_start:
	* @timer: a #GTimer.
	*
	* Marks a start time, so that future calls to g_timer_elapsed() will
	* report the time since g_timer_start() was called. g_timer_new()
	* automatically marks the start time, so no need to call
	* g_timer_start() immediately after creating the timer.
	**/
	void
	g_timer_start (GTimer *timer)
	{
	g_return_if_fail (timer != NULL);

	timer->active = TRUE;

	timer->start = g_get_monotonic_time ();
	}

	/**
	* g_timer_stop:
	* @timer: a #GTimer.
	*
	* Marks an end time, so calls to g_timer_elapsed() will return the
	* difference between this end time and the start time.
	**/
	void
	g_timer_stop (GTimer *timer)
	{
	g_return_if_fail (timer != NULL);

	timer->active = FALSE;

	timer->end = g_get_monotonic_time ();
	}

	/**
	* g_timer_reset:
	* @timer: a #GTimer.
	*
	* This function is useless; it's fine to call g_timer_start() on an
	* already-started timer to reset the start time, so g_timer_reset()
	* serves no purpose.
	**/
	void
	g_timer_reset (GTimer *timer)
	{
	g_return_if_fail (timer != NULL);

	timer->start = g_get_monotonic_time ();
	}

	/**
	* g_timer_continue:
	* @timer: a #GTimer.
	*
	* Resumes a timer that has previously been stopped with
	* g_timer_stop(). g_timer_stop() must be called before using this
	* function.
	*
	* Since: 2.4
	**/
	void
	g_timer_continue (GTimer *timer)
	{
	guint64 elapsed;

	g_return_if_fail (timer != NULL);
	g_return_if_fail (timer->active == FALSE);

	/* Get elapsed time and reset timer start time
	* to the current time minus the previously
	* elapsed interval.
	*/

	elapsed = timer->end - timer->start;

	timer->start = g_get_monotonic_time ();

	timer->start -= elapsed;

	timer->active = TRUE;
	}

	/**
	* g_timer_elapsed:
	* @timer: a #GTimer.
	* @microseconds: return location for the fractional part of seconds
	* elapsed, in microseconds (that is, the total number
	* of microseconds elapsed, modulo 1000000), or %NULL
	*
	* If @timer has been started but not stopped, obtains the time since
	* the timer was started. If @timer has been stopped, obtains the
	* elapsed time between the time it was started and the time it was
	* stopped. The return value is the number of seconds elapsed,
	* including any fractional part. The @microseconds out parameter is
	* essentially useless.
	*
	* Returns: seconds elapsed as a floating point value, including any
	* fractional part.
	**/
	gdouble
	g_timer_elapsed (GTimer *timer,
	gulong *microseconds)
	{
	gdouble total;
	gint64 elapsed;

	g_return_val_if_fail (timer != NULL, 0);

	if (timer->active)
	timer->end = g_get_monotonic_time ();

	elapsed = timer->end - timer->start;

	total = elapsed / 1e6;

	if (microseconds)
	*microseconds = elapsed % 1000000;

	return total;
	}

	/**
	* g_usleep:
	* @microseconds: number of microseconds to pause
	*
	* Pauses the current thread for the given number of microseconds.
	*
	* There are 1 million microseconds per second (represented by the
	* #G_USEC_PER_SEC macro). g_usleep() may have limited precision,
	* depending on hardware and operating system; don't rely on the exact
	* length of the sleep.
	*/
	void
	g_usleep (gulong microseconds)
	{
	#ifdef G_OS_WIN32
	/* Round up to the next millisecond */
	Sleep (microseconds ? (1 + (microseconds - 1) / 1000) : 0);
	#else
	struct timespec request, remaining;
	request.tv_sec = microseconds / G_USEC_PER_SEC;
	request.tv_nsec = 1000 * (microseconds % G_USEC_PER_SEC);
	while (nanosleep (&request, &remaining) == -1 && errno == EINTR)
	request = remaining;
	#endif
	}

	/**
	* g_time_val_add:
	* @time_: a #GTimeVal
	* @microseconds: number of microseconds to add to @time
	*
	* Adds the given number of microseconds to @time_. @microseconds can
	* also be negative to decrease the value of @time_.
	**/
	void
	g_time_val_add (GTimeVal *time_, glong microseconds)
	{
	g_return_if_fail (time_->tv_usec >= 0 && time_->tv_usec < G_USEC_PER_SEC);

	if (microseconds >= 0)
	{
	time_->tv_usec += microseconds % G_USEC_PER_SEC;
	time_->tv_sec += microseconds / G_USEC_PER_SEC;
	if (time_->tv_usec >= G_USEC_PER_SEC)
	{
	time_->tv_usec -= G_USEC_PER_SEC;
	time_->tv_sec++;
	}
	}
	else
	{
	microseconds *= -1;
	time_->tv_usec -= microseconds % G_USEC_PER_SEC;
	time_->tv_sec -= microseconds / G_USEC_PER_SEC;
	if (time_->tv_usec < 0)
	{
	time_->tv_usec += G_USEC_PER_SEC;
	time_->tv_sec--;
	}
	}
	}

	/* converts a broken down date representation, relative to UTC,
	* to a timestamp; it uses timegm() if it's available.
	*/
	static time_t
	mktime_utc (struct tm *tm)
	{
	time_t retval;

	#ifndef HAVE_TIMEGM
	static const gint days_before[] =
	{
	0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334
	};
	#endif

	#ifndef HAVE_TIMEGM
	if (tm->tm_mon < 0 \|\| tm->tm_mon > 11)
	return (time_t) -1;

	retval = (tm->tm_year - 70) * 365;
	retval += (tm->tm_year - 68) / 4;
	retval += days_before[tm->tm_mon] + tm->tm_mday - 1;

	if (tm->tm_year % 4 == 0 && tm->tm_mon < 2)
	retval -= 1;

	retval = ((((retval * 24) + tm->tm_hour) * 60) + tm->tm_min) * 60 + tm->tm_sec;
	#else
	retval = timegm (tm);
	#endif /* !HAVE_TIMEGM */

	return retval;
	}

	/**
	* g_time_val_from_iso8601:
	* @iso_date: an ISO 8601 encoded date string
	* @time_: (out): a #GTimeVal
	*
	* Converts a string containing an ISO 8601 encoded date and time
	* to a #GTimeVal and puts it into @time_.
	*
	* @iso_date must include year, month, day, hours, minutes, and
	* seconds. It can optionally include fractions of a second and a time
	* zone indicator. (In the absence of any time zone indication, the
	* timestamp is assumed to be in local time.)
	*
	* Any leading or trailing space in @iso_date is ignored.
	*
	* Returns: %TRUE if the conversion was successful.
	*
	* Since: 2.12
	*/
	gboolean
	g_time_val_from_iso8601 (const gchar *iso_date,
	GTimeVal *time_)
	{
	struct tm tm = {0};
	long val;
	long mday, mon, year;
	long hour, min, sec;

	g_return_val_if_fail (iso_date != NULL, FALSE);
	g_return_val_if_fail (time_ != NULL, FALSE);

	/* Ensure that the first character is a digit, the first digit
	* of the date, otherwise we don't have an ISO 8601 date
	*/
	while (g_ascii_isspace (*iso_date))
	iso_date++;

	if (*iso_date == '\0')
	return FALSE;

	if (!g_ascii_isdigit (iso_date) && iso_date != '+')
	return FALSE;

	val = strtoul (iso_date, (char **)&iso_date, 10);
	if (*iso_date == '-')
	{
	/* YYYY-MM-DD */
	year = val;
	iso_date++;

	mon = strtoul (iso_date, (char **)&iso_date, 10);
	if (*iso_date++ != '-')
	return FALSE;

	mday = strtoul (iso_date, (char **)&iso_date, 10);
	}
	else
	{
	/* YYYYMMDD */
	mday = val % 100;
	mon = (val % 10000) / 100;
	year = val / 10000;
	}

	/* Validation. */
	if (year < 1900 \|\| year > G_MAXINT)
	return FALSE;
	if (mon < 1 \|\| mon > 12)
	return FALSE;
	if (mday < 1 \|\| mday > 31)
	return FALSE;

	tm.tm_mday = mday;
	tm.tm_mon = mon - 1;
	tm.tm_year = year - 1900;

	if (*iso_date != 'T')
	return FALSE;

	iso_date++;

	/* If there is a 'T' then there has to be a time */
	if (!g_ascii_isdigit (*iso_date))
	return FALSE;

	val = strtoul (iso_date, (char **)&iso_date, 10);
	if (*iso_date == ':')
	{
	/* hh:mm:ss */
	hour = val;
	iso_date++;
	min = strtoul (iso_date, (char **)&iso_date, 10);

	if (*iso_date++ != ':')
	return FALSE;

	sec = strtoul (iso_date, (char **)&iso_date, 10);
	}
	else
	{
	/* hhmmss */
	sec = val % 100;
	min = (val % 10000) / 100;
	hour = val / 10000;
	}

	/* Validation. Allow up to 2 leap seconds when validating @sec. */
	if (hour > 23)
	return FALSE;
	if (min > 59)
	return FALSE;
	if (sec > 61)
	return FALSE;

	tm.tm_hour = hour;
	tm.tm_min = min;
	tm.tm_sec = sec;

	time_->tv_usec = 0;

	if (iso_date == ',' \|\| iso_date == '.')
	{
	glong mul = 100000;

	while (mul >= 1 && g_ascii_isdigit (*++iso_date))
	{
	time_->tv_usec += (iso_date - '0') mul;
	mul /= 10;
	}

	/* Skip any remaining digits after we’ve reached our limit of precision. */
	while (g_ascii_isdigit (*iso_date))
	iso_date++;
	}

	/* Now parse the offset and convert tm to a time_t */
	if (*iso_date == 'Z')
	{
	iso_date++;
	time_->tv_sec = mktime_utc (&tm);
	}
	else if (iso_date == '+' \|\| iso_date == '-')
	{
	gint sign = (*iso_date == '+') ? -1 : 1;

	val = strtoul (iso_date + 1, (char **)&iso_date, 10);

	if (*iso_date == ':')
	{
	/* hh:mm */
	hour = val;
	min = strtoul (iso_date + 1, (char **)&iso_date, 10);
	}
	else
	{
	/* hhmm */
	hour = val / 100;
	min = val % 100;
	}

	if (hour > 99)
	return FALSE;
	if (min > 59)
	return FALSE;

	time_->tv_sec = mktime_utc (&tm) + (time_t) (60 * (gint64) (60 * hour + min) * sign);
	}
	else
	{
	/* No "Z" or offset, so local time */
	tm.tm_isdst = -1; /* locale selects DST */
	time_->tv_sec = mktime (&tm);
	}

	while (g_ascii_isspace (*iso_date))
	iso_date++;

	return *iso_date == '\0';
	}

	/**
	* g_time_val_to_iso8601:
	* @time_: a #GTimeVal
	*
	* Converts @time_ into an RFC 3339 encoded string, relative to the
	* Coordinated Universal Time (UTC). This is one of the many formats
	* allowed by ISO 8601.
	*
	* ISO 8601 allows a large number of date/time formats, with or without
	* punctuation and optional elements. The format returned by this function
	* is a complete date and time, with optional punctuation included, the
	* UTC time zone represented as "Z", and the @tv_usec part included if
	* and only if it is nonzero, i.e. either
	* "YYYY-MM-DDTHH:MM:SSZ" or "YYYY-MM-DDTHH:MM:SS.fffffZ".
	*
	* This corresponds to the Internet date/time format defined by
	* [RFC 3339](https://www.ietf.org/rfc/rfc3339.txt),
	* and to either of the two most-precise formats defined by
	* the W3C Note
	* [Date and Time Formats](http://www.w3.org/TR/NOTE-datetime-19980827).
	* Both of these documents are profiles of ISO 8601.
	*
	* Use g_date_time_format() or g_strdup_printf() if a different
	* variation of ISO 8601 format is required.
	*
	* If @time_ represents a date which is too large to fit into a `struct tm`,
	* %NULL will be returned. This is platform dependent, but it is safe to assume
	* years up to 3000 are supported. The return value of g_time_val_to_iso8601()
	* has been nullable since GLib 2.54; before then, GLib would crash under the
	* same conditions.
	*
	* Returns: (nullable): a newly allocated string containing an ISO 8601 date,
	* or %NULL if @time_ was too large
	*
	* Since: 2.12
	*/
	gchar *
	g_time_val_to_iso8601 (GTimeVal *time_)
	{
	gchar *retval;
	struct tm *tm;
	#ifdef HAVE_GMTIME_R
	struct tm tm_;
	#endif
	time_t secs;

	g_return_val_if_fail (time_->tv_usec >= 0 && time_->tv_usec < G_USEC_PER_SEC, NULL);

	secs = time_->tv_sec;
	#ifdef _WIN32
	tm = gmtime (&secs);
	#else
	#ifdef HAVE_GMTIME_R
	tm = gmtime_r (&secs, &tm_);
	#else
	tm = gmtime (&secs);
	#endif
	#endif

	/* If the gmtime() call has failed, time_->tv_sec is too big. */
	if (tm == NULL)
	return NULL;

	if (time_->tv_usec != 0)
	{
	/* ISO 8601 date and time format, with fractionary seconds:
	* YYYY-MM-DDTHH:MM:SS.MMMMMMZ
	*/
	retval = g_strdup_printf ("%4d-%02d-%02dT%02d:%02d:%02d.%06ldZ",
	tm->tm_year + 1900,
	tm->tm_mon + 1,
	tm->tm_mday,
	tm->tm_hour,
	tm->tm_min,
	tm->tm_sec,
	time_->tv_usec);
	}
	else
	{
	/* ISO 8601 date and time format:
	* YYYY-MM-DDTHH:MM:SSZ
	*/
	retval = g_strdup_printf ("%4d-%02d-%02dT%02d:%02d:%02dZ",
	tm->tm_year + 1900,
	tm->tm_mon + 1,
	tm->tm_mday,
	tm->tm_hour,
	tm->tm_min,
	tm->tm_sec);
	}

	return retval;
	}