/* Provide a replacement for the POSIX nanosleep function.

   Copyright (C) 1999-2000, 2002, 2004-2025 Free Software Foundation, Inc.

   This file 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 file 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 program.  If not, see <https://www.gnu.org/licenses/>.  */

/* written by Jim Meyering

   and Bruno Haible for the native Windows part */

#include <config.h>

#include <time.h>

#include "intprops.h"

#include <stdio.h>

#include <sys/types.h>

#include <sys/select.h>

#include <signal.h>

#include <errno.h>

#include <unistd.h>

enum { BILLION = 1000 * 1000 * 1000 };

#if HAVE_BUG_BIG_NANOSLEEP

int

nanosleep (const struct timespec *requested_delay,

           struct timespec *remaining_delay)

# undef nanosleep

{

  /* nanosleep mishandles large sleeps due to internal overflow problems.

     The worst known case of this is Linux 2.6.9 with glibc 2.3.4, which

     can't sleep more than 24.85 days (2^31 milliseconds).  Similarly,

     cygwin 1.5.x, which can't sleep more than 49.7 days (2^32 milliseconds).

     Solve this by breaking the sleep up into smaller chunks.  */

  if (requested_delay->tv_nsec < 0 || BILLION <= requested_delay->tv_nsec)

    {

      errno = EINVAL;

      return -1;

    }

  {

    /* Verify that time_t is large enough.  */

    static_assert (TYPE_MAXIMUM (time_t) / 24 / 24 / 60 / 60);

    const time_t limit = 24 * 24 * 60 * 60;

    time_t seconds = requested_delay->tv_sec;

    struct timespec intermediate = *requested_delay;

    while (limit < seconds)

      {

        int result;

        intermediate.tv_sec = limit;

        result = nanosleep (&intermediate, remaining_delay);

        seconds -= limit;

        if (result)

          {

            if (remaining_delay)

              remaining_delay->tv_sec += seconds;

            return result;

          }

        intermediate.tv_nsec = 0;

      }

    intermediate.tv_sec = seconds;

    return nanosleep (&intermediate, remaining_delay);

  }

}

#elif defined _WIN32 && ! defined __CYGWIN__

/* Native Windows platforms.  */

# define WIN32_LEAN_AND_MEAN

# include <windows.h>

/* The Windows API function Sleep() has a resolution of about 15 ms and takes

   at least 5 ms to execute.  We use this function for longer time periods.

   Additionally, we use busy-looping over short time periods, to get a

   resolution of about 0.01 ms.  In order to measure such short timespans,

   we use the QueryPerformanceCounter() function.  */

int

nanosleep (const struct timespec *requested_delay,

           struct timespec *remaining_delay)

{

  static bool initialized;

  /* Number of performance counter increments per nanosecond,

     or zero if it could not be determined.  */

  static double ticks_per_nanosecond;

  if (requested_delay->tv_nsec < 0 || BILLION <= requested_delay->tv_nsec)

    {

      errno = EINVAL;

      return -1;

    }

  /* For requested delays of one second or more, 15ms resolution is

     sufficient.  */

  if (requested_delay->tv_sec == 0)

    {

      if (!initialized)

        {

          /* Initialize ticks_per_nanosecond.  */

          LARGE_INTEGER ticks_per_second;

          if (QueryPerformanceFrequency (&ticks_per_second))

            ticks_per_nanosecond =

              (double) ticks_per_second.QuadPart / 1000000000.0;

          initialized = true;

        }

      if (ticks_per_nanosecond)

        {

          /* QueryPerformanceFrequency worked.  We can use

             QueryPerformanceCounter.  Use a combination of Sleep and

             busy-looping.  */

          /* Number of milliseconds to pass to the Sleep function.

             Since Sleep can take up to 8 ms less or 8 ms more than requested

             (or maybe more if the system is loaded), we subtract 10 ms.  */

          int sleep_millis = (int) requested_delay->tv_nsec / 1000000 - 10;

          /* Determine how many ticks to delay.  */

          LONGLONG wait_ticks = requested_delay->tv_nsec * ticks_per_nanosecond;

          /* Start.  */

          LARGE_INTEGER counter_before;

          if (QueryPerformanceCounter (&counter_before))

            {

              /* Wait until the performance counter has reached this value.

                 We don't need to worry about overflow, because the performance

                 counter is reset at reboot, and with a frequency of 3.6E6

                 ticks per second 63 bits suffice for over 80000 years.  */

              LONGLONG wait_until = counter_before.QuadPart + wait_ticks;

              /* Use Sleep for the longest part.  */

              if (sleep_millis > 0)

                Sleep (sleep_millis);

              /* Busy-loop for the rest.  */

              for (;;)

                {

                  LARGE_INTEGER counter_after;

                  if (!QueryPerformanceCounter (&counter_after))

                    /* QueryPerformanceCounter failed, but succeeded earlier.

                       Should not happen.  */

                    break;

                  if (counter_after.QuadPart >= wait_until)

                    /* The requested time has elapsed.  */

                    break;

                }

              goto done;

            }

        }

    }

  /* Implementation for long delays and as fallback.  */

  Sleep (requested_delay->tv_sec * 1000 + requested_delay->tv_nsec / 1000000);

 done:

  /* Sleep is not interruptible.  So there is no remaining delay.  */

  if (remaining_delay != NULL)

    {

      remaining_delay->tv_sec = 0;

      remaining_delay->tv_nsec = 0;

    }

  return 0;

}

#else

/* Other platforms lacking nanosleep.

   It's not clear whether these are still practical porting targets.

   For now, just fall back on pselect.  */

/* Suspend execution for at least *REQUESTED_DELAY seconds.  The

   *REMAINING_DELAY part isn't implemented yet.  */

int

nanosleep (const struct timespec *requested_delay,

           struct timespec *remaining_delay)

{

  return pselect (0, NULL, NULL, NULL, requested_delay, NULL);

}

#endif