+#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. */
+ verify (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;
+ intermediate.tv_nsec = requested_delay->tv_nsec;
+
+ 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 __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
+/* Unix platforms lacking nanosleep. */