+ 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);