+/* Sleep long enough to notice a timestamp difference on the file
+ system in the current directory. */
+static void
+nap (void)
+{
+#if !HAVE_USLEEP
+ /* Assume the worst case file system of FAT, which has a granularity
+ of 2 seconds. */
+ sleep (2);
+#else /* HAVE_USLEEP */
+ static long delay;
+ if (!delay)
+ {
+ /* Initialize only once, by sleeping for 20 milliseconds (needed
+ since xfs has a quantization of about 10 milliseconds, even
+ though it has a granularity of 1 nanosecond, and since NTFS
+ has a default quantization of 15.25 milliseconds, even though
+ it has a granularity of 100 nanoseconds). If the seconds
+ differ, repeat the test one more time (in case we crossed a
+ quantization boundary on a file system with 1 second
+ resolution). If we can't observe a difference in only the
+ nanoseconds, then fall back to 2 seconds. However, note that
+ usleep (2000000) is allowed to fail with EINVAL. */
+ struct stat st1;
+ struct stat st2;
+ ASSERT (stat ("t-stt-stamp1", &st1) == 0);
+ ASSERT (force_unlink ("t-stt-stamp1") == 0);
+ delay = 20000;
+ usleep (delay);
+ create_file ("t-stt-stamp1");
+ ASSERT (stat ("t-stt-stamp1", &st2) == 0);
+ if (st1.st_mtime != st2.st_mtime)
+ {
+ /* Seconds differ, give it one more shot. */
+ st1 = st2;
+ ASSERT (force_unlink ("t-stt-stamp1") == 0);
+ usleep (delay);
+ create_file ("t-stt-stamp1");
+ ASSERT (stat ("t-stt-stamp1", &st2) == 0);
+ }
+ if (! (st1.st_mtime == st2.st_mtime
+ && get_stat_mtime_ns (&st1) < get_stat_mtime_ns (&st2)))
+ delay = 2000000;
+ }
+ if (delay == 2000000)
+ sleep (2);
+ else
+ usleep (delay);
+#endif /* HAVE_USLEEP */
+}
+