+#if defined (HAVE_CLOCK_NANOSLEEP)
+static unsigned prec = 0;
+
+static void mprec_once( void )
+{
+ struct timespec ts;
+ if( clock_getres( CLOCK_MONOTONIC, &ts ))
+ clock_getres( CLOCK_REALTIME, &ts );
+
+ prec = ts.tv_nsec / 1000;
+}
+#endif
+
+/**
+ * Return a value that is no bigger than the clock precision
+ * (possibly zero).
+ */
+static inline unsigned mprec( void )
+{
+#if defined (HAVE_CLOCK_NANOSLEEP)
+ static pthread_once_t once = PTHREAD_ONCE_INIT;
+ pthread_once( &once, mprec_once );
+ return prec;
+#else
+ return 0;
+#endif
+}
+
+#ifdef USE_APPLE_MACH
+static mach_timebase_info_data_t mtime_timebase_info;
+static pthread_once_t mtime_timebase_info_once = PTHREAD_ONCE_INIT;
+static void mtime_init_timebase(void)
+{
+ mach_timebase_info(&mtime_timebase_info);
+}
+#endif