+#ifdef __APPLE__
+
+#ifndef CLOCK_MONOTONIC
+ #define CLOCK_MONOTONIC (1)
+#endif
+#ifndef CLOCK_REALTIME
+ #define CLOCK_REALTIME (2)
+#endif
+
+ #include <sys/time.h>
+ #include <mach/clock.h>
+ #include <mach/mach.h>
+ #include <mach/mach_time.h>
+
+ /* clock_gettime is not implemented on OSX prior to 10.12 */
+ int _civet_clock_gettime(int clk_id, struct timespec *t);
+
+ int _civet_clock_gettime(int clk_id, struct timespec *t)
+ {
+ memset(t, 0, sizeof(*t));
+ if (clk_id == CLOCK_REALTIME) {
+ struct timeval now;
+ int rv = gettimeofday(&now, NULL);
+ if (rv) {
+ return rv;
+ }
+ t->tv_sec = now.tv_sec;
+ t->tv_nsec = now.tv_usec * 1000;
+ return 0;
+
+ } else if (clk_id == CLOCK_MONOTONIC) {
+ static uint64_t clock_start_time = 0;
+ static mach_timebase_info_data_t timebase_info = {0, 0};
+
+ uint64_t now = mach_absolute_time();
+
+ if (clock_start_time == 0) {
+ mach_timebase_info(&timebase_info);
+ clock_start_time = now;
+ }
+
+ now = (uint64_t)((double)(now - clock_start_time)
+ * (double)timebase_info.numer
+ / (double)timebase_info.denom);
+
+ t->tv_sec = now / 1000000000;
+ t->tv_nsec = now % 1000000000;
+ return 0;
+ }
+ return -1; // EINVAL - Clock ID is unknown
+ }
+
+ /* if clock_gettime is declared, then __CLOCK_AVAILABILITY will be defined */
+ #ifdef __CLOCK_AVAILABILITY
+ /* If we compiled with Mac OSX 10.12 or later, then clock_gettime will be declared
+ * but it may be NULL at runtime. So we need to check before using it. */
+ int _civet_safe_clock_gettime(int clk_id, struct timespec *t);
+
+ int _civet_safe_clock_gettime(int clk_id, struct timespec *t) {
+ if( clock_gettime ) {
+ return clock_gettime(clk_id, t);
+ }
+ return _civet_clock_gettime(clk_id, t);
+ }
+ #define clock_gettime _civet_safe_clock_gettime
+ #else
+ #define clock_gettime _civet_clock_gettime
+ #endif
+
+#endif
+
+