Support for monotime

Provide `monotime` function with at least 1 millisecond resolution.

1 files changed, 66 insertions, 0 deletions

diff --git a/src/time_osx.h b/src/time_osx.h
new file mode 100644
index 0000000..3308318
--- /dev/null
+++ b/src/time_osx.h
@@ -0,0 +1,66 @@
+#ifndef TIME_OSX_H
+#define TIME_OSX_H
+
+/*
+ * clock_gettime()
+ *
+ * OS X doesn't implement the clock_gettime() POSIX interface, but does
+ * provide a monotonic clock through mach_absolute_time(). On i386 and
+ * x86_64 architectures this clock is in nanosecond units, but not so on
+ * other devices. mach_timebase_info() provides the conversion parameters.
+ *
+ */
+
+#include <time.h>            /* struct timespec */
+#include <errno.h>           /* errno EINVAL */
+#include <sys/time.h>        /* TIMEVAL_TO_TIMESPEC struct timeval gettimeofday(3) */
+#include <mach/mach_time.h>  /* mach_timebase_info_data_t mach_timebase_info() mach_absolute_time() */
+
+
+#define CLOCK_REALTIME  0
+#define CLOCK_VIRTUAL   1
+#define CLOCK_PROF      2
+#define CLOCK_MONOTONIC 3
+
+static mach_timebase_info_data_t clock_timebase = {
+    .numer = 1, .denom = 1,
+}; /* clock_timebase */
+
+void clock_gettime_init(void) __attribute__((constructor));
+
+void clock_gettime_init(void) {
+    if (mach_timebase_info(&clock_timebase) != KERN_SUCCESS)
+        __builtin_abort();
+} /* clock_gettime_init() */
+
+static int clock_gettime(int clockid, struct timespec *ts) {
+    switch (clockid) {
+    case CLOCK_REALTIME: {
+        struct timeval tv;
+
+        if (0 != gettimeofday(&tv, 0))
+        return -1;
+
+        TIMEVAL_TO_TIMESPEC(&tv, ts);
+
+        return 0;
+    }
+    case CLOCK_MONOTONIC: {
+        unsigned long long abt;
+
+        abt = mach_absolute_time();
+        abt = abt * clock_timebase.numer / clock_timebase.denom;
+
+        ts->tv_sec = abt / 1000000000UL;
+        ts->tv_nsec = abt % 1000000000UL;
+
+        return 0;
+    }
+    default:
+        errno = EINVAL;
+
+        return -1;
+    } /* switch() */
+} /* clock_gettime() */
+
+#endif /* TIME_OSX_H */