mach/mach_time.h

Returns the scale factor used to convert mach absolute time units to nanoseconds, as a numerator/denominator pair: nanoseconds = ticks * numer / denom. Applies to values from mach_absolute_time, mach_approximate_time, mach_continuous_time, and deadlines passed to mach_wait_until. The result of mach_timebase_info_trap is cached in the library after the first successful call. Returns KERN_SUCCESS, or the trap's error if the first query fails.

Suspends execution of the calling thread until the specified deadline, expressed in mach absolute time units (the mach_absolute_time timebase), has passed. A deadline already in the past returns immediately. The wait uses standard user timeout urgency with no additional leeway and is abort-safe: KERN_ABORTED is returned if the wait is interrupted (e.g. thread_abort), otherwise KERN_SUCCESS. Because the deadline is on the mach_absolute_time clock, time the system spends asleep does not count toward it; use continuous-time based waits when sleep must be included.

Returns the current value of the system's monotonic clock in mach absolute time units (ticks); convert to nanoseconds with the fraction returned by mach_timebase_info. Implemented in the commpage from the hardware time base without a system call. The value increases monotonically, starts near zero at boot, and is unaffected by calendar clock adjustments, but it does not include time the system spends asleep: mach_continuous_time is defined in the kernel as mach_absolute_time plus the accumulated sleep time (mach_absolutetime_asleep), so intervals measured with mach_absolute_time exclude sleep while mach_continuous_time intervals include it. Values are meaningful only within a single boot session.

Returns an approximation of mach_absolute_time, in the same mach absolute time units. When the commpage advertises APPROX_TIME_SUPPORTED, the value is read from a periodically updated commpage field, avoiding the cost of reading the hardware time base; the result may therefore lag the precise clock slightly. On configurations without commpage support the call falls back to mach_absolute_time exactly. Like mach_absolute_time, the clock does not advance while the system is asleep; mach_continuous_approximate_time is the variant that does.