mach_absolute_time to seconds in Swift

machAbsoluteToSeconds.swift

var timebaseInfo = mach_timebase_info_data_t()

init() {
  mach_timebase_info(&timebaseInfo)
}

func machAbsoluteToSeconds(machAbsolute: UInt64 = mach_absolute_time()) -> Double {
  let nanos = Double(machAbsolute * UInt64(timebaseInfo.numer)) / Double(timebaseInfo.denom)
  return nanos / 1.0e9;
}