Measure on Darwin Match

measure.swift

func measure(_ name: String, _ block: () -> Void) {
    let machToSeconds: Double = {
        var timebase: mach_timebase_info_data_t = mach_timebase_info_data_t()
        mach_timebase_info(&timebase)
        return Double(timebase.numer) / Double(timebase.denom) * 1e-9
    }()

    let startTime = mach_absolute_time()
    block()
    let endTime = mach_absolute_time()
    print(name, (machToSeconds * Double(endTime - startTime)))
}