Swift で CPU の使用率を表示する

CpuUsage.swift

#! /usr/bin/xcrun swift

import Cocoa

let host_port = mach_host_self()
var prev_cpu_load = host_cpu_load_info_data_t()
var cpu_load = host_cpu_load_info_data_t()
var count = mach_msg_type_number_t(MemoryLayout<host_cpu_load_info_data_t>.size / MemoryLayout<integer_t>.size)
var user : natural_t
var system : natural_t
var idle : natural_t
let cpu_usage = {(cpu_load_info : host_cpu_load_info_data_t) -> host_cpu_load_info_data_t in
	var load_info = cpu_load_info
	return withUnsafePointer(to: &load_info) { (pointer : UnsafePointer<host_cpu_load_info_data_t>) -> host_cpu_load_info_data_t in
    	let raw = OpaquePointer(pointer)
    	let host_info = host_info_t(raw)
    	host_statistics(host_port, HOST_CPU_LOAD_INFO, host_info, &count);

    	return pointer.pointee
	}
}

prev_cpu_load = cpu_usage(prev_cpu_load)

while true {
	sleep(1)
    cpu_load = cpu_usage(cpu_load)

    user = cpu_load.cpu_ticks.0 - prev_cpu_load.cpu_ticks.0;
    system = cpu_load.cpu_ticks.1 - prev_cpu_load.cpu_ticks.1;
    idle = cpu_load.cpu_ticks.2 - prev_cpu_load.cpu_ticks.2;

    print((Double)(user + system) / (Double)(system + user + idle) * 100.0)

    prev_cpu_load = cpu_load;
}