在Swift中使用libevent和GCD(libdispatch)

这就是我想出的：

var terminated = false

DispatchQueue.main.after(when: DispatchTime.now() + 3) {
    print("Dispatch works!")
    terminated = true
}

while !terminated {
    switch event_base_loop(eventBase,EVLOOP_NONBLOCK) { // libevent
    case 1:
        break // No events were processed
    case 0:
        print("DEBUG: Libevent processed one or more events")
    default: // -1
        print("Unhandled error in network backend")
        exit(1)
    }
    RunLoop.current().run(mode: RunLoopMode.defaultRunLoopMode,before: Date(timeIntervalSinceNow: 0.01))
}

这有效,但引入了0.01秒的延迟.当RunLoop正在休眠时,libevent将无法处理事件.当应用程序空闲时,降低此超时会显着增加CPU使用率.

我也在考虑只使用libevent,但是项目中的第三方库可以在内部使用dispatch_async,因此这可能会有问题.

在另一个线程中运行libevent的循环会使同步变得更加复杂,这是解决此延迟问题的唯一方法吗？

LINUX更新.上面的代码在Linux上不起作用(2016-07-25-a Swift snapshot),RunLoop.current().run存在但有错误.下面是一个有效的Linux版本,用timer和dispatch_main重新实现.它遇到了相同的延迟问题：

let queue = dispatch_get_main_queue()
let timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER,queue)
let interval = 0.01
let block: () -> () = {
    guard !terminated else {
        print("Quitting")
        exit(0)
    }
    switch server.loop() {
    case 1: break // Just idling
    case 0: break //print("Libevent: processed event(s)")
    default: // -1
        print("Unhandled error in network backend")
        exit(1)
    }
}
block()
let fireTime = dispatch_time(DISPATCH_TIME_NOW,Int64(interval * Double(NSEC_PER_SEC)))
dispatch_source_set_timer(timer,fireTime,UInt64(interval * Double(NSEC_PER_SEC)),UInt64(NSEC_PER_SEC) / 10)
dispatch_source_set_event_handler(timer,block)
dispatch_resume(timer)
dispatch_main()