RunLoop伪代码

static int32_t __CFRunLoopRun(CFRunLoopRef rl, CFRunLoopModeRef rlm, CFTimeInterval seconds, Boolean stopAfterHandle, CFRunLoopModeRef previousMode) {
    //通知Observer：即将处理Timers事件
     __CFRunLoopDoObservers(rl, rlm, kCFRunLoopBeforeTimers);
     //通知Observer：即将处理Sources事件
     __CFRunLoopDoObservers(rl, rlm, kCFRunLoopBeforeSources);
    //处理Blocks
	__CFRunLoopDoBlocks(rl, rlm);
    //处理Sources0 通过处理结果来判断是否需要再次执行Blocks
    Boolean sourceHandledThisLoop = __CFRunLoopDoSources0(rl, rlm, stopAfterHandle);
    if (sourceHandledThisLoop) {
            __CFRunLoopDoBlocks(rl, rlm);
	}
    //判断Sources1（MachPort为Sources1），如果有事件，直接跳转到handle_msg
    if (__CFRunLoopServiceMachPort(dispatchPort, &msg, sizeof(msg_buffer), 0)) {
        goto handle_msg;
    }
    //通知Observer：即将进入休眠
	__CFRunLoopDoObservers(rl, rlm, kCFRunLoopBeforeWaiting);
    //开始休眠，等待其他消息唤醒
	__CFRunLoopSetSleeping(rl);
    __CFPortSetInsert(dispatchPort, waitSet);
        __CFRunLoopServiceMachPort(waitSet, &msg, sizeof(msg_buffer), poll ? 0 : TIMEOUT_INFINITY);

    //醒来了
    __CFPortSetRemove(dispatchPort, waitSet);
	__CFRunLoopUnsetSleeping(rl);
    //通知Observer：已经唤醒
	__CFRunLoopDoObservers(rl, rlm, kCFRunLoopAfterWaiting);

        handle_msg:;   //看是谁唤醒RunLoop，进行相应的处理
        mach_port_t livePort = msg ? msg->msgh_local_port : MACH_PORT_NULL;

        if (MACH_PORT_NULL == livePort) {
            // handle nothing
        } else if (livePort == rl->_wakeUpPort) {
            // do nothing on Mac OS

        } else if (livePort == rlm->_timerPort) {    //被Timer唤醒，处理Timers事件

	    __CFRunLoopDoTimers(rl, rlm, mach_absolute_time());
        } else if (livePort == dispatchPort) {       //GCD唤醒，处理GCD async to main async 事件
 	        _dispatch_main_queue_callback_4CF(msg);
        } else {                                     //Source1唤醒，处理Source1事件
            __CFRunLoopDoSource1(rl, rlm, rls, msg, msg->msgh_size, &reply) || sourceHandledThisLoop;

    //执行Blocks
	__CFRunLoopDoBlocks(rl, rlm);

    //根据之前的执行结果来看是否要继续循环？
	if (sourceHandledThisLoop && stopAfterHandle) {
	    retVal = kCFRunLoopRunHandledSource;
        } else if (timeout_context->termTSR < (int64_t)mach_absolute_time()) {
            retVal = kCFRunLoopRunTimedOut;
	} else if (__CFRunLoopIsStopped(rl)) {
            __CFRunLoopUnsetStopped(rl);
	    retVal = kCFRunLoopRunStopped;
	} else if (rlm->_stopped) {
	    rlm->_stopped = false;
	    retVal = kCFRunLoopRunStopped;
	} else if (__CFRunLoopModeIsEmpty(rl, rlm, previousMode)) {
	    retVal = kCFRunLoopRunFinished;
	}
    } while (0 == retVal);

    return retVal;
}

SInt32 CFRunLoopRunSpecific(CFRunLoopRef rl, CFStringRef modeName, CFTimeInterval seconds, Boolean returnAfterSourceHandled) {     /* DOES CALLOUT */
    //通知Observers：进入loop
	__CFRunLoopDoObservers(rl, currentMode, kCFRunLoopEntry);
    //开始执行Run
	result = __CFRunLoopRun(rl, currentMode, seconds, returnAfterSourceHandled, previousMode);
    //通知Observers：推出Loop
	__CFRunLoopDoObservers(rl, currentMode, kCFRunLoopExit);
    return result;
}

void CFRunLoopRun(void) {	/* DOES CALLOUT */
    int32_t result;
    do {
        result = CFRunLoopRunSpecific(CFRunLoopGetCurrent(), kCFRunLoopDefaultMode, 1.0e10, false);
        CHECK_FOR_FORK();
    } while (kCFRunLoopRunStopped != result && kCFRunLoopRunFinished != result);
}