c++多線程（十四） - std::future_status

    c++中， std::future_status的定義如下：

enum class future_status
{
	ready,      //成功
	timeout,    //逾時
	deferred    //延遲
};
           

1. future_status::ready  

    線程myThread執行5秒，wait_for等待了6s，是以線程myThread已經執行完畢，future_status的值為ready 。

#include<iostream>
#include<thread>
#include<mutex>
#include<future>
using namespace std;

int myThread()
{
	cout << "Thread start id = " << this_thread::get_id() << endl;
	chrono::milliseconds time(5000); //休息5秒
	this_thread::sleep_for(time);
	cout << "Thread end id = " << this_thread::get_id() << endl;
	return 5;
}

int main()
{
	cout << "Main start id = " << this_thread::get_id() << endl;
	future<int> result = async(myThread);
	cout << "continue......" << endl;
	//等待6秒
	std::future_status status = result.wait_for(std::chrono::seconds(6));
	//逾時，線程還沒執行完
	if (status == std::future_status::ready)
	{
		cout << "線程執行完" << endl;
	}	 
	//成功，線程已經執行完
	else if (status == std::future_status::timeout)
	{
		cout << "線程逾時" << endl;
	}
	//延遲，async第一個參數被設定為std::launch::deferred
	else if (status == std::future_status::deferred)
	{
		cout << "線程延遲執行" << endl;
	}
	return 0;
}
           

    執行結果

2. future_status::timeout

     線程myThread執行5秒，wait_for等待了1s，是以線程myThread逾時，future_status的值為timeout。

//等待1秒
std::future_status status = result.wait_for(std::chrono::seconds(1));
           

    執行結果

3. future_status::deferred

    線程myThread延遲執行，future_status的值為deferred。

//線程延遲執行
future<int> result = async(std::launch::deferred, myThread);
           

    執行結果