C++并发与多线程（高级函数async）

async

在 C++ 中，async 关键字用于实现异步编程，它允许你定义异步操作，这些操作可以在后台执行，而不会阻塞当前线程。这是 C++11 引入的特性，与 std::async 函数和 std::future 类一起使用。与thread函数模板的区别在于async可以有返回值，thread无返回值。

简单入门

// ConsoleApplication10.cpp : 此文件包含 "main" 函数。程序执行将在此处开始并结束。
//

#include <iostream>
#include <vector>
#include <map>
#include <string>
#include <thread>
#include <mutex>
#include <cstdint>
#include <future>

#include <list>
using  namespace std;



int mythread()
{
	cout << "func " << "  threadid = " << this_thread::get_id() << " start " << endl << endl;
	std::chrono::milliseconds dura(3000);
	std::this_thread::sleep_for(dura);
	cout << "func " << "  threadid = " << this_thread::get_id() <<" end " << endl << endl;
	return 5;

}

int main()
{
	cout << "=========================================== " << " threadid = " << this_thread::get_id() << endl << endl;
	std::future<int> ret =  std::async(mythread);
	cout << ret.get() << endl; //堵塞获取值,注意：get函数只能调用一次，不能多次调用
	cout << "=========================================== " << " threadid = " << this_thread::get_id() << endl << endl;

	return 0;
}

中级过度

// ConsoleApplication10.cpp : 此文件包含 "main" 函数。程序执行将在此处开始并结束。
//

#include <iostream>
#include <vector>
#include <map>
#include <string>
#include <thread>
#include <mutex>
#include <cstdint>
#include <future>

#include <list>
using  namespace std;


class A
{
public:
	int mythread(int myint)
	{
		cout << "func " << "  threadid = " << this_thread::get_id() << " start " << endl << endl;
		cout << "myint = " << myint << endl;
		std::chrono::milliseconds dura(3000);
		std::this_thread::sleep_for(dura);
		cout << "func " << "  threadid = " << this_thread::get_id() << " end " << endl << endl;
		return 5;

	}
};


int main()
{
	cout << "=========================================== " << " threadid = " << this_thread::get_id() << endl << endl;
	A a;
	int num = 100;

	std::future<int> ret =  std::async(&A::mythread,&a,num);//传入可调用对象 &a == std::ref(a)都是引用传递 相当于传递了this指针。
	cout << ret.get() << endl; //堵塞获取值

	cout << "=========================================== " << " threadid = " << this_thread::get_id() << endl << endl;

	return 0;
}

其他线程使用可以参数我主页中的 C语言：高级并发操作（线程）文章。