C++ | 多线程编程（四）信号量

超、凢脫俗 2022-11-11 05:50 305阅读 0赞

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzkxOTkzMg_size_16_color_FFFFFF_t_70]  
[https://zh.cppreference.com/w/cpp/thread/counting\_semaphore][https_zh.cppreference.com_w_cpp_thread_counting_semaphore]  
成员函数：

*  release：增加内部计数器并除阻获取者  
    相当于V操作
 *  acquire： 减少内部计数器或阻塞到直至能如此  
    相当于p操作

#include <iostream>
    #include <thread>
    #include <semaphore>
    
    using namespace std;
    
    /*
    三个线程，依次打印ABC
    */
    
    std::counting_semaphore sema(1);
    std::counting_semaphore semb(0);
    std::counting_semaphore semc(0);
    
    void thread_a()
    {
        
    	for (int i = 0; i < 10; ++i)
    	{
        
    		sema.acquire();	// p
    		cout << "A";
    		semb.release(); // v
    	}
    }
    void thread_b()
    {
        
    	for (int i = 0; i < 10; ++i)
    	{
        
    		semb.acquire();	// p
    		cout << "B";
    		semc.release();
    	}
    }
    void thread_c()
    {
        
    	for (int i = 0; i < 10; ++i)
    	{
        
    		semc.acquire();	// p
    		cout << "C";
    		sema.release();
    	}
    }
    
    int main()
    {
        
    	std::thread ta(thread_a);
    	std::thread tb(thread_b);
    	std::thread tc(thread_c);
    
    	ta.join();
    	tb.join();
    	tc.join();
    
    	return 0;
    }

![在这里插入图片描述][20210319164042949.png]

--------------------

#include <iostream>
    #include <thread>
    #include <semaphore>
    
    using namespace std;
    
    /*  生产者，消费者模型 */
    
    std::counting_semaphore seamp(1);	// 生产者信号量
    std::counting_semaphore seams(0);	// 消费者信号量
    int num(0);
    
    
    // 生产者
    void producer_thread()
    {
        
    	while (num < 10)
    	{
        
    		seamp.acquire(); // p
    		num += 1;
    		cout << "producer: " << num << endl;
    		seams.release();	// v
    	}
    }
    void consumer_thread()
    {
        
    	while (num < 10)
    	{
        
    		seams.acquire();
    		cout << "consumer: " << num << endl;
    		seamp.release();
    	}
    }
    
    int main()
    {
        
    	std::thread tp1(producer_thread);	// 生产者线程
    	std::thread ts1(consumer_thread);	// 生产者线程
    
    	tp1.join();
    	ts1.join();
    
    	return 0;
    }

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzkxOTkzMg_size_16_color_FFFFFF_t_70 1]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzkxOTkzMg_size_16_color_FFFFFF_t_70]: /images/20221022/635b34a98d614911954bbf324c683003.png
[https_zh.cppreference.com_w_cpp_thread_counting_semaphore]: https://zh.cppreference.com/w/cpp/thread/counting_semaphore
[20210319164042949.png]: https://img-blog.csdnimg.cn/20210319164042949.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzkxOTkzMg_size_16_color_FFFFFF_t_70 1]: https://img-blog.csdnimg.cn/20210319164507120.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzkxOTkzMg==,size_16,color_FFFFFF,t_70