C++ 多线程 生产者消费者（1）_std::queue 生产消费

#include <queue>
#include <thread>
#include <mutex>
#include <iostream>
#include <vector>
#include <unistd.h>
 
std::queue<std::string> mQueue;
std::mutex m;
std::condition_variable cv_notEmpty;
 
 
void workerPut(int max_num, int interval=1){
 
	for(int i=0;i<max_num;i++){
		sleep(interval);
		std::unique_lock<std::mutex>  lk_queue(m);
		mQueue.push("JobItem " + std::to_string(i));
		std::cout << "put value to queue: " << i << std::endl;
		cv_notEmpty.notify_all();
 
	}
 
}
 
void workShow(int interval=2){
 
	while(true){
		
		sleep(interval);
		std::unique_lock<std::mutex> lk_queue(m);
		cv_notEmpty.wait(lk_queue,[]{return !mQueue.empty();});
 
		std::string value = mQueue.front();
		mQueue.pop();
 
		std::cout << "consume value: " + value << std::endl;
	}
	
}
 
 
int main(){
 
 
	std::thread producer(workerPut,10,1);
	std::thread consumer(workShow,2);
 
	producer.join();
	consumer.join();
	
	return 0;
 
 
}

上面有个限制：

（1）生产者生产max_num个产品就退出；

（2）对队列上线没有做要求。

下面继续改进，

（1）生产者可以一直生产产品放到队列；

（2）设置队列最大长度，即队列满了则生产者要被阻塞等待；等待消费者消费了数据，队列有空余，再进行生产；

（3）消费者当队列不空时消费产品

#include <queue>
#include <thread>
#include <mutex>
#include <iostream>
#include <vector>
#include <unistd.h>
 
std::queue<std::string> mQueue;
std::mutex m;
std::condition_variable cv_notEmpty;
std::condition_variable cv_notFull;
 
 
void workerPut(int max_num, int interval=1){
 
    int i = 0;
    while(true){
		sleep(interval);
		std::unique_lock<std::mutex>  lk_queue(m);
		cv_notFull.wait(lk_queue, []{return mQueue.size()<5;}); // queue最长5
 
		mQueue.push("JobItem " + std::to_string(i));
		std::cout << "put value to queue: " << i << std::endl;
		std::cout << "current queue is : " << mQueue.size() << std::endl;
		cv_notEmpty.notify_all();
		i++;
	}
 
}
 
void workShow(int interval=2){
 
	while(true){
		
		sleep(interval);
		std::unique_lock<std::mutex> lk_queue(m);
		cv_notEmpty.wait(lk_queue,[]{return !mQueue.empty();});
 
		std::string value = mQueue.front();
		mQueue.pop();
 
		std::cout << "consume value: " + value << std::endl;
		std::cout << "current queue is : " << mQueue.size() << std::endl;
		cv_notFull.notify_all();
	}
	
}
 
 
int main(){
 
	std::thread producer(workerPut,10,1);
	std::thread consumer(workShow,2);
 
	producer.join();
	consumer.join();
	
	return 0;
 
}

由于设置了队列最长为5，而且生产速度是消费速度的2倍，因此最终队列长度会一直保持在5

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