【并发编程实战笔记】--使用锁和条件变量的线程安全队列

线程安全队列实现代码

queue.hpp

template<typename T>
class threadsafe_queue
{
private:
    mutable std::mutex mut;
    std::queue<T> data_queue;
    std::condition_variable data_cond;
public:
    threadsafe_queue()
    {}

    void push(T new_value)
    {
        std::lock_guard<std::mutex> lk(mut);
        data_queue.push(std::move(new_value));
        data_cond.notify_one();
    }

    void wait_and_pop(T& value)
    {
        std::unique_lock<std::mutex> lk(mut);
        data_cond.wait(lk,[this]{return !data_queue.empty();});
        value=std::move(data_queue.front());
        data_queue.pop();
    }

    std::shared_ptr<T> wait_and_pop()
    {
        std::unique_lock<std::mutex> lk(mut);
        data_cond.wait(lk,[this]{return !data_queue.empty();});
        std::shared_ptr<T> res(
            std::make_shared<T>(std::move(data_queue.front())));
        data_queue.pop();
        return res;
    }

    bool try_pop(T& value)
    {
        std::lock_guard<std::mutex> lk(mut);
        if(data_queue.empty())
            return false;
        value=std::move(data_queue.front());
        data_queue.pop();
    }

    std::shared_ptr<T> try_pop()
    {
        std::lock_guard<std::mutex> lk(mut);
        if(data_queue.empty())
            return std::shared_ptr<T>();
        std::shared_ptr<T> res(
            std::make_shared<T>(std::move(data_queue.front())));
        data_queue.pop();
        return res;
    }

    bool empty() const
    {
        std::lock_guard<std::mutex> lk(mut);
        return data_queue.empty();
    }
};

测试代码

int main()
{
    threadsafe_queue<int> si;
    si.push(5);
    //si.wait_and_pop();
    if(!si.empty())
    {
        cout << "pop is operator" << endl;
    //  int x;
    //  si.try_pop(x);
    //  cout << "x : " << x << endl;
        auto a = si.try_pop();
        cout << "a : " << *a << endl;
    }
    return 0;
}

使用wait_and_pop()与try_pop()函数的区别是在于，当队列为空时，wait_and_pop()会引发安全异常，而try_pop()函数不会。

源码地址：
https://github.com/ykevin/blog/tree/master/concurrency/queue