C++实现一个简单的阻塞队列

class BoundedBlockingQueue {
private:
    int capacity;
    list<int> bq;
    condition_variable cv;
    mutex mu;
public:
    BoundedBlockingQueue(int capacity) {
        this->capacity=capacity;
    }
    
    void enqueue(int element) {
        unique_lock<mutex> lck(mu);
        while(bq.size()==capacity) cv.wait(lck);
        bq.push_front(element);
        cv.notify_all(); // 通知 可读
    }
    
    int dequeue() {
        unique_lock<mutex> lck(mu);
        while(bq.size()==0) cv.wait(lck);
        int ret=bq.back();
        bq.pop_back();
        lck.unlock();
        if(bq.size()<capacity) cv.notify_all(); //通知可写
        return ret;
    }
    
    int size() {
        unique_lock<mutex> lck(mu);
        int size=bq.size();    
        return size;
    }
};