线程安全的循环缓冲区

Question

我想改变我看到here的线程安全循环缓冲区， 在条件变量中添加谓词，如此article。

我需要在缓冲区空了很多时间后退出我的等待状态....所以这是我的循环缓冲区模板快照：

//Template of CIRCULAR BUFFER thread-safe

template <typename T>
class circ_buffer : private boost::noncopyable{
public:
    typedef boost::mutex::scoped_lock lock;

    circ_buffer(){}
    circ_buffer(int n){cb.set_capacity(n);}

 ........

  struct cb_not_empty{
        boost::circular_buffer<T>& circ_buf;

        cb_not_empty(boost::circular_buffer<T>& circular_buffer_):
            circ_buf(circular_buffer_){}

        bool operator ()() const{
            return !circ_buf.empty();
        }
    };

    template<typename Duration>
    bool timed_wait_and_pop(T& popped_valued,Duration const& wait_duration){
        lock lk(monitor);
        if(!buffer_not_empty.timed_wait(lk,wait_duration,cb_not_empty(the_cb)))
            return false;
        popped_valued = the_cb.front();
        the_cb.pop();
        return true;
    }

 .......

private:
    boost::condition            buffer_not_empty;
    boost::mutex                monitor;
    boost::circular_buffer<T>   cb;
    std::atomic<bool>           circ_buf_flag;   //flag to turn ON/OFF circular buffer: make circ_buf OFF to go out

};

我的gnu编译器给我

error: 'the_cb' was not declared in this scope
         if(!buffer_not_empty.timed_wait(lk,wait_duration,cb_not_empty(the_cb)))
                                                                       ^