PDS20150625

#pragma once
#include <mutex>
#include <condition_variable>
template <class T>
class Exchanger {
private:
    T val;
    std::condition_variable cv;
    std::mutex m;
public:
    Exchanger() {
    }
    T exchange(T t) {
        std::unique_lock<std::mutex> ul(m);
        val = t;
        cv.notify_one();
        cv.wait(ul);
        return val;
    }
    ~Exchanger() {
    }
};