c++11实现异步定时器

    c++11提供了丰富的时间和线程操作函数，比如 std::this_thread::sleep, std::chrono::seconds等。可以利用这些来很方便的实现一个定时器。 
    定时器要求在固定的时间异步执行一个操作，比如boost库中的boost::asio::deadline_timer，以及MFC中的定时器。这里，利用c++11的thread, mutex, condition_variable 来实现一个定时器： 
    定时器要求异步执行任务    ----> 开辟独立的线程 
    定时器要求能够启动和取消 ----> 提供安全的取消操作，使用互斥量和信号量 
    定时器要求每个定时时刻到达的时候执行的任务要尽可能节省时间

实现

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#ifndef TIMER_H_ #define TIMER_H_ #include<functional> #include<chrono> #include<thread> #include<atomic> #include<memory> #include<mutex> #include<condition_variable> class Timer{ public:     Timer() :expired_(true), try_to_expire_(false){     }       Timer(const Timer& t){         expired_ = t.expired_.load();         try_to_expire_ = t.try_to_expire_.load();     }     ~Timer(){         Expire();         //      std::cout << "timer destructed!" << std::endl;     }       void StartTimer(int interval, std::function<void()> task){         if (expired_ == false){             //          std::cout << "timer is currently running, please expire it first..." << std::endl;             return;         }         expired_ = false;         std::thread([this, interval, task](){             while (!try_to_expire_){                 std::this_thread::sleep_for(std::chrono::milliseconds(interval));                 task();             }             //          std::cout << "stop task..." << std::endl;             {                 std::lock_guard<std::mutex> locker(mutex_);                 expired_ = true;                 expired_cond_.notify_one();             }         }).detach();     }       void Expire(){         if (expired_){             return;         }           if (try_to_expire_){             //          std::cout << "timer is trying to expire, please wait..." << std::endl;             return;         }         try_to_expire_ = true;         {             std::unique_lock<std::mutex> locker(mutex_);             expired_cond_.wait(locker, [this]{return expired_ == true; });             if (expired_ == true){                 //              std::cout << "timer expired!" << std::endl;                 try_to_expire_ = false;             }         }     }           template<typename callable, class... arguments>     void SyncWait(int after, callable&& f, arguments&&... args){           std::function<typename std::result_of<callable(arguments...)>::type()> task             (std::bind(std::forward<callable>(f), std::forward<arguments>(args)...));         std::this_thread::sleep_for(std::chrono::milliseconds(after));         task();     }     template<typename callable, class... arguments>     void AsyncWait(int after, callable&& f, arguments&&... args){         std::function<typename std::result_of<callable(arguments...)>::type()> task             (std::bind(std::forward<callable>(f), std::forward<arguments>(args)...));           std::thread([after, task](){             std::this_thread::sleep_for(std::chrono::milliseconds(after));             task();         }).detach();     }       private:     std::atomic<bool> expired_;     std::atomic<bool> try_to_expire_;     std::mutex mutex_;     std::condition_variable expired_cond_; }; #endif   ////////////////////test.cpp #include<iostream> #include<string> #include<memory> #include"Timer.hpp" using namespace std; void EchoFunc(std::string&& s){     std::cout << "test : " << s << endl; }   int main(){     Timer t;     //周期性执行定时任务     t.StartTimer(1000, std::bind(EchoFunc,"hello world!"));     std::this_thread::sleep_for(std::chrono::seconds(4));     std::cout << "try to expire timer!" << std::endl;     t.Expire();       //周期性执行定时任务     t.StartTimer(1000, std::bind(EchoFunc,  "hello c++11!"));     std::this_thread::sleep_for(std::chrono::seconds(4));     std::cout << "try to expire timer!" << std::endl;     t.Expire();       std::this_thread::sleep_for(std::chrono::seconds(2));       //只执行一次定时任务     //同步     t.SyncWait(1000, EchoFunc, "hello world!");     //异步     t.AsyncWait(1000, EchoFunc, "hello c++11!");       std::this_thread::sleep_for(std::chrono::seconds(2));       return 0; }