C++ timer计时器

timer.hpp

#ifndef PROJECT_TIMER_HPP
#define PROJECT_TIMER_HPP

#include <ratio>
#include <chrono>

namespace datetime {

// DurationPeriod
typedef std::chrono::nanoseconds Nano;   // 纳秒 <long, long>
typedef std::chrono::microseconds Micro; // 微秒 <long, long>
typedef std::chrono::milliseconds Milli; // 毫秒 <long, long>
typedef std::chrono::seconds Seconds;    // 秒   <long, long>
typedef std::chrono::minutes Minutes;    // 分钟 <long>
typedef std::chrono::hours Hours;        // 小时 <long>

typedef std::chrono::duration<long, std::ratio<60 * 60 * 24>> Day;        // 天
typedef std::chrono::duration<long, std::ratio<60 * 60 * 24 * 7>> Week;   // 周
typedef std::chrono::duration<long, std::ratio<60 * 60 * 24 * 30>> Month; // 月

// Clock
typedef std::chrono::steady_clock SteadyClock;
typedef std::chrono::system_clock SystemClock;

template<typename DurationPeriod = Milli, typename Clock = SteadyClock>
class Timer final {

private:
  typedef DurationPeriod Period;
  typedef std::chrono::time_point<Clock> TimePoint;

  TimePoint start{Clock::now()};

public:

  void reset() {
    start = Clock::now();
  }

  typename Period::rep elapsed() const {
    return std::chrono::duration_cast<Period>(Clock::now() - start).count();
  }
};
}
#endif