C++設計一個精度達納秒的計時器

 可計時 納秒-小時

/************************************************************************************
**
**  Copyright (C) 2020, Shaoguang. All rights reserved.
**
**  Date  : 2020/04/01
**
************************************************************************************/

#ifndef ELAPSED_TIMER_H_
#define ELAPSED_TIMER_H_

#include <chrono>

/** \class ElapsedTimer
    \brief Defines an elapsed timer.
*/
template<class TimeT = double>
class ElapsedTimer
{
public:
    using chrono_clock_type = std::chrono::high_resolution_clock;
    using time_point = typename chrono_clock_type::time_point;
    using time_t = TimeT;
    
    /** Constructs a elapsed timer, and start timing. */
    ElapsedTimer() : m_tp(chrono_clock_type::now()) {}

    /** Restart timing. */
    void reset()
    {
        m_tp = chrono_clock_type::now();
    }
    
    /** Returns the elapsed time in milliseconds. */
    time_t elapsed() const
    {
        return elapsedMilliseconds();
    }
    
    /** Returns the elapsed time in nanoseconds. */
    time_t elapsedNanoseconds() const
    {
        return static_cast<nanoseconds_t>(chrono_clock_type::now() - m_tp).count();
    }
    
    /** Returns the elapsed time in microseconds. */
    time_t elapsedMicroseconds() const
    {
        return static_cast<microseconds_t>(chrono_clock_type::now() - m_tp).count();
    }
    
    /** Returns the elapsed time in milliseconds. */
    time_t elapsedMilliseconds() const
    {
        return static_cast<milliseconds_t>(chrono_clock_type::now() - m_tp).count();
    }
    
    /** Returns the elapsed time in seconds. */
    time_t elapsedSeconds() const
    {
        return static_cast<seconds_t>(chrono_clock_type::now() - m_tp).count();
    }
    
    /** Returns the elapsed time in minutes.  */
    time_t elapsedMinutes() const
    {
        return static_cast<minutes_t>(chrono_clock_type::now() - m_tp).count();
    }
    
    /** Returns the elapsed time in hours. */
    time_t elapsedHours() const
    {
        return static_cast<hours_t>(chrono_clock_type::now() - m_tp).count();
    }

private:
    using nanoseconds_t = std::chrono::duration<time_t, std::chrono::nanoseconds::period>;
    using microseconds_t = std::chrono::duration<time_t, std::chrono::microseconds::period>;
    using milliseconds_t = std::chrono::duration<time_t, std::chrono::milliseconds::period>;
    using seconds_t = std::chrono::duration<time_t, std::chrono::seconds::period>;
    using minutes_t = std::chrono::duration<time_t, std::chrono::minutes::period>;
    using hours_t = std::chrono::duration<time_t, std::chrono::hours::period>;

    time_point m_tp;
};

#endif // ELAPSED_TIMER_H_