timer.h

#pragma once
#include <chrono>

// https://gist.github.com/mcleary/b0bf4fa88830ff7c882d
class Timer
{
    public:
        void start()
        {
            m_StartTime = std::chrono::system_clock::now();
            m_bRunning = true;
        }
        void stop()
        {
            m_EndTime = std::chrono::system_clock::now();
            m_bRunning = false;
        }
        double elapsedMilliseconds()
        {
            std::chrono::time_point<std::chrono::system_clock> endTime;

            if (m_bRunning)
                endTime = std::chrono::system_clock::now();
            else
                endTime = m_EndTime;
            return std::chrono::duration_cast<std::chrono::milliseconds>(endTime - m_StartTime).count();
        }
        double elapsedSeconds()
        {
            return elapsedMilliseconds() / 1000.0;
        }
    private:
        std::chrono::time_point<std::chrono::system_clock> m_StartTime;
        std::chrono::time_point<std::chrono::system_clock> m_EndTime;
        bool m_bRunning = false;
};