一、便于使用，使用chrono封装一个简单的类

#pragma once

#include <chrono>

using CTime_point = std::chrono::high_resolution_clock::time_point;

class CElapsedTime final
{
public:
    static CTime_point now() {
        return std::chrono::high_resolution_clock::now();
    }

    using s  = std::chrono::seconds;
    using ms = std::chrono::milliseconds;
    using us = std::chrono::microseconds;
    using ns = std::chrono::nanoseconds;

    //获取当前时间戳 类型: s/ms/us/ns
    template<typename T = CElapsedTime::ms> static long long since_epoch() {
        const auto now = std::chrono::system_clock::now();//时间戳要用 system_clock
        const auto sinceEpoch = std::chrono::duration_cast<T>(now.time_since_epoch());
        return sinceEpoch.count();
    }

    //计算时间差  类型: s/ms/us/ns
    template<typename T = CElapsedTime::ms>
    static long long duration(const CTime_point &begin, const CTime_point &end)
    {
        const auto delta = std::chrono::duration_cast<T>(end - begin);
        return delta.count();
    }

    const static long long _s  = 1;
    const static long long _ms = 1000;
    const static long long _us = 1000000;
    const static long long _ns = 1000000000;
    //计算时间差  返回浮点类型
    template<size_t T = CElapsedTime::_ms>
    static double duration(const CTime_point &begin, const CTime_point &end)
    {
        const std::chrono::duration<double, std::ratio<1, T>> delta = end - begin;
        return delta.count();
    }
};

二、直接调用

#include <stdlib.h>
#include <thread>
#include <iostream>
#include <iomanip>
#include "CElapsedTime.h"

int main(int argc, char *argv[])
{
#ifdef _WIN32
   _tzset();
   _putenv("_tz=GMT +8");
#else
    setenv("TZ", "Asia/Shanghai", 1);
#endif

    auto begin = CElapsedTime::now();
    std::this_thread::sleep_for(std::chrono::milliseconds(1230));//运行时长
    auto end = CElapsedTime::now();

    long long sinceEpoch = CElapsedTime::since_epoch();
    std::cout << "since epoch: " << sinceEpoch  << std::endl;

    std::cout << "run(s):  " << CElapsedTime::duration<CElapsedTime::s>(begin, end)  << std::endl;
    std::cout << "run(ms): " << CElapsedTime::duration<CElapsedTime::ms>(begin, end) << std::endl;
    std::cout << "run(us): " << CElapsedTime::duration<CElapsedTime::us>(begin, end) << std::endl;
    std::cout << "run(ns): " << CElapsedTime::duration<CElapsedTime::ns>(begin, end) << std::endl;

    std::cout << "run(s):  " << std::fixed << std::setprecision(3) << CElapsedTime::duration<CElapsedTime::_s>(begin, end)  << std::endl;
    std::cout << "run(ms): " << std::fixed << std::setprecision(3) << CElapsedTime::duration<CElapsedTime::_ms>(begin, end) << std::endl;
    std::cout << "run(us): " << std::fixed << std::setprecision(3) << CElapsedTime::duration<CElapsedTime::_us>(begin, end) << std::endl;
    std::cout << "run(ns): " << std::fixed << std::setprecision(3) << CElapsedTime::duration<CElapsedTime::_ns>(begin, end) << std::endl;

    return 0;
}

运行结果：