C++ 使用标准库chrono获取时间戳

#include <ctime>
#include <string>
#include <chrono>
#include <sstream>
#include <iostream>

/*
 0、秒
 1、毫秒
 2、微妙
 3、纳秒
 */
std::string GetCurrentTimeStamp(int time_stamp_type = 0)
{
    std::chrono::system_clock::time_point now = std::chrono::system_clock::now();

    std::time_t now_time_t = std::chrono::system_clock::to_time_t(now);
    std::tm* now_tm = std::localtime(&now_time_t);

    char buffer[128];
    strftime(buffer, sizeof(buffer), "%F %T", now_tm);

    std::ostringstream ss;
    ss.fill('0');

    std::chrono::milliseconds ms;
    std::chrono::microseconds cs;
    std::chrono::nanoseconds ns;
    
    switch (time_stamp_type)
    {
    case 0:
        ss << buffer;
        break;
    case 1:
        ms = std::chrono::duration_cast<std::chrono::milliseconds>(now.time_since_epoch()) % 1000;
        ss << buffer << ":" << ms.count();
        break;
    case 2:
        ms = std::chrono::duration_cast<std::chrono::milliseconds>(now.time_since_epoch()) % 1000;
        cs = std::chrono::duration_cast<std::chrono::microseconds>(now.time_since_epoch()) % 1000000;
        ss << buffer << ":" << ms.count() << ":" << cs.count() % 1000;
        break;
    case 3:
        ms = std::chrono::duration_cast<std::chrono::milliseconds>(now.time_since_epoch()) % 1000;
        cs = std::chrono::duration_cast<std::chrono::microseconds>(now.time_since_epoch()) % 1000000;
        ns = std::chrono::duration_cast<std::chrono::nanoseconds>(now.time_since_epoch()) % 1000000000;
        ss << buffer << ":" << ms.count() << ":" << cs.count() % 1000 << ":" << ns.count() % 1000;
        break;
    default:
        ss << buffer;
        break;
    }

    return ss.str();
}