c++ 获取时间戳 与 时间戳转化为时间

//获取系统时间戳毫秒级
std::string GetTimeStamp()
{
	time_t curtime = time(NULL);
	unsigned long long time = (unsigned long long)curtime;
	return std::to_string(time);
}

//时间戳转化为时间 毫秒级
std::string Stamp2Time(long long timestamp)
{
	int ms = timestamp % 1000;//取毫秒
	time_t tick = (time_t)(timestamp/1000);//转换时间
	struct tm tm;
	char s[40];
	tm = *localtime(&tick);
	strftime(s, sizeof(s), "%Y-%m-%d %H:%M:%S", &tm);
	std::string str(s);
	str = str+ " " + std::to_string(ms);
	return str;
}

//c++ 利用chrono函数获取时间戳 毫秒级
#include <iostream>
#include <chrono>
#include <string>
#include <time.h>
std::string GetTimeStamp()
{
	auto timeNow = chrono::duration_cast<chrono::milliseconds>(chrono::system_clock::now().time_since_epoch());
	long long timestamp = timeNow.count();
	return std::to_string(timestamp);
}