c++11 chrono全面解析(最高可达纳秒级别的精度)

template <intmax_t N, intmax_t D = 1> class ratio;

#include<iostream>
#include<chrono>
using namespace std;
int main()
{
	cout << "millisecond : ";
	cout << std::chrono::milliseconds::period::num << "/" << std::chrono::milliseconds::period::den << "s" <<endl;
	system("pause");
	return 0;
}

template <class Rep, class Period = ratio<1> >
class duration;

(1)duration() = default;    //默认构造
(2)duration (const duration& dtn);        //(2)(3)拷贝构造
(3)template<class Rep2, class Period2>
   constexpr duration (const duration<Rep2,Period2>& dtn);
(4)template<class Rep2>      //传递一个某类型（int等）的数值，构造一个时间段   
   constexpr explicit duration (const Rep2& n);

#include <iostream>
#include <chrono>
int main()
{
	std::chrono::milliseconds mscond(1000); // 1 second
	std::cout << mscond.count() << " milliseconds.\n";
 
	std::cout << mscond.count() * std::chrono::milliseconds::period::num / std::chrono::milliseconds::period::den;
	std::cout << " seconds.\n";
	system("pause");
	return 0;
}

template <class Clock, class Duration = typename Clock::duration>
  class time_point;

#include <iostream>
#include <chrono>
#include <ctime>
using namespace std;
int main()
{
	//距离时间戳2两秒
	chrono::time_point<chrono::system_clock, chrono::seconds> tp(chrono::seconds(2));
	cout << "to epoch : " <<tp.time_since_epoch().count() << "s" <<endl;
	//转化为ctime，打印输出时间点
	time_t tt = chrono::system_clock::to_time_t(tp);
	char a[50];
	ctime_s(a, sizeof(a), &tt);
	cout << a;
	system("pause");
	return 0;
}

#include <iostream>
#include <chrono>
using namespace std;
int main()
{
	cout << "system clock          : ";
	cout << chrono::system_clock::period::num << "/" << chrono::system_clock::period::den << "s" << endl;
	cout << "steady clock          : ";
	cout << chrono::steady_clock::period::num << "/" << chrono::steady_clock::period::den << "s" << endl;
	cout << "high resolution clock : ";
	cout << chrono::high_resolution_clock::period::num << "/" << chrono::high_resolution_clock::period::den << "s" << endl;
	system("pause");
	return 0;
}

template <class ToDuration, class Clock, class Duration>
  time_point<Clock,ToDuration> time_point_cast (const time_point<Clock,Duration>& tp);

#include <iostream>
#include <chrono>
#include <ctime>
using namespace std;
int main()
{
	//定义毫秒级别的时钟类型
	typedef chrono::time_point<chrono::system_clock, chrono::milliseconds> microClock_type;
	//获取当前时间点，windows system_clock是100纳秒级别的(不同系统不一样，自己按照介绍的方法测试)，所以要转换
	microClock_type tp = chrono::time_point_cast<chrono::milliseconds>(chrono::system_clock::now());
	//转换为ctime.用于打印显示时间
	time_t tt = chrono::system_clock::to_time_t(tp);
	char _time[50];
	ctime_s(_time,sizeof(_time),&tt);
	cout << "now time is : " << _time;
	//计算距离1970-1-1,00:00的时间长度，因为当前时间点定义的精度为毫秒，所以输出的是毫秒
	cout << "to 1970-1-1,00:00  " << tp.time_since_epoch().count() << "ms" << endl;
	system("pause");
	return 0;
}