c++11 std::chrono

简洁版：项目工程中，可直接调用下列time.h文件

#ifndef TIME_H
#define TIME_H
 
#include <cstdint>
#include <chrono>
 
class ElapsedTimer
{
public:
	ElapsedTimer(bool do_start = false)
	{
		if (do_start)
			start();
	}
 
	void start()
	{
		m_start_point = std::chrono::high_resolution_clock::now();
	}
 
	uint64_t get_elapsed_ms()
	{
		auto now = std::chrono::high_resolution_clock::now();
		return std::chrono::duration_cast<std::chrono::milliseconds>(now-m_start_point).count();
	}
 
	uint64_t get_elapsed_us()
	{
		auto now = std::chrono::high_resolution_clock::now();
		return std::chrono::duration_cast<std::chrono::microseconds>(now-m_start_point).count();
	}
 
private:
	std::chrono::time_point<std::chrono::high_resolution_clock> m_start_point;
};
 
#endif

解析版：

#ifndef TIME_H
#define TIME_H
 
#include <cstdint>
#include <chrono>  //chrono是c++ 11中的时间库，提供计时，时钟等功能
 
class ElapsedTimer
{
public:
	ElapsedTimer(bool do_start = false)
	{
		if (do_start)
			start();
	}
 
	void start()
	{
		m_start_point = std::chrono::high_resolution_clock::now();  //高精度时钟类std::chrono::high_resolution_clock
	}
 
	uint64_t get_elapsed_ms()
	{
		auto now = std::chrono::high_resolution_clock::now(); //要获取某时钟类的当前时刻，调用静态成员函数now()
		return std::chrono::duration_cast<std::chrono::milliseconds>(now-m_start_point).count(); //ms；
	}  
  //std::chrono::duration_cast<std::chrono::milliseconds>(end - begin).count(); 成员函数count()返回单位时间的数量
 
	uint64_t get_elapsed_us()
	{
		auto now = std::chrono::high_resolution_clock::now();
		return std::chrono::duration_cast<std::chrono::microseconds>(now-m_start_point).count();  //us
	}
 
private:
	std::chrono::time_point<std::chrono::high_resolution_clock> m_start_point;
};
 
#endif