windows c/c++ 代码运行时间，毫秒级

#pragma once
/*
//计算代码段运行时间的类
//
*/
#include <iostream>

#ifndef ComputeTime_h
#define ComputeTime_h


class   ComputeTime    
{  
private:  
	int Initialized;  
	__int64 Frequency;  
	__int64 BeginTime;  
		    
public:  

	bool Avaliable();  
	double End();  
	bool Begin();  
	ComputeTime();  
	virtual   ~ComputeTime();    

};  


#endif




#include "stdafx.h"
#include "ComputeTime.h"
#include <iostream>
#include <Windows.h>

ComputeTime::ComputeTime()  
{  
	Initialized=QueryPerformanceFrequency((LARGE_INTEGER   *)&Frequency);  
}  
   
 ComputeTime::~ComputeTime()  
{  
		    
}  
   
 bool   ComputeTime::Begin()  
{  
	if(!Initialized)  
		return 0;

	 return   QueryPerformanceCounter((LARGE_INTEGER   *)&BeginTime);  
 }
     
 double   ComputeTime::End()
{  
	 if(!Initialized)  
		return 0;

		   
	 __int64   endtime;  
		   
	 QueryPerformanceCounter((LARGE_INTEGER   *)&endtime);  
		    
		  
	 __int64   elapsed = endtime-BeginTime;  
		    
		  
	 return   ((double)elapsed/(double)Frequency)*1000.0;  //单位毫秒
 }  

 bool   ComputeTime::Avaliable()
{  
	 return Initialized;  
}