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;
}