写日志类，怎么使用protected 类构造函数创建类实例

//

//log.h head file

//
//write log file 
//protected member function
//private member function
//
#pragma once

class CLog
{
protected:
	CLog(void);
	~CLog(void);
public:
	static void Init(CLog* &plog);
	void Log(const char* lpMsg,const char* lpFile = NULL);

private:
	void WriteLog(const char* lpMsg,const char* lpFile = NULL);

};

//
//log.cpp 
//
#include "StdAfx.h"
#include "Log.h"


CLog::CLog(void)
{
}


CLog::~CLog(void)
{
}

void CLog::WriteLog(const char* lpMsg,const char* lpFile)
{
	char lpFileName[256] = "\0";
	
	if (!lpFile){
		strcpy(lpFileName,"D:\\Log\\test\\log.txt");
	}
	else{
		strcpy(lpFileName,lpFile);
	}
	
	FILE* pFile = fopen(lpFileName,"r");
	if (!pFile){
		pFile = fopen(lpFileName,"w");//create file if not exist
		fputs(lpMsg,pFile);
		fclose(pFile);
	}
	else{
		fclose(pFile);
		pFile = fopen(lpFileName,"a");// add if file exist
		fputs(lpMsg,pFile);
		fclose(pFile);

	}
}

void CLog::Init( CLog* &plog )
{
	if (!plog){
		plog = new CLog();
	}
}

void CLog::Log(const char* lpMsg,const char* lpFile)
{
	WriteLog(lpMsg,lpFile);
}

//
//other cpp file
//

#include "Log.h"
CLog* g_plog = NULL;

void COperateFile::Tick()
{
	LARGE_INTEGER litmp;
	LONGLONG Qpart1,Qpart2;
	double dMinus,dFreq,dTime;

	QueryPerformanceFrequency(&litmp);
	dFreq = (double)litmp.QuadPart;
	QueryPerformanceCounter(&litmp);
	Qpart1 = litmp.QuadPart;

	//do something
	Sleep(1567);

	QueryPerformanceCounter(&litmp);
	Qpart2 = litmp.QuadPart;
	dMinus = (double)(Qpart2-Qpart1);
	dTime = dMinus/dFreq *1000; //ms,microSecond
	///dTime = dMinus/dFreq //s,second
	char lpSpendTime[256] = "\0";
	sprintf(lpSpendTime,"  Cost Time: %lf ms  %d NO",dTime,nCount++);

	//get system time
	SYSTEMTIME systemTime;
	memset((void*)&systemTime,0,sizeof(SYSTEMTIME));
	GetSystemTime(&systemTime);
	char lpSystemTime[256] = "\0";
	sprintf(lpSystemTime,"[ %4d.%2d.%2d  %2d:%2d:%2d ]",systemTime.wYear,\
		systemTime.wMonth,systemTime.wDay,systemTime.wHour+8,\
		systemTime.wMinute,systemTime.wSecond);

	char lpMsg[512] = "\0";
	strcpy(lpMsg,lpSystemTime);
	strcat(lpMsg,lpSpendTime);
	strcat(lpMsg,"\n");

	//write message to txt file
	if (!g_plog){
		CLog::Init(g_plog);
	}
	if (g_plog){
		g_plog->Log(lpMsg);
	}

	/*char lpFileName[256] = "\0";
	strcpy(lpFileName,"D:\\Log\\test\\log.txt");
	FILE* pFile = fopen(lpFileName,"r");
	if (!pFile){
		pFile = fopen(lpFileName,"w");//create file if not exist
		fputs(lpMsg,pFile);
		fclose(pFile);
	}
	else{
		fclose(pFile);
		pFile = fopen(lpFileName,"a");// add if file exist
		fputs(lpMsg,pFile);
		fclose(pFile);

	}
	*/

}