void指针及指针的多次赋值的理解

int A::functionCommamd(const DWORD _from,const DWORD _to,const DWORD Event_type,void * _data,void* _ret)
{
	if (CMD_XXX_NUM==Event_type)
	{
		/*PropertiesPtr mProp= *(Properties::PropertiesPtr*)_data;
		std::string data = mProp->getValue("Data", "");
		Json::Reader oReader;
		Json::Value oValue;
		char data = oValue["event_info"]["pic_url"]["vehicle_pic_url"].asString().c_str();*/
		CHAR*strdata = (char*)_data;
		std::string* strret = (std::string*)_ret; //指针变量，进来的时候传数据长度，返回获取的图片URL
		int iBufSize = atoi((*strret).c_str());
		return GetCapturePicUrl(strdata, iBufSize, *strret);
	}
	return 0;
}

funcCommand(1, 2, 3, pstEventInfo->pPlatePicData.get(), &strPlateRet);