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/* ScummVM - Scumm Interpreter
* Copyright (C) 2001 Ludvig Strigeus
* Copyright (C) 2001-2005 The ScummVM project
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* $Header$
*
*/
#ifndef COMMON_SINGLETON_H
#define COMMON_SINGLETON_H
namespace Common {
/**
* Generic template base class for implementing the singleton design pattern.
*/
template <class T>
class Singleton
{
private:
Singleton<T>(const Singleton<T>&);
Singleton<T>& operator= (const Singleton<T>&);
static T* _singleton;
/**
* The default object factory used by the template class Singleton.
* By specialising this template function, one can make a singleton use a
* custom object factory. For example, to support encapsulation, your
* singleton class might be pure virtual (or "abstract" in Java terminology),
* and you specialise makeInstance to return an instance of a subclass.
*/
//template <class T>
#if defined (_WIN32_WCE) || defined (_MSC_VER)
//FIXME evc4 and msvc7 doesn't like it as private member
public:
#endif
static T* makeInstance() {
return new T();
}
public:
static T& instance() {
// TODO: We aren't thread safe. For now we ignore it since the
// only thing using this singleton template is the config manager,
// and that is first instantiated long before any threads.
// TODO: We don't leak, but the destruction order is nevertheless
// semi-random. If we use multiple singletons, the destruction
// order might become an issue. There are various approaches
// to solve that problem, but for now this is sufficient
if (!_singleton)
_singleton = T::makeInstance();
return *_singleton;
}
protected:
Singleton<T>() { }
virtual ~Singleton<T>() { }
typedef T SingletonBaseType;
};
#define DECLARE_SINGLETON(T) template<> T* Common::Singleton<T>::_singleton=0
} // End of namespace Common
#endif
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