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/* ScummVM - Graphic Adventure Engine
*
* ScummVM is the legal property of its developers, whose names
* are too numerous to list here. Please refer to the COPYRIGHT
* file distributed with this source distribution.
*
* 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*
* $URL$
* $Id$
*
*/
#ifndef COMMON_SINGLETON_H
#define COMMON_SINGLETON_H
#include "common/noncopyable.h"
namespace Common {
/**
* Generic template base class for implementing the singleton design pattern.
*/
template<class T>
class Singleton : NonCopyable {
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) || defined (__WINS__)
//FIXME evc4 and msvc7 doesn't like it as private member
public:
#endif
static T *makeInstance() {
return new T();
}
static void destroyInstance() {
delete _singleton;
_singleton = 0;
}
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;
}
static void destroy() {
T::destroyInstance();
}
protected:
Singleton<T>() { }
#ifdef __SYMBIAN32__
virtual ~Singleton() { }
#else
virtual ~Singleton<T>() { }
#endif
typedef T SingletonBaseType;
};
/**
* Note that you need to use this macro from the global namespace.
*
* This is because C++ requires initial explicit specialization
* to be placed in the same namespace as the template.
* It has to be put in the global namespace to assure the correct
* namespace Common is referenced.
*/
#define DECLARE_SINGLETON(T) \
namespace Common { \
template<> T *Singleton<T>::_singleton = 0; \
} // End of namespace Common
} // End of namespace Common
#endif
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