singleton.h

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/* xoreos - A reimplementation of BioWare's Aurora engine
 *
 * xoreos is the legal property of its developers, whose names
 * can be found in the AUTHORS file distributed with this source
 * distribution.
 *
 * xoreos 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 3
 * of the License, or (at your option) any later version.
 *
 * xoreos 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 xoreos. If not, see <http://www.gnu.org/licenses/>.
 */

/* Based on ScummVM (<http://scummvm.org>) code, which is released
 * under the terms of version 2 or later of the GNU General Public
 * License.
 *
 * The original copyright note in ScummVM reads as follows:
 *
 * 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.
 */

#ifndef COMMON_SINGLETON_H
#define COMMON_SINGLETON_H

#include <boost/noncopyable.hpp>

namespace Common {

template<class T>
class Singleton : boost::noncopyable {
private:
    Singleton<T>(const Singleton<T> &);
    Singleton<T> &operator=(const Singleton<T> &);

    static T *_singleton;

    //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>() { }
    virtual ~Singleton<T>() { }

    typedef T SingletonBaseType;
};

#define DECLARE_SINGLETON(T) \
    namespace Common { \
    template<> T *Singleton<T>::_singleton = 0; \
    } // End of namespace Common

} // End of namespace Common

#endif // COMMON_SINGLETON_H