singleton.h

/*
 * singleton.h
 * This file is part of dbPager Classes Library (DCL)
 *
 * Copyright (c) 2008 Dennis Prochko <wolfsoft@mail.ru>
 *
 * DCL 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 version 3.
 *
 * DCL 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 DCL; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor,
 * Boston, MA  02110-1301  USA
 */

#ifndef _SINGLETON_H_
#define _SINGLETON_H_

#include <memory>

#include <dcl/mutex.h>
#include <dcl/noncopyable.h>

namespace dbp {


template <class T>
class singleton: public noncopyable {
public:

        static T& instance() {
                if (!_instance.get()) {
                        mutex_guard m(_cs);
                        if (!_instance.get())
                                _instance.reset(new T());
                        else
                                _instance->_is_copy = true;
                } else
                        _instance->_is_copy = true;
                return *_instance;
        };

        bool is_copy() {
                return _is_copy;
        };
protected:
        singleton(): _is_copy(false) { };
private:
        bool _is_copy;
        static std::auto_ptr<T> _instance;
        static mutex _cs;
};

template <class T>
std::auto_ptr<T> singleton<T>::_instance;

template <class T>
mutex singleton<T>::_cs;

} //namespace

#endif /*_SINGLETON_H_*/