/*

* Copyright (c) 2010 Nokia Corporation and/or its subsidiary(-ies).

* All rights reserved.

*

* This program is free software: you can redistribute it and/or modify

* it under the terms of the GNU Lesser General Public License as published by

* the Free Software Foundation, version 2.1 of the License.

* 

* 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 Lesser General Public License for more details.

*

* You should have received a copy of the GNU Lesser General Public License

* along with this program.  If not, 

* see "http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html/".

*

* Description:

*  This defines both Meyers Singleton and Gamma Singleton template.

*/

#ifndef __SINGLETON_H

#define __SINGLETON_H

/* 

 * This is how a Gamma Singleton would instantiate its object.

 */

template <class T> struct CreateGamma {

    static T* Create() { return new T; }

};

/* 

 * This is how a Meyers Singleton would instantiate its object.

 */

template <class T> struct CreateMeyers {

    static T* Create() {

        static T _instance;

        return &_instance;

    }

};

/*

 * This Singleton class accepts different creation policies.

 */

template <class T, template<class> class CreationPolicy=CreateMeyers>

class Singleton {

public:

    static T& Instance() {

        if (!m_pInstance)

            m_pInstance=CreationPolicy<T>::Create();

        return *m_pInstance;

}

private:

    Singleton();           // hide constrcutor

    ~Singleton();          // hide desctructor

    Singleton(Singleton const&);    // hide copy constructor

    Singleton& operator=(Singleton const&);  // hide assignment operator

    static T* m_pInstance;

};

template <class T, template<class> class C>

T* Singleton<T,C>::m_pInstance=0;

#endif // __SINGLETON_H