/*

 * Copyright (C) 2006, 2007, 2009, 2010 Apple Inc. All rights reserved.

 *

 * This library is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Library General Public

 * License as published by the Free Software Foundation; either

 * version 2 of the License, or (at your option) any later version.

 *

 * This library 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

 * Library General Public License for more details.

 *

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

 * along with this library; see the file COPYING.LIB.  If not, write to

 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,

 * Boston, MA 02110-1301, USA.

 *

 */

#ifndef TreeShared_h

#define TreeShared_h

#include <wtf/Assertions.h>

#include <wtf/Noncopyable.h>

#include <wtf/Threading.h>

namespace WebCore {

#ifndef NDEBUG

template<typename T> class TreeShared;

template<typename T> void adopted(TreeShared<T>*);

#endif

template<typename T> class TreeShared : public Noncopyable {

public:

    TreeShared(int initialRefCount = 1)

        : m_refCount(initialRefCount)

        , m_parent(0)

#ifndef NDEBUG

        , m_adoptionIsRequired(initialRefCount == 1)

#endif

    {

        ASSERT(isMainThread());

#ifndef NDEBUG

        m_deletionHasBegun = false;

        m_inRemovedLastRefFunction = false;

#endif

    }

    virtual ~TreeShared()

    {

        ASSERT(isMainThread());

        ASSERT(!m_refCount);

        ASSERT(m_deletionHasBegun);

        ASSERT(!m_adoptionIsRequired);

    }

    void ref()

    {

        ASSERT(isMainThread());

        ASSERT(!m_deletionHasBegun);

        ASSERT(!m_inRemovedLastRefFunction);

        ASSERT(!m_adoptionIsRequired);

        ++m_refCount;

    }

    void deref()

    {

        ASSERT(isMainThread());

        ASSERT(m_refCount >= 0);

        ASSERT(!m_deletionHasBegun);

        ASSERT(!m_inRemovedLastRefFunction);

        ASSERT(!m_adoptionIsRequired);

        if (--m_refCount <= 0 && !m_parent) {

#ifndef NDEBUG

            m_inRemovedLastRefFunction = true;

#endif

            removedLastRef();

        }

    }

    bool hasOneRef() const

    {

        ASSERT(!m_deletionHasBegun);

        ASSERT(!m_inRemovedLastRefFunction);

        return m_refCount == 1;

    }

    int refCount() const

    {

        return m_refCount;

    }

    void setParent(T* parent)

    { 

        ASSERT(isMainThread());

        m_parent = parent; 

    }

    T* parent() const

    {

        ASSERT(isMainThread());

        return m_parent;

    }

#ifndef NDEBUG

    bool m_deletionHasBegun;

    bool m_inRemovedLastRefFunction;

#endif

private:

#ifndef NDEBUG

    friend void adopted<>(TreeShared<T>*);

#endif

    virtual void removedLastRef()

    {

#ifndef NDEBUG

        m_deletionHasBegun = true;

#endif

        delete this;

    }

    int m_refCount;

    T* m_parent;

#ifndef NDEBUG

    bool m_adoptionIsRequired;

#endif

};

#ifndef NDEBUG

template<typename T> inline void adopted(TreeShared<T>* object)

{

    if (!object)

        return;

    ASSERT(!object->m_deletionHasBegun);

    ASSERT(!object->m_inRemovedLastRefFunction);

    object->m_adoptionIsRequired = false;

}

#endif

}

#endif // TreeShared.h