Source/JavaScriptCore/wtf/RefCounted.h

/*
 * Copyright (C) 2006, 2007, 2008, 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 RefCounted_h
#define RefCounted_h

#include "Assertions.h"
#include "FastAllocBase.h"
#include "Noncopyable.h"

namespace WTF {

// This base class holds the non-template methods and attributes.
// The RefCounted class inherits from it reducing the template bloat
// generated by the compiler (technique called template hoisting).
class RefCountedBase {
public:
    void ref()
    {
        ASSERT(!m_deletionHasBegun);
        ASSERT(!m_adoptionIsRequired);
        ++m_refCount;
    }

    bool hasOneRef() const
    {
        ASSERT(!m_deletionHasBegun);
        return m_refCount == 1;
    }

    int refCount() const
    {
        return m_refCount;
    }

    void relaxAdoptionRequirement()
    {
#ifndef NDEBUG
        ASSERT(!m_deletionHasBegun);
        ASSERT(m_adoptionIsRequired);
        m_adoptionIsRequired = false;
#endif
    }

    // Helper for generating JIT code. Please do not use for non-JIT purposes.
    const int* addressOfCount() const
    {
        return &m_refCount;
    }

protected:
    RefCountedBase()
        : m_refCount(1)
#ifndef NDEBUG
        , m_deletionHasBegun(false)
        , m_adoptionIsRequired(true)
#endif
    {
    }

    ~RefCountedBase()
    {
        ASSERT(m_deletionHasBegun);
        ASSERT(!m_adoptionIsRequired);
    }

    // Returns whether the pointer should be freed or not.
    bool derefBase()
    {
        ASSERT(!m_deletionHasBegun);
        ASSERT(!m_adoptionIsRequired);

        ASSERT(m_refCount > 0);
        if (m_refCount == 1) {
#ifndef NDEBUG
            m_deletionHasBegun = true;
#endif
            return true;
        }

        --m_refCount;
        return false;
    }

#ifndef NDEBUG
    bool deletionHasBegun() const
    {
        return m_deletionHasBegun;
    }
#endif

private:
    template<typename T> friend class CrossThreadRefCounted;

#ifndef NDEBUG
    friend void adopted(RefCountedBase*);
#endif

    int m_refCount;
#ifndef NDEBUG
    bool m_deletionHasBegun;
    bool m_adoptionIsRequired;
#endif
};

#ifndef NDEBUG

inline void adopted(RefCountedBase* object)
{
    if (!object)
        return;
    ASSERT(!object->m_deletionHasBegun);
    object->m_adoptionIsRequired = false;
}

#endif

template<typename T> class RefCounted : public RefCountedBase {
    WTF_MAKE_NONCOPYABLE(RefCounted); WTF_MAKE_FAST_ALLOCATED;
public:
    void deref()
    {
        if (derefBase())
            delete static_cast<T*>(this);
    }

protected:
    RefCounted() { }
    ~RefCounted()
    {
    }
};

template<typename T> class RefCountedCustomAllocated : public RefCountedBase {
    WTF_MAKE_NONCOPYABLE(RefCountedCustomAllocated);

public:
    void deref()
    {
        if (derefBase())
            delete static_cast<T*>(this);
    }

protected:
    ~RefCountedCustomAllocated()
    {
    }
};

} // namespace WTF

using WTF::RefCounted;
using WTF::RefCountedCustomAllocated;

#endif // RefCounted_h