sky/engine/wtf/ThreadSafeRefCounted.h

/*
 * Copyright (C) 2007, 2008, 2010 Apple Inc. All rights reserved.
 * Copyright (C) 2007 Justin Haygood (jhaygood@reaktix.com)
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1.  Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 * 2.  Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
 *     its contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef SKY_ENGINE_WTF_THREADSAFEREFCOUNTED_H_
#define SKY_ENGINE_WTF_THREADSAFEREFCOUNTED_H_

#include "sky/engine/wtf/Atomics.h"
#include "sky/engine/wtf/DynamicAnnotations.h"
#include "sky/engine/wtf/FastAllocBase.h"
#include "sky/engine/wtf/Noncopyable.h"
#include "sky/engine/wtf/WTFExport.h"

namespace WTF {

class WTF_EXPORT ThreadSafeRefCountedBase {
    WTF_MAKE_NONCOPYABLE(ThreadSafeRefCountedBase);
    WTF_MAKE_FAST_ALLOCATED;
public:
    ThreadSafeRefCountedBase(int initialRefCount = 1)
        : m_refCount(initialRefCount)
    {
    }

    void ref()
    {
        atomicIncrement(&m_refCount);
    }

    bool hasOneRef()
    {
        return refCount() == 1;
    }

    int refCount() const
    {
        return static_cast<int const volatile &>(m_refCount);
    }

protected:
    // Returns whether the pointer should be freed or not.
    bool derefBase()
    {
        WTF_ANNOTATE_HAPPENS_BEFORE(&m_refCount);
        if (atomicDecrement(&m_refCount) <= 0) {
            WTF_ANNOTATE_HAPPENS_AFTER(&m_refCount);
            return true;
        }
        return false;
    }

private:
    int m_refCount;
};

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

protected:
    ThreadSafeRefCounted()
    {
    }
};

} // namespace WTF

using WTF::ThreadSafeRefCounted;

#endif  // SKY_ENGINE_WTF_THREADSAFEREFCOUNTED_H_