third_party/WebKit/Source/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 ThreadSafeRefCounted_h
#define ThreadSafeRefCounted_h

#include "wtf/Allocator.h"
#include "wtf/Atomics.h"
#include "wtf/DynamicAnnotations.h"
#include "wtf/Noncopyable.h"
#include "wtf/WTFExport.h"

namespace WTF {

class WTF_EXPORT ThreadSafeRefCountedBase {
  WTF_MAKE_NONCOPYABLE(ThreadSafeRefCountedBase);
  USING_FAST_MALLOC(ThreadSafeRefCountedBase);

 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  // ThreadSafeRefCounted_h