third_party/WebKit/Source/wtf/ThreadSafeRefCounted.h

   1 /*
   2  * Copyright (C) 2007, 2008, 2010 Apple Inc. All rights reserved.
   3  * Copyright (C) 2007 Justin Haygood (jhaygood@reaktix.com)
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  *
   9  * 1.  Redistributions of source code must retain the above copyright
  10  *     notice, this list of conditions and the following disclaimer.
  11  * 2.  Redistributions in binary form must reproduce the above copyright
  12  *     notice, this list of conditions and the following disclaimer in the
  13  *     documentation and/or other materials provided with the distribution.
  14  * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
  15  *     its contributors may be used to endorse or promote products derived
  16  *     from this software without specific prior written permission.
  17  *
  18  * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
  19  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  20  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  21  * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
  22  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  23  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  24  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  25  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  26  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  27  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  28  */
  29
  30 #ifndef ThreadSafeRefCounted_h
  31 #define ThreadSafeRefCounted_h
  32
  33 #include "wtf/Atomics.h"
  34 #include "wtf/DynamicAnnotations.h"
  35 #include "wtf/FastAllocBase.h"
  36 #include "wtf/Noncopyable.h"
  37 #include "wtf/WTFExport.h"
  38
  39 namespace WTF {
  40
  41 class WTF_EXPORT ThreadSafeRefCountedBase {
  42     WTF_MAKE_NONCOPYABLE(ThreadSafeRefCountedBase);
  43     WTF_MAKE_FAST_ALLOCATED(ThreadSafeRefCountedBase);
  44 public:
  45     ThreadSafeRefCountedBase(int initialRefCount = 1)
  46         : m_refCount(initialRefCount)
  47     {
  48     }
  49
  50     void ref()
  51     {
  52         atomicIncrement(&m_refCount);
  53     }
  54
  55     bool hasOneRef()
  56     {
  57         return refCount() == 1;
  58     }
  59
  60     int refCount() const
  61     {
  62         return static_cast<int const volatile &>(m_refCount);
  63     }
  64
  65 protected:
  66     // Returns whether the pointer should be freed or not.
  67     bool derefBase()
  68     {
  69         WTF_ANNOTATE_HAPPENS_BEFORE(&m_refCount);
  70         if (atomicDecrement(&m_refCount) <= 0) {
  71             WTF_ANNOTATE_HAPPENS_AFTER(&m_refCount);
  72             return true;
  73         }
  74         return false;
  75     }
  76
  77 private:
  78     int m_refCount;
  79 };
  80
  81 template<class T> class ThreadSafeRefCounted : public ThreadSafeRefCountedBase {
  82 public:
  83     void deref()
  84     {
  85         if (derefBase())
  86             delete static_cast<T*>(this);
  87     }
  88
  89 protected:
  90     ThreadSafeRefCounted()
  91     {
  92     }
  93 };
  94
  95 } // namespace WTF
  96
  97 using WTF::ThreadSafeRefCounted;
  98
  99 #endif // ThreadSafeRefCounted_h