Home | History | Annotate | Download | only in wtf 
      1 /*
      2  * Copyright (C) 2007, 2008, 2010 Apple Inc. All rights reserved.
      3  * Copyright (C) 2007 Justin Haygood (jhaygood (at) 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;
     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
    100