COWIntrusiveCountableBase.hpp

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00001 /*******************************************************************************
00002 * Copyright (C) 2004 Vintela, Inc. All rights reserved.
00003 * Copyright (C) 2005 Novell, Inc. All rights reserved.
00004 *
00005 * Redistribution and use in source and binary forms, with or without
00006 * modification, are permitted provided that the following conditions are met:
00007 *
00008 *  - Redistributions of source code must retain the above copyright notice,
00009 *    this list of conditions and the following disclaimer.
00010 *
00011 *  - Redistributions in binary form must reproduce the above copyright notice,
00012 *    this list of conditions and the following disclaimer in the documentation
00013 *    and/or other materials provided with the distribution.
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00015 *  - Neither the name of Vintela, Inc., Novell, Inc., nor the names of its
00016 *    contributors may be used to endorse or promote products derived from this
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00019 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS IS''
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00031 
00032 
00037 //
00038 //  Copyright (c) 2001, 2002 Peter Dimov
00039 //
00040 //  Permission to copy, use, modify, sell and distribute this software
00041 //  is granted provided this copyright notice appears in all copies.
00042 //  This software is provided "as is" without express or implied
00043 //  warranty, and with no claim as to its suitability for any purpose.
00044 //
00045 
00046 #ifndef BLOCXX_COW_INTRUSIVE_COUNTABLE_BASE_HPP_INCLUDE_GUARD_
00047 #define BLOCXX_COW_INTRUSIVE_COUNTABLE_BASE_HPP_INCLUDE_GUARD_
00048 
00049 #include "blocxx/BLOCXX_config.h"
00050 #include "blocxx/RefCount.hpp"
00051 
00052 namespace BLOCXX_NAMESPACE
00053 {
00054 
00071 class COWIntrusiveCountableBase; 
00072 void COWIntrusiveReferenceAddRef(COWIntrusiveCountableBase * p); 
00073 void COWIntrusiveReferenceRelease(COWIntrusiveCountableBase * p); 
00074 bool COWIntrusiveReferenceUnique(COWIntrusiveCountableBase* p); 
00075 template <typename T> T* COWIntrusiveReferenceClone(T* p); 
00076 
00077 class BLOCXX_COMMON_API COWIntrusiveCountableBase
00078 {
00079 private:
00080    RefCount m_usecount;
00081 
00082 protected:
00086    COWIntrusiveCountableBase(COWIntrusiveCountableBase const &)
00087       : m_usecount(0)
00088    {
00089    }
00090 
00094    COWIntrusiveCountableBase(): m_usecount(0)
00095    {
00096    }
00097 
00103    COWIntrusiveCountableBase& operator=(COWIntrusiveCountableBase const &x)
00104    {
00105       // don't assign or change the ref count, since it won't be different.
00106       return *this;
00107    }
00108 
00112    virtual ~COWIntrusiveCountableBase();
00113 
00117    RefCount getRefCount() const
00118    {
00119       return m_usecount;
00120    }
00121 
00122 public:
00123 
00129    inline friend void COWIntrusiveReferenceAddRef(COWIntrusiveCountableBase * p)
00130    {
00131       p->m_usecount.inc();
00132    }
00133 
00141    inline friend void COWIntrusiveReferenceRelease(COWIntrusiveCountableBase * p)
00142    {
00143       if (p->m_usecount.decAndTest())
00144          delete p;
00145    }
00146    
00153    inline friend bool COWIntrusiveReferenceUnique(COWIntrusiveCountableBase* p)
00154    {
00155       return p->m_usecount.get() == 1;
00156    }
00157 
00164    template <typename T>
00165    friend T* COWIntrusiveReferenceClone(T* p); 
00166 }; 
00167 
00168 template <typename T>
00169 inline T* COWIntrusiveReferenceClone(T* p)
00170 {
00171    // this needs to happen first to avoid a race condition between 
00172    // another thread deleting the object and this one making a copy.
00173    T* tmp = p->clone();
00174    if (p->m_usecount.decAndTest())
00175    {
00176       // only copy--don't need to clone, also not a race condition.
00177       // undo the decAndTest.
00178       p->m_usecount.inc();
00179       delete tmp; // we won't need this anymore.
00180       return p;
00181    }
00182    else
00183    {
00184       // need to become unique
00185       if (tmp)
00186          COWIntrusiveReferenceAddRef(tmp);
00187       return tmp;
00188    }
00189 }
00190 
00191 } // end namespace BLOCXX_NAMESPACE
00192 
00193 #endif
00194 
00195 

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