OW_COWIntrusiveReference.hpp

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//
//  Copyright (c) 2001, 2002 Peter Dimov
//
//  Permission to copy, use, modify, sell and distribute this software
//  is granted provided this copyright notice appears in all copies.
//  This software is provided "as is" without express or implied
//  warranty, and with no claim as to its suitability for any purpose.
//

#ifndef OW_COW_INTRUSIVE_REFERENCE_HPP_INCLUDE_GUARD_
#define OW_COW_INTRUSIVE_REFERENCE_HPP_INCLUDE_GUARD_

#include "OW_config.h"

namespace OW_NAMESPACE
{

#ifdef OW_CHECK_NULL_REFERENCES
namespace COWIntrusiveReferenceHelpers
{
   // these are not part of COWIntrusiveReference to try and avoid template bloat.
   OW_COMMON_API void throwNULLException();
   inline void checkNull(const void* p)
   {
      if (p == 0)
      {
         throwNULLException();
      }
   }
}
#endif

template<class T> class COWIntrusiveReference
{
private:
   typedef COWIntrusiveReference this_type;
public:
   typedef T element_type;

   COWIntrusiveReference(): m_pObj(0)
   {
   }
   COWIntrusiveReference(T * p, bool addRef = true): m_pObj(p)
   {
      if (m_pObj != 0 && addRef) COWIntrusiveReferenceAddRef(m_pObj);
   }
   template<class U> COWIntrusiveReference(COWIntrusiveReference<U> const & rhs): m_pObj(rhs.m_pObj)
   {
      if (m_pObj != 0) COWIntrusiveReferenceAddRef(m_pObj);
   }
   COWIntrusiveReference(COWIntrusiveReference const & rhs): m_pObj(rhs.m_pObj)
   {
      if (m_pObj != 0) COWIntrusiveReferenceAddRef(m_pObj);
   }
   ~COWIntrusiveReference()
   {
      if (m_pObj != 0) COWIntrusiveReferenceRelease(m_pObj);
   }
   template<class U> COWIntrusiveReference & operator=(COWIntrusiveReference<U> const & rhs)
   {
      this_type(rhs).swap(*this);
      return *this;
   }
   COWIntrusiveReference & operator=(COWIntrusiveReference const & rhs)
   {
      this_type(rhs).swap(*this);
      return *this;
   }
   COWIntrusiveReference & operator=(T * rhs)
   {
      this_type(rhs).swap(*this);
      return *this;
   }
   const T * getPtr() const
   {
      return m_pObj;
   }
   
   const T & operator*() const
   {
#ifdef OW_CHECK_NULL_REFERENCES
      COWIntrusiveReferenceHelpers::checkNull(this);
      COWIntrusiveReferenceHelpers::checkNull(m_pObj);
#endif
      return *m_pObj;
   }
   
   const T * operator->() const
   {
#ifdef OW_CHECK_NULL_REFERENCES
      COWIntrusiveReferenceHelpers::checkNull(this);
      COWIntrusiveReferenceHelpers::checkNull(m_pObj);
#endif
      return m_pObj;
   }

   T & operator*()
   {
#ifdef OW_CHECK_NULL_REFERENCES
      COWIntrusiveReferenceHelpers::checkNull(this);
      COWIntrusiveReferenceHelpers::checkNull(m_pObj);
#endif
      getWriteLock();
      return *m_pObj;
   }
   
   T * operator->()
   {
#ifdef OW_CHECK_NULL_REFERENCES
      COWIntrusiveReferenceHelpers::checkNull(this);
      COWIntrusiveReferenceHelpers::checkNull(m_pObj);
#endif
      getWriteLock();
      return m_pObj;
   }

   typedef T * this_type::*unspecified_bool_type;
   operator unspecified_bool_type () const
   {
      return m_pObj == 0? 0: &this_type::m_pObj;
   }

   bool operator! () const
   {
      return m_pObj == 0;
   }
   
   void swap(COWIntrusiveReference & rhs)
   {
      T * tmp = m_pObj;
      m_pObj = rhs.m_pObj;
      rhs.m_pObj = tmp;
   }

#if !defined(__GNUC__) || __GNUC__ > 2 // causes gcc 2.95 to ICE
   /* This is so the templated constructor will work */
   template <class U> friend class COWIntrusiveReference;
private:
#endif

   void getWriteLock()
   {
      if ((m_pObj != 0) && !COWIntrusiveReferenceUnique(m_pObj))
      {
         m_pObj = COWIntrusiveReferenceClone(m_pObj);
      }
   }


   T * m_pObj;
};
template<class T, class U> inline bool operator==(COWIntrusiveReference<T> const & a, COWIntrusiveReference<U> const & b)
{
   return a.getPtr() == b.getPtr();
}
template<class T, class U> inline bool operator!=(COWIntrusiveReference<T> const & a, COWIntrusiveReference<U> const & b)
{
   return a.getPtr() != b.getPtr();
}
template<class T> inline bool operator==(COWIntrusiveReference<T> const & a, const T * b)
{
   return a.getPtr() == b;
}
template<class T> inline bool operator!=(COWIntrusiveReference<T> const & a, const T * b)
{
   return a.getPtr() != b;
}
template<class T> inline bool operator==(const T * a, COWIntrusiveReference<T> const & b)
{
   return a == b.getPtr();
}
template<class T> inline bool operator!=(const T * a, COWIntrusiveReference<T> const & b)
{
   return a != b.getPtr();
}
#if __GNUC__ == 2 && __GNUC_MINOR__ <= 96
// Resolve the ambiguity between our op!= and the one in rel_ops
template<class T> inline bool operator!=(COWIntrusiveReference<T> const & a, COWIntrusiveReference<T> const & b)
{
   return a.getPtr() != b.getPtr();
}
#endif
template<class T> inline bool operator<(COWIntrusiveReference<T> const & a, COWIntrusiveReference<T> const & b)
{
   return a.getPtr() < b.getPtr();
}
template<class T> void swap(COWIntrusiveReference<T> & lhs, COWIntrusiveReference<T> & rhs)
{
   lhs.swap(rhs);
}

} // end namespace OW_NAMESPACE

#endif

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