OWBI1_IntrusiveReference.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 OWBI1_INTRUSIVE_REFERENCE_HPP_INCLUDE_GUARD_
#define OWBI1_INTRUSIVE_REFERENCE_HPP_INCLUDE_GUARD_

#include "OWBI1_config.h"

namespace OWBI1
{

//
//  IntrusiveReference
//
//  A smart pointer that uses intrusive reference counting.
//
//  Relies on unqualified calls to
//  
//      void IntrusiveReferenceAddRef(T * p);
//      void IntrusiveReferenceRelease(T * p);
//
//          (p != 0)
//
//  The object is responsible for destroying itself.
//
template<class T> class IntrusiveReference
{
private:
   typedef IntrusiveReference this_type;
public:
   typedef T element_type;

   IntrusiveReference(): m_pObj(0)
   {
   }
   IntrusiveReference(T * p, bool add_ref = true): m_pObj(p)
   {
      if (m_pObj != 0 && add_ref) IntrusiveReferenceAddRef(m_pObj);
   }
   template<class U> IntrusiveReference(IntrusiveReference<U> const & rhs): m_pObj(rhs.getPtr())
   {
      if (m_pObj != 0) IntrusiveReferenceAddRef(m_pObj);
   }
   IntrusiveReference(IntrusiveReference const & rhs): m_pObj(rhs.m_pObj)
   {
      if (m_pObj != 0) IntrusiveReferenceAddRef(m_pObj);
   }
   ~IntrusiveReference()
   {
      if (m_pObj != 0) IntrusiveReferenceRelease(m_pObj);
   }
   template<class U> IntrusiveReference & operator=(IntrusiveReference<U> const & rhs)
   {
      this_type(rhs).swap(*this);
      return *this;
   }
   IntrusiveReference & operator=(IntrusiveReference const & rhs)
   {
      this_type(rhs).swap(*this);
      return *this;
   }
   IntrusiveReference & operator=(T * rhs)
   {
      this_type(rhs).swap(*this);
      return *this;
   }
   T * getPtr() const
   {
      return m_pObj;
   }
   T & operator*() const
   {
      return *m_pObj;
   }
   T * operator->() const
   {
      return m_pObj;
   }
   typedef T * this_type::*safe_bool;
   operator safe_bool() const
   {
      return m_pObj == 0? 0: &this_type::m_pObj;
   }
   bool operator! () const
   {
      return m_pObj == 0;
   }

   void swap(IntrusiveReference & rhs)
   {
      T * tmp = m_pObj;
      m_pObj = rhs.m_pObj;
      rhs.m_pObj = tmp;
   }

   template <class U>
   IntrusiveReference<U> cast_to() const
   {
      return IntrusiveReference<U>(dynamic_cast<U*>(m_pObj));
   }

private:
   T * m_pObj;
};
template<class T, class U> inline bool operator==(IntrusiveReference<T> const & a, IntrusiveReference<U> const & b)
{
   return a.getPtr() == b.getPtr();
}
template<class T, class U> inline bool operator!=(IntrusiveReference<T> const & a, IntrusiveReference<U> const & b)
{
   return a.getPtr() != b.getPtr();
}
template<class T> inline bool operator==(IntrusiveReference<T> const & a, T * b)
{
   return a.getPtr() == b;
}
template<class T> inline bool operator!=(IntrusiveReference<T> const & a, T * b)
{
   return a.getPtr() != b;
}
template<class T> inline bool operator==(T * a, IntrusiveReference<T> const & b)
{
   return a == b.getPtr();
}
template<class T> inline bool operator!=(T * a, IntrusiveReference<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!=(IntrusiveReference<T> const & a, IntrusiveReference<T> const & b)
{
   return a.getPtr() != b.getPtr();
}
#endif
template<class T> inline bool operator<(IntrusiveReference<T> const & a, IntrusiveReference<T> const & b)
{
   return a.getPtr() < b.getPtr();
}
template<class T> void swap(IntrusiveReference<T> & lhs, IntrusiveReference<T> & rhs)
{
   lhs.swap(rhs);
}
template<class T, class U> IntrusiveReference<T> static_pointer_cast(IntrusiveReference<U> const & p)
{
   return static_cast<T *>(p.getPtr());
}
template<class T, class U> IntrusiveReference<T> const_pointer_cast(IntrusiveReference<U> const & p)
{
   return const_cast<T *>(p.getPtr());
}
template<class T, class U> IntrusiveReference<T> dynamic_pointer_cast(IntrusiveReference<U> const & p)
{
   return dynamic_cast<T *>(p.getPtr());
}

} // end namespace OWBI1

#endif

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