OW_SharedLibraryReference.hpp

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#ifndef OW_SHARED_LIBRARY_REFERENCE_HPP_
#define OW_SHARED_LIBRARY_REFERENCE_HPP_
#include "OW_config.h"
#include "OW_SharedLibrary.hpp"

namespace OW_NAMESPACE
{

template <class T>
class SharedLibraryReference
{
public:
   typedef T element_type;

   SharedLibraryReference(const SharedLibraryRef& lib, const T& obj)
   : m_sharedLib(lib), m_obj(obj)
   {}
   SharedLibraryReference(const SharedLibraryRef& lib, typename T::element_type* obj)
   : m_sharedLib(lib), m_obj(T(obj))
   {}
   SharedLibraryReference(const SharedLibraryReference<T>& arg)
   : m_sharedLib(arg.m_sharedLib), m_obj(arg.m_obj)
   {
   }
   /* construct out of a reference to a derived type.  U should be
   derived from T */
   template <class U>
   SharedLibraryReference(const SharedLibraryReference<U>& arg)
   : m_sharedLib(arg.m_sharedLib), m_obj(arg.m_obj)
   {
   }
   SharedLibraryReference()
   : m_sharedLib(), m_obj()
   {}
   SharedLibraryReference<T>& operator=(const SharedLibraryReference<T>& arg)
   {
      m_obj = arg.m_obj;
      m_sharedLib = arg.m_sharedLib;
      return *this;
   }
   ~SharedLibraryReference()
   {
      try
      {
         m_obj = 0;
         m_sharedLib = 0;
      }
      catch (...)
      {
         // don't let exceptions escape
      }
   }
   SharedLibraryRef getLibRef() const
   {
      return m_sharedLib;
   }
   typename T::element_type* operator->() const
   {
      return &*m_obj;
   }
   T get() const
   {
      return m_obj;
   }
   
   typedef T SharedLibraryReference::*safe_bool;
   operator safe_bool () const
      {  return (m_obj) ? &SharedLibraryReference::m_obj : 0; }
   bool operator!() const
      {  return !m_obj; }
   void setNull()
   {
      m_obj = 0;
      m_sharedLib = 0;
   }
   
   template <class U>
   SharedLibraryReference<U> cast_to() const
   {
      SharedLibraryReference<U> rval;
      rval.m_sharedLib = m_sharedLib;
      rval.m_obj = m_obj.cast_to<U>();
      return rval;
   }

   OW_DEPRECATED bool isNull() const // in 3.1.0
   {
      return !m_obj;
   }

#if !defined(__GNUC__) || __GNUC__ > 2 // causes gcc 2.95 to ICE
   /* This is so cast_to will work */
   template <class U> friend class SharedLibraryReference;

private:
#endif

   SharedLibraryRef m_sharedLib;
   T m_obj;
};

} // end namespace OW_NAMESPACE

#endif

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