GlobalPtr.hpp

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* Copyright (C) 2006, Novell, Inc. All rights reserved.
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#ifndef BLOCXX_GLOBAL_PTR_HPP_INCLUDE_GUARD_
#define BLOCXX_GLOBAL_PTR_HPP_INCLUDE_GUARD_
#include "blocxx/BLOCXX_config.h"
#include "blocxx/ThreadOnce.hpp"
#include "blocxx/SafeBool.hpp"

namespace BLOCXX_NAMESPACE
{
   template <typename T>
   struct DefaultConstructorFactory
   {
      static T* create()
      {
         return new T;
      }
   };

   template <typename T, typename FactoryT = DefaultConstructorFactory<T> >
   class GlobalPtr
   {
   private:
      struct InitPtr
      {
         InitPtr(T*& p)
         : m_p(p)
         {}
         T*& m_p;

         void operator()()
         {
            m_p = static_cast<T*>(FactoryT::create());
         }
      };

   public:
      T* get() const
      {
         callOnce(m_onceFlag, InitPtr(m_p));

         return m_p;
      }

      T* set(T* newP)
      {
         T* oldP = get();
         m_p = newP;
         return oldP;
      }

      BLOCXX_SAFE_BOOL_IMPL(GlobalPtr, T*, GlobalPtr::m_p, get() != 0);

      T & operator*() const
      {
         return *get();
      }
      T * operator->() const
      {
         return get();
      }
      

      // These members should be treated as private. They aren't marked private because if they are, POD initializaer syntax can't be used.
      mutable T* m_p;
      mutable OnceFlag m_onceFlag;
   };

#define BLOCXX_GLOBAL_PTR_INIT { 0, BLOCXX_ONCE_INIT }


} // end namespace BLOCXX_NAMESPACE


#endif