#ifndef BOOST_DETAIL_SP_COUNTED_BASE_W32_HPP_INCLUDED

 #define BOOST_DETAIL_SP_COUNTED_BASE_W32_HPP_INCLUDED

 // MS compatible compilers support #pragma once

 #if defined(_MSC_VER) && (_MSC_VER >= 1020)

 # pragma once

 #endif

 //

 //  detail/sp_counted_base_w32.hpp

 //

 //  Copyright (c) 2001, 2002, 2003 Peter Dimov and Multi Media Ltd.

 //  Copyright 2004-2005 Peter Dimov

 //

 //  Distributed under the Boost Software License, Version 1.0. (See

 //  accompanying file LICENSE_1_0.txt or copy at

 //  http://www.boost.org/LICENSE_1_0.txt)

 //

 //

 //  Lock-free algorithm by Alexander Terekhov

 //

 //  Thanks to Ben Hitchings for the #weak + (#shared != 0)

 //  formulation

 //

 #include <boost/detail/interlocked.hpp>

 #include <boost/detail/workaround.hpp>

 #include <typeinfo>

 namespace boost

 {

 namespace detail

 {

 class sp_counted_base

 {

 private:

     sp_counted_base( sp_counted_base const & );

     sp_counted_base & operator= ( sp_counted_base const & );

     long use_count_;        // #shared

     long weak_count_;       // #weak + (#shared != 0)

 public:

     sp_counted_base(): use_count_( 1 ), weak_count_( 1 )

     {

     }

     virtual ~sp_counted_base() // nothrow

     {

     }

     // dispose() is called when use_count_ drops to zero, to release

     // the resources managed by *this.

     virtual void dispose() = 0; // nothrow

     // destroy() is called when weak_count_ drops to zero.

     virtual void destroy() // nothrow

     {

         delete this;

     }

     virtual void * get_deleter( std::type_info const & ti ) = 0;

     void add_ref_copy()

     {

         BOOST_INTERLOCKED_INCREMENT( &use_count_ );

     }

     bool add_ref_lock() // true on success

     {

         for( ;; )

         {

             long tmp = static_cast< long const volatile& >( use_count_ );

             if( tmp == 0 ) return false;

 #if defined( BOOST_MSVC ) && BOOST_WORKAROUND( BOOST_MSVC, == 1200 )

             // work around a code generation bug

             long tmp2 = tmp + 1;

             if( BOOST_INTERLOCKED_COMPARE_EXCHANGE( &use_count_, tmp2, tmp ) == tmp2 - 1 ) return true;

 #else

             if( BOOST_INTERLOCKED_COMPARE_EXCHANGE( &use_count_, tmp + 1, tmp ) == tmp ) return true;

 #endif

         }

     }

     void release() // nothrow

     {

         if( BOOST_INTERLOCKED_DECREMENT( &use_count_ ) == 0 )

         {

             dispose();

             weak_release();

         }

     }

     void weak_add_ref() // nothrow

     {

         BOOST_INTERLOCKED_INCREMENT( &weak_count_ );

     }

     void weak_release() // nothrow

     {

         if( BOOST_INTERLOCKED_DECREMENT( &weak_count_ ) == 0 )

         {

             destroy();

         }

     }

     long use_count() const // nothrow

     {

         return static_cast<long const volatile &>( use_count_ );

     }

 };

 } // namespace detail

 } // namespace boost

 #endif  // #ifndef BOOST_DETAIL_SP_COUNTED_BASE_W32_HPP_INCLUDED