#ifndef BOOST_DETAIL_SP_COUNTED_BASE_GCC_X86_HPP_INCLUDED

 #define BOOST_DETAIL_SP_COUNTED_BASE_GCC_X86_HPP_INCLUDED

 // MS compatible compilers support #pragma once

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

 # pragma once

 #endif

 //

 //  detail/sp_counted_base_gcc_x86.hpp - g++ on 486+ or AMD64

 //

 //  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 <typeinfo>

 namespace boost

 {

 namespace detail

 {

 inline int atomic_exchange_and_add( int * pw, int dv )

 {

     // int r = *pw;

     // *pw += dv;

     // return r;

     int r;

     __asm__ __volatile__

     (

         "lock\n\t"

         "xadd %1, %0":

         "=m"( *pw ), "=r"( r ): // outputs (%0, %1)

         "m"( *pw ), "1"( dv ): // inputs (%2, %3 == %1)

         "memory", "cc" // clobbers

     );

     return r;

 }

 inline void atomic_increment( int * pw )

 {

     //atomic_exchange_and_add( pw, 1 );

     __asm__

     (

         "lock\n\t"

         "incl %0":

         "=m"( *pw ): // output (%0)

         "m"( *pw ): // input (%1)

         "cc" // clobbers

     );

 }

 inline int atomic_conditional_increment( int * pw )

 {

     // int rv = *pw;

     // if( rv != 0 ) ++*pw;

     // return rv;

     int rv, tmp;

     __asm__

     (

         "movl %0, %%eax\n\t"

         "0:\n\t"

         "test %%eax, %%eax\n\t"

         "je 1f\n\t"

         "movl %%eax, %2\n\t"

         "incl %2\n\t"

         "lock\n\t"

         "cmpxchgl %2, %0\n\t"

         "jne 0b\n\t"

         "1:":

         "=m"( *pw ), "=&a"( rv ), "=&r"( tmp ): // outputs (%0, %1, %2)

         "m"( *pw ): // input (%3)

         "cc" // clobbers

     );

     return rv;

 }

 class sp_counted_base

 {

 private:

     sp_counted_base( sp_counted_base const & );

     sp_counted_base & operator= ( sp_counted_base const & );

     int use_count_;        // #shared

     int 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()

     {

         atomic_increment( &use_count_ );

     }

     bool add_ref_lock() // true on success

     {

         return atomic_conditional_increment( &use_count_ ) != 0;

     }

     void release() // nothrow

     {

         if( atomic_exchange_and_add( &use_count_, -1 ) == 1 )

         {

             dispose();

             weak_release();

         }

     }

     void weak_add_ref() // nothrow

     {

         atomic_increment( &weak_count_ );

     }

     void weak_release() // nothrow

     {

         if( atomic_exchange_and_add( &weak_count_, -1 ) == 1 )

         {

             destroy();

         }

     }

     long use_count() const // nothrow

     {

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

     }

 };

 } // namespace detail

 } // namespace boost

 #endif  // #ifndef BOOST_DETAIL_SP_COUNTED_BASE_GCC_X86_HPP_INCLUDED