#ifndef BOOST_SMART_PTR_DETAIL_SP_COUNTED_BASE_SYNC_HPP_INCLUDED

#define BOOST_SMART_PTR_DETAIL_SP_COUNTED_BASE_SYNC_HPP_INCLUDED

// MS compatible compilers support #pragma once

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

# pragma once

#endif

//  detail/sp_counted_base_sync.hpp - g++ 4.1+ __sync intrinsics

//

//  Copyright (c) 2007 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

#include <boost/detail/sp_typeinfo.hpp>

#include <limits.h>

#if defined( __ia64__ ) && defined( __INTEL_COMPILER )

# include <ia64intrin.h>

#endif

namespace boost

{

namespace detail

{

#if INT_MAX >= 2147483647

typedef int sp_int32_t;

#else

typedef long sp_int32_t;

#endif

inline void atomic_increment( sp_int32_t * pw )

{

    __sync_fetch_and_add( pw, 1 );

}

inline sp_int32_t atomic_decrement( sp_int32_t * pw )

{

    return __sync_fetch_and_add( pw, -1 );

}

inline sp_int32_t atomic_conditional_increment( sp_int32_t * pw )

{

    // long r = *pw;

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

    // return r;

    sp_int32_t r = *pw;

    for( ;; )

    {

        if( r == 0 )

        {

            return r;

        }

        sp_int32_t r2 = __sync_val_compare_and_swap( pw, r, r + 1 );

        if( r2 == r )

        {

            return r;

        }

        else

        {

            r = r2;

        }

    }    

}

class sp_counted_base

{

private:

    sp_counted_base( sp_counted_base const & );

    sp_counted_base & operator= ( sp_counted_base const & );

    sp_int32_t use_count_;        // #shared

    sp_int32_t 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( sp_typeinfo 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_decrement( &use_count_ ) == 1 )

        {

            dispose();

            weak_release();

        }

    }

    void weak_add_ref() // nothrow

    {

        atomic_increment( &weak_count_ );

    }

    void weak_release() // nothrow

    {

        if( atomic_decrement( &weak_count_ ) == 1 )

        {

            destroy();

        }

    }

    long use_count() const // nothrow

    {

        return const_cast< sp_int32_t const volatile & >( use_count_ );

    }

};

} // namespace detail

} // namespace boost

#endif  // #ifndef BOOST_SMART_PTR_DETAIL_SP_COUNTED_BASE_SYNC_HPP_INCLUDED