boost/detail/sp_counted_base_w32.hpp
#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 "sp_typeinfo.hpp"
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( sp_typeinfo 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