boost/ptr_container/nullable.hpp

0001 //
0002 // Boost.Pointer Container
0003 //
0004 //  Copyright Thorsten Ottosen 2003-2005. Use, modification and
0005 //  distribution is subject to the Boost Software License, Version
0006 //  1.0. (See accompanying file LICENSE_1_0.txt or copy at
0007 //  http://www.boost.org/LICENSE_1_0.txt)
0008 //
0009 // For more information, see http://www.boost.org/libs/ptr_container/
0010 //
0011
0012
0013 #ifndef BOOST_INDIRECT_CONTAINER_NULLABLE_HPP
0014 #define BOOST_INDIRECT_CONTAINER_NULLABLE_HPP
0015
0016 #if defined(_MSC_VER) && (_MSC_VER >= 1200)
0017 # pragma once
0018 #endif
0019
0020 #include <boost/type_traits/detail/yes_no_type.hpp>
0021 #include <boost/type_traits/is_const.hpp>
0022 #include <boost/mpl/eval_if.hpp>
0023 #include <boost/mpl/identity.hpp>
0024 #include <boost/config.hpp>
0025
0026 namespace boost
0027 {
0028
0029     template< class T >
0030     struct nullable
0031     {
0032         typedef T type;
0033     };
0034
0035     namespace ptr_container_detail
0036     {
0037         template< class T >
0038         type_traits::yes_type is_nullable( const nullable<T>* );
0039
0040         type_traits::no_type is_nullable( ... );
0041     }
0042
0043     template< class T >
0044     struct is_nullable
0045     {
0046     private:
0047             BOOST_STATIC_CONSTANT( T*, var );
0048     public:
0049
0050 #if BOOST_WORKAROUND(BOOST_MSVC, >= 1400)
0051 #pragma warning(push)
0052 #pragma warning(disable:6334)
0053 #endif
0054
0055             BOOST_STATIC_CONSTANT(bool, value = sizeof( ptr_container_detail::is_nullable( var ) )
0056                                                 == sizeof( type_traits::yes_type ) );
0057 #if BOOST_WORKAROUND(BOOST_MSVC, >= 1400)
0058 #pragma warning(pop)
0059 #endif
0060
0061     };
0062
0063     template< class T >
0064     struct remove_nullable
0065     {
0066         typedef BOOST_DEDUCED_TYPENAME mpl::eval_if< is_nullable<T>,
0067                                                       T,
0068                                             mpl::identity<T> >::type
0069             type;
0070     };
0071
0072     namespace ptr_container_detail
0073     {
0074         template< class T >
0075         struct void_ptr
0076         {
0077             typedef BOOST_DEDUCED_TYPENAME
0078                 mpl::if_c< boost::is_const<
0079                               BOOST_DEDUCED_TYPENAME boost::remove_nullable<T>::type >::value,
0080                            const void*, void* >::type type;
0081         };
0082     }
0083 }
0084
0085 #endif