optional/detail/optional_swap.hpp

0001 // Copyright (C) 2003, 2008 Fernando Luis Cacciola Carballal.
0002 // Copyright (C) 2015 Andrzej Krzemienski.
0003 //
0004 // Use, modification, and distribution is subject to the Boost Software
0005 // License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
0006 // http://www.boost.org/LICENSE_1_0.txt)
0007 //
0008 // See http://www.boost.org/libs/optional for documentation.
0009 //
0010 // You are welcome to contact the author at:
0011 //  akrzemi1@gmail.com
0012
0013 #ifndef BOOST_OPTIONAL_DETAIL_OPTIONAL_SWAP_AJK_28JAN2015_HPP
0014 #define BOOST_OPTIONAL_DETAIL_OPTIONAL_SWAP_AJK_28JAN2015_HPP
0015
0016 #include <boost/core/invoke_swap.hpp>
0017 #include <boost/optional/optional_fwd.hpp>
0018
0019 namespace boost {
0020
0021 namespace optional_detail {
0022
0023 template <bool use_default_constructor> struct swap_selector;
0024
0025 template <>
0026 struct swap_selector<true>
0027 {
0028     template <class T>
0029     static void optional_swap ( optional<T>& x, optional<T>& y )
0030     {
0031         const bool hasX = !!x;
0032         const bool hasY = !!y;
0033
0034         if ( !hasX && !hasY )
0035             return;
0036
0037         if( !hasX )
0038             x.emplace();
0039         else if ( !hasY )
0040             y.emplace();
0041
0042         // Boost.Core.Swap will take care of ADL and workarounds for broken compilers
0043         boost::core::invoke_swap(x.get(), y.get());
0044
0045         if( !hasX )
0046             y = boost::none ;
0047         else if( !hasY )
0048             x = boost::none ;
0049     }
0050 };
0051
0052 #ifdef BOOST_OPTIONAL_DETAIL_MOVE
0053 # undef BOOST_OPTIONAL_DETAIL_MOVE
0054 #endif
0055
0056 #ifndef BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
0057 # define BOOST_OPTIONAL_DETAIL_MOVE(EXPR_) boost::move(EXPR_)
0058 #else
0059 # define BOOST_OPTIONAL_DETAIL_MOVE(EXPR_) EXPR_
0060 #endif
0061
0062 template <>
0063 struct swap_selector<false>
0064 {
0065     template <class T>
0066     static void optional_swap ( optional<T>& x, optional<T>& y )
0067     //BOOST_NOEXCEPT_IF(::boost::is_nothrow_move_constructible<T>::value && BOOST_NOEXCEPT_EXPR(boost::core::invoke_swap(*x, *y)))
0068     {
0069         if (x)
0070         {
0071             if (y)
0072             {
0073                 boost::core::invoke_swap(*x, *y);
0074             }
0075             else
0076             {
0077                 y = BOOST_OPTIONAL_DETAIL_MOVE(*x);
0078                 x = boost::none;
0079             }
0080         }
0081         else
0082         {
0083             if (y)
0084             {
0085                 x = BOOST_OPTIONAL_DETAIL_MOVE(*y);
0086                 y = boost::none;
0087             }
0088         }
0089     }
0090 };
0091
0092 } // namespace optional_detail
0093
0094 #if (!defined BOOST_NO_CXX11_RVALUE_REFERENCES) && (!defined BOOST_CONFIG_RESTORE_OBSOLETE_SWAP_IMPLEMENTATION)
0095
0096 template<class T>
0097 struct optional_swap_should_use_default_constructor : boost::false_type {} ;
0098
0099 #else
0100
0101 template<class T>
0102 struct optional_swap_should_use_default_constructor : has_nothrow_default_constructor<T> {} ;
0103
0104 #endif
0105
0106 template <class T>
0107 inline void swap ( optional<T>& x, optional<T>& y )
0108 //BOOST_NOEXCEPT_IF(::boost::is_nothrow_move_constructible<T>::value && BOOST_NOEXCEPT_EXPR(boost::core::invoke_swap(*x, *y)))
0109 {
0110     optional_detail::swap_selector<optional_swap_should_use_default_constructor<T>::value>::optional_swap(x, y);
0111 }
0112
0113 } // namespace boost
0114
0115 #undef BOOST_OPTIONAL_DETAIL_MOVE
0116
0117 #endif // header guard