1 //-----------------------------------------------------------------------------
2 // boost variant/detail/initializer.hpp header file
3 // See http://www.boost.org for updates, documentation, and revision history.
4 //-----------------------------------------------------------------------------
5 //
6 // Copyright (c) 2002-2003
7 // Eric Friedman, Itay Maman
8 //
9 // Distributed under the Boost Software License, Version 1.0. (See
10 // accompanying file LICENSE_1_0.txt or copy at
11 // http://www.boost.org/LICENSE_1_0.txt)
12 
13 #ifndef BOOST_VARIANT_DETAIL_INITIALIZER_HPP
14 #define BOOST_VARIANT_DETAIL_INITIALIZER_HPP
15 
16 #include <new> // for placement new
17 
18 #include <boost/config.hpp>
19 
20 #include <boost/call_traits.hpp>
21 #include <boost/detail/reference_content.hpp>
22 #include <boost/variant/recursive_wrapper_fwd.hpp>
23 #include <boost/variant/detail/move.hpp>
24 
25 #if !defined(BOOST_NO_USING_DECLARATION_OVERLOADS_FROM_TYPENAME_BASE)
26 #   include <boost/mpl/aux_/value_wknd.hpp>
27 #   include <boost/mpl/int.hpp>
28 #   include <boost/mpl/iter_fold.hpp>
29 #   include <boost/mpl/next.hpp>
30 #   include <boost/mpl/deref.hpp>
31 #   include <boost/mpl/pair.hpp>
32 #   include <boost/mpl/protect.hpp>
33 #else
34 #   include <boost/variant/variant_fwd.hpp>
35 #   include <boost/preprocessor/cat.hpp>
36 #   include <boost/preprocessor/enum.hpp>
37 #   include <boost/preprocessor/repeat.hpp>
38 #endif
39 
40 namespace boost {
41 namespace detail { namespace variant {
42 
43 ///////////////////////////////////////////////////////////////////////////////
44 // (detail) support to simulate standard overload resolution rules
45 //
46 // The below initializers allows variant to follow standard overload
47 // resolution rules over the specified set of bounded types.
48 //
49 // On compilers where using declarations in class templates can correctly
50 // avoid name hiding, use an optimal solution based on the variant's typelist.
51 //
52 // Otherwise, use a preprocessor workaround based on knowledge of the fixed
53 // size of the variant's psuedo-variadic template parameter list.
54 //
55 
56 #if !defined(BOOST_NO_USING_DECLARATION_OVERLOADS_FROM_TYPENAME_BASE)
57 
58 // (detail) quoted metafunction make_initializer_node
59 //
60 // Exposes a pair whose first type is a node in the initializer hierarchy.
61 //
62 struct make_initializer_node
63 {
64     template <typename BaseIndexPair, typename Iterator>
65     struct apply
66     {
67     private: // helpers, for metafunction result (below)
68 
69         typedef typename BaseIndexPair::first
70             base;
71         typedef typename BaseIndexPair::second
72             index;
73 
74         class initializer_node
75             : public base
76         {
77         private: // helpers, for static functions (below)
78 
79             typedef typename mpl::deref<Iterator>::type
80                 recursive_enabled_T;
81             typedef typename unwrap_recursive<recursive_enabled_T>::type
82                 public_T;
83 
84 #ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
85             typedef boost::is_reference<public_T>
86                 is_reference_content_t;
87 
88             typedef typename boost::mpl::if_<is_reference_content_t, public_T, const public_T& >::type
89                 param_T;
90 
91             template <class T> struct disable_overload{};
92 
93             typedef typename boost::mpl::if_<is_reference_content_t, disable_overload<public_T>, public_T&& >::type
94                 param2_T;
95 #else
96             typedef typename call_traits<public_T>::param_type
97                 param_T;
98 #endif
99 
100         public: // static functions
101 
102             using base::initialize;
103 
initialize(void * dest,param_T operand)104             static int initialize(void* dest, param_T operand)
105             {
106                 typedef typename boost::detail::make_reference_content<
107                       recursive_enabled_T
108                     >::type internal_T;
109 
110                 new(dest) internal_T(operand);
111                 return BOOST_MPL_AUX_VALUE_WKND(index)::value; // which
112             }
113 
114 #ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
initialize(void * dest,param2_T operand)115             static int initialize(void* dest, param2_T operand)
116             {
117                 // This assert must newer trigger, because all the reference contents are
118                 // handled by the initilize(void* dest, param_T operand) function above
119                 BOOST_ASSERT(!is_reference_content_t::value);
120 
121                 typedef typename boost::mpl::if_<is_reference_content_t, param2_T, recursive_enabled_T>::type value_T;
122                 new(dest) value_T( boost::detail::variant::move(operand) );
123                 return BOOST_MPL_AUX_VALUE_WKND(index)::value; // which
124             }
125 #endif
126         };
127 
128         friend class initializer_node;
129 
130     public: // metafunction result
131 
132         typedef mpl::pair<
133               initializer_node
134             , typename mpl::next< index >::type
135             > type;
136 
137     };
138 };
139 
140 // (detail) class initializer_root
141 //
142 // Every level of the initializer hierarchy must expose the name
143 // "initialize," so initializer_root provides a dummy function:
144 //
145 class initializer_root
146 {
147 public: // static functions
148 
149     static void initialize();
150 
151 };
152 
153 #else // defined(BOOST_NO_USING_DECLARATION_OVERLOADS_FROM_TYPENAME_BASE)
154 
155     // Obsolete. Remove.
156     #define BOOST_VARIANT_AUX_PP_INITIALIZER_TEMPLATE_PARAMS \
157           BOOST_VARIANT_ENUM_PARAMS(typename recursive_enabled_T) \
158     /**/
159 
160     // Obsolete. Remove.
161     #define BOOST_VARIANT_AUX_PP_INITIALIZER_DEFINE_PARAM_T(N) \
162         typedef typename unwrap_recursive< \
163               BOOST_PP_CAT(recursive_enabled_T,N) \
164             >::type BOOST_PP_CAT(public_T,N); \
165         typedef typename call_traits< \
166               BOOST_PP_CAT(public_T,N) \
167             >::param_type BOOST_PP_CAT(param_T,N); \
168     /**/
169 
170 template < BOOST_VARIANT_ENUM_PARAMS(typename recursive_enabled_T) >
171 struct preprocessor_list_initializer
172 {
173 public: // static functions
174 
175     #define BOOST_VARIANT_AUX_PP_INITIALIZE_FUNCTION(z,N,_) \
176         typedef typename unwrap_recursive< \
177               BOOST_PP_CAT(recursive_enabled_T,N) \
178             >::type BOOST_PP_CAT(public_T,N); \
179         typedef typename call_traits< \
180               BOOST_PP_CAT(public_T,N) \
181             >::param_type BOOST_PP_CAT(param_T,N); \
182         static int initialize( \
183               void* dest \
184             , BOOST_PP_CAT(param_T,N) operand \
185             ) \
186         { \
187             typedef typename boost::detail::make_reference_content< \
188                   BOOST_PP_CAT(recursive_enabled_T,N) \
189                 >::type internal_T; \
190             \
191             new(dest) internal_T(operand); \
192             return (N); /*which*/ \
193         } \
194         /**/
195 
196     BOOST_PP_REPEAT(
197           BOOST_VARIANT_LIMIT_TYPES
198         , BOOST_VARIANT_AUX_PP_INITIALIZE_FUNCTION
199         , _
200         )
201 
202     #undef BOOST_VARIANT_AUX_PP_INITIALIZE_FUNCTION
203 
204 };
205 
206 #endif // BOOST_NO_USING_DECLARATION_OVERLOADS_FROM_TYPENAME_BASE workaround
207 
208 }} // namespace detail::variant
209 } // namespace boost
210 
211 ///////////////////////////////////////////////////////////////////////////////
212 // macro BOOST_VARIANT_AUX_INITIALIZER_T
213 //
214 // Given both the variant's typelist and a basename for forming the list of
215 // bounded types (i.e., T becomes T1, T2, etc.), exposes the initializer
216 // most appropriate to the current compiler.
217 //
218 
219 #if !defined(BOOST_NO_USING_DECLARATION_OVERLOADS_FROM_TYPENAME_BASE)
220 
221 #define BOOST_VARIANT_AUX_INITIALIZER_T( mpl_seq, typename_base ) \
222     ::boost::mpl::iter_fold< \
223           mpl_seq \
224         , ::boost::mpl::pair< \
225               ::boost::detail::variant::initializer_root \
226             , ::boost::mpl::int_<0> \
227             > \
228         , ::boost::mpl::protect< \
229               ::boost::detail::variant::make_initializer_node \
230             > \
231         >::type::first \
232     /**/
233 
234 #else // defined(BOOST_NO_USING_DECLARATION_OVERLOADS_FROM_TYPENAME_BASE)
235 
236     // Obsolete. Remove.
237     #define BOOST_VARIANT_AUX_PP_INITIALIZER_TEMPLATE_ARGS(typename_base) \
238           BOOST_VARIANT_ENUM_PARAMS(typename_base) \
239         /**/
240 
241 #define BOOST_VARIANT_AUX_INITIALIZER_T( mpl_seq, typename_base ) \
242     ::boost::detail::variant::preprocessor_list_initializer< \
243           BOOST_VARIANT_ENUM_PARAMS(typename_base) \
244         > \
245     /**/
246 
247 #endif // BOOST_NO_USING_DECLARATION_OVERLOADS_FROM_TYPENAME_BASE workaround
248 
249 #endif // BOOST_VARIANT_DETAIL_INITIALIZER_HPP
250