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1
2 // (C) Copyright Steve Cleary, Beman Dawes, Howard Hinnant & John Maddock 2000.
3 //  Use, modification and distribution are subject to the Boost Software License,
4 //  Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
5 //  http://www.boost.org/LICENSE_1_0.txt).
6 //
7 //  See http://www.boost.org/libs/type_traits for most recent version including documentation.
8
9 #ifndef BOOST_TT_IS_EMPTY_HPP_INCLUDED
10 #define BOOST_TT_IS_EMPTY_HPP_INCLUDED
11
12 #include "boost/type_traits/is_convertible.hpp"
13 #include "boost/type_traits/detail/ice_or.hpp"
14 #include "boost/type_traits/config.hpp"
15 #include "boost/type_traits/intrinsics.hpp"
16
17 #ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
18 #   include "boost/type_traits/remove_cv.hpp"
19 #   include "boost/type_traits/is_class.hpp"
20 #   include "boost/type_traits/add_reference.hpp"
21 #else
22 #   include "boost/type_traits/is_reference.hpp"
23 #   include "boost/type_traits/is_pointer.hpp"
24 #   include "boost/type_traits/is_member_pointer.hpp"
25 #   include "boost/type_traits/is_array.hpp"
26 #   include "boost/type_traits/is_void.hpp"
27 #   include "boost/type_traits/detail/ice_and.hpp"
28 #   include "boost/type_traits/detail/ice_not.hpp"
29 #endif
30
31 // should be always the last #include directive
32 #include "boost/type_traits/detail/bool_trait_def.hpp"
33
34 namespace boost {
35
36 namespace detail {
37
38 #ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
39 template <typename T>
40 struct empty_helper_t1 : public T
41 {
42     empty_helper_t1();  // hh compiler bug workaround
43     int i[256];
44 };
45
46 struct empty_helper_t2 { int i[256]; };
47
48 #if !BOOST_WORKAROUND(__BORLANDC__, < 0x600)
49
50 template <typename T, bool is_a_class = false>
51 struct empty_helper
52 {
53     BOOST_STATIC_CONSTANT(bool, value = false);
54 };
55
56 template <typename T>
57 struct empty_helper<T, true>
58 {
59     BOOST_STATIC_CONSTANT(
60         bool, value = (sizeof(empty_helper_t1<T>) == sizeof(empty_helper_t2))
61         );
62 };
63
64 template <typename T>
65 struct is_empty_impl
66 {
67     typedef typename remove_cv<T>::type cvt;
68     BOOST_STATIC_CONSTANT(
69         bool, value = (
70             ::boost::type_traits::ice_or<
71               ::boost::detail::empty_helper<cvt,::boost::is_class<T>::value>::value
72               , BOOST_IS_EMPTY(cvt)
73             >::value
74             ));
75 };
76
77 #else // __BORLANDC__
78
79 template <typename T, bool is_a_class, bool convertible_to_int>
80 struct empty_helper
81 {
82     BOOST_STATIC_CONSTANT(bool, value = false);
83 };
84
85 template <typename T>
86 struct empty_helper<T, true, false>
87 {
88     BOOST_STATIC_CONSTANT(bool, value = (
89         sizeof(empty_helper_t1<T>) == sizeof(empty_helper_t2)
90         ));
91 };
92
93 template <typename T>
94 struct is_empty_impl
95 {
96    typedef typename remove_cv<T>::type cvt;
97    typedef typename add_reference<T>::type r_type;
98
99    BOOST_STATIC_CONSTANT(
100        bool, value = (
101            ::boost::type_traits::ice_or<
102               ::boost::detail::empty_helper<
103                   cvt
104                 , ::boost::is_class<T>::value
105                 , ::boost::is_convertible< r_type,int>::value
106               >::value
107               , BOOST_IS_EMPTY(cvt)
108            >::value));
109 };
110
111 #endif // __BORLANDC__
112
113 #else // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
114
115 #ifdef BOOST_MSVC6_MEMBER_TEMPLATES
116
117 template <typename T>
118 struct empty_helper_t1 : public T
119 {
120    empty_helper_t1();
121    int i[256];
122 };
123
124 struct empty_helper_t2 { int i[256]; };
125
126 template <typename T>
127 struct empty_helper_base
128 {
129    enum { value = (sizeof(empty_helper_t1<T>) == sizeof(empty_helper_t2)) };
130 };
131
132 template <typename T>
133 struct empty_helper_nonbase
134 {
135    enum { value = false };
136 };
137
138 template <bool base>
139 struct empty_helper_chooser
140 {
141    template <typename T> struct result_
142    {
143       typedef empty_helper_nonbase<T> type;
144    };
145 };
146
147 template <>
148 struct empty_helper_chooser<true>
149 {
150    template <typename T> struct result_
151    {
152       typedef empty_helper_base<T> type;
153    };
154 };
155
156 template <typename T>
157 struct is_empty_impl
158 {
159    typedef ::boost::detail::empty_helper_chooser<
160       ::boost::type_traits::ice_and<
161          ::boost::type_traits::ice_not< ::boost::is_reference<T>::value >::value,
162          ::boost::type_traits::ice_not< ::boost::is_convertible<T,double>::value >::value,
163          ::boost::type_traits::ice_not< ::boost::is_pointer<T>::value >::value,
164          ::boost::type_traits::ice_not< ::boost::is_member_pointer<T>::value >::value,
165          ::boost::type_traits::ice_not< ::boost::is_array<T>::value >::value,
166          ::boost::type_traits::ice_not< ::boost::is_void<T>::value >::value,
167          ::boost::type_traits::ice_not<
168             ::boost::is_convertible<T,void const volatile*>::value
169             >::value
170       >::value > chooser;
171
172    typedef typename chooser::template result_<T> result;
173    typedef typename result::type eh_type;
174
175    BOOST_STATIC_CONSTANT(bool, value =
176       (::boost::type_traits::ice_or<eh_type::value, BOOST_IS_EMPTY(T)>::value));
177 };
178
179 #else
180
181 template <typename T> struct is_empty_impl
182 {
183     BOOST_STATIC_CONSTANT(bool, value = BOOST_IS_EMPTY(T));
184 };
185
186 #endif  // BOOST_MSVC6_MEMBER_TEMPLATES
187
188 #endif  // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
189
190 // these help when the compiler has no partial specialization support:
191 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_empty,void,false)
192 #ifndef BOOST_NO_CV_VOID_SPECIALIZATIONS
193 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_empty,void const,false)
194 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_empty,void volatile,false)
195 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_empty,void const volatile,false)
196 #endif
197
198 } // namespace detail
199
200 BOOST_TT_AUX_BOOL_TRAIT_DEF1(is_empty,T,::boost::detail::is_empty_impl<T>::value)
201
202 } // namespace boost
203
204 #include "boost/type_traits/detail/bool_trait_undef.hpp"
205
206 #endif // BOOST_TT_IS_EMPTY_HPP_INCLUDED
207