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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/config.hpp> | |
14 | #include <boost/type_traits/intrinsics.hpp> | |
15 | ||
16 | #include <boost/type_traits/remove_cv.hpp> | |
17 | #include <boost/type_traits/is_class.hpp> | |
18 | #include <boost/type_traits/add_reference.hpp> | |
19 | ||
20 | #ifndef BOOST_INTERNAL_IS_EMPTY | |
21 | #define BOOST_INTERNAL_IS_EMPTY(T) false | |
22 | #else | |
23 | #define BOOST_INTERNAL_IS_EMPTY(T) BOOST_IS_EMPTY(T) | |
24 | #endif | |
25 | ||
26 | namespace boost { | |
27 | ||
28 | namespace detail { | |
29 | ||
30 | ||
31 | #ifdef BOOST_MSVC | |
32 | #pragma warning(push) | |
33 | #pragma warning(disable:4624) // destructor could not be generated | |
34 | #endif | |
35 | ||
36 | template <typename T> | |
37 | struct empty_helper_t1 : public T | |
38 | { | |
39 | empty_helper_t1(); // hh compiler bug workaround | |
40 | int i[256]; | |
41 | private: | |
42 | // suppress compiler warnings: | |
43 | empty_helper_t1(const empty_helper_t1&); | |
44 | empty_helper_t1& operator=(const empty_helper_t1&); | |
45 | }; | |
46 | ||
47 | #ifdef BOOST_MSVC | |
48 | #pragma warning(pop) | |
49 | #endif | |
50 | ||
51 | struct empty_helper_t2 { int i[256]; }; | |
52 | ||
53 | #if !BOOST_WORKAROUND(__BORLANDC__, < 0x600) | |
54 | ||
55 | template <typename T, bool is_a_class = false> | |
56 | struct empty_helper | |
57 | { | |
58 | BOOST_STATIC_CONSTANT(bool, value = false); | |
59 | }; | |
60 | ||
61 | template <typename T> | |
62 | struct empty_helper<T, true> | |
63 | { | |
64 | BOOST_STATIC_CONSTANT( | |
65 | bool, value = (sizeof(empty_helper_t1<T>) == sizeof(empty_helper_t2)) | |
66 | ); | |
67 | }; | |
68 | ||
69 | template <typename T> | |
70 | struct is_empty_impl | |
71 | { | |
72 | typedef typename remove_cv<T>::type cvt; | |
73 | BOOST_STATIC_CONSTANT( | |
74 | bool, | |
75 | value = ( ::boost::detail::empty_helper<cvt,::boost::is_class<T>::value>::value || BOOST_INTERNAL_IS_EMPTY(cvt))); | |
76 | }; | |
77 | ||
78 | #else // __BORLANDC__ | |
79 | ||
80 | template <typename T, bool is_a_class, bool convertible_to_int> | |
81 | struct empty_helper | |
82 | { | |
83 | BOOST_STATIC_CONSTANT(bool, value = false); | |
84 | }; | |
85 | ||
86 | template <typename T> | |
87 | struct empty_helper<T, true, false> | |
88 | { | |
89 | BOOST_STATIC_CONSTANT(bool, value = ( | |
90 | sizeof(empty_helper_t1<T>) == sizeof(empty_helper_t2) | |
91 | )); | |
92 | }; | |
93 | ||
94 | template <typename T> | |
95 | struct is_empty_impl | |
96 | { | |
97 | typedef typename remove_cv<T>::type cvt; | |
98 | typedef typename add_reference<T>::type r_type; | |
99 | ||
100 | BOOST_STATIC_CONSTANT( | |
101 | bool, value = ( | |
102 | ::boost::detail::empty_helper< | |
103 | cvt | |
104 | , ::boost::is_class<T>::value | |
105 | , ::boost::is_convertible< r_type,int>::value | |
106 | >::value || BOOST_INTERNAL_IS_EMPTY(cvt)); | |
107 | }; | |
108 | ||
109 | #endif // __BORLANDC__ | |
110 | ||
111 | } // namespace detail | |
112 | ||
113 | template <class T> struct is_empty : integral_constant<bool, ::boost::detail::is_empty_impl<T>::value> {}; | |
114 | ||
115 | } // namespace boost | |
116 | ||
117 | #undef BOOST_INTERNAL_IS_EMPTY | |
118 | ||
119 | #endif // BOOST_TT_IS_EMPTY_HPP_INCLUDED | |
120 |