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1 | // Boost.Signals library |
2 | ||
3 | // Copyright Douglas Gregor 2001-2004. Use, modification and | |
4 | // distribution is subject to the Boost Software License, Version | |
5 | // 1.0. (See accompanying file LICENSE_1_0.txt or copy at | |
6 | // http://www.boost.org/LICENSE_1_0.txt) | |
7 | ||
8 | // For more information, see http://www.boost.org | |
9 | ||
10 | #ifndef BOOST_SIGNALS_COMMON_HEADER | |
11 | #define BOOST_SIGNALS_COMMON_HEADER | |
12 | ||
13 | #ifndef BOOST_SIGNALS_NAMESPACE | |
14 | # define BOOST_SIGNALS_NAMESPACE signals | |
15 | #endif | |
16 | ||
17 | #include <boost/type_traits/conversion_traits.hpp> | |
18 | #include <boost/ref.hpp> | |
19 | #include <boost/signals/detail/config.hpp> | |
20 | ||
21 | #ifdef BOOST_HAS_ABI_HEADERS | |
22 | # include BOOST_ABI_PREFIX | |
23 | #endif | |
24 | ||
25 | namespace boost { | |
26 | namespace BOOST_SIGNALS_NAMESPACE { | |
27 | namespace detail { | |
28 | // The unusable class is a placeholder for unused function arguments | |
29 | // It is also completely unusable except that it constructable from | |
30 | // anything. This helps compilers without partial specialization | |
31 | // handle slots returning void. | |
32 | struct unusable { | |
33 | unusable() {} | |
34 | }; | |
35 | ||
36 | // Determine the result type of a slot call | |
37 | template<typename R> | |
38 | struct slot_result_type { | |
39 | typedef R type; | |
40 | }; | |
41 | ||
42 | template<> | |
43 | struct slot_result_type<void> { | |
44 | typedef unusable type; | |
45 | }; | |
46 | ||
47 | // Determine if the given type T is a signal | |
48 | class signal_base; | |
49 | ||
50 | template<typename T> | |
51 | struct is_signal { | |
52 | BOOST_STATIC_CONSTANT(bool, | |
53 | value = (is_convertible<T*, signal_base*>::value)); | |
54 | }; | |
55 | ||
56 | /* | |
57 | * The IF implementation is temporary code. When a Boost metaprogramming | |
58 | * library is introduced, Boost.Signals will use it instead. | |
59 | */ | |
60 | namespace intimate { | |
61 | struct SelectThen | |
62 | { | |
63 | template<typename Then, typename Else> | |
64 | struct Result | |
65 | { | |
66 | typedef Then type; | |
67 | }; | |
68 | }; | |
69 | ||
70 | struct SelectElse | |
71 | { | |
72 | template<typename Then, typename Else> | |
73 | struct Result | |
74 | { | |
75 | typedef Else type; | |
76 | }; | |
77 | }; | |
78 | ||
79 | template<bool Condition> | |
80 | struct Selector | |
81 | { | |
82 | typedef SelectThen type; | |
83 | }; | |
84 | ||
85 | template<> | |
86 | struct Selector<false> | |
87 | { | |
88 | typedef SelectElse type; | |
89 | }; | |
90 | } // end namespace intimate | |
91 | ||
92 | template<bool Condition, typename Then, typename Else> | |
93 | struct IF | |
94 | { | |
95 | typedef typename intimate::Selector<Condition>::type select; | |
96 | typedef typename select::template Result<Then,Else>::type type; | |
97 | }; | |
98 | ||
99 | // Determine if the incoming argument is a reference_wrapper | |
100 | template<typename T> | |
101 | struct is_ref | |
102 | { | |
103 | BOOST_STATIC_CONSTANT(bool, value = false); | |
104 | }; | |
105 | ||
106 | template<typename T> | |
107 | struct is_ref<reference_wrapper<T> > | |
108 | { | |
109 | BOOST_STATIC_CONSTANT(bool, value = true); | |
110 | }; | |
111 | ||
112 | // A slot can be a signal, a reference to a function object, or a | |
113 | // function object. | |
114 | struct signal_tag {}; | |
115 | struct reference_tag {}; | |
116 | struct value_tag {}; | |
117 | ||
118 | // Classify the given slot as a signal, a reference-to-slot, or a | |
119 | // standard slot | |
120 | template<typename S> | |
121 | class get_slot_tag { | |
122 | typedef typename IF<(is_signal<S>::value), | |
123 | signal_tag, | |
124 | value_tag>::type signal_or_value; | |
125 | ||
126 | public: | |
127 | typedef typename IF<(is_ref<S>::value), | |
128 | reference_tag, | |
129 | signal_or_value>::type type; | |
130 | }; | |
131 | ||
132 | // Forward declaration needed in lots of places | |
133 | class signal_base_impl; | |
134 | class bound_objects_visitor; | |
135 | class slot_base; | |
136 | } // end namespace detail | |
137 | } // end namespace BOOST_SIGNALS_NAMESPACE | |
138 | } // end namespace boost | |
139 | ||
140 | #ifdef BOOST_HAS_ABI_HEADERS | |
141 | # include BOOST_ABI_SUFFIX | |
142 | #endif | |
143 | ||
144 | #endif // BOOST_SIGNALS_COMMON_HEADER |