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1 | // |
2 | // require_concept.hpp | |
3 | // ~~~~~~~~~~~~~~~~~~~ | |
4 | // | |
5 | // Copyright (c) 2003-2020 Christopher M. Kohlhoff (chris at kohlhoff dot com) | |
6 | // | |
7 | // Distributed under the Boost Software License, Version 1.0. (See accompanying | |
8 | // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) | |
9 | // | |
10 | ||
11 | #ifndef BOOST_ASIO_REQUIRE_CONCEPT_HPP | |
12 | #define BOOST_ASIO_REQUIRE_CONCEPT_HPP | |
13 | ||
14 | #if defined(_MSC_VER) && (_MSC_VER >= 1200) | |
15 | # pragma once | |
16 | #endif // defined(_MSC_VER) && (_MSC_VER >= 1200) | |
17 | ||
18 | #include <boost/asio/detail/config.hpp> | |
19 | #include <boost/asio/detail/type_traits.hpp> | |
20 | #include <boost/asio/is_applicable_property.hpp> | |
21 | #include <boost/asio/traits/require_concept_member.hpp> | |
22 | #include <boost/asio/traits/require_concept_free.hpp> | |
23 | #include <boost/asio/traits/static_require_concept.hpp> | |
24 | ||
25 | #include <boost/asio/detail/push_options.hpp> | |
26 | ||
27 | #if defined(GENERATING_DOCUMENTATION) | |
28 | ||
29 | namespace boost { | |
30 | namespace asio { | |
31 | ||
32 | /// A customisation point that applies a concept-enforcing property to an | |
33 | /// object. | |
34 | /** | |
35 | * The name <tt>require_concept</tt> denotes a customization point object. The | |
36 | * expression <tt>boost::asio::require_concept(E, P)</tt> for some | |
37 | * subexpressions <tt>E</tt> and <tt>P</tt> (with types <tt>T = | |
38 | * decay_t<decltype(E)></tt> and <tt>Prop = decay_t<decltype(P)></tt>) is | |
39 | * expression-equivalent to: | |
40 | * | |
41 | * @li If <tt>is_applicable_property_v<T, Prop> && | |
42 | * Prop::is_requirable_concept</tt> is not a well-formed constant expression | |
43 | * with value <tt>true</tt>, <tt>boost::asio::require_concept(E, P)</tt> is | |
44 | * ill-formed. | |
45 | * | |
46 | * @li Otherwise, <tt>E</tt> if the expression <tt>Prop::template | |
47 | * static_query_v<T> == Prop::value()</tt> is a well-formed constant | |
48 | * expression with value <tt>true</tt>. | |
49 | * | |
50 | * @li Otherwise, <tt>(E).require_concept(P)</tt> if the expression | |
51 | * <tt>(E).require_concept(P)</tt> is well-formed. | |
52 | * | |
53 | * @li Otherwise, <tt>require_concept(E, P)</tt> if the expression | |
54 | * <tt>require_concept(E, P)</tt> is a valid expression with overload | |
55 | * resolution performed in a context that does not include the declaration | |
56 | * of the <tt>require_concept</tt> customization point object. | |
57 | * | |
58 | * @li Otherwise, <tt>boost::asio::require_concept(E, P)</tt> is ill-formed. | |
59 | */ | |
60 | inline constexpr unspecified require_concept = unspecified; | |
61 | ||
62 | /// A type trait that determines whether a @c require_concept expression is | |
63 | /// well-formed. | |
64 | /** | |
65 | * Class template @c can_require_concept is a trait that is derived from | |
66 | * @c true_type if the expression | |
67 | * <tt>boost::asio::require_concept(std::declval<T>(), | |
68 | * std::declval<Property>())</tt> is well formed; otherwise @c false_type. | |
69 | */ | |
70 | template <typename T, typename Property> | |
71 | struct can_require_concept : | |
72 | integral_constant<bool, automatically_determined> | |
73 | { | |
74 | }; | |
75 | ||
76 | /// A type trait that determines whether a @c require_concept expression will | |
77 | /// not throw. | |
78 | /** | |
79 | * Class template @c is_nothrow_require_concept is a trait that is derived from | |
80 | * @c true_type if the expression | |
81 | * <tt>boost::asio::require_concept(std::declval<T>(), | |
82 | * std::declval<Property>())</tt> is @c noexcept; otherwise @c false_type. | |
83 | */ | |
84 | template <typename T, typename Property> | |
85 | struct is_nothrow_require_concept : | |
86 | integral_constant<bool, automatically_determined> | |
87 | { | |
88 | }; | |
89 | ||
90 | /// A type trait that determines the result type of a @c require_concept | |
91 | /// expression. | |
92 | /** | |
93 | * Class template @c require_concept_result is a trait that determines the | |
94 | * result type of the expression | |
95 | * <tt>boost::asio::require_concept(std::declval<T>(), | |
96 | * std::declval<Property>())</tt>. | |
97 | */ | |
98 | template <typename T, typename Property> | |
99 | struct require_concept_result | |
100 | { | |
101 | /// The result of the @c require_concept expression. | |
102 | typedef automatically_determined type; | |
103 | }; | |
104 | ||
105 | } // namespace asio | |
106 | } // namespace boost | |
107 | ||
108 | #else // defined(GENERATING_DOCUMENTATION) | |
109 | ||
110 | namespace asio_require_concept_fn { | |
111 | ||
112 | using boost::asio::decay; | |
113 | using boost::asio::declval; | |
114 | using boost::asio::enable_if; | |
115 | using boost::asio::is_applicable_property; | |
116 | using boost::asio::traits::require_concept_free; | |
117 | using boost::asio::traits::require_concept_member; | |
118 | using boost::asio::traits::static_require_concept; | |
119 | ||
120 | void require_concept(); | |
121 | ||
122 | enum overload_type | |
123 | { | |
124 | identity, | |
125 | call_member, | |
126 | call_free, | |
127 | ill_formed | |
128 | }; | |
129 | ||
130 | template <typename T, typename Properties, typename = void> | |
131 | struct call_traits | |
132 | { | |
133 | BOOST_ASIO_STATIC_CONSTEXPR(overload_type, overload = ill_formed); | |
134 | BOOST_ASIO_STATIC_CONSTEXPR(bool, is_noexcept = false); | |
135 | typedef void result_type; | |
136 | }; | |
137 | ||
138 | template <typename T, typename Property> | |
139 | struct call_traits<T, void(Property), | |
140 | typename enable_if< | |
141 | ( | |
142 | is_applicable_property< | |
143 | typename decay<T>::type, | |
144 | typename decay<Property>::type | |
145 | >::value | |
146 | && | |
147 | decay<Property>::type::is_requirable_concept | |
148 | && | |
149 | static_require_concept<T, Property>::is_valid | |
150 | ) | |
151 | >::type> | |
152 | { | |
153 | BOOST_ASIO_STATIC_CONSTEXPR(overload_type, overload = identity); | |
154 | BOOST_ASIO_STATIC_CONSTEXPR(bool, is_noexcept = true); | |
155 | typedef BOOST_ASIO_MOVE_ARG(T) result_type; | |
156 | }; | |
157 | ||
158 | template <typename T, typename Property> | |
159 | struct call_traits<T, void(Property), | |
160 | typename enable_if< | |
161 | ( | |
162 | is_applicable_property< | |
163 | typename decay<T>::type, | |
164 | typename decay<Property>::type | |
165 | >::value | |
166 | && | |
167 | decay<Property>::type::is_requirable_concept | |
168 | && | |
169 | !static_require_concept<T, Property>::is_valid | |
170 | && | |
171 | require_concept_member<T, Property>::is_valid | |
172 | ) | |
173 | >::type> : | |
174 | require_concept_member<T, Property> | |
175 | { | |
176 | BOOST_ASIO_STATIC_CONSTEXPR(overload_type, overload = call_member); | |
177 | }; | |
178 | ||
179 | template <typename T, typename Property> | |
180 | struct call_traits<T, void(Property), | |
181 | typename enable_if< | |
182 | ( | |
183 | is_applicable_property< | |
184 | typename decay<T>::type, | |
185 | typename decay<Property>::type | |
186 | >::value | |
187 | && | |
188 | decay<Property>::type::is_requirable_concept | |
189 | && | |
190 | !static_require_concept<T, Property>::is_valid | |
191 | && | |
192 | !require_concept_member<T, Property>::is_valid | |
193 | && | |
194 | require_concept_free<T, Property>::is_valid | |
195 | ) | |
196 | >::type> : | |
197 | require_concept_free<T, Property> | |
198 | { | |
199 | BOOST_ASIO_STATIC_CONSTEXPR(overload_type, overload = call_free); | |
200 | }; | |
201 | ||
202 | struct impl | |
203 | { | |
204 | template <typename T, typename Property> | |
205 | BOOST_ASIO_NODISCARD BOOST_ASIO_CONSTEXPR typename enable_if< | |
206 | call_traits<T, void(Property)>::overload == identity, | |
207 | typename call_traits<T, void(Property)>::result_type | |
208 | >::type | |
209 | operator()( | |
210 | BOOST_ASIO_MOVE_ARG(T) t, | |
211 | BOOST_ASIO_MOVE_ARG(Property)) const | |
212 | BOOST_ASIO_NOEXCEPT_IF(( | |
213 | call_traits<T, void(Property)>::is_noexcept)) | |
214 | { | |
215 | return BOOST_ASIO_MOVE_CAST(T)(t); | |
216 | } | |
217 | ||
218 | template <typename T, typename Property> | |
219 | BOOST_ASIO_NODISCARD BOOST_ASIO_CONSTEXPR typename enable_if< | |
220 | call_traits<T, void(Property)>::overload == call_member, | |
221 | typename call_traits<T, void(Property)>::result_type | |
222 | >::type | |
223 | operator()( | |
224 | BOOST_ASIO_MOVE_ARG(T) t, | |
225 | BOOST_ASIO_MOVE_ARG(Property) p) const | |
226 | BOOST_ASIO_NOEXCEPT_IF(( | |
227 | call_traits<T, void(Property)>::is_noexcept)) | |
228 | { | |
229 | return BOOST_ASIO_MOVE_CAST(T)(t).require_concept( | |
230 | BOOST_ASIO_MOVE_CAST(Property)(p)); | |
231 | } | |
232 | ||
233 | template <typename T, typename Property> | |
234 | BOOST_ASIO_NODISCARD BOOST_ASIO_CONSTEXPR typename enable_if< | |
235 | call_traits<T, void(Property)>::overload == call_free, | |
236 | typename call_traits<T, void(Property)>::result_type | |
237 | >::type | |
238 | operator()( | |
239 | BOOST_ASIO_MOVE_ARG(T) t, | |
240 | BOOST_ASIO_MOVE_ARG(Property) p) const | |
241 | BOOST_ASIO_NOEXCEPT_IF(( | |
242 | call_traits<T, void(Property)>::is_noexcept)) | |
243 | { | |
244 | return require_concept( | |
245 | BOOST_ASIO_MOVE_CAST(T)(t), | |
246 | BOOST_ASIO_MOVE_CAST(Property)(p)); | |
247 | } | |
248 | }; | |
249 | ||
250 | template <typename T = impl> | |
251 | struct static_instance | |
252 | { | |
253 | static const T instance; | |
254 | }; | |
255 | ||
256 | template <typename T> | |
257 | const T static_instance<T>::instance = {}; | |
258 | ||
259 | } // namespace asio_require_concept_fn | |
260 | namespace boost { | |
261 | namespace asio { | |
262 | namespace { | |
263 | ||
264 | static BOOST_ASIO_CONSTEXPR const asio_require_concept_fn::impl& | |
265 | require_concept = asio_require_concept_fn::static_instance<>::instance; | |
266 | ||
267 | } // namespace | |
268 | ||
269 | template <typename T, typename Property> | |
270 | struct can_require_concept : | |
271 | integral_constant<bool, | |
272 | asio_require_concept_fn::call_traits<T, void(Property)>::overload != | |
273 | asio_require_concept_fn::ill_formed> | |
274 | { | |
275 | }; | |
276 | ||
277 | #if defined(BOOST_ASIO_HAS_VARIABLE_TEMPLATES) | |
278 | ||
279 | template <typename T, typename Property> | |
280 | constexpr bool can_require_concept_v | |
281 | = can_require_concept<T, Property>::value; | |
282 | ||
283 | #endif // defined(BOOST_ASIO_HAS_VARIABLE_TEMPLATES) | |
284 | ||
285 | template <typename T, typename Property> | |
286 | struct is_nothrow_require_concept : | |
287 | integral_constant<bool, | |
288 | asio_require_concept_fn::call_traits<T, void(Property)>::is_noexcept> | |
289 | { | |
290 | }; | |
291 | ||
292 | #if defined(BOOST_ASIO_HAS_VARIABLE_TEMPLATES) | |
293 | ||
294 | template <typename T, typename Property> | |
295 | constexpr bool is_nothrow_require_concept_v | |
296 | = is_nothrow_require_concept<T, Property>::value; | |
297 | ||
298 | #endif // defined(BOOST_ASIO_HAS_VARIABLE_TEMPLATES) | |
299 | ||
300 | template <typename T, typename Property> | |
301 | struct require_concept_result | |
302 | { | |
303 | typedef typename asio_require_concept_fn::call_traits< | |
304 | T, void(Property)>::result_type type; | |
305 | }; | |
306 | ||
307 | } // namespace asio | |
308 | } // namespace boost | |
309 | ||
310 | #endif // defined(GENERATING_DOCUMENTATION) | |
311 | ||
312 | #include <boost/asio/detail/pop_options.hpp> | |
313 | ||
314 | #endif // BOOST_ASIO_REQUIRE_CONCEPT_HPP |