1 // Utilities used throughout the library -*- C++ -*-
2
3 // Copyright (C) 2004-2023 Free Software Foundation, Inc.
4 //
5 // This file is part of the GNU ISO C++ Library. This library is free
6 // software; you can redistribute it and/or modify it under the
7 // terms of the GNU General Public License as published by the
8 // Free Software Foundation; either version 3, or (at your option)
9 // any later version.
10
11 // This library is distributed in the hope that it will be useful,
12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 // GNU General Public License for more details.
15
16 // Under Section 7 of GPL version 3, you are granted additional
17 // permissions described in the GCC Runtime Library Exception, version
18 // 3.1, as published by the Free Software Foundation.
19
20 // You should have received a copy of the GNU General Public License and
21 // a copy of the GCC Runtime Library Exception along with this program;
22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23 // <http://www.gnu.org/licenses/>.
24
25 /** @file include/bits/utility.h
26 * This is an internal header file, included by other library headers.
27 * Do not attempt to use it directly. @headername{utility}
28 *
29 * This file contains the parts of `<utility>` needed by other headers,
30 * so they don't need to include the whole of `<utility>`.
31 */
32
33 #ifndef _GLIBCXX_UTILITY_H
34 #define _GLIBCXX_UTILITY_H 1
35
36 #pragma GCC system_header
37
38 #if __cplusplus >= 201103L
39
40 #include <type_traits>
41 #include <bits/move.h>
42
43 namespace std _GLIBCXX_VISIBILITY(default)
44 {
45 _GLIBCXX_BEGIN_NAMESPACE_VERSION
46
47 /// Finds the size of a given tuple type.
48 template<typename _Tp>
49 struct tuple_size;
50
51 // _GLIBCXX_RESOLVE_LIB_DEFECTS
52 // 2313. tuple_size should always derive from integral_constant<size_t, N>
53 // 2770. tuple_size<const T> specialization is not SFINAE compatible
54
55 template<typename _Tp,
56 typename _Up = typename remove_cv<_Tp>::type,
57 typename = typename enable_if<is_same<_Tp, _Up>::value>::type,
58 size_t = tuple_size<_Tp>::value>
59 using __enable_if_has_tuple_size = _Tp;
60
61 template<typename _Tp>
62 struct tuple_size<const __enable_if_has_tuple_size<_Tp>>
63 : public tuple_size<_Tp> { };
64
65 template<typename _Tp>
66 struct tuple_size<volatile __enable_if_has_tuple_size<_Tp>>
67 : public tuple_size<_Tp> { };
68
69 template<typename _Tp>
70 struct tuple_size<const volatile __enable_if_has_tuple_size<_Tp>>
71 : public tuple_size<_Tp> { };
72
73 #if __cplusplus >= 201703L
74 template<typename _Tp>
75 inline constexpr size_t tuple_size_v = tuple_size<_Tp>::value;
76 #endif
77
78 /// Gives the type of the ith element of a given tuple type.
79 template<size_t __i, typename _Tp>
80 struct tuple_element;
81
82 // Duplicate of C++14's tuple_element_t for internal use in C++11 mode
83 template<size_t __i, typename _Tp>
84 using __tuple_element_t = typename tuple_element<__i, _Tp>::type;
85
86 template<size_t __i, typename _Tp>
87 struct tuple_element<__i, const _Tp>
88 {
89 using type = const __tuple_element_t<__i, _Tp>;
90 };
91
92 template<size_t __i, typename _Tp>
93 struct tuple_element<__i, volatile _Tp>
94 {
95 using type = volatile __tuple_element_t<__i, _Tp>;
96 };
97
98 template<size_t __i, typename _Tp>
99 struct tuple_element<__i, const volatile _Tp>
100 {
101 using type = const volatile __tuple_element_t<__i, _Tp>;
102 };
103
104 #if __cplusplus >= 201402L
105
106 // Return the index of _Tp in _Types, if it occurs exactly once.
107 // Otherwise, return sizeof...(_Types).
108 template<typename _Tp, typename... _Types>
109 constexpr size_t
110 __find_uniq_type_in_pack()
111 {
112 constexpr size_t __sz = sizeof...(_Types);
113 constexpr bool __found[__sz] = { __is_same(_Tp, _Types) ... };
114 size_t __n = __sz;
115 for (size_t __i = 0; __i < __sz; ++__i)
116 {
117 if (__found[__i])
118 {
119 if (__n < __sz) // more than one _Tp found
120 return __sz;
121 __n = __i;
122 }
123 }
124 return __n;
125 }
126
127 // The standard says this macro and alias template should be in <tuple> but we
128 // define them here, to be available in <array>, <utility> and <ranges> too.
129 // _GLIBCXX_RESOLVE_LIB_DEFECTS
130 // 3378. tuple_size_v/tuple_element_t should be available when
131 // tuple_size/tuple_element are
132 #define __cpp_lib_tuple_element_t 201402L
133
134 template<size_t __i, typename _Tp>
135 using tuple_element_t = typename tuple_element<__i, _Tp>::type;
136 #endif // C++14
137
138 // Stores a tuple of indices. Used by tuple and pair, and by bind() to
139 // extract the elements in a tuple.
140 template<size_t... _Indexes> struct _Index_tuple { };
141
142 // Builds an _Index_tuple<0, 1, 2, ..., _Num-1>.
143 template<size_t _Num>
144 struct _Build_index_tuple
145 {
146 #if __has_builtin(__make_integer_seq)
147 template<typename, size_t... _Indices>
148 using _IdxTuple = _Index_tuple<_Indices...>;
149
150 // Clang defines __make_integer_seq for this purpose.
151 using __type = __make_integer_seq<_IdxTuple, size_t, _Num>;
152 #else
153 // For GCC and other compilers, use __integer_pack instead.
154 using __type = _Index_tuple<__integer_pack(_Num)...>;
155 #endif
156 };
157
158 #if __cplusplus >= 201402L
159
160 #define __cpp_lib_integer_sequence 201304L
161
162 /// Class template integer_sequence
163 template<typename _Tp, _Tp... _Idx>
164 struct integer_sequence
165 {
166 typedef _Tp value_type;
167 static constexpr size_t size() noexcept { return sizeof...(_Idx); }
168 };
169
170 /// Alias template make_integer_sequence
171 template<typename _Tp, _Tp _Num>
172 using make_integer_sequence
173 #if __has_builtin(__make_integer_seq)
174 = __make_integer_seq<integer_sequence, _Tp, _Num>;
175 #else
176 = integer_sequence<_Tp, __integer_pack(_Num)...>;
177 #endif
178
179 /// Alias template index_sequence
180 template<size_t... _Idx>
181 using index_sequence = integer_sequence<size_t, _Idx...>;
182
183 /// Alias template make_index_sequence
184 template<size_t _Num>
185 using make_index_sequence = make_integer_sequence<size_t, _Num>;
186
187 /// Alias template index_sequence_for
188 template<typename... _Types>
189 using index_sequence_for = make_index_sequence<sizeof...(_Types)>;
190
191 #if __cplusplus >= 201703L
192
193 struct in_place_t {
194 explicit in_place_t() = default;
195 };
196
197 inline constexpr in_place_t in_place{};
198
199 template<typename _Tp> struct in_place_type_t
200 {
201 explicit in_place_type_t() = default;
202 };
203
204 template<typename _Tp>
205 inline constexpr in_place_type_t<_Tp> in_place_type{};
206
207 template<size_t _Idx> struct in_place_index_t
208 {
209 explicit in_place_index_t() = default;
210 };
211
212 template<size_t _Idx>
213 inline constexpr in_place_index_t<_Idx> in_place_index{};
214
215 template<typename>
216 inline constexpr bool __is_in_place_type_v = false;
217
218 template<typename _Tp>
219 inline constexpr bool __is_in_place_type_v<in_place_type_t<_Tp>> = true;
220
221 template<typename _Tp>
222 using __is_in_place_type = bool_constant<__is_in_place_type_v<_Tp>>;
223
224 #endif // C++17
225 #endif // C++14
226
227 template<size_t _Np, typename... _Types>
228 struct _Nth_type
229 { };
230
231 template<typename _Tp0, typename... _Rest>
232 struct _Nth_type<0, _Tp0, _Rest...>
233 { using type = _Tp0; };
234
235 template<typename _Tp0, typename _Tp1, typename... _Rest>
236 struct _Nth_type<1, _Tp0, _Tp1, _Rest...>
237 { using type = _Tp1; };
238
239 template<typename _Tp0, typename _Tp1, typename _Tp2, typename... _Rest>
240 struct _Nth_type<2, _Tp0, _Tp1, _Tp2, _Rest...>
241 { using type = _Tp2; };
242
243 template<size_t _Np, typename _Tp0, typename _Tp1, typename _Tp2,
244 typename... _Rest>
245 #if __cpp_concepts
246 requires (_Np >= 3)
247 #endif
248 struct _Nth_type<_Np, _Tp0, _Tp1, _Tp2, _Rest...>
249 : _Nth_type<_Np - 3, _Rest...>
250 { };
251
252 #if ! __cpp_concepts // Need additional specializations to avoid ambiguities.
253 template<typename _Tp0, typename _Tp1, typename... _Rest>
254 struct _Nth_type<0, _Tp0, _Tp1, _Rest...>
255 { using type = _Tp0; };
256
257 template<typename _Tp0, typename _Tp1, typename _Tp2, typename... _Rest>
258 struct _Nth_type<0, _Tp0, _Tp1, _Tp2, _Rest...>
259 { using type = _Tp0; };
260
261 template<typename _Tp0, typename _Tp1, typename _Tp2, typename... _Rest>
262 struct _Nth_type<1, _Tp0, _Tp1, _Tp2, _Rest...>
263 { using type = _Tp1; };
264 #endif
265
266 #if __cplusplus > 202002L
267 #define __cpp_lib_ranges_zip 202110L // for <tuple> and <utility>
268 #endif
269
270 _GLIBCXX_END_NAMESPACE_VERSION
271 } // namespace
272
273 #endif // C++11
274 #endif /* _GLIBCXX_UTILITY_H */