1// Utilities used throughout the library -*- C++ -*-
2
3// Copyright (C) 2004-2024 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
43namespace 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#endif // C++14
127
128// The standard says this macro and alias template should be in <tuple> but we
129// define them here, to be available in <array>, <utility> and <ranges> too.
130// _GLIBCXX_RESOLVE_LIB_DEFECTS
131// 3378. tuple_size_v/tuple_element_t should be available when
132// tuple_size/tuple_element are
133#ifdef __glibcxx_tuple_element_t // C++ >= 14
134 template<size_t __i, typename _Tp>
135 using tuple_element_t = typename tuple_element<__i, _Tp>::type;
136#endif
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#ifdef __glibcxx_integer_sequence // C++ >= 14
159
160 /// Class template integer_sequence
161 template<typename _Tp, _Tp... _Idx>
162 struct integer_sequence
163 {
164#if __cplusplus >= 202002L
165 static_assert(is_integral_v<_Tp>);
166#endif
167 typedef _Tp value_type;
168 static constexpr size_t size() noexcept { return sizeof...(_Idx); }
169 };
170
171 /// Alias template make_integer_sequence
172 template<typename _Tp, _Tp _Num>
173 using make_integer_sequence
174#if __has_builtin(__make_integer_seq)
175 = __make_integer_seq<integer_sequence, _Tp, _Num>;
176#else
177 = integer_sequence<_Tp, __integer_pack(_Num)...>;
178#endif
179
180 /// Alias template index_sequence
181 template<size_t... _Idx>
182 using index_sequence = integer_sequence<size_t, _Idx...>;
183
184 /// Alias template make_index_sequence
185 template<size_t _Num>
186 using make_index_sequence = make_integer_sequence<size_t, _Num>;
187
188 /// Alias template index_sequence_for
189 template<typename... _Types>
190 using index_sequence_for = make_index_sequence<sizeof...(_Types)>;
191#endif // __glibcxx_integer_sequence
192
193#if __cplusplus >= 201703L
194
195 struct in_place_t {
196 explicit in_place_t() = default;
197 };
198
199 inline constexpr in_place_t in_place{};
200
201 template<typename _Tp> struct in_place_type_t
202 {
203 explicit in_place_type_t() = default;
204 };
205
206 template<typename _Tp>
207 inline constexpr in_place_type_t<_Tp> in_place_type{};
208
209 template<size_t _Idx> struct in_place_index_t
210 {
211 explicit in_place_index_t() = default;
212 };
213
214 template<size_t _Idx>
215 inline constexpr in_place_index_t<_Idx> in_place_index{};
216
217 template<typename>
218 inline constexpr bool __is_in_place_type_v = false;
219
220 template<typename _Tp>
221 inline constexpr bool __is_in_place_type_v<in_place_type_t<_Tp>> = true;
222
223 template<typename _Tp>
224 using __is_in_place_type = bool_constant<__is_in_place_type_v<_Tp>>;
225
226 template<typename>
227 inline constexpr bool __is_in_place_index_v = false;
228
229 template<size_t _Nm>
230 inline constexpr bool __is_in_place_index_v<in_place_index_t<_Nm>> = true;
231
232#endif // C++17
233
234#if _GLIBCXX_USE_BUILTIN_TRAIT(__type_pack_element)
235 template<size_t _Np, typename... _Types>
236 struct _Nth_type
237 { using type = __type_pack_element<_Np, _Types...>; };
238#else
239 template<size_t _Np, typename... _Types>
240 struct _Nth_type
241 { };
242
243 template<typename _Tp0, typename... _Rest>
244 struct _Nth_type<0, _Tp0, _Rest...>
245 { using type = _Tp0; };
246
247 template<typename _Tp0, typename _Tp1, typename... _Rest>
248 struct _Nth_type<1, _Tp0, _Tp1, _Rest...>
249 { using type = _Tp1; };
250
251 template<typename _Tp0, typename _Tp1, typename _Tp2, typename... _Rest>
252 struct _Nth_type<2, _Tp0, _Tp1, _Tp2, _Rest...>
253 { using type = _Tp2; };
254
255 template<size_t _Np, typename _Tp0, typename _Tp1, typename _Tp2,
256 typename... _Rest>
257#if __cpp_concepts
258 requires (_Np >= 3)
259#endif
260 struct _Nth_type<_Np, _Tp0, _Tp1, _Tp2, _Rest...>
261 : _Nth_type<_Np - 3, _Rest...>
262 { };
263
264#if ! __cpp_concepts // Need additional specializations to avoid ambiguities.
265 template<typename _Tp0, typename _Tp1, typename _Tp2, typename... _Rest>
266 struct _Nth_type<0, _Tp0, _Tp1, _Tp2, _Rest...>
267 { using type = _Tp0; };
268
269 template<typename _Tp0, typename _Tp1, typename _Tp2, typename... _Rest>
270 struct _Nth_type<1, _Tp0, _Tp1, _Tp2, _Rest...>
271 { using type = _Tp1; };
272#endif
273#endif
274
275#if __glibcxx_ranges
276 namespace ranges::__detail
277 {
278 template<typename _Range>
279 inline constexpr bool __is_subrange = false;
280 } // namespace __detail
281#endif
282
283_GLIBCXX_END_NAMESPACE_VERSION
284} // namespace
285
286#endif // C++11
287#endif /* _GLIBCXX_UTILITY_H */
288