1// Utilities used throughout the library -*- C++ -*-
2
3// Copyright (C) 2004-2022 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      typedef typename add_const<__tuple_element_t<__i, _Tp>>::type type;
90    };
91
92  template<size_t __i, typename _Tp>
93    struct tuple_element<__i, volatile _Tp>
94    {
95      typedef typename add_volatile<__tuple_element_t<__i, _Tp>>::type type;
96    };
97
98  template<size_t __i, typename _Tp>
99    struct tuple_element<__i, const volatile _Tp>
100    {
101      typedef typename add_cv<__tuple_element_t<__i, _Tp>>::type type;
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_GLIBCXX_END_NAMESPACE_VERSION
267} // namespace
268
269#endif // C++11
270#endif /* _GLIBCXX_UTILITY_H */
271