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1 : // Types used in iterator implementation -*- C++ -*-
2 :
3 : // Copyright (C) 2001-2024 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 : /*
26 : *
27 : * Copyright (c) 1994
28 : * Hewlett-Packard Company
29 : *
30 : * Permission to use, copy, modify, distribute and sell this software
31 : * and its documentation for any purpose is hereby granted without fee,
32 : * provided that the above copyright notice appear in all copies and
33 : * that both that copyright notice and this permission notice appear
34 : * in supporting documentation. Hewlett-Packard Company makes no
35 : * representations about the suitability of this software for any
36 : * purpose. It is provided "as is" without express or implied warranty.
37 : *
38 : *
39 : * Copyright (c) 1996-1998
40 : * Silicon Graphics Computer Systems, Inc.
41 : *
42 : * Permission to use, copy, modify, distribute and sell this software
43 : * and its documentation for any purpose is hereby granted without fee,
44 : * provided that the above copyright notice appear in all copies and
45 : * that both that copyright notice and this permission notice appear
46 : * in supporting documentation. Silicon Graphics makes no
47 : * representations about the suitability of this software for any
48 : * purpose. It is provided "as is" without express or implied warranty.
49 : */
50 :
51 : /** @file bits/stl_iterator_base_types.h
52 : * This is an internal header file, included by other library headers.
53 : * Do not attempt to use it directly. @headername{iterator}
54 : *
55 : * This file contains all of the general iterator-related utility types,
56 : * such as iterator_traits and struct iterator.
57 : */
58 :
59 : #ifndef _STL_ITERATOR_BASE_TYPES_H
60 : #define _STL_ITERATOR_BASE_TYPES_H 1
61 :
62 : #pragma GCC system_header
63 :
64 : #include <bits/c++config.h>
65 :
66 : #if __cplusplus >= 201103L
67 : # include <type_traits> // For __void_t, is_convertible
68 : #endif
69 :
70 : #if __cplusplus > 201703L && __cpp_concepts >= 201907L
71 : # include <bits/iterator_concepts.h>
72 : #endif
73 :
74 : namespace std _GLIBCXX_VISIBILITY(default)
75 : {
76 : _GLIBCXX_BEGIN_NAMESPACE_VERSION
77 :
78 : /**
79 : * @defgroup iterators Iterators
80 : * Abstractions for uniform iterating through various underlying types.
81 : */
82 : ///@{
83 :
84 : /**
85 : * @defgroup iterator_tags Iterator Tags
86 : * These are empty types, used to distinguish different iterators. The
87 : * distinction is not made by what they contain, but simply by what they
88 : * are. Different underlying algorithms can then be used based on the
89 : * different operations supported by different iterator types.
90 : */
91 : ///@{
92 : /// Marking input iterators.
93 : struct input_iterator_tag { };
94 :
95 : /// Marking output iterators.
96 : struct output_iterator_tag { };
97 :
98 : /// Forward iterators support a superset of input iterator operations.
99 : struct forward_iterator_tag : public input_iterator_tag { };
100 :
101 : /// Bidirectional iterators support a superset of forward iterator
102 : /// operations.
103 : struct bidirectional_iterator_tag : public forward_iterator_tag { };
104 :
105 : /// Random-access iterators support a superset of bidirectional
106 : /// iterator operations.
107 : struct random_access_iterator_tag : public bidirectional_iterator_tag { };
108 :
109 : #if __cplusplus > 201703L
110 : /// Contiguous iterators point to objects stored contiguously in memory.
111 : struct contiguous_iterator_tag : public random_access_iterator_tag { };
112 : #endif
113 : ///@}
114 :
115 : /**
116 : * @brief Common %iterator class.
117 : *
118 : * This class does nothing but define nested typedefs. %Iterator classes
119 : * can inherit from this class to save some work. The typedefs are then
120 : * used in specializations and overloading.
121 : *
122 : * In particular, there are no default implementations of requirements
123 : * such as @c operator++ and the like. (How could there be?)
124 : */
125 : template<typename _Category, typename _Tp, typename _Distance = ptrdiff_t,
126 : typename _Pointer = _Tp*, typename _Reference = _Tp&>
127 : struct _GLIBCXX17_DEPRECATED iterator
128 : {
129 : /// One of the @link iterator_tags tag types@endlink.
130 : typedef _Category iterator_category;
131 : /// The type "pointed to" by the iterator.
132 : typedef _Tp value_type;
133 : /// Distance between iterators is represented as this type.
134 : typedef _Distance difference_type;
135 : /// This type represents a pointer-to-value_type.
136 : typedef _Pointer pointer;
137 : /// This type represents a reference-to-value_type.
138 : typedef _Reference reference;
139 : };
140 :
141 : /**
142 : * @brief Traits class for iterators.
143 : *
144 : * This class does nothing but define nested typedefs. The general
145 : * version simply @a forwards the nested typedefs from the Iterator
146 : * argument. Specialized versions for pointers and pointers-to-const
147 : * provide tighter, more correct semantics.
148 : */
149 : template<typename _Iterator>
150 : struct iterator_traits;
151 :
152 : #if __cplusplus >= 201103L
153 : // _GLIBCXX_RESOLVE_LIB_DEFECTS
154 : // 2408. SFINAE-friendly common_type/iterator_traits is missing in C++14
155 : template<typename _Iterator, typename = __void_t<>>
156 : struct __iterator_traits { };
157 :
158 : #if ! __cpp_lib_concepts
159 :
160 : template<typename _Iterator>
161 : struct __iterator_traits<_Iterator,
162 : __void_t<typename _Iterator::iterator_category,
163 : typename _Iterator::value_type,
164 : typename _Iterator::difference_type,
165 : typename _Iterator::pointer,
166 : typename _Iterator::reference>>
167 : {
168 : typedef typename _Iterator::iterator_category iterator_category;
169 : typedef typename _Iterator::value_type value_type;
170 : typedef typename _Iterator::difference_type difference_type;
171 : typedef typename _Iterator::pointer pointer;
172 : typedef typename _Iterator::reference reference;
173 : };
174 : #endif // ! concepts
175 :
176 : template<typename _Iterator>
177 : struct iterator_traits
178 : : public __iterator_traits<_Iterator> { };
179 :
180 : #else // ! C++11
181 : template<typename _Iterator>
182 : struct iterator_traits
183 : {
184 : typedef typename _Iterator::iterator_category iterator_category;
185 : typedef typename _Iterator::value_type value_type;
186 : typedef typename _Iterator::difference_type difference_type;
187 : typedef typename _Iterator::pointer pointer;
188 : typedef typename _Iterator::reference reference;
189 : };
190 : #endif // C++11
191 :
192 : #if __cplusplus > 201703L
193 : /// Partial specialization for object pointer types.
194 : template<typename _Tp>
195 : #if __cpp_concepts >= 201907L
196 : requires is_object_v<_Tp>
197 : #endif
198 : struct iterator_traits<_Tp*>
199 : {
200 : using iterator_concept = contiguous_iterator_tag;
201 : using iterator_category = random_access_iterator_tag;
202 : using value_type = remove_cv_t<_Tp>;
203 : using difference_type = ptrdiff_t;
204 : using pointer = _Tp*;
205 : using reference = _Tp&;
206 : };
207 : #else
208 : /// Partial specialization for pointer types.
209 : template<typename _Tp>
210 : struct iterator_traits<_Tp*>
211 : {
212 : typedef random_access_iterator_tag iterator_category;
213 : typedef _Tp value_type;
214 : typedef ptrdiff_t difference_type;
215 : typedef _Tp* pointer;
216 : typedef _Tp& reference;
217 : };
218 :
219 : /// Partial specialization for const pointer types.
220 : template<typename _Tp>
221 : struct iterator_traits<const _Tp*>
222 : {
223 : typedef random_access_iterator_tag iterator_category;
224 : typedef _Tp value_type;
225 : typedef ptrdiff_t difference_type;
226 : typedef const _Tp* pointer;
227 : typedef const _Tp& reference;
228 : };
229 : #endif
230 :
231 : /**
232 : * This function is not a part of the C++ standard but is syntactic
233 : * sugar for internal library use only.
234 : */
235 : template<typename _Iter>
236 : __attribute__((__always_inline__))
237 : inline _GLIBCXX_CONSTEXPR
238 : typename iterator_traits<_Iter>::iterator_category
239 : __iterator_category(const _Iter&)
240 0 : { return typename iterator_traits<_Iter>::iterator_category(); }
241 :
242 : ///@}
243 :
244 : #if __cplusplus >= 201103L
245 : template<typename _Iter>
246 : using __iter_category_t
247 : = typename iterator_traits<_Iter>::iterator_category;
248 :
249 : template<typename _InIter>
250 : using _RequireInputIter =
251 : __enable_if_t<is_convertible<__iter_category_t<_InIter>,
252 : input_iterator_tag>::value>;
253 :
254 : template<typename _It,
255 : typename _Cat = __iter_category_t<_It>>
256 : struct __is_random_access_iter
257 : : is_base_of<random_access_iterator_tag, _Cat>
258 : {
259 : typedef is_base_of<random_access_iterator_tag, _Cat> _Base;
260 : enum { __value = _Base::value };
261 : };
262 : #else
263 : template<typename _It, typename _Traits = iterator_traits<_It>,
264 : typename _Cat = typename _Traits::iterator_category>
265 : struct __is_random_access_iter
266 : { enum { __value = __is_base_of(random_access_iterator_tag, _Cat) }; };
267 : #endif
268 :
269 : _GLIBCXX_END_NAMESPACE_VERSION
270 : } // namespace
271 :
272 : #endif /* _STL_ITERATOR_BASE_TYPES_H */
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