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1 : // Functions used by iterators -*- 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_funcs.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
56 : * functions, such as distance() and advance().
57 : */
58 :
59 : #ifndef _STL_ITERATOR_BASE_FUNCS_H
60 : #define _STL_ITERATOR_BASE_FUNCS_H 1
61 :
62 : #pragma GCC system_header
63 :
64 : #include <bits/concept_check.h>
65 : #include <debug/assertions.h>
66 : #include <bits/stl_iterator_base_types.h>
67 :
68 : namespace std _GLIBCXX_VISIBILITY(default)
69 : {
70 : _GLIBCXX_BEGIN_NAMESPACE_VERSION
71 :
72 : _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
73 : // Forward declaration for the overloads of __distance.
74 : template <typename> struct _List_iterator;
75 : template <typename> struct _List_const_iterator;
76 : _GLIBCXX_END_NAMESPACE_CONTAINER
77 :
78 : template<typename _InputIterator>
79 : inline _GLIBCXX14_CONSTEXPR
80 : typename iterator_traits<_InputIterator>::difference_type
81 : __distance(_InputIterator __first, _InputIterator __last,
82 : input_iterator_tag)
83 : {
84 : // concept requirements
85 : __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
86 :
87 : typename iterator_traits<_InputIterator>::difference_type __n = 0;
88 : while (__first != __last)
89 : {
90 : ++__first;
91 : ++__n;
92 : }
93 : return __n;
94 : }
95 :
96 : template<typename _RandomAccessIterator>
97 : __attribute__((__always_inline__))
98 : inline _GLIBCXX14_CONSTEXPR
99 : typename iterator_traits<_RandomAccessIterator>::difference_type
100 : __distance(_RandomAccessIterator __first, _RandomAccessIterator __last,
101 : random_access_iterator_tag)
102 : {
103 : // concept requirements
104 : __glibcxx_function_requires(_RandomAccessIteratorConcept<
105 : _RandomAccessIterator>)
106 0 : return __last - __first;
107 : }
108 :
109 : #if _GLIBCXX_USE_CXX11_ABI
110 : // Forward declaration because of the qualified call in distance.
111 : template<typename _Tp>
112 : ptrdiff_t
113 : __distance(_GLIBCXX_STD_C::_List_iterator<_Tp>,
114 : _GLIBCXX_STD_C::_List_iterator<_Tp>,
115 : input_iterator_tag);
116 :
117 : template<typename _Tp>
118 : ptrdiff_t
119 : __distance(_GLIBCXX_STD_C::_List_const_iterator<_Tp>,
120 : _GLIBCXX_STD_C::_List_const_iterator<_Tp>,
121 : input_iterator_tag);
122 : #endif
123 :
124 : #if __cplusplus >= 201103L
125 : // Give better error if std::distance called with a non-Cpp17InputIterator.
126 : template<typename _OutputIterator>
127 : void
128 : __distance(_OutputIterator, _OutputIterator, output_iterator_tag) = delete;
129 : #endif
130 :
131 : /**
132 : * @brief A generalization of pointer arithmetic.
133 : * @param __first An input iterator.
134 : * @param __last An input iterator.
135 : * @return The distance between them.
136 : *
137 : * Returns @c n such that __first + n == __last. This requires
138 : * that @p __last must be reachable from @p __first. Note that @c
139 : * n may be negative.
140 : *
141 : * For random access iterators, this uses their @c + and @c - operations
142 : * and are constant time. For other %iterator classes they are linear time.
143 : */
144 : template<typename _InputIterator>
145 : _GLIBCXX_NODISCARD __attribute__((__always_inline__))
146 : inline _GLIBCXX17_CONSTEXPR
147 : typename iterator_traits<_InputIterator>::difference_type
148 : distance(_InputIterator __first, _InputIterator __last)
149 : {
150 : // concept requirements -- taken care of in __distance
151 0 : return std::__distance(__first, __last,
152 0 : std::__iterator_category(__first));
153 : }
154 :
155 : template<typename _InputIterator, typename _Distance>
156 : inline _GLIBCXX14_CONSTEXPR void
157 : __advance(_InputIterator& __i, _Distance __n, input_iterator_tag)
158 : {
159 : // concept requirements
160 : __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
161 : __glibcxx_assert(__n >= 0);
162 : while (__n--)
163 : ++__i;
164 : }
165 :
166 : template<typename _BidirectionalIterator, typename _Distance>
167 : inline _GLIBCXX14_CONSTEXPR void
168 : __advance(_BidirectionalIterator& __i, _Distance __n,
169 : bidirectional_iterator_tag)
170 : {
171 : // concept requirements
172 : __glibcxx_function_requires(_BidirectionalIteratorConcept<
173 : _BidirectionalIterator>)
174 : if (__n > 0)
175 : while (__n--)
176 : ++__i;
177 : else
178 : while (__n++)
179 : --__i;
180 : }
181 :
182 : template<typename _RandomAccessIterator, typename _Distance>
183 : inline _GLIBCXX14_CONSTEXPR void
184 : __advance(_RandomAccessIterator& __i, _Distance __n,
185 : random_access_iterator_tag)
186 : {
187 : // concept requirements
188 : __glibcxx_function_requires(_RandomAccessIteratorConcept<
189 : _RandomAccessIterator>)
190 : if (__builtin_constant_p(__n) && __n == 1)
191 : ++__i;
192 : else if (__builtin_constant_p(__n) && __n == -1)
193 : --__i;
194 : else
195 : __i += __n;
196 : }
197 :
198 : #if __cplusplus >= 201103L
199 : // Give better error if std::advance called with a non-Cpp17InputIterator.
200 : template<typename _OutputIterator, typename _Distance>
201 : void
202 : __advance(_OutputIterator&, _Distance, output_iterator_tag) = delete;
203 : #endif
204 :
205 : /**
206 : * @brief A generalization of pointer arithmetic.
207 : * @param __i An input iterator.
208 : * @param __n The @a delta by which to change @p __i.
209 : * @return Nothing.
210 : *
211 : * This increments @p i by @p n. For bidirectional and random access
212 : * iterators, @p __n may be negative, in which case @p __i is decremented.
213 : *
214 : * For random access iterators, this uses their @c + and @c - operations
215 : * and are constant time. For other %iterator classes they are linear time.
216 : */
217 : template<typename _InputIterator, typename _Distance>
218 : __attribute__((__always_inline__))
219 : inline _GLIBCXX17_CONSTEXPR void
220 : advance(_InputIterator& __i, _Distance __n)
221 : {
222 : // concept requirements -- taken care of in __advance
223 : typename iterator_traits<_InputIterator>::difference_type __d = __n;
224 : std::__advance(__i, __d, std::__iterator_category(__i));
225 : }
226 :
227 : #if __cplusplus >= 201103L
228 :
229 : template<typename _InputIterator>
230 : _GLIBCXX_NODISCARD [[__gnu__::__always_inline__]]
231 : inline _GLIBCXX17_CONSTEXPR _InputIterator
232 : next(_InputIterator __x, typename
233 : iterator_traits<_InputIterator>::difference_type __n = 1)
234 : {
235 : // concept requirements
236 : __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
237 : std::advance(__x, __n);
238 : return __x;
239 : }
240 :
241 : template<typename _BidirectionalIterator>
242 : _GLIBCXX_NODISCARD [[__gnu__::__always_inline__]]
243 : inline _GLIBCXX17_CONSTEXPR _BidirectionalIterator
244 : prev(_BidirectionalIterator __x, typename
245 : iterator_traits<_BidirectionalIterator>::difference_type __n = 1)
246 : {
247 : // concept requirements
248 : __glibcxx_function_requires(_BidirectionalIteratorConcept<
249 : _BidirectionalIterator>)
250 : std::advance(__x, -__n);
251 : return __x;
252 : }
253 :
254 : #endif // C++11
255 :
256 : _GLIBCXX_END_NAMESPACE_VERSION
257 : } // namespace
258 :
259 : #endif /* _STL_ITERATOR_BASE_FUNCS_H */
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