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1 : // Functions used by iterators -*- C++ -*-
2 :
3 : // Copyright (C) 2001-2022 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 : /*
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 : inline _GLIBCXX14_CONSTEXPR
98 : typename iterator_traits<_RandomAccessIterator>::difference_type
99 55390 : __distance(_RandomAccessIterator __first, _RandomAccessIterator __last,
100 : random_access_iterator_tag)
101 : {
102 : // concept requirements
103 : __glibcxx_function_requires(_RandomAccessIteratorConcept<
104 : _RandomAccessIterator>)
105 55390 : return __last - __first;
106 : }
107 :
108 : #if _GLIBCXX_USE_CXX11_ABI
109 : // Forward declaration because of the qualified call in distance.
110 : template<typename _Tp>
111 : ptrdiff_t
112 : __distance(_GLIBCXX_STD_C::_List_iterator<_Tp>,
113 : _GLIBCXX_STD_C::_List_iterator<_Tp>,
114 : input_iterator_tag);
115 :
116 : template<typename _Tp>
117 : ptrdiff_t
118 : __distance(_GLIBCXX_STD_C::_List_const_iterator<_Tp>,
119 : _GLIBCXX_STD_C::_List_const_iterator<_Tp>,
120 : input_iterator_tag);
121 : #endif
122 :
123 : #if __cplusplus >= 201103L
124 : // Give better error if std::distance called with a non-Cpp17InputIterator.
125 : template<typename _OutputIterator>
126 : void
127 : __distance(_OutputIterator, _OutputIterator, output_iterator_tag) = delete;
128 : #endif
129 :
130 : /**
131 : * @brief A generalization of pointer arithmetic.
132 : * @param __first An input iterator.
133 : * @param __last An input iterator.
134 : * @return The distance between them.
135 : *
136 : * Returns @c n such that __first + n == __last. This requires
137 : * that @p __last must be reachable from @p __first. Note that @c
138 : * n may be negative.
139 : *
140 : * For random access iterators, this uses their @c + and @c - operations
141 : * and are constant time. For other %iterator classes they are linear time.
142 : */
143 : template<typename _InputIterator>
144 : _GLIBCXX_NODISCARD
145 : inline _GLIBCXX17_CONSTEXPR
146 : typename iterator_traits<_InputIterator>::difference_type
147 55506 : distance(_InputIterator __first, _InputIterator __last)
148 : {
149 : // concept requirements -- taken care of in __distance
150 55506 : return std::__distance(__first, __last,
151 : std::__iterator_category(__first));
152 : }
153 :
154 : template<typename _InputIterator, typename _Distance>
155 : inline _GLIBCXX14_CONSTEXPR void
156 : __advance(_InputIterator& __i, _Distance __n, input_iterator_tag)
157 : {
158 : // concept requirements
159 : __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
160 : __glibcxx_assert(__n >= 0);
161 : while (__n--)
162 : ++__i;
163 : }
164 :
165 : template<typename _BidirectionalIterator, typename _Distance>
166 : inline _GLIBCXX14_CONSTEXPR void
167 232 : __advance(_BidirectionalIterator& __i, _Distance __n,
168 : bidirectional_iterator_tag)
169 : {
170 : // concept requirements
171 : __glibcxx_function_requires(_BidirectionalIteratorConcept<
172 : _BidirectionalIterator>)
173 232 : if (__n > 0)
174 1957 : while (__n--)
175 1957 : ++__i;
176 : else
177 1 : while (__n++)
178 1 : --__i;
179 232 : }
180 :
181 : template<typename _RandomAccessIterator, typename _Distance>
182 : inline _GLIBCXX14_CONSTEXPR void
183 : __advance(_RandomAccessIterator& __i, _Distance __n,
184 : random_access_iterator_tag)
185 : {
186 : // concept requirements
187 : __glibcxx_function_requires(_RandomAccessIteratorConcept<
188 : _RandomAccessIterator>)
189 : if (__builtin_constant_p(__n) && __n == 1)
190 : ++__i;
191 : else if (__builtin_constant_p(__n) && __n == -1)
192 : --__i;
193 : else
194 : __i += __n;
195 : }
196 :
197 : #if __cplusplus >= 201103L
198 : // Give better error if std::advance called with a non-Cpp17InputIterator.
199 : template<typename _OutputIterator, typename _Distance>
200 : void
201 : __advance(_OutputIterator&, _Distance, output_iterator_tag) = delete;
202 : #endif
203 :
204 : /**
205 : * @brief A generalization of pointer arithmetic.
206 : * @param __i An input iterator.
207 : * @param __n The @a delta by which to change @p __i.
208 : * @return Nothing.
209 : *
210 : * This increments @p i by @p n. For bidirectional and random access
211 : * iterators, @p __n may be negative, in which case @p __i is decremented.
212 : *
213 : * For random access iterators, this uses their @c + and @c - operations
214 : * and are constant time. For other %iterator classes they are linear time.
215 : */
216 : template<typename _InputIterator, typename _Distance>
217 : inline _GLIBCXX17_CONSTEXPR void
218 232 : advance(_InputIterator& __i, _Distance __n)
219 : {
220 : // concept requirements -- taken care of in __advance
221 232 : typename iterator_traits<_InputIterator>::difference_type __d = __n;
222 116 : std::__advance(__i, __d, std::__iterator_category(__i));
223 : }
224 :
225 : #if __cplusplus >= 201103L
226 :
227 : template<typename _InputIterator>
228 : _GLIBCXX_NODISCARD
229 : inline _GLIBCXX17_CONSTEXPR _InputIterator
230 116 : next(_InputIterator __x, typename
231 : iterator_traits<_InputIterator>::difference_type __n = 1)
232 : {
233 : // concept requirements
234 : __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
235 116 : std::advance(__x, __n);
236 116 : return __x;
237 : }
238 :
239 : template<typename _BidirectionalIterator>
240 : _GLIBCXX_NODISCARD
241 : inline _GLIBCXX17_CONSTEXPR _BidirectionalIterator
242 : prev(_BidirectionalIterator __x, typename
243 : iterator_traits<_BidirectionalIterator>::difference_type __n = 1)
244 : {
245 : // concept requirements
246 : __glibcxx_function_requires(_BidirectionalIteratorConcept<
247 : _BidirectionalIterator>)
248 : std::advance(__x, -__n);
249 : return __x;
250 : }
251 :
252 : #endif // C++11
253 :
254 : _GLIBCXX_END_NAMESPACE_VERSION
255 : } // namespace
256 :
257 : #endif /* _STL_ITERATOR_BASE_FUNCS_H */
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