1// Functions used by iterators -*- C++ -*-
2
3// Copyright (C) 2001-2018 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
67namespace std _GLIBCXX_VISIBILITY(default)
68{
69_GLIBCXX_BEGIN_NAMESPACE_VERSION
70
71_GLIBCXX_BEGIN_NAMESPACE_CONTAINER
72 // Forward declaration for the overloads of __distance.
73 template <typename> struct _List_iterator;
74 template <typename> struct _List_const_iterator;
75_GLIBCXX_END_NAMESPACE_CONTAINER
76
77 template<typename _InputIterator>
78 inline _GLIBCXX14_CONSTEXPR
79 typename iterator_traits<_InputIterator>::difference_type
80 __distance(_InputIterator __first, _InputIterator __last,
81 input_iterator_tag)
82 {
83 // concept requirements
84 __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
85
86 typename iterator_traits<_InputIterator>::difference_type __n = 0;
87 while (__first != __last)
88 {
89 ++__first;
90 ++__n;
91 }
92 return __n;
93 }
94
95 template<typename _RandomAccessIterator>
96 inline _GLIBCXX14_CONSTEXPR
97 typename iterator_traits<_RandomAccessIterator>::difference_type
98 __distance(_RandomAccessIterator __first, _RandomAccessIterator __last,
99 random_access_iterator_tag)
100 {
101 // concept requirements
102 __glibcxx_function_requires(_RandomAccessIteratorConcept<
103 _RandomAccessIterator>)
104 return __last - __first;
105 }
106
107#if _GLIBCXX_USE_CXX11_ABI
108 // Forward declaration because of the qualified call in distance.
109 template<typename _Tp>
110 ptrdiff_t
111 __distance(_GLIBCXX_STD_C::_List_iterator<_Tp>,
112 _GLIBCXX_STD_C::_List_iterator<_Tp>,
113 input_iterator_tag);
114
115 template<typename _Tp>
116 ptrdiff_t
117 __distance(_GLIBCXX_STD_C::_List_const_iterator<_Tp>,
118 _GLIBCXX_STD_C::_List_const_iterator<_Tp>,
119 input_iterator_tag);
120#endif
121
122 /**
123 * @brief A generalization of pointer arithmetic.
124 * @param __first An input iterator.
125 * @param __last An input iterator.
126 * @return The distance between them.
127 *
128 * Returns @c n such that __first + n == __last. This requires
129 * that @p __last must be reachable from @p __first. Note that @c
130 * n may be negative.
131 *
132 * For random access iterators, this uses their @c + and @c - operations
133 * and are constant time. For other %iterator classes they are linear time.
134 */
135 template<typename _InputIterator>
136 inline _GLIBCXX17_CONSTEXPR
137 typename iterator_traits<_InputIterator>::difference_type
138 distance(_InputIterator __first, _InputIterator __last)
139 {
140 // concept requirements -- taken care of in __distance
141 return std::__distance(__first, __last,
142 std::__iterator_category(__first));
143 }
144
145 template<typename _InputIterator, typename _Distance>
146 inline _GLIBCXX14_CONSTEXPR void
147 __advance(_InputIterator& __i, _Distance __n, input_iterator_tag)
148 {
149 // concept requirements
150 __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
151 __glibcxx_assert(__n >= 0);
152 while (__n--)
153 ++__i;
154 }
155
156 template<typename _BidirectionalIterator, typename _Distance>
157 inline _GLIBCXX14_CONSTEXPR void
158 __advance(_BidirectionalIterator& __i, _Distance __n,
159 bidirectional_iterator_tag)
160 {
161 // concept requirements
162 __glibcxx_function_requires(_BidirectionalIteratorConcept<
163 _BidirectionalIterator>)
164 if (__n > 0)
165 while (__n--)
166 ++__i;
167 else
168 while (__n++)
169 --__i;
170 }
171
172 template<typename _RandomAccessIterator, typename _Distance>
173 inline _GLIBCXX14_CONSTEXPR void
174 __advance(_RandomAccessIterator& __i, _Distance __n,
175 random_access_iterator_tag)
176 {
177 // concept requirements
178 __glibcxx_function_requires(_RandomAccessIteratorConcept<
179 _RandomAccessIterator>)
180 if (__builtin_constant_p(__n) && __n == 1)
181 ++__i;
182 else if (__builtin_constant_p(__n) && __n == -1)
183 --__i;
184 else
185 __i += __n;
186 }
187
188 /**
189 * @brief A generalization of pointer arithmetic.
190 * @param __i An input iterator.
191 * @param __n The @a delta by which to change @p __i.
192 * @return Nothing.
193 *
194 * This increments @p i by @p n. For bidirectional and random access
195 * iterators, @p __n may be negative, in which case @p __i is decremented.
196 *
197 * For random access iterators, this uses their @c + and @c - operations
198 * and are constant time. For other %iterator classes they are linear time.
199 */
200 template<typename _InputIterator, typename _Distance>
201 inline _GLIBCXX17_CONSTEXPR void
202 advance(_InputIterator& __i, _Distance __n)
203 {
204 // concept requirements -- taken care of in __advance
205 typename iterator_traits<_InputIterator>::difference_type __d = __n;
206 std::__advance(__i, __d, std::__iterator_category(__i));
207 }
208
209#if __cplusplus >= 201103L
210
211 template<typename _InputIterator>
212 inline _GLIBCXX17_CONSTEXPR _InputIterator
213 next(_InputIterator __x, typename
214 iterator_traits<_InputIterator>::difference_type __n = 1)
215 {
216 // concept requirements
217 __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
218 std::advance(__x, __n);
219 return __x;
220 }
221
222 template<typename _BidirectionalIterator>
223 inline _GLIBCXX17_CONSTEXPR _BidirectionalIterator
224 prev(_BidirectionalIterator __x, typename
225 iterator_traits<_BidirectionalIterator>::difference_type __n = 1)
226 {
227 // concept requirements
228 __glibcxx_function_requires(_BidirectionalIteratorConcept<
229 _BidirectionalIterator>)
230 std::advance(__x, -__n);
231 return __x;
232 }
233
234#endif // C++11
235
236_GLIBCXX_END_NAMESPACE_VERSION
237} // namespace
238
239#endif /* _STL_ITERATOR_BASE_FUNCS_H */
240