1 // Functions used by iterators -*- C++ -*-
2
3 // Copyright (C) 2001-2013 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/debug.h>
66
67 namespace std _GLIBCXX_VISIBILITY(default)
68 {
69 _GLIBCXX_BEGIN_NAMESPACE_VERSION
70
71 template<typename _InputIterator>
72 inline typename iterator_traits<_InputIterator>::difference_type
73 __distance(_InputIterator __first, _InputIterator __last,
74 input_iterator_tag)
75 {
76 // concept requirements
77 __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
78
79 typename iterator_traits<_InputIterator>::difference_type __n = 0;
80 while (__first != __last)
81 {
82 ++__first;
83 ++__n;
84 }
85 return __n;
86 }
87
88 template<typename _RandomAccessIterator>
89 inline typename iterator_traits<_RandomAccessIterator>::difference_type
90 __distance(_RandomAccessIterator __first, _RandomAccessIterator __last,
91 random_access_iterator_tag)
92 {
93 // concept requirements
94 __glibcxx_function_requires(_RandomAccessIteratorConcept<
95 _RandomAccessIterator>)
96 return __last - __first;
97 }
98
99 /**
100 * @brief A generalization of pointer arithmetic.
101 * @param __first An input iterator.
102 * @param __last An input iterator.
103 * @return The distance between them.
104 *
105 * Returns @c n such that __first + n == __last. This requires
106 * that @p __last must be reachable from @p __first. Note that @c
107 * n may be negative.
108 *
109 * For random access iterators, this uses their @c + and @c - operations
110 * and are constant time. For other %iterator classes they are linear time.
111 */
112 template<typename _InputIterator>
113 inline typename iterator_traits<_InputIterator>::difference_type
114 distance(_InputIterator __first, _InputIterator __last)
115 {
116 // concept requirements -- taken care of in __distance
117 return std::__distance(__first, __last,
118 std::__iterator_category(__first));
119 }
120
121 template<typename _InputIterator, typename _Distance>
122 inline void
123 __advance(_InputIterator& __i, _Distance __n, input_iterator_tag)
124 {
125 // concept requirements
126 __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
127 _GLIBCXX_DEBUG_ASSERT(__n >= 0);
128 while (__n--)
129 ++__i;
130 }
131
132 template<typename _BidirectionalIterator, typename _Distance>
133 inline void
134 __advance(_BidirectionalIterator& __i, _Distance __n,
135 bidirectional_iterator_tag)
136 {
137 // concept requirements
138 __glibcxx_function_requires(_BidirectionalIteratorConcept<
139 _BidirectionalIterator>)
140 if (__n > 0)
141 while (__n--)
142 ++__i;
143 else
144 while (__n++)
145 --__i;
146 }
147
148 template<typename _RandomAccessIterator, typename _Distance>
149 inline void
150 __advance(_RandomAccessIterator& __i, _Distance __n,
151 random_access_iterator_tag)
152 {
153 // concept requirements
154 __glibcxx_function_requires(_RandomAccessIteratorConcept<
155 _RandomAccessIterator>)
156 __i += __n;
157 }
158
159 /**
160 * @brief A generalization of pointer arithmetic.
161 * @param __i An input iterator.
162 * @param __n The @a delta by which to change @p __i.
163 * @return Nothing.
164 *
165 * This increments @p i by @p n. For bidirectional and random access
166 * iterators, @p __n may be negative, in which case @p __i is decremented.
167 *
168 * For random access iterators, this uses their @c + and @c - operations
169 * and are constant time. For other %iterator classes they are linear time.
170 */
171 template<typename _InputIterator, typename _Distance>
172 inline void
173 advance(_InputIterator& __i, _Distance __n)
174 {
175 // concept requirements -- taken care of in __advance
176 typename iterator_traits<_InputIterator>::difference_type __d = __n;
177 std::__advance(__i, __d, std::__iterator_category(__i));
178 }
179
180 #if __cplusplus >= 201103L
181
182 template<typename _ForwardIterator>
183 inline _ForwardIterator
184 next(_ForwardIterator __x, typename
185 iterator_traits<_ForwardIterator>::difference_type __n = 1)
186 {
187 std::advance(__x, __n);
188 return __x;
189 }
190
191 template<typename _BidirectionalIterator>
192 inline _BidirectionalIterator
193 prev(_BidirectionalIterator __x, typename
194 iterator_traits<_BidirectionalIterator>::difference_type __n = 1)
195 {
196 std::advance(__x, -__n);
197 return __x;
198 }
199
200 #endif // C++11
201
202 _GLIBCXX_END_NAMESPACE_VERSION
203 } // namespace
204
205 #endif /* _STL_ITERATOR_BASE_FUNCS_H */
206