1 // Types used in iterator implementation -*- 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_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 namespace std _GLIBCXX_VISIBILITY(default) 71 { 72 _GLIBCXX_BEGIN_NAMESPACE_VERSION 73 74 /** 75 * @defgroup iterators Iterators 76 * Abstractions for uniform iterating through various underlying types. 77 */ 78 //@{ 79 80 /** 81 * @defgroup iterator_tags Iterator Tags 82 * These are empty types, used to distinguish different iterators. The 83 * distinction is not made by what they contain, but simply by what they 84 * are. Different underlying algorithms can then be used based on the 85 * different operations supported by different iterator types. 86 */ 87 //@{ 88 /// Marking input iterators. 89 struct input_iterator_tag { }; 90 91 /// Marking output iterators. 92 struct output_iterator_tag { }; 93 94 /// Forward iterators support a superset of input iterator operations. 95 struct forward_iterator_tag : public input_iterator_tag { }; 96 97 /// Bidirectional iterators support a superset of forward iterator 98 /// operations. 99 struct bidirectional_iterator_tag : public forward_iterator_tag { }; 100 101 /// Random-access iterators support a superset of bidirectional 102 /// iterator operations. 103 struct random_access_iterator_tag : public bidirectional_iterator_tag { }; 104 //@} 105 106 /** 107 * @brief Common %iterator class. 108 * 109 * This class does nothing but define nested typedefs. %Iterator classes 110 * can inherit from this class to save some work. The typedefs are then 111 * used in specializations and overloading. 112 * 113 * In particular, there are no default implementations of requirements 114 * such as @c operator++ and the like. (How could there be?) 115 */ 116 template<typename _Category, typename _Tp, typename _Distance = ptrdiff_t, 117 typename _Pointer = _Tp*, typename _Reference = _Tp&> 118 struct iterator 119 { 120 /// One of the @link iterator_tags tag types@endlink. 121 typedef _Category iterator_category; 122 /// The type "pointed to" by the iterator. 123 typedef _Tp value_type; 124 /// Distance between iterators is represented as this type. 125 typedef _Distance difference_type; 126 /// This type represents a pointer-to-value_type. 127 typedef _Pointer pointer; 128 /// This type represents a reference-to-value_type. 129 typedef _Reference reference; 130 }; 131 132 /** 133 * @brief Traits class for iterators. 134 * 135 * This class does nothing but define nested typedefs. The general 136 * version simply @a forwards the nested typedefs from the Iterator 137 * argument. Specialized versions for pointers and pointers-to-const 138 * provide tighter, more correct semantics. 139 */ 140 #if __cplusplus >= 201103L 141 // _GLIBCXX_RESOLVE_LIB_DEFECTS 142 // 2408. SFINAE-friendly common_type/iterator_traits is missing in C++14 143 template<typename _Iterator, typename = __void_t<>> 144 struct __iterator_traits { }; 145 146 template<typename _Iterator> 147 struct __iterator_traits<_Iterator, 148 __void_t<typename _Iterator::iterator_category, 149 typename _Iterator::value_type, 150 typename _Iterator::difference_type, 151 typename _Iterator::pointer, 152 typename _Iterator::reference>> 153 { 154 typedef typename _Iterator::iterator_category iterator_category; 155 typedef typename _Iterator::value_type value_type; 156 typedef typename _Iterator::difference_type difference_type; 157 typedef typename _Iterator::pointer pointer; 158 typedef typename _Iterator::reference reference; 159 }; 160 161 template<typename _Iterator> 162 struct iterator_traits 163 : public __iterator_traits<_Iterator> { }; 164 #else 165 template<typename _Iterator> 166 struct iterator_traits 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 175 176 /// Partial specialization for pointer types. 177 template<typename _Tp> 178 struct iterator_traits<_Tp*> 179 { 180 typedef random_access_iterator_tag iterator_category; 181 typedef _Tp value_type; 182 typedef ptrdiff_t difference_type; 183 typedef _Tp* pointer; 184 typedef _Tp& reference; 185 }; 186 187 /// Partial specialization for const pointer types. 188 template<typename _Tp> 189 struct iterator_traits<const _Tp*> 190 { 191 typedef random_access_iterator_tag iterator_category; 192 typedef _Tp value_type; 193 typedef ptrdiff_t difference_type; 194 typedef const _Tp* pointer; 195 typedef const _Tp& reference; 196 }; 197 198 /** 199 * This function is not a part of the C++ standard but is syntactic 200 * sugar for internal library use only. 201 */ 202 template<typename _Iter> 203 inline _GLIBCXX_CONSTEXPR 204 typename iterator_traits<_Iter>::iterator_category 205 __iterator_category(const _Iter&) 206 { return typename iterator_traits<_Iter>::iterator_category(); } 207 208 //@} 209 210 #if __cplusplus < 201103L 211 // If _Iterator has a base returns it otherwise _Iterator is returned 212 // untouched 213 template<typename _Iterator, bool _HasBase> 214 struct _Iter_base 215 { 216 typedef _Iterator iterator_type; 217 static iterator_type _S_base(_Iterator __it) 218 { return __it; } 219 }; 220 221 template<typename _Iterator> 222 struct _Iter_base<_Iterator, true> 223 { 224 typedef typename _Iterator::iterator_type iterator_type; 225 static iterator_type _S_base(_Iterator __it) 226 { return __it.base(); } 227 }; 228 #endif 229 230 #if __cplusplus >= 201103L 231 template<typename _InIter> 232 using _RequireInputIter = typename 233 enable_if<is_convertible<typename 234 iterator_traits<_InIter>::iterator_category, 235 input_iterator_tag>::value>::type; 236 #endif 237 238 _GLIBCXX_END_NAMESPACE_VERSION 239 } // namespace 240 241 #endif /* _STL_ITERATOR_BASE_TYPES_H */ 242 243