libstdc++
stl_iterator_base_types.h
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1 // Types used in iterator implementation -*- C++ -*-
2 
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4 //
5 // This file is part of the GNU ISO C++ Library. This library is free
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16 // Under Section 7 of GPL version 3, you are granted additional
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24 
25 /*
26  *
27  * Copyright (c) 1994
28  * Hewlett-Packard Company
29  *
30  * Permission to use, copy, modify, distribute and sell this software
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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
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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.
96 
97  /// Bidirectional iterators support a superset of forward iterator
98  /// operations.
100 
101  /// Random-access iterators support a superset of bidirectional
102  /// iterator operations.
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  {
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  {
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 
Traits class for iterators.
Bidirectional iterators support a superset of forward iterator operations.
constexpr iterator_traits< _Iter >::iterator_category __iterator_category(const _Iter &)
_Pointer pointer
This type represents a pointer-to-value_type.
_Category iterator_category
One of the tag types.
_Distance difference_type
Distance between iterators is represented as this type.
ISO C++ entities toplevel namespace is std.
_Reference reference
This type represents a reference-to-value_type.
Marking input iterators.
Common iterator class.
Forward iterators support a superset of input iterator operations.
_Tp value_type
The type "pointed to" by the iterator.
Random-access iterators support a superset of bidirectional iterator operations.
Marking output iterators.