libstdc++-v3/include/bits/stl_iterator_base_types.h

   1 // Types used in iterator implementation -*- C++ -*-
   2
   3 // Copyright (C) 2001-2024 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 #if __cplusplus > 201703L && __cpp_concepts >= 201907L
  71 # include <bits/iterator_concepts.h>
  72 #endif
  73
  74 namespace std _GLIBCXX_VISIBILITY(default)
  75 {
  76 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  77
  78   /**
  79    *  @defgroup iterators Iterators
  80    *  Abstractions for uniform iterating through various underlying types.
  81   */
  82   ///@{
  83
  84   /**
  85    *  @defgroup iterator_tags Iterator Tags
  86    *  These are empty types, used to distinguish different iterators.  The
  87    *  distinction is not made by what they contain, but simply by what they
  88    *  are.  Different underlying algorithms can then be used based on the
  89    *  different operations supported by different iterator types.
  90   */
  91   ///@{
  92   ///  Marking input iterators.
  93   struct input_iterator_tag { };
  94
  95   ///  Marking output iterators.
  96   struct output_iterator_tag { };
  97
  98   /// Forward iterators support a superset of input iterator operations.
  99   struct forward_iterator_tag : public input_iterator_tag { };
 100
 101   /// Bidirectional iterators support a superset of forward iterator
 102   /// operations.
 103   struct bidirectional_iterator_tag : public forward_iterator_tag { };
 104
 105   /// Random-access iterators support a superset of bidirectional
 106   /// iterator operations.
 107   struct random_access_iterator_tag : public bidirectional_iterator_tag { };
 108
 109 #if __cplusplus > 201703L
 110   /// Contiguous iterators point to objects stored contiguously in memory.
 111   struct contiguous_iterator_tag : public random_access_iterator_tag { };
 112 #endif
 113   ///@}
 114
 115   /**
 116    *  @brief  Common %iterator class.
 117    *
 118    *  This class does nothing but define nested typedefs.  %Iterator classes
 119    *  can inherit from this class to save some work.  The typedefs are then
 120    *  used in specializations and overloading.
 121    *
 122    *  In particular, there are no default implementations of requirements
 123    *  such as @c operator++ and the like.  (How could there be?)
 124   */
 125   template<typename _Category, typename _Tp, typename _Distance = ptrdiff_t,
 126            typename _Pointer = _Tp*, typename _Reference = _Tp&>
 127     struct _GLIBCXX17_DEPRECATED iterator
 128     {
 129       /// One of the @link iterator_tags tag types@endlink.
 130       typedef _Category  iterator_category;
 131       /// The type "pointed to" by the iterator.
 132       typedef _Tp        value_type;
 133       /// Distance between iterators is represented as this type.
 134       typedef _Distance  difference_type;
 135       /// This type represents a pointer-to-value_type.
 136       typedef _Pointer   pointer;
 137       /// This type represents a reference-to-value_type.
 138       typedef _Reference reference;
 139     };
 140
 141   /**
 142    *  @brief  Traits class for iterators.
 143    *
 144    *  This class does nothing but define nested typedefs.  The general
 145    *  version simply @a forwards the nested typedefs from the Iterator
 146    *  argument.  Specialized versions for pointers and pointers-to-const
 147    *  provide tighter, more correct semantics.
 148   */
 149   template<typename _Iterator>
 150     struct iterator_traits;
 151
 152 #if __cplusplus >= 201103L
 153   // _GLIBCXX_RESOLVE_LIB_DEFECTS
 154   // 2408. SFINAE-friendly common_type/iterator_traits is missing in C++14
 155   template<typename _Iterator, typename = __void_t<>>
 156     struct __iterator_traits { };
 157
 158 #if ! __cpp_lib_concepts
 159
 160   template<typename _Iterator>
 161     struct __iterator_traits<_Iterator,
 162                              __void_t<typename _Iterator::iterator_category,
 163                                       typename _Iterator::value_type,
 164                                       typename _Iterator::difference_type,
 165                                       typename _Iterator::pointer,
 166                                       typename _Iterator::reference>>
 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 // ! concepts
 175
 176   template<typename _Iterator>
 177     struct iterator_traits
 178     : public __iterator_traits<_Iterator> { };
 179
 180 #else // ! C++11
 181   template<typename _Iterator>
 182     struct iterator_traits
 183     {
 184       typedef typename _Iterator::iterator_category iterator_category;
 185       typedef typename _Iterator::value_type        value_type;
 186       typedef typename _Iterator::difference_type   difference_type;
 187       typedef typename _Iterator::pointer           pointer;
 188       typedef typename _Iterator::reference         reference;
 189     };
 190 #endif // C++11
 191
 192 #if __cplusplus > 201703L
 193   /// Partial specialization for object pointer types.
 194   template<typename _Tp>
 195 #if __cpp_concepts >= 201907L
 196     requires is_object_v<_Tp>
 197 #endif
 198     struct iterator_traits<_Tp*>
 199     {
 200       using iterator_concept  = contiguous_iterator_tag;
 201       using iterator_category = random_access_iterator_tag;
 202       using value_type        = remove_cv_t<_Tp>;
 203       using difference_type   = ptrdiff_t;
 204       using pointer           = _Tp*;
 205       using reference         = _Tp&;
 206     };
 207 #else
 208   /// Partial specialization for pointer types.
 209   template<typename _Tp>
 210     struct iterator_traits<_Tp*>
 211     {
 212       typedef random_access_iterator_tag iterator_category;
 213       typedef _Tp                         value_type;
 214       typedef ptrdiff_t                   difference_type;
 215       typedef _Tp*                        pointer;
 216       typedef _Tp&                        reference;
 217     };
 218
 219   /// Partial specialization for const pointer types.
 220   template<typename _Tp>
 221     struct iterator_traits<const _Tp*>
 222     {
 223       typedef random_access_iterator_tag iterator_category;
 224       typedef _Tp                         value_type;
 225       typedef ptrdiff_t                   difference_type;
 226       typedef const _Tp*                  pointer;
 227       typedef const _Tp&                  reference;
 228     };
 229 #endif
 230
 231   /**
 232    *  This function is not a part of the C++ standard but is syntactic
 233    *  sugar for internal library use only.
 234   */
 235   template<typename _Iter>
 236     __attribute__((__always_inline__))
 237     inline _GLIBCXX_CONSTEXPR
 238     typename iterator_traits<_Iter>::iterator_category
 239     __iterator_category(const _Iter&)
 240     { return typename iterator_traits<_Iter>::iterator_category(); }
 241
 242   ///@}
 243
 244 #if __cplusplus >= 201103L
 245   template<typename _Iter>
 246     using __iter_category_t
 247       = typename iterator_traits<_Iter>::iterator_category;
 248
 249   template<typename _InIter>
 250     using _RequireInputIter =
 251       __enable_if_t<is_convertible<__iter_category_t<_InIter>,
 252                                    input_iterator_tag>::value>;
 253
 254   template<typename _It,
 255            typename _Cat = __iter_category_t<_It>>
 256     struct __is_random_access_iter
 257       : is_base_of<random_access_iterator_tag, _Cat>
 258     {
 259       typedef is_base_of<random_access_iterator_tag, _Cat> _Base;
 260       enum { __value = _Base::value };
 261     };
 262 #else
 263   template<typename _It, typename _Traits = iterator_traits<_It>,
 264            typename _Cat = typename _Traits::iterator_category>
 265     struct __is_random_access_iter
 266     { enum { __value = __is_base_of(random_access_iterator_tag, _Cat) }; };
 267 #endif
 268
 269 _GLIBCXX_END_NAMESPACE_VERSION
 270 } // namespace
 271
 272 #endif /* _STL_ITERATOR_BASE_TYPES_H */