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

   1 // Types used in iterator implementation -*- C++ -*-
   2
   3 // Copyright (C) 2001-2015 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 typename iterator_traits<_Iter>::iterator_category
 204     __iterator_category(const _Iter&)
 205     { return typename iterator_traits<_Iter>::iterator_category(); }
 206
 207   //@}
 208
 209 #if __cplusplus < 201103L
 210   // If _Iterator has a base returns it otherwise _Iterator is returned
 211   // untouched
 212   template<typename _Iterator, bool _HasBase>
 213     struct _Iter_base
 214     {
 215       typedef _Iterator iterator_type;
 216       static iterator_type _S_base(_Iterator __it)
 217       { return __it; }
 218     };
 219
 220   template<typename _Iterator>
 221     struct _Iter_base<_Iterator, true>
 222     {
 223       typedef typename _Iterator::iterator_type iterator_type;
 224       static iterator_type _S_base(_Iterator __it)
 225       { return __it.base(); }
 226     };
 227 #endif
 228
 229 #if __cplusplus >= 201103L
 230   template<typename _InIter>
 231     using _RequireInputIter = typename
 232       enable_if<is_convertible<typename
 233                 iterator_traits<_InIter>::iterator_category,
 234                                input_iterator_tag>::value>::type;
 235 #endif
 236
 237 _GLIBCXX_END_NAMESPACE_VERSION
 238 } // namespace
 239
 240 #endif /* _STL_ITERATOR_BASE_TYPES_H */
 241