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       1             : // Types used in iterator implementation -*- C++ -*-
       2             : 
       3             : // Copyright (C) 2001-2021 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 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             :     inline _GLIBCXX_CONSTEXPR
     237             :     typename iterator_traits<_Iter>::iterator_category
     238    11222405 :     __iterator_category(const _Iter&)
     239    11222405 :     { return typename iterator_traits<_Iter>::iterator_category(); }
     240             : 
     241             :   ///@}
     242             : 
     243             : #if __cplusplus >= 201103L
     244             :   template<typename _Iter>
     245             :     using __iterator_category_t
     246             :       = typename iterator_traits<_Iter>::iterator_category;
     247             : 
     248             :   template<typename _InIter>
     249             :     using _RequireInputIter =
     250             :       __enable_if_t<is_convertible<__iterator_category_t<_InIter>,
     251             :                                    input_iterator_tag>::value>;
     252             : 
     253             :   template<typename _It,
     254             :            typename _Cat = __iterator_category_t<_It>>
     255             :     struct __is_random_access_iter
     256             :       : is_base_of<random_access_iterator_tag, _Cat>
     257             :     {
     258             :       typedef is_base_of<random_access_iterator_tag, _Cat> _Base;
     259             :       enum { __value = _Base::value };
     260             :     };
     261             : #else
     262             :   template<typename _It, typename _Traits = iterator_traits<_It>,
     263             :            typename _Cat = typename _Traits::iterator_category>
     264             :     struct __is_random_access_iter
     265             :     { enum { __value = __is_base_of(random_access_iterator_tag, _Cat) }; };
     266             : #endif
     267             : 
     268             : _GLIBCXX_END_NAMESPACE_VERSION
     269             : } // namespace
     270             : 
     271             : #endif /* _STL_ITERATOR_BASE_TYPES_H */