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       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     1029943 :     __iterator_category(const _Iter&)
     206     1029943 :     { 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             :