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

   1 // Functions used by iterators -*- C++ -*-
   2
   3 // Copyright (C) 2001-2022 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_funcs.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
  56  *  functions, such as distance() and advance().
  57  */
  58
  59 #ifndef _STL_ITERATOR_BASE_FUNCS_H
  60 #define _STL_ITERATOR_BASE_FUNCS_H 1
  61
  62 #pragma GCC system_header
  63
  64 #include <bits/concept_check.h>
  65 #include <debug/assertions.h>
  66
  67 namespace std _GLIBCXX_VISIBILITY(default)
  68 {
  69 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  70
  71 _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
  72   // Forward declaration for the overloads of __distance.
  73   template <typename> struct _List_iterator;
  74   template <typename> struct _List_const_iterator;
  75 _GLIBCXX_END_NAMESPACE_CONTAINER
  76
  77   template<typename _InputIterator>
  78     inline _GLIBCXX14_CONSTEXPR
  79     typename iterator_traits<_InputIterator>::difference_type
  80     __distance(_InputIterator __first, _InputIterator __last,
  81                input_iterator_tag)
  82     {
  83       // concept requirements
  84       __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
  85
  86       typename iterator_traits<_InputIterator>::difference_type __n = 0;
  87       while (__first != __last)
  88         {
  89           ++__first;
  90           ++__n;
  91         }
  92       return __n;
  93     }
  94
  95   template<typename _RandomAccessIterator>
  96     inline _GLIBCXX14_CONSTEXPR
  97     typename iterator_traits<_RandomAccessIterator>::difference_type
  98     __distance(_RandomAccessIterator __first, _RandomAccessIterator __last,
  99                random_access_iterator_tag)
 100     {
 101       // concept requirements
 102       __glibcxx_function_requires(_RandomAccessIteratorConcept<
 103                                   _RandomAccessIterator>)
 104       return __last - __first;
 105     }
 106
 107 #if _GLIBCXX_USE_CXX11_ABI
 108   // Forward declaration because of the qualified call in distance.
 109   template<typename _Tp>
 110     ptrdiff_t
 111     __distance(_GLIBCXX_STD_C::_List_iterator<_Tp>,
 112                _GLIBCXX_STD_C::_List_iterator<_Tp>,
 113                input_iterator_tag);
 114
 115   template<typename _Tp>
 116     ptrdiff_t
 117     __distance(_GLIBCXX_STD_C::_List_const_iterator<_Tp>,
 118                _GLIBCXX_STD_C::_List_const_iterator<_Tp>,
 119                input_iterator_tag);
 120 #endif
 121
 122 #if __cplusplus >= 201103L
 123   // Give better error if std::distance called with a non-Cpp17InputIterator.
 124   template<typename _OutputIterator>
 125     void
 126     __distance(_OutputIterator, _OutputIterator, output_iterator_tag) = delete;
 127 #endif
 128
 129   /**
 130    *  @brief A generalization of pointer arithmetic.
 131    *  @param  __first  An input iterator.
 132    *  @param  __last  An input iterator.
 133    *  @return  The distance between them.
 134    *
 135    *  Returns @c n such that __first + n == __last.  This requires
 136    *  that @p __last must be reachable from @p __first.  Note that @c
 137    *  n may be negative.
 138    *
 139    *  For random access iterators, this uses their @c + and @c - operations
 140    *  and are constant time.  For other %iterator classes they are linear time.
 141   */
 142   template<typename _InputIterator>
 143     _GLIBCXX_NODISCARD
 144     inline _GLIBCXX17_CONSTEXPR
 145     typename iterator_traits<_InputIterator>::difference_type
 146     distance(_InputIterator __first, _InputIterator __last)
 147     {
 148       // concept requirements -- taken care of in __distance
 149       return std::__distance(__first, __last,
 150                              std::__iterator_category(__first));
 151     }
 152
 153   template<typename _InputIterator, typename _Distance>
 154     inline _GLIBCXX14_CONSTEXPR void
 155     __advance(_InputIterator& __i, _Distance __n, input_iterator_tag)
 156     {
 157       // concept requirements
 158       __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
 159       __glibcxx_assert(__n >= 0);
 160       while (__n--)
 161         ++__i;
 162     }
 163
 164   template<typename _BidirectionalIterator, typename _Distance>
 165     inline _GLIBCXX14_CONSTEXPR void
 166     __advance(_BidirectionalIterator& __i, _Distance __n,
 167               bidirectional_iterator_tag)
 168     {
 169       // concept requirements
 170       __glibcxx_function_requires(_BidirectionalIteratorConcept<
 171                                   _BidirectionalIterator>)
 172       if (__n > 0)
 173         while (__n--)
 174           ++__i;
 175       else
 176         while (__n++)
 177           --__i;
 178     }
 179
 180   template<typename _RandomAccessIterator, typename _Distance>
 181     inline _GLIBCXX14_CONSTEXPR void
 182     __advance(_RandomAccessIterator& __i, _Distance __n,
 183               random_access_iterator_tag)
 184     {
 185       // concept requirements
 186       __glibcxx_function_requires(_RandomAccessIteratorConcept<
 187                                   _RandomAccessIterator>)
 188       if (__builtin_constant_p(__n) && __n == 1)
 189         ++__i;
 190       else if (__builtin_constant_p(__n) && __n == -1)
 191         --__i;
 192       else
 193         __i += __n;
 194     }
 195
 196 #if __cplusplus >= 201103L
 197   // Give better error if std::advance called with a non-Cpp17InputIterator.
 198   template<typename _OutputIterator, typename _Distance>
 199     void
 200     __advance(_OutputIterator&, _Distance, output_iterator_tag) = delete;
 201 #endif
 202
 203   /**
 204    *  @brief A generalization of pointer arithmetic.
 205    *  @param  __i  An input iterator.
 206    *  @param  __n  The @a delta by which to change @p __i.
 207    *  @return  Nothing.
 208    *
 209    *  This increments @p i by @p n.  For bidirectional and random access
 210    *  iterators, @p __n may be negative, in which case @p __i is decremented.
 211    *
 212    *  For random access iterators, this uses their @c + and @c - operations
 213    *  and are constant time.  For other %iterator classes they are linear time.
 214   */
 215   template<typename _InputIterator, typename _Distance>
 216     inline _GLIBCXX17_CONSTEXPR void
 217     advance(_InputIterator& __i, _Distance __n)
 218     {
 219       // concept requirements -- taken care of in __advance
 220       typename iterator_traits<_InputIterator>::difference_type __d = __n;
 221       std::__advance(__i, __d, std::__iterator_category(__i));
 222     }
 223
 224 #if __cplusplus >= 201103L
 225
 226   template<typename _InputIterator>
 227     _GLIBCXX_NODISCARD
 228     inline _GLIBCXX17_CONSTEXPR _InputIterator
 229     next(_InputIterator __x, typename
 230          iterator_traits<_InputIterator>::difference_type __n = 1)
 231     {
 232       // concept requirements
 233       __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
 234       std::advance(__x, __n);
 235       return __x;
 236     }
 237
 238   template<typename _BidirectionalIterator>
 239     _GLIBCXX_NODISCARD
 240     inline _GLIBCXX17_CONSTEXPR _BidirectionalIterator
 241     prev(_BidirectionalIterator __x, typename
 242          iterator_traits<_BidirectionalIterator>::difference_type __n = 1)
 243     {
 244       // concept requirements
 245       __glibcxx_function_requires(_BidirectionalIteratorConcept<
 246                                   _BidirectionalIterator>)
 247       std::advance(__x, -__n);
 248       return __x;
 249     }
 250
 251 #endif // C++11
 252
 253 _GLIBCXX_END_NAMESPACE_VERSION
 254 } // namespace
 255
 256 #endif /* _STL_ITERATOR_BASE_FUNCS_H */