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

   1 // Functions used by iterators -*- 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_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_CONTAINER
  70   // Forward declaration for the overloads of __distance.
  71   template <typename> struct _List_iterator;
  72   template <typename> struct _List_const_iterator;
  73 _GLIBCXX_END_NAMESPACE_CONTAINER
  74
  75 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  76
  77   template<typename _InputIterator>
  78     inline typename iterator_traits<_InputIterator>::difference_type
  79     __distance(_InputIterator __first, _InputIterator __last,
  80                input_iterator_tag)
  81     {
  82       // concept requirements
  83       __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
  84
  85       typename iterator_traits<_InputIterator>::difference_type __n = 0;
  86       while (__first != __last)
  87         {
  88           ++__first;
  89           ++__n;
  90         }
  91       return __n;
  92     }
  93
  94   template<typename _RandomAccessIterator>
  95     inline typename iterator_traits<_RandomAccessIterator>::difference_type
  96     __distance(_RandomAccessIterator __first, _RandomAccessIterator __last,
  97                random_access_iterator_tag)
  98     {
  99       // concept requirements
 100       __glibcxx_function_requires(_RandomAccessIteratorConcept<
 101                                   _RandomAccessIterator>)
 102       return __last - __first;
 103     }
 104
 105 #if _GLIBCXX_USE_CXX11_ABI
 106   // Forward declaration because of the qualified call in distance.
 107   template<typename _Tp>
 108     ptrdiff_t
 109     __distance(_GLIBCXX_STD_C::_List_iterator<_Tp>,
 110                _GLIBCXX_STD_C::_List_iterator<_Tp>,
 111                input_iterator_tag);
 112
 113   template<typename _Tp>
 114     ptrdiff_t
 115     __distance(_GLIBCXX_STD_C::_List_const_iterator<_Tp>,
 116                _GLIBCXX_STD_C::_List_const_iterator<_Tp>,
 117                input_iterator_tag);
 118 #endif
 119
 120   /**
 121    *  @brief A generalization of pointer arithmetic.
 122    *  @param  __first  An input iterator.
 123    *  @param  __last  An input iterator.
 124    *  @return  The distance between them.
 125    *
 126    *  Returns @c n such that __first + n == __last.  This requires
 127    *  that @p __last must be reachable from @p __first.  Note that @c
 128    *  n may be negative.
 129    *
 130    *  For random access iterators, this uses their @c + and @c - operations
 131    *  and are constant time.  For other %iterator classes they are linear time.
 132   */
 133   template<typename _InputIterator>
 134     inline typename iterator_traits<_InputIterator>::difference_type
 135     distance(_InputIterator __first, _InputIterator __last)
 136     {
 137       // concept requirements -- taken care of in __distance
 138       return std::__distance(__first, __last,
 139                              std::__iterator_category(__first));
 140     }
 141
 142   template<typename _InputIterator, typename _Distance>
 143     inline void
 144     __advance(_InputIterator& __i, _Distance __n, input_iterator_tag)
 145     {
 146       // concept requirements
 147       __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
 148       _GLIBCXX_DEBUG_ASSERT(__n >= 0);
 149       while (__n--)
 150         ++__i;
 151     }
 152
 153   template<typename _BidirectionalIterator, typename _Distance>
 154     inline void
 155     __advance(_BidirectionalIterator& __i, _Distance __n,
 156               bidirectional_iterator_tag)
 157     {
 158       // concept requirements
 159       __glibcxx_function_requires(_BidirectionalIteratorConcept<
 160                                   _BidirectionalIterator>)
 161       if (__n > 0)
 162         while (__n--)
 163           ++__i;
 164       else
 165         while (__n++)
 166           --__i;
 167     }
 168
 169   template<typename _RandomAccessIterator, typename _Distance>
 170     inline void
 171     __advance(_RandomAccessIterator& __i, _Distance __n,
 172               random_access_iterator_tag)
 173     {
 174       // concept requirements
 175       __glibcxx_function_requires(_RandomAccessIteratorConcept<
 176                                   _RandomAccessIterator>)
 177       __i += __n;
 178     }
 179
 180   /**
 181    *  @brief A generalization of pointer arithmetic.
 182    *  @param  __i  An input iterator.
 183    *  @param  __n  The @a delta by which to change @p __i.
 184    *  @return  Nothing.
 185    *
 186    *  This increments @p i by @p n.  For bidirectional and random access
 187    *  iterators, @p __n may be negative, in which case @p __i is decremented.
 188    *
 189    *  For random access iterators, this uses their @c + and @c - operations
 190    *  and are constant time.  For other %iterator classes they are linear time.
 191   */
 192   template<typename _InputIterator, typename _Distance>
 193     inline void
 194     advance(_InputIterator& __i, _Distance __n)
 195     {
 196       // concept requirements -- taken care of in __advance
 197       typename iterator_traits<_InputIterator>::difference_type __d = __n;
 198       std::__advance(__i, __d, std::__iterator_category(__i));
 199     }
 200
 201 #if __cplusplus >= 201103L
 202
 203   template<typename _ForwardIterator>
 204     inline _ForwardIterator
 205     next(_ForwardIterator __x, typename
 206          iterator_traits<_ForwardIterator>::difference_type __n = 1)
 207     {
 208       std::advance(__x, __n);
 209       return __x;
 210     }
 211
 212   template<typename _BidirectionalIterator>
 213     inline _BidirectionalIterator
 214     prev(_BidirectionalIterator __x, typename
 215          iterator_traits<_BidirectionalIterator>::difference_type __n = 1)
 216     {
 217       std::advance(__x, -__n);
 218       return __x;
 219     }
 220
 221 #endif // C++11
 222
 223 _GLIBCXX_END_NAMESPACE_VERSION
 224 } // namespace
 225
 226 #endif /* _STL_ITERATOR_BASE_FUNCS_H */