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

   1 // Functions used by iterators -*- C++ -*-
   2
   3 // Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007
   4 // Free Software Foundation, Inc.
   5 //
   6 // This file is part of the GNU ISO C++ Library.  This library is free
   7 // software; you can redistribute it and/or modify it under the
   8 // terms of the GNU General Public License as published by the
   9 // Free Software Foundation; either version 2, or (at your option)
  10 // any later version.
  11
  12 // This library is distributed in the hope that it will be useful,
  13 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 // GNU General Public License for more details.
  16
  17 // You should have received a copy of the GNU General Public License along
  18 // with this library; see the file COPYING.  If not, write to the Free
  19 // Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
  20 // USA.
  21
  22 // As a special exception, you may use this file as part of a free software
  23 // library without restriction.  Specifically, if other files instantiate
  24 // templates or use macros or inline functions from this file, or you compile
  25 // this file and link it with other files to produce an executable, this
  26 // file does not by itself cause the resulting executable to be covered by
  27 // the GNU General Public License.  This exception does not however
  28 // invalidate any other reasons why the executable file might be covered by
  29 // the GNU General Public License.
  30
  31 /*
  32  *
  33  * Copyright (c) 1994
  34  * Hewlett-Packard Company
  35  *
  36  * Permission to use, copy, modify, distribute and sell this software
  37  * and its documentation for any purpose is hereby granted without fee,
  38  * provided that the above copyright notice appear in all copies and
  39  * that both that copyright notice and this permission notice appear
  40  * in supporting documentation.  Hewlett-Packard Company makes no
  41  * representations about the suitability of this software for any
  42  * purpose.  It is provided "as is" without express or implied warranty.
  43  *
  44  *
  45  * Copyright (c) 1996-1998
  46  * Silicon Graphics Computer Systems, Inc.
  47  *
  48  * Permission to use, copy, modify, distribute and sell this software
  49  * and its documentation for any purpose is hereby granted without fee,
  50  * provided that the above copyright notice appear in all copies and
  51  * that both that copyright notice and this permission notice appear
  52  * in supporting documentation.  Silicon Graphics makes no
  53  * representations about the suitability of this software for any
  54  * purpose.  It is provided "as is" without express or implied warranty.
  55  */
  56
  57 /** @file stl_iterator_base_funcs.h
  58  *  This is an internal header file, included by other library headers.
  59  *  You should not attempt to use it directly.
  60  *
  61  *  This file contains all of the general iterator-related utility
  62  *  functions, such as distance() and advance().
  63  */
  64
  65 #ifndef _STL_ITERATOR_BASE_FUNCS_H
  66 #define _STL_ITERATOR_BASE_FUNCS_H 1
  67
  68 #pragma GCC system_header
  69 #include <bits/concept_check.h>
  70
  71 _GLIBCXX_BEGIN_NAMESPACE(std)
  72
  73   template<typename _InputIterator>
  74     inline typename iterator_traits<_InputIterator>::difference_type
  75     __distance(_InputIterator __first, _InputIterator __last,
  76                input_iterator_tag)
  77     {
  78       // concept requirements
  79       __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
  80
  81       typename iterator_traits<_InputIterator>::difference_type __n = 0;
  82       while (__first != __last)
  83         {
  84           ++__first;
  85           ++__n;
  86         }
  87       return __n;
  88     }
  89
  90   template<typename _RandomAccessIterator>
  91     inline typename iterator_traits<_RandomAccessIterator>::difference_type
  92     __distance(_RandomAccessIterator __first, _RandomAccessIterator __last,
  93                random_access_iterator_tag)
  94     {
  95       // concept requirements
  96       __glibcxx_function_requires(_RandomAccessIteratorConcept<
  97                                   _RandomAccessIterator>)
  98       return __last - __first;
  99     }
 100
 101   /**
 102    *  @brief A generalization of pointer arithmetic.
 103    *  @param  first  An input iterator.
 104    *  @param  last  An input iterator.
 105    *  @return  The distance between them.
 106    *
 107    *  Returns @c n such that first + n == last.  This requires that @p last
 108    *  must be reachable from @p first.  Note that @c n may be negative.
 109    *
 110    *  For random access iterators, this uses their @c + and @c - operations
 111    *  and are constant time.  For other %iterator classes they are linear time.
 112   */
 113   template<typename _InputIterator>
 114     inline typename iterator_traits<_InputIterator>::difference_type
 115     distance(_InputIterator __first, _InputIterator __last)
 116     {
 117       // concept requirements -- taken care of in __distance
 118       return std::__distance(__first, __last,
 119                              std::__iterator_category(__first));
 120     }
 121
 122   template<typename _InputIterator, typename _Distance>
 123     inline void
 124     __advance(_InputIterator& __i, _Distance __n, input_iterator_tag)
 125     {
 126       // concept requirements
 127       __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
 128       while (__n--)
 129         ++__i;
 130     }
 131
 132   template<typename _BidirectionalIterator, typename _Distance>
 133     inline void
 134     __advance(_BidirectionalIterator& __i, _Distance __n,
 135               bidirectional_iterator_tag)
 136     {
 137       // concept requirements
 138       __glibcxx_function_requires(_BidirectionalIteratorConcept<
 139                                   _BidirectionalIterator>)
 140       if (__n > 0)
 141         while (__n--)
 142           ++__i;
 143       else
 144         while (__n++)
 145           --__i;
 146     }
 147
 148   template<typename _RandomAccessIterator, typename _Distance>
 149     inline void
 150     __advance(_RandomAccessIterator& __i, _Distance __n,
 151               random_access_iterator_tag)
 152     {
 153       // concept requirements
 154       __glibcxx_function_requires(_RandomAccessIteratorConcept<
 155                                   _RandomAccessIterator>)
 156       __i += __n;
 157     }
 158
 159   /**
 160    *  @brief A generalization of pointer arithmetic.
 161    *  @param  i  An input iterator.
 162    *  @param  n  The "delta" by which to change @p i.
 163    *  @return  Nothing.
 164    *
 165    *  This increments @p i by @p n.  For bidirectional and random access
 166    *  iterators, @p n may be negative, in which case @p i is decremented.
 167    *
 168    *  For random access iterators, this uses their @c + and @c - operations
 169    *  and are constant time.  For other %iterator classes they are linear time.
 170   */
 171   template<typename _InputIterator, typename _Distance>
 172     inline void
 173     advance(_InputIterator& __i, _Distance __n)
 174     {
 175       // concept requirements -- taken care of in __advance
 176       typename iterator_traits<_InputIterator>::difference_type __d = __n;
 177       std::__advance(__i, __d, std::__iterator_category(__i));
 178     }
 179
 180 _GLIBCXX_END_NAMESPACE
 181
 182 #endif /* _STL_ITERATOR_BASE_FUNCS_H */