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

   1 // Functions used by iterators -*- C++ -*-
   2
   3 // Copyright (C) 2001, 2002, 2003 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 2, 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 // You should have received a copy of the GNU General Public License along
  17 // with this library; see the file COPYING.  If not, write to the Free
  18 // Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
  19 // USA.
  20
  21 // As a special exception, you may use this file as part of a free software
  22 // library without restriction.  Specifically, if other files instantiate
  23 // templates or use macros or inline functions from this file, or you compile
  24 // this file and link it with other files to produce an executable, this
  25 // file does not by itself cause the resulting executable to be covered by
  26 // the GNU General Public License.  This exception does not however
  27 // invalidate any other reasons why the executable file might be covered by
  28 // the GNU General Public License.
  29
  30 /*
  31  *
  32  * Copyright (c) 1994
  33  * Hewlett-Packard Company
  34  *
  35  * Permission to use, copy, modify, distribute and sell this software
  36  * and its documentation for any purpose is hereby granted without fee,
  37  * provided that the above copyright notice appear in all copies and
  38  * that both that copyright notice and this permission notice appear
  39  * in supporting documentation.  Hewlett-Packard Company makes no
  40  * representations about the suitability of this software for any
  41  * purpose.  It is provided "as is" without express or implied warranty.
  42  *
  43  *
  44  * Copyright (c) 1996-1998
  45  * Silicon Graphics Computer Systems, Inc.
  46  *
  47  * Permission to use, copy, modify, distribute and sell this software
  48  * and its documentation for any purpose is hereby granted without fee,
  49  * provided that the above copyright notice appear in all copies and
  50  * that both that copyright notice and this permission notice appear
  51  * in supporting documentation.  Silicon Graphics makes no
  52  * representations about the suitability of this software for any
  53  * purpose.  It is provided "as is" without express or implied warranty.
  54  */
  55
  56 /** @file stl_iterator_base_funcs.h
  57  *  This is an internal header file, included by other library headers.
  58  *  You should not attempt to use it directly.
  59  *
  60  *  This file contains all of the general iterator-related utility
  61  *  functions, such as distance() and advance().
  62  */
  63
  64 #ifndef _ITERATOR_BASE_FUNCS_H
  65 #define _ITERATOR_BASE_FUNCS_H 1
  66
  67 #pragma GCC system_header
  68 #include <bits/concept_check.h>
  69
  70 namespace std
  71 {
  72   template<typename _InputIterator>
  73     inline typename iterator_traits<_InputIterator>::difference_type
  74     __distance(_InputIterator __first, _InputIterator __last,
  75                input_iterator_tag)
  76     {
  77       // concept requirements
  78       __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
  79
  80       typename iterator_traits<_InputIterator>::difference_type __n = 0;
  81       while (__first != __last) {
  82         ++__first; ++__n;
  83       }
  84       return __n;
  85     }
  86
  87   template<typename _RandomAccessIterator>
  88     inline typename iterator_traits<_RandomAccessIterator>::difference_type
  89     __distance(_RandomAccessIterator __first, _RandomAccessIterator __last,
  90                random_access_iterator_tag)
  91     {
  92       // concept requirements
  93       __glibcxx_function_requires(_RandomAccessIteratorConcept<_RandomAccessIterator>)
  94       return __last - __first;
  95     }
  96
  97   /**
  98    *  @brief A generalization of pointer arithmetic.
  99    *  @param  first  An input iterator.
 100    *  @param  last  An input iterator.
 101    *  @return  The distance between them.
 102    *
 103    *  Returns @c n such that first + n == last.  This requires that @p last
 104    *  must be reachable from @p first.  Note that @c n may be negative.
 105    *
 106    *  For random access iterators, this uses their @c + and @c - operations
 107    *  and are constant time.  For other %iterator classes they are linear time.
 108   */
 109   template<typename _InputIterator>
 110     inline typename iterator_traits<_InputIterator>::difference_type
 111     distance(_InputIterator __first, _InputIterator __last)
 112     {
 113       // concept requirements -- taken care of in __distance
 114       return std::__distance(__first, __last, std::__iterator_category(__first));
 115     }
 116
 117   template<typename _InputIterator, typename _Distance>
 118     inline void
 119     __advance(_InputIterator& __i, _Distance __n, input_iterator_tag)
 120     {
 121       // concept requirements
 122       __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
 123       while (__n--) ++__i;
 124     }
 125
 126   template<typename _BidirectionalIterator, typename _Distance>
 127     inline void
 128     __advance(_BidirectionalIterator& __i, _Distance __n,
 129               bidirectional_iterator_tag)
 130     {
 131       // concept requirements
 132       __glibcxx_function_requires(_BidirectionalIteratorConcept<_BidirectionalIterator>)
 133
 134       if (__n > 0)
 135         while (__n--) ++__i;
 136       else
 137         while (__n++) --__i;
 138     }
 139
 140   template<typename _RandomAccessIterator, typename _Distance>
 141     inline void
 142     __advance(_RandomAccessIterator& __i, _Distance __n,
 143               random_access_iterator_tag)
 144     {
 145       // concept requirements
 146       __glibcxx_function_requires(_RandomAccessIteratorConcept<_RandomAccessIterator>)
 147       __i += __n;
 148     }
 149
 150   /**
 151    *  @brief A generalization of pointer arithmetic.
 152    *  @param  i  An input iterator.
 153    *  @param  n  The "delta" by which to change @p i.
 154    *  @return  Nothing.
 155    *
 156    *  This increments @p i by @p n.  For bidirectional and random access
 157    *  iterators, @p n may be negative, in which case @p i is decremented.
 158    *
 159    *  For random access iterators, this uses their @c + and @c - operations
 160    *  and are constant time.  For other %iterator classes they are linear time.
 161   */
 162   template<typename _InputIterator, typename _Distance>
 163     inline void
 164     advance(_InputIterator& __i, _Distance __n)
 165     {
 166       // concept requirements -- taken care of in __advance
 167       std::__advance(__i, __n, std::__iterator_category(__i));
 168     }
 169 } // namespace std
 170
 171 #endif /* _ITERATOR_BASE_FUNCS_H */