1// Functions used by iterators -*- C++ -*-
2
3// Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006
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 _ITERATOR_BASE_FUNCS_H
66#define _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 /* _ITERATOR_BASE_FUNCS_H */
183