libstdc++
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00001 // Functions used by iterators -*- C++ -*- 00002 00003 // Copyright (C) 2001-2018 Free Software Foundation, Inc. 00004 // 00005 // This file is part of the GNU ISO C++ Library. This library is free 00006 // software; you can redistribute it and/or modify it under the 00007 // terms of the GNU General Public License as published by the 00008 // Free Software Foundation; either version 3, or (at your option) 00009 // any later version. 00010 00011 // This library is distributed in the hope that it will be useful, 00012 // but WITHOUT ANY WARRANTY; without even the implied warranty of 00013 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 00014 // GNU General Public License for more details. 00015 00016 // Under Section 7 of GPL version 3, you are granted additional 00017 // permissions described in the GCC Runtime Library Exception, version 00018 // 3.1, as published by the Free Software Foundation. 00019 00020 // You should have received a copy of the GNU General Public License and 00021 // a copy of the GCC Runtime Library Exception along with this program; 00022 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 00023 // <http://www.gnu.org/licenses/>. 00024 00025 /* 00026 * 00027 * Copyright (c) 1994 00028 * Hewlett-Packard Company 00029 * 00030 * Permission to use, copy, modify, distribute and sell this software 00031 * and its documentation for any purpose is hereby granted without fee, 00032 * provided that the above copyright notice appear in all copies and 00033 * that both that copyright notice and this permission notice appear 00034 * in supporting documentation. Hewlett-Packard Company makes no 00035 * representations about the suitability of this software for any 00036 * purpose. It is provided "as is" without express or implied warranty. 00037 * 00038 * 00039 * Copyright (c) 1996-1998 00040 * Silicon Graphics Computer Systems, Inc. 00041 * 00042 * Permission to use, copy, modify, distribute and sell this software 00043 * and its documentation for any purpose is hereby granted without fee, 00044 * provided that the above copyright notice appear in all copies and 00045 * that both that copyright notice and this permission notice appear 00046 * in supporting documentation. Silicon Graphics makes no 00047 * representations about the suitability of this software for any 00048 * purpose. It is provided "as is" without express or implied warranty. 00049 */ 00050 00051 /** @file bits/stl_iterator_base_funcs.h 00052 * This is an internal header file, included by other library headers. 00053 * Do not attempt to use it directly. @headername{iterator} 00054 * 00055 * This file contains all of the general iterator-related utility 00056 * functions, such as distance() and advance(). 00057 */ 00058 00059 #ifndef _STL_ITERATOR_BASE_FUNCS_H 00060 #define _STL_ITERATOR_BASE_FUNCS_H 1 00061 00062 #pragma GCC system_header 00063 00064 #include <bits/concept_check.h> 00065 #include <debug/assertions.h> 00066 00067 namespace std _GLIBCXX_VISIBILITY(default) 00068 { 00069 _GLIBCXX_BEGIN_NAMESPACE_VERSION 00070 00071 _GLIBCXX_BEGIN_NAMESPACE_CONTAINER 00072 // Forward declaration for the overloads of __distance. 00073 template <typename> struct _List_iterator; 00074 template <typename> struct _List_const_iterator; 00075 _GLIBCXX_END_NAMESPACE_CONTAINER 00076 00077 template<typename _InputIterator> 00078 inline _GLIBCXX14_CONSTEXPR 00079 typename iterator_traits<_InputIterator>::difference_type 00080 __distance(_InputIterator __first, _InputIterator __last, 00081 input_iterator_tag) 00082 { 00083 // concept requirements 00084 __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>) 00085 00086 typename iterator_traits<_InputIterator>::difference_type __n = 0; 00087 while (__first != __last) 00088 { 00089 ++__first; 00090 ++__n; 00091 } 00092 return __n; 00093 } 00094 00095 template<typename _RandomAccessIterator> 00096 inline _GLIBCXX14_CONSTEXPR 00097 typename iterator_traits<_RandomAccessIterator>::difference_type 00098 __distance(_RandomAccessIterator __first, _RandomAccessIterator __last, 00099 random_access_iterator_tag) 00100 { 00101 // concept requirements 00102 __glibcxx_function_requires(_RandomAccessIteratorConcept< 00103 _RandomAccessIterator>) 00104 return __last - __first; 00105 } 00106 00107 #if _GLIBCXX_USE_CXX11_ABI 00108 // Forward declaration because of the qualified call in distance. 00109 template<typename _Tp> 00110 ptrdiff_t 00111 __distance(_GLIBCXX_STD_C::_List_iterator<_Tp>, 00112 _GLIBCXX_STD_C::_List_iterator<_Tp>, 00113 input_iterator_tag); 00114 00115 template<typename _Tp> 00116 ptrdiff_t 00117 __distance(_GLIBCXX_STD_C::_List_const_iterator<_Tp>, 00118 _GLIBCXX_STD_C::_List_const_iterator<_Tp>, 00119 input_iterator_tag); 00120 #endif 00121 00122 /** 00123 * @brief A generalization of pointer arithmetic. 00124 * @param __first An input iterator. 00125 * @param __last An input iterator. 00126 * @return The distance between them. 00127 * 00128 * Returns @c n such that __first + n == __last. This requires 00129 * that @p __last must be reachable from @p __first. Note that @c 00130 * n may be negative. 00131 * 00132 * For random access iterators, this uses their @c + and @c - operations 00133 * and are constant time. For other %iterator classes they are linear time. 00134 */ 00135 template<typename _InputIterator> 00136 inline _GLIBCXX17_CONSTEXPR 00137 typename iterator_traits<_InputIterator>::difference_type 00138 distance(_InputIterator __first, _InputIterator __last) 00139 { 00140 // concept requirements -- taken care of in __distance 00141 return std::__distance(__first, __last, 00142 std::__iterator_category(__first)); 00143 } 00144 00145 template<typename _InputIterator, typename _Distance> 00146 inline _GLIBCXX14_CONSTEXPR void 00147 __advance(_InputIterator& __i, _Distance __n, input_iterator_tag) 00148 { 00149 // concept requirements 00150 __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>) 00151 __glibcxx_assert(__n >= 0); 00152 while (__n--) 00153 ++__i; 00154 } 00155 00156 template<typename _BidirectionalIterator, typename _Distance> 00157 inline _GLIBCXX14_CONSTEXPR void 00158 __advance(_BidirectionalIterator& __i, _Distance __n, 00159 bidirectional_iterator_tag) 00160 { 00161 // concept requirements 00162 __glibcxx_function_requires(_BidirectionalIteratorConcept< 00163 _BidirectionalIterator>) 00164 if (__n > 0) 00165 while (__n--) 00166 ++__i; 00167 else 00168 while (__n++) 00169 --__i; 00170 } 00171 00172 template<typename _RandomAccessIterator, typename _Distance> 00173 inline _GLIBCXX14_CONSTEXPR void 00174 __advance(_RandomAccessIterator& __i, _Distance __n, 00175 random_access_iterator_tag) 00176 { 00177 // concept requirements 00178 __glibcxx_function_requires(_RandomAccessIteratorConcept< 00179 _RandomAccessIterator>) 00180 if (__builtin_constant_p(__n) && __n == 1) 00181 ++__i; 00182 else if (__builtin_constant_p(__n) && __n == -1) 00183 --__i; 00184 else 00185 __i += __n; 00186 } 00187 00188 /** 00189 * @brief A generalization of pointer arithmetic. 00190 * @param __i An input iterator. 00191 * @param __n The @a delta by which to change @p __i. 00192 * @return Nothing. 00193 * 00194 * This increments @p i by @p n. For bidirectional and random access 00195 * iterators, @p __n may be negative, in which case @p __i is decremented. 00196 * 00197 * For random access iterators, this uses their @c + and @c - operations 00198 * and are constant time. For other %iterator classes they are linear time. 00199 */ 00200 template<typename _InputIterator, typename _Distance> 00201 inline _GLIBCXX17_CONSTEXPR void 00202 advance(_InputIterator& __i, _Distance __n) 00203 { 00204 // concept requirements -- taken care of in __advance 00205 typename iterator_traits<_InputIterator>::difference_type __d = __n; 00206 std::__advance(__i, __d, std::__iterator_category(__i)); 00207 } 00208 00209 #if __cplusplus >= 201103L 00210 00211 template<typename _InputIterator> 00212 inline _GLIBCXX17_CONSTEXPR _InputIterator 00213 next(_InputIterator __x, typename 00214 iterator_traits<_InputIterator>::difference_type __n = 1) 00215 { 00216 // concept requirements 00217 __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>) 00218 std::advance(__x, __n); 00219 return __x; 00220 } 00221 00222 template<typename _BidirectionalIterator> 00223 inline _GLIBCXX17_CONSTEXPR _BidirectionalIterator 00224 prev(_BidirectionalIterator __x, typename 00225 iterator_traits<_BidirectionalIterator>::difference_type __n = 1) 00226 { 00227 // concept requirements 00228 __glibcxx_function_requires(_BidirectionalIteratorConcept< 00229 _BidirectionalIterator>) 00230 std::advance(__x, -__n); 00231 return __x; 00232 } 00233 00234 #endif // C++11 00235 00236 _GLIBCXX_END_NAMESPACE_VERSION 00237 } // namespace 00238 00239 #endif /* _STL_ITERATOR_BASE_FUNCS_H */