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1// -*- C++ -*-
2//===----------------------------------------------------------------------===//
3//
4// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5// See https://llvm.org/LICENSE.txt for license information.
6// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7//
8//===----------------------------------------------------------------------===//
9
10#ifndef _LIBCPP___ITERATOR_REVERSE_ITERATOR_H
11#define _LIBCPP___ITERATOR_REVERSE_ITERATOR_H
12
13#include <__algorithm/unwrap_iter.h>
14#include <__compare/compare_three_way_result.h>
15#include <__compare/three_way_comparable.h>
16#include <__concepts/convertible_to.h>
17#include <__config>
18#include <__iterator/advance.h>
19#include <__iterator/concepts.h>
20#include <__iterator/incrementable_traits.h>
21#include <__iterator/iter_move.h>
22#include <__iterator/iter_swap.h>
23#include <__iterator/iterator.h>
24#include <__iterator/iterator_traits.h>
25#include <__iterator/next.h>
26#include <__iterator/prev.h>
27#include <__iterator/readable_traits.h>
28#include <__iterator/segmented_iterator.h>
29#include <__memory/addressof.h>
30#include <__ranges/access.h>
31#include <__ranges/concepts.h>
32#include <__ranges/subrange.h>
33#include <__type_traits/conditional.h>
34#include <__type_traits/enable_if.h>
35#include <__type_traits/is_assignable.h>
36#include <__type_traits/is_convertible.h>
37#include <__type_traits/is_nothrow_constructible.h>
38#include <__type_traits/is_pointer.h>
39#include <__type_traits/is_same.h>
40#include <__utility/declval.h>
41#include <__utility/move.h>
42
43#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
44# pragma GCC system_header
45#endif
46
47_LIBCPP_BEGIN_NAMESPACE_STD
48
49_LIBCPP_SUPPRESS_DEPRECATED_PUSH
50template <class _Iter>
51class reverse_iterator
52#if _LIBCPP_STD_VER <= 14 || !defined(_LIBCPP_ABI_NO_ITERATOR_BASES)
53 : public iterator<typename iterator_traits<_Iter>::iterator_category,
54 typename iterator_traits<_Iter>::value_type,
55 typename iterator_traits<_Iter>::difference_type,
56 typename iterator_traits<_Iter>::pointer,
57 typename iterator_traits<_Iter>::reference>
58#endif
59{
60 _LIBCPP_SUPPRESS_DEPRECATED_POP
61
62private:
63#ifndef _LIBCPP_ABI_NO_ITERATOR_BASES
64 _Iter __t_; // no longer used as of LWG #2360, not removed due to ABI break
65#endif
66
67#if _LIBCPP_STD_VER >= 20
68 static_assert(__has_bidirectional_iterator_category<_Iter>::value || bidirectional_iterator<_Iter>,
69 "reverse_iterator<It> requires It to be a bidirectional iterator.");
70#endif // _LIBCPP_STD_VER >= 20
71
72protected:
73 _Iter current;
74
75public:
76 using iterator_type = _Iter;
77
78 using iterator_category =
79 _If<__has_random_access_iterator_category<_Iter>::value,
80 random_access_iterator_tag,
81 typename iterator_traits<_Iter>::iterator_category>;
82 using pointer = typename iterator_traits<_Iter>::pointer;
83#if _LIBCPP_STD_VER >= 20
84 using iterator_concept = _If<random_access_iterator<_Iter>, random_access_iterator_tag, bidirectional_iterator_tag>;
85 using value_type = iter_value_t<_Iter>;
86 using difference_type = iter_difference_t<_Iter>;
87 using reference = iter_reference_t<_Iter>;
88#else
89 using value_type = typename iterator_traits<_Iter>::value_type;
90 using difference_type = typename iterator_traits<_Iter>::difference_type;
91 using reference = typename iterator_traits<_Iter>::reference;
92#endif
93
94#ifndef _LIBCPP_ABI_NO_ITERATOR_BASES
95 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator() : __t_(), current() {}
96
97 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 explicit reverse_iterator(_Iter __x) : __t_(__x), current(__x) {}
98
99 template <class _Up, __enable_if_t<!is_same<_Up, _Iter>::value && is_convertible<_Up const&, _Iter>::value, int> = 0>
100 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator(const reverse_iterator<_Up>& __u)
101 : __t_(__u.base()), current(__u.base()) {}
102
103 template <class _Up,
104 __enable_if_t<!is_same<_Up, _Iter>::value && is_convertible<_Up const&, _Iter>::value &&
105 is_assignable<_Iter&, _Up const&>::value,
106 int> = 0>
107 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator& operator=(const reverse_iterator<_Up>& __u) {
108 __t_ = current = __u.base();
109 return *this;
110 }
111#else
112 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator() : current() {}
113
114 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 explicit reverse_iterator(_Iter __x) : current(__x) {}
115
116 template <class _Up, __enable_if_t<!is_same<_Up, _Iter>::value && is_convertible<_Up const&, _Iter>::value, int> = 0>
117 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator(const reverse_iterator<_Up>& __u)
118 : current(__u.base()) {}
119
120 template <class _Up,
121 __enable_if_t<!is_same<_Up, _Iter>::value && is_convertible<_Up const&, _Iter>::value &&
122 is_assignable<_Iter&, _Up const&>::value,
123 int> = 0>
124 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator& operator=(const reverse_iterator<_Up>& __u) {
125 current = __u.base();
126 return *this;
127 }
128#endif
129 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 _Iter base() const { return current; }
130 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reference operator*() const {
131 _Iter __tmp = current;
132 return *--__tmp;
133 }
134
135#if _LIBCPP_STD_VER >= 20
136 _LIBCPP_HIDE_FROM_ABI constexpr pointer operator->() const
137 requires is_pointer_v<_Iter> || requires(const _Iter __i) { __i.operator->(); }
138 {
139 _Iter __tmp = current;
140 --__tmp;
141 if constexpr (is_pointer_v<_Iter>) {
142 return __tmp;
143 } else {
144 return __tmp.operator->();
145 }
146 }
147#else
148 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 pointer operator->() const { return std::addressof(operator*()); }
149#endif // _LIBCPP_STD_VER >= 20
150
151 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator& operator++() {
152 --current;
153 return *this;
154 }
155 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator operator++(int) {
156 reverse_iterator __tmp(*this);
157 --current;
158 return __tmp;
159 }
160 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator& operator--() {
161 ++current;
162 return *this;
163 }
164 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator operator--(int) {
165 reverse_iterator __tmp(*this);
166 ++current;
167 return __tmp;
168 }
169 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator operator+(difference_type __n) const {
170 return reverse_iterator(current - __n);
171 }
172 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator& operator+=(difference_type __n) {
173 current -= __n;
174 return *this;
175 }
176 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator operator-(difference_type __n) const {
177 return reverse_iterator(current + __n);
178 }
179 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator& operator-=(difference_type __n) {
180 current += __n;
181 return *this;
182 }
183 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reference operator[](difference_type __n) const {
184 return *(*this + __n);
185 }
186
187#if _LIBCPP_STD_VER >= 20
188 _LIBCPP_HIDE_FROM_ABI friend constexpr iter_rvalue_reference_t<_Iter> iter_move(const reverse_iterator& __i) noexcept(
189 is_nothrow_copy_constructible_v<_Iter> && noexcept(ranges::iter_move(--std::declval<_Iter&>()))) {
190 auto __tmp = __i.base();
191 return ranges::iter_move(--__tmp);
192 }
193
194 template <indirectly_swappable<_Iter> _Iter2>
195 _LIBCPP_HIDE_FROM_ABI friend constexpr void
196 iter_swap(const reverse_iterator& __x, const reverse_iterator<_Iter2>& __y) noexcept(
197 is_nothrow_copy_constructible_v<_Iter> && is_nothrow_copy_constructible_v<_Iter2> &&
198 noexcept(ranges::iter_swap(--std::declval<_Iter&>(), --std::declval<_Iter2&>()))) {
199 auto __xtmp = __x.base();
200 auto __ytmp = __y.base();
201 ranges::iter_swap(--__xtmp, --__ytmp);
202 }
203#endif // _LIBCPP_STD_VER >= 20
204};
205
206template <class _Iter1, class _Iter2>
207inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 bool
208operator==(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
209#if _LIBCPP_STD_VER >= 20
210 requires requires {
211 { __x.base() == __y.base() } -> convertible_to<bool>;
212 }
213#endif // _LIBCPP_STD_VER >= 20
214{
215 return __x.base() == __y.base();
216}
217
218template <class _Iter1, class _Iter2>
219inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 bool
220operator<(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
221#if _LIBCPP_STD_VER >= 20
222 requires requires {
223 { __x.base() > __y.base() } -> convertible_to<bool>;
224 }
225#endif // _LIBCPP_STD_VER >= 20
226{
227 return __x.base() > __y.base();
228}
229
230template <class _Iter1, class _Iter2>
231inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 bool
232operator!=(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
233#if _LIBCPP_STD_VER >= 20
234 requires requires {
235 { __x.base() != __y.base() } -> convertible_to<bool>;
236 }
237#endif // _LIBCPP_STD_VER >= 20
238{
239 return __x.base() != __y.base();
240}
241
242template <class _Iter1, class _Iter2>
243inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 bool
244operator>(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
245#if _LIBCPP_STD_VER >= 20
246 requires requires {
247 { __x.base() < __y.base() } -> convertible_to<bool>;
248 }
249#endif // _LIBCPP_STD_VER >= 20
250{
251 return __x.base() < __y.base();
252}
253
254template <class _Iter1, class _Iter2>
255inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 bool
256operator>=(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
257#if _LIBCPP_STD_VER >= 20
258 requires requires {
259 { __x.base() <= __y.base() } -> convertible_to<bool>;
260 }
261#endif // _LIBCPP_STD_VER >= 20
262{
263 return __x.base() <= __y.base();
264}
265
266template <class _Iter1, class _Iter2>
267inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 bool
268operator<=(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
269#if _LIBCPP_STD_VER >= 20
270 requires requires {
271 { __x.base() >= __y.base() } -> convertible_to<bool>;
272 }
273#endif // _LIBCPP_STD_VER >= 20
274{
275 return __x.base() >= __y.base();
276}
277
278#if _LIBCPP_STD_VER >= 20
279template <class _Iter1, three_way_comparable_with<_Iter1> _Iter2>
280_LIBCPP_HIDE_FROM_ABI constexpr compare_three_way_result_t<_Iter1, _Iter2>
281operator<=>(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y) {
282 return __y.base() <=> __x.base();
283}
284#endif // _LIBCPP_STD_VER >= 20
285
286#ifndef _LIBCPP_CXX03_LANG
287template <class _Iter1, class _Iter2>
288inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 auto
289operator-(const reverse_iterator<_Iter1>& __x,
290 const reverse_iterator<_Iter2>& __y) -> decltype(__y.base() - __x.base()) {
291 return __y.base() - __x.base();
292}
293#else
294template <class _Iter1, class _Iter2>
295inline _LIBCPP_HIDE_FROM_ABI typename reverse_iterator<_Iter1>::difference_type
296operator-(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y) {
297 return __y.base() - __x.base();
298}
299#endif
300
301template <class _Iter>
302inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator<_Iter>
303operator+(typename reverse_iterator<_Iter>::difference_type __n, const reverse_iterator<_Iter>& __x) {
304 return reverse_iterator<_Iter>(__x.base() - __n);
305}
306
307#if _LIBCPP_STD_VER >= 20
308template <class _Iter1, class _Iter2>
309 requires(!sized_sentinel_for<_Iter1, _Iter2>)
310inline constexpr bool disable_sized_sentinel_for<reverse_iterator<_Iter1>, reverse_iterator<_Iter2>> = true;
311#endif // _LIBCPP_STD_VER >= 20
312
313#if _LIBCPP_STD_VER >= 14
314template <class _Iter>
315inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator<_Iter> make_reverse_iterator(_Iter __i) {
316 return reverse_iterator<_Iter>(__i);
317}
318#endif
319
320#if _LIBCPP_STD_VER >= 20
321template <ranges::bidirectional_range _Range>
322_LIBCPP_HIDE_FROM_ABI constexpr ranges::subrange<reverse_iterator<ranges::iterator_t<_Range>>,
323 reverse_iterator<ranges::iterator_t<_Range>>>
324__reverse_range(_Range&& __range) {
325 auto __first = ranges::begin(__range);
326 return {std::make_reverse_iterator(ranges::next(__first, ranges::end(__range))), std::make_reverse_iterator(__first)};
327}
328#endif
329
330template <class _Iter, bool __b>
331struct __unwrap_iter_impl<reverse_iterator<reverse_iterator<_Iter> >, __b> {
332 using _UnwrappedIter _LIBCPP_NODEBUG = decltype(__unwrap_iter_impl<_Iter>::__unwrap(std::declval<_Iter>()));
333 using _ReverseWrapper _LIBCPP_NODEBUG = reverse_iterator<reverse_iterator<_Iter> >;
334
335 static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _ReverseWrapper
336 __rewrap(_ReverseWrapper __orig_iter, _UnwrappedIter __unwrapped_iter) {
337 return _ReverseWrapper(
338 reverse_iterator<_Iter>(__unwrap_iter_impl<_Iter>::__rewrap(__orig_iter.base().base(), __unwrapped_iter)));
339 }
340
341 static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _UnwrappedIter __unwrap(_ReverseWrapper __i) _NOEXCEPT {
342 return __unwrap_iter_impl<_Iter>::__unwrap(__i.base().base());
343 }
344};
345
346_LIBCPP_END_NAMESPACE_STD
347
348#endif // _LIBCPP___ITERATOR_REVERSE_ITERATOR_H
349

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source code of libcxx/include/__iterator/reverse_iterator.h