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
49template <class _Iter>
50class reverse_iterator
51 : public __iterator_base<reverse_iterator<_Iter>,
52 typename iterator_traits<_Iter>::iterator_category,
53 typename iterator_traits<_Iter>::value_type,
54 typename iterator_traits<_Iter>::difference_type,
55 typename iterator_traits<_Iter>::pointer,
56 typename iterator_traits<_Iter>::reference> {
57private:
58#ifndef _LIBCPP_ABI_NO_REVERSE_ITERATOR_SECOND_MEMBER
59 _Iter __t_; // no longer used as of LWG #2360, not removed due to ABI break
60#endif
61
62#if _LIBCPP_STD_VER >= 20
63 static_assert(__has_bidirectional_iterator_category<_Iter>::value || bidirectional_iterator<_Iter>,
64 "reverse_iterator<It> requires It to be a bidirectional iterator.");
65#endif // _LIBCPP_STD_VER >= 20
66
67protected:
68 _Iter current;
69
70public:
71 using iterator_type = _Iter;
72
73 using iterator_category =
74 _If<__has_random_access_iterator_category<_Iter>::value,
75 random_access_iterator_tag,
76 typename iterator_traits<_Iter>::iterator_category>;
77 using pointer = typename iterator_traits<_Iter>::pointer;
78#if _LIBCPP_STD_VER >= 20
79 using iterator_concept = _If<random_access_iterator<_Iter>, random_access_iterator_tag, bidirectional_iterator_tag>;
80 using value_type = iter_value_t<_Iter>;
81 using difference_type = iter_difference_t<_Iter>;
82 using reference = iter_reference_t<_Iter>;
83#else
84 using value_type = typename iterator_traits<_Iter>::value_type;
85 using difference_type = typename iterator_traits<_Iter>::difference_type;
86 using reference = typename iterator_traits<_Iter>::reference;
87#endif
88
89#ifndef _LIBCPP_ABI_NO_REVERSE_ITERATOR_SECOND_MEMBER
90 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator() : __t_(), current() {}
91
92 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 explicit reverse_iterator(_Iter __x) : __t_(__x), current(__x) {}
93
94 template <class _Up, __enable_if_t<!is_same<_Up, _Iter>::value && is_convertible<_Up const&, _Iter>::value, int> = 0>
95 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator(const reverse_iterator<_Up>& __u)
96 : __t_(__u.base()), current(__u.base()) {}
97
98 template <class _Up,
99 __enable_if_t<!is_same<_Up, _Iter>::value && is_convertible<_Up const&, _Iter>::value &&
100 is_assignable<_Iter&, _Up const&>::value,
101 int> = 0>
102 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator& operator=(const reverse_iterator<_Up>& __u) {
103 __t_ = current = __u.base();
104 return *this;
105 }
106#else
107 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator() : current() {}
108
109 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 explicit reverse_iterator(_Iter __x) : current(__x) {}
110
111 template <class _Up, __enable_if_t<!is_same<_Up, _Iter>::value && is_convertible<_Up const&, _Iter>::value, int> = 0>
112 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator(const reverse_iterator<_Up>& __u)
113 : current(__u.base()) {}
114
115 template <class _Up,
116 __enable_if_t<!is_same<_Up, _Iter>::value && is_convertible<_Up const&, _Iter>::value &&
117 is_assignable<_Iter&, _Up const&>::value,
118 int> = 0>
119 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator& operator=(const reverse_iterator<_Up>& __u) {
120 current = __u.base();
121 return *this;
122 }
123#endif
124 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 _Iter base() const { return current; }
125 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reference operator*() const {
126 _Iter __tmp = current;
127 return *--__tmp;
128 }
129
130#if _LIBCPP_STD_VER >= 20
131 _LIBCPP_HIDE_FROM_ABI constexpr pointer operator->() const
132 requires is_pointer_v<_Iter> || requires(const _Iter __i) { __i.operator->(); }
133 {
134 _Iter __tmp = current;
135 --__tmp;
136 if constexpr (is_pointer_v<_Iter>) {
137 return __tmp;
138 } else {
139 return __tmp.operator->();
140 }
141 }
142#else
143 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 pointer operator->() const { return std::addressof(operator*()); }
144#endif // _LIBCPP_STD_VER >= 20
145
146 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator& operator++() {
147 --current;
148 return *this;
149 }
150 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator operator++(int) {
151 reverse_iterator __tmp(*this);
152 --current;
153 return __tmp;
154 }
155 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator& operator--() {
156 ++current;
157 return *this;
158 }
159 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator operator--(int) {
160 reverse_iterator __tmp(*this);
161 ++current;
162 return __tmp;
163 }
164 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator operator+(difference_type __n) const {
165 return reverse_iterator(current - __n);
166 }
167 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator& operator+=(difference_type __n) {
168 current -= __n;
169 return *this;
170 }
171 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator operator-(difference_type __n) const {
172 return reverse_iterator(current + __n);
173 }
174 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator& operator-=(difference_type __n) {
175 current += __n;
176 return *this;
177 }
178 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reference operator[](difference_type __n) const {
179 return *(*this + __n);
180 }
181
182#if _LIBCPP_STD_VER >= 20
183 _LIBCPP_HIDE_FROM_ABI friend constexpr iter_rvalue_reference_t<_Iter> iter_move(const reverse_iterator& __i) noexcept(
184 is_nothrow_copy_constructible_v<_Iter> && noexcept(ranges::iter_move(--std::declval<_Iter&>()))) {
185 auto __tmp = __i.base();
186 return ranges::iter_move(--__tmp);
187 }
188
189 template <indirectly_swappable<_Iter> _Iter2>
190 _LIBCPP_HIDE_FROM_ABI friend constexpr void
191 iter_swap(const reverse_iterator& __x, const reverse_iterator<_Iter2>& __y) noexcept(
192 is_nothrow_copy_constructible_v<_Iter> && is_nothrow_copy_constructible_v<_Iter2> &&
193 noexcept(ranges::iter_swap(--std::declval<_Iter&>(), --std::declval<_Iter2&>()))) {
194 auto __xtmp = __x.base();
195 auto __ytmp = __y.base();
196 ranges::iter_swap(--__xtmp, --__ytmp);
197 }
198#endif // _LIBCPP_STD_VER >= 20
199};
200
201template <class _Iter1, class _Iter2>
202inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 bool
203operator==(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
204#if _LIBCPP_STD_VER >= 20
205 requires requires {
206 { __x.base() == __y.base() } -> convertible_to<bool>;
207 }
208#endif // _LIBCPP_STD_VER >= 20
209{
210 return __x.base() == __y.base();
211}
212
213template <class _Iter1, class _Iter2>
214inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 bool
215operator<(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
216#if _LIBCPP_STD_VER >= 20
217 requires requires {
218 { __x.base() > __y.base() } -> convertible_to<bool>;
219 }
220#endif // _LIBCPP_STD_VER >= 20
221{
222 return __x.base() > __y.base();
223}
224
225template <class _Iter1, class _Iter2>
226inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 bool
227operator!=(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
228#if _LIBCPP_STD_VER >= 20
229 requires requires {
230 { __x.base() != __y.base() } -> convertible_to<bool>;
231 }
232#endif // _LIBCPP_STD_VER >= 20
233{
234 return __x.base() != __y.base();
235}
236
237template <class _Iter1, class _Iter2>
238inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 bool
239operator>(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
240#if _LIBCPP_STD_VER >= 20
241 requires requires {
242 { __x.base() < __y.base() } -> convertible_to<bool>;
243 }
244#endif // _LIBCPP_STD_VER >= 20
245{
246 return __x.base() < __y.base();
247}
248
249template <class _Iter1, class _Iter2>
250inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 bool
251operator>=(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
252#if _LIBCPP_STD_VER >= 20
253 requires requires {
254 { __x.base() <= __y.base() } -> convertible_to<bool>;
255 }
256#endif // _LIBCPP_STD_VER >= 20
257{
258 return __x.base() <= __y.base();
259}
260
261template <class _Iter1, class _Iter2>
262inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 bool
263operator<=(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
264#if _LIBCPP_STD_VER >= 20
265 requires requires {
266 { __x.base() >= __y.base() } -> convertible_to<bool>;
267 }
268#endif // _LIBCPP_STD_VER >= 20
269{
270 return __x.base() >= __y.base();
271}
272
273#if _LIBCPP_STD_VER >= 20
274template <class _Iter1, three_way_comparable_with<_Iter1> _Iter2>
275_LIBCPP_HIDE_FROM_ABI constexpr compare_three_way_result_t<_Iter1, _Iter2>
276operator<=>(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y) {
277 return __y.base() <=> __x.base();
278}
279#endif // _LIBCPP_STD_VER >= 20
280
281#ifndef _LIBCPP_CXX03_LANG
282template <class _Iter1, class _Iter2>
283inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 auto
284operator-(const reverse_iterator<_Iter1>& __x,
285 const reverse_iterator<_Iter2>& __y) -> decltype(__y.base() - __x.base()) {
286 return __y.base() - __x.base();
287}
288#else
289template <class _Iter1, class _Iter2>
290inline _LIBCPP_HIDE_FROM_ABI typename reverse_iterator<_Iter1>::difference_type
291operator-(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y) {
292 return __y.base() - __x.base();
293}
294#endif
295
296template <class _Iter>
297inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator<_Iter>
298operator+(typename reverse_iterator<_Iter>::difference_type __n, const reverse_iterator<_Iter>& __x) {
299 return reverse_iterator<_Iter>(__x.base() - __n);
300}
301
302#if _LIBCPP_STD_VER >= 20
303template <class _Iter1, class _Iter2>
304 requires(!sized_sentinel_for<_Iter1, _Iter2>)
305inline constexpr bool disable_sized_sentinel_for<reverse_iterator<_Iter1>, reverse_iterator<_Iter2>> = true;
306#endif // _LIBCPP_STD_VER >= 20
307
308#if _LIBCPP_STD_VER >= 14
309template <class _Iter>
310inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 reverse_iterator<_Iter> make_reverse_iterator(_Iter __i) {
311 return reverse_iterator<_Iter>(__i);
312}
313#endif
314
315#if _LIBCPP_STD_VER >= 20
316template <ranges::bidirectional_range _Range>
317_LIBCPP_HIDE_FROM_ABI constexpr ranges::subrange<reverse_iterator<ranges::iterator_t<_Range>>,
318 reverse_iterator<ranges::iterator_t<_Range>>>
319__reverse_range(_Range&& __range) {
320 auto __first = ranges::begin(__range);
321 return {std::make_reverse_iterator(ranges::next(__first, ranges::end(__range))), std::make_reverse_iterator(__first)};
322}
323#endif
324
325template <class _Iter, bool __b>
326struct __unwrap_iter_impl<reverse_iterator<reverse_iterator<_Iter> >, __b> {
327 using _UnwrappedIter _LIBCPP_NODEBUG = decltype(__unwrap_iter_impl<_Iter>::__unwrap(std::declval<_Iter>()));
328 using _ReverseWrapper _LIBCPP_NODEBUG = reverse_iterator<reverse_iterator<_Iter> >;
329
330 static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _ReverseWrapper
331 __rewrap(_ReverseWrapper __orig_iter, _UnwrappedIter __unwrapped_iter) {
332 return _ReverseWrapper(
333 reverse_iterator<_Iter>(__unwrap_iter_impl<_Iter>::__rewrap(__orig_iter.base().base(), __unwrapped_iter)));
334 }
335
336 static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _UnwrappedIter __unwrap(_ReverseWrapper __i) _NOEXCEPT {
337 return __unwrap_iter_impl<_Iter>::__unwrap(__i.base().base());
338 }
339};
340
341_LIBCPP_END_NAMESPACE_STD
342
343#endif // _LIBCPP___ITERATOR_REVERSE_ITERATOR_H
344