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