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 <__iterator/prev.h>
25 #include <__iterator/readable_traits.h>
26 #include <__memory/addressof.h>
27 #include <__utility/move.h>
28 #include <type_traits>
29 
30 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
31 #  pragma GCC system_header
32 #endif
33 
34 _LIBCPP_BEGIN_NAMESPACE_STD
35 
36 _LIBCPP_SUPPRESS_DEPRECATED_PUSH
37 template <class _Iter>
38 class _LIBCPP_TEMPLATE_VIS reverse_iterator
39 #if _LIBCPP_STD_VER <= 14 || !defined(_LIBCPP_ABI_NO_ITERATOR_BASES)
40     : public iterator<typename iterator_traits<_Iter>::iterator_category,
41                       typename iterator_traits<_Iter>::value_type,
42                       typename iterator_traits<_Iter>::difference_type,
43                       typename iterator_traits<_Iter>::pointer,
44                       typename iterator_traits<_Iter>::reference>
45 #endif
46 {
47 _LIBCPP_SUPPRESS_DEPRECATED_POP
48 private:
49 #ifndef _LIBCPP_ABI_NO_ITERATOR_BASES
50     _Iter __t; // no longer used as of LWG #2360, not removed due to ABI break
51 #endif
52 
53 #if _LIBCPP_STD_VER > 17
54     static_assert(__is_cpp17_bidirectional_iterator<_Iter>::value || bidirectional_iterator<_Iter>,
55         "reverse_iterator<It> requires It to be a bidirectional iterator.");
56 #endif // _LIBCPP_STD_VER > 17
57 
58 protected:
59     _Iter current;
60 public:
61     using iterator_type = _Iter;
62 
63     using iterator_category = _If<__is_cpp17_random_access_iterator<_Iter>::value,
64                                   random_access_iterator_tag,
65                                   typename iterator_traits<_Iter>::iterator_category>;
66     using pointer = typename iterator_traits<_Iter>::pointer;
67 #if _LIBCPP_STD_VER > 17
68     using iterator_concept = _If<__is_cpp17_random_access_iterator<_Iter>::value,
69                                   random_access_iterator_tag,
70                                   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_ITERATOR_BASES
81     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
82     reverse_iterator() : __t(), current() {}
83 
84     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
85     explicit reverse_iterator(_Iter __x) : __t(__x), current(__x) {}
86 
87     template <class _Up, class = __enable_if_t<
88         !is_same<_Up, _Iter>::value && is_convertible<_Up const&, _Iter>::value
89     > >
90     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
91     reverse_iterator(const reverse_iterator<_Up>& __u)
92         : __t(__u.base()), current(__u.base())
93     { }
94 
95     template <class _Up, class = __enable_if_t<
96         !is_same<_Up, _Iter>::value &&
97         is_convertible<_Up const&, _Iter>::value &&
98         is_assignable<_Iter&, _Up const&>::value
99     > >
100     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
101     reverse_iterator& operator=(const reverse_iterator<_Up>& __u) {
102         __t = current = __u.base();
103         return *this;
104     }
105 #else
106     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
107     reverse_iterator() : current() {}
108 
109     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
110     explicit reverse_iterator(_Iter __x) : current(__x) {}
111 
112     template <class _Up, class = __enable_if_t<
113         !is_same<_Up, _Iter>::value && is_convertible<_Up const&, _Iter>::value
114     > >
115     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
116     reverse_iterator(const reverse_iterator<_Up>& __u)
117         : current(__u.base())
118     { }
119 
120     template <class _Up, class = __enable_if_t<
121         !is_same<_Up, _Iter>::value &&
122         is_convertible<_Up const&, _Iter>::value &&
123         is_assignable<_Iter&, _Up const&>::value
124     > >
125     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
126     reverse_iterator& operator=(const reverse_iterator<_Up>& __u) {
127         current = __u.base();
128         return *this;
129     }
130 #endif
131     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
132     _Iter base() const {return current;}
133     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
134     reference operator*() const {_Iter __tmp = current; return *--__tmp;}
135 
136 #if _LIBCPP_STD_VER > 17
137     _LIBCPP_INLINE_VISIBILITY
138     constexpr pointer operator->() const
139       requires is_pointer_v<_Iter> || requires(const _Iter i) { i.operator->(); }
140     {
141       if constexpr (is_pointer_v<_Iter>) {
142         return std::prev(current);
143       } else {
144         return std::prev(current).operator->();
145       }
146     }
147 #else
148     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
149     pointer operator->() const {
150       return std::addressof(operator*());
151     }
152 #endif // _LIBCPP_STD_VER > 17
153 
154     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
155     reverse_iterator& operator++() {--current; return *this;}
156     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
157     reverse_iterator operator++(int) {reverse_iterator __tmp(*this); --current; return __tmp;}
158     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
159     reverse_iterator& operator--() {++current; return *this;}
160     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
161     reverse_iterator operator--(int) {reverse_iterator __tmp(*this); ++current; return __tmp;}
162     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
163     reverse_iterator operator+(difference_type __n) const {return reverse_iterator(current - __n);}
164     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
165     reverse_iterator& operator+=(difference_type __n) {current -= __n; return *this;}
166     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
167     reverse_iterator operator-(difference_type __n) const {return reverse_iterator(current + __n);}
168     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
169     reverse_iterator& operator-=(difference_type __n) {current += __n; return *this;}
170     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
171     reference operator[](difference_type __n) const {return *(*this + __n);}
172 
173 #if _LIBCPP_STD_VER > 17
174     _LIBCPP_HIDE_FROM_ABI friend constexpr
175     iter_rvalue_reference_t<_Iter> iter_move(const reverse_iterator& __i)
176       noexcept(is_nothrow_copy_constructible_v<_Iter> &&
177           noexcept(ranges::iter_move(--declval<_Iter&>()))) {
178       auto __tmp = __i.base();
179       return ranges::iter_move(--__tmp);
180     }
181 
182     template <indirectly_swappable<_Iter> _Iter2>
183     _LIBCPP_HIDE_FROM_ABI friend constexpr
184     void iter_swap(const reverse_iterator& __x, const reverse_iterator<_Iter2>& __y)
185       noexcept(is_nothrow_copy_constructible_v<_Iter> &&
186           is_nothrow_copy_constructible_v<_Iter2> &&
187           noexcept(ranges::iter_swap(--declval<_Iter&>(), --declval<_Iter2&>()))) {
188       auto __xtmp = __x.base();
189       auto __ytmp = __y.base();
190       ranges::iter_swap(--__xtmp, --__ytmp);
191     }
192 #endif // _LIBCPP_STD_VER > 17
193 };
194 
195 template <class _Iter1, class _Iter2>
196 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
197 bool
198 operator==(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
199 #if _LIBCPP_STD_VER > 17
200     requires requires {
201       { __x.base() == __y.base() } -> convertible_to<bool>;
202     }
203 #endif // _LIBCPP_STD_VER > 17
204 {
205     return __x.base() == __y.base();
206 }
207 
208 template <class _Iter1, class _Iter2>
209 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
210 bool
211 operator<(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
212 #if _LIBCPP_STD_VER > 17
213     requires requires {
214         { __x.base() > __y.base() } -> convertible_to<bool>;
215       }
216 #endif // _LIBCPP_STD_VER > 17
217 {
218     return __x.base() > __y.base();
219 }
220 
221 template <class _Iter1, class _Iter2>
222 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
223 bool
224 operator!=(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
225 #if _LIBCPP_STD_VER > 17
226     requires requires {
227       { __x.base() != __y.base() } -> convertible_to<bool>;
228     }
229 #endif // _LIBCPP_STD_VER > 17
230 {
231     return __x.base() != __y.base();
232 }
233 
234 template <class _Iter1, class _Iter2>
235 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
236 bool
237 operator>(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
238 #if _LIBCPP_STD_VER > 17
239     requires requires {
240         { __x.base() < __y.base() } -> convertible_to<bool>;
241       }
242 #endif // _LIBCPP_STD_VER > 17
243 {
244     return __x.base() < __y.base();
245 }
246 
247 template <class _Iter1, class _Iter2>
248 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
249 bool
250 operator>=(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
251 #if _LIBCPP_STD_VER > 17
252     requires requires {
253         { __x.base() <= __y.base() } -> convertible_to<bool>;
254       }
255 #endif // _LIBCPP_STD_VER > 17
256 {
257     return __x.base() <= __y.base();
258 }
259 
260 template <class _Iter1, class _Iter2>
261 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
262 bool
263 operator<=(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
264 #if _LIBCPP_STD_VER > 17
265     requires requires {
266         { __x.base() >= __y.base() } -> convertible_to<bool>;
267       }
268 #endif // _LIBCPP_STD_VER > 17
269 {
270     return __x.base() >= __y.base();
271 }
272 
273 #if _LIBCPP_STD_VER > 17
274 template <class _Iter1, three_way_comparable_with<_Iter1> _Iter2>
275 _LIBCPP_HIDE_FROM_ABI constexpr
276 compare_three_way_result_t<_Iter1, _Iter2>
277 operator<=>(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
278 {
279     return __y.base() <=> __x.base();
280 }
281 #endif // _LIBCPP_STD_VER > 17
282 
283 #ifndef _LIBCPP_CXX03_LANG
284 template <class _Iter1, class _Iter2>
285 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
286 auto
287 operator-(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
288 -> decltype(__y.base() - __x.base())
289 {
290     return __y.base() - __x.base();
291 }
292 #else
293 template <class _Iter1, class _Iter2>
294 inline _LIBCPP_INLINE_VISIBILITY
295 typename reverse_iterator<_Iter1>::difference_type
296 operator-(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
297 {
298     return __y.base() - __x.base();
299 }
300 #endif
301 
302 template <class _Iter>
303 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
304 reverse_iterator<_Iter>
305 operator+(typename reverse_iterator<_Iter>::difference_type __n, const reverse_iterator<_Iter>& __x)
306 {
307     return reverse_iterator<_Iter>(__x.base() - __n);
308 }
309 
310 #if _LIBCPP_STD_VER > 17
311 template <class _Iter1, class _Iter2>
312   requires (!sized_sentinel_for<_Iter1, _Iter2>)
313 inline constexpr bool disable_sized_sentinel_for<reverse_iterator<_Iter1>, reverse_iterator<_Iter2>> = true;
314 #endif // _LIBCPP_STD_VER > 17
315 
316 #if _LIBCPP_STD_VER > 11
317 template <class _Iter>
318 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
319 reverse_iterator<_Iter> make_reverse_iterator(_Iter __i)
320 {
321     return reverse_iterator<_Iter>(__i);
322 }
323 #endif
324 
325 template <class _Iter>
326 using _ReverseWrapper = reverse_iterator<reverse_iterator<_Iter> >;
327 
328 template <class _Iter, bool __b>
329 struct __unwrap_iter_impl<_ReverseWrapper<_Iter>, __b> {
330   static _LIBCPP_CONSTEXPR decltype(std::__unwrap_iter(std::declval<_Iter>()))
331   __apply(_ReverseWrapper<_Iter> __i) _NOEXCEPT {
332     return std::__unwrap_iter(__i.base().base());
333   }
334 };
335 
336 template <class _OrigIter, class _UnwrappedIter>
337 struct __rewrap_iter_impl<_ReverseWrapper<_OrigIter>, _UnwrappedIter> {
338   template <class _Iter>
339   struct _ReverseWrapperCount {
340     static _LIBCPP_CONSTEXPR const size_t value = 1;
341   };
342 
343   template <class _Iter>
344   struct _ReverseWrapperCount<_ReverseWrapper<_Iter> > {
345     static _LIBCPP_CONSTEXPR const size_t value = 1 + _ReverseWrapperCount<_Iter>::value;
346   };
347 
348   template <size_t _RewrapCount, class _OIter, class _UIter, __enable_if_t<_RewrapCount != 0, int> = 0>
349   _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR _ReverseWrapper<_OIter> __rewrap(_ReverseWrapper<_OIter> __iter1,
350                                                                                   _UIter __iter2) {
351     return _ReverseWrapper<_OIter>(
352         reverse_iterator<_OIter>(__rewrap<_RewrapCount - 1>(__iter1.base().base(), __iter2)));
353   }
354 
355   template <size_t _RewrapCount, class _OIter, class _UIter, __enable_if_t<_RewrapCount == 0, int> = 0>
356   _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR decltype(std::__rewrap_iter(std::declval<_OIter>(),
357                                                                              std::declval<_UIter>()))
358   __rewrap(_OIter __iter1, _UIter __iter2) {
359     return std::__rewrap_iter(__iter1, __iter2);
360   }
361 
362   _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR _ReverseWrapper<_OrigIter> __apply(_ReverseWrapper<_OrigIter> __iter1,
363                                                                                     _UnwrappedIter __iter2) {
364     return __rewrap<_ReverseWrapperCount<_OrigIter>::value>(__iter1, __iter2);
365   }
366 };
367 
368 _LIBCPP_END_NAMESPACE_STD
369 
370 #endif // _LIBCPP___ITERATOR_REVERSE_ITERATOR_H
371