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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_COUNTED_ITERATOR_H
11#define _LIBCPP___ITERATOR_COUNTED_ITERATOR_H
12
13#include <__assert>
14#include <__compare/ordering.h>
15#include <__concepts/assignable.h>
16#include <__concepts/common_with.h>
17#include <__concepts/constructible.h>
18#include <__concepts/convertible_to.h>
19#include <__concepts/same_as.h>
20#include <__config>
21#include <__iterator/concepts.h>
22#include <__iterator/default_sentinel.h>
23#include <__iterator/incrementable_traits.h>
24#include <__iterator/iter_move.h>
25#include <__iterator/iter_swap.h>
26#include <__iterator/iterator_traits.h>
27#include <__iterator/readable_traits.h>
28#include <__memory/pointer_traits.h>
29#include <__type_traits/add_pointer.h>
30#include <__type_traits/conditional.h>
31#include <__utility/move.h>
32
33#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
34# pragma GCC system_header
35#endif
36
37_LIBCPP_PUSH_MACROS
38#include <__undef_macros>
39
40_LIBCPP_BEGIN_NAMESPACE_STD
41
42#if _LIBCPP_STD_VER >= 20
43
44template <class>
45struct __counted_iterator_concept {};
46
47template <class _Iter>
48 requires requires { typename _Iter::iterator_concept; }
49struct __counted_iterator_concept<_Iter> {
50 using iterator_concept = typename _Iter::iterator_concept;
51};
52
53template <class>
54struct __counted_iterator_category {};
55
56template <class _Iter>
57 requires requires { typename _Iter::iterator_category; }
58struct __counted_iterator_category<_Iter> {
59 using iterator_category = typename _Iter::iterator_category;
60};
61
62template <class>
63struct __counted_iterator_value_type {};
64
65template <indirectly_readable _Iter>
66struct __counted_iterator_value_type<_Iter> {
67 using value_type = iter_value_t<_Iter>;
68};
69
70template <input_or_output_iterator _Iter>
71class counted_iterator
72 : public __counted_iterator_concept<_Iter>,
73 public __counted_iterator_category<_Iter>,
74 public __counted_iterator_value_type<_Iter> {
75public:
76 using iterator_type = _Iter;
77 using difference_type = iter_difference_t<_Iter>;
78
79 _LIBCPP_HIDE_FROM_ABI constexpr counted_iterator()
80 requires default_initializable<_Iter>
81 = default;
82
83 _LIBCPP_HIDE_FROM_ABI constexpr counted_iterator(_Iter __iter, iter_difference_t<_Iter> __n)
84 : __current_(std::move(__iter)), __count_(__n) {
85 _LIBCPP_ASSERT_UNCATEGORIZED(__n >= 0, "__n must not be negative.");
86 }
87
88 template <class _I2>
89 requires convertible_to<const _I2&, _Iter>
90 _LIBCPP_HIDE_FROM_ABI constexpr counted_iterator(const counted_iterator<_I2>& __other)
91 : __current_(__other.__current_), __count_(__other.__count_) {}
92
93 template <class _I2>
94 requires assignable_from<_Iter&, const _I2&>
95 _LIBCPP_HIDE_FROM_ABI constexpr counted_iterator& operator=(const counted_iterator<_I2>& __other) {
96 __current_ = __other.__current_;
97 __count_ = __other.__count_;
98 return *this;
99 }
100
101 _LIBCPP_HIDE_FROM_ABI constexpr const _Iter& base() const& noexcept { return __current_; }
102
103 _LIBCPP_HIDE_FROM_ABI constexpr _Iter base() && { return std::move(__current_); }
104
105 _LIBCPP_HIDE_FROM_ABI constexpr iter_difference_t<_Iter> count() const noexcept { return __count_; }
106
107 _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) operator*() {
108 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__count_ > 0, "Iterator is equal to or past end.");
109 return *__current_;
110 }
111
112 _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) operator*() const
113 requires __dereferenceable<const _Iter>
114 {
115 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__count_ > 0, "Iterator is equal to or past end.");
116 return *__current_;
117 }
118
119 _LIBCPP_HIDE_FROM_ABI constexpr auto operator->() const noexcept
120 requires contiguous_iterator<_Iter>
121 {
122 return std::to_address(__current_);
123 }
124
125 _LIBCPP_HIDE_FROM_ABI constexpr counted_iterator& operator++() {
126 _LIBCPP_ASSERT_UNCATEGORIZED(__count_ > 0, "Iterator already at or past end.");
127 ++__current_;
128 --__count_;
129 return *this;
130 }
131
132 _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) operator++(int) {
133 _LIBCPP_ASSERT_UNCATEGORIZED(__count_ > 0, "Iterator already at or past end.");
134 --__count_;
135# if _LIBCPP_HAS_EXCEPTIONS
136 try {
137 return __current_++;
138 } catch (...) {
139 ++__count_;
140 throw;
141 }
142# else
143 return __current_++;
144# endif // _LIBCPP_HAS_EXCEPTIONS
145 }
146
147 _LIBCPP_HIDE_FROM_ABI constexpr counted_iterator operator++(int)
148 requires forward_iterator<_Iter>
149 {
150 _LIBCPP_ASSERT_UNCATEGORIZED(__count_ > 0, "Iterator already at or past end.");
151 counted_iterator __tmp = *this;
152 ++*this;
153 return __tmp;
154 }
155
156 _LIBCPP_HIDE_FROM_ABI constexpr counted_iterator& operator--()
157 requires bidirectional_iterator<_Iter>
158 {
159 --__current_;
160 ++__count_;
161 return *this;
162 }
163
164 _LIBCPP_HIDE_FROM_ABI constexpr counted_iterator operator--(int)
165 requires bidirectional_iterator<_Iter>
166 {
167 counted_iterator __tmp = *this;
168 --*this;
169 return __tmp;
170 }
171
172 _LIBCPP_HIDE_FROM_ABI constexpr counted_iterator operator+(iter_difference_t<_Iter> __n) const
173 requires random_access_iterator<_Iter>
174 {
175 return counted_iterator(__current_ + __n, __count_ - __n);
176 }
177
178 _LIBCPP_HIDE_FROM_ABI friend constexpr counted_iterator
179 operator+(iter_difference_t<_Iter> __n, const counted_iterator& __x)
180 requires random_access_iterator<_Iter>
181 {
182 return __x + __n;
183 }
184
185 _LIBCPP_HIDE_FROM_ABI constexpr counted_iterator& operator+=(iter_difference_t<_Iter> __n)
186 requires random_access_iterator<_Iter>
187 {
188 _LIBCPP_ASSERT_UNCATEGORIZED(__n <= __count_, "Cannot advance iterator past end.");
189 __current_ += __n;
190 __count_ -= __n;
191 return *this;
192 }
193
194 _LIBCPP_HIDE_FROM_ABI constexpr counted_iterator operator-(iter_difference_t<_Iter> __n) const
195 requires random_access_iterator<_Iter>
196 {
197 return counted_iterator(__current_ - __n, __count_ + __n);
198 }
199
200 template <common_with<_Iter> _I2>
201 _LIBCPP_HIDE_FROM_ABI friend constexpr iter_difference_t<_I2>
202 operator-(const counted_iterator& __lhs, const counted_iterator<_I2>& __rhs) {
203 return __rhs.__count_ - __lhs.__count_;
204 }
205
206 _LIBCPP_HIDE_FROM_ABI friend constexpr iter_difference_t<_Iter>
207 operator-(const counted_iterator& __lhs, default_sentinel_t) {
208 return -__lhs.__count_;
209 }
210
211 _LIBCPP_HIDE_FROM_ABI friend constexpr iter_difference_t<_Iter>
212 operator-(default_sentinel_t, const counted_iterator& __rhs) {
213 return __rhs.__count_;
214 }
215
216 _LIBCPP_HIDE_FROM_ABI constexpr counted_iterator& operator-=(iter_difference_t<_Iter> __n)
217 requires random_access_iterator<_Iter>
218 {
219 _LIBCPP_ASSERT_UNCATEGORIZED(
220 -__n <= __count_,
221 "Attempt to subtract too large of a size: "
222 "counted_iterator would be decremented before the "
223 "first element of its range.");
224 __current_ -= __n;
225 __count_ += __n;
226 return *this;
227 }
228
229 _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) operator[](iter_difference_t<_Iter> __n) const
230 requires random_access_iterator<_Iter>
231 {
232 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__n < __count_, "Subscript argument must be less than size.");
233 return __current_[__n];
234 }
235
236 template <common_with<_Iter> _I2>
237 _LIBCPP_HIDE_FROM_ABI friend constexpr bool
238 operator==(const counted_iterator& __lhs, const counted_iterator<_I2>& __rhs) {
239 return __lhs.__count_ == __rhs.__count_;
240 }
241
242 _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const counted_iterator& __lhs, default_sentinel_t) {
243 return __lhs.__count_ == 0;
244 }
245
246 template <common_with<_Iter> _I2>
247 _LIBCPP_HIDE_FROM_ABI friend constexpr strong_ordering
248 operator<=>(const counted_iterator& __lhs, const counted_iterator<_I2>& __rhs) {
249 return __rhs.__count_ <=> __lhs.__count_;
250 }
251
252 _LIBCPP_HIDE_FROM_ABI friend constexpr decltype(auto)
253 iter_move(const counted_iterator& __i) noexcept(noexcept(ranges::iter_move(__i.__current_)))
254 requires input_iterator<_Iter>
255 {
256 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__i.__count_ > 0, "Iterator must not be past end of range.");
257 return ranges::iter_move(__i.__current_);
258 }
259
260 template <indirectly_swappable<_Iter> _I2>
261 _LIBCPP_HIDE_FROM_ABI friend constexpr void
262 iter_swap(const counted_iterator& __x,
263 const counted_iterator<_I2>& __y) noexcept(noexcept(ranges::iter_swap(__x.__current_, __y.__current_))) {
264 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
265 __x.__count_ > 0 && __y.__count_ > 0, "Iterators must not be past end of range.");
266 return ranges::iter_swap(__x.__current_, __y.__current_);
267 }
268
269private:
270 _LIBCPP_NO_UNIQUE_ADDRESS _Iter __current_ = _Iter();
271 iter_difference_t<_Iter> __count_ = 0;
272 template <input_or_output_iterator _OtherIter>
273 friend class counted_iterator;
274};
275_LIBCPP_CTAD_SUPPORTED_FOR_TYPE(counted_iterator);
276
277template <input_iterator _Iter>
278 requires same_as<_ITER_TRAITS<_Iter>, iterator_traits<_Iter>>
279struct iterator_traits<counted_iterator<_Iter>> : iterator_traits<_Iter> {
280 using pointer = conditional_t<contiguous_iterator<_Iter>, add_pointer_t<iter_reference_t<_Iter>>, void>;
281};
282
283#endif // _LIBCPP_STD_VER >= 20
284
285_LIBCPP_END_NAMESPACE_STD
286
287_LIBCPP_POP_MACROS
288
289#endif // _LIBCPP___ITERATOR_COUNTED_ITERATOR_H