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 <__concepts/assignable.h>
15#include <__concepts/common_with.h>
16#include <__concepts/constructible.h>
17#include <__concepts/convertible_to.h>
18#include <__concepts/same_as.h>
19#include <__config>
20#include <__iterator/concepts.h>
21#include <__iterator/default_sentinel.h>
22#include <__iterator/incrementable_traits.h>
23#include <__iterator/iter_move.h>
24#include <__iterator/iter_swap.h>
25#include <__iterator/iterator_traits.h>
26#include <__iterator/readable_traits.h>
27#include <__memory/pointer_traits.h>
28#include <__type_traits/add_pointer.h>
29#include <__type_traits/conditional.h>
30#include <__utility/move.h>
31#include <compare>
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 decltype(auto) operator++(int) {
133    _LIBCPP_ASSERT_UNCATEGORIZED(__count_ > 0, "Iterator already at or past end.");
134    --__count_;
135#  ifndef _LIBCPP_HAS_NO_EXCEPTIONS
136    try {
137      return __current_++;
138    } catch (...) {
139      ++__count_;
140      throw;
141    }
142#  else
143    return __current_++;
144#  endif // _LIBCPP_HAS_NO_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 iter_rvalue_reference_t<_Iter>
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
290