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_BEGIN_NAMESPACE_STD
38
39#if _LIBCPP_STD_VER > 17
40
41template<class>
42struct __counted_iterator_concept {};
43
44template<class _Iter>
45  requires requires { typename _Iter::iterator_concept; }
46struct __counted_iterator_concept<_Iter> {
47  using iterator_concept = typename _Iter::iterator_concept;
48};
49
50template<class>
51struct __counted_iterator_category {};
52
53template<class _Iter>
54  requires requires { typename _Iter::iterator_category; }
55struct __counted_iterator_category<_Iter> {
56  using iterator_category = typename _Iter::iterator_category;
57};
58
59template<class>
60struct __counted_iterator_value_type {};
61
62template<indirectly_readable _Iter>
63struct __counted_iterator_value_type<_Iter> {
64  using value_type = iter_value_t<_Iter>;
65};
66
67template<input_or_output_iterator _Iter>
68class counted_iterator
69  : public __counted_iterator_concept<_Iter>
70  , public __counted_iterator_category<_Iter>
71  , public __counted_iterator_value_type<_Iter>
72{
73public:
74  _LIBCPP_NO_UNIQUE_ADDRESS _Iter __current_ = _Iter();
75  iter_difference_t<_Iter> __count_ = 0;
76
77  using iterator_type = _Iter;
78  using difference_type = iter_difference_t<_Iter>;
79
80  _LIBCPP_HIDE_FROM_ABI
81  constexpr counted_iterator() requires default_initializable<_Iter> = default;
82
83  _LIBCPP_HIDE_FROM_ABI
84  constexpr counted_iterator(_Iter __iter, iter_difference_t<_Iter> __n)
85   : __current_(_VSTD::move(__iter)), __count_(__n) {
86    _LIBCPP_ASSERT(__n >= 0, "__n must not be negative.");
87  }
88
89  template<class _I2>
90    requires convertible_to<const _I2&, _Iter>
91  _LIBCPP_HIDE_FROM_ABI
92  constexpr counted_iterator(const counted_iterator<_I2>& __other)
93   : __current_(__other.__current_), __count_(__other.__count_) {}
94
95  template<class _I2>
96    requires assignable_from<_Iter&, const _I2&>
97  _LIBCPP_HIDE_FROM_ABI
98  constexpr counted_iterator& operator=(const counted_iterator<_I2>& __other) {
99    __current_ = __other.__current_;
100    __count_ = __other.__count_;
101    return *this;
102  }
103
104  _LIBCPP_HIDE_FROM_ABI
105  constexpr const _Iter& base() const& noexcept { return __current_; }
106
107  _LIBCPP_HIDE_FROM_ABI
108  constexpr _Iter base() && { return _VSTD::move(__current_); }
109
110  _LIBCPP_HIDE_FROM_ABI
111  constexpr iter_difference_t<_Iter> count() const noexcept { return __count_; }
112
113  _LIBCPP_HIDE_FROM_ABI
114  constexpr decltype(auto) operator*() {
115    _LIBCPP_ASSERT(__count_ > 0, "Iterator is equal to or past end.");
116    return *__current_;
117  }
118
119  _LIBCPP_HIDE_FROM_ABI
120  constexpr decltype(auto) operator*() const
121    requires __dereferenceable<const _Iter>
122  {
123    _LIBCPP_ASSERT(__count_ > 0, "Iterator is equal to or past end.");
124    return *__current_;
125  }
126
127  _LIBCPP_HIDE_FROM_ABI
128  constexpr auto operator->() const noexcept
129    requires contiguous_iterator<_Iter>
130  {
131    return _VSTD::to_address(__current_);
132  }
133
134  _LIBCPP_HIDE_FROM_ABI
135  constexpr counted_iterator& operator++() {
136    _LIBCPP_ASSERT(__count_ > 0, "Iterator already at or past end.");
137    ++__current_;
138    --__count_;
139    return *this;
140  }
141
142  _LIBCPP_HIDE_FROM_ABI
143  decltype(auto) operator++(int) {
144    _LIBCPP_ASSERT(__count_ > 0, "Iterator already at or past end.");
145    --__count_;
146#ifndef _LIBCPP_NO_EXCEPTIONS
147    try { return __current_++; }
148    catch(...) { ++__count_; throw; }
149#else
150    return __current_++;
151#endif // _LIBCPP_NO_EXCEPTIONS
152  }
153
154  _LIBCPP_HIDE_FROM_ABI
155  constexpr counted_iterator operator++(int)
156    requires forward_iterator<_Iter>
157  {
158    _LIBCPP_ASSERT(__count_ > 0, "Iterator already at or past end.");
159    counted_iterator __tmp = *this;
160    ++*this;
161    return __tmp;
162  }
163
164  _LIBCPP_HIDE_FROM_ABI
165  constexpr counted_iterator& operator--()
166    requires bidirectional_iterator<_Iter>
167  {
168    --__current_;
169    ++__count_;
170    return *this;
171  }
172
173  _LIBCPP_HIDE_FROM_ABI
174  constexpr counted_iterator operator--(int)
175    requires bidirectional_iterator<_Iter>
176  {
177    counted_iterator __tmp = *this;
178    --*this;
179    return __tmp;
180  }
181
182  _LIBCPP_HIDE_FROM_ABI
183  constexpr counted_iterator operator+(iter_difference_t<_Iter> __n) const
184    requires random_access_iterator<_Iter>
185  {
186    return counted_iterator(__current_ + __n, __count_ - __n);
187  }
188
189  _LIBCPP_HIDE_FROM_ABI
190  friend constexpr counted_iterator operator+(
191    iter_difference_t<_Iter> __n, const counted_iterator& __x)
192    requires random_access_iterator<_Iter>
193  {
194    return __x + __n;
195  }
196
197  _LIBCPP_HIDE_FROM_ABI
198  constexpr counted_iterator& operator+=(iter_difference_t<_Iter> __n)
199    requires random_access_iterator<_Iter>
200  {
201    _LIBCPP_ASSERT(__n <= __count_, "Cannot advance iterator past end.");
202    __current_ += __n;
203    __count_ -= __n;
204    return *this;
205  }
206
207  _LIBCPP_HIDE_FROM_ABI
208  constexpr counted_iterator operator-(iter_difference_t<_Iter> __n) const
209    requires random_access_iterator<_Iter>
210  {
211    return counted_iterator(__current_ - __n, __count_ + __n);
212  }
213
214  template<common_with<_Iter> _I2>
215  _LIBCPP_HIDE_FROM_ABI
216  friend constexpr iter_difference_t<_I2> operator-(
217    const counted_iterator& __lhs, const counted_iterator<_I2>& __rhs)
218  {
219    return __rhs.__count_ - __lhs.__count_;
220  }
221
222  _LIBCPP_HIDE_FROM_ABI
223  friend constexpr iter_difference_t<_Iter> operator-(
224    const counted_iterator& __lhs, default_sentinel_t)
225  {
226    return -__lhs.__count_;
227  }
228
229  _LIBCPP_HIDE_FROM_ABI
230  friend constexpr iter_difference_t<_Iter> operator-(
231    default_sentinel_t, const counted_iterator& __rhs)
232  {
233    return __rhs.__count_;
234  }
235
236  _LIBCPP_HIDE_FROM_ABI
237  constexpr counted_iterator& operator-=(iter_difference_t<_Iter> __n)
238    requires random_access_iterator<_Iter>
239  {
240    _LIBCPP_ASSERT(-__n <= __count_, "Attempt to subtract too large of a size: "
241                                     "counted_iterator would be decremented before the "
242                                     "first element of its range.");
243    __current_ -= __n;
244    __count_ += __n;
245    return *this;
246  }
247
248  _LIBCPP_HIDE_FROM_ABI
249  constexpr decltype(auto) operator[](iter_difference_t<_Iter> __n) const
250    requires random_access_iterator<_Iter>
251  {
252    _LIBCPP_ASSERT(__n < __count_, "Subscript argument must be less than size.");
253    return __current_[__n];
254  }
255
256  template<common_with<_Iter> _I2>
257  _LIBCPP_HIDE_FROM_ABI
258  friend constexpr bool operator==(
259    const counted_iterator& __lhs, const counted_iterator<_I2>& __rhs)
260  {
261    return __lhs.__count_ == __rhs.__count_;
262  }
263
264  _LIBCPP_HIDE_FROM_ABI
265  friend constexpr bool operator==(
266    const counted_iterator& __lhs, default_sentinel_t)
267  {
268    return __lhs.__count_ == 0;
269  }
270
271  template<common_with<_Iter> _I2>
272  _LIBCPP_HIDE_FROM_ABI friend constexpr strong_ordering operator<=>(
273    const counted_iterator& __lhs, const counted_iterator<_I2>& __rhs)
274  {
275    return __rhs.__count_ <=> __lhs.__count_;
276  }
277
278  _LIBCPP_HIDE_FROM_ABI
279  friend constexpr iter_rvalue_reference_t<_Iter> iter_move(const counted_iterator& __i)
280    noexcept(noexcept(ranges::iter_move(__i.__current_)))
281      requires input_iterator<_Iter>
282  {
283    _LIBCPP_ASSERT(__i.__count_ > 0, "Iterator must not be past end of range.");
284    return ranges::iter_move(__i.__current_);
285  }
286
287  template<indirectly_swappable<_Iter> _I2>
288  _LIBCPP_HIDE_FROM_ABI
289  friend constexpr void iter_swap(const counted_iterator& __x, const counted_iterator<_I2>& __y)
290    noexcept(noexcept(ranges::iter_swap(__x.__current_, __y.__current_)))
291  {
292    _LIBCPP_ASSERT(__x.__count_ > 0 && __y.__count_ > 0,
293                   "Iterators must not be past end of range.");
294    return ranges::iter_swap(__x.__current_, __y.__current_);
295  }
296};
297_LIBCPP_CTAD_SUPPORTED_FOR_TYPE(counted_iterator);
298
299template<input_iterator _Iter>
300  requires same_as<_ITER_TRAITS<_Iter>, iterator_traits<_Iter>>
301struct iterator_traits<counted_iterator<_Iter>> : iterator_traits<_Iter> {
302  using pointer = conditional_t<contiguous_iterator<_Iter>,
303                                add_pointer_t<iter_reference_t<_Iter>>, void>;
304};
305
306#endif // _LIBCPP_STD_VER > 17
307
308_LIBCPP_END_NAMESPACE_STD
309
310#endif // _LIBCPP___ITERATOR_COUNTED_ITERATOR_H
311