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___RANGES_VIEW_INTERFACE_H
11#define _LIBCPP___RANGES_VIEW_INTERFACE_H
12
13#include <__assert>
14#include <__concepts/derived_from.h>
15#include <__concepts/same_as.h>
16#include <__config>
17#include <__iterator/concepts.h>
18#include <__iterator/iterator_traits.h>
19#include <__iterator/prev.h>
20#include <__memory/pointer_traits.h>
21#include <__ranges/access.h>
22#include <__ranges/concepts.h>
23#include <__ranges/empty.h>
24#include <__type_traits/is_class.h>
25#include <__type_traits/make_unsigned.h>
26#include <__type_traits/remove_cv.h>
27
28#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
29#  pragma GCC system_header
30#endif
31
32_LIBCPP_BEGIN_NAMESPACE_STD
33
34#if _LIBCPP_STD_VER >= 20
35
36namespace ranges {
37
38template <class _Derived>
39  requires is_class_v<_Derived> && same_as<_Derived, remove_cv_t<_Derived>>
40class view_interface {
41  _LIBCPP_HIDE_FROM_ABI constexpr _Derived& __derived() noexcept {
42    static_assert(sizeof(_Derived) && derived_from<_Derived, view_interface> && view<_Derived>);
43    return static_cast<_Derived&>(*this);
44  }
45
46  _LIBCPP_HIDE_FROM_ABI constexpr _Derived const& __derived() const noexcept {
47    static_assert(sizeof(_Derived) && derived_from<_Derived, view_interface> && view<_Derived>);
48    return static_cast<_Derived const&>(*this);
49  }
50
51public:
52  template <class _D2 = _Derived>
53  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool empty()
54    requires forward_range<_D2>
55  {
56    return ranges::begin(__derived()) == ranges::end(__derived());
57  }
58
59  template <class _D2 = _Derived>
60  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool empty() const
61    requires forward_range<const _D2>
62  {
63    return ranges::begin(__derived()) == ranges::end(__derived());
64  }
65
66  template <class _D2 = _Derived>
67  _LIBCPP_HIDE_FROM_ABI constexpr explicit operator bool()
68    requires requires(_D2& __t) { ranges::empty(__t); }
69  {
70    return !ranges::empty(__derived());
71  }
72
73  template <class _D2 = _Derived>
74  _LIBCPP_HIDE_FROM_ABI constexpr explicit operator bool() const
75    requires requires(const _D2& __t) { ranges::empty(__t); }
76  {
77    return !ranges::empty(__derived());
78  }
79
80  template <class _D2 = _Derived>
81  _LIBCPP_HIDE_FROM_ABI constexpr auto data()
82    requires contiguous_iterator<iterator_t<_D2>>
83  {
84    return std::to_address(ranges::begin(__derived()));
85  }
86
87  template <class _D2 = _Derived>
88  _LIBCPP_HIDE_FROM_ABI constexpr auto data() const
89    requires range<const _D2> && contiguous_iterator<iterator_t<const _D2>>
90  {
91    return std::to_address(ranges::begin(__derived()));
92  }
93
94  template <class _D2 = _Derived>
95  _LIBCPP_HIDE_FROM_ABI constexpr auto size()
96    requires forward_range<_D2> && sized_sentinel_for<sentinel_t<_D2>, iterator_t<_D2>>
97  {
98    return std::__to_unsigned_like(ranges::end(__derived()) - ranges::begin(__derived()));
99  }
100
101  template <class _D2 = _Derived>
102  _LIBCPP_HIDE_FROM_ABI constexpr auto size() const
103    requires forward_range<const _D2> && sized_sentinel_for<sentinel_t<const _D2>, iterator_t<const _D2>>
104  {
105    return std::__to_unsigned_like(ranges::end(__derived()) - ranges::begin(__derived()));
106  }
107
108  template <class _D2 = _Derived>
109  _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) front()
110    requires forward_range<_D2>
111  {
112    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
113        !empty(), "Precondition `!empty()` not satisfied. `.front()` called on an empty view.");
114    return *ranges::begin(__derived());
115  }
116
117  template <class _D2 = _Derived>
118  _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) front() const
119    requires forward_range<const _D2>
120  {
121    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
122        !empty(), "Precondition `!empty()` not satisfied. `.front()` called on an empty view.");
123    return *ranges::begin(__derived());
124  }
125
126  template <class _D2 = _Derived>
127  _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) back()
128    requires bidirectional_range<_D2> && common_range<_D2>
129  {
130    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
131        !empty(), "Precondition `!empty()` not satisfied. `.back()` called on an empty view.");
132    return *ranges::prev(ranges::end(__derived()));
133  }
134
135  template <class _D2 = _Derived>
136  _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) back() const
137    requires bidirectional_range<const _D2> && common_range<const _D2>
138  {
139    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
140        !empty(), "Precondition `!empty()` not satisfied. `.back()` called on an empty view.");
141    return *ranges::prev(ranges::end(__derived()));
142  }
143
144  template <random_access_range _RARange = _Derived>
145  _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) operator[](range_difference_t<_RARange> __index) {
146    return ranges::begin(__derived())[__index];
147  }
148
149  template <random_access_range _RARange = const _Derived>
150  _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) operator[](range_difference_t<_RARange> __index) const {
151    return ranges::begin(__derived())[__index];
152  }
153};
154
155} // namespace ranges
156
157#endif // _LIBCPP_STD_VER >= 20
158
159_LIBCPP_END_NAMESPACE_STD
160
161#endif // _LIBCPP___RANGES_VIEW_INTERFACE_H
162