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 <__ranges/size.h>
25#include <__type_traits/is_class.h>
26#include <__type_traits/make_unsigned.h>
27#include <__type_traits/remove_cv.h>
28
29#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
30# pragma GCC system_header
31#endif
32
33_LIBCPP_BEGIN_NAMESPACE_STD
34
35#if _LIBCPP_STD_VER >= 20
36
37namespace ranges {
38
39template <class _Derived>
40 requires is_class_v<_Derived> && same_as<_Derived, remove_cv_t<_Derived>>
41class view_interface {
42 _LIBCPP_HIDE_FROM_ABI constexpr _Derived& __derived() noexcept {
43 static_assert(sizeof(_Derived) && derived_from<_Derived, view_interface> && view<_Derived>);
44 return static_cast<_Derived&>(*this);
45 }
46
47 _LIBCPP_HIDE_FROM_ABI constexpr _Derived const& __derived() const noexcept {
48 static_assert(sizeof(_Derived) && derived_from<_Derived, view_interface> && view<_Derived>);
49 return static_cast<_Derived const&>(*this);
50 }
51
52public:
53 template <class _D2 = _Derived>
54 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool empty()
55 requires sized_range<_D2> || forward_range<_D2>
56 {
57 if constexpr (sized_range<_D2>) {
58 return ranges::size(__derived()) == 0;
59 } else {
60 return ranges::begin(__derived()) == ranges::end(__derived());
61 }
62 }
63
64 template <class _D2 = _Derived>
65 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool empty() const
66 requires sized_range<const _D2> || forward_range<const _D2>
67 {
68 if constexpr (sized_range<const _D2>) {
69 return ranges::size(__derived()) == 0;
70 } else {
71 return ranges::begin(__derived()) == ranges::end(__derived());
72 }
73 }
74
75 template <class _D2 = _Derived>
76 _LIBCPP_HIDE_FROM_ABI constexpr explicit operator bool()
77 requires requires(_D2& __t) { ranges::empty(__t); }
78 {
79 return !ranges::empty(__derived());
80 }
81
82 template <class _D2 = _Derived>
83 _LIBCPP_HIDE_FROM_ABI constexpr explicit operator bool() const
84 requires requires(const _D2& __t) { ranges::empty(__t); }
85 {
86 return !ranges::empty(__derived());
87 }
88
89 template <class _D2 = _Derived>
90 _LIBCPP_HIDE_FROM_ABI constexpr auto data()
91 requires contiguous_iterator<iterator_t<_D2>>
92 {
93 return std::to_address(ranges::begin(__derived()));
94 }
95
96 template <class _D2 = _Derived>
97 _LIBCPP_HIDE_FROM_ABI constexpr auto data() const
98 requires range<const _D2> && contiguous_iterator<iterator_t<const _D2>>
99 {
100 return std::to_address(ranges::begin(__derived()));
101 }
102
103 template <class _D2 = _Derived>
104 _LIBCPP_HIDE_FROM_ABI constexpr auto size()
105 requires forward_range<_D2> && sized_sentinel_for<sentinel_t<_D2>, iterator_t<_D2>>
106 {
107 return std::__to_unsigned_like(ranges::end(__derived()) - ranges::begin(__derived()));
108 }
109
110 template <class _D2 = _Derived>
111 _LIBCPP_HIDE_FROM_ABI constexpr auto size() const
112 requires forward_range<const _D2> && sized_sentinel_for<sentinel_t<const _D2>, iterator_t<const _D2>>
113 {
114 return std::__to_unsigned_like(ranges::end(__derived()) - ranges::begin(__derived()));
115 }
116
117 template <class _D2 = _Derived>
118 _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) front()
119 requires forward_range<_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) front() const
128 requires forward_range<const _D2>
129 {
130 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
131 !empty(), "Precondition `!empty()` not satisfied. `.front()` called on an empty view.");
132 return *ranges::begin(__derived());
133 }
134
135 template <class _D2 = _Derived>
136 _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) back()
137 requires bidirectional_range<_D2> && common_range<_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 <class _D2 = _Derived>
145 _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) back() const
146 requires bidirectional_range<const _D2> && common_range<const _D2>
147 {
148 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
149 !empty(), "Precondition `!empty()` not satisfied. `.back()` called on an empty view.");
150 return *ranges::prev(ranges::end(__derived()));
151 }
152
153 template <random_access_range _RARange = _Derived>
154 _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) operator[](range_difference_t<_RARange> __index) {
155 return ranges::begin(__derived())[__index];
156 }
157
158 template <random_access_range _RARange = const _Derived>
159 _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) operator[](range_difference_t<_RARange> __index) const {
160 return ranges::begin(__derived())[__index];
161 }
162};
163
164} // namespace ranges
165
166#endif // _LIBCPP_STD_VER >= 20
167
168_LIBCPP_END_NAMESPACE_STD
169
170#endif // _LIBCPP___RANGES_VIEW_INTERFACE_H
171