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_SINGLE_VIEW_H 11 #define _LIBCPP___RANGES_SINGLE_VIEW_H 12 13 #include <__concepts/constructible.h> 14 #include <__config> 15 #include <__ranges/movable_box.h> 16 #include <__ranges/range_adaptor.h> 17 #include <__ranges/view_interface.h> 18 #include <__type_traits/decay.h> 19 #include <__type_traits/is_object.h> 20 #include <__utility/forward.h> 21 #include <__utility/in_place.h> 22 #include <__utility/move.h> 23 #include <cstddef> 24 25 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 26 # pragma GCC system_header 27 #endif 28 29 _LIBCPP_PUSH_MACROS 30 #include <__undef_macros> 31 32 _LIBCPP_BEGIN_NAMESPACE_STD 33 34 #if _LIBCPP_STD_VER >= 20 35 36 namespace ranges { 37 # if _LIBCPP_STD_VER >= 23 38 template <move_constructible _Tp> 39 # else 40 template <copy_constructible _Tp> 41 # endif 42 requires is_object_v<_Tp> 43 class _LIBCPP_ABI_LLVM18_NO_UNIQUE_ADDRESS single_view : public view_interface<single_view<_Tp>> { 44 _LIBCPP_NO_UNIQUE_ADDRESS __movable_box<_Tp> __value_; 45 46 public: 47 _LIBCPP_HIDE_FROM_ABI single_view() 48 requires default_initializable<_Tp> 49 = default; 50 51 _LIBCPP_HIDE_FROM_ABI constexpr explicit single_view(const _Tp& __t) 52 # if _LIBCPP_STD_VER >= 23 53 requires copy_constructible<_Tp> 54 # endif 55 : __value_(in_place, __t) { 56 } 57 58 _LIBCPP_HIDE_FROM_ABI constexpr explicit single_view(_Tp&& __t) : __value_(in_place, std::move(__t)) {} 59 60 template <class... _Args> 61 requires constructible_from<_Tp, _Args...> 62 _LIBCPP_HIDE_FROM_ABI constexpr explicit single_view(in_place_t, _Args&&... __args) 63 : __value_{in_place, std::forward<_Args>(__args)...} {} 64 65 _LIBCPP_HIDE_FROM_ABI constexpr _Tp* begin() noexcept { return data(); } 66 67 _LIBCPP_HIDE_FROM_ABI constexpr const _Tp* begin() const noexcept { return data(); } 68 69 _LIBCPP_HIDE_FROM_ABI constexpr _Tp* end() noexcept { return data() + 1; } 70 71 _LIBCPP_HIDE_FROM_ABI constexpr const _Tp* end() const noexcept { return data() + 1; } 72 73 _LIBCPP_HIDE_FROM_ABI static constexpr size_t size() noexcept { return 1; } 74 75 _LIBCPP_HIDE_FROM_ABI constexpr _Tp* data() noexcept { return __value_.operator->(); } 76 77 _LIBCPP_HIDE_FROM_ABI constexpr const _Tp* data() const noexcept { return __value_.operator->(); } 78 }; 79 80 template <class _Tp> 81 single_view(_Tp) -> single_view<_Tp>; 82 83 namespace views { 84 namespace __single_view { 85 86 struct __fn : __range_adaptor_closure<__fn> { 87 template <class _Range> 88 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range) const 89 noexcept(noexcept(single_view<decay_t<_Range&&>>(std::forward<_Range>(__range)))) 90 -> decltype(single_view<decay_t<_Range&&>>(std::forward<_Range>(__range))) { 91 return single_view<decay_t<_Range&&>>(std::forward<_Range>(__range)); 92 } 93 }; 94 } // namespace __single_view 95 96 inline namespace __cpo { 97 inline constexpr auto single = __single_view::__fn{}; 98 } // namespace __cpo 99 100 } // namespace views 101 } // namespace ranges 102 103 #endif // _LIBCPP_STD_VER >= 20 104 105 _LIBCPP_END_NAMESPACE_STD 106 107 _LIBCPP_POP_MACROS 108 109 #endif // _LIBCPP___RANGES_SINGLE_VIEW_H 110