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 <__cstddef/ptrdiff_t.h> 16 #include <__cstddef/size_t.h> 17 #include <__ranges/movable_box.h> 18 #include <__ranges/range_adaptor.h> 19 #include <__ranges/view_interface.h> 20 #include <__type_traits/decay.h> 21 #include <__type_traits/is_object.h> 22 #include <__utility/forward.h> 23 #include <__utility/in_place.h> 24 #include <__utility/move.h> 25 26 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 27 # pragma GCC system_header 28 #endif 29 30 _LIBCPP_PUSH_MACROS 31 #include <__undef_macros> 32 33 _LIBCPP_BEGIN_NAMESPACE_STD 34 35 #if _LIBCPP_STD_VER >= 20 36 37 namespace ranges { 38 # if _LIBCPP_STD_VER >= 23 39 template <move_constructible _Tp> 40 # else 41 template <copy_constructible _Tp> 42 # endif 43 requires is_object_v<_Tp> 44 class _LIBCPP_ABI_LLVM18_NO_UNIQUE_ADDRESS single_view : public view_interface<single_view<_Tp>> { 45 _LIBCPP_NO_UNIQUE_ADDRESS __movable_box<_Tp> __value_; 46 47 public: 48 _LIBCPP_HIDE_FROM_ABI single_view() 49 requires default_initializable<_Tp> 50 = default; 51 52 _LIBCPP_HIDE_FROM_ABI constexpr explicit single_view(const _Tp& __t) 53 # if _LIBCPP_STD_VER >= 23 54 requires copy_constructible<_Tp> 55 # endif 56 : __value_(in_place, __t) { 57 } 58 59 _LIBCPP_HIDE_FROM_ABI constexpr explicit single_view(_Tp&& __t) : __value_(in_place, std::move(__t)) {} 60 61 template <class... _Args> 62 requires constructible_from<_Tp, _Args...> 63 _LIBCPP_HIDE_FROM_ABI constexpr explicit single_view(in_place_t, _Args&&... __args) 64 : __value_{in_place, std::forward<_Args>(__args)...} {} 65 66 _LIBCPP_HIDE_FROM_ABI constexpr _Tp* begin() noexcept { return data(); } 67 68 _LIBCPP_HIDE_FROM_ABI constexpr const _Tp* begin() const noexcept { return data(); } 69 70 _LIBCPP_HIDE_FROM_ABI constexpr _Tp* end() noexcept { return data() + 1; } 71 72 _LIBCPP_HIDE_FROM_ABI constexpr const _Tp* end() const noexcept { return data() + 1; } 73 74 _LIBCPP_HIDE_FROM_ABI static constexpr bool empty() noexcept { return false; } 75 76 _LIBCPP_HIDE_FROM_ABI static constexpr size_t size() noexcept { return 1; } 77 78 _LIBCPP_HIDE_FROM_ABI constexpr _Tp* data() noexcept { return __value_.operator->(); } 79 80 _LIBCPP_HIDE_FROM_ABI constexpr const _Tp* data() const noexcept { return __value_.operator->(); } 81 }; 82 83 template <class _Tp> 84 single_view(_Tp) -> single_view<_Tp>; 85 86 namespace views { 87 namespace __single_view { 88 89 struct __fn : __range_adaptor_closure<__fn> { 90 template <class _Range> 91 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range) const 92 noexcept(noexcept(single_view<decay_t<_Range&&>>(std::forward<_Range>(__range)))) 93 -> decltype(single_view<decay_t<_Range&&>>(std::forward<_Range>(__range))) { 94 return single_view<decay_t<_Range&&>>(std::forward<_Range>(__range)); 95 } 96 }; 97 } // namespace __single_view 98 99 inline namespace __cpo { 100 inline constexpr auto single = __single_view::__fn{}; 101 } // namespace __cpo 102 103 } // namespace views 104 } // namespace ranges 105 106 #endif // _LIBCPP_STD_VER >= 20 107 108 _LIBCPP_END_NAMESPACE_STD 109 110 _LIBCPP_POP_MACROS 111 112 #endif // _LIBCPP___RANGES_SINGLE_VIEW_H 113