libcxx/include/__cxx03/__ranges/single_view.h

   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___CXX03___RANGES_SINGLE_VIEW_H
  11 #define _LIBCPP___CXX03___RANGES_SINGLE_VIEW_H
  12
  13 #include <__cxx03/__concepts/constructible.h>
  14 #include <__cxx03/__config>
  15 #include <__cxx03/__ranges/movable_box.h>
  16 #include <__cxx03/__ranges/range_adaptor.h>
  17 #include <__cxx03/__ranges/view_interface.h>
  18 #include <__cxx03/__type_traits/decay.h>
  19 #include <__cxx03/__type_traits/is_object.h>
  20 #include <__cxx03/__utility/forward.h>
  21 #include <__cxx03/__utility/in_place.h>
  22 #include <__cxx03/__utility/move.h>
  23 #include <__cxx03/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 <__cxx03/__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 bool empty() noexcept { return false; }
  74
  75   _LIBCPP_HIDE_FROM_ABI static constexpr size_t size() noexcept { return 1; }
  76
  77   _LIBCPP_HIDE_FROM_ABI constexpr _Tp* data() noexcept { return __value_.operator->(); }
  78
  79   _LIBCPP_HIDE_FROM_ABI constexpr const _Tp* data() const noexcept { return __value_.operator->(); }
  80 };
  81
  82 template <class _Tp>
  83 single_view(_Tp) -> single_view<_Tp>;
  84
  85 namespace views {
  86 namespace __single_view {
  87
  88 struct __fn : __range_adaptor_closure<__fn> {
  89   template <class _Range>
  90   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range) const
  91       noexcept(noexcept(single_view<decay_t<_Range&&>>(std::forward<_Range>(__range))))
  92           -> decltype(single_view<decay_t<_Range&&>>(std::forward<_Range>(__range))) {
  93     return single_view<decay_t<_Range&&>>(std::forward<_Range>(__range));
  94   }
  95 };
  96 } // namespace __single_view
  97
  98 inline namespace __cpo {
  99 inline constexpr auto single = __single_view::__fn{};
 100 } // namespace __cpo
 101
 102 } // namespace views
 103 } // namespace ranges
 104
 105 #endif // _LIBCPP_STD_VER >= 20
 106
 107 _LIBCPP_END_NAMESPACE_STD
 108
 109 _LIBCPP_POP_MACROS
 110
 111 #endif // _LIBCPP___CXX03___RANGES_SINGLE_VIEW_H