libcxx/include/__ranges/common_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___RANGES_COMMON_VIEW_H
  11 #define _LIBCPP___RANGES_COMMON_VIEW_H
  12
  13 #include <__concepts/constructible.h>
  14 #include <__concepts/copyable.h>
  15 #include <__config>
  16 #include <__iterator/common_iterator.h>
  17 #include <__iterator/iterator_traits.h>
  18 #include <__ranges/access.h>
  19 #include <__ranges/all.h>
  20 #include <__ranges/concepts.h>
  21 #include <__ranges/enable_borrowed_range.h>
  22 #include <__ranges/range_adaptor.h>
  23 #include <__ranges/size.h>
  24 #include <__ranges/view_interface.h>
  25 #include <__utility/forward.h>
  26 #include <__utility/move.h>
  27
  28 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  29 #  pragma GCC system_header
  30 #endif
  31
  32 _LIBCPP_PUSH_MACROS
  33 #include <__undef_macros>
  34
  35 _LIBCPP_BEGIN_NAMESPACE_STD
  36
  37 #if _LIBCPP_STD_VER >= 20
  38
  39 namespace ranges {
  40
  41 template <view _View>
  42   requires(!common_range<_View> && copyable<iterator_t<_View>>)
  43 class common_view : public view_interface<common_view<_View>> {
  44   _View __base_ = _View();
  45
  46 public:
  47   _LIBCPP_HIDE_FROM_ABI common_view()
  48     requires default_initializable<_View>
  49   = default;
  50
  51   _LIBCPP_HIDE_FROM_ABI constexpr explicit common_view(_View __v) : __base_(std::move(__v)) {}
  52
  53   _LIBCPP_HIDE_FROM_ABI constexpr _View base() const&
  54     requires copy_constructible<_View>
  55   {
  56     return __base_;
  57   }
  58
  59   _LIBCPP_HIDE_FROM_ABI constexpr _View base() && { return std::move(__base_); }
  60
  61   _LIBCPP_HIDE_FROM_ABI constexpr auto begin() {
  62     if constexpr (random_access_range<_View> && sized_range<_View>)
  63       return ranges::begin(__base_);
  64     else
  65       return common_iterator<iterator_t<_View>, sentinel_t<_View>>(ranges::begin(__base_));
  66   }
  67
  68   _LIBCPP_HIDE_FROM_ABI constexpr auto begin() const
  69     requires range<const _View>
  70   {
  71     if constexpr (random_access_range<const _View> && sized_range<const _View>)
  72       return ranges::begin(__base_);
  73     else
  74       return common_iterator<iterator_t<const _View>, sentinel_t<const _View>>(ranges::begin(__base_));
  75   }
  76
  77   _LIBCPP_HIDE_FROM_ABI constexpr auto end() {
  78     if constexpr (random_access_range<_View> && sized_range<_View>)
  79       return ranges::begin(__base_) + ranges::size(__base_);
  80     else
  81       return common_iterator<iterator_t<_View>, sentinel_t<_View>>(ranges::end(__base_));
  82   }
  83
  84   _LIBCPP_HIDE_FROM_ABI constexpr auto end() const
  85     requires range<const _View>
  86   {
  87     if constexpr (random_access_range<const _View> && sized_range<const _View>)
  88       return ranges::begin(__base_) + ranges::size(__base_);
  89     else
  90       return common_iterator<iterator_t<const _View>, sentinel_t<const _View>>(ranges::end(__base_));
  91   }
  92
  93   _LIBCPP_HIDE_FROM_ABI constexpr auto size()
  94     requires sized_range<_View>
  95   {
  96     return ranges::size(__base_);
  97   }
  98
  99   _LIBCPP_HIDE_FROM_ABI constexpr auto size() const
 100     requires sized_range<const _View>
 101   {
 102     return ranges::size(__base_);
 103   }
 104 };
 105
 106 template <class _Range>
 107 common_view(_Range&&) -> common_view<views::all_t<_Range>>;
 108
 109 template <class _View>
 110 inline constexpr bool enable_borrowed_range<common_view<_View>> = enable_borrowed_range<_View>;
 111
 112 namespace views {
 113 namespace __common {
 114 struct __fn : __range_adaptor_closure<__fn> {
 115   template <class _Range>
 116     requires common_range<_Range>
 117   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range) const noexcept(
 118       noexcept(views::all(std::forward<_Range>(__range)))) -> decltype(views::all(std::forward<_Range>(__range))) {
 119     return views::all(std::forward<_Range>(__range));
 120   }
 121
 122   template <class _Range>
 123   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range) const noexcept(noexcept(common_view{
 124       std::forward<_Range>(__range)})) -> decltype(common_view{std::forward<_Range>(__range)}) {
 125     return common_view{std::forward<_Range>(__range)};
 126   }
 127 };
 128 } // namespace __common
 129
 130 inline namespace __cpo {
 131 inline constexpr auto common = __common::__fn{};
 132 } // namespace __cpo
 133 } // namespace views
 134 } // namespace ranges
 135
 136 #endif // _LIBCPP_STD_VER >= 20
 137
 138 _LIBCPP_END_NAMESPACE_STD
 139
 140 _LIBCPP_POP_MACROS
 141
 142 #endif // _LIBCPP___RANGES_COMMON_VIEW_H