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
  48   common_view() requires default_initializable<_View> = default;
  49
  50   _LIBCPP_HIDE_FROM_ABI
  51   constexpr explicit common_view(_View __v) : __base_(std::move(__v)) { }
  52
  53   _LIBCPP_HIDE_FROM_ABI
  54   constexpr _View base() const& requires copy_constructible<_View> { return __base_; }
  55
  56   _LIBCPP_HIDE_FROM_ABI
  57   constexpr _View base() && { return std::move(__base_); }
  58
  59   _LIBCPP_HIDE_FROM_ABI
  60   constexpr auto begin() {
  61     if constexpr (random_access_range<_View> && sized_range<_View>)
  62       return ranges::begin(__base_);
  63     else
  64       return common_iterator<iterator_t<_View>, sentinel_t<_View>>(ranges::begin(__base_));
  65   }
  66
  67   _LIBCPP_HIDE_FROM_ABI
  68   constexpr auto begin() const requires range<const _View> {
  69     if constexpr (random_access_range<const _View> && sized_range<const _View>)
  70       return ranges::begin(__base_);
  71     else
  72       return common_iterator<iterator_t<const _View>, sentinel_t<const _View>>(ranges::begin(__base_));
  73   }
  74
  75   _LIBCPP_HIDE_FROM_ABI
  76   constexpr auto end() {
  77     if constexpr (random_access_range<_View> && sized_range<_View>)
  78       return ranges::begin(__base_) + ranges::size(__base_);
  79     else
  80       return common_iterator<iterator_t<_View>, sentinel_t<_View>>(ranges::end(__base_));
  81   }
  82
  83   _LIBCPP_HIDE_FROM_ABI
  84   constexpr auto end() const requires range<const _View> {
  85     if constexpr (random_access_range<const _View> && sized_range<const _View>)
  86       return ranges::begin(__base_) + ranges::size(__base_);
  87     else
  88       return common_iterator<iterator_t<const _View>, sentinel_t<const _View>>(ranges::end(__base_));
  89   }
  90
  91   _LIBCPP_HIDE_FROM_ABI
  92   constexpr auto size() requires sized_range<_View> {
  93     return ranges::size(__base_);
  94   }
  95
  96   _LIBCPP_HIDE_FROM_ABI
  97   constexpr auto size() const requires sized_range<const _View> {
  98     return ranges::size(__base_);
  99   }
 100 };
 101
 102 template<class _Range>
 103 common_view(_Range&&)
 104   -> common_view<views::all_t<_Range>>;
 105
 106 template<class _View>
 107 inline constexpr bool enable_borrowed_range<common_view<_View>> = enable_borrowed_range<_View>;
 108
 109 namespace views {
 110 namespace __common {
 111   struct __fn : __range_adaptor_closure<__fn> {
 112     template<class _Range>
 113       requires common_range<_Range>
 114     [[nodiscard]] _LIBCPP_HIDE_FROM_ABI
 115     constexpr auto operator()(_Range&& __range) const
 116       noexcept(noexcept(views::all(std::forward<_Range>(__range))))
 117       -> decltype(      views::all(std::forward<_Range>(__range)))
 118       { return          views::all(std::forward<_Range>(__range)); }
 119
 120     template<class _Range>
 121     [[nodiscard]] _LIBCPP_HIDE_FROM_ABI
 122     constexpr auto operator()(_Range&& __range) const
 123       noexcept(noexcept(common_view{std::forward<_Range>(__range)}))
 124       -> decltype(      common_view{std::forward<_Range>(__range)})
 125       { return          common_view{std::forward<_Range>(__range)}; }
 126   };
 127 } // namespace __common
 128
 129 inline namespace __cpo {
 130   inline constexpr auto common = __common::__fn{};
 131 } // namespace __cpo
 132 } // namespace views
 133 } // namespace ranges
 134
 135 #endif // _LIBCPP_STD_VER >= 20
 136
 137 _LIBCPP_END_NAMESPACE_STD
 138
 139 _LIBCPP_POP_MACROS
 140
 141 #endif // _LIBCPP___RANGES_COMMON_VIEW_H