libcxx/include/__ranges/view_interface.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_VIEW_INTERFACE_H
  11 #define _LIBCPP___RANGES_VIEW_INTERFACE_H
  12
  13 #include <__assert>
  14 #include <__concepts/derived_from.h>
  15 #include <__concepts/same_as.h>
  16 #include <__config>
  17 #include <__iterator/concepts.h>
  18 #include <__iterator/iterator_traits.h>
  19 #include <__iterator/prev.h>
  20 #include <__memory/pointer_traits.h>
  21 #include <__ranges/access.h>
  22 #include <__ranges/concepts.h>
  23 #include <__ranges/empty.h>
  24 #include <__type_traits/is_class.h>
  25 #include <__type_traits/make_unsigned.h>
  26 #include <__type_traits/remove_cv.h>
  27
  28 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  29 #  pragma GCC system_header
  30 #endif
  31
  32 _LIBCPP_BEGIN_NAMESPACE_STD
  33
  34 #if _LIBCPP_STD_VER >= 20
  35
  36 namespace ranges {
  37
  38 template<class _Derived>
  39   requires is_class_v<_Derived> && same_as<_Derived, remove_cv_t<_Derived>>
  40 class view_interface {
  41   _LIBCPP_HIDE_FROM_ABI
  42   constexpr _Derived& __derived() noexcept {
  43     static_assert(sizeof(_Derived) && derived_from<_Derived, view_interface> && view<_Derived>);
  44     return static_cast<_Derived&>(*this);
  45   }
  46
  47   _LIBCPP_HIDE_FROM_ABI
  48   constexpr _Derived const& __derived() const noexcept {
  49     static_assert(sizeof(_Derived) && derived_from<_Derived, view_interface> && view<_Derived>);
  50     return static_cast<_Derived const&>(*this);
  51   }
  52
  53 public:
  54   template<class _D2 = _Derived>
  55   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool empty()
  56     requires forward_range<_D2>
  57   {
  58     return ranges::begin(__derived()) == ranges::end(__derived());
  59   }
  60
  61   template<class _D2 = _Derived>
  62   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool empty() const
  63     requires forward_range<const _D2>
  64   {
  65     return ranges::begin(__derived()) == ranges::end(__derived());
  66   }
  67
  68   template<class _D2 = _Derived>
  69   _LIBCPP_HIDE_FROM_ABI
  70   constexpr explicit operator bool()
  71     requires requires (_D2& __t) { ranges::empty(__t); }
  72   {
  73     return !ranges::empty(__derived());
  74   }
  75
  76   template<class _D2 = _Derived>
  77   _LIBCPP_HIDE_FROM_ABI
  78   constexpr explicit operator bool() const
  79     requires requires (const _D2& __t) { ranges::empty(__t); }
  80   {
  81     return !ranges::empty(__derived());
  82   }
  83
  84   template<class _D2 = _Derived>
  85   _LIBCPP_HIDE_FROM_ABI
  86   constexpr auto data()
  87     requires contiguous_iterator<iterator_t<_D2>>
  88   {
  89     return std::to_address(ranges::begin(__derived()));
  90   }
  91
  92   template<class _D2 = _Derived>
  93   _LIBCPP_HIDE_FROM_ABI
  94   constexpr auto data() const
  95     requires range<const _D2> && contiguous_iterator<iterator_t<const _D2>>
  96   {
  97     return std::to_address(ranges::begin(__derived()));
  98   }
  99
 100   template<class _D2 = _Derived>
 101   _LIBCPP_HIDE_FROM_ABI
 102   constexpr auto size()
 103     requires forward_range<_D2> && sized_sentinel_for<sentinel_t<_D2>, iterator_t<_D2>>
 104   {
 105     return std::__to_unsigned_like(ranges::end(__derived()) - ranges::begin(__derived()));
 106   }
 107
 108   template<class _D2 = _Derived>
 109   _LIBCPP_HIDE_FROM_ABI
 110   constexpr auto size() const
 111     requires forward_range<const _D2> && sized_sentinel_for<sentinel_t<const _D2>, iterator_t<const _D2>>
 112   {
 113     return std::__to_unsigned_like(ranges::end(__derived()) - ranges::begin(__derived()));
 114   }
 115
 116   template<class _D2 = _Derived>
 117   _LIBCPP_HIDE_FROM_ABI
 118   constexpr decltype(auto) front()
 119     requires forward_range<_D2>
 120   {
 121     _LIBCPP_ASSERT_UNCATEGORIZED(!empty(),
 122         "Precondition `!empty()` not satisfied. `.front()` called on an empty view.");
 123     return *ranges::begin(__derived());
 124   }
 125
 126   template<class _D2 = _Derived>
 127   _LIBCPP_HIDE_FROM_ABI
 128   constexpr decltype(auto) front() const
 129     requires forward_range<const _D2>
 130   {
 131     _LIBCPP_ASSERT_UNCATEGORIZED(!empty(),
 132         "Precondition `!empty()` not satisfied. `.front()` called on an empty view.");
 133     return *ranges::begin(__derived());
 134   }
 135
 136   template<class _D2 = _Derived>
 137   _LIBCPP_HIDE_FROM_ABI
 138   constexpr decltype(auto) back()
 139     requires bidirectional_range<_D2> && common_range<_D2>
 140   {
 141     _LIBCPP_ASSERT_UNCATEGORIZED(!empty(),
 142         "Precondition `!empty()` not satisfied. `.back()` called on an empty view.");
 143     return *ranges::prev(ranges::end(__derived()));
 144   }
 145
 146   template<class _D2 = _Derived>
 147   _LIBCPP_HIDE_FROM_ABI
 148   constexpr decltype(auto) back() const
 149     requires bidirectional_range<const _D2> && common_range<const _D2>
 150   {
 151     _LIBCPP_ASSERT_UNCATEGORIZED(!empty(),
 152         "Precondition `!empty()` not satisfied. `.back()` called on an empty view.");
 153     return *ranges::prev(ranges::end(__derived()));
 154   }
 155
 156   template<random_access_range _RARange = _Derived>
 157   _LIBCPP_HIDE_FROM_ABI
 158   constexpr decltype(auto) operator[](range_difference_t<_RARange> __index)
 159   {
 160     return ranges::begin(__derived())[__index];
 161   }
 162
 163   template<random_access_range _RARange = const _Derived>
 164   _LIBCPP_HIDE_FROM_ABI
 165   constexpr decltype(auto) operator[](range_difference_t<_RARange> __index) const
 166   {
 167     return ranges::begin(__derived())[__index];
 168   }
 169 };
 170
 171 } // namespace ranges
 172
 173 #endif // _LIBCPP_STD_VER >= 20
 174
 175 _LIBCPP_END_NAMESPACE_STD
 176
 177 #endif // _LIBCPP___RANGES_VIEW_INTERFACE_H