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 <__ranges/size.h>
  25 #include <__type_traits/is_class.h>
  26 #include <__type_traits/make_unsigned.h>
  27 #include <__type_traits/remove_cv.h>
  28
  29 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  30 #  pragma GCC system_header
  31 #endif
  32
  33 _LIBCPP_BEGIN_NAMESPACE_STD
  34
  35 #if _LIBCPP_STD_VER >= 20
  36
  37 namespace ranges {
  38
  39 template <class _Derived>
  40   requires is_class_v<_Derived> && same_as<_Derived, remove_cv_t<_Derived>>
  41 class view_interface {
  42   _LIBCPP_HIDE_FROM_ABI 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 constexpr _Derived const& __derived() const noexcept {
  48     static_assert(sizeof(_Derived) && derived_from<_Derived, view_interface> && view<_Derived>);
  49     return static_cast<_Derived const&>(*this);
  50   }
  51
  52 public:
  53   template <class _D2 = _Derived>
  54   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool empty()
  55     requires sized_range<_D2> || forward_range<_D2>
  56   {
  57     if constexpr (sized_range<_D2>) {
  58       return ranges::size(__derived()) == 0;
  59     } else {
  60       return ranges::begin(__derived()) == ranges::end(__derived());
  61     }
  62   }
  63
  64   template <class _D2 = _Derived>
  65   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool empty() const
  66     requires sized_range<const _D2> || forward_range<const _D2>
  67   {
  68     if constexpr (sized_range<const _D2>) {
  69       return ranges::size(__derived()) == 0;
  70     } else {
  71       return ranges::begin(__derived()) == ranges::end(__derived());
  72     }
  73   }
  74
  75   template <class _D2 = _Derived>
  76   _LIBCPP_HIDE_FROM_ABI constexpr explicit operator bool()
  77     requires requires(_D2& __t) { ranges::empty(__t); }
  78   {
  79     return !ranges::empty(__derived());
  80   }
  81
  82   template <class _D2 = _Derived>
  83   _LIBCPP_HIDE_FROM_ABI constexpr explicit operator bool() const
  84     requires requires(const _D2& __t) { ranges::empty(__t); }
  85   {
  86     return !ranges::empty(__derived());
  87   }
  88
  89   template <class _D2 = _Derived>
  90   _LIBCPP_HIDE_FROM_ABI constexpr auto data()
  91     requires contiguous_iterator<iterator_t<_D2>>
  92   {
  93     return std::to_address(ranges::begin(__derived()));
  94   }
  95
  96   template <class _D2 = _Derived>
  97   _LIBCPP_HIDE_FROM_ABI constexpr auto data() const
  98     requires range<const _D2> && contiguous_iterator<iterator_t<const _D2>>
  99   {
 100     return std::to_address(ranges::begin(__derived()));
 101   }
 102
 103   template <class _D2 = _Derived>
 104   _LIBCPP_HIDE_FROM_ABI constexpr auto size()
 105     requires forward_range<_D2> && sized_sentinel_for<sentinel_t<_D2>, iterator_t<_D2>>
 106   {
 107     return std::__to_unsigned_like(ranges::end(__derived()) - ranges::begin(__derived()));
 108   }
 109
 110   template <class _D2 = _Derived>
 111   _LIBCPP_HIDE_FROM_ABI constexpr auto size() const
 112     requires forward_range<const _D2> && sized_sentinel_for<sentinel_t<const _D2>, iterator_t<const _D2>>
 113   {
 114     return std::__to_unsigned_like(ranges::end(__derived()) - ranges::begin(__derived()));
 115   }
 116
 117   template <class _D2 = _Derived>
 118   _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) front()
 119     requires forward_range<_D2>
 120   {
 121     _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
 122         !empty(), "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 constexpr decltype(auto) front() const
 128     requires forward_range<const _D2>
 129   {
 130     _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
 131         !empty(), "Precondition `!empty()` not satisfied. `.front()` called on an empty view.");
 132     return *ranges::begin(__derived());
 133   }
 134
 135   template <class _D2 = _Derived>
 136   _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) back()
 137     requires bidirectional_range<_D2> && common_range<_D2>
 138   {
 139     _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
 140         !empty(), "Precondition `!empty()` not satisfied. `.back()` called on an empty view.");
 141     return *ranges::prev(ranges::end(__derived()));
 142   }
 143
 144   template <class _D2 = _Derived>
 145   _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) back() const
 146     requires bidirectional_range<const _D2> && common_range<const _D2>
 147   {
 148     _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
 149         !empty(), "Precondition `!empty()` not satisfied. `.back()` called on an empty view.");
 150     return *ranges::prev(ranges::end(__derived()));
 151   }
 152
 153   template <random_access_range _RARange = _Derived>
 154   _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) operator[](range_difference_t<_RARange> __index) {
 155     return ranges::begin(__derived())[__index];
 156   }
 157
 158   template <random_access_range _RARange = const _Derived>
 159   _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) operator[](range_difference_t<_RARange> __index) const {
 160     return ranges::begin(__derived())[__index];
 161   }
 162 };
 163
 164 } // namespace ranges
 165
 166 #endif // _LIBCPP_STD_VER >= 20
 167
 168 _LIBCPP_END_NAMESPACE_STD
 169
 170 #endif // _LIBCPP___RANGES_VIEW_INTERFACE_H