v1/__ranges/view_interface.h

0001 // -*- C++ -*-
0002 //===----------------------------------------------------------------------===//
0003 //
0004 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0005 // See https://llvm.org/LICENSE.txt for license information.
0006 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0007 //
0008 //===----------------------------------------------------------------------===//
0009
0010 #ifndef _LIBCPP___RANGES_VIEW_INTERFACE_H
0011 #define _LIBCPP___RANGES_VIEW_INTERFACE_H
0012
0013 #include <__assert>
0014 #include <__concepts/derived_from.h>
0015 #include <__concepts/same_as.h>
0016 #include <__config>
0017 #include <__iterator/concepts.h>
0018 #include <__iterator/iterator_traits.h>
0019 #include <__iterator/prev.h>
0020 #include <__memory/pointer_traits.h>
0021 #include <__ranges/access.h>
0022 #include <__ranges/concepts.h>
0023 #include <__ranges/empty.h>
0024 #include <__ranges/size.h>
0025 #include <__type_traits/is_class.h>
0026 #include <__type_traits/make_unsigned.h>
0027 #include <__type_traits/remove_cv.h>
0028
0029 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0030 #  pragma GCC system_header
0031 #endif
0032
0033 _LIBCPP_BEGIN_NAMESPACE_STD
0034
0035 #if _LIBCPP_STD_VER >= 20
0036
0037 namespace ranges {
0038
0039 template <class _Derived>
0040   requires is_class_v<_Derived> && same_as<_Derived, remove_cv_t<_Derived>>
0041 class view_interface {
0042   _LIBCPP_HIDE_FROM_ABI constexpr _Derived& __derived() noexcept {
0043     static_assert(sizeof(_Derived) && derived_from<_Derived, view_interface> && view<_Derived>);
0044     return static_cast<_Derived&>(*this);
0045   }
0046
0047   _LIBCPP_HIDE_FROM_ABI constexpr _Derived const& __derived() const noexcept {
0048     static_assert(sizeof(_Derived) && derived_from<_Derived, view_interface> && view<_Derived>);
0049     return static_cast<_Derived const&>(*this);
0050   }
0051
0052 public:
0053   template <class _D2 = _Derived>
0054   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool empty()
0055     requires sized_range<_D2> || forward_range<_D2>
0056   {
0057     if constexpr (sized_range<_D2>) {
0058       return ranges::size(__derived()) == 0;
0059     } else {
0060       return ranges::begin(__derived()) == ranges::end(__derived());
0061     }
0062   }
0063
0064   template <class _D2 = _Derived>
0065   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool empty() const
0066     requires sized_range<const _D2> || forward_range<const _D2>
0067   {
0068     if constexpr (sized_range<const _D2>) {
0069       return ranges::size(__derived()) == 0;
0070     } else {
0071       return ranges::begin(__derived()) == ranges::end(__derived());
0072     }
0073   }
0074
0075   template <class _D2 = _Derived>
0076   _LIBCPP_HIDE_FROM_ABI constexpr explicit operator bool()
0077     requires requires(_D2& __t) { ranges::empty(__t); }
0078   {
0079     return !ranges::empty(__derived());
0080   }
0081
0082   template <class _D2 = _Derived>
0083   _LIBCPP_HIDE_FROM_ABI constexpr explicit operator bool() const
0084     requires requires(const _D2& __t) { ranges::empty(__t); }
0085   {
0086     return !ranges::empty(__derived());
0087   }
0088
0089   template <class _D2 = _Derived>
0090   _LIBCPP_HIDE_FROM_ABI constexpr auto data()
0091     requires contiguous_iterator<iterator_t<_D2>>
0092   {
0093     return std::to_address(ranges::begin(__derived()));
0094   }
0095
0096   template <class _D2 = _Derived>
0097   _LIBCPP_HIDE_FROM_ABI constexpr auto data() const
0098     requires range<const _D2> && contiguous_iterator<iterator_t<const _D2>>
0099   {
0100     return std::to_address(ranges::begin(__derived()));
0101   }
0102
0103   template <class _D2 = _Derived>
0104   _LIBCPP_HIDE_FROM_ABI constexpr auto size()
0105     requires forward_range<_D2> && sized_sentinel_for<sentinel_t<_D2>, iterator_t<_D2>>
0106   {
0107     return std::__to_unsigned_like(ranges::end(__derived()) - ranges::begin(__derived()));
0108   }
0109
0110   template <class _D2 = _Derived>
0111   _LIBCPP_HIDE_FROM_ABI constexpr auto size() const
0112     requires forward_range<const _D2> && sized_sentinel_for<sentinel_t<const _D2>, iterator_t<const _D2>>
0113   {
0114     return std::__to_unsigned_like(ranges::end(__derived()) - ranges::begin(__derived()));
0115   }
0116
0117   template <class _D2 = _Derived>
0118   _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) front()
0119     requires forward_range<_D2>
0120   {
0121     _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
0122         !empty(), "Precondition `!empty()` not satisfied. `.front()` called on an empty view.");
0123     return *ranges::begin(__derived());
0124   }
0125
0126   template <class _D2 = _Derived>
0127   _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) front() const
0128     requires forward_range<const _D2>
0129   {
0130     _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
0131         !empty(), "Precondition `!empty()` not satisfied. `.front()` called on an empty view.");
0132     return *ranges::begin(__derived());
0133   }
0134
0135   template <class _D2 = _Derived>
0136   _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) back()
0137     requires bidirectional_range<_D2> && common_range<_D2>
0138   {
0139     _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
0140         !empty(), "Precondition `!empty()` not satisfied. `.back()` called on an empty view.");
0141     return *ranges::prev(ranges::end(__derived()));
0142   }
0143
0144   template <class _D2 = _Derived>
0145   _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) back() const
0146     requires bidirectional_range<const _D2> && common_range<const _D2>
0147   {
0148     _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
0149         !empty(), "Precondition `!empty()` not satisfied. `.back()` called on an empty view.");
0150     return *ranges::prev(ranges::end(__derived()));
0151   }
0152
0153   template <random_access_range _RARange = _Derived>
0154   _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) operator[](range_difference_t<_RARange> __index) {
0155     return ranges::begin(__derived())[__index];
0156   }
0157
0158   template <random_access_range _RARange = const _Derived>
0159   _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) operator[](range_difference_t<_RARange> __index) const {
0160     return ranges::begin(__derived())[__index];
0161   }
0162 };
0163
0164 } // namespace ranges
0165
0166 #endif // _LIBCPP_STD_VER >= 20
0167
0168 _LIBCPP_END_NAMESPACE_STD
0169
0170 #endif // _LIBCPP___RANGES_VIEW_INTERFACE_H