__cxx03/__ranges/size.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___CXX03___RANGES_SIZE_H
0011 #define _LIBCPP___CXX03___RANGES_SIZE_H
0012
0013 #include <__cxx03/__concepts/arithmetic.h>
0014 #include <__cxx03/__concepts/class_or_enum.h>
0015 #include <__cxx03/__config>
0016 #include <__cxx03/__iterator/concepts.h>
0017 #include <__cxx03/__iterator/iterator_traits.h>
0018 #include <__cxx03/__ranges/access.h>
0019 #include <__cxx03/__type_traits/decay.h>
0020 #include <__cxx03/__type_traits/make_signed.h>
0021 #include <__cxx03/__type_traits/make_unsigned.h>
0022 #include <__cxx03/__type_traits/remove_cvref.h>
0023 #include <__cxx03/__utility/auto_cast.h>
0024 #include <__cxx03/__utility/declval.h>
0025 #include <__cxx03/cstddef>
0026
0027 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0028 #  pragma GCC system_header
0029 #endif
0030
0031 _LIBCPP_BEGIN_NAMESPACE_STD
0032
0033 #if _LIBCPP_STD_VER >= 20
0034
0035 namespace ranges {
0036 template <class>
0037 inline constexpr bool disable_sized_range = false;
0038 } // namespace ranges
0039
0040 // [range.prim.size]
0041
0042 namespace ranges {
0043 namespace __size {
0044 void size() = delete;
0045
0046 template <class _Tp>
0047 concept __size_enabled = !disable_sized_range<remove_cvref_t<_Tp>>;
0048
0049 template <class _Tp>
0050 concept __member_size = __size_enabled<_Tp> && requires(_Tp&& __t) {
0051   { _LIBCPP_AUTO_CAST(__t.size()) } -> __integer_like;
0052 };
0053
0054 template <class _Tp>
0055 concept __unqualified_size =
0056     __size_enabled<_Tp> && !__member_size<_Tp> && __class_or_enum<remove_cvref_t<_Tp>> && requires(_Tp&& __t) {
0057       { _LIBCPP_AUTO_CAST(size(__t)) } -> __integer_like;
0058     };
0059
0060 template <class _Tp>
0061 concept __difference =
0062     !__member_size<_Tp> && !__unqualified_size<_Tp> && __class_or_enum<remove_cvref_t<_Tp>> && requires(_Tp&& __t) {
0063       { ranges::begin(__t) } -> forward_iterator;
0064       { ranges::end(__t) } -> sized_sentinel_for<decltype(ranges::begin(std::declval<_Tp>()))>;
0065     };
0066
0067 struct __fn {
0068   // `[range.prim.size]`: the array case (for rvalues).
0069   template <class _Tp, size_t _Sz>
0070   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr size_t operator()(_Tp (&&)[_Sz]) const noexcept {
0071     return _Sz;
0072   }
0073
0074   // `[range.prim.size]`: the array case (for lvalues).
0075   template <class _Tp, size_t _Sz>
0076   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr size_t operator()(_Tp (&)[_Sz]) const noexcept {
0077     return _Sz;
0078   }
0079
0080   // `[range.prim.size]`: `auto(t.size())` is a valid expression.
0081   template <__member_size _Tp>
0082   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr __integer_like auto operator()(_Tp&& __t) const
0083       noexcept(noexcept(_LIBCPP_AUTO_CAST(__t.size()))) {
0084     return _LIBCPP_AUTO_CAST(__t.size());
0085   }
0086
0087   // `[range.prim.size]`: `auto(size(t))` is a valid expression.
0088   template <__unqualified_size _Tp>
0089   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr __integer_like auto operator()(_Tp&& __t) const
0090       noexcept(noexcept(_LIBCPP_AUTO_CAST(size(__t)))) {
0091     return _LIBCPP_AUTO_CAST(size(__t));
0092   }
0093
0094   // [range.prim.size]: the `to-unsigned-like` case.
0095   template <__difference _Tp>
0096   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const
0097       noexcept(noexcept(std::__to_unsigned_like(ranges::end(__t) - ranges::begin(__t))))
0098           -> decltype(std::__to_unsigned_like(ranges::end(__t) - ranges::begin(__t))) {
0099     return std::__to_unsigned_like(ranges::end(__t) - ranges::begin(__t));
0100   }
0101 };
0102
0103 } // namespace __size
0104
0105 inline namespace __cpo {
0106 inline constexpr auto size = __size::__fn{};
0107 } // namespace __cpo
0108 } // namespace ranges
0109
0110 // [range.prim.ssize]
0111
0112 namespace ranges {
0113 namespace __ssize {
0114 struct __fn {
0115   template <class _Tp>
0116     requires requires(_Tp&& __t) { ranges::size(__t); }
0117   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr integral auto operator()(_Tp&& __t) const
0118       noexcept(noexcept(ranges::size(__t))) {
0119     using _Signed = make_signed_t<decltype(ranges::size(__t))>;
0120     if constexpr (sizeof(ptrdiff_t) > sizeof(_Signed))
0121       return static_cast<ptrdiff_t>(ranges::size(__t));
0122     else
0123       return static_cast<_Signed>(ranges::size(__t));
0124   }
0125 };
0126 } // namespace __ssize
0127
0128 inline namespace __cpo {
0129 inline constexpr auto ssize = __ssize::__fn{};
0130 } // namespace __cpo
0131 } // namespace ranges
0132
0133 #endif // _LIBCPP_STD_VER >= 20
0134
0135 _LIBCPP_END_NAMESPACE_STD
0136
0137 #endif // _LIBCPP___CXX03___RANGES_SIZE_H