v1/__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___RANGES_SIZE_H
0011 #define _LIBCPP___RANGES_SIZE_H
0012
0013 #include <__concepts/arithmetic.h>
0014 #include <__concepts/class_or_enum.h>
0015 #include <__config>
0016 #include <__cstddef/ptrdiff_t.h>
0017 #include <__cstddef/size_t.h>
0018 #include <__iterator/concepts.h>
0019 #include <__iterator/iterator_traits.h>
0020 #include <__ranges/access.h>
0021 #include <__type_traits/decay.h>
0022 #include <__type_traits/make_signed.h>
0023 #include <__type_traits/make_unsigned.h>
0024 #include <__type_traits/remove_cvref.h>
0025 #include <__utility/auto_cast.h>
0026 #include <__utility/declval.h>
0027
0028 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0029 #  pragma GCC system_header
0030 #endif
0031
0032 _LIBCPP_BEGIN_NAMESPACE_STD
0033
0034 #if _LIBCPP_STD_VER >= 20
0035
0036 namespace ranges {
0037 template <class>
0038 inline constexpr bool disable_sized_range = false;
0039 } // namespace ranges
0040
0041 // [range.prim.size]
0042
0043 namespace ranges {
0044 namespace __size {
0045 void size() = delete;
0046
0047 template <class _Tp>
0048 concept __size_enabled = !disable_sized_range<remove_cvref_t<_Tp>>;
0049
0050 template <class _Tp>
0051 concept __member_size = __size_enabled<_Tp> && requires(_Tp&& __t) {
0052   { _LIBCPP_AUTO_CAST(__t.size()) } -> __integer_like;
0053 };
0054
0055 template <class _Tp>
0056 concept __unqualified_size =
0057     __size_enabled<_Tp> && !__member_size<_Tp> && __class_or_enum<remove_cvref_t<_Tp>> && requires(_Tp&& __t) {
0058       { _LIBCPP_AUTO_CAST(size(__t)) } -> __integer_like;
0059     };
0060
0061 template <class _Tp>
0062 concept __difference =
0063     !__member_size<_Tp> && !__unqualified_size<_Tp> && __class_or_enum<remove_cvref_t<_Tp>> && requires(_Tp&& __t) {
0064       { ranges::begin(__t) } -> forward_iterator;
0065       { ranges::end(__t) } -> sized_sentinel_for<decltype(ranges::begin(std::declval<_Tp>()))>;
0066     };
0067
0068 struct __fn {
0069   // `[range.prim.size]`: the array case (for rvalues).
0070   template <class _Tp, size_t _Sz>
0071   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr size_t operator()(_Tp (&&)[_Sz]) const noexcept {
0072     return _Sz;
0073   }
0074
0075   // `[range.prim.size]`: the array case (for lvalues).
0076   template <class _Tp, size_t _Sz>
0077   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr size_t operator()(_Tp (&)[_Sz]) const noexcept {
0078     return _Sz;
0079   }
0080
0081   // `[range.prim.size]`: `auto(t.size())` is a valid expression.
0082   template <__member_size _Tp>
0083   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr __integer_like auto operator()(_Tp&& __t) const
0084       noexcept(noexcept(_LIBCPP_AUTO_CAST(__t.size()))) {
0085     return _LIBCPP_AUTO_CAST(__t.size());
0086   }
0087
0088   // `[range.prim.size]`: `auto(size(t))` is a valid expression.
0089   template <__unqualified_size _Tp>
0090   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr __integer_like auto operator()(_Tp&& __t) const
0091       noexcept(noexcept(_LIBCPP_AUTO_CAST(size(__t)))) {
0092     return _LIBCPP_AUTO_CAST(size(__t));
0093   }
0094
0095   // [range.prim.size]: the `to-unsigned-like` case.
0096   template <__difference _Tp>
0097   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const
0098       noexcept(noexcept(std::__to_unsigned_like(ranges::end(__t) - ranges::begin(__t))))
0099           -> decltype(std::__to_unsigned_like(ranges::end(__t) - ranges::begin(__t))) {
0100     return std::__to_unsigned_like(ranges::end(__t) - ranges::begin(__t));
0101   }
0102 };
0103
0104 } // namespace __size
0105
0106 inline namespace __cpo {
0107 inline constexpr auto size = __size::__fn{};
0108 } // namespace __cpo
0109 } // namespace ranges
0110
0111 // [range.prim.ssize]
0112
0113 namespace ranges {
0114 namespace __ssize {
0115 struct __fn {
0116   template <class _Tp>
0117     requires requires(_Tp&& __t) { ranges::size(__t); }
0118   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr integral auto operator()(_Tp&& __t) const
0119       noexcept(noexcept(ranges::size(__t))) {
0120     using _Signed = make_signed_t<decltype(ranges::size(__t))>;
0121     if constexpr (sizeof(ptrdiff_t) > sizeof(_Signed))
0122       return static_cast<ptrdiff_t>(ranges::size(__t));
0123     else
0124       return static_cast<_Signed>(ranges::size(__t));
0125   }
0126 };
0127 } // namespace __ssize
0128
0129 inline namespace __cpo {
0130 inline constexpr auto ssize = __ssize::__fn{};
0131 } // namespace __cpo
0132 } // namespace ranges
0133
0134 #endif // _LIBCPP_STD_VER >= 20
0135
0136 _LIBCPP_END_NAMESPACE_STD
0137
0138 #endif // _LIBCPP___RANGES_SIZE_H