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_SIZE_H
 11#define _LIBCPP___RANGES_SIZE_H
 12
 13#include <__concepts/arithmetic.h>
 14#include <__concepts/class_or_enum.h>
 15#include <__config>
 16#include <__cstddef/ptrdiff_t.h>
 17#include <__cstddef/size_t.h>
 18#include <__iterator/concepts.h>
 19#include <__iterator/iterator_traits.h>
 20#include <__ranges/access.h>
 21#include <__type_traits/decay.h>
 22#include <__type_traits/make_signed.h>
 23#include <__type_traits/make_unsigned.h>
 24#include <__type_traits/remove_cvref.h>
 25#include <__utility/auto_cast.h>
 26#include <__utility/declval.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
 36namespace ranges {
 37template <class>
 38inline constexpr bool disable_sized_range = false;
 39} // namespace ranges
 40
 41// [range.prim.size]
 42
 43namespace ranges {
 44namespace __size {
 45void size() = delete;
 46
 47template <class _Tp>
 48concept __size_enabled = !disable_sized_range<remove_cvref_t<_Tp>>;
 49
 50template <class _Tp>
 51concept __member_size = __size_enabled<_Tp> && requires(_Tp&& __t) {
 52  { _LIBCPP_AUTO_CAST(__t.size()) } -> __integer_like;
 53};
 54
 55template <class _Tp>
 56concept __unqualified_size =
 57    __size_enabled<_Tp> && !__member_size<_Tp> && __class_or_enum<remove_cvref_t<_Tp>> && requires(_Tp&& __t) {
 58      { _LIBCPP_AUTO_CAST(size(__t)) } -> __integer_like;
 59    };
 60
 61template <class _Tp>
 62concept __difference =
 63    !__member_size<_Tp> && !__unqualified_size<_Tp> && __class_or_enum<remove_cvref_t<_Tp>> && requires(_Tp&& __t) {
 64      { ranges::begin(__t) } -> forward_iterator;
 65      { ranges::end(__t) } -> sized_sentinel_for<decltype(ranges::begin(std::declval<_Tp>()))>;
 66    };
 67
 68struct __fn {
 69  // `[range.prim.size]`: the array case (for rvalues).
 70  template <class _Tp, size_t _Sz>
 71  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr size_t operator()(_Tp (&&)[_Sz]) const noexcept {
 72    return _Sz;
 73  }
 74
 75  // `[range.prim.size]`: the array case (for lvalues).
 76  template <class _Tp, size_t _Sz>
 77  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr size_t operator()(_Tp (&)[_Sz]) const noexcept {
 78    return _Sz;
 79  }
 80
 81  // `[range.prim.size]`: `auto(t.size())` is a valid expression.
 82  template <__member_size _Tp>
 83  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr __integer_like auto operator()(_Tp&& __t) const
 84      noexcept(noexcept(_LIBCPP_AUTO_CAST(__t.size()))) {
 85    return _LIBCPP_AUTO_CAST(__t.size());
 86  }
 87
 88  // `[range.prim.size]`: `auto(size(t))` is a valid expression.
 89  template <__unqualified_size _Tp>
 90  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr __integer_like auto operator()(_Tp&& __t) const
 91      noexcept(noexcept(_LIBCPP_AUTO_CAST(size(__t)))) {
 92    return _LIBCPP_AUTO_CAST(size(__t));
 93  }
 94
 95  // [range.prim.size]: the `to-unsigned-like` case.
 96  template <__difference _Tp>
 97  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const
 98      noexcept(noexcept(std::__to_unsigned_like(ranges::end(__t) - ranges::begin(__t))))
 99          -> decltype(std::__to_unsigned_like(ranges::end(__t) - ranges::begin(__t))) {
100    return std::__to_unsigned_like(ranges::end(__t) - ranges::begin(__t));
101  }
102};
103
104} // namespace __size
105
106inline namespace __cpo {
107inline constexpr auto size = __size::__fn{};
108} // namespace __cpo
109} // namespace ranges
110
111// [range.prim.ssize]
112
113namespace ranges {
114namespace __ssize {
115struct __fn {
116  template <class _Tp>
117    requires requires(_Tp&& __t) { ranges::size(__t); }
118  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr integral auto operator()(_Tp&& __t) const
119      noexcept(noexcept(ranges::size(__t))) {
120    using _Signed = make_signed_t<decltype(ranges::size(__t))>;
121    if constexpr (sizeof(ptrdiff_t) > sizeof(_Signed))
122      return static_cast<ptrdiff_t>(ranges::size(__t));
123    else
124      return static_cast<_Signed>(ranges::size(__t));
125  }
126};
127} // namespace __ssize
128
129inline namespace __cpo {
130inline constexpr auto ssize = __ssize::__fn{};
131} // namespace __cpo
132} // namespace ranges
133
134#endif // _LIBCPP_STD_VER >= 20
135
136_LIBCPP_END_NAMESPACE_STD
137
138#endif // _LIBCPP___RANGES_SIZE_H