include/__ranges/size.h

// -*- C++ -*-
//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP___RANGES_SIZE_H
#define _LIBCPP___RANGES_SIZE_H

#include <__concepts/arithmetic.h>
#include <__concepts/class_or_enum.h>
#include <__config>
#include <__iterator/concepts.h>
#include <__iterator/iterator_traits.h>
#include <__ranges/access.h>
#include <__type_traits/decay.h>
#include <__type_traits/make_signed.h>
#include <__type_traits/make_unsigned.h>
#include <__type_traits/remove_cvref.h>
#include <__utility/auto_cast.h>
#include <__utility/declval.h>
#include <cstddef>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#  pragma GCC system_header
#endif

_LIBCPP_BEGIN_NAMESPACE_STD

#if _LIBCPP_STD_VER >= 20

namespace ranges {
template <class>
inline constexpr bool disable_sized_range = false;
} // namespace ranges

// [range.prim.size]

namespace ranges {
namespace __size {
void size() = delete;

template <class _Tp>
concept __size_enabled = !disable_sized_range<remove_cvref_t<_Tp>>;

template <class _Tp>
concept __member_size = __size_enabled<_Tp> && requires(_Tp&& __t) {
  { _LIBCPP_AUTO_CAST(__t.size()) } -> __integer_like;
};

template <class _Tp>
concept __unqualified_size =
    __size_enabled<_Tp> && !__member_size<_Tp> && __class_or_enum<remove_cvref_t<_Tp>> && requires(_Tp&& __t) {
      { _LIBCPP_AUTO_CAST(size(__t)) } -> __integer_like;
    };

template <class _Tp>
concept __difference =
    !__member_size<_Tp> && !__unqualified_size<_Tp> && __class_or_enum<remove_cvref_t<_Tp>> && requires(_Tp&& __t) {
      { ranges::begin(__t) } -> forward_iterator;
      { ranges::end(__t) } -> sized_sentinel_for<decltype(ranges::begin(std::declval<_Tp>()))>;
    };

struct __fn {
  // `[range.prim.size]`: the array case (for rvalues).
  template <class _Tp, size_t _Sz>
  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr size_t operator()(_Tp (&&)[_Sz]) const noexcept {
    return _Sz;
  }

  // `[range.prim.size]`: the array case (for lvalues).
  template <class _Tp, size_t _Sz>
  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr size_t operator()(_Tp (&)[_Sz]) const noexcept {
    return _Sz;
  }

  // `[range.prim.size]`: `auto(t.size())` is a valid expression.
  template <__member_size _Tp>
  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr __integer_like auto operator()(_Tp&& __t) const
      noexcept(noexcept(_LIBCPP_AUTO_CAST(__t.size()))) {
    return _LIBCPP_AUTO_CAST(__t.size());
  }

  // `[range.prim.size]`: `auto(size(t))` is a valid expression.
  template <__unqualified_size _Tp>
  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr __integer_like auto operator()(_Tp&& __t) const
      noexcept(noexcept(_LIBCPP_AUTO_CAST(size(__t)))) {
    return _LIBCPP_AUTO_CAST(size(__t));
  }

  // [range.prim.size]: the `to-unsigned-like` case.
  template <__difference _Tp>
  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const
      noexcept(noexcept(std::__to_unsigned_like(ranges::end(__t) - ranges::begin(__t))))
          -> decltype(std::__to_unsigned_like(ranges::end(__t) - ranges::begin(__t))) {
    return std::__to_unsigned_like(ranges::end(__t) - ranges::begin(__t));
  }
};

} // namespace __size

inline namespace __cpo {
inline constexpr auto size = __size::__fn{};
} // namespace __cpo
} // namespace ranges

// [range.prim.ssize]

namespace ranges {
namespace __ssize {
struct __fn {
  template <class _Tp>
    requires requires(_Tp&& __t) { ranges::size(__t); }
  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr integral auto operator()(_Tp&& __t) const
      noexcept(noexcept(ranges::size(__t))) {
    using _Signed = make_signed_t<decltype(ranges::size(__t))>;
    if constexpr (sizeof(ptrdiff_t) > sizeof(_Signed))
      return static_cast<ptrdiff_t>(ranges::size(__t));
    else
      return static_cast<_Signed>(ranges::size(__t));
  }
};
} // namespace __ssize

inline namespace __cpo {
inline constexpr auto ssize = __ssize::__fn{};
} // namespace __cpo
} // namespace ranges

#endif // _LIBCPP_STD_VER >= 20

_LIBCPP_END_NAMESPACE_STD

#endif // _LIBCPP___RANGES_SIZE_H