libcxx/include/__ranges/size.h

   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 <__iterator/concepts.h>
  17 #include <__iterator/iterator_traits.h>
  18 #include <__ranges/access.h>
  19 #include <__type_traits/decay.h>
  20 #include <__type_traits/make_signed.h>
  21 #include <__type_traits/make_unsigned.h>
  22 #include <__type_traits/remove_cvref.h>
  23 #include <__utility/auto_cast.h>
  24 #include <__utility/declval.h>
  25 #include <cstddef>
  26
  27 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  28 #  pragma GCC system_header
  29 #endif
  30
  31 _LIBCPP_BEGIN_NAMESPACE_STD
  32
  33 #if _LIBCPP_STD_VER >= 20
  34
  35 namespace ranges {
  36   template<class>
  37   inline constexpr bool disable_sized_range = false;
  38 } // namespace ranges
  39
  40 // [range.prim.size]
  41
  42 namespace ranges {
  43 namespace __size {
  44 void size(auto&) = delete;
  45 void size(const auto&) = delete;
  46
  47 template <class _Tp>
  48 concept __size_enabled = !disable_sized_range<remove_cvref_t<_Tp>>;
  49
  50 template <class _Tp>
  51 concept __member_size =
  52   __size_enabled<_Tp> &&
  53   __workaround_52970<_Tp> &&
  54   requires(_Tp&& __t) {
  55     { _LIBCPP_AUTO_CAST(__t.size()) } -> __integer_like;
  56   };
  57
  58 template <class _Tp>
  59 concept __unqualified_size =
  60   __size_enabled<_Tp> &&
  61   !__member_size<_Tp> &&
  62   __class_or_enum<remove_cvref_t<_Tp>> &&
  63   requires(_Tp&& __t) {
  64     { _LIBCPP_AUTO_CAST(size(__t)) } -> __integer_like;
  65   };
  66
  67 template <class _Tp>
  68 concept __difference =
  69   !__member_size<_Tp> &&
  70   !__unqualified_size<_Tp> &&
  71   __class_or_enum<remove_cvref_t<_Tp>> &&
  72   requires(_Tp&& __t) {
  73     { ranges::begin(__t) } -> forward_iterator;
  74     { ranges::end(__t) } -> sized_sentinel_for<decltype(ranges::begin(std::declval<_Tp>()))>;
  75   };
  76
  77 struct __fn {
  78
  79   // `[range.prim.size]`: the array case (for rvalues).
  80   template <class _Tp, size_t _Sz>
  81   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr size_t operator()(_Tp (&&)[_Sz]) const noexcept {
  82     return _Sz;
  83   }
  84
  85   // `[range.prim.size]`: the array case (for lvalues).
  86   template <class _Tp, size_t _Sz>
  87   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr size_t operator()(_Tp (&)[_Sz]) const noexcept {
  88     return _Sz;
  89   }
  90
  91   // `[range.prim.size]`: `auto(t.size())` is a valid expression.
  92   template <__member_size _Tp>
  93   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr __integer_like auto operator()(_Tp&& __t) const
  94       noexcept(noexcept(_LIBCPP_AUTO_CAST(__t.size()))) {
  95     return _LIBCPP_AUTO_CAST(__t.size());
  96   }
  97
  98   // `[range.prim.size]`: `auto(size(t))` is a valid expression.
  99   template <__unqualified_size _Tp>
 100   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr __integer_like auto operator()(_Tp&& __t) const
 101       noexcept(noexcept(_LIBCPP_AUTO_CAST(size(__t)))) {
 102     return _LIBCPP_AUTO_CAST(size(__t));
 103   }
 104
 105   // [range.prim.size]: the `to-unsigned-like` case.
 106   template <__difference _Tp>
 107   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const
 108     noexcept(noexcept(std::__to_unsigned_like(ranges::end(__t) - ranges::begin(__t))))
 109     -> decltype(      std::__to_unsigned_like(ranges::end(__t) - ranges::begin(__t)))
 110     { return          std::__to_unsigned_like(ranges::end(__t) - ranges::begin(__t));
 111   }
 112 };
 113
 114 } // namespace __size
 115
 116 inline namespace __cpo {
 117   inline constexpr auto size = __size::__fn{};
 118 } // namespace __cpo
 119 } // namespace ranges
 120
 121 // [range.prim.ssize]
 122
 123 namespace ranges {
 124 namespace __ssize {
 125 struct __fn {
 126   template<class _Tp>
 127     requires requires (_Tp&& __t) { ranges::size(__t); }
 128   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr integral auto operator()(_Tp&& __t) const
 129     noexcept(noexcept(ranges::size(__t))) {
 130     using _Signed = make_signed_t<decltype(ranges::size(__t))>;
 131     if constexpr (sizeof(ptrdiff_t) > sizeof(_Signed))
 132       return static_cast<ptrdiff_t>(ranges::size(__t));
 133     else
 134       return static_cast<_Signed>(ranges::size(__t));
 135   }
 136 };
 137 } // namespace __ssize
 138
 139 inline namespace __cpo {
 140   inline constexpr auto ssize = __ssize::__fn{};
 141 } // namespace __cpo
 142 } // namespace ranges
 143
 144 #endif // _LIBCPP_STD_VER >= 20
 145
 146 _LIBCPP_END_NAMESPACE_STD
 147
 148 #endif // _LIBCPP___RANGES_SIZE_H