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 <__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
  36 namespace ranges {
  37 template <class>
  38 inline constexpr bool disable_sized_range = false;
  39 } // namespace ranges
  40
  41 // [range.prim.size]
  42
  43 namespace ranges {
  44 namespace __size {
  45 void size() = 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 = __size_enabled<_Tp> && requires(_Tp&& __t) {
  52   { _LIBCPP_AUTO_CAST(__t.size()) } -> __integer_like;
  53 };
  54
  55 template <class _Tp>
  56 concept __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
  61 template <class _Tp>
  62 concept __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
  68 struct __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
 106 inline namespace __cpo {
 107 inline constexpr auto size = __size::__fn{};
 108 } // namespace __cpo
 109 } // namespace ranges
 110
 111 // [range.prim.ssize]
 112
 113 namespace ranges {
 114 namespace __ssize {
 115 struct __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
 129 inline namespace __cpo {
 130 inline 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