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() = delete;
  45
  46 template <class _Tp>
  47 concept __size_enabled = !disable_sized_range<remove_cvref_t<_Tp>>;
  48
  49 template <class _Tp>
  50 concept __member_size = __size_enabled<_Tp> && requires(_Tp&& __t) {
  51   { _LIBCPP_AUTO_CAST(__t.size()) } -> __integer_like;
  52 };
  53
  54 template <class _Tp>
  55 concept __unqualified_size =
  56     __size_enabled<_Tp> && !__member_size<_Tp> && __class_or_enum<remove_cvref_t<_Tp>> && requires(_Tp&& __t) {
  57       { _LIBCPP_AUTO_CAST(size(__t)) } -> __integer_like;
  58     };
  59
  60 template <class _Tp>
  61 concept __difference =
  62     !__member_size<_Tp> && !__unqualified_size<_Tp> && __class_or_enum<remove_cvref_t<_Tp>> && requires(_Tp&& __t) {
  63       { ranges::begin(__t) } -> forward_iterator;
  64       { ranges::end(__t) } -> sized_sentinel_for<decltype(ranges::begin(std::declval<_Tp>()))>;
  65     };
  66
  67 struct __fn {
  68   // `[range.prim.size]`: the array case (for rvalues).
  69   template <class _Tp, size_t _Sz>
  70   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr size_t operator()(_Tp (&&)[_Sz]) const noexcept {
  71     return _Sz;
  72   }
  73
  74   // `[range.prim.size]`: the array case (for lvalues).
  75   template <class _Tp, size_t _Sz>
  76   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr size_t operator()(_Tp (&)[_Sz]) const noexcept {
  77     return _Sz;
  78   }
  79
  80   // `[range.prim.size]`: `auto(t.size())` is a valid expression.
  81   template <__member_size _Tp>
  82   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr __integer_like auto operator()(_Tp&& __t) const
  83       noexcept(noexcept(_LIBCPP_AUTO_CAST(__t.size()))) {
  84     return _LIBCPP_AUTO_CAST(__t.size());
  85   }
  86
  87   // `[range.prim.size]`: `auto(size(t))` is a valid expression.
  88   template <__unqualified_size _Tp>
  89   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr __integer_like auto operator()(_Tp&& __t) const
  90       noexcept(noexcept(_LIBCPP_AUTO_CAST(size(__t)))) {
  91     return _LIBCPP_AUTO_CAST(size(__t));
  92   }
  93
  94   // [range.prim.size]: the `to-unsigned-like` case.
  95   template <__difference _Tp>
  96   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const
  97       noexcept(noexcept(std::__to_unsigned_like(ranges::end(__t) - ranges::begin(__t))))
  98           -> decltype(std::__to_unsigned_like(ranges::end(__t) - ranges::begin(__t))) {
  99     return std::__to_unsigned_like(ranges::end(__t) - ranges::begin(__t));
 100   }
 101 };
 102
 103 } // namespace __size
 104
 105 inline namespace __cpo {
 106 inline constexpr auto size = __size::__fn{};
 107 } // namespace __cpo
 108 } // namespace ranges
 109
 110 // [range.prim.ssize]
 111
 112 namespace ranges {
 113 namespace __ssize {
 114 struct __fn {
 115   template <class _Tp>
 116     requires requires(_Tp&& __t) { ranges::size(__t); }
 117   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr integral auto operator()(_Tp&& __t) const
 118       noexcept(noexcept(ranges::size(__t))) {
 119     using _Signed = make_signed_t<decltype(ranges::size(__t))>;
 120     if constexpr (sizeof(ptrdiff_t) > sizeof(_Signed))
 121       return static_cast<ptrdiff_t>(ranges::size(__t));
 122     else
 123       return static_cast<_Signed>(ranges::size(__t));
 124   }
 125 };
 126 } // namespace __ssize
 127
 128 inline namespace __cpo {
 129 inline constexpr auto ssize = __ssize::__fn{};
 130 } // namespace __cpo
 131 } // namespace ranges
 132
 133 #endif // _LIBCPP_STD_VER >= 20
 134
 135 _LIBCPP_END_NAMESPACE_STD
 136
 137 #endif // _LIBCPP___RANGES_SIZE_H