libcxx/include/__ranges/counted.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_COUNTED_H
  11 #define _LIBCPP___RANGES_COUNTED_H
  12
  13 #include <__concepts/convertible_to.h>
  14 #include <__config>
  15 #include <__iterator/concepts.h>
  16 #include <__iterator/counted_iterator.h>
  17 #include <__iterator/default_sentinel.h>
  18 #include <__iterator/incrementable_traits.h>
  19 #include <__iterator/iterator_traits.h>
  20 #include <__memory/pointer_traits.h>
  21 #include <__ranges/subrange.h>
  22 #include <__type_traits/decay.h>
  23 #include <__utility/forward.h>
  24 #include <__utility/move.h>
  25 #include <cstddef>
  26 #include <span>
  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::views {
  37
  38 namespace __counted {
  39
  40   struct __fn {
  41     template<contiguous_iterator _It>
  42     _LIBCPP_HIDE_FROM_ABI
  43     static constexpr auto __go(_It __it, iter_difference_t<_It> __count)
  44       noexcept(noexcept(span(std::to_address(__it), static_cast<size_t>(__count))))
  45       // Deliberately omit return-type SFINAE, because to_address is not SFINAE-friendly
  46       { return          span(std::to_address(__it), static_cast<size_t>(__count)); }
  47
  48     template<random_access_iterator _It>
  49     _LIBCPP_HIDE_FROM_ABI
  50     static constexpr auto __go(_It __it, iter_difference_t<_It> __count)
  51       noexcept(noexcept(subrange(__it, __it + __count)))
  52       -> decltype(      subrange(__it, __it + __count))
  53       { return          subrange(__it, __it + __count); }
  54
  55     template<class _It>
  56     _LIBCPP_HIDE_FROM_ABI
  57     static constexpr auto __go(_It __it, iter_difference_t<_It> __count)
  58       noexcept(noexcept(subrange(counted_iterator(std::move(__it), __count), default_sentinel)))
  59       -> decltype(      subrange(counted_iterator(std::move(__it), __count), default_sentinel))
  60       { return          subrange(counted_iterator(std::move(__it), __count), default_sentinel); }
  61
  62     template<class _It, convertible_to<iter_difference_t<_It>> _Diff>
  63       requires input_or_output_iterator<decay_t<_It>>
  64     [[nodiscard]] _LIBCPP_HIDE_FROM_ABI
  65     constexpr auto operator()(_It&& __it, _Diff&& __count) const
  66       noexcept(noexcept(__go(std::forward<_It>(__it), std::forward<_Diff>(__count))))
  67       -> decltype(      __go(std::forward<_It>(__it), std::forward<_Diff>(__count)))
  68       { return          __go(std::forward<_It>(__it), std::forward<_Diff>(__count)); }
  69   };
  70
  71 } // namespace __counted
  72
  73 inline namespace __cpo {
  74   inline constexpr auto counted = __counted::__fn{};
  75 } // namespace __cpo
  76
  77 } // namespace ranges::views
  78
  79 #endif // _LIBCPP_STD_VER >= 20
  80
  81 _LIBCPP_END_NAMESPACE_STD
  82
  83 #endif // _LIBCPP___RANGES_COUNTED_H