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_PUSH_MACROS 33 #include <__undef_macros> 34 35 _LIBCPP_BEGIN_NAMESPACE_STD 36 37 #if _LIBCPP_STD_VER >= 20 38 39 namespace ranges::views { 40 41 namespace __counted { 42 43 struct __fn { 44 template <contiguous_iterator _It> 45 _LIBCPP_HIDE_FROM_ABI static constexpr auto 46 __go(_It __it, 47 iter_difference_t<_It> __count) noexcept(noexcept(span(std::to_address(__it), static_cast<size_t>(__count)))) 48 // Deliberately omit return-type SFINAE, because to_address is not SFINAE-friendly 49 { 50 return span(std::to_address(__it), static_cast<size_t>(__count)); 51 } 52 53 template <random_access_iterator _It> 54 _LIBCPP_HIDE_FROM_ABI static constexpr auto 55 __go(_It __it, iter_difference_t<_It> __count) noexcept(noexcept(subrange(__it, __it + __count))) 56 -> decltype(subrange(__it, __it + __count)) { 57 return subrange(__it, __it + __count); 58 } 59 60 template <class _It> 61 _LIBCPP_HIDE_FROM_ABI static constexpr auto __go(_It __it, iter_difference_t<_It> __count) noexcept( 62 noexcept(subrange(counted_iterator(std::move(__it), __count), default_sentinel))) 63 -> decltype(subrange(counted_iterator(std::move(__it), __count), default_sentinel)) { 64 return subrange(counted_iterator(std::move(__it), __count), default_sentinel); 65 } 66 67 template <class _It, convertible_to<iter_difference_t<_It>> _Diff> 68 requires input_or_output_iterator<decay_t<_It>> 69 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_It&& __it, _Diff&& __count) const 70 noexcept(noexcept(__go(std::forward<_It>(__it), std::forward<_Diff>(__count)))) 71 -> decltype(__go(std::forward<_It>(__it), std::forward<_Diff>(__count))) { 72 return __go(std::forward<_It>(__it), std::forward<_Diff>(__count)); 73 } 74 }; 75 76 } // namespace __counted 77 78 inline namespace __cpo { 79 inline constexpr auto counted = __counted::__fn{}; 80 } // namespace __cpo 81 82 } // namespace ranges::views 83 84 #endif // _LIBCPP_STD_VER >= 20 85 86 _LIBCPP_END_NAMESPACE_STD 87 88 _LIBCPP_POP_MACROS 89 90 #endif // _LIBCPP___RANGES_COUNTED_H 91