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 <__cstddef/size_t.h>
16#include <__iterator/concepts.h>
17#include <__iterator/counted_iterator.h>
18#include <__iterator/default_sentinel.h>
19#include <__iterator/incrementable_traits.h>
20#include <__iterator/iterator_traits.h>
21#include <__memory/pointer_traits.h>
22#include <__ranges/subrange.h>
23#include <__type_traits/decay.h>
24#include <__utility/forward.h>
25#include <__utility/move.h>
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
39namespace ranges::views {
40
41namespace __counted {
42
43struct __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 __go(_It __it, iter_difference_t<_It> __count) noexcept(
55      noexcept(subrange(__it, __it + __count))) -> decltype(subrange(__it, __it + __count)) {
56    return subrange(__it, __it + __count);
57  }
58
59  template <class _It>
60  _LIBCPP_HIDE_FROM_ABI static constexpr auto __go(_It __it, iter_difference_t<_It> __count) noexcept(
61      noexcept(subrange(counted_iterator(std::move(__it), __count), default_sentinel)))
62      -> decltype(subrange(counted_iterator(std::move(__it), __count), default_sentinel)) {
63    return subrange(counted_iterator(std::move(__it), __count), default_sentinel);
64  }
65
66  template <class _It, convertible_to<iter_difference_t<_It>> _Diff>
67    requires input_or_output_iterator<decay_t<_It>>
68  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_It&& __it, _Diff&& __count) const
69      noexcept(noexcept(__go(std::forward<_It>(__it), std::forward<_Diff>(__count))))
70          -> decltype(__go(std::forward<_It>(__it), std::forward<_Diff>(__count))) {
71    return __go(std::forward<_It>(__it), std::forward<_Diff>(__count));
72  }
73};
74
75} // namespace __counted
76
77inline namespace __cpo {
78inline constexpr auto counted = __counted::__fn{};
79} // namespace __cpo
80
81} // namespace ranges::views
82
83#endif // _LIBCPP_STD_VER >= 20
84
85_LIBCPP_END_NAMESPACE_STD
86
87_LIBCPP_POP_MACROS
88
89#endif // _LIBCPP___RANGES_COUNTED_H