llvm-project/libcxx/include/__ranges/counted.h

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// -*- C++ -*-
//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#ifndef _LIBCPP___RANGES_COUNTED_H
#define _LIBCPP___RANGES_COUNTED_H
#include <__concepts/convertible_to.h>
#include <__config>
#include <__iterator/concepts.h>
#include <__iterator/counted_iterator.h>
#include <__iterator/default_sentinel.h>
#include <__iterator/incrementable_traits.h>
#include <__iterator/iterator_traits.h>
#include <__memory/pointer_traits.h>
#include <__ranges/subrange.h>
#include <__utility/forward.h>
#include <__utility/move.h>
#include <span>
#include <type_traits>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
#endif
_LIBCPP_BEGIN_NAMESPACE_STD
#if !defined(_LIBCPP_HAS_NO_CONCEPTS) && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
namespace ranges::views {
namespace __counted {
struct __fn {
template<contiguous_iterator _It>
_LIBCPP_HIDE_FROM_ABI
static constexpr auto __go(_It __it, iter_difference_t<_It> __count)
noexcept(noexcept(span(std::to_address(__it), static_cast<size_t>(__count))))
// Deliberately omit return-type SFINAE, because to_address is not SFINAE-friendly
{ return span(std::to_address(__it), static_cast<size_t>(__count)); }
template<random_access_iterator _It>
_LIBCPP_HIDE_FROM_ABI
static constexpr auto __go(_It __it, iter_difference_t<_It> __count)
noexcept(noexcept(subrange(__it, __it + __count)))
-> decltype( subrange(__it, __it + __count))
{ return subrange(__it, __it + __count); }
template<class _It>
_LIBCPP_HIDE_FROM_ABI
static constexpr auto __go(_It __it, iter_difference_t<_It> __count)
noexcept(noexcept(subrange(counted_iterator(std::move(__it), __count), default_sentinel)))
-> decltype( subrange(counted_iterator(std::move(__it), __count), default_sentinel))
{ return subrange(counted_iterator(std::move(__it), __count), default_sentinel); }
template<class _It, convertible_to<iter_difference_t<_It>> _Diff>
requires input_or_output_iterator<decay_t<_It>>
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI
constexpr auto operator()(_It&& __it, _Diff&& __count) const
noexcept(noexcept(__go(std::forward<_It>(__it), std::forward<_Diff>(__count))))
-> decltype( __go(std::forward<_It>(__it), std::forward<_Diff>(__count)))
{ return __go(std::forward<_It>(__it), std::forward<_Diff>(__count)); }
};
} // namespace __counted
inline namespace __cpo {
inline constexpr auto counted = __counted::__fn{};
} // namespace __cpo
} // namespace ranges::views
#endif // !defined(_LIBCPP_HAS_NO_CONCEPTS) && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
_LIBCPP_END_NAMESPACE_STD
#endif // _LIBCPP___RANGES_COUNTED_H