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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_REVERSE_VIEW_H
#define _LIBCPP___RANGES_REVERSE_VIEW_H
#include <__concepts/constructible.h>
#include <__config>
#include <__iterator/concepts.h>
#include <__iterator/next.h>
#include <__iterator/reverse_iterator.h>
#include <__ranges/access.h>
#include <__ranges/all.h>
#include <__ranges/concepts.h>
#include <__ranges/enable_borrowed_range.h>
#include <__ranges/non_propagating_cache.h>
#include <__ranges/size.h>
#include <__ranges/view_interface.h>
#include <__utility/move.h>
#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_RANGES)
namespace ranges {
template<view _View>
requires bidirectional_range<_View>
class reverse_view : public view_interface<reverse_view<_View>> {
// We cache begin() whenever ranges::next is not guaranteed O(1) to provide an
// amortized O(1) begin() method.
static constexpr bool _UseCache = !random_access_range<_View> && !common_range<_View>;
using _Cache = _If<_UseCache, __non_propagating_cache<reverse_iterator<iterator_t<_View>>>, __empty_cache>;
[[no_unique_address]] _Cache __cached_begin_ = _Cache();
[[no_unique_address]] _View __base_ = _View();
public:
_LIBCPP_HIDE_FROM_ABI
reverse_view() requires default_initializable<_View> = default;
_LIBCPP_HIDE_FROM_ABI
constexpr explicit reverse_view(_View __view) : __base_(_VSTD::move(__view)) {}
_LIBCPP_HIDE_FROM_ABI
constexpr _View base() const& requires copy_constructible<_View> { return __base_; }
_LIBCPP_HIDE_FROM_ABI
constexpr _View base() && { return _VSTD::move(__base_); }
_LIBCPP_HIDE_FROM_ABI
constexpr reverse_iterator<iterator_t<_View>> begin() {
if constexpr (_UseCache)
if (__cached_begin_.__has_value())
return *__cached_begin_;
auto __tmp = _VSTD::make_reverse_iterator(ranges::next(ranges::begin(__base_), ranges::end(__base_)));
if constexpr (_UseCache)
__cached_begin_.__emplace(__tmp);
return __tmp;
}
_LIBCPP_HIDE_FROM_ABI
constexpr reverse_iterator<iterator_t<_View>> begin() requires common_range<_View> {
return _VSTD::make_reverse_iterator(ranges::end(__base_));
}
_LIBCPP_HIDE_FROM_ABI
constexpr auto begin() const requires common_range<const _View> {
return _VSTD::make_reverse_iterator(ranges::end(__base_));
}
_LIBCPP_HIDE_FROM_ABI
constexpr reverse_iterator<iterator_t<_View>> end() {
return _VSTD::make_reverse_iterator(ranges::begin(__base_));
}
_LIBCPP_HIDE_FROM_ABI
constexpr auto end() const requires common_range<const _View> {
return _VSTD::make_reverse_iterator(ranges::begin(__base_));
}
_LIBCPP_HIDE_FROM_ABI
constexpr auto size() requires sized_range<_View> {
return ranges::size(__base_);
}
_LIBCPP_HIDE_FROM_ABI
constexpr auto size() const requires sized_range<const _View> {
return ranges::size(__base_);
}
};
template<class _Range>
reverse_view(_Range&&) -> reverse_view<views::all_t<_Range>>;
template<class _Tp>
inline constexpr bool enable_borrowed_range<reverse_view<_Tp>> = enable_borrowed_range<_Tp>;
} // namespace ranges
#endif // !defined(_LIBCPP_HAS_NO_RANGES)
_LIBCPP_END_NAMESPACE_STD
#endif // _LIBCPP___RANGES_REVERSE_VIEW_H
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