| // -*- 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 |