[libcxx][ranges] Add `ranges::reverse_view`.
Differential Revision: https://reviews.llvm.org/D107096
NOKEYCHECK=True
GitOrigin-RevId: 9d982c67ba01ef5fcee1e2ca946a8bd0b6747ac0
diff --git a/include/CMakeLists.txt b/include/CMakeLists.txt
index 1be2df1..765c193 100644
--- a/include/CMakeLists.txt
+++ b/include/CMakeLists.txt
@@ -199,6 +199,8 @@
__ranges/enable_view.h
__ranges/non_propagating_cache.h
__ranges/ref_view.h
+ __ranges/reverse_view.h
+ __ranges/take_view.h
__ranges/single_view.h
__ranges/size.h
__ranges/subrange.h
diff --git a/include/__ranges/reverse_view.h b/include/__ranges/reverse_view.h
new file mode 100644
index 0000000..25d3d65
--- /dev/null
+++ b/include/__ranges/reverse_view.h
@@ -0,0 +1,112 @@
+// -*- 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 <__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 <concepts>
+#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_.__set(__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
diff --git a/include/module.modulemap b/include/module.modulemap
index ee6f3c3..7f8c3bc 100644
--- a/include/module.modulemap
+++ b/include/module.modulemap
@@ -631,6 +631,7 @@
module enable_view { private header "__ranges/enable_view.h" }
module non_propagating_cache { private header "__ranges/non_propagating_cache.h" }
module ref_view { private header "__ranges/ref_view.h" }
+ module reverse_view { private header "__ranges/reverse_view.h" }
module size { private header "__ranges/size.h" }
module single_view { private header "__ranges/single_view.h" }
module subrange { private header "__ranges/subrange.h" }
diff --git a/include/ranges b/include/ranges
index cd29aee..a224313 100644
--- a/include/ranges
+++ b/include/ranges
@@ -154,6 +154,14 @@
requires (!common_range<V> && copyable<iterator_t<V>>)
class common_view;
+ // [range.reverse], reverse view
+ template<view V>
+ requires bidirectional_range<V>
+ class reverse_view;
+
+ template<class T>
+ inline constexpr bool enable_borrowed_range<reverse_view<T>> = enable_borrowed_range<T>;
+
template<class T>
inline constexpr bool enable_borrowed_range<common_view<T>> = enable_borrowed_range<T>;
@@ -188,6 +196,8 @@
#include <__ranges/enable_borrowed_range.h>
#include <__ranges/enable_view.h>
#include <__ranges/ref_view.h>
+#include <__ranges/reverse_view.h>
+#include <__ranges/take_view.h>
#include <__ranges/single_view.h>
#include <__ranges/size.h>
#include <__ranges/subrange.h>