[libcxx-commits] [libcxx] [libc++][ranges] Implement `ranges::stride_view`. (PR #65200)
Christopher Di Bella via libcxx-commits
libcxx-commits at lists.llvm.org
Tue Jan 2 15:34:10 PST 2024
================
@@ -0,0 +1,396 @@
+// -*- 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_STRIDE_VIEW_H
+#define _LIBCPP___RANGES_STRIDE_VIEW_H
+
+#include "__concepts/relation.h"
+#include "__functional/ranges_operations.h"
+#include "__iterator/indirectly_comparable.h"
+#include <__config>
+
+#include <__compare/three_way_comparable.h>
+#include <__concepts/convertible_to.h>
+#include <__concepts/derived_from.h>
+#include <__concepts/equality_comparable.h>
+#include <__functional/bind_back.h>
+#include <__functional/operations.h>
+#include <__iterator/advance.h>
+#include <__iterator/concepts.h>
+#include <__iterator/default_sentinel.h>
+#include <__iterator/distance.h>
+#include <__iterator/iter_move.h>
+#include <__iterator/iter_swap.h>
+#include <__iterator/iterator_traits.h>
+#include <__ranges/access.h>
+#include <__ranges/all.h>
+#include <__ranges/concepts.h>
+#include <__ranges/range_adaptor.h>
+#include <__ranges/view_interface.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+# pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER >= 23
+
+namespace ranges {
+
+template <class _Value>
+_LIBCPP_HIDE_FROM_ABI constexpr _Value __div_ceil(_Value __left, _Value __right) {
+ _Value __r = __left / __right;
+ if (__left % __right) {
+ __r++;
+ }
+ return __r;
+}
+
+template <input_range _View>
+ requires view<_View>
+class stride_view : public view_interface<stride_view<_View>> {
+ _LIBCPP_NO_UNIQUE_ADDRESS _View __base_ = _View();
+ range_difference_t<_View> __stride_ = 0;
+
+ template <bool _Const>
+ class __iterator;
+
+public:
+ _LIBCPP_HIDE_FROM_ABI constexpr explicit stride_view(_View __base, range_difference_t<_View> __stride)
+ : __base_(std::move(__base)), __stride_(__stride) {
+ _LIBCPP_ASSERT_UNCATEGORIZED(__stride > 0, "The value of stride must be greater than 0");
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr _View base() const&
+ requires copy_constructible<_View>
+ {
+ return __base_;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr _View base() && { return std::move(__base_); }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr range_difference_t<_View> stride() const noexcept { return __stride_; }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr auto begin()
+ requires(!__simple_view<_View>)
+ {
+ return __iterator<false>(this, ranges::begin(__base_), 0);
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr auto begin() const
+ requires range<const _View>
+ {
+ return __iterator<true>(this, ranges::begin(__base_), 0);
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr auto end()
+ requires(!__simple_view<_View>)
+ {
+ if constexpr (common_range<_View> && sized_range<_View> && forward_range<_View>) {
+ auto __missing = (__stride_ - ranges::distance(__base_) % __stride_) % __stride_;
+ return __iterator<false>(this, ranges::end(__base_), __missing);
+ } else if constexpr (common_range<_View> && !bidirectional_range<_View>) {
+ return __iterator<false>(this, ranges::end(__base_), 0);
+ } else {
+ return default_sentinel;
+ }
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr auto end() const
+ requires(range<const _View>)
+ {
+ if constexpr (common_range<const _View> && sized_range<const _View> && forward_range<const _View>) {
+ auto __missing = (__stride_ - ranges::distance(__base_) % __stride_) % __stride_;
+ return __iterator<true>(this, ranges::end(__base_), __missing);
+ } else if constexpr (common_range<_View> && !bidirectional_range<_View>) {
+ return __iterator<true>(this, ranges::end(__base_), 0);
+ } else {
+ return default_sentinel;
+ }
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr auto size()
+ requires sized_range<_View>
+ {
+ return std::__to_unsigned_like(ranges::__div_ceil(ranges::distance(__base_), __stride_));
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr auto size() const
+ requires sized_range<const _View>
+ {
+ return std::__to_unsigned_like(ranges::__div_ceil(ranges::distance(__base_), __stride_));
+ }
+}; // class stride_view
+
+template <class _Range>
+stride_view(_Range&&, range_difference_t<_Range>) -> stride_view<views::all_t<_Range>>;
+
+template <class _View>
+struct __stride_iterator_category {};
+
+template <forward_range _View>
+struct __stride_iterator_category<_View> {
+ using _Cat = typename iterator_traits<iterator_t<_View>>::iterator_category;
+ using iterator_category =
+ _If<derived_from<_Cat, random_access_iterator_tag>,
+ random_access_iterator_tag,
+ /* else */ _Cat >;
+};
+
+template <input_range _View>
+ requires view<_View>
+template <bool _Const>
+class stride_view<_View>::__iterator : public __stride_iterator_category<_View> {
+ using _Parent = __maybe_const<_Const, stride_view<_View>>;
+ using _Base = __maybe_const<_Const, _View>;
+
+ _LIBCPP_NO_UNIQUE_ADDRESS iterator_t<_Base> __current_ = iterator_t<_Base>();
+ _LIBCPP_NO_UNIQUE_ADDRESS ranges::sentinel_t<_Base> __end_ = ranges::sentinel_t<_Base>();
+ range_difference_t<_Base> __stride_ = 0;
+ range_difference_t<_Base> __missing_ = 0;
+
+ friend stride_view;
+
+ _LIBCPP_HIDE_FROM_ABI constexpr __iterator(
+ _Parent* __parent, ranges::iterator_t<_Base> __current, range_difference_t<_Base> __missing)
+ : __current_(std::move(__current)),
+ __end_(ranges::end(__parent->__base_)),
+ __stride_(__parent->__stride_),
+ __missing_(__missing) {}
+
+ static consteval auto __get_stride_view_iterator_concept() {
+ if constexpr (random_access_range<_Base>) {
+ return random_access_iterator_tag{};
+ } else if constexpr (bidirectional_range<_Base>) {
+ return bidirectional_iterator_tag{};
+ } else if constexpr (forward_range<_Base>) {
+ return forward_iterator_tag{};
+ } else {
+ return input_iterator_tag{};
+ }
+ }
+
+public:
+ using difference_type = range_difference_t<_Base>;
+ using value_type = range_value_t<_Base>;
+ using iterator_concept = decltype(__get_stride_view_iterator_concept());
+ // using iterator_category = inherited;
+
+ _LIBCPP_HIDE_FROM_ABI __iterator()
+ requires default_initializable<iterator_t<_Base>>
+ = default;
+
+ _LIBCPP_HIDE_FROM_ABI constexpr __iterator(__iterator<!_Const> __i)
+ requires _Const && convertible_to<ranges::iterator_t<_View>, iterator_t<_Base>> &&
+ convertible_to<sentinel_t<_View>, sentinel_t<_Base>>
+ : __current_(std::move(__i.__current_)),
+ __end_(std::move(__i.__end_)),
+ __stride_(__i.__stride_),
+ __missing_(__i.__missing_) {}
+
+ _LIBCPP_HIDE_FROM_ABI constexpr iterator_t<_Base> const& base() const& noexcept { return __current_; }
+ _LIBCPP_HIDE_FROM_ABI constexpr iterator_t<_Base> base() && { return std::move(__current_); }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) operator*() const {
+ _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__current_ != __end_, "Cannot dereference an iterator at the end.");
+ return *__current_;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr __iterator& operator++() {
+ _LIBCPP_ASSERT_UNCATEGORIZED(__current_ != __end_, "Cannot increment an iterator already at the end.");
+ __missing_ = ranges::advance(__current_, __stride_, __end_);
+ return *this;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr void operator++(int) { ++*this; }
+ _LIBCPP_HIDE_FROM_ABI constexpr __iterator operator++(int)
+ requires forward_range<_Base>
+ {
+ auto __tmp = *this;
+ ++*this;
+ return __tmp;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr __iterator& operator--()
+ requires bidirectional_range<_Base>
+ {
+ ranges::advance(__current_, __missing_ - __stride_);
+ __missing_ = 0;
+ return *this;
+ }
+ _LIBCPP_HIDE_FROM_ABI constexpr __iterator operator--(int)
+ requires bidirectional_range<_Base>
+ {
+ auto __tmp = *this;
+ --*this;
+ return __tmp;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr __iterator& operator+=(difference_type __n)
+ requires random_access_range<_Base>
+ {
+ if (__n > 0) {
+ _LIBCPP_ASSERT_UNCATEGORIZED(ranges::distance(__current_, __end_) > __stride_ * (__n - 1),
+ "Advancing the iterator beyond the end is not allowed.");
+ ranges::advance(__current_, __stride_ * (__n - 1));
+ __missing_ = ranges::advance(__current_, __stride_, __end_);
+
+ } else if (__n < 0) {
+ ranges::advance(__current_, __stride_ * __n + __missing_);
+ __missing_ = 0;
+ }
+ return *this;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr __iterator& operator-=(difference_type __n)
+ requires random_access_range<_Base>
+ {
+ return *this += -__n;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) operator[](difference_type __n) const
+ requires random_access_range<_Base>
+ {
+ return *(*this + __n);
+ }
+
+ _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(__iterator const& __x, default_sentinel_t) {
+ return __x.__current_ == __x.__end_;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(__iterator const& __x, __iterator const& __y)
+ requires equality_comparable<iterator_t<_Base>>
+ {
+ return __x.__current_ == __y.__current_;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator<(__iterator const& __x, __iterator const& __y)
+ requires random_access_range<_Base>
+ {
+ return __x.__current_ < __y.__current_;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator>(__iterator const& __x, __iterator const& __y)
+ requires random_access_range<_Base>
+ {
+ return __y < __x;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator<=(__iterator const& __x, __iterator const& __y)
+ requires random_access_range<_Base>
+ {
+ return !(__y < __x);
+ }
+
+ _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator>=(__iterator const& __x, __iterator const& __y)
+ requires random_access_range<_Base>
+ {
+ return !(__x < __y);
+ }
+
+ _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator<=>(__iterator const& __x, __iterator const& __y)
+ requires random_access_range<_Base> && three_way_comparable<iterator_t<_Base>>
+ {
+ return __x.__current_ <=> __y.__current_;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI friend constexpr __iterator operator+(__iterator const& __i, difference_type __s)
----------------
cjdb wrote:
Please mark as `_LIBCPP_NODISCARD`.
https://github.com/llvm/llvm-project/pull/65200
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