[libcxx-commits] [libcxx] [libc++][ranges] Implement `ranges::stride_view`. (PR #65200)

[Christopher Di Bella via libcxx-commits]

================
@@ -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()
----------------
cjdb wrote:

Please mark as `_LIBCPP_NODISCARD`.

https://github.com/llvm/llvm-project/pull/65200