[libcxx] [llvm] [libc++] Implement P2442R1 `std::views::chunk` (PR #171234)

[via llvm-commits]

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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_CHUNK_VIEW_H
+#define _LIBCPP___RANGES_CHUNK_VIEW_H
+
+#include <__algorithm/ranges_min.h>
+#include <__assert>
+#include <__concepts/constructible.h>
+#include <__concepts/convertible_to.h>
+#include <__config>
+#include <__functional/bind_back.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 <__memory/addressof.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/range_adaptor.h>
+#include <__ranges/take_view.h>
+#include <__ranges/view_interface.h>
+#include <__type_traits/conditional.h>
+#include <__type_traits/decay.h>
+#include <__type_traits/is_nothrow_constructible.h>
+#include <__type_traits/make_unsigned.h>
+#include <__utility/forward.h>
+#include <__utility/move.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER >= 23
+
+namespace ranges {
+
+template <class _Integral>
+inline _LIBCPP_HIDE_FROM_ABI constexpr auto __div_ceil(_Integral __num, _Integral __denom) {
+  _Integral __r = __num / __denom;
+  if (__num % __denom)
+    ++__r;
+  return __r;
+}
+
+template <view _View>
+  requires input_range<_View>
+class _LIBCPP_ABI_LLVM18_NO_UNIQUE_ADDRESS chunk_view : public view_interface<chunk_view<_View>> {
+  _LIBCPP_NO_UNIQUE_ADDRESS _View __base_;
+  _LIBCPP_NO_UNIQUE_ADDRESS range_difference_t<_View> __n_;
+  _LIBCPP_NO_UNIQUE_ADDRESS range_difference_t<_View> __remainder_;
+  _LIBCPP_NO_UNIQUE_ADDRESS __non_propagating_cache<iterator_t<_View>> __current_;
+
+  class __outer_iterator;
+  class __inner_iterator;
+
+public:
+  _LIBCPP_HIDE_FROM_ABI constexpr explicit chunk_view(_View __base, range_difference_t<_View> __n)
+      : __base_(std::move(__base)), __n_(__n), __remainder_(0) {
+    _LIBCPP_ASSERT_PEDANTIC(__n > 0, "Trying to construct a chunk_view with chunk size <= 0");
+  }
+
+  _LIBCPP_HIDE_FROM_ABI constexpr _View base() const&
+    requires std::copy_constructible<_View>
+  {
+    return __base_;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI constexpr _View base() && { return std::move(__base_); }
+
+  _LIBCPP_HIDE_FROM_ABI constexpr __outer_iterator begin() {
+    __current_.__emplace(ranges::begin(__base_));
+    __remainder_ = __n_;
+    return __outer_iterator(*this);
+  }
+
+  _LIBCPP_HIDE_FROM_ABI constexpr default_sentinel_t end() const noexcept { return std::default_sentinel; }
+
+  _LIBCPP_HIDE_FROM_ABI constexpr auto size()
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anonymouspc wrote:

Ok, I'll add `[[nodiscard]]` here. Thank you!

https://github.com/llvm/llvm-project/pull/171234