1 files changed, 141 insertions, 0 deletions
diff --git a/contrib/llvm-project/libcxx/include/__ranges/istream_view.h b/contrib/llvm-project/libcxx/include/__ranges/istream_view.h
new file mode 100644
index 000000000000..cd7096d35c2c
--- /dev/null
+++ b/contrib/llvm-project/libcxx/include/__ranges/istream_view.h
@@ -0,0 +1,141 @@
+// -*- 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_ISTREAM_VIEW_H
+#define _LIBCPP___RANGES_ISTREAM_VIEW_H
+
+#include <__concepts/constructible.h>
+#include <__concepts/derived_from.h>
+#include <__concepts/movable.h>
+#include <__config>
+#include <__fwd/istream.h>
+#include <__fwd/string.h>
+#include <__iterator/default_sentinel.h>
+#include <__iterator/iterator_traits.h>
+#include <__memory/addressof.h>
+#include <__ranges/view_interface.h>
+#include <__type_traits/remove_cvref.h>
+#include <__utility/forward.h>
+#include <cstddef>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+#if _LIBCPP_STD_VER >= 20
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+namespace ranges {
+
+template <class _Val, class _CharT, class _Traits>
+concept __stream_extractable = requires(basic_istream<_CharT, _Traits>& __is, _Val& __t) { __is >> __t; };
+
+template <movable _Val, class _CharT, class _Traits = char_traits<_CharT>>
+  requires default_initializable<_Val> && __stream_extractable<_Val, _CharT, _Traits>
+class basic_istream_view : public view_interface<basic_istream_view<_Val, _CharT, _Traits>> {
+  class __iterator;
+
+public:
+  _LIBCPP_HIDE_FROM_ABI constexpr explicit basic_istream_view(basic_istream<_CharT, _Traits>& __stream)
+      : __stream_(std::addressof(__stream)) {}
+
+  _LIBCPP_HIDE_FROM_ABI constexpr auto begin() {
+    *__stream_ >> __value_;
+    return __iterator{*this};
+  }
+
+  _LIBCPP_HIDE_FROM_ABI constexpr default_sentinel_t end() const noexcept { return default_sentinel; }
+
+private:
+  basic_istream<_CharT, _Traits>* __stream_;
+  _LIBCPP_NO_UNIQUE_ADDRESS _Val __value_ = _Val();
+};
+
+template <movable _Val, class _CharT, class _Traits>
+  requires default_initializable<_Val> && __stream_extractable<_Val, _CharT, _Traits>
+class basic_istream_view<_Val, _CharT, _Traits>::__iterator {
+public:
+  using iterator_concept = input_iterator_tag;
+  using difference_type  = ptrdiff_t;
+  using value_type       = _Val;
+
+  _LIBCPP_HIDE_FROM_ABI constexpr explicit __iterator(basic_istream_view<_Val, _CharT, _Traits>& __parent) noexcept
+      : __parent_(std::addressof(__parent)) {}
+
+  __iterator(const __iterator&)                  = delete;
+  _LIBCPP_HIDE_FROM_ABI __iterator(__iterator&&) = default;
+
+  __iterator& operator=(const __iterator&)                  = delete;
+  _LIBCPP_HIDE_FROM_ABI __iterator& operator=(__iterator&&) = default;
+
+  _LIBCPP_HIDE_FROM_ABI __iterator& operator++() {
+    *__parent_->__stream_ >> __parent_->__value_;
+    return *this;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI void operator++(int) { ++*this; }
+
+  _LIBCPP_HIDE_FROM_ABI _Val& operator*() const { return __parent_->__value_; }
+
+  _LIBCPP_HIDE_FROM_ABI friend bool operator==(const __iterator& __x, default_sentinel_t) {
+    return !*__x.__get_parent_stream();
+  }
+
+private:
+  basic_istream_view<_Val, _CharT, _Traits>* __parent_;
+
+  _LIBCPP_HIDE_FROM_ABI constexpr basic_istream<_CharT, _Traits>* __get_parent_stream() const {
+    return __parent_->__stream_;
+  }
+};
+
+template <class _Val>
+using istream_view = basic_istream_view<_Val, char>;
+
+#  ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
+template <class _Val>
+using wistream_view = basic_istream_view<_Val, wchar_t>;
+#  endif
+
+namespace views {
+namespace __istream {
+
+// clang-format off
+template <class _Tp>
+struct __fn {
+  template <class _Up, class _UnCVRef = remove_cvref_t<_Up>>
+    requires derived_from<_UnCVRef, basic_istream<typename _UnCVRef::char_type,
+                                                  typename _UnCVRef::traits_type>>
+  _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Up&& __u) const
+    noexcept(noexcept(basic_istream_view<_Tp, typename _UnCVRef::char_type,
+                                              typename _UnCVRef::traits_type>(std::forward<_Up>(__u))))
+    -> decltype(      basic_istream_view<_Tp, typename _UnCVRef::char_type,
+                                              typename _UnCVRef::traits_type>(std::forward<_Up>(__u)))
+    {   return        basic_istream_view<_Tp, typename _UnCVRef::char_type,
+                                              typename _UnCVRef::traits_type>(std::forward<_Up>(__u));
+    }
+};
+// clang-format on
+
+} // namespace __istream
+
+inline namespace __cpo {
+template <class _Tp>
+inline constexpr auto istream = __istream::__fn<_Tp>{};
+} // namespace __cpo
+} // namespace views
+
+} // namespace ranges
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STD_VER >= 20
+
+#endif // _LIBCPP___RANGES_ISTREAM_VIEW_H