1 files changed, 62 insertions, 0 deletions
diff --git a/contrib/llvm-project/libcxx/include/__algorithm/uniform_random_bit_generator_adaptor.h b/contrib/llvm-project/libcxx/include/__algorithm/uniform_random_bit_generator_adaptor.h
new file mode 100644
index 000000000000..04a67752dd0b
--- /dev/null
+++ b/contrib/llvm-project/libcxx/include/__algorithm/uniform_random_bit_generator_adaptor.h
@@ -0,0 +1,62 @@
+//===----------------------------------------------------------------------===//
+//
+// 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___ALGORITHM_RANGES_UNIFORM_RANDOM_BIT_GENERATOR_ADAPTOR_H
+#define _LIBCPP___ALGORITHM_RANGES_UNIFORM_RANDOM_BIT_GENERATOR_ADAPTOR_H
+
+#include <__config>
+#include <__functional/invoke.h>
+#include <type_traits>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+#if _LIBCPP_STD_VER > 17
+
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+// Range versions of random algorithms (e.g. `std::shuffle`) are less constrained than their classic counterparts.
+// Range algorithms only require the given generator to satisfy the `std::uniform_random_bit_generator` concept.
+// Classic algorithms require the given generator to meet the uniform random bit generator requirements; these
+// requirements include satisfying `std::uniform_random_bit_generator` and add a requirement for the generator to
+// provide a nested `result_type` typedef (see `[rand.req.urng]`).
+//
+// To be able to reuse classic implementations, make the given generator meet the classic requirements by wrapping
+// it into an adaptor type that forwards all of its interface and adds the required typedef.
+template <class _Gen>
+class _ClassicGenAdaptor {
+private:
+  // The generator is not required to be copyable or movable, so it has to be stored as a reference.
+  _Gen& __gen;
+
+public:
+  using result_type = invoke_result_t<_Gen&>;
+
+  _LIBCPP_HIDE_FROM_ABI
+  static constexpr auto min() { return __uncvref_t<_Gen>::min(); }
+  _LIBCPP_HIDE_FROM_ABI
+  static constexpr auto max() { return __uncvref_t<_Gen>::max(); }
+
+  _LIBCPP_HIDE_FROM_ABI
+  constexpr explicit _ClassicGenAdaptor(_Gen& __g) : __gen(__g) {}
+
+  _LIBCPP_HIDE_FROM_ABI
+  constexpr auto operator()() const { return __gen(); }
+};
+
+_LIBCPP_END_NAMESPACE_STD
+
+_LIBCPP_POP_MACROS
+
+#endif // _LIBCPP_STD_VER > 17
+
+#endif // _LIBCPP___ALGORITHM_RANGES_UNIFORM_RANDOM_BIT_GENERATOR_ADAPTOR_H