Rearrange sources (#4997)

include/xrpl/beast/container/detail/empty_base_optimization.h

@@ -0,0 +1,100 @@
+//
+// Copyright (c) 2016-2017 Vinnie Falco (vinnie dot falco at gmail dot com)
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+// Official repository: https://github.com/boostorg/beast
+//
+
+#ifndef BEAST_CONTAINER_DETAIL_EMPTY_BASE_OPTIMIZATION_H_INCLUDED
+#define BEAST_CONTAINER_DETAIL_EMPTY_BASE_OPTIMIZATION_H_INCLUDED
+
+#include <boost/type_traits/is_final.hpp>
+#include <type_traits>
+#include <utility>
+
+namespace beast {
+namespace detail {
+
+template <class T>
+struct is_empty_base_optimization_derived
+    : std::integral_constant<
+          bool,
+          std::is_empty<T>::value && !boost::is_final<T>::value>
+{
+};
+
+template <
+    class T,
+    int UniqueID = 0,
+    bool isDerived = is_empty_base_optimization_derived<T>::value>
+class empty_base_optimization : private T
+{
+public:
+    empty_base_optimization() = default;
+    empty_base_optimization(empty_base_optimization&&) = default;
+    empty_base_optimization(empty_base_optimization const&) = default;
+    empty_base_optimization&
+    operator=(empty_base_optimization&&) = default;
+    empty_base_optimization&
+    operator=(empty_base_optimization const&) = default;
+
+    template <class Arg1, class... ArgN>
+    explicit empty_base_optimization(Arg1&& arg1, ArgN&&... argn)
+        : T(std::forward<Arg1>(arg1), std::forward<ArgN>(argn)...)
+    {
+    }
+
+    T&
+    member() noexcept
+    {
+        return *this;
+    }
+
+    T const&
+    member() const noexcept
+    {
+        return *this;
+    }
+};
+
+//------------------------------------------------------------------------------
+
+template <class T, int UniqueID>
+class empty_base_optimization<T, UniqueID, false>
+{
+    T t_;
+
+public:
+    empty_base_optimization() = default;
+    empty_base_optimization(empty_base_optimization&&) = default;
+    empty_base_optimization(empty_base_optimization const&) = default;
+    empty_base_optimization&
+    operator=(empty_base_optimization&&) = default;
+    empty_base_optimization&
+    operator=(empty_base_optimization const&) = default;
+
+    template <class Arg1, class... ArgN>
+    explicit empty_base_optimization(Arg1&& arg1, ArgN&&... argn)
+        : t_(std::forward<Arg1>(arg1), std::forward<ArgN>(argn)...)
+    {
+    }
+
+    T&
+    member() noexcept
+    {
+        return t_;
+    }
+
+    T const&
+    member() const noexcept
+    {
+        return t_;
+    }
+};
+
+}  // namespace detail
+}  // namespace beast
+
+#endif