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diff --git a/lib/asio/detail/object_pool.hpp b/lib/asio/detail/object_pool.hpp
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+++ b/lib/asio/detail/object_pool.hpp
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+//
+// detail/object_pool.hpp
+// ~~~~~~~~~~~~~~~~~~~~~~
+//
+// Copyright (c) 2003-2018 Christopher M. Kohlhoff (chris at kohlhoff 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)
+//
+
+#ifndef ASIO_DETAIL_OBJECT_POOL_HPP
+#define ASIO_DETAIL_OBJECT_POOL_HPP
+
+#if defined(_MSC_VER) && (_MSC_VER >= 1200)
+# pragma once
+#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
+
+#include "asio/detail/noncopyable.hpp"
+
+#include "asio/detail/push_options.hpp"
+
+namespace asio {
+namespace detail {
+
+template <typename Object>
+class object_pool;
+
+class object_pool_access
+{
+public:
+  template <typename Object>
+  static Object* create()
+  {
+    return new Object;
+  }
+
+  template <typename Object, typename Arg>
+  static Object* create(Arg arg)
+  {
+    return new Object(arg);
+  }
+
+  template <typename Object>
+  static void destroy(Object* o)
+  {
+    delete o;
+  }
+
+  template <typename Object>
+  static Object*& next(Object* o)
+  {
+    return o->next_;
+  }
+
+  template <typename Object>
+  static Object*& prev(Object* o)
+  {
+    return o->prev_;
+  }
+};
+
+template <typename Object>
+class object_pool
+  : private noncopyable
+{
+public:
+  // Constructor.
+  object_pool()
+    : live_list_(0),
+      free_list_(0)
+  {
+  }
+
+  // Destructor destroys all objects.
+  ~object_pool()
+  {
+    destroy_list(live_list_);
+    destroy_list(free_list_);
+  }
+
+  // Get the object at the start of the live list.
+  Object* first()
+  {
+    return live_list_;
+  }
+
+  // Allocate a new object.
+  Object* alloc()
+  {
+    Object* o = free_list_;
+    if (o)
+      free_list_ = object_pool_access::next(free_list_);
+    else
+      o = object_pool_access::create<Object>();
+
+    object_pool_access::next(o) = live_list_;
+    object_pool_access::prev(o) = 0;
+    if (live_list_)
+      object_pool_access::prev(live_list_) = o;
+    live_list_ = o;
+
+    return o;
+  }
+
+  // Allocate a new object with an argument.
+  template <typename Arg>
+  Object* alloc(Arg arg)
+  {
+    Object* o = free_list_;
+    if (o)
+      free_list_ = object_pool_access::next(free_list_);
+    else
+      o = object_pool_access::create<Object>(arg);
+
+    object_pool_access::next(o) = live_list_;
+    object_pool_access::prev(o) = 0;
+    if (live_list_)
+      object_pool_access::prev(live_list_) = o;
+    live_list_ = o;
+
+    return o;
+  }
+
+  // Free an object. Moves it to the free list. No destructors are run.
+  void free(Object* o)
+  {
+    if (live_list_ == o)
+      live_list_ = object_pool_access::next(o);
+
+    if (object_pool_access::prev(o))
+    {
+      object_pool_access::next(object_pool_access::prev(o))
+        = object_pool_access::next(o);
+    }
+
+    if (object_pool_access::next(o))
+    {
+      object_pool_access::prev(object_pool_access::next(o))
+        = object_pool_access::prev(o);
+    }
+
+    object_pool_access::next(o) = free_list_;
+    object_pool_access::prev(o) = 0;
+    free_list_ = o;
+  }
+
+private:
+  // Helper function to destroy all elements in a list.
+  void destroy_list(Object* list)
+  {
+    while (list)
+    {
+      Object* o = list;
+      list = object_pool_access::next(o);
+      object_pool_access::destroy(o);
+    }
+  }
+
+  // The list of live objects.
+  Object* live_list_;
+
+  // The free list.
+  Object* free_list_;
+};
+
+} // namespace detail
+} // namespace asio
+
+#include "asio/detail/pop_options.hpp"
+
+#endif // ASIO_DETAIL_OBJECT_POOL_HPP