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diff --git a/boost/asio/strand.hpp b/boost/asio/strand.hpp
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+//
+// strand.hpp
+// ~~~~~~~~~~
+//
+// Copyright (c) 2003-2012 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 BOOST_ASIO_STRAND_HPP
+#define BOOST_ASIO_STRAND_HPP
+
+#if defined(_MSC_VER) && (_MSC_VER >= 1200)
+# pragma once
+#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
+
+#include <boost/asio/detail/config.hpp>
+#include <boost/asio/detail/handler_type_requirements.hpp>
+#include <boost/asio/detail/strand_service.hpp>
+#include <boost/asio/detail/wrapped_handler.hpp>
+#include <boost/asio/io_service.hpp>
+
+#include <boost/asio/detail/push_options.hpp>
+
+namespace boost {
+namespace asio {
+
+/// Provides serialised handler execution.
+/**
+ * The io_service::strand class provides the ability to post and dispatch
+ * handlers with the guarantee that none of those handlers will execute
+ * concurrently.
+ *
+ * @par Order of handler invocation
+ * Given:
+ *
+ * @li a strand object @c s
+ *
+ * @li an object @c a meeting completion handler requirements
+ *
+ * @li an object @c a1 which is an arbitrary copy of @c a made by the
+ * implementation
+ *
+ * @li an object @c b meeting completion handler requirements
+ *
+ * @li an object @c b1 which is an arbitrary copy of @c b made by the
+ * implementation
+ *
+ * if any of the following conditions are true:
+ *
+ * @li @c s.post(a) happens-before @c s.post(b)
+ * 
+ * @li @c s.post(a) happens-before @c s.dispatch(b), where the latter is
+ * performed outside the strand
+ * 
+ * @li @c s.dispatch(a) happens-before @c s.post(b), where the former is
+ * performed outside the strand
+ * 
+ * @li @c s.dispatch(a) happens-before @c s.dispatch(b), where both are
+ * performed outside the strand
+ *   
+ * then @c asio_handler_invoke(a1, &a1) happens-before
+ * @c asio_handler_invoke(b1, &b1).
+ * 
+ * Note that in the following case:
+ * @code async_op_1(..., s.wrap(a));
+ * async_op_2(..., s.wrap(b)); @endcode
+ * the completion of the first async operation will perform @c s.dispatch(a),
+ * and the second will perform @c s.dispatch(b), but the order in which those
+ * are performed is unspecified. That is, you cannot state whether one
+ * happens-before the other. Therefore none of the above conditions are met and
+ * no ordering guarantee is made.
+ *
+ * @par Thread Safety
+ * @e Distinct @e objects: Safe.@n
+ * @e Shared @e objects: Safe.
+ *
+ * @par Concepts:
+ * Dispatcher.
+ */
+class io_service::strand
+{
+public:
+  /// Constructor.
+  /**
+   * Constructs the strand.
+   *
+   * @param io_service The io_service object that the strand will use to
+   * dispatch handlers that are ready to be run.
+   */
+  explicit strand(boost::asio::io_service& io_service)
+    : service_(boost::asio::use_service<
+        boost::asio::detail::strand_service>(io_service))
+  {
+    service_.construct(impl_);
+  }
+
+  /// Destructor.
+  /**
+   * Destroys a strand.
+   *
+   * Handlers posted through the strand that have not yet been invoked will
+   * still be dispatched in a way that meets the guarantee of non-concurrency.
+   */
+  ~strand()
+  {
+    service_.destroy(impl_);
+  }
+
+  /// Get the io_service associated with the strand.
+  /**
+   * This function may be used to obtain the io_service object that the strand
+   * uses to dispatch handlers for asynchronous operations.
+   *
+   * @return A reference to the io_service object that the strand will use to
+   * dispatch handlers. Ownership is not transferred to the caller.
+   */
+  boost::asio::io_service& get_io_service()
+  {
+    return service_.get_io_service();
+  }
+
+  /// Request the strand to invoke the given handler.
+  /**
+   * This function is used to ask the strand to execute the given handler.
+   *
+   * The strand object guarantees that handlers posted or dispatched through
+   * the strand will not be executed concurrently. The handler may be executed
+   * inside this function if the guarantee can be met. If this function is
+   * called from within a handler that was posted or dispatched through the same
+   * strand, then the new handler will be executed immediately.
+   *
+   * The strand's guarantee is in addition to the guarantee provided by the
+   * underlying io_service. The io_service guarantees that the handler will only
+   * be called in a thread in which the io_service's run member function is
+   * currently being invoked.
+   *
+   * @param handler The handler to be called. The strand will make a copy of the
+   * handler object as required. The function signature of the handler must be:
+   * @code void handler(); @endcode
+   */
+  template <typename CompletionHandler>
+  void dispatch(BOOST_ASIO_MOVE_ARG(CompletionHandler) handler)
+  {
+    // If you get an error on the following line it means that your handler does
+    // not meet the documented type requirements for a CompletionHandler.
+    BOOST_ASIO_COMPLETION_HANDLER_CHECK(CompletionHandler, handler) type_check;
+
+    service_.dispatch(impl_, BOOST_ASIO_MOVE_CAST(CompletionHandler)(handler));
+  }
+
+  /// Request the strand to invoke the given handler and return
+  /// immediately.
+  /**
+   * This function is used to ask the strand to execute the given handler, but
+   * without allowing the strand to call the handler from inside this function.
+   *
+   * The strand object guarantees that handlers posted or dispatched through
+   * the strand will not be executed concurrently. The strand's guarantee is in
+   * addition to the guarantee provided by the underlying io_service. The
+   * io_service guarantees that the handler will only be called in a thread in
+   * which the io_service's run member function is currently being invoked.
+   *
+   * @param handler The handler to be called. The strand will make a copy of the
+   * handler object as required. The function signature of the handler must be:
+   * @code void handler(); @endcode
+   */
+  template <typename CompletionHandler>
+  void post(BOOST_ASIO_MOVE_ARG(CompletionHandler) handler)
+  {
+    // If you get an error on the following line it means that your handler does
+    // not meet the documented type requirements for a CompletionHandler.
+    BOOST_ASIO_COMPLETION_HANDLER_CHECK(CompletionHandler, handler) type_check;
+
+    service_.post(impl_, BOOST_ASIO_MOVE_CAST(CompletionHandler)(handler));
+  }
+
+  /// Create a new handler that automatically dispatches the wrapped handler
+  /// on the strand.
+  /**
+   * This function is used to create a new handler function object that, when
+   * invoked, will automatically pass the wrapped handler to the strand's
+   * dispatch function.
+   *
+   * @param handler The handler to be wrapped. The strand will make a copy of
+   * the handler object as required. The function signature of the handler must
+   * be: @code void handler(A1 a1, ... An an); @endcode
+   *
+   * @return A function object that, when invoked, passes the wrapped handler to
+   * the strand's dispatch function. Given a function object with the signature:
+   * @code R f(A1 a1, ... An an); @endcode
+   * If this function object is passed to the wrap function like so:
+   * @code strand.wrap(f); @endcode
+   * then the return value is a function object with the signature
+   * @code void g(A1 a1, ... An an); @endcode
+   * that, when invoked, executes code equivalent to:
+   * @code strand.dispatch(boost::bind(f, a1, ... an)); @endcode
+   */
+  template <typename Handler>
+#if defined(GENERATING_DOCUMENTATION)
+  unspecified
+#else
+  detail::wrapped_handler<strand, Handler>
+#endif
+  wrap(Handler handler)
+  {
+    return detail::wrapped_handler<io_service::strand, Handler>(*this, handler);
+  }
+
+private:
+  boost::asio::detail::strand_service& service_;
+  boost::asio::detail::strand_service::implementation_type impl_;
+};
+
+/// Typedef for backwards compatibility.
+typedef boost::asio::io_service::strand strand;
+
+} // namespace asio
+} // namespace boost
+
+#include <boost/asio/detail/pop_options.hpp>
+
+#endif // BOOST_ASIO_STRAND_HPP