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| <div class="titlepage"><div><div><h4 class="title"> |
| <a name="boost_asio.overview.cpp2011.move_objects"></a><a class="link" href="move_objects.html" title="Movable I/O Objects">Movable I/O |
| Objects</a> |
| </h4></div></div></div> |
| <p> |
| When move support is available (via rvalue references), Boost.Asio allows |
| move construction and assignment of sockets, serial ports, POSIX descriptors |
| and Windows handles. |
| </p> |
| <p> |
| Move support allows you to write code like: |
| </p> |
| <pre class="programlisting"><span class="identifier">tcp</span><span class="special">::</span><span class="identifier">socket</span> <span class="identifier">make_socket</span><span class="special">(</span><span class="identifier">io_service</span><span class="special">&</span> <span class="identifier">i</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="identifier">tcp</span><span class="special">::</span><span class="identifier">socket</span> <span class="identifier">s</span><span class="special">(</span><span class="identifier">i</span><span class="special">);</span> |
| <span class="special">...</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">s</span><span class="special">);</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| or: |
| </p> |
| <pre class="programlisting"><span class="keyword">class</span> <span class="identifier">connection</span> <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">enable_shared_from_this</span><span class="special"><</span><span class="identifier">connection</span><span class="special">></span> |
| <span class="special">{</span> |
| <span class="keyword">private</span><span class="special">:</span> |
| <span class="identifier">tcp</span><span class="special">::</span><span class="identifier">socket</span> <span class="identifier">socket_</span><span class="special">;</span> |
| <span class="special">...</span> |
| <span class="keyword">public</span><span class="special">:</span> |
| <span class="identifier">connection</span><span class="special">(</span><span class="identifier">tcp</span><span class="special">::</span><span class="identifier">socket</span><span class="special">&&</span> <span class="identifier">s</span><span class="special">)</span> <span class="special">:</span> <span class="identifier">socket_</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">s</span><span class="special">))</span> <span class="special">{}</span> |
| <span class="special">...</span> |
| <span class="special">};</span> |
| |
| <span class="special">...</span> |
| |
| <span class="keyword">class</span> <span class="identifier">server</span> |
| <span class="special">{</span> |
| <span class="keyword">private</span><span class="special">:</span> |
| <span class="identifier">tcp</span><span class="special">::</span><span class="identifier">acceptor</span> <span class="identifier">acceptor_</span><span class="special">;</span> |
| <span class="identifier">tcp</span><span class="special">::</span><span class="identifier">socket</span> <span class="identifier">socket_</span><span class="special">;</span> |
| <span class="special">...</span> |
| <span class="keyword">void</span> <span class="identifier">handle_accept</span><span class="special">(</span><span class="identifier">error_code</span> <span class="identifier">ec</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">if</span> <span class="special">(!</span><span class="identifier">ec</span><span class="special">)</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">make_shared</span><span class="special"><</span><span class="identifier">connection</span><span class="special">>(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">socket_</span><span class="special">))-></span><span class="identifier">go</span><span class="special">();</span> |
| <span class="identifier">acceptor_</span><span class="special">.</span><span class="identifier">async_accept</span><span class="special">(</span><span class="identifier">socket_</span><span class="special">,</span> <span class="special">...);</span> |
| <span class="special">}</span> |
| <span class="special">...</span> |
| <span class="special">};</span> |
| </pre> |
| <p> |
| as well as: |
| </p> |
| <pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special"><</span><span class="identifier">tcp</span><span class="special">::</span><span class="identifier">socket</span><span class="special">></span> <span class="identifier">sockets</span><span class="special">;</span> |
| <span class="identifier">sockets</span><span class="special">.</span><span class="identifier">push_back</span><span class="special">(</span><span class="identifier">tcp</span><span class="special">::</span><span class="identifier">socket</span><span class="special">(...));</span> |
| </pre> |
| <p> |
| A word of warning: There is nothing stopping you from moving these objects |
| while there are pending asynchronous operations, but it is unlikely to |
| be a good idea to do so. In particular, composed operations like <a class="link" href="../../reference/async_read.html" title="async_read">async_read()</a> store a reference |
| to the stream object. Moving during the composed operation means that the |
| composed operation may attempt to access a moved-from object. |
| </p> |
| <p> |
| Move support is automatically enabled for <code class="literal">g++</code> 4.5 and |
| later, when the <code class="literal">-std=c++0x</code> or <code class="literal">-std=gnu++0x</code> |
| compiler options are used. It may be disabled by defining <code class="computeroutput"><span class="identifier">BOOST_ASIO_DISABLE_MOVE</span></code>, or explicitly |
| enabled for other compilers by defining <code class="computeroutput"><span class="identifier">BOOST_ASIO_HAS_MOVE</span></code>. |
| Note that these macros also affect the availability of <a class="link" href="move_handlers.html" title="Movable Handlers">movable |
| handlers</a>. |
| </p> |
| </div> |
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| <td align="left"></td> |
| <td align="right"><div class="copyright-footer">Copyright © 2003-2015 Christopher M. |
| Kohlhoff<p> |
| Distributed under the Boost Software License, Version 1.0. (See accompanying |
| file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) |
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