move_objects.html
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<title>Movable I/O Objects</title>
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<div class="titlepage"><div><div><h4 class="title">
<a name="asio.overview.cpp2011.move_objects"></a><a class="link" href="move_objects.html" title="Movable I/O Objects">Movable I/O Objects</a>
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<p>
When move support is available (via rvalue references), 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">tcp::socket make_socket(io_context& i)
{
tcp::socket s(i);
...
std::move(s);
}
</pre>
<p>
or:
</p>
<pre class="programlisting">class connection : public enable_shared_from_this<connection>
{
private:
tcp::socket socket_;
...
public:
connection(tcp::socket&& s) : socket_(std::move(s)) {}
...
};
...
class server
{
private:
tcp::acceptor acceptor_;
...
void handle_accept(error_code ec, tcp::socket socket)
{
if (!ec)
std::make_shared<connection>(std::move(socket))->go();
acceptor_.async_accept(...);
}
...
};
</pre>
<p>
as well as:
</p>
<pre class="programlisting">std::vector<tcp::socket> sockets;
sockets.push_back(tcp::socket(...));
</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">ASIO_DISABLE_MOVE</code>,
or explicitly enabled for other compilers by defining <code class="computeroutput">ASIO_HAS_MOVE</code>.
Note that these macros also affect the availability of <a class="link" href="move_handlers.html" title="Movable Handlers">movable
handlers</a>.
</p>
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<td align="right"><div class="copyright-footer">Copyright © 2003-2020 Christopher M.
Kohlhoff<p>
Distributed under the Boost Software License, Version 1.0. (See accompanying
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