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<title>basic_seq_packet_socket::native_non_blocking (3 of 3 overloads)</title>
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<div class="titlepage"><div><div><h5 class="title">
<a name="boost_asio.reference.basic_seq_packet_socket.native_non_blocking.overload3"></a><a class="link" href="overload3.html" title="basic_seq_packet_socket::native_non_blocking (3 of 3 overloads)">basic_seq_packet_socket::native_non_blocking
(3 of 3 overloads)</a>
</h5></div></div></div>
<p>
<span class="emphasis"><em>Inherited from basic_socket.</em></span>
</p>
<p>
Sets the non-blocking mode of the native socket implementation.
</p>
<pre class="programlisting">void native_non_blocking(
bool mode,
boost::system::error_code & ec);
</pre>
<p>
This function is used to modify the non-blocking mode of the underlying
native socket. It has no effect on the behaviour of the socket object's
synchronous operations.
</p>
<h6>
<a name="boost_asio.reference.basic_seq_packet_socket.native_non_blocking.overload3.h0"></a>
<span class="phrase"><a name="boost_asio.reference.basic_seq_packet_socket.native_non_blocking.overload3.parameters"></a></span><a class="link" href="overload3.html#boost_asio.reference.basic_seq_packet_socket.native_non_blocking.overload3.parameters">Parameters</a>
</h6>
<div class="variablelist">
<p class="title"><b></b></p>
<dl class="variablelist">
<dt><span class="term">mode</span></dt>
<dd><p>
If <code class="computeroutput">true</code>, the underlying socket is put into non-blocking
mode and direct system calls may fail with <code class="computeroutput">boost::asio::error::would_block</code>
(or the equivalent system error).
</p></dd>
<dt><span class="term">ec</span></dt>
<dd><p>
Set to indicate what error occurred, if any. If the <code class="computeroutput">mode</code>
is <code class="computeroutput">false</code>, but the current value of <code class="computeroutput">non_blocking()</code>
is <code class="computeroutput">true</code>, this function fails with <code class="computeroutput">boost::asio::error::invalid_argument</code>,
as the combination does not make sense.
</p></dd>
</dl>
</div>
<h6>
<a name="boost_asio.reference.basic_seq_packet_socket.native_non_blocking.overload3.h1"></a>
<span class="phrase"><a name="boost_asio.reference.basic_seq_packet_socket.native_non_blocking.overload3.example"></a></span><a class="link" href="overload3.html#boost_asio.reference.basic_seq_packet_socket.native_non_blocking.overload3.example">Example</a>
</h6>
<p>
This function is intended to allow the encapsulation of arbitrary non-blocking
system calls as asynchronous operations, in a way that is transparent
to the user of the socket object. The following example illustrates how
Linux's <code class="computeroutput">sendfile</code> system call might be encapsulated:
</p>
<pre class="programlisting">template <typename Handler>
struct sendfile_op
{
tcp::socket& sock_;
int fd_;
Handler handler_;
off_t offset_;
std::size_t total_bytes_transferred_;
// Function call operator meeting WriteHandler requirements.
// Used as the handler for the async_write_some operation.
void operator()(boost::system::error_code ec, std::size_t)
{
// Put the underlying socket into non-blocking mode.
if (!ec)
if (!sock_.native_non_blocking())
sock_.native_non_blocking(true, ec);
if (!ec)
{
for (;;)
{
// Try the system call.
errno = 0;
int n = ::sendfile(sock_.native_handle(), fd_, &offset_, 65536);
ec = boost::system::error_code(n < 0 ? errno : 0,
boost::asio::error::get_system_category());
total_bytes_transferred_ += ec ? 0 : n;
// Retry operation immediately if interrupted by signal.
if (ec == boost::asio::error::interrupted)
continue;
// Check if we need to run the operation again.
if (ec == boost::asio::error::would_block
|| ec == boost::asio::error::try_again)
{
// We have to wait for the socket to become ready again.
sock_.async_wait(tcp::socket::wait_write, *this);
return;
}
if (ec || n == 0)
{
// An error occurred, or we have reached the end of the file.
// Either way we must exit the loop so we can call the handler.
break;
}
// Loop around to try calling sendfile again.
}
}
// Pass result back to user's handler.
handler_(ec, total_bytes_transferred_);
}
};
template <typename Handler>
void async_sendfile(tcp::socket& sock, int fd, Handler h)
{
sendfile_op<Handler> op = { sock, fd, h, 0, 0 };
sock.async_wait(tcp::socket::wait_write, op);
}
</pre>
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<td align="right"><div class="copyright-footer">Copyright © 2003-2017 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>)
</p>
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