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<title>basic_socket_streambuf::native_non_blocking (1 of 3 overloads)</title>
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<div class="titlepage"><div><div><h5 class="title">
<a name="boost_asio.reference.basic_socket_streambuf.native_non_blocking.overload1"></a><a class="link" href="overload1.html" title="basic_socket_streambuf::native_non_blocking (1 of 3 overloads)">basic_socket_streambuf::native_non_blocking
(1 of 3 overloads)</a>
</h5></div></div></div>
<p>
<span class="emphasis"><em>Inherited from basic_socket.</em></span>
</p>
<p>
Gets the non-blocking mode of the native socket implementation.
</p>
<pre class="programlisting"><span class="keyword">bool</span> <span class="identifier">native_non_blocking</span><span class="special">()</span> <span class="keyword">const</span><span class="special">;</span>
</pre>
<p>
This function is used to retrieve the non-blocking mode of the underlying
native socket. This mode has no effect on the behaviour of the socket
object's synchronous operations.
</p>
<h6>
<a name="boost_asio.reference.basic_socket_streambuf.native_non_blocking.overload1.h0"></a>
<span class="phrase"><a name="boost_asio.reference.basic_socket_streambuf.native_non_blocking.overload1.return_value"></a></span><a class="link" href="overload1.html#boost_asio.reference.basic_socket_streambuf.native_non_blocking.overload1.return_value">Return
Value</a>
</h6>
<p>
<code class="computeroutput"><span class="keyword">true</span></code> if the underlying socket
is in non-blocking mode and direct system calls may fail with <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">error</span><span class="special">::</span><span class="identifier">would_block</span></code> (or the equivalent system
error).
</p>
<h6>
<a name="boost_asio.reference.basic_socket_streambuf.native_non_blocking.overload1.h1"></a>
<span class="phrase"><a name="boost_asio.reference.basic_socket_streambuf.native_non_blocking.overload1.remarks"></a></span><a class="link" href="overload1.html#boost_asio.reference.basic_socket_streambuf.native_non_blocking.overload1.remarks">Remarks</a>
</h6>
<p>
The current non-blocking mode is cached by the socket object. Consequently,
the return value may be incorrect if the non-blocking mode was set directly
on the native socket.
</p>
<h6>
<a name="boost_asio.reference.basic_socket_streambuf.native_non_blocking.overload1.h2"></a>
<span class="phrase"><a name="boost_asio.reference.basic_socket_streambuf.native_non_blocking.overload1.example"></a></span><a class="link" href="overload1.html#boost_asio.reference.basic_socket_streambuf.native_non_blocking.overload1.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"><span class="identifier">sendfile</span></code> system
call might be encapsulated:
</p>
<pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Handler</span><span class="special">></span>
<span class="keyword">struct</span> <span class="identifier">sendfile_op</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">sock_</span><span class="special">;</span>
<span class="keyword">int</span> <span class="identifier">fd_</span><span class="special">;</span>
<span class="identifier">Handler</span> <span class="identifier">handler_</span><span class="special">;</span>
<span class="identifier">off_t</span> <span class="identifier">offset_</span><span class="special">;</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">total_bytes_transferred_</span><span class="special">;</span>
<span class="comment">// Function call operator meeting WriteHandler requirements.</span>
<span class="comment">// Used as the handler for the async_write_some operation.</span>
<span class="keyword">void</span> <span class="keyword">operator</span><span class="special">()(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">system</span><span class="special">::</span><span class="identifier">error_code</span> <span class="identifier">ec</span><span class="special">,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span><span class="special">)</span>
<span class="special">{</span>
<span class="comment">// Put the underlying socket into non-blocking mode.</span>
<span class="keyword">if</span> <span class="special">(!</span><span class="identifier">ec</span><span class="special">)</span>
<span class="keyword">if</span> <span class="special">(!</span><span class="identifier">sock_</span><span class="special">.</span><span class="identifier">native_non_blocking</span><span class="special">())</span>
<span class="identifier">sock_</span><span class="special">.</span><span class="identifier">native_non_blocking</span><span class="special">(</span><span class="keyword">true</span><span class="special">,</span> <span class="identifier">ec</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="special">{</span>
<span class="keyword">for</span> <span class="special">(;;)</span>
<span class="special">{</span>
<span class="comment">// Try the system call.</span>
<span class="identifier">errno</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span>
<span class="keyword">int</span> <span class="identifier">n</span> <span class="special">=</span> <span class="special">::</span><span class="identifier">sendfile</span><span class="special">(</span><span class="identifier">sock_</span><span class="special">.</span><span class="identifier">native_handle</span><span class="special">(),</span> <span class="identifier">fd_</span><span class="special">,</span> <span class="special">&</span><span class="identifier">offset_</span><span class="special">,</span> <span class="number">65536</span><span class="special">);</span>
<span class="identifier">ec</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">system</span><span class="special">::</span><span class="identifier">error_code</span><span class="special">(</span><span class="identifier">n</span> <span class="special"><</span> <span class="number">0</span> <span class="special">?</span> <span class="identifier">errno</span> <span class="special">:</span> <span class="number">0</span><span class="special">,</span>
<span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">error</span><span class="special">::</span><span class="identifier">get_system_category</span><span class="special">());</span>
<span class="identifier">total_bytes_transferred_</span> <span class="special">+=</span> <span class="identifier">ec</span> <span class="special">?</span> <span class="number">0</span> <span class="special">:</span> <span class="identifier">n</span><span class="special">;</span>
<span class="comment">// Retry operation immediately if interrupted by signal.</span>
<span class="keyword">if</span> <span class="special">(</span><span class="identifier">ec</span> <span class="special">==</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">error</span><span class="special">::</span><span class="identifier">interrupted</span><span class="special">)</span>
<span class="keyword">continue</span><span class="special">;</span>
<span class="comment">// Check if we need to run the operation again.</span>
<span class="keyword">if</span> <span class="special">(</span><span class="identifier">ec</span> <span class="special">==</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">error</span><span class="special">::</span><span class="identifier">would_block</span>
<span class="special">||</span> <span class="identifier">ec</span> <span class="special">==</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">error</span><span class="special">::</span><span class="identifier">try_again</span><span class="special">)</span>
<span class="special">{</span>
<span class="comment">// We have to wait for the socket to become ready again.</span>
<span class="identifier">sock_</span><span class="special">.</span><span class="identifier">async_write_some</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">null_buffers</span><span class="special">(),</span> <span class="special">*</span><span class="keyword">this</span><span class="special">);</span>
<span class="keyword">return</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">n</span> <span class="special">==</span> <span class="number">0</span><span class="special">)</span>
<span class="special">{</span>
<span class="comment">// An error occurred, or we have reached the end of the file.</span>
<span class="comment">// Either way we must exit the loop so we can call the handler.</span>
<span class="keyword">break</span><span class="special">;</span>
<span class="special">}</span>
<span class="comment">// Loop around to try calling sendfile again.</span>
<span class="special">}</span>
<span class="special">}</span>
<span class="comment">// Pass result back to user's handler.</span>
<span class="identifier">handler_</span><span class="special">(</span><span class="identifier">ec</span><span class="special">,</span> <span class="identifier">total_bytes_transferred_</span><span class="special">);</span>
<span class="special">}</span>
<span class="special">};</span>
<span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Handler</span><span class="special">></span>
<span class="keyword">void</span> <span class="identifier">async_sendfile</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">sock</span><span class="special">,</span> <span class="keyword">int</span> <span class="identifier">fd</span><span class="special">,</span> <span class="identifier">Handler</span> <span class="identifier">h</span><span class="special">)</span>
<span class="special">{</span>
<span class="identifier">sendfile_op</span><span class="special"><</span><span class="identifier">Handler</span><span class="special">></span> <span class="identifier">op</span> <span class="special">=</span> <span class="special">{</span> <span class="identifier">sock</span><span class="special">,</span> <span class="identifier">fd</span><span class="special">,</span> <span class="identifier">h</span><span class="special">,</span> <span class="number">0</span><span class="special">,</span> <span class="number">0</span> <span class="special">};</span>
<span class="identifier">sock</span><span class="special">.</span><span class="identifier">async_write_some</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">null_buffers</span><span class="special">(),</span> <span class="identifier">op</span><span class="special">);</span>
<span class="special">}</span>
</pre>
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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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