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  27 <a name="boost_asio.reference.basic_stream_socket.native_non_blocking.overload1"></a><a class="link" href="overload1.html" title="basic_stream_socket::native_non_blocking (1 of 3 overloads)">basic_stream_socket::native_non_blocking
  28           (1 of 3 overloads)</a>
  29 </h5></div></div></div>
  30 <p>
  31             <span class="emphasis"><em>Inherited from basic_socket.</em></span>
  32           </p>
  33 <p>
  34             Gets the non-blocking mode of the native socket implementation.
  35           </p>
  36 <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>
  37 </pre>
  38 <p>
  39             This function is used to retrieve the non-blocking mode of the underlying
  40             native socket. This mode has no effect on the behaviour of the socket
  41             object's synchronous operations.
  42           </p>
  43 <h6>
  44 <a name="boost_asio.reference.basic_stream_socket.native_non_blocking.overload1.h0"></a>
  45             <span class="phrase"><a name="boost_asio.reference.basic_stream_socket.native_non_blocking.overload1.return_value"></a></span><a class="link" href="overload1.html#boost_asio.reference.basic_stream_socket.native_non_blocking.overload1.return_value">Return
  46             Value</a>
  47           </h6>
  48 <p>
  49             <code class="computeroutput"><span class="keyword">true</span></code> if the underlying socket
  50             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
  51             error).
  52           </p>
  53 <h6>
  54 <a name="boost_asio.reference.basic_stream_socket.native_non_blocking.overload1.h1"></a>
  55             <span class="phrase"><a name="boost_asio.reference.basic_stream_socket.native_non_blocking.overload1.remarks"></a></span><a class="link" href="overload1.html#boost_asio.reference.basic_stream_socket.native_non_blocking.overload1.remarks">Remarks</a>
  56           </h6>
  57 <p>
  58             The current non-blocking mode is cached by the socket object. Consequently,
  59             the return value may be incorrect if the non-blocking mode was set directly
  60             on the native socket.
  61           </p>
  62 <h6>
  63 <a name="boost_asio.reference.basic_stream_socket.native_non_blocking.overload1.h2"></a>
  64             <span class="phrase"><a name="boost_asio.reference.basic_stream_socket.native_non_blocking.overload1.example"></a></span><a class="link" href="overload1.html#boost_asio.reference.basic_stream_socket.native_non_blocking.overload1.example">Example</a>
  65           </h6>
  66 <p>
  67             This function is intended to allow the encapsulation of arbitrary non-blocking
  68             system calls as asynchronous operations, in a way that is transparent
  69             to the user of the socket object. The following example illustrates how
  70             Linux's <code class="computeroutput"><span class="identifier">sendfile</span></code> system
  71             call might be encapsulated:
  72           </p>
  73 <pre class="programlisting"><span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">Handler</span><span class="special">&gt;</span>
  74 <span class="keyword">struct</span> <span class="identifier">sendfile_op</span>
  75 <span class="special">{</span>
  76   <span class="identifier">tcp</span><span class="special">::</span><span class="identifier">socket</span><span class="special">&amp;</span> <span class="identifier">sock_</span><span class="special">;</span>
  77   <span class="keyword">int</span> <span class="identifier">fd_</span><span class="special">;</span>
  78   <span class="identifier">Handler</span> <span class="identifier">handler_</span><span class="special">;</span>
  79   <span class="identifier">off_t</span> <span class="identifier">offset_</span><span class="special">;</span>
  80   <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>
  81
  82   <span class="comment">// Function call operator meeting WriteHandler requirements.</span>
  83   <span class="comment">// Used as the handler for the async_write_some operation.</span>
  84   <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>
  85   <span class="special">{</span>
  86     <span class="comment">// Put the underlying socket into non-blocking mode.</span>
  87     <span class="keyword">if</span> <span class="special">(!</span><span class="identifier">ec</span><span class="special">)</span>
  88       <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>
  89         <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>
  90
  91     <span class="keyword">if</span> <span class="special">(!</span><span class="identifier">ec</span><span class="special">)</span>
  92     <span class="special">{</span>
  93       <span class="keyword">for</span> <span class="special">(;;)</span>
  94       <span class="special">{</span>
  95         <span class="comment">// Try the system call.</span>
  96         <span class="identifier">errno</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span>
  97         <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">&amp;</span><span class="identifier">offset_</span><span class="special">,</span> <span class="number">65536</span><span class="special">);</span>
  98         <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">&lt;</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>
  99             <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>
 100         <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>
 101
 102         <span class="comment">// Retry operation immediately if interrupted by signal.</span>
 103         <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>
 104           <span class="keyword">continue</span><span class="special">;</span>
 105
 106         <span class="comment">// Check if we need to run the operation again.</span>
 107         <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>
 108             <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>
 109         <span class="special">{</span>
 110           <span class="comment">// We have to wait for the socket to become ready again.</span>
 111           <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>
 112           <span class="keyword">return</span><span class="special">;</span>
 113         <span class="special">}</span>
 114
 115         <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>
 116         <span class="special">{</span>
 117           <span class="comment">// An error occurred, or we have reached the end of the file.</span>
 118           <span class="comment">// Either way we must exit the loop so we can call the handler.</span>
 119           <span class="keyword">break</span><span class="special">;</span>
 120         <span class="special">}</span>
 121
 122         <span class="comment">// Loop around to try calling sendfile again.</span>
 123       <span class="special">}</span>
 124     <span class="special">}</span>
 125
 126     <span class="comment">// Pass result back to user's handler.</span>
 127     <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>
 128   <span class="special">}</span>
 129 <span class="special">};</span>
 130
 131 <span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">Handler</span><span class="special">&gt;</span>
 132 <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">&amp;</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>
 133 <span class="special">{</span>
 134   <span class="identifier">sendfile_op</span><span class="special">&lt;</span><span class="identifier">Handler</span><span class="special">&gt;</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>
 135   <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>
 136 <span class="special">}</span>
 137 </pre>
 138 </div>
 139 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 140 <td align="left"></td>
 141 <td align="right"><div class="copyright-footer">Copyright &#169; 2003-2014 Christopher M. Kohlhoff<p>
 142         Distributed under the Boost Software License, Version 1.0. (See accompanying
 143         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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