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  26 <div class="titlepage"><div><div><h5 class="title">
  27 <a name="boost_asio.reference.basic_socket_streambuf.native_non_blocking.overload2"></a><a class="link" href="overload2.html" title="basic_socket_streambuf::native_non_blocking (2 of 3 overloads)">basic_socket_streambuf::native_non_blocking
  28           (2 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             Sets the non-blocking mode of the native socket implementation.
  35           </p>
  36 <pre class="programlisting"><span class="keyword">void</span> <span class="identifier">native_non_blocking</span><span class="special">(</span>
  37     <span class="keyword">bool</span> <span class="identifier">mode</span><span class="special">);</span>
  38 </pre>
  39 <p>
  40             This function is used to modify the non-blocking mode of the underlying
  41             native socket. It has no effect on the behaviour of the socket object's
  42             synchronous operations.
  43           </p>
  44 <h6>
  45 <a name="boost_asio.reference.basic_socket_streambuf.native_non_blocking.overload2.h0"></a>
  46             <span class="phrase"><a name="boost_asio.reference.basic_socket_streambuf.native_non_blocking.overload2.parameters"></a></span><a class="link" href="overload2.html#boost_asio.reference.basic_socket_streambuf.native_non_blocking.overload2.parameters">Parameters</a>
  47           </h6>
  48 <div class="variablelist">
  49 <p class="title"><b></b></p>
  50 <dl class="variablelist">
  51 <dt><span class="term">mode</span></dt>
  52 <dd><p>
  53                   If <code class="computeroutput"><span class="keyword">true</span></code>, the underlying
  54                   socket is put into non-blocking mode and direct system calls may
  55                   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>
  56                   (or the equivalent system error).
  57                 </p></dd>
  58 </dl>
  59 </div>
  60 <h6>
  61 <a name="boost_asio.reference.basic_socket_streambuf.native_non_blocking.overload2.h1"></a>
  62             <span class="phrase"><a name="boost_asio.reference.basic_socket_streambuf.native_non_blocking.overload2.exceptions"></a></span><a class="link" href="overload2.html#boost_asio.reference.basic_socket_streambuf.native_non_blocking.overload2.exceptions">Exceptions</a>
  63           </h6>
  64 <div class="variablelist">
  65 <p class="title"><b></b></p>
  66 <dl class="variablelist">
  67 <dt><span class="term">boost::system::system_error</span></dt>
  68 <dd><p>
  69                   Thrown on failure. If the <code class="computeroutput"><span class="identifier">mode</span></code>
  70                   is <code class="computeroutput"><span class="keyword">false</span></code>, but the
  71                   current value of <code class="computeroutput"><span class="identifier">non_blocking</span><span class="special">()</span></code> is <code class="computeroutput"><span class="keyword">true</span></code>,
  72                   this function fails 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">invalid_argument</span></code>,
  73                   as the combination does not make sense.
  74                 </p></dd>
  75 </dl>
  76 </div>
  77 <h6>
  78 <a name="boost_asio.reference.basic_socket_streambuf.native_non_blocking.overload2.h2"></a>
  79             <span class="phrase"><a name="boost_asio.reference.basic_socket_streambuf.native_non_blocking.overload2.example"></a></span><a class="link" href="overload2.html#boost_asio.reference.basic_socket_streambuf.native_non_blocking.overload2.example">Example</a>
  80           </h6>
  81 <p>
  82             This function is intended to allow the encapsulation of arbitrary non-blocking
  83             system calls as asynchronous operations, in a way that is transparent
  84             to the user of the socket object. The following example illustrates how
  85             Linux's <code class="computeroutput"><span class="identifier">sendfile</span></code> system
  86             call might be encapsulated:
  87           </p>
  88 <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>
  89 <span class="keyword">struct</span> <span class="identifier">sendfile_op</span>
  90 <span class="special">{</span>
  91   <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>
  92   <span class="keyword">int</span> <span class="identifier">fd_</span><span class="special">;</span>
  93   <span class="identifier">Handler</span> <span class="identifier">handler_</span><span class="special">;</span>
  94   <span class="identifier">off_t</span> <span class="identifier">offset_</span><span class="special">;</span>
  95   <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>
  96
  97   <span class="comment">// Function call operator meeting WriteHandler requirements.</span>
  98   <span class="comment">// Used as the handler for the async_write_some operation.</span>
  99   <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>
 100   <span class="special">{</span>
 101     <span class="comment">// Put the underlying socket into non-blocking mode.</span>
 102     <span class="keyword">if</span> <span class="special">(!</span><span class="identifier">ec</span><span class="special">)</span>
 103       <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>
 104         <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>
 105
 106     <span class="keyword">if</span> <span class="special">(!</span><span class="identifier">ec</span><span class="special">)</span>
 107     <span class="special">{</span>
 108       <span class="keyword">for</span> <span class="special">(;;)</span>
 109       <span class="special">{</span>
 110         <span class="comment">// Try the system call.</span>
 111         <span class="identifier">errno</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span>
 112         <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>
 113         <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>
 114             <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>
 115         <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>
 116
 117         <span class="comment">// Retry operation immediately if interrupted by signal.</span>
 118         <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>
 119           <span class="keyword">continue</span><span class="special">;</span>
 120
 121         <span class="comment">// Check if we need to run the operation again.</span>
 122         <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>
 123             <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>
 124         <span class="special">{</span>
 125           <span class="comment">// We have to wait for the socket to become ready again.</span>
 126           <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>
 127           <span class="keyword">return</span><span class="special">;</span>
 128         <span class="special">}</span>
 129
 130         <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>
 131         <span class="special">{</span>
 132           <span class="comment">// An error occurred, or we have reached the end of the file.</span>
 133           <span class="comment">// Either way we must exit the loop so we can call the handler.</span>
 134           <span class="keyword">break</span><span class="special">;</span>
 135         <span class="special">}</span>
 136
 137         <span class="comment">// Loop around to try calling sendfile again.</span>
 138       <span class="special">}</span>
 139     <span class="special">}</span>
 140
 141     <span class="comment">// Pass result back to user's handler.</span>
 142     <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>
 143   <span class="special">}</span>
 144 <span class="special">};</span>
 145
 146 <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>
 147 <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>
 148 <span class="special">{</span>
 149   <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>
 150   <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>
 151 <span class="special">}</span>
 152 </pre>
 153 </div>
 154 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 155 <td align="left"></td>
 156 <td align="right"><div class="copyright-footer">Copyright &#169; 2003-2014 Christopher M. Kohlhoff<p>
 157         Distributed under the Boost Software License, Version 1.0. (See accompanying
 158         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>)
 159       </p>
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