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  26 <div class="titlepage"><div><div><h4 class="title">
  27 <a name="boost_asio.reference.posix__basic_descriptor.async_wait"></a><a class="link" href="async_wait.html" title="posix::basic_descriptor::async_wait">posix::basic_descriptor::async_wait</a>
  28 </h4></div></div></div>
  29 <p>
  30           <a class="indexterm" name="boost_asio.indexterm.posix__basic_descriptor.async_wait"></a>
  31 Asynchronously
  32           wait for the descriptor to become ready to read, ready to write, or to
  33           have pending error conditions.
  34         </p>
  35 <pre class="programlisting">template&lt;
  36     typename <a class="link" href="../WaitHandler.html" title="Wait handler requirements">WaitHandler</a> = <a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>&gt;
  37 <a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.automatic_deduction_of_initiating_function_return_type"><span class="emphasis"><em>DEDUCED</em></span></a> async_wait(
  38     wait_type w,
  39     WaitHandler &amp;&amp; handler = <a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>);
  40 </pre>
  41 <p>
  42           This function is used to perform an asynchronous wait for a descriptor
  43           to enter a ready to read, write or error condition state.
  44         </p>
  45 <h6>
  46 <a name="boost_asio.reference.posix__basic_descriptor.async_wait.h0"></a>
  47           <span class="phrase"><a name="boost_asio.reference.posix__basic_descriptor.async_wait.parameters"></a></span><a class="link" href="async_wait.html#boost_asio.reference.posix__basic_descriptor.async_wait.parameters">Parameters</a>
  48         </h6>
  49 <div class="variablelist">
  50 <p class="title"><b></b></p>
  51 <dl class="variablelist">
  52 <dt><span class="term">w</span></dt>
  53 <dd><p>
  54                 Specifies the desired descriptor state.
  55               </p></dd>
  56 <dt><span class="term">handler</span></dt>
  57 <dd>
  58 <p>
  59                 The handler to be called when the wait operation completes. Copies
  60                 will be made of the handler as required. The function signature of
  61                 the handler must be:
  62 </p>
  63 <pre class="programlisting">void handler(
  64   const boost::system::error_code&amp; error // Result of operation
  65 );
  66 </pre>
  67 <p>
  68                 Regardless of whether the asynchronous operation completes immediately
  69                 or not, the handler will not be invoked from within this function.
  70                 On immediate completion, invocation of the handler will be performed
  71                 in a manner equivalent to using <a class="link" href="../post.html" title="post"><code class="computeroutput">post</code></a>.
  72               </p>
  73 </dd>
  74 </dl>
  75 </div>
  76 <h6>
  77 <a name="boost_asio.reference.posix__basic_descriptor.async_wait.h1"></a>
  78           <span class="phrase"><a name="boost_asio.reference.posix__basic_descriptor.async_wait.example"></a></span><a class="link" href="async_wait.html#boost_asio.reference.posix__basic_descriptor.async_wait.example">Example</a>
  79         </h6>
  80 <pre class="programlisting">void wait_handler(const boost::system::error_code&amp; error)
  81 {
  82   if (!error)
  83   {
  84     // Wait succeeded.
  85   }
  86 }
  87
  88 ...
  89
  90 boost::asio::posix::stream_descriptor descriptor(my_context);
  91 ...
  92 descriptor.async_wait(
  93     boost::asio::posix::stream_descriptor::wait_read,
  94     wait_handler);
  95 </pre>
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