1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>posix::basic_descriptor::async_wait</title> 5<link rel="stylesheet" href="../../../../../doc/src/boostbook.css" type="text/css"> 6<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 7<link rel="home" href="../../../boost_asio.html" title="Boost.Asio"> 8<link rel="up" href="../posix__basic_descriptor.html" title="posix::basic_descriptor"> 9<link rel="prev" href="assign/overload2.html" title="posix::basic_descriptor::assign (2 of 2 overloads)"> 10<link rel="next" href="basic_descriptor.html" title="posix::basic_descriptor::basic_descriptor"> 11</head> 12<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 13<table cellpadding="2" width="100%"><tr> 14<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../boost.png"></td> 15<td align="center"><a href="../../../../../index.html">Home</a></td> 16<td align="center"><a href="../../../../../libs/libraries.htm">Libraries</a></td> 17<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 18<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 19<td align="center"><a href="../../../../../more/index.htm">More</a></td> 20</tr></table> 21<hr> 22<div class="spirit-nav"> 23<a accesskey="p" href="assign/overload2.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../posix__basic_descriptor.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../boost_asio.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="basic_descriptor.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 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> 31Asynchronously 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< 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>> 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 && 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& 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& error) 81{ 82 if (!error) 83 { 84 // Wait succeeded. 85 } 86} 87 88... 89 90boost::asio::posix::stream_descriptor descriptor(my_context); 91... 92descriptor.async_wait( 93 boost::asio::posix::stream_descriptor::wait_read, 94 wait_handler); 95</pre> 96</div> 97<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 98<td align="left"></td> 99<td align="right"><div class="copyright-footer">Copyright © 2003-2020 Christopher M. 100 Kohlhoff<p> 101 Distributed under the Boost Software License, Version 1.0. (See accompanying 102 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>) 103 </p> 104</div></td> 105</tr></table> 106<hr> 107<div class="spirit-nav"> 108<a accesskey="p" href="assign/overload2.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../posix__basic_descriptor.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../boost_asio.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="basic_descriptor.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> 109</div> 110</body> 111</html> 112
