1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>basic_waitable_timer::cancel (1 of 2 overloads)</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="../cancel.html" title="basic_waitable_timer::cancel"> 9<link rel="prev" href="../cancel.html" title="basic_waitable_timer::cancel"> 10<link rel="next" href="overload2.html" title="basic_waitable_timer::cancel (2 of 2 overloads)"> 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="../cancel.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../cancel.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="overload2.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h5 class="title"> 27<a name="boost_asio.reference.basic_waitable_timer.cancel.overload1"></a><a class="link" href="overload1.html" title="basic_waitable_timer::cancel (1 of 2 overloads)">basic_waitable_timer::cancel 28 (1 of 2 overloads)</a> 29</h5></div></div></div> 30<p> 31 Cancel any asynchronous operations that are waiting on the timer. 32 </p> 33<pre class="programlisting">std::size_t cancel(); 34</pre> 35<p> 36 This function forces the completion of any pending asynchronous wait 37 operations against the timer. The handler for each cancelled operation 38 will be invoked with the <code class="computeroutput">boost::asio::error::operation_aborted</code> 39 error code. 40 </p> 41<p> 42 Cancelling the timer does not change the expiry time. 43 </p> 44<h6> 45<a name="boost_asio.reference.basic_waitable_timer.cancel.overload1.h0"></a> 46 <span class="phrase"><a name="boost_asio.reference.basic_waitable_timer.cancel.overload1.return_value"></a></span><a class="link" href="overload1.html#boost_asio.reference.basic_waitable_timer.cancel.overload1.return_value">Return 47 Value</a> 48 </h6> 49<p> 50 The number of asynchronous operations that were cancelled. 51 </p> 52<h6> 53<a name="boost_asio.reference.basic_waitable_timer.cancel.overload1.h1"></a> 54 <span class="phrase"><a name="boost_asio.reference.basic_waitable_timer.cancel.overload1.exceptions"></a></span><a class="link" href="overload1.html#boost_asio.reference.basic_waitable_timer.cancel.overload1.exceptions">Exceptions</a> 55 </h6> 56<div class="variablelist"> 57<p class="title"><b></b></p> 58<dl class="variablelist"> 59<dt><span class="term">boost::system::system_error</span></dt> 60<dd><p> 61 Thrown on failure. 62 </p></dd> 63</dl> 64</div> 65<h6> 66<a name="boost_asio.reference.basic_waitable_timer.cancel.overload1.h2"></a> 67 <span class="phrase"><a name="boost_asio.reference.basic_waitable_timer.cancel.overload1.remarks"></a></span><a class="link" href="overload1.html#boost_asio.reference.basic_waitable_timer.cancel.overload1.remarks">Remarks</a> 68 </h6> 69<p> 70 If the timer has already expired when <code class="computeroutput">cancel()</code> is called, 71 then the handlers for asynchronous wait operations will: 72 </p> 73<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 74<li class="listitem"> 75 have already been invoked; or 76 </li> 77<li class="listitem"> 78 have been queued for invocation in the near future. 79 </li> 80</ul></div> 81<p> 82 These handlers can no longer be cancelled, and therefore are passed an 83 error code that indicates the successful completion of the wait operation. 84 </p> 85</div> 86<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 87<td align="left"></td> 88<td align="right"><div class="copyright-footer">Copyright © 2003-2020 Christopher M. 89 Kohlhoff<p> 90 Distributed under the Boost Software License, Version 1.0. (See accompanying 91 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>) 92 </p> 93</div></td> 94</tr></table> 95<hr> 96<div class="spirit-nav"> 97<a accesskey="p" href="../cancel.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../cancel.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="overload2.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> 98</div> 99</body> 100</html> 101
