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  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"><span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">cancel</span><span class="special">();</span>
  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"><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">operation_aborted</span></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"><span class="identifier">cancel</span><span class="special">()</span></code> is called, then the handlers for asynchronous
  71             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>
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  88 <td align="right"><div class="copyright-footer">Copyright &#169; 2003-2017 Christopher M. Kohlhoff<p>
  89         Distributed under the Boost Software License, Version 1.0. (See accompanying
  90         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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