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<div class="section">
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<div class="titlepage"><div><div><h3 class="title">
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<a name="boost_asio.reference.basic_waitable_timer"></a><a class="link" href="basic_waitable_timer.html" title="basic_waitable_timer">basic_waitable_timer</a>
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</h3></div></div></div>
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<p>
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<a class="indexterm" name="boost_asio.indexterm.basic_waitable_timer"></a>
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</p>
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<p>
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Provides waitable timer functionality.
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</p>
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<pre class="programlisting">template<
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typename Clock,
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typename <a class="link" href="WaitTraits.html" title="Wait traits requirements">WaitTraits</a>,
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typename <a class="link" href="Executor1.html" title="Executor requirements">Executor</a>>
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class basic_waitable_timer
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</pre>
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<h5>
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<a name="boost_asio.reference.basic_waitable_timer.h0"></a>
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<span class="phrase"><a name="boost_asio.reference.basic_waitable_timer.types"></a></span><a class="link" href="basic_waitable_timer.html#boost_asio.reference.basic_waitable_timer.types">Types</a>
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</h5>
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<div class="informaltable"><table class="table">
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<colgroup>
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<col>
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<col>
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</colgroup>
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<thead><tr>
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<th>
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<p>
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Name
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</p>
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</th>
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<th>
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<p>
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Description
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</p>
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</th>
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</tr></thead>
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<tbody>
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<tr>
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<td>
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<p>
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<a class="link" href="basic_waitable_timer__rebind_executor.html" title="basic_waitable_timer::rebind_executor"><span class="bold"><strong>rebind_executor</strong></span></a>
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</p>
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</td>
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<td>
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<p>
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Rebinds the timer type to another executor.
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</p>
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</td>
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</tr>
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<tr>
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<td>
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<p>
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<a class="link" href="basic_waitable_timer/clock_type.html" title="basic_waitable_timer::clock_type"><span class="bold"><strong>clock_type</strong></span></a>
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</p>
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</td>
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<td>
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<p>
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The clock type.
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</p>
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</td>
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</tr>
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<tr>
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<td>
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<p>
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<a class="link" href="basic_waitable_timer/duration.html" title="basic_waitable_timer::duration"><span class="bold"><strong>duration</strong></span></a>
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</p>
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</td>
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<td>
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<p>
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The duration type of the clock.
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</p>
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</td>
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</tr>
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<tr>
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<td>
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<p>
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<a class="link" href="basic_waitable_timer/executor_type.html" title="basic_waitable_timer::executor_type"><span class="bold"><strong>executor_type</strong></span></a>
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</p>
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</td>
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<td>
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<p>
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The type of the executor associated with the object.
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</p>
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</td>
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</tr>
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<tr>
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<td>
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<p>
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<a class="link" href="basic_waitable_timer/time_point.html" title="basic_waitable_timer::time_point"><span class="bold"><strong>time_point</strong></span></a>
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</p>
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</td>
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<td>
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<p>
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The time point type of the clock.
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</p>
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</td>
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</tr>
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<tr>
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<td>
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<p>
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<a class="link" href="basic_waitable_timer/traits_type.html" title="basic_waitable_timer::traits_type"><span class="bold"><strong>traits_type</strong></span></a>
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</p>
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</td>
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<td>
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<p>
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The wait traits type.
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</p>
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</td>
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</tr>
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</tbody>
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</table></div>
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<h5>
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<a name="boost_asio.reference.basic_waitable_timer.h1"></a>
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<span class="phrase"><a name="boost_asio.reference.basic_waitable_timer.member_functions"></a></span><a class="link" href="basic_waitable_timer.html#boost_asio.reference.basic_waitable_timer.member_functions">Member
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Functions</a>
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</h5>
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<div class="informaltable"><table class="table">
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<colgroup>
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<col>
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<col>
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</colgroup>
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<thead><tr>
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<th>
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<p>
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Name
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</p>
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</th>
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<th>
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<p>
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Description
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</p>
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</th>
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</tr></thead>
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<tbody>
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<tr>
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<td>
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<p>
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<a class="link" href="basic_waitable_timer/async_wait.html" title="basic_waitable_timer::async_wait"><span class="bold"><strong>async_wait</strong></span></a>
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</p>
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</td>
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<td>
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<p>
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Start an asynchronous wait on the timer.
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</p>
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</td>
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</tr>
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<tr>
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<td>
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<p>
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<a class="link" href="basic_waitable_timer/basic_waitable_timer.html" title="basic_waitable_timer::basic_waitable_timer"><span class="bold"><strong>basic_waitable_timer</strong></span></a> <span class="silver">[constructor]</span>
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</p>
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</td>
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<td>
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<p>
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Constructor. <br> <span class="silver"> —</span><br> Constructor to set a particular expiry
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time as an absolute time. <br> <span class="silver"> —</span><br> Constructor to set a particular
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expiry time relative to now. <br> <span class="silver"> —</span><br> Move-construct a basic_waitable_timer
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from another.
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</p>
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</td>
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</tr>
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<tr>
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<td>
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<p>
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<a class="link" href="basic_waitable_timer/cancel.html" title="basic_waitable_timer::cancel"><span class="bold"><strong>cancel</strong></span></a>
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</p>
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</td>
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<td>
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<p>
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Cancel any asynchronous operations that are waiting on the timer.
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<br> <span class="silver"> —</span><br> (Deprecated: Use non-error_code overload.) Cancel
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any asynchronous operations that are waiting on the timer.
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</p>
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</td>
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</tr>
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<tr>
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<td>
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<p>
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<a class="link" href="basic_waitable_timer/cancel_one.html" title="basic_waitable_timer::cancel_one"><span class="bold"><strong>cancel_one</strong></span></a>
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</p>
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</td>
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<td>
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<p>
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Cancels one asynchronous operation that is waiting on the timer.
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<br> <span class="silver"> —</span><br> (Deprecated: Use non-error_code overload.) Cancels
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one asynchronous operation that is waiting on the timer.
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</p>
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</td>
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</tr>
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<tr>
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<td>
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<p>
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<a class="link" href="basic_waitable_timer/expires_after.html" title="basic_waitable_timer::expires_after"><span class="bold"><strong>expires_after</strong></span></a>
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</p>
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</td>
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<td>
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<p>
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Set the timer's expiry time relative to now.
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</p>
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</td>
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</tr>
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<tr>
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<td>
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<p>
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<a class="link" href="basic_waitable_timer/expires_at.html" title="basic_waitable_timer::expires_at"><span class="bold"><strong>expires_at</strong></span></a>
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</p>
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</td>
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<td>
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<p>
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(Deprecated: Use expiry().) Get the timer's expiry time as an absolute
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time. <br> <span class="silver"> —</span><br> Set the timer's expiry time as an absolute
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time. <br> <span class="silver"> —</span><br> (Deprecated: Use non-error_code overload.)
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Set the timer's expiry time as an absolute time.
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</p>
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</td>
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</tr>
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<tr>
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<td>
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<p>
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<a class="link" href="basic_waitable_timer/expires_from_now.html" title="basic_waitable_timer::expires_from_now"><span class="bold"><strong>expires_from_now</strong></span></a>
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</p>
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</td>
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<td>
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<p>
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(Deprecated: Use expiry().) Get the timer's expiry time relative
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to now. <br> <span class="silver"> —</span><br> (Deprecated: Use expires_after().) Set the
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timer's expiry time relative to now.
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</p>
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</td>
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</tr>
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<tr>
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<td>
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<p>
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<a class="link" href="basic_waitable_timer/expiry.html" title="basic_waitable_timer::expiry"><span class="bold"><strong>expiry</strong></span></a>
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</p>
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</td>
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<td>
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<p>
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Get the timer's expiry time as an absolute time.
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</p>
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</td>
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</tr>
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<tr>
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<td>
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<p>
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<a class="link" href="basic_waitable_timer/get_executor.html" title="basic_waitable_timer::get_executor"><span class="bold"><strong>get_executor</strong></span></a>
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</p>
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</td>
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<td>
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<p>
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Get the executor associated with the object.
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</p>
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</td>
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</tr>
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<tr>
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<td>
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<p>
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<a class="link" href="basic_waitable_timer/operator_eq_.html" title="basic_waitable_timer::operator="><span class="bold"><strong>operator=</strong></span></a>
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</p>
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</td>
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<td>
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<p>
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Move-assign a basic_waitable_timer from another.
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</p>
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</td>
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</tr>
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<tr>
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<td>
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<p>
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<a class="link" href="basic_waitable_timer/wait.html" title="basic_waitable_timer::wait"><span class="bold"><strong>wait</strong></span></a>
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</p>
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</td>
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<td>
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<p>
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Perform a blocking wait on the timer.
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</p>
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</td>
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</tr>
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<tr>
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<td>
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<p>
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<a class="link" href="basic_waitable_timer/_basic_waitable_timer.html" title="basic_waitable_timer::~basic_waitable_timer"><span class="bold"><strong>~basic_waitable_timer</strong></span></a> <span class="silver">[destructor]</span>
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</p>
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</td>
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<td>
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<p>
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Destroys the timer.
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</p>
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</td>
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</tr>
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</tbody>
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</table></div>
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<p>
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The <a class="link" href="basic_waitable_timer.html" title="basic_waitable_timer"><code class="computeroutput">basic_waitable_timer</code></a>
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class template provides the ability to perform a blocking or asynchronous
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wait for a timer to expire.
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</p>
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<p>
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A waitable timer is always in one of two states: "expired" or "not
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expired". If the <code class="computeroutput">wait()</code> or <code class="computeroutput">async_wait()</code> function
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is called on an expired timer, the wait operation will complete immediately.
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</p>
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<p>
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Most applications will use one of the <a class="link" href="steady_timer.html" title="steady_timer"><code class="computeroutput">steady_timer</code></a>,
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<a class="link" href="system_timer.html" title="system_timer"><code class="computeroutput">system_timer</code></a>
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or <a class="link" href="high_resolution_timer.html" title="high_resolution_timer"><code class="computeroutput">high_resolution_timer</code></a>
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typedefs.
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</p>
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<h5>
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<a name="boost_asio.reference.basic_waitable_timer.h2"></a>
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<span class="phrase"><a name="boost_asio.reference.basic_waitable_timer.remarks"></a></span><a class="link" href="basic_waitable_timer.html#boost_asio.reference.basic_waitable_timer.remarks">Remarks</a>
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</h5>
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<p>
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This waitable timer functionality is for use with the C++11 standard library's
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<code class="computeroutput"><chrono></code> facility, or with the Boost.Chrono library.
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</p>
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<h5>
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<a name="boost_asio.reference.basic_waitable_timer.h3"></a>
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<span class="phrase"><a name="boost_asio.reference.basic_waitable_timer.thread_safety"></a></span><a class="link" href="basic_waitable_timer.html#boost_asio.reference.basic_waitable_timer.thread_safety">Thread
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Safety</a>
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</h5>
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<p>
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<span class="emphasis"><em>Distinct</em></span> <span class="emphasis"><em>objects:</em></span> Safe.
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</p>
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<p>
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<span class="emphasis"><em>Shared</em></span> <span class="emphasis"><em>objects:</em></span> Unsafe.
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</p>
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<h5>
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<a name="boost_asio.reference.basic_waitable_timer.h4"></a>
|
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<span class="phrase"><a name="boost_asio.reference.basic_waitable_timer.examples"></a></span><a class="link" href="basic_waitable_timer.html#boost_asio.reference.basic_waitable_timer.examples">Examples</a>
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</h5>
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<p>
|
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Performing a blocking wait (C++11):
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</p>
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<pre class="programlisting">// Construct a timer without setting an expiry time.
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boost::asio::steady_timer timer(my_context);
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// Set an expiry time relative to now.
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timer.expires_after(std::chrono::seconds(5));
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// Wait for the timer to expire.
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timer.wait();
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</pre>
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<p>
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Performing an asynchronous wait (C++11):
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</p>
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<pre class="programlisting">void handler(const boost::system::error_code& error)
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{
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if (!error)
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{
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// Timer expired.
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}
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}
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...
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// Construct a timer with an absolute expiry time.
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boost::asio::steady_timer timer(my_context,
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std::chrono::steady_clock::now() + std::chrono::seconds(60));
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// Start an asynchronous wait.
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timer.async_wait(handler);
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</pre>
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<h5>
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<a name="boost_asio.reference.basic_waitable_timer.h5"></a>
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<span class="phrase"><a name="boost_asio.reference.basic_waitable_timer.changing_an_active_waitable_timer_s_expiry_time"></a></span><a class="link" href="basic_waitable_timer.html#boost_asio.reference.basic_waitable_timer.changing_an_active_waitable_timer_s_expiry_time">Changing
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an active waitable timer's expiry time</a>
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</h5>
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<p>
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Changing the expiry time of a timer while there are pending asynchronous
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waits causes those wait operations to be cancelled. To ensure that the action
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associated with the timer is performed only once, use something like this:
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used:
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</p>
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<pre class="programlisting">void on_some_event()
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{
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if (my_timer.expires_after(seconds(5)) > 0)
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{
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// We managed to cancel the timer. Start new asynchronous wait.
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my_timer.async_wait(on_timeout);
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}
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else
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{
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// Too late, timer has already expired!
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}
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}
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void on_timeout(const boost::system::error_code& e)
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{
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if (e != boost::asio::error::operation_aborted)
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{
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// Timer was not cancelled, take necessary action.
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}
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}
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</pre>
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<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
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<li class="listitem">
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The <code class="computeroutput">boost::asio::basic_waitable_timer::expires_after()</code> function
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cancels any pending asynchronous waits, and returns the number of asynchronous
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waits that were cancelled. If it returns 0 then you were too late and
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the wait handler has already been executed, or will soon be executed.
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If it returns 1 then the wait handler was successfully cancelled.
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</li>
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<li class="listitem">
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If a wait handler is cancelled, the boost::system::error_code passed
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to it contains the value <code class="computeroutput">boost::asio::error::operation_aborted</code>.
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</li>
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</ul></div>
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<h5>
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<a name="boost_asio.reference.basic_waitable_timer.h6"></a>
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<span class="phrase"><a name="boost_asio.reference.basic_waitable_timer.requirements"></a></span><a class="link" href="basic_waitable_timer.html#boost_asio.reference.basic_waitable_timer.requirements">Requirements</a>
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</h5>
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<p>
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<span class="emphasis"><em>Header: </em></span><code class="literal">boost/asio/basic_waitable_timer.hpp</code>
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</p>
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<p>
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<span class="emphasis"><em>Convenience header: </em></span><code class="literal">boost/asio.hpp</code>
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</p>
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</div>
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