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450 lines
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<table cellpadding="2" width="100%"><tr><td valign="top"><img alt="asio C++ library" width="250" height="60" src="../../asio.png"></td></tr></table>
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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="asio.reference.steady_timer"></a><a class="link" href="steady_timer.html" title="steady_timer">steady_timer</a>
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</h3></div></div></div>
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<p>
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<a class="indexterm" name="asio.indexterm.steady_timer"></a>
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</p>
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<p>
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Typedef for a timer based on the steady clock.
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</p>
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<pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">basic_waitable_timer</span><span class="special"><</span> <span class="identifier">chrono</span><span class="special">::</span><span class="identifier">steady_clock</span> <span class="special">></span> <span class="identifier">steady_timer</span><span class="special">;</span>
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</pre>
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<h5>
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<a name="asio.reference.steady_timer.h0"></a>
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<span><a name="asio.reference.steady_timer.types"></a></span><a class="link" href="steady_timer.html#asio.reference.steady_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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<thead><tr>
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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="asio.reference.steady_timer.h1"></a>
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<span><a name="asio.reference.steady_timer.member_functions"></a></span><a class="link" href="steady_timer.html#asio.reference.steady_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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<thead><tr>
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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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<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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<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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<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"><span class="identifier">basic_waitable_timer</span></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"><span class="identifier">wait</span><span class="special">()</span></code> or <code class="computeroutput"><span class="identifier">async_wait</span><span class="special">()</span></code> function is called on an expired timer,
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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"><span class="identifier">steady_timer</span></code></a>, <a class="link" href="system_timer.html" title="system_timer"><code class="computeroutput"><span class="identifier">system_timer</span></code></a> or <a class="link" href="high_resolution_timer.html" title="high_resolution_timer"><code class="computeroutput"><span class="identifier">high_resolution_timer</span></code></a> typedefs.
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</p>
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<h5>
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<a name="asio.reference.steady_timer.h2"></a>
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<span><a name="asio.reference.steady_timer.remarks"></a></span><a class="link" href="steady_timer.html#asio.reference.steady_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"><span class="special"><</span><span class="identifier">chrono</span><span class="special">></span></code> facility, or with the Boost.Chrono library.
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</p>
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<h5>
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<a name="asio.reference.steady_timer.h3"></a>
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<span><a name="asio.reference.steady_timer.thread_safety"></a></span><a class="link" href="steady_timer.html#asio.reference.steady_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="asio.reference.steady_timer.h4"></a>
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<span><a name="asio.reference.steady_timer.examples"></a></span><a class="link" href="steady_timer.html#asio.reference.steady_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"><span class="comment">// Construct a timer without setting an expiry time.</span>
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<span class="identifier">asio</span><span class="special">::</span><span class="identifier">steady_timer</span> <span class="identifier">timer</span><span class="special">(</span><span class="identifier">my_context</span><span class="special">);</span>
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<span class="comment">// Set an expiry time relative to now.</span>
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<span class="identifier">timer</span><span class="special">.</span><span class="identifier">expires_after</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">seconds</span><span class="special">(</span><span class="number">5</span><span class="special">));</span>
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<span class="comment">// Wait for the timer to expire.</span>
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<span class="identifier">timer</span><span class="special">.</span><span class="identifier">wait</span><span class="special">();</span>
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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"><span class="keyword">void</span> <span class="identifier">handler</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">asio</span><span class="special">::</span><span class="identifier">error_code</span><span class="special">&</span> <span class="identifier">error</span><span class="special">)</span>
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<span class="special">{</span>
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<span class="keyword">if</span> <span class="special">(!</span><span class="identifier">error</span><span class="special">)</span>
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<span class="special">{</span>
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<span class="comment">// Timer expired.</span>
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<span class="special">}</span>
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<span class="special">}</span>
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<span class="special">...</span>
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<span class="comment">// Construct a timer with an absolute expiry time.</span>
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<span class="identifier">asio</span><span class="special">::</span><span class="identifier">steady_timer</span> <span class="identifier">timer</span><span class="special">(</span><span class="identifier">my_context</span><span class="special">,</span>
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<span class="identifier">std</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">steady_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">+</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">seconds</span><span class="special">(</span><span class="number">60</span><span class="special">));</span>
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<span class="comment">// Start an asynchronous wait.</span>
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<span class="identifier">timer</span><span class="special">.</span><span class="identifier">async_wait</span><span class="special">(</span><span class="identifier">handler</span><span class="special">);</span>
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</pre>
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<h5>
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<a name="asio.reference.steady_timer.h5"></a>
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<span><a name="asio.reference.steady_timer.changing_an_active_waitable_timer_s_expiry_time"></a></span><a class="link" href="steady_timer.html#asio.reference.steady_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"><span class="keyword">void</span> <span class="identifier">on_some_event</span><span class="special">()</span>
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<span class="special">{</span>
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<span class="keyword">if</span> <span class="special">(</span><span class="identifier">my_timer</span><span class="special">.</span><span class="identifier">expires_after</span><span class="special">(</span><span class="identifier">seconds</span><span class="special">(</span><span class="number">5</span><span class="special">))</span> <span class="special">></span> <span class="number">0</span><span class="special">)</span>
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<span class="special">{</span>
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<span class="comment">// We managed to cancel the timer. Start new asynchronous wait.</span>
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<span class="identifier">my_timer</span><span class="special">.</span><span class="identifier">async_wait</span><span class="special">(</span><span class="identifier">on_timeout</span><span class="special">);</span>
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<span class="special">}</span>
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<span class="keyword">else</span>
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<span class="special">{</span>
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<span class="comment">// Too late, timer has already expired!</span>
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<span class="special">}</span>
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<span class="special">}</span>
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<span class="keyword">void</span> <span class="identifier">on_timeout</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">asio</span><span class="special">::</span><span class="identifier">error_code</span><span class="special">&</span> <span class="identifier">e</span><span class="special">)</span>
|
|
<span class="special">{</span>
|
|
<span class="keyword">if</span> <span class="special">(</span><span class="identifier">e</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><span class="special">)</span>
|
|
<span class="special">{</span>
|
|
<span class="comment">// Timer was not cancelled, take necessary action.</span>
|
|
<span class="special">}</span>
|
|
<span class="special">}</span>
|
|
</pre>
|
|
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
|
|
<li class="listitem">
|
|
The <code class="computeroutput"><span class="identifier">asio</span><span class="special">::</span><span class="identifier">basic_waitable_timer</span><span class="special">::</span><span class="identifier">expires_after</span><span class="special">()</span></code>
|
|
function cancels any pending asynchronous waits, and returns the number
|
|
of asynchronous waits that were cancelled. If it returns 0 then you were
|
|
too late and the wait handler has already been executed, or will soon
|
|
be executed. If it returns 1 then the wait handler was successfully cancelled.
|
|
</li>
|
|
<li class="listitem">
|
|
If a wait handler is cancelled, the <a class="link" href="error_code.html" title="error_code"><code class="computeroutput"><span class="identifier">error_code</span></code></a> passed to it contains
|
|
the value <code class="computeroutput"><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>.
|
|
</li>
|
|
</ul></div>
|
|
<p>
|
|
This typedef uses the C++11 <code class="computeroutput"><span class="special"><</span><span class="identifier">chrono</span><span class="special">></span></code>
|
|
standard library facility, if available. Otherwise, it may use the Boost.Chrono
|
|
library. To explicitly utilise Boost.Chrono, use the <a class="link" href="basic_waitable_timer.html" title="basic_waitable_timer"><code class="computeroutput"><span class="identifier">basic_waitable_timer</span></code></a> template directly:
|
|
</p>
|
|
<pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">basic_waitable_timer</span><span class="special"><</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">steady_clock</span><span class="special">></span> <span class="identifier">timer</span><span class="special">;</span>
|
|
</pre>
|
|
<h5>
|
|
<a name="asio.reference.steady_timer.h6"></a>
|
|
<span><a name="asio.reference.steady_timer.requirements"></a></span><a class="link" href="steady_timer.html#asio.reference.steady_timer.requirements">Requirements</a>
|
|
</h5>
|
|
<p>
|
|
<span class="emphasis"><em>Header: </em></span><code class="literal">asio/steady_timer.hpp</code>
|
|
</p>
|
|
<p>
|
|
<span class="emphasis"><em>Convenience header: </em></span><code class="literal">asio.hpp</code>
|
|
</p>
|
|
</div>
|
|
<div class="copyright-footer">Copyright © 2003-2023 Christopher M. Kohlhoff<p>
|
|
Distributed under the Boost Software License, Version 1.0. (See accompanying
|
|
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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</p>
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