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<div class="titlepage"><div><div><h3 class="title">
<a name="asio.reference.basic_deadline_timer"></a><a class="link" href="basic_deadline_timer.html" title="basic_deadline_timer">basic_deadline_timer</a>
</h3></div></div></div>
<p>
<a class="indexterm" name="asio.indexterm.basic_deadline_timer"></a>
</p>
<p>
Provides waitable timer functionality.
</p>
<pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span>
<span class="keyword">typename</span> <span class="identifier">Time</span><span class="special">,</span>
<span class="keyword">typename</span> <a class="link" href="TimeTraits.html" title="Time traits requirements">TimeTraits</a> <span class="special">=</span> <span class="identifier">asio</span><span class="special">::</span><span class="identifier">time_traits</span><span class="special">&lt;</span><span class="identifier">Time</span><span class="special">&gt;,</span>
<span class="keyword">typename</span> <a class="link" href="Executor1.html" title="Executor requirements">Executor</a> <span class="special">=</span> <span class="identifier">any_io_executor</span><span class="special">&gt;</span>
<span class="keyword">class</span> <span class="identifier">basic_deadline_timer</span>
</pre>
<h5>
<a name="asio.reference.basic_deadline_timer.h0"></a>
<span><a name="asio.reference.basic_deadline_timer.types"></a></span><a class="link" href="basic_deadline_timer.html#asio.reference.basic_deadline_timer.types">Types</a>
</h5>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
<p>
Name
</p>
</th>
<th>
<p>
Description
</p>
</th>
</tr></thead>
<tbody>
<tr>
<td>
<p>
<a class="link" href="basic_deadline_timer__rebind_executor.html" title="basic_deadline_timer::rebind_executor"><span class="bold"><strong>rebind_executor</strong></span></a>
</p>
</td>
<td>
<p>
Rebinds the timer type to another executor.
</p>
</td>
</tr>
<tr>
<td>
<p>
<a class="link" href="basic_deadline_timer/duration_type.html" title="basic_deadline_timer::duration_type"><span class="bold"><strong>duration_type</strong></span></a>
</p>
</td>
<td>
<p>
The duration type.
</p>
</td>
</tr>
<tr>
<td>
<p>
<a class="link" href="basic_deadline_timer/executor_type.html" title="basic_deadline_timer::executor_type"><span class="bold"><strong>executor_type</strong></span></a>
</p>
</td>
<td>
<p>
The type of the executor associated with the object.
</p>
</td>
</tr>
<tr>
<td>
<p>
<a class="link" href="basic_deadline_timer/time_type.html" title="basic_deadline_timer::time_type"><span class="bold"><strong>time_type</strong></span></a>
</p>
</td>
<td>
<p>
The time type.
</p>
</td>
</tr>
<tr>
<td>
<p>
<a class="link" href="basic_deadline_timer/traits_type.html" title="basic_deadline_timer::traits_type"><span class="bold"><strong>traits_type</strong></span></a>
</p>
</td>
<td>
<p>
The time traits type.
</p>
</td>
</tr>
</tbody>
</table></div>
<h5>
<a name="asio.reference.basic_deadline_timer.h1"></a>
<span><a name="asio.reference.basic_deadline_timer.member_functions"></a></span><a class="link" href="basic_deadline_timer.html#asio.reference.basic_deadline_timer.member_functions">Member Functions</a>
</h5>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
<p>
Name
</p>
</th>
<th>
<p>
Description
</p>
</th>
</tr></thead>
<tbody>
<tr>
<td>
<p>
<a class="link" href="basic_deadline_timer/async_wait.html" title="basic_deadline_timer::async_wait"><span class="bold"><strong>async_wait</strong></span></a>
</p>
</td>
<td>
<p>
Start an asynchronous wait on the timer.
</p>
</td>
</tr>
<tr>
<td>
<p>
<a class="link" href="basic_deadline_timer/basic_deadline_timer.html" title="basic_deadline_timer::basic_deadline_timer"><span class="bold"><strong>basic_deadline_timer</strong></span></a> <span class="silver">[constructor]</span>
</p>
</td>
<td>
<p>
Constructor. <br> <span class="silver"> —</span><br> Constructor to set a particular expiry
time as an absolute time. <br> <span class="silver"> —</span><br> Constructor to set a particular
expiry time relative to now. <br> <span class="silver"> —</span><br> Move-construct a basic_deadline_timer
from another.
</p>
</td>
</tr>
<tr>
<td>
<p>
<a class="link" href="basic_deadline_timer/cancel.html" title="basic_deadline_timer::cancel"><span class="bold"><strong>cancel</strong></span></a>
</p>
</td>
<td>
<p>
Cancel any asynchronous operations that are waiting on the timer.
</p>
</td>
</tr>
<tr>
<td>
<p>
<a class="link" href="basic_deadline_timer/cancel_one.html" title="basic_deadline_timer::cancel_one"><span class="bold"><strong>cancel_one</strong></span></a>
</p>
</td>
<td>
<p>
Cancels one asynchronous operation that is waiting on the timer.
</p>
</td>
</tr>
<tr>
<td>
<p>
<a class="link" href="basic_deadline_timer/expires_at.html" title="basic_deadline_timer::expires_at"><span class="bold"><strong>expires_at</strong></span></a>
</p>
</td>
<td>
<p>
Get the timer's expiry time as an absolute time. <br> <span class="silver"> —</span><br>
Set the timer's expiry time as an absolute time.
</p>
</td>
</tr>
<tr>
<td>
<p>
<a class="link" href="basic_deadline_timer/expires_from_now.html" title="basic_deadline_timer::expires_from_now"><span class="bold"><strong>expires_from_now</strong></span></a>
</p>
</td>
<td>
<p>
Get the timer's expiry time relative to now. <br> <span class="silver"> —</span><br> Set
the timer's expiry time relative to now.
</p>
</td>
</tr>
<tr>
<td>
<p>
<a class="link" href="basic_deadline_timer/get_executor.html" title="basic_deadline_timer::get_executor"><span class="bold"><strong>get_executor</strong></span></a>
</p>
</td>
<td>
<p>
Get the executor associated with the object.
</p>
</td>
</tr>
<tr>
<td>
<p>
<a class="link" href="basic_deadline_timer/operator_eq_.html" title="basic_deadline_timer::operator="><span class="bold"><strong>operator=</strong></span></a>
</p>
</td>
<td>
<p>
Move-assign a basic_deadline_timer from another.
</p>
</td>
</tr>
<tr>
<td>
<p>
<a class="link" href="basic_deadline_timer/wait.html" title="basic_deadline_timer::wait"><span class="bold"><strong>wait</strong></span></a>
</p>
</td>
<td>
<p>
Perform a blocking wait on the timer.
</p>
</td>
</tr>
<tr>
<td>
<p>
<a class="link" href="basic_deadline_timer/_basic_deadline_timer.html" title="basic_deadline_timer::~basic_deadline_timer"><span class="bold"><strong>~basic_deadline_timer</strong></span></a> <span class="silver">[destructor]</span>
</p>
</td>
<td>
<p>
Destroys the timer.
</p>
</td>
</tr>
</tbody>
</table></div>
<p>
The <a class="link" href="basic_deadline_timer.html" title="basic_deadline_timer"><code class="computeroutput"><span class="identifier">basic_deadline_timer</span></code></a>
class template provides the ability to perform a blocking or asynchronous
wait for a timer to expire.
</p>
<p>
A deadline timer is always in one of two states: "expired" or "not
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,
the wait operation will complete immediately.
</p>
<p>
Most applications will use the <a class="link" href="deadline_timer.html" title="deadline_timer"><code class="computeroutput"><span class="identifier">deadline_timer</span></code></a> typedef.
</p>
<h5>
<a name="asio.reference.basic_deadline_timer.h2"></a>
<span><a name="asio.reference.basic_deadline_timer.thread_safety"></a></span><a class="link" href="basic_deadline_timer.html#asio.reference.basic_deadline_timer.thread_safety">Thread
Safety</a>
</h5>
<p>
<span class="emphasis"><em>Distinct</em></span> <span class="emphasis"><em>objects:</em></span> Safe.
</p>
<p>
<span class="emphasis"><em>Shared</em></span> <span class="emphasis"><em>objects:</em></span> Unsafe.
</p>
<h5>
<a name="asio.reference.basic_deadline_timer.h3"></a>
<span><a name="asio.reference.basic_deadline_timer.examples"></a></span><a class="link" href="basic_deadline_timer.html#asio.reference.basic_deadline_timer.examples">Examples</a>
</h5>
<p>
Performing a blocking wait:
</p>
<pre class="programlisting"><span class="comment">// Construct a timer without setting an expiry time.</span>
<span class="identifier">asio</span><span class="special">::</span><span class="identifier">deadline_timer</span> <span class="identifier">timer</span><span class="special">(</span><span class="identifier">my_context</span><span class="special">);</span>
<span class="comment">// Set an expiry time relative to now.</span>
<span class="identifier">timer</span><span class="special">.</span><span class="identifier">expires_from_now</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">posix_time</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="comment">// Wait for the timer to expire.</span>
<span class="identifier">timer</span><span class="special">.</span><span class="identifier">wait</span><span class="special">();</span>
</pre>
<p>
Performing an asynchronous wait:
</p>
<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">&amp;</span> <span class="identifier">error</span><span class="special">)</span>
<span class="special">{</span>
<span class="keyword">if</span> <span class="special">(!</span><span class="identifier">error</span><span class="special">)</span>
<span class="special">{</span>
<span class="comment">// Timer expired.</span>
<span class="special">}</span>
<span class="special">}</span>
<span class="special">...</span>
<span class="comment">// Construct a timer with an absolute expiry time.</span>
<span class="identifier">asio</span><span class="special">::</span><span class="identifier">deadline_timer</span> <span class="identifier">timer</span><span class="special">(</span><span class="identifier">my_context</span><span class="special">,</span>
<span class="identifier">boost</span><span class="special">::</span><span class="identifier">posix_time</span><span class="special">::</span><span class="identifier">time_from_string</span><span class="special">(</span><span class="string">"2005-12-07 23:59:59.000"</span><span class="special">));</span>
<span class="comment">// Start an asynchronous wait.</span>
<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>
</pre>
<h5>
<a name="asio.reference.basic_deadline_timer.h4"></a>
<span><a name="asio.reference.basic_deadline_timer.changing_an_active_deadline_timer_s_expiry_time"></a></span><a class="link" href="basic_deadline_timer.html#asio.reference.basic_deadline_timer.changing_an_active_deadline_timer_s_expiry_time">Changing
an active deadline_timer's expiry time</a>
</h5>
<p>
Changing the expiry time of a timer while there are pending asynchronous
waits causes those wait operations to be cancelled. To ensure that the action
associated with the timer is performed only once, use something like this:
used:
</p>
<pre class="programlisting"><span class="keyword">void</span> <span class="identifier">on_some_event</span><span class="special">()</span>
<span class="special">{</span>
<span class="keyword">if</span> <span class="special">(</span><span class="identifier">my_timer</span><span class="special">.</span><span class="identifier">expires_from_now</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">&gt;</span> <span class="number">0</span><span class="special">)</span>
<span class="special">{</span>
<span class="comment">// We managed to cancel the timer. Start new asynchronous wait.</span>
<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>
<span class="special">}</span>
<span class="keyword">else</span>
<span class="special">{</span>
<span class="comment">// Too late, timer has already expired!</span>
<span class="special">}</span>
<span class="special">}</span>
<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">&amp;</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_deadline_timer</span><span class="special">::</span><span class="identifier">expires_from_now</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>
<h5>
<a name="asio.reference.basic_deadline_timer.h5"></a>
<span><a name="asio.reference.basic_deadline_timer.requirements"></a></span><a class="link" href="basic_deadline_timer.html#asio.reference.basic_deadline_timer.requirements">Requirements</a>
</h5>
<p>
<span class="emphasis"><em>Header: </em></span><code class="literal">asio/basic_deadline_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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