1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>basic_waitable_timer</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="../reference.html" title="Reference"> 9<link rel="prev" href="basic_system_executor/require/overload7.html" title="basic_system_executor::require (7 of 7 overloads)"> 10<link rel="next" href="basic_waitable_timer/async_wait.html" title="basic_waitable_timer::async_wait"> 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 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href="basic_waitable_timer.html" title="basic_waitable_timer">basic_waitable_timer</a> 28</h3></div></div></div> 29<p> 30 Provides waitable timer functionality. 31 </p> 32<pre class="programlisting">template< 33 typename Clock, 34 typename <a class="link" href="WaitTraits.html" title="Wait traits requirements">WaitTraits</a>, 35 typename <a class="link" href="Executor1.html" title="Executor requirements">Executor</a>> 36class basic_waitable_timer 37</pre> 38<h5> 39<a name="boost_asio.reference.basic_waitable_timer.h0"></a> 40 <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> 41 </h5> 42<div class="informaltable"><table class="table"> 43<colgroup> 44<col> 45<col> 46</colgroup> 47<thead><tr> 48<th> 49 <p> 50 Name 51 </p> 52 </th> 53<th> 54 <p> 55 Description 56 </p> 57 </th> 58</tr></thead> 59<tbody> 60<tr> 61<td> 62 <p> 63 <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> 64 </p> 65 </td> 66<td> 67 <p> 68 Rebinds the timer type to another executor. 69 </p> 70 </td> 71</tr> 72<tr> 73<td> 74 <p> 75 <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> 76 </p> 77 </td> 78<td> 79 <p> 80 The clock type. 81 </p> 82 </td> 83</tr> 84<tr> 85<td> 86 <p> 87 <a class="link" href="basic_waitable_timer/duration.html" title="basic_waitable_timer::duration"><span class="bold"><strong>duration</strong></span></a> 88 </p> 89 </td> 90<td> 91 <p> 92 The duration type of the clock. 93 </p> 94 </td> 95</tr> 96<tr> 97<td> 98 <p> 99 <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> 100 </p> 101 </td> 102<td> 103 <p> 104 The type of the executor associated with the object. 105 </p> 106 </td> 107</tr> 108<tr> 109<td> 110 <p> 111 <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> 112 </p> 113 </td> 114<td> 115 <p> 116 The time point type of the clock. 117 </p> 118 </td> 119</tr> 120<tr> 121<td> 122 <p> 123 <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> 124 </p> 125 </td> 126<td> 127 <p> 128 The wait traits type. 129 </p> 130 </td> 131</tr> 132</tbody> 133</table></div> 134<h5> 135<a name="boost_asio.reference.basic_waitable_timer.h1"></a> 136 <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 137 Functions</a> 138 </h5> 139<div class="informaltable"><table class="table"> 140<colgroup> 141<col> 142<col> 143</colgroup> 144<thead><tr> 145<th> 146 <p> 147 Name 148 </p> 149 </th> 150<th> 151 <p> 152 Description 153 </p> 154 </th> 155</tr></thead> 156<tbody> 157<tr> 158<td> 159 <p> 160 <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> 161 </p> 162 </td> 163<td> 164 <p> 165 Start an asynchronous wait on the timer. 166 </p> 167 </td> 168</tr> 169<tr> 170<td> 171 <p> 172 <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> 173 </p> 174 </td> 175<td> 176 <p> 177 Constructor. <br> <span class="silver"> —</span><br> Constructor to set a particular expiry 178 time as an absolute time. <br> <span class="silver"> —</span><br> Constructor to set a particular 179 expiry time relative to now. <br> <span class="silver"> —</span><br> Move-construct a basic_waitable_timer 180 from another. 181 </p> 182 </td> 183</tr> 184<tr> 185<td> 186 <p> 187 <a class="link" href="basic_waitable_timer/cancel.html" title="basic_waitable_timer::cancel"><span class="bold"><strong>cancel</strong></span></a> 188 </p> 189 </td> 190<td> 191 <p> 192 Cancel any asynchronous operations that are waiting on the timer. 193 <br> <span class="silver"> —</span><br> (Deprecated: Use non-error_code overload.) Cancel 194 any asynchronous operations that are waiting on the timer. 195 </p> 196 </td> 197</tr> 198<tr> 199<td> 200 <p> 201 <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> 202 </p> 203 </td> 204<td> 205 <p> 206 Cancels one asynchronous operation that is waiting on the timer. 207 <br> <span class="silver"> —</span><br> (Deprecated: Use non-error_code overload.) Cancels 208 one asynchronous operation that is waiting on the timer. 209 </p> 210 </td> 211</tr> 212<tr> 213<td> 214 <p> 215 <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> 216 </p> 217 </td> 218<td> 219 <p> 220 Set the timer's expiry time relative to now. 221 </p> 222 </td> 223</tr> 224<tr> 225<td> 226 <p> 227 <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> 228 </p> 229 </td> 230<td> 231 <p> 232 (Deprecated: Use expiry().) Get the timer's expiry time as an absolute 233 time. <br> <span class="silver"> —</span><br> Set the timer's expiry time as an absolute 234 time. <br> <span class="silver"> —</span><br> (Deprecated: Use non-error_code overload.) 235 Set the timer's expiry time as an absolute time. 236 </p> 237 </td> 238</tr> 239<tr> 240<td> 241 <p> 242 <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> 243 </p> 244 </td> 245<td> 246 <p> 247 (Deprecated: Use expiry().) Get the timer's expiry time relative 248 to now. <br> <span class="silver"> —</span><br> (Deprecated: Use expires_after().) Set the 249 timer's expiry time relative to now. 250 </p> 251 </td> 252</tr> 253<tr> 254<td> 255 <p> 256 <a class="link" href="basic_waitable_timer/expiry.html" title="basic_waitable_timer::expiry"><span class="bold"><strong>expiry</strong></span></a> 257 </p> 258 </td> 259<td> 260 <p> 261 Get the timer's expiry time as an absolute time. 262 </p> 263 </td> 264</tr> 265<tr> 266<td> 267 <p> 268 <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> 269 </p> 270 </td> 271<td> 272 <p> 273 Get the executor associated with the object. 274 </p> 275 </td> 276</tr> 277<tr> 278<td> 279 <p> 280 <a class="link" href="basic_waitable_timer/operator_eq_.html" title="basic_waitable_timer::operator="><span class="bold"><strong>operator=</strong></span></a> 281 </p> 282 </td> 283<td> 284 <p> 285 Move-assign a basic_waitable_timer from another. 286 </p> 287 </td> 288</tr> 289<tr> 290<td> 291 <p> 292 <a class="link" href="basic_waitable_timer/wait.html" title="basic_waitable_timer::wait"><span class="bold"><strong>wait</strong></span></a> 293 </p> 294 </td> 295<td> 296 <p> 297 Perform a blocking wait on the timer. 298 </p> 299 </td> 300</tr> 301<tr> 302<td> 303 <p> 304 <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> 305 </p> 306 </td> 307<td> 308 <p> 309 Destroys the timer. 310 </p> 311 </td> 312</tr> 313</tbody> 314</table></div> 315<p> 316 The <a class="link" href="basic_waitable_timer.html" title="basic_waitable_timer"><code class="computeroutput">basic_waitable_timer</code></a> 317 class template provides the ability to perform a blocking or asynchronous 318 wait for a timer to expire. 319 </p> 320<p> 321 A waitable timer is always in one of two states: "expired" or "not 322 expired". If the <code class="computeroutput">wait()</code> or <code class="computeroutput">async_wait()</code> function 323 is called on an expired timer, the wait operation will complete immediately. 324 </p> 325<p> 326 Most applications will use one of the <a class="link" href="steady_timer.html" title="steady_timer"><code class="computeroutput">steady_timer</code></a>, 327 <a class="link" href="system_timer.html" title="system_timer"><code class="computeroutput">system_timer</code></a> 328 or <a class="link" href="high_resolution_timer.html" title="high_resolution_timer"><code class="computeroutput">high_resolution_timer</code></a> 329 typedefs. 330 </p> 331<h5> 332<a name="boost_asio.reference.basic_waitable_timer.h2"></a> 333 <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> 334 </h5> 335<p> 336 This waitable timer functionality is for use with the C++11 standard library's 337 <code class="computeroutput"><chrono></code> facility, or with the Boost.Chrono library. 338 </p> 339<h5> 340<a name="boost_asio.reference.basic_waitable_timer.h3"></a> 341 <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 342 Safety</a> 343 </h5> 344<p> 345 <span class="emphasis"><em>Distinct</em></span> <span class="emphasis"><em>objects:</em></span> Safe. 346 </p> 347<p> 348 <span class="emphasis"><em>Shared</em></span> <span class="emphasis"><em>objects:</em></span> Unsafe. 349 </p> 350<h5> 351<a name="boost_asio.reference.basic_waitable_timer.h4"></a> 352 <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> 353 </h5> 354<p> 355 Performing a blocking wait (C++11): 356 </p> 357<pre class="programlisting">// Construct a timer without setting an expiry time. 358boost::asio::steady_timer timer(my_context); 359 360// Set an expiry time relative to now. 361timer.expires_after(std::chrono::seconds(5)); 362 363// Wait for the timer to expire. 364timer.wait(); 365</pre> 366<p> 367 Performing an asynchronous wait (C++11): 368 </p> 369<pre class="programlisting">void handler(const boost::system::error_code& error) 370{ 371 if (!error) 372 { 373 // Timer expired. 374 } 375} 376 377... 378 379// Construct a timer with an absolute expiry time. 380boost::asio::steady_timer timer(my_context, 381 std::chrono::steady_clock::now() + std::chrono::seconds(60)); 382 383// Start an asynchronous wait. 384timer.async_wait(handler); 385</pre> 386<h5> 387<a name="boost_asio.reference.basic_waitable_timer.h5"></a> 388 <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 389 an active waitable timer's expiry time</a> 390 </h5> 391<p> 392 Changing the expiry time of a timer while there are pending asynchronous 393 waits causes those wait operations to be cancelled. To ensure that the action 394 associated with the timer is performed only once, use something like this: 395 used: 396 </p> 397<pre class="programlisting">void on_some_event() 398{ 399 if (my_timer.expires_after(seconds(5)) > 0) 400 { 401 // We managed to cancel the timer. Start new asynchronous wait. 402 my_timer.async_wait(on_timeout); 403 } 404 else 405 { 406 // Too late, timer has already expired! 407 } 408} 409 410void on_timeout(const boost::system::error_code& e) 411{ 412 if (e != boost::asio::error::operation_aborted) 413 { 414 // Timer was not cancelled, take necessary action. 415 } 416} 417</pre> 418<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 419<li class="listitem"> 420 The <code class="computeroutput">boost::asio::basic_waitable_timer::expires_after()</code> function 421 cancels any pending asynchronous waits, and returns the number of asynchronous 422 waits that were cancelled. If it returns 0 then you were too late and 423 the wait handler has already been executed, or will soon be executed. 424 If it returns 1 then the wait handler was successfully cancelled. 425 </li> 426<li class="listitem"> 427 If a wait handler is cancelled, the boost::system::error_code passed 428 to it contains the value <code class="computeroutput">boost::asio::error::operation_aborted</code>. 429 </li> 430</ul></div> 431<h5> 432<a name="boost_asio.reference.basic_waitable_timer.h6"></a> 433 <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> 434 </h5> 435<p> 436 <span class="emphasis"><em>Header: </em></span><code class="literal">boost/asio/basic_waitable_timer.hpp</code> 437 </p> 438<p> 439 <span class="emphasis"><em>Convenience header: </em></span><code class="literal">boost/asio.hpp</code> 440 </p> 441</div> 442<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 443<td align="left"></td> 444<td align="right"><div class="copyright-footer">Copyright © 2003-2020 Christopher M. 445 Kohlhoff<p> 446 Distributed under the Boost Software License, Version 1.0. (See accompanying 447 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>) 448 </p> 449</div></td> 450</tr></table> 451<hr> 452<div class="spirit-nav"> 453<a accesskey="p" href="basic_system_executor/require/overload7.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../reference.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="basic_waitable_timer/async_wait.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a> 454</div> 455</body> 456</html> 457
