doc/html/boost_asio/reference/high_resolution_timer.html

   1 <html>
   2 <head>
   3 <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
   4 <title>high_resolution_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="get_associated_executor/overload3.html" title="get_associated_executor (3 of 3 overloads)">
  10 <link rel="next" href="invalid_service_owner.html" title="invalid_service_owner">
  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 href="../../../../libs/libraries.htm">Libraries</a></td>
  17 <td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
  18 <td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
  19 <td align="center"><a href="../../../../more/index.htm">More</a></td>
  20 </tr></table>
  21 <hr>
  22 <div class="spirit-nav">
  23 <a accesskey="p" href="get_associated_executor/overload3.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="invalid_service_owner.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a>
  24 </div>
  25 <div class="section">
  26 <div class="titlepage"><div><div><h3 class="title">
  27 <a name="boost_asio.reference.high_resolution_timer"></a><a class="link" href="high_resolution_timer.html" title="high_resolution_timer">high_resolution_timer</a>
  28 </h3></div></div></div>
  29 <p>
  30         <a class="indexterm" name="boost_asio.indexterm.high_resolution_timer"></a>
  31 Typedef for
  32         a timer based on the high resolution clock.
  33       </p>
  34 <pre class="programlisting">typedef basic_waitable_timer&lt; chrono::high_resolution_clock &gt; high_resolution_timer;
  35 </pre>
  36 <h5>
  37 <a name="boost_asio.reference.high_resolution_timer.h0"></a>
  38         <span class="phrase"><a name="boost_asio.reference.high_resolution_timer.types"></a></span><a class="link" href="high_resolution_timer.html#boost_asio.reference.high_resolution_timer.types">Types</a>
  39       </h5>
  40 <div class="informaltable"><table class="table">
  41 <colgroup>
  42 <col>
  43 <col>
  44 </colgroup>
  45 <thead><tr>
  46 <th>
  47                 <p>
  48                   Name
  49                 </p>
  50               </th>
  51 <th>
  52                 <p>
  53                   Description
  54                 </p>
  55               </th>
  56 </tr></thead>
  57 <tbody>
  58 <tr>
  59 <td>
  60                 <p>
  61                   <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>
  62                 </p>
  63               </td>
  64 <td>
  65                 <p>
  66                   The clock type.
  67                 </p>
  68               </td>
  69 </tr>
  70 <tr>
  71 <td>
  72                 <p>
  73                   <a class="link" href="basic_waitable_timer/duration.html" title="basic_waitable_timer::duration"><span class="bold"><strong>duration</strong></span></a>
  74                 </p>
  75               </td>
  76 <td>
  77                 <p>
  78                   The duration type of the clock.
  79                 </p>
  80               </td>
  81 </tr>
  82 <tr>
  83 <td>
  84                 <p>
  85                   <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>
  86                 </p>
  87               </td>
  88 <td>
  89                 <p>
  90                   The type of the executor associated with the object.
  91                 </p>
  92               </td>
  93 </tr>
  94 <tr>
  95 <td>
  96                 <p>
  97                   <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>
  98                 </p>
  99               </td>
 100 <td>
 101                 <p>
 102                   The time point type of the clock.
 103                 </p>
 104               </td>
 105 </tr>
 106 <tr>
 107 <td>
 108                 <p>
 109                   <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>
 110                 </p>
 111               </td>
 112 <td>
 113                 <p>
 114                   The wait traits type.
 115                 </p>
 116               </td>
 117 </tr>
 118 </tbody>
 119 </table></div>
 120 <h5>
 121 <a name="boost_asio.reference.high_resolution_timer.h1"></a>
 122         <span class="phrase"><a name="boost_asio.reference.high_resolution_timer.member_functions"></a></span><a class="link" href="high_resolution_timer.html#boost_asio.reference.high_resolution_timer.member_functions">Member
 123         Functions</a>
 124       </h5>
 125 <div class="informaltable"><table class="table">
 126 <colgroup>
 127 <col>
 128 <col>
 129 </colgroup>
 130 <thead><tr>
 131 <th>
 132                 <p>
 133                   Name
 134                 </p>
 135               </th>
 136 <th>
 137                 <p>
 138                   Description
 139                 </p>
 140               </th>
 141 </tr></thead>
 142 <tbody>
 143 <tr>
 144 <td>
 145                 <p>
 146                   <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>
 147                 </p>
 148               </td>
 149 <td>
 150                 <p>
 151                   Start an asynchronous wait on the timer.
 152                 </p>
 153               </td>
 154 </tr>
 155 <tr>
 156 <td>
 157                 <p>
 158                   <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>
 159                 </p>
 160               </td>
 161 <td>
 162                 <p>
 163                   Constructor. <br> <span class="silver"> &#8212;</span><br> Constructor to set a particular expiry
 164                   time as an absolute time. <br> <span class="silver"> &#8212;</span><br> Constructor to set a particular
 165                   expiry time relative to now. <br> <span class="silver"> &#8212;</span><br> Move-construct a basic_waitable_timer
 166                   from another.
 167                 </p>
 168               </td>
 169 </tr>
 170 <tr>
 171 <td>
 172                 <p>
 173                   <a class="link" href="basic_waitable_timer/cancel.html" title="basic_waitable_timer::cancel"><span class="bold"><strong>cancel</strong></span></a>
 174                 </p>
 175               </td>
 176 <td>
 177                 <p>
 178                   Cancel any asynchronous operations that are waiting on the timer.
 179                   <br> <span class="silver"> &#8212;</span><br> (Deprecated: Use non-error_code overload.) Cancel
 180                   any asynchronous operations that are waiting on the timer.
 181                 </p>
 182               </td>
 183 </tr>
 184 <tr>
 185 <td>
 186                 <p>
 187                   <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>
 188                 </p>
 189               </td>
 190 <td>
 191                 <p>
 192                   Cancels one asynchronous operation that is waiting on the timer.
 193                   <br> <span class="silver"> &#8212;</span><br> (Deprecated: Use non-error_code overload.) Cancels
 194                   one asynchronous operation that is waiting on the timer.
 195                 </p>
 196               </td>
 197 </tr>
 198 <tr>
 199 <td>
 200                 <p>
 201                   <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>
 202                 </p>
 203               </td>
 204 <td>
 205                 <p>
 206                   Set the timer's expiry time relative to now.
 207                 </p>
 208               </td>
 209 </tr>
 210 <tr>
 211 <td>
 212                 <p>
 213                   <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>
 214                 </p>
 215               </td>
 216 <td>
 217                 <p>
 218                   (Deprecated: Use expiry().) Get the timer's expiry time as an absolute
 219                   time. <br> <span class="silver"> &#8212;</span><br> Set the timer's expiry time as an absolute
 220                   time. <br> <span class="silver"> &#8212;</span><br> (Deprecated: Use non-error_code overload.)
 221                   Set the timer's expiry time as an absolute time.
 222                 </p>
 223               </td>
 224 </tr>
 225 <tr>
 226 <td>
 227                 <p>
 228                   <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>
 229                 </p>
 230               </td>
 231 <td>
 232                 <p>
 233                   (Deprecated: Use expiry().) Get the timer's expiry time relative
 234                   to now. <br> <span class="silver"> &#8212;</span><br> (Deprecated: Use expires_after().) Set the
 235                   timer's expiry time relative to now.
 236                 </p>
 237               </td>
 238 </tr>
 239 <tr>
 240 <td>
 241                 <p>
 242                   <a class="link" href="basic_waitable_timer/expiry.html" title="basic_waitable_timer::expiry"><span class="bold"><strong>expiry</strong></span></a>
 243                 </p>
 244               </td>
 245 <td>
 246                 <p>
 247                   Get the timer's expiry time as an absolute time.
 248                 </p>
 249               </td>
 250 </tr>
 251 <tr>
 252 <td>
 253                 <p>
 254                   <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>
 255                 </p>
 256               </td>
 257 <td>
 258                 <p>
 259                   Get the executor associated with the object.
 260                 </p>
 261               </td>
 262 </tr>
 263 <tr>
 264 <td>
 265                 <p>
 266                   <a class="link" href="basic_waitable_timer/operator_eq_.html" title="basic_waitable_timer::operator="><span class="bold"><strong>operator=</strong></span></a>
 267                 </p>
 268               </td>
 269 <td>
 270                 <p>
 271                   Move-assign a basic_waitable_timer from another.
 272                 </p>
 273               </td>
 274 </tr>
 275 <tr>
 276 <td>
 277                 <p>
 278                   <a class="link" href="basic_waitable_timer/wait.html" title="basic_waitable_timer::wait"><span class="bold"><strong>wait</strong></span></a>
 279                 </p>
 280               </td>
 281 <td>
 282                 <p>
 283                   Perform a blocking wait on the timer.
 284                 </p>
 285               </td>
 286 </tr>
 287 <tr>
 288 <td>
 289                 <p>
 290                   <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>
 291                 </p>
 292               </td>
 293 <td>
 294                 <p>
 295                   Destroys the timer.
 296                 </p>
 297               </td>
 298 </tr>
 299 </tbody>
 300 </table></div>
 301 <p>
 302         The <a class="link" href="basic_waitable_timer.html" title="basic_waitable_timer"><code class="computeroutput">basic_waitable_timer</code></a>
 303         class template provides the ability to perform a blocking or asynchronous
 304         wait for a timer to expire.
 305       </p>
 306 <p>
 307         A waitable timer is always in one of two states: "expired" or "not
 308         expired". If the <code class="computeroutput">wait()</code> or <code class="computeroutput">async_wait()</code> function
 309         is called on an expired timer, the wait operation will complete immediately.
 310       </p>
 311 <p>
 312         Most applications will use one of the <a class="link" href="steady_timer.html" title="steady_timer"><code class="computeroutput">steady_timer</code></a>,
 313         <a class="link" href="system_timer.html" title="system_timer"><code class="computeroutput">system_timer</code></a>
 314         or <a class="link" href="high_resolution_timer.html" title="high_resolution_timer"><code class="computeroutput">high_resolution_timer</code></a>
 315         typedefs.
 316       </p>
 317 <h5>
 318 <a name="boost_asio.reference.high_resolution_timer.h2"></a>
 319         <span class="phrase"><a name="boost_asio.reference.high_resolution_timer.remarks"></a></span><a class="link" href="high_resolution_timer.html#boost_asio.reference.high_resolution_timer.remarks">Remarks</a>
 320       </h5>
 321 <p>
 322         This waitable timer functionality is for use with the C++11 standard library's
 323         <code class="computeroutput">&lt;chrono&gt;</code> facility, or with the Boost.Chrono library.
 324       </p>
 325 <h5>
 326 <a name="boost_asio.reference.high_resolution_timer.h3"></a>
 327         <span class="phrase"><a name="boost_asio.reference.high_resolution_timer.thread_safety"></a></span><a class="link" href="high_resolution_timer.html#boost_asio.reference.high_resolution_timer.thread_safety">Thread
 328         Safety</a>
 329       </h5>
 330 <p>
 331         <span class="emphasis"><em>Distinct</em></span> <span class="emphasis"><em>objects:</em></span> Safe.
 332       </p>
 333 <p>
 334         <span class="emphasis"><em>Shared</em></span> <span class="emphasis"><em>objects:</em></span> Unsafe.
 335       </p>
 336 <h5>
 337 <a name="boost_asio.reference.high_resolution_timer.h4"></a>
 338         <span class="phrase"><a name="boost_asio.reference.high_resolution_timer.examples"></a></span><a class="link" href="high_resolution_timer.html#boost_asio.reference.high_resolution_timer.examples">Examples</a>
 339       </h5>
 340 <p>
 341         Performing a blocking wait (C++11):
 342       </p>
 343 <pre class="programlisting">// Construct a timer without setting an expiry time.
 344 boost::asio::steady_timer timer(my_context);
 345
 346 // Set an expiry time relative to now.
 347 timer.expires_after(std::chrono::seconds(5));
 348
 349 // Wait for the timer to expire.
 350 timer.wait();
 351 </pre>
 352 <p>
 353         Performing an asynchronous wait (C++11):
 354       </p>
 355 <pre class="programlisting">void handler(const boost::system::error_code&amp; error)
 356 {
 357   if (!error)
 358   {
 359     // Timer expired.
 360   }
 361 }
 362
 363 ...
 364
 365 // Construct a timer with an absolute expiry time.
 366 boost::asio::steady_timer timer(my_context,
 367     std::chrono::steady_clock::now() + std::chrono::seconds(60));
 368
 369 // Start an asynchronous wait.
 370 timer.async_wait(handler);
 371 </pre>
 372 <h5>
 373 <a name="boost_asio.reference.high_resolution_timer.h5"></a>
 374         <span class="phrase"><a name="boost_asio.reference.high_resolution_timer.changing_an_active_waitable_timer_s_expiry_time"></a></span><a class="link" href="high_resolution_timer.html#boost_asio.reference.high_resolution_timer.changing_an_active_waitable_timer_s_expiry_time">Changing
 375         an active waitable timer's expiry time</a>
 376       </h5>
 377 <p>
 378         Changing the expiry time of a timer while there are pending asynchronous
 379         waits causes those wait operations to be cancelled. To ensure that the action
 380         associated with the timer is performed only once, use something like this:
 381         used:
 382       </p>
 383 <pre class="programlisting">void on_some_event()
 384 {
 385   if (my_timer.expires_after(seconds(5)) &gt; 0)
 386   {
 387     // We managed to cancel the timer. Start new asynchronous wait.
 388     my_timer.async_wait(on_timeout);
 389   }
 390   else
 391   {
 392     // Too late, timer has already expired!
 393   }
 394 }
 395
 396 void on_timeout(const boost::system::error_code&amp; e)
 397 {
 398   if (e != boost::asio::error::operation_aborted)
 399   {
 400     // Timer was not cancelled, take necessary action.
 401   }
 402 }
 403 </pre>
 404 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
 405 <li class="listitem">
 406             The <code class="computeroutput">boost::asio::basic_waitable_timer::expires_after()</code> function
 407             cancels any pending asynchronous waits, and returns the number of asynchronous
 408             waits that were cancelled. If it returns 0 then you were too late and
 409             the wait handler has already been executed, or will soon be executed.
 410             If it returns 1 then the wait handler was successfully cancelled.
 411           </li>
 412 <li class="listitem">
 413             If a wait handler is cancelled, the boost::system::error_code passed
 414             to it contains the value <code class="computeroutput">boost::asio::error::operation_aborted</code>.
 415           </li>
 416 </ul></div>
 417 <p>
 418         This typedef uses the C++11 <code class="computeroutput">&lt;chrono&gt;</code> standard library
 419         facility, if available. Otherwise, it may use the Boost.Chrono library. To
 420         explicitly utilise Boost.Chrono, use the <a class="link" href="basic_waitable_timer.html" title="basic_waitable_timer"><code class="computeroutput">basic_waitable_timer</code></a>
 421         template directly:
 422       </p>
 423 <pre class="programlisting">typedef basic_waitable_timer&lt;boost::chrono::high_resolution_clock&gt; timer;
 424 </pre>
 425 <h5>
 426 <a name="boost_asio.reference.high_resolution_timer.h6"></a>
 427         <span class="phrase"><a name="boost_asio.reference.high_resolution_timer.requirements"></a></span><a class="link" href="high_resolution_timer.html#boost_asio.reference.high_resolution_timer.requirements">Requirements</a>
 428       </h5>
 429 <p>
 430         <span class="emphasis"><em>Header: </em></span><code class="literal">boost/asio/high_resolution_timer.hpp</code>
 431       </p>
 432 <p>
 433         <span class="emphasis"><em>Convenience header: </em></span><code class="literal">boost/asio.hpp</code>
 434       </p>
 435 </div>
 436 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 437 <td align="left"></td>
 438 <td align="right"><div class="copyright-footer">Copyright &#169; 2003-2019 Christopher M. Kohlhoff<p>
 439         Distributed under the Boost Software License, Version 1.0. (See accompanying
 440         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>)
 441       </p>
 442 </div></td>
 443 </tr></table>
 444 <hr>
 445 <div class="spirit-nav">
 446 <a accesskey="p" href="get_associated_executor/overload3.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="invalid_service_owner.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a>
 447 </div>
 448 </body>
 449 </html>