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  26 <div class="titlepage"><div><div><h3 class="title">
  27 <a name="boost_asio.reference.TimerService"></a><a class="link" href="TimerService.html" title="Timer service requirements">Timer service requirements</a>
  28 </h3></div></div></div>
  29 <p>
  30         A timer service must meet the requirements for an <a class="link" href="IoObjectService.html" title="I/O object service requirements">I/O
  31         object service</a>, as well as the additional requirements listed below.
  32       </p>
  33 <p>
  34         In the table below, <code class="computeroutput"><span class="identifier">X</span></code> denotes
  35         a timer service class for time type <code class="computeroutput"><span class="identifier">Time</span></code>
  36         and traits type <code class="computeroutput"><span class="identifier">TimeTraits</span></code>,
  37         <code class="computeroutput"><span class="identifier">a</span></code> denotes a value of type
  38         <code class="computeroutput"><span class="identifier">X</span></code>, <code class="computeroutput"><span class="identifier">b</span></code>
  39         denotes a value of type <code class="computeroutput"><span class="identifier">X</span><span class="special">::</span><span class="identifier">implementation_type</span></code>,
  40         <code class="computeroutput"><span class="identifier">t</span></code> denotes a value of type
  41         <code class="computeroutput"><span class="identifier">Time</span></code>, <code class="computeroutput"><span class="identifier">d</span></code>
  42         denotes a value of type <code class="computeroutput"><span class="identifier">TimeTraits</span><span class="special">::</span><span class="identifier">duration_type</span></code>,
  43         <code class="computeroutput"><span class="identifier">e</span></code> denotes a value of type
  44         <code class="computeroutput"><span class="identifier">error_code</span></code>, and <code class="computeroutput"><span class="identifier">h</span></code> denotes a value meeting <a class="link" href="WaitHandler.html" title="Wait handler requirements"><code class="computeroutput"><span class="identifier">WaitHandler</span></code></a> requirements.
  45       </p>
  46 <div class="table">
  47 <a name="boost_asio.reference.TimerService.t0"></a><p class="title"><b>Table&#160;39.&#160;TimerService requirements</b></p>
  48 <div class="table-contents"><table class="table" summary="TimerService requirements">
  49 <colgroup>
  50 <col>
  51 <col>
  52 <col>
  53 </colgroup>
  54 <thead><tr>
  55 <th>
  56                 <p>
  57                   expression
  58                 </p>
  59               </th>
  60 <th>
  61                 <p>
  62                   return type
  63                 </p>
  64               </th>
  65 <th>
  66                 <p>
  67                   assertion/note<br> pre/post-condition
  68                 </p>
  69               </th>
  70 </tr></thead>
  71 <tbody>
  72 <tr>
  73 <td>
  74                 <p>
  75                   <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">destroy</span><span class="special">(</span><span class="identifier">b</span><span class="special">);</span></code>
  76                 </p>
  77               </td>
  78 <td>
  79               </td>
  80 <td>
  81                 <p>
  82                   From <a class="link" href="IoObjectService.html" title="I/O object service requirements">IoObjectService</a>
  83                   requirements. Implicitly cancels asynchronous wait operations,
  84                   as if by calling <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">cancel</span><span class="special">(</span><span class="identifier">b</span><span class="special">,</span> <span class="identifier">e</span><span class="special">)</span></code>.
  85                 </p>
  86               </td>
  87 </tr>
  88 <tr>
  89 <td>
  90                 <p>
  91 </p>
  92 <pre class="programlisting"><span class="identifier">a</span><span class="special">.</span><span class="identifier">cancel</span><span class="special">(</span><span class="identifier">b</span><span class="special">,</span> <span class="identifier">e</span><span class="special">);</span>
  93 </pre>
  94 <p>
  95                 </p>
  96               </td>
  97 <td>
  98                 <p>
  99                   <code class="computeroutput"><span class="identifier">size_t</span></code>
 100                 </p>
 101               </td>
 102 <td>
 103                 <p>
 104                   Causes any outstanding asynchronous wait operations to complete
 105                   as soon as possible. Handlers for cancelled operations shall be
 106                   passed the error code <code class="computeroutput"><span class="identifier">error</span><span class="special">::</span><span class="identifier">operation_aborted</span></code>.
 107                   Sets <code class="computeroutput"><span class="identifier">e</span></code> to indicate
 108                   success or failure. Returns the number of operations that were
 109                   cancelled.
 110                 </p>
 111               </td>
 112 </tr>
 113 <tr>
 114 <td>
 115                 <p>
 116                   <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">expires_at</span><span class="special">(</span><span class="identifier">b</span><span class="special">);</span></code>
 117                 </p>
 118               </td>
 119 <td>
 120                 <p>
 121                   <code class="computeroutput"><span class="identifier">Time</span></code>
 122                 </p>
 123               </td>
 124 <td>
 125               </td>
 126 </tr>
 127 <tr>
 128 <td>
 129                 <p>
 130 </p>
 131 <pre class="programlisting"><span class="identifier">a</span><span class="special">.</span><span class="identifier">expires_at</span><span class="special">(</span><span class="identifier">b</span><span class="special">,</span> <span class="identifier">t</span><span class="special">,</span> <span class="identifier">e</span><span class="special">);</span>
 132 </pre>
 133 <p>
 134                 </p>
 135               </td>
 136 <td>
 137                 <p>
 138                   <code class="computeroutput"><span class="identifier">size_t</span></code>
 139                 </p>
 140               </td>
 141 <td>
 142                 <p>
 143                   Implicitly cancels asynchronous wait operations, as if by calling
 144                   <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">cancel</span><span class="special">(</span><span class="identifier">b</span><span class="special">,</span>
 145                   <span class="identifier">e</span><span class="special">)</span></code>.
 146                   Returns the number of operations that were cancelled.<br> post:
 147                   <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">expires_at</span><span class="special">(</span><span class="identifier">b</span><span class="special">)</span>
 148                   <span class="special">==</span> <span class="identifier">t</span></code>.
 149                 </p>
 150               </td>
 151 </tr>
 152 <tr>
 153 <td>
 154                 <p>
 155                   <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">expires_from_now</span><span class="special">(</span><span class="identifier">b</span><span class="special">);</span></code>
 156                 </p>
 157               </td>
 158 <td>
 159                 <p>
 160                   <code class="computeroutput"><span class="identifier">TimeTraits</span><span class="special">::</span><span class="identifier">duration_type</span></code>
 161                 </p>
 162               </td>
 163 <td>
 164                 <p>
 165                   Returns a value equivalent to <code class="computeroutput"><span class="identifier">TimeTraits</span><span class="special">::</span><span class="identifier">subtract</span><span class="special">(</span><span class="identifier">a</span><span class="special">.</span><span class="identifier">expires_at</span><span class="special">(</span><span class="identifier">b</span><span class="special">),</span> <span class="identifier">TimeTraits</span><span class="special">::</span><span class="identifier">now</span><span class="special">())</span></code>.
 166                 </p>
 167               </td>
 168 </tr>
 169 <tr>
 170 <td>
 171                 <p>
 172 </p>
 173 <pre class="programlisting"><span class="identifier">a</span><span class="special">.</span><span class="identifier">expires_from_now</span><span class="special">(</span><span class="identifier">b</span><span class="special">,</span> <span class="identifier">d</span><span class="special">,</span> <span class="identifier">e</span><span class="special">);</span>
 174 </pre>
 175 <p>
 176                 </p>
 177               </td>
 178 <td>
 179                 <p>
 180                   <code class="computeroutput"><span class="identifier">size_t</span></code>
 181                 </p>
 182               </td>
 183 <td>
 184                 <p>
 185                   Equivalent to <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">expires_at</span><span class="special">(</span><span class="identifier">b</span><span class="special">,</span> <span class="identifier">TimeTraits</span><span class="special">::</span><span class="identifier">add</span><span class="special">(</span><span class="identifier">TimeTraits</span><span class="special">::</span><span class="identifier">now</span><span class="special">(),</span> <span class="identifier">d</span><span class="special">),</span> <span class="identifier">e</span><span class="special">)</span></code>.
 186                 </p>
 187               </td>
 188 </tr>
 189 <tr>
 190 <td>
 191                 <p>
 192 </p>
 193 <pre class="programlisting"><span class="identifier">a</span><span class="special">.</span><span class="identifier">wait</span><span class="special">(</span><span class="identifier">b</span><span class="special">,</span> <span class="identifier">e</span><span class="special">);</span>
 194 </pre>
 195 <p>
 196                 </p>
 197               </td>
 198 <td>
 199                 <p>
 200                   <code class="computeroutput"><span class="identifier">error_code</span></code>
 201                 </p>
 202               </td>
 203 <td>
 204                 <p>
 205                   Sets <code class="computeroutput"><span class="identifier">e</span></code> to indicate
 206                   success or failure. Returns <code class="computeroutput"><span class="identifier">e</span></code>.<br>
 207                   post: <code class="computeroutput"><span class="special">!!</span><span class="identifier">e</span>
 208                   <span class="special">||</span> <span class="special">!</span><span class="identifier">TimeTraits</span><span class="special">::</span><span class="identifier">lt</span><span class="special">(</span><span class="identifier">TimeTraits</span><span class="special">::</span><span class="identifier">now</span><span class="special">(),</span>
 209                   <span class="identifier">a</span><span class="special">.</span><span class="identifier">expires_at</span><span class="special">(</span><span class="identifier">b</span><span class="special">))</span></code>.
 210                 </p>
 211               </td>
 212 </tr>
 213 <tr>
 214 <td>
 215                 <p>
 216 </p>
 217 <pre class="programlisting"><span class="identifier">a</span><span class="special">.</span><span class="identifier">async_wait</span><span class="special">(</span><span class="identifier">b</span><span class="special">,</span> <span class="identifier">h</span><span class="special">);</span>
 218 </pre>
 219 <p>
 220                 </p>
 221               </td>
 222 <td>
 223               </td>
 224 <td>
 225                 <p>
 226                   Initiates an asynchronous wait operation that is performed via
 227                   the <code class="computeroutput"><span class="identifier">io_service</span></code>
 228                   object <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">get_io_service</span><span class="special">()</span></code>
 229                   and behaves according to <a class="link" href="asynchronous_operations.html" title="Requirements on asynchronous operations">asynchronous
 230                   operation</a> requirements.<br> <br> The handler shall be
 231                   posted for execution only if the condition <code class="computeroutput"><span class="special">!!</span><span class="identifier">ec</span> <span class="special">||</span>
 232                   <span class="special">!</span><span class="identifier">TimeTraits</span><span class="special">::</span><span class="identifier">lt</span><span class="special">(</span><span class="identifier">TimeTraits</span><span class="special">::</span><span class="identifier">now</span><span class="special">(),</span> <span class="identifier">a</span><span class="special">.</span><span class="identifier">expires_at</span><span class="special">(</span><span class="identifier">b</span><span class="special">))</span></code> holds, where <code class="computeroutput"><span class="identifier">ec</span></code>
 233                   is the error code to be passed to the handler.
 234                 </p>
 235               </td>
 236 </tr>
 237 </tbody>
 238 </table></div>
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 240 <br class="table-break">
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 243 <td align="left"></td>
 244 <td align="right"><div class="copyright-footer">Copyright &#169; 2003-2017 Christopher M. Kohlhoff<p>
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 246         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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