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| <a name="boost.log.attributes.timer"></a><div class="titlepage"></div> |
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| <h2><span class="refentrytitle">Class timer</span></h2> |
| <p>boost::log::attributes::timer — A class of an attribute that makes an attribute value of the time interval since construction. </p> |
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| <h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2> |
| <div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: <<a class="link" href="../../../attributes.html#header.boost.log.attributes.timer_hpp" title="Header <boost/log/attributes/timer.hpp>">boost/log/attributes/timer.hpp</a>> |
| |
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| <span class="keyword">class</span> <a class="link" href="timer.html" title="Class timer">timer</a> <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">attribute</span> <span class="special">{</span> |
| <span class="keyword">public</span><span class="special">:</span> |
| <span class="comment">// types</span> |
| <span class="keyword">typedef</span> <span class="identifier">utc_time_traits</span><span class="special">::</span><span class="identifier">time_type</span><span class="special">::</span><span class="identifier">time_duration_type</span> <a name="boost.log.attributes.timer.value_type"></a><span class="identifier">value_type</span><span class="special">;</span> <span class="comment">// Attribute value type. </span> |
| |
| <span class="comment">// <a class="link" href="timer.html#boost.log.attributes.timerconstruct-copy-destruct">construct/copy/destruct</a></span> |
| <a class="link" href="timer.html#idp42326224-bb"><span class="identifier">timer</span></a><span class="special">(</span><span class="special">)</span><span class="special">;</span> |
| <span class="keyword">explicit</span> <a class="link" href="timer.html#idp42326944-bb"><span class="identifier">timer</span></a><span class="special">(</span><a class="link" href="cast_source.html" title="Class cast_source">cast_source</a> <span class="keyword">const</span> <span class="special">&</span><span class="special">)</span><span class="special">;</span> |
| <span class="special">}</span><span class="special">;</span></pre></div> |
| <div class="refsect1"> |
| <a name="idp109123200"></a><h2>Description</h2> |
| <p>The timer attribute calculates the time passed since its construction and returns it on value acquisition. The attribute value type is <code class="computeroutput">boost::posix_time::time_duration</code>.</p> |
| <p>On Windows platform there are two implementations of the attribute. The default one is more precise but a bit slower. This version uses <code class="computeroutput">QueryPerformanceFrequence</code>/<code class="computeroutput">QueryPerformanceCounter</code> API to calculate elapsed time.</p> |
| <p>There are known problems with these functions when used with some CPUs, notably AMD Athlon with Cool'n'Quiet technology enabled. See the following links for more information and possible resolutions:</p> |
| <p><a href="http://support.microsoft.com/?scid=kb;en-us;895980" target="_top">http://support.microsoft.com/?scid=kb;en-us;895980</a> <a href="http://support.microsoft.com/?id=896256" target="_top">http://support.microsoft.com/?id=896256</a></p> |
| <p>In case if none of these solutions apply, you are free to define <code class="computeroutput">BOOST_LOG_NO_QUERY_PERFORMANCE_COUNTER</code> macro to fall back to another implementation based on Boost.DateTime. </p> |
| <div class="refsect2"> |
| <a name="idp109129520"></a><h3> |
| <a name="boost.log.attributes.timerconstruct-copy-destruct"></a><code class="computeroutput">timer</code> |
| public |
| construct/copy/destruct</h3> |
| <div class="orderedlist"><ol class="orderedlist" type="1"> |
| <li class="listitem"> |
| <pre class="literallayout"><a name="idp42326224-bb"></a><span class="identifier">timer</span><span class="special">(</span><span class="special">)</span><span class="special">;</span></pre> |
| <p>Constructor. Starts time counting. </p> |
| </li> |
| <li class="listitem"> |
| <pre class="literallayout"><span class="keyword">explicit</span> <a name="idp42326944-bb"></a><span class="identifier">timer</span><span class="special">(</span><a class="link" href="cast_source.html" title="Class cast_source">cast_source</a> <span class="keyword">const</span> <span class="special">&</span> source<span class="special">)</span><span class="special">;</span></pre> |
| <p>Constructor for casting support </p> |
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| <td align="right"><div class="copyright-footer">Copyright © 2007-2015 Andrey |
| Semashev<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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