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| <div class="refentry"> |
| <a name="boost.log.attribute"></a><div class="titlepage"></div> |
| <div class="refnamediv"> |
| <h2><span class="refentrytitle">Class attribute</span></h2> |
| <p>boost::log::attribute — A base class for an attribute value factory. </p> |
| </div> |
| <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.attribute_hpp" title="Header <boost/log/attributes/attribute.hpp>">boost/log/attributes/attribute.hpp</a>> |
| |
| </span> |
| <span class="keyword">class</span> <a class="link" href="attribute.html" title="Class attribute">attribute</a> <span class="special">{</span> |
| <span class="keyword">public</span><span class="special">:</span> |
| <span class="comment">// member classes/structs/unions</span> |
| |
| <span class="comment">// A base class for an attribute value factory.</span> |
| |
| <span class="keyword">struct</span> <a class="link" href="attribute/impl.html" title="Struct impl">impl</a> <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">intrusive_ref_counter</span><span class="special"><</span> <span class="identifier">impl</span> <span class="special">></span> <span class="special">{</span> |
| <span class="comment">// <a class="link" href="attribute/impl.html#boost.log.attribute.implconstruct-copy-destruct">construct/copy/destruct</a></span> |
| <a class="link" href="attribute/impl.html#idp40323216-bb"><span class="special">~</span><span class="identifier">impl</span></a><span class="special">(</span><span class="special">)</span><span class="special">;</span> |
| |
| <span class="comment">// <a class="link" href="attribute/impl.html#idp27715552-bb">public member functions</a></span> |
| <span class="keyword">virtual</span> <a class="link" href="attribute_value.html" title="Class attribute_value">attribute_value</a> <a class="link" href="attribute/impl.html#idp27716112-bb"><span class="identifier">get_value</span></a><span class="special">(</span><span class="special">)</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span> |
| |
| <span class="comment">// <a class="link" href="attribute/impl.html#idp40323792-bb">public static functions</a></span> |
| <span class="keyword">static</span> <span class="keyword">void</span> <span class="special">*</span> <a class="link" href="attribute/impl.html#idp40324352-bb"><span class="keyword">operator</span> <span class="keyword">new</span></a><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span><span class="special">)</span><span class="special">;</span> |
| <span class="keyword">static</span> <span class="keyword">void</span> <a class="link" href="attribute/impl.html#idp40326160-bb"><span class="keyword">operator</span> <span class="keyword">delete</span></a><span class="special">(</span><span class="keyword">void</span> <span class="special">*</span><span class="special">,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span> |
| <span class="special">}</span><span class="special">;</span> |
| <span class="comment">// <a class="link" href="attribute.html#boost.log.attributeconstruct-copy-destruct">construct/copy/destruct</a></span> |
| <a class="link" href="attribute.html#idp40338080-bb"><span class="identifier">attribute</span></a><span class="special">(</span><span class="special">)</span> <span class="special">=</span> <span class="keyword">default</span><span class="special">;</span> |
| <a class="link" href="attribute.html#idp40082816-bb"><span class="identifier">attribute</span></a><span class="special">(</span><a class="link" href="attribute.html" title="Class attribute">attribute</a> <span class="keyword">const</span> <span class="special">&</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span> |
| <a class="link" href="attribute.html#idp40084768-bb"><span class="identifier">attribute</span></a><span class="special">(</span><a class="link" href="attribute.html" title="Class attribute">attribute</a> <span class="special">&&</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span> |
| <span class="keyword">explicit</span> <a class="link" href="attribute.html#idp40086720-bb"><span class="identifier">attribute</span></a><span class="special">(</span><span class="identifier">intrusive_ptr</span><span class="special"><</span> <a class="link" href="attribute/impl.html" title="Struct impl">impl</a> <span class="special">></span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span> |
| <a class="link" href="attribute.html" title="Class attribute">attribute</a> <span class="special">&</span> <a class="link" href="attribute.html#idp40090304-bb"><span class="keyword">operator</span><span class="special">=</span></a><span class="special">(</span><a class="link" href="attribute.html" title="Class attribute">attribute</a> <span class="keyword">const</span> <span class="special">&</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span> |
| <a class="link" href="attribute.html" title="Class attribute">attribute</a> <span class="special">&</span> <a class="link" href="attribute.html#idp40092832-bb"><span class="keyword">operator</span><span class="special">=</span></a><span class="special">(</span><a class="link" href="attribute.html" title="Class attribute">attribute</a> <span class="special">&&</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span> |
| |
| <span class="comment">// <a class="link" href="attribute.html#idp40329088-bb">public member functions</a></span> |
| <span class="keyword">explicit</span> <a class="link" href="attribute.html#idp40329648-bb"><span class="keyword">operator</span> <span class="keyword">bool</span></a><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span> |
| <span class="keyword">bool</span> <a class="link" href="attribute.html#idp40331696-bb"><span class="keyword">operator</span><span class="special">!</span></a><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span> |
| <a class="link" href="attribute_value.html" title="Class attribute_value">attribute_value</a> <a class="link" href="attribute.html#idp40333264-bb"><span class="identifier">get_value</span></a><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span> |
| <span class="keyword">void</span> <a class="link" href="attribute.html#idp40335440-bb"><span class="identifier">swap</span></a><span class="special">(</span><a class="link" href="attribute.html" title="Class attribute">attribute</a> <span class="special">&</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span> |
| |
| <span class="comment">// <a class="link" href="attribute.html#idp40095360-bb">protected member functions</a></span> |
| <a class="link" href="attribute/impl.html" title="Struct impl">impl</a> <span class="special">*</span> <a class="link" href="attribute.html#idp40095936-bb"><span class="identifier">get_impl</span></a><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span> |
| <span class="keyword">void</span> <a class="link" href="attribute.html#idp40098192-bb"><span class="identifier">set_impl</span></a><span class="special">(</span><span class="identifier">intrusive_ptr</span><span class="special"><</span> <a class="link" href="attribute/impl.html" title="Struct impl">impl</a> <span class="special">></span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span> |
| |
| <span class="comment">// <a class="link" href="attribute.html#idp41479392-bb">friend functions</a></span> |
| <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> T<span class="special">></span> <span class="keyword">friend</span> <span class="identifier">T</span> <a class="link" href="attribute.html#idp41479952-bb"><span class="identifier">attribute_cast</span></a><span class="special">(</span><a class="link" href="attribute.html" title="Class attribute">attribute</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="idp104064608"></a><h2>Description</h2> |
| <p>Every attribute is represented with a factory that is basically an attribute value generator. The sole purpose of an attribute is to return an actual value when requested. A simplest attribute can always return the same value that it stores internally, but more complex ones can perform a considerable amount of work to return a value, and the returned values may differ each time requested.</p> |
| <p>A word about thread safety. An attribute should be prepared to be requested a value from multiple threads concurrently. </p> |
| <div class="refsect2"> |
| <a name="idp104066080"></a><h3> |
| <a name="boost.log.attributeconstruct-copy-destruct"></a><code class="computeroutput">attribute</code> |
| public |
| construct/copy/destruct</h3> |
| <div class="orderedlist"><ol class="orderedlist" type="1"> |
| <li class="listitem"> |
| <pre class="literallayout"><a name="idp40338080-bb"></a><span class="identifier">attribute</span><span class="special">(</span><span class="special">)</span> <span class="special">=</span> <span class="keyword">default</span><span class="special">;</span></pre> |
| <p>Default constructor. Creates an empty attribute value factory, which is not usable until <code class="computeroutput">set_impl</code> is called. </p> |
| </li> |
| <li class="listitem"> |
| <pre class="literallayout"><a name="idp40082816-bb"></a><span class="identifier">attribute</span><span class="special">(</span><a class="link" href="attribute.html" title="Class attribute">attribute</a> <span class="keyword">const</span> <span class="special">&</span> that<span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></pre> |
| <p>Copy constructor </p> |
| </li> |
| <li class="listitem"> |
| <pre class="literallayout"><a name="idp40084768-bb"></a><span class="identifier">attribute</span><span class="special">(</span><a class="link" href="attribute.html" title="Class attribute">attribute</a> <span class="special">&&</span> that<span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></pre> |
| <p>Move constructor </p> |
| </li> |
| <li class="listitem"> |
| <pre class="literallayout"><span class="keyword">explicit</span> <a name="idp40086720-bb"></a><span class="identifier">attribute</span><span class="special">(</span><span class="identifier">intrusive_ptr</span><span class="special"><</span> <a class="link" href="attribute/impl.html" title="Struct impl">impl</a> <span class="special">></span> p<span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></pre> |
| <p>Initializing constructor</p> |
| <p> |
| </p> |
| <div class="variablelist"><table border="0" class="variablelist compact"> |
| <colgroup> |
| <col align="left" valign="top"> |
| <col> |
| </colgroup> |
| <tbody><tr> |
| <td><p><span class="term">Parameters:</span></p></td> |
| <td><div class="variablelist"><table border="0" class="variablelist compact"> |
| <colgroup> |
| <col align="left" valign="top"> |
| <col> |
| </colgroup> |
| <tbody><tr> |
| <td><p><span class="term"><code class="computeroutput">p</code></span></p></td> |
| <td><p>Pointer to the implementation. Must not be <code class="computeroutput">NULL</code>. </p></td> |
| </tr></tbody> |
| </table></div></td> |
| </tr></tbody> |
| </table></div> |
| </li> |
| <li class="listitem"> |
| <pre class="literallayout"><a class="link" href="attribute.html" title="Class attribute">attribute</a> <span class="special">&</span> <a name="idp40090304-bb"></a><span class="keyword">operator</span><span class="special">=</span><span class="special">(</span><a class="link" href="attribute.html" title="Class attribute">attribute</a> <span class="keyword">const</span> <span class="special">&</span> that<span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></pre> |
| <p>Copy assignment </p> |
| </li> |
| <li class="listitem"> |
| <pre class="literallayout"><a class="link" href="attribute.html" title="Class attribute">attribute</a> <span class="special">&</span> <a name="idp40092832-bb"></a><span class="keyword">operator</span><span class="special">=</span><span class="special">(</span><a class="link" href="attribute.html" title="Class attribute">attribute</a> <span class="special">&&</span> that<span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></pre> |
| <p>Move assignment </p> |
| </li> |
| </ol></div> |
| </div> |
| <div class="refsect2"> |
| <a name="idp104116320"></a><h3> |
| <a name="idp40329088-bb"></a><code class="computeroutput">attribute</code> public member functions</h3> |
| <div class="orderedlist"><ol class="orderedlist" type="1"> |
| <li class="listitem"> |
| <pre class="literallayout"><span class="keyword">explicit</span> <a name="idp40329648-bb"></a><span class="keyword">operator</span> <span class="keyword">bool</span><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span></pre> |
| <p>Verifies that the factory is not in empty state </p> |
| </li> |
| <li class="listitem"> |
| <pre class="literallayout"><span class="keyword">bool</span> <a name="idp40331696-bb"></a><span class="keyword">operator</span><span class="special">!</span><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span></pre> |
| <p>Verifies that the factory is in empty state </p> |
| </li> |
| <li class="listitem"> |
| <pre class="literallayout"><a class="link" href="attribute_value.html" title="Class attribute_value">attribute_value</a> <a name="idp40333264-bb"></a><span class="identifier">get_value</span><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span></pre> |
| <p> |
| </p> |
| <div class="variablelist"><table border="0" class="variablelist compact"> |
| <colgroup> |
| <col align="left" valign="top"> |
| <col> |
| </colgroup> |
| <tbody><tr> |
| <td><p><span class="term">Returns:</span></p></td> |
| <td><p>The actual attribute value. It shall not return empty values (exceptions shall be used to indicate errors). </p></td> |
| </tr></tbody> |
| </table></div> |
| </li> |
| <li class="listitem"> |
| <pre class="literallayout"><span class="keyword">void</span> <a name="idp40335440-bb"></a><span class="identifier">swap</span><span class="special">(</span><a class="link" href="attribute.html" title="Class attribute">attribute</a> <span class="special">&</span> that<span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></pre> |
| <p>The method swaps two factories (i.e. their implementations). </p> |
| </li> |
| </ol></div> |
| </div> |
| <div class="refsect2"> |
| <a name="idp104145440"></a><h3> |
| <a name="idp40095360-bb"></a><code class="computeroutput">attribute</code> protected member functions</h3> |
| <div class="orderedlist"><ol class="orderedlist" type="1"> |
| <li class="listitem"> |
| <pre class="literallayout"><a class="link" href="attribute/impl.html" title="Struct impl">impl</a> <span class="special">*</span> <a name="idp40095936-bb"></a><span class="identifier">get_impl</span><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span></pre> |
| <p> |
| </p> |
| <div class="variablelist"><table border="0" class="variablelist compact"> |
| <colgroup> |
| <col align="left" valign="top"> |
| <col> |
| </colgroup> |
| <tbody><tr> |
| <td><p><span class="term">Returns:</span></p></td> |
| <td><p>The pointer to the implementation </p></td> |
| </tr></tbody> |
| </table></div> |
| </li> |
| <li class="listitem"> |
| <pre class="literallayout"><span class="keyword">void</span> <a name="idp40098192-bb"></a><span class="identifier">set_impl</span><span class="special">(</span><span class="identifier">intrusive_ptr</span><span class="special"><</span> <a class="link" href="attribute/impl.html" title="Struct impl">impl</a> <span class="special">></span> p<span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></pre> |
| <p>Sets the pointer to the factory implementation.</p> |
| <p> |
| </p> |
| <div class="variablelist"><table border="0" class="variablelist compact"> |
| <colgroup> |
| <col align="left" valign="top"> |
| <col> |
| </colgroup> |
| <tbody><tr> |
| <td><p><span class="term">Parameters:</span></p></td> |
| <td><div class="variablelist"><table border="0" class="variablelist compact"> |
| <colgroup> |
| <col align="left" valign="top"> |
| <col> |
| </colgroup> |
| <tbody><tr> |
| <td><p><span class="term"><code class="computeroutput">p</code></span></p></td> |
| <td><p>Pointer to the implementation. Must not be <code class="computeroutput">NULL</code>. </p></td> |
| </tr></tbody> |
| </table></div></td> |
| </tr></tbody> |
| </table></div> |
| </li> |
| </ol></div> |
| </div> |
| <div class="refsect2"> |
| <a name="idp104167824"></a><h3> |
| <a name="idp41479392-bb"></a><code class="computeroutput">attribute</code> friend functions</h3> |
| <div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"> |
| <pre class="literallayout"><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> T<span class="special">></span> <span class="keyword">friend</span> <span class="identifier">T</span> <a name="idp41479952-bb"></a><span class="identifier">attribute_cast</span><span class="special">(</span><a class="link" href="attribute.html" title="Class attribute">attribute</a> <span class="keyword">const</span> <span class="special">&</span><span class="special">)</span><span class="special">;</span></pre> |
| <p>The function casts one attribute factory to another </p> |
| </li></ol></div> |
| </div> |
| </div> |
| </div> |
| <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> |
| <td align="left"></td> |
| <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>). |
| </p> |
| </div></td> |
| </tr></table> |
| <hr> |
| <div class="spirit-nav"> |
| <a accesskey="p" href="../../attributes.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../attributes.html#header.boost.log.attributes.attribute_hpp"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="attribute/impl.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> |
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