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| <div class="titlepage"><div><div><h2 class="title" style="clear: both"> |
| <a name="log.defs"></a><a class="link" href="defs.html" title="Definitions">Definitions</a> |
| </h2></div></div></div> |
| <p> |
| Here are definitions of some terms that will be used widely throughout the |
| documentation: |
| </p> |
| <div class="variablelist"> |
| <p class="title"><b></b></p> |
| <dl class="variablelist"> |
| <dt><span class="term">Log record</span></dt> |
| <dd><p> |
| A single bundle of information, collected from the user's application, |
| that is a candidate to be put into the log. In a simple case the log |
| record will be represented as a line of text in the log file after being |
| processed by the logging library. |
| </p></dd> |
| <dt><span class="term">Attribute</span></dt> |
| <dd><p> |
| An "attribute" is a piece of meta-information that can be used |
| to specialize a log record. In Boost.Log attributes are represented by |
| function objects with a specific interface, which return the actual attribute |
| value when invoked. |
| </p></dd> |
| <dt><span class="term">Attribute value</span></dt> |
| <dd><p> |
| Attribute values are the actual data acquired from attributes. This data |
| is attached to the specific log record and processed by the library. |
| Values can have different types (integers, strings and more complex, |
| including user defined types). Some examples of attribute values: current |
| time stamp value, file name, line number, current scope name, etc.. Attribute |
| values are enveloped in a type erasing wrapper, so the actual type of |
| the attribute is not visible in the interface. The actual (erased) type |
| of the value is sometimes called the stored type. |
| </p></dd> |
| <dt><span class="term">(Attribute) value visitation</span></dt> |
| <dd><p> |
| A way of processing the attribute value. This approach involves a function |
| object (a visitor) which is applied to the attribute value. The visitor |
| should know the stored type of the attribute value in order to process |
| it. |
| </p></dd> |
| <dt><span class="term">(Attribute) value extraction</span></dt> |
| <dd><p> |
| A way of processing the attribute value when the caller attempts to obtain |
| a reference to the stored value. The caller should know the stored type |
| of the attribute value in order to be able to extract it. |
| </p></dd> |
| <dt><span class="term">Log sink</span></dt> |
| <dd><p> |
| A target, to which all log records are fed after being collected from |
| the user's application. The sink defines where and how the log records |
| are going to be stored or processed. |
| </p></dd> |
| <dt><span class="term">Log source</span></dt> |
| <dd><p> |
| An entry point for the user's application to put log records to. In a |
| simple case it is an object (logger) which maintains a set of attributes |
| that will be used to form a log record upon the user's request. However, |
| one can surely create a source that would emit log records on some side |
| events (for example, by intercepting and parsing console output of another |
| application). |
| </p></dd> |
| <dt><span class="term">Log filter</span></dt> |
| <dd><p> |
| A predicate that takes a log record and tells whether this record should |
| be passed through or discarded. The predicate typically forms its decision |
| based on the attribute values attached to the record. |
| </p></dd> |
| <dt><span class="term">Log formatter</span></dt> |
| <dd><p> |
| A function object that generates the final textual output from a log |
| record. Some sinks, e.g. a binary logging sink, may not need it, although |
| almost any text-based sink would use a formatter to compose its output. |
| </p></dd> |
| <dt><span class="term">Logging core</span></dt> |
| <dd><p> |
| The global entity that maintains connections between sources and sinks |
| and applies filters to records. It is mainly used when the logging library |
| is initialized. |
| </p></dd> |
| <dt><span class="term">i18n</span></dt> |
| <dd><p> |
| Internationalization. The ability to manipulate wide characters. |
| </p></dd> |
| <dt><span class="term">TLS</span></dt> |
| <dd><p> |
| Thread-local storage. The concept of having a variable that has independent |
| values for each thread that attempts to access it. |
| </p></dd> |
| <dt><span class="term">RTTI</span></dt> |
| <dd><p> |
| Run-time type information. This is the C++ language support data structures |
| required for <code class="computeroutput"><span class="keyword">dynamic_cast</span></code> |
| and <code class="computeroutput"><span class="keyword">typeid</span></code> operators to |
| function properly. |
| </p></dd> |
| </dl> |
| </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> |
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