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<h1><a class="anchor" name="channel">RLog Channels</a></h1>An RLog Channel is a naming method for logging messages.<p>
All logs are associated with a single channel, however there a variety of ways of subscribing to a log message.<h2><a class="anchor" name="hierarchy">
Channel Hierarchy</a></h2>
Channels are hierarchical. For example, if a log message is published on the "debug" channel: <div class="fragment"><pre class="fragment"> <a class="code" href="group__RLogMacros.html#ge8be8a2d2e9da76cb70e2f29e0801f73">rDebug</a>(<span class="stringliteral">"hi"</span>);
<span class="comment">// same as</span>
<span class="keyword">static</span> RLogChannel *myChannel = <a class="code" href="rlog_8h.html#ae55883696f0d46d890824be09d70d5d">DEF_CHANNEL</a>(<span class="stringliteral">"debug"</span>, Log_Debug);
<a class="code" href="group__RLogMacros.html#g95004cecec660f509c3e9af03608aa7d">rLog</a>(myChannel, <span class="stringliteral">"hi"</span>);
</pre></div><p>
In the example above, all subscribers to the "debug" channel receive the messages, but <em>not</em> subscribers to "debug/foo" or other sub-channels.<p>
If a log is published under "debug/foo/bar": <div class="fragment"><pre class="fragment"> <span class="keyword">static</span> RLogChannel *myChannel = <a class="code" href="rlog_8h.html#ae55883696f0d46d890824be09d70d5d">DEF_CHANNEL</a>(<span class="stringliteral">"debug/foo/bar"</span>, Log_Debug);
<a class="code" href="group__RLogMacros.html#g95004cecec660f509c3e9af03608aa7d">rLog</a>(myChannel, <span class="stringliteral">"hi"</span>);
</pre></div><p>
In that example, all subscribers to "debug/foo/bar", "debug/foo", and "debug" will receive the message.<p>
All channels are considered to be derived from a root channel. It doesn't have a true name and is referenced as the empty string "". So, to capture <em>all</em> messages: <div class="fragment"><pre class="fragment"> <span class="comment">// capture all messages and log them to stderr</span>
StdioNode stdLog( STDERR_FILENO );
stdLog.subscribeTo( GetGlobalChannel(<span class="stringliteral">""</span>) ); <span class="comment">// empty string is root channel</span>
</pre></div><h2><a class="anchor" name="channelcomponents">
Channel Components</a></h2>
Or in mathematical terms, the cross product of channels and components.<p>
Channels are componentized. By default, all log messages using one of the rLog type macros is actually published on the component-specific version of the channel (the component being the value of RLOG_COMPONENT at compile time). So, instead of just saying a message was published on "debug" channel, we need to also say which component it was part of, which we could represent as a pair ( < COMPONENT, CHANNEL > ) -- eg <"rlog", "debug">.<p>
This means that two separate components, both using <a class="el" href="group__RLogMacros.html#ge8be8a2d2e9da76cb70e2f29e0801f73">rDebug()</a> (for example) could be subscribed to separately, or together.<p>
There is a way to subscribe to channels in the following ways:<ul>
<li><COMPONENT, CHANNEL> : subscribe to a particular channel from a component</li><li><COMPONENT, *> : subscribe to all channels from a component</li><li><*, CHANNEL> : subscribe to a channel from <em>all</em> components</li><li><*, *> : subscribe to all channels from all components</li></ul>
<p>
<div class="fragment"><pre class="fragment">{
<span class="comment">// this is published on the channel "debug", and the component</span>
<span class="comment">// [RLOG_COMPONENT]</span>
<a class="code" href="group__RLogMacros.html#ge8be8a2d2e9da76cb70e2f29e0801f73">rDebug</a>(<span class="stringliteral">"hi"</span>);
StdioNode stdLog( STDERR_FILENO );
<span class="comment">// subscribe to a particular channel, from the current component</span>
<span class="comment">// ([RLOG_COMPONENT])</span>
stdLog.subscribeTo( RLOG_CHANNEL(<span class="stringliteral">"debug/foo"</span>) );
<span class="comment">// subscribe to all channels from the current component ([RLOG_COMPONENT])</span>
<span class="comment">// (the root channel is the empty string "")</span>
stdLog.subscribeTo( RLOG_CHANNEL(<span class="stringliteral">""</span>) );
<span class="comment">// subscribe to a particular channel from all components</span>
stdLog.subscribeTo( GetGlobalChannel(<span class="stringliteral">"debug/foo"</span>) );
<span class="comment">// subscribe to all channels from all components</span>
stdLog.subscribeTo( GetGlobalChannel(<span class="stringliteral">""</span>) );
}
</pre></div><p>
As you can see from the pattern above, using the RLOG_CHANNEL() macro limits the selection to the current component. If you want to specify a component other then the current component, use GetComponentChannel() which takes the component name as the first argument. <hr size="1"><address style="align: right;"><small>Generated on Mon Nov 20 22:57:44 2006 for rlog by
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