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<title>Class: Semaphore</title>
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<td class="file-title"><span class="file-title-prefix">Class</span><br />Semaphore</td>
<td align="right">
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<td>In:</td>
<td>
<a href="../files/lib/more/facets/semaphore_rb.html">lib/more/facets/semaphore.rb</a>
</td>
</tr>
<tr>
<td>Parent:</td>
<td>
Object
</td>
</tr>
</table>
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<div id="bodyContent">
<div id="content">
<div class="description"><h1><a href="Semaphore.html">Semaphore</a></h1>
<p>
Technically a semaphore is simply an integer variable which has an
execution queue associated with it.
</p>
</div>
<div class="sectiontitle">Methods</div>
<span style="padding-right: 5px;"><a href="#M000211">down</a></span>
<span style="padding-right: 5px;"><a href="#M000215">exclusive</a></span>
<span style="padding-right: 5px;"><a href="#M000208">new</a></span>
<span style="padding-right: 5px;"><a href="#M000213">p</a></span>
<span style="padding-right: 5px;"><a href="#M000210">signal</a></span>
<span style="padding-right: 5px;"><a href="#M000216">synchronize</a></span>
<span style="padding-right: 5px;"><a href="#M000212">up</a></span>
<span style="padding-right: 5px;"><a href="#M000214">v</a></span>
<span style="padding-right: 5px;"><a href="#M000209">wait</a></span>
<div class="sectiontitle">Public Class methods</div>
<div class="method">
<div class="title">
<a name="M000208"></a><b>new</b>(initvalue = 0)
</div>
<div class="sourcecode">
<p class="source-link">[ <a href="javascript:toggleSource('M000208_source')" id="l_M000208_source">+</a> ]</p>
<div id="M000208_source" class="dyn-source">
<pre>
<span class="ruby-comment cmt"># File lib/more/facets/semaphore.rb, line 31</span>
<span class="ruby-keyword kw">def</span> <span class="ruby-identifier">initialize</span>(<span class="ruby-identifier">initvalue</span> = <span class="ruby-value">0</span>)
<span class="ruby-ivar">@counter</span> = <span class="ruby-identifier">initvalue</span>
<span class="ruby-ivar">@waiting_list</span> = []
<span class="ruby-keyword kw">end</span>
</pre>
</div>
</div>
</div>
<div class="sectiontitle">Public Instance methods</div>
<div class="method">
<div class="title">
<a name="M000211"></a><b>down</b>()
</div>
<div class="description">
<p>
Alias for <a href="Semaphore.html#M000209">wait</a>
</p>
</div>
</div>
<div class="method">
<div class="title">
<a name="M000215"></a><b>exclusive</b>() {|| ...}
</div>
<div class="aka">
This method is also aliased as
<a href="Semaphore.html#M000216">synchronize</a>
</div>
<div class="sourcecode">
<p class="source-link">[ <a href="javascript:toggleSource('M000215_source')" id="l_M000215_source">+</a> ]</p>
<div id="M000215_source" class="dyn-source">
<pre>
<span class="ruby-comment cmt"># File lib/more/facets/semaphore.rb, line 67</span>
<span class="ruby-keyword kw">def</span> <span class="ruby-identifier">exclusive</span>
<span class="ruby-identifier">wait</span>
<span class="ruby-keyword kw">yield</span>
<span class="ruby-keyword kw">ensure</span>
<span class="ruby-identifier">signal</span>
<span class="ruby-keyword kw">end</span>
</pre>
</div>
</div>
</div>
<div class="method">
<div class="title">
<a name="M000213"></a><b>p</b>()
</div>
<div class="description">
<p>
Alias for <a href="Semaphore.html#M000209">wait</a>
</p>
</div>
</div>
<div class="method">
<div class="title">
<a name="M000210"></a><b>signal</b>()
</div>
<div class="aka">
This method is also aliased as
<a href="Semaphore.html#M000212">up</a>
<a href="Semaphore.html#M000214">v</a>
</div>
<div class="sourcecode">
<p class="source-link">[ <a href="javascript:toggleSource('M000210_source')" id="l_M000210_source">+</a> ]</p>
<div id="M000210_source" class="dyn-source">
<pre>
<span class="ruby-comment cmt"># File lib/more/facets/semaphore.rb, line 47</span>
<span class="ruby-keyword kw">def</span> <span class="ruby-identifier">signal</span>
<span class="ruby-constant">Thread</span>.<span class="ruby-identifier">critical</span> = <span class="ruby-keyword kw">true</span>
<span class="ruby-keyword kw">begin</span>
<span class="ruby-keyword kw">if</span> (<span class="ruby-ivar">@counter</span> <span class="ruby-operator">+=</span> <span class="ruby-value">1</span>) <span class="ruby-operator"><=</span> <span class="ruby-value">0</span>
<span class="ruby-identifier">t</span> = <span class="ruby-ivar">@waiting_list</span>.<span class="ruby-identifier">shift</span>
<span class="ruby-identifier">t</span>.<span class="ruby-identifier">wakeup</span> <span class="ruby-keyword kw">if</span> <span class="ruby-identifier">t</span>
<span class="ruby-keyword kw">end</span>
<span class="ruby-keyword kw">rescue</span> <span class="ruby-constant">ThreadError</span>
<span class="ruby-keyword kw">retry</span>
<span class="ruby-keyword kw">end</span>
<span class="ruby-keyword kw">self</span>
<span class="ruby-keyword kw">ensure</span>
<span class="ruby-constant">Thread</span>.<span class="ruby-identifier">critical</span> = <span class="ruby-keyword kw">false</span>
<span class="ruby-keyword kw">end</span>
</pre>
</div>
</div>
</div>
<div class="method">
<div class="title">
<a name="M000216"></a><b>synchronize</b>()
</div>
<div class="description">
<p>
Alias for <a href="Semaphore.html#M000215">exclusive</a>
</p>
</div>
</div>
<div class="method">
<div class="title">
<a name="M000212"></a><b>up</b>()
</div>
<div class="description">
<p>
Alias for <a href="Semaphore.html#M000210">signal</a>
</p>
</div>
</div>
<div class="method">
<div class="title">
<a name="M000214"></a><b>v</b>()
</div>
<div class="description">
<p>
Alias for <a href="Semaphore.html#M000210">signal</a>
</p>
</div>
</div>
<div class="method">
<div class="title">
<a name="M000209"></a><b>wait</b>()
</div>
<div class="aka">
This method is also aliased as
<a href="Semaphore.html#M000211">down</a>
<a href="Semaphore.html#M000213">p</a>
</div>
<div class="sourcecode">
<p class="source-link">[ <a href="javascript:toggleSource('M000209_source')" id="l_M000209_source">+</a> ]</p>
<div id="M000209_source" class="dyn-source">
<pre>
<span class="ruby-comment cmt"># File lib/more/facets/semaphore.rb, line 36</span>
<span class="ruby-keyword kw">def</span> <span class="ruby-identifier">wait</span>
<span class="ruby-constant">Thread</span>.<span class="ruby-identifier">critical</span> = <span class="ruby-keyword kw">true</span>
<span class="ruby-keyword kw">if</span> (<span class="ruby-ivar">@counter</span> <span class="ruby-operator">-=</span> <span class="ruby-value">1</span>) <span class="ruby-operator"><</span> <span class="ruby-value">0</span>
<span class="ruby-ivar">@waiting_list</span>.<span class="ruby-identifier">push</span>(<span class="ruby-constant">Thread</span>.<span class="ruby-identifier">current</span>)
<span class="ruby-constant">Thread</span>.<span class="ruby-identifier">stop</span>
<span class="ruby-keyword kw">end</span>
<span class="ruby-keyword kw">self</span>
<span class="ruby-keyword kw">ensure</span>
<span class="ruby-constant">Thread</span>.<span class="ruby-identifier">critical</span> = <span class="ruby-keyword kw">false</span>
<span class="ruby-keyword kw">end</span>
</pre>
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