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| <pre><span class="sourceLineNo">001</span>/*<a name="line.1"></a> |
| <span class="sourceLineNo">002</span> * Licensed to the Apache Software Foundation (ASF) under one or more<a name="line.2"></a> |
| <span class="sourceLineNo">003</span> * contributor license agreements. See the NOTICE file distributed with<a name="line.3"></a> |
| <span class="sourceLineNo">004</span> * this work for additional information regarding copyright ownership.<a name="line.4"></a> |
| <span class="sourceLineNo">005</span> * The ASF licenses this file to You under the Apache license, Version 2.0<a name="line.5"></a> |
| <span class="sourceLineNo">006</span> * (the "License"); you may not use this file except in compliance with<a name="line.6"></a> |
| <span class="sourceLineNo">007</span> * the License. You may obtain a copy of the License at<a name="line.7"></a> |
| <span class="sourceLineNo">008</span> *<a name="line.8"></a> |
| <span class="sourceLineNo">009</span> * http://www.apache.org/licenses/LICENSE-2.0<a name="line.9"></a> |
| <span class="sourceLineNo">010</span> *<a name="line.10"></a> |
| <span class="sourceLineNo">011</span> * Unless required by applicable law or agreed to in writing, software<a name="line.11"></a> |
| <span class="sourceLineNo">012</span> * distributed under the License is distributed on an "AS IS" BASIS,<a name="line.12"></a> |
| <span class="sourceLineNo">013</span> * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.<a name="line.13"></a> |
| <span class="sourceLineNo">014</span> * See the license for the specific language governing permissions and<a name="line.14"></a> |
| <span class="sourceLineNo">015</span> * limitations under the license.<a name="line.15"></a> |
| <span class="sourceLineNo">016</span> */<a name="line.16"></a> |
| <span class="sourceLineNo">017</span>package org.apache.logging.log4j.core.util;<a name="line.17"></a> |
| <span class="sourceLineNo">018</span><a name="line.18"></a> |
| <span class="sourceLineNo">019</span>import java.lang.reflect.Array;<a name="line.19"></a> |
| <span class="sourceLineNo">020</span><a name="line.20"></a> |
| <span class="sourceLineNo">021</span>/**<a name="line.21"></a> |
| <span class="sourceLineNo">022</span> * A bounded buffer containing elements of type T. When the number of elements to be added will exceed the<a name="line.22"></a> |
| <span class="sourceLineNo">023</span> * size of the buffer the oldest element will be overwritten. Access to the buffer is thread safe.<a name="line.23"></a> |
| <span class="sourceLineNo">024</span> * @param <T> The type of object stored in the buffer.<a name="line.24"></a> |
| <span class="sourceLineNo">025</span> */<a name="line.25"></a> |
| <span class="sourceLineNo">026</span>public final class CyclicBuffer<T> {<a name="line.26"></a> |
| <span class="sourceLineNo">027</span> private final T[] ring;<a name="line.27"></a> |
| <span class="sourceLineNo">028</span> private int first = 0;<a name="line.28"></a> |
| <span class="sourceLineNo">029</span> private int last = 0;<a name="line.29"></a> |
| <span class="sourceLineNo">030</span> private int numElems = 0;<a name="line.30"></a> |
| <span class="sourceLineNo">031</span> private final Class<T> clazz;<a name="line.31"></a> |
| <span class="sourceLineNo">032</span><a name="line.32"></a> |
| <span class="sourceLineNo">033</span> /**<a name="line.33"></a> |
| <span class="sourceLineNo">034</span> * Instantiates a new CyclicBuffer of at most <code>maxSize</code> events.<a name="line.34"></a> |
| <span class="sourceLineNo">035</span> * @param clazz The Class associate with the type of object in the buffer.<a name="line.35"></a> |
| <span class="sourceLineNo">036</span> * @param size The number of items in the buffer.<a name="line.36"></a> |
| <span class="sourceLineNo">037</span> * @throws IllegalArgumentException if the size is negative.<a name="line.37"></a> |
| <span class="sourceLineNo">038</span> */<a name="line.38"></a> |
| <span class="sourceLineNo">039</span> public CyclicBuffer(final Class<T> clazz, final int size) throws IllegalArgumentException {<a name="line.39"></a> |
| <span class="sourceLineNo">040</span> if (size < 0) {<a name="line.40"></a> |
| <span class="sourceLineNo">041</span> throw new IllegalArgumentException("The maxSize argument (" + size + ") cannot be negative.");<a name="line.41"></a> |
| <span class="sourceLineNo">042</span> }<a name="line.42"></a> |
| <span class="sourceLineNo">043</span> this.ring = makeArray(clazz, size);<a name="line.43"></a> |
| <span class="sourceLineNo">044</span> this.clazz = clazz;<a name="line.44"></a> |
| <span class="sourceLineNo">045</span> }<a name="line.45"></a> |
| <span class="sourceLineNo">046</span><a name="line.46"></a> |
| <span class="sourceLineNo">047</span> @SuppressWarnings("unchecked")<a name="line.47"></a> |
| <span class="sourceLineNo">048</span> private T[] makeArray(final Class<T> cls, final int size) {<a name="line.48"></a> |
| <span class="sourceLineNo">049</span> return (T[]) Array.newInstance(cls, size);<a name="line.49"></a> |
| <span class="sourceLineNo">050</span> }<a name="line.50"></a> |
| <span class="sourceLineNo">051</span><a name="line.51"></a> |
| <span class="sourceLineNo">052</span> /**<a name="line.52"></a> |
| <span class="sourceLineNo">053</span> * Adds an item as the last event in the buffer.<a name="line.53"></a> |
| <span class="sourceLineNo">054</span> * @param item The item to add to the buffer.<a name="line.54"></a> |
| <span class="sourceLineNo">055</span> */<a name="line.55"></a> |
| <span class="sourceLineNo">056</span> public synchronized void add(final T item) {<a name="line.56"></a> |
| <span class="sourceLineNo">057</span> if (ring.length > 0) {<a name="line.57"></a> |
| <span class="sourceLineNo">058</span> ring[last] = item;<a name="line.58"></a> |
| <span class="sourceLineNo">059</span> if (++last == ring.length) {<a name="line.59"></a> |
| <span class="sourceLineNo">060</span> last = 0;<a name="line.60"></a> |
| <span class="sourceLineNo">061</span> }<a name="line.61"></a> |
| <span class="sourceLineNo">062</span><a name="line.62"></a> |
| <span class="sourceLineNo">063</span> if (numElems < ring.length) {<a name="line.63"></a> |
| <span class="sourceLineNo">064</span> numElems++;<a name="line.64"></a> |
| <span class="sourceLineNo">065</span> } else if (++first == ring.length) {<a name="line.65"></a> |
| <span class="sourceLineNo">066</span> first = 0;<a name="line.66"></a> |
| <span class="sourceLineNo">067</span> }<a name="line.67"></a> |
| <span class="sourceLineNo">068</span> }<a name="line.68"></a> |
| <span class="sourceLineNo">069</span> }<a name="line.69"></a> |
| <span class="sourceLineNo">070</span><a name="line.70"></a> |
| <span class="sourceLineNo">071</span> /**<a name="line.71"></a> |
| <span class="sourceLineNo">072</span> * Removes all the elements from the buffer and returns them.<a name="line.72"></a> |
| <span class="sourceLineNo">073</span> * @return An array of the elements in the buffer.<a name="line.73"></a> |
| <span class="sourceLineNo">074</span> */<a name="line.74"></a> |
| <span class="sourceLineNo">075</span> public synchronized T[] removeAll() {<a name="line.75"></a> |
| <span class="sourceLineNo">076</span> final T[] array = makeArray(clazz, numElems);<a name="line.76"></a> |
| <span class="sourceLineNo">077</span> int index = 0;<a name="line.77"></a> |
| <span class="sourceLineNo">078</span> while (numElems > 0) {<a name="line.78"></a> |
| <span class="sourceLineNo">079</span> numElems--;<a name="line.79"></a> |
| <span class="sourceLineNo">080</span> array[index++] = ring[first];<a name="line.80"></a> |
| <span class="sourceLineNo">081</span> ring[first] = null;<a name="line.81"></a> |
| <span class="sourceLineNo">082</span> if (++first == ring.length) {<a name="line.82"></a> |
| <span class="sourceLineNo">083</span> first = 0;<a name="line.83"></a> |
| <span class="sourceLineNo">084</span> }<a name="line.84"></a> |
| <span class="sourceLineNo">085</span> }<a name="line.85"></a> |
| <span class="sourceLineNo">086</span> return array;<a name="line.86"></a> |
| <span class="sourceLineNo">087</span> }<a name="line.87"></a> |
| <span class="sourceLineNo">088</span><a name="line.88"></a> |
| <span class="sourceLineNo">089</span> /**<a name="line.89"></a> |
| <span class="sourceLineNo">090</span> * Determines if the buffer contains elements.<a name="line.90"></a> |
| <span class="sourceLineNo">091</span> * @return true if the buffer is empty, false otherwise.<a name="line.91"></a> |
| <span class="sourceLineNo">092</span> */<a name="line.92"></a> |
| <span class="sourceLineNo">093</span> public boolean isEmpty() {<a name="line.93"></a> |
| <span class="sourceLineNo">094</span> return 0 == numElems;<a name="line.94"></a> |
| <span class="sourceLineNo">095</span> }<a name="line.95"></a> |
| <span class="sourceLineNo">096</span>}<a name="line.96"></a> |
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