org.apache.logging.log4j.core.util.CyclicBuffer Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache license, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the license for the specific language governing permissions and
* limitations under the license.
*/
package org.apache.logging.log4j.core.util;
import java.lang.reflect.Array;
/**
* A bounded buffer containing elements of type T. When the number of elements to be added will exceed the
* size of the buffer the oldest element will be overwritten. Access to the buffer is thread safe.
* @param The type of object stored in the buffer.
*/
public final class CyclicBuffer {
private final T[] ring;
private int first = 0;
private int last = 0;
private int numElems = 0;
private final Class clazz;
/**
* Instantiates a new CyclicBuffer of at most maxSize
events.
* @param clazz The Class associate with the type of object in the buffer.
* @param size The number of items in the buffer.
* @throws IllegalArgumentException if the size is negative.
*/
public CyclicBuffer(final Class clazz, final int size) throws IllegalArgumentException {
if (size < 0) {
throw new IllegalArgumentException("The maxSize argument (" + size + ") cannot be negative.");
}
this.ring = makeArray(clazz, size);
this.clazz = clazz;
}
@SuppressWarnings("unchecked")
private T[] makeArray(final Class cls, final int size) {
return (T[]) Array.newInstance(cls, size);
}
/**
* Adds an item as the last event in the buffer.
* @param item The item to add to the buffer.
*/
public synchronized void add(final T item) {
if (ring.length > 0) {
ring[last] = item;
if (++last == ring.length) {
last = 0;
}
if (numElems < ring.length) {
numElems++;
} else if (++first == ring.length) {
first = 0;
}
}
}
/**
* Removes all the elements from the buffer and returns them.
* @return An array of the elements in the buffer.
*/
public synchronized T[] removeAll() {
final T[] array = makeArray(clazz, numElems);
int index = 0;
while (numElems > 0) {
numElems--;
array[index++] = ring[first];
ring[first] = null;
if (++first == ring.length) {
first = 0;
}
}
return array;
}
/**
* Determines if the buffer contains elements.
* @return true if the buffer is empty, false otherwise.
*/
public boolean isEmpty() {
return 0 == numElems;
}
}