/*
 * 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.
Type parameters:
<T> – The type of object stored in the buffer./**
 * 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 <T> The type of object stored in the buffer.
 */
public final class CyclicBuffer<T> {
    private final T[] ring;
    private int first = 0;
    private int last = 0;
    private int numElems = 0;
    private final Class<T> clazz;

    
Instantiates a new CyclicBuffer of at most maxSize events.
Params:
clazz – The Class associate with the type of object in the buffer.
size – The number of items in the buffer.
Throws:
IllegalArgumentException – if the size is negative./**
     * Instantiates a new CyclicBuffer of at most <code>maxSize</code> 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<T> 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<T> cls, final int size) {
        return (T[]) Array.newInstance(cls, size);
    }

    
Adds an item as the last event in the buffer.
Params:
item – The item to add to the buffer./**
     * 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.
Returns:
An array of the elements in the buffer./**
     * 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.
Returns:
true if the buffer is empty, false otherwise./**
     * Determines if the buffer contains elements.
     * @return true if the buffer is empty, false otherwise.
     */
    public boolean isEmpty() {
        return 0 == numElems;
    }
}