CircularBuffer.java

/*
 * Copyright 2010 LinkedIn Corp.
 * 
 * Licensed 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 azkaban.utils;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import com.google.common.base.Joiner;
import com.google.common.collect.Iterators;

/**
 * A circular buffer of items of a given length. It will grow up to the give size as items are appended, then
 * it will begin to overwrite older items.
 *
 * @param <T> The type of the item contained.
 */
public class CircularBuffer<T> implements Iterable<T> {
	
	private final List<T> lines;
	private final int size;
	private int start;
	
	public CircularBuffer(int size) {
		this.lines = new ArrayList<T>();
		this.size = size;
		this.start = 0;
	}
	
	public void append(T line) {
		if(lines.size() < size) {
			lines.add(line);
		} else {
			lines.set(start, line);
			start = (start + 1) % size;
		}
	}
			
	@Override
	public String toString() {
		return "[" + Joiner.on(", ").join(lines) + "]";
	}

	public Iterator<T> iterator() {
		if(start == 0)
			return lines.iterator();
		else
			return Iterators.concat(lines.subList(start, lines.size()).iterator(), lines.subList(0, start).iterator());
	}
	
	public int getMaxSize() {
	    return this.size;
	}
	
	public int getSize() {
	    return this.lines.size();
	}
	
}