001/* 002 * Trident - A Multithreaded Server Alternative 003 * Copyright 2014 The TridentSDK Team 004 * 005 * Licensed under the Apache License, Version 2.0 (the "License"); 006 * you may not use this file except in compliance with the License. 007 * You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017 018package net.tridentsdk.server.util; 019 020import com.google.common.collect.Iterators; 021 022import javax.annotation.concurrent.ThreadSafe; 023import java.util.Iterator; 024import java.util.concurrent.locks.Lock; 025import java.util.concurrent.locks.ReentrantLock; 026 027/** 028 * A thread safe implementation of a Circular array 029 * 030 * <p>A simple data structure that will overwrite the oldest value when a new one is added, keeping it at a 031 * fixed length</p> 032 */ 033@ThreadSafe 034public class ConcurrentCircularArray<E> implements Iterable<E> { 035 private final Object[] list; 036 private final int size; 037 038 private final Lock lock = new ReentrantLock(); 039 private int index = 0; 040 041 public ConcurrentCircularArray(int size) { 042 this.list = new Object[size]; 043 this.size = size; 044 } 045 046 public void add(E item) { 047 lock.lock(); 048 try { 049 if (index == size) index = 0; 050 list[index] = item; 051 index++; 052 } finally { 053 lock.unlock(); 054 } 055 } 056 057 @Override 058 public Iterator<E> iterator() { 059 lock.lock(); 060 try { 061 return Iterators.transform(Iterators.forArray(list), e -> (E) e); 062 } finally { 063 lock.unlock(); 064 } 065 } 066}