| /******************************************************************************* |
| * Copyright (c) 1997, 2008 by ProSyst Software GmbH |
| * http://www.prosyst.com |
| * |
| * This program and the accompanying materials |
| * are made available under the terms of the Eclipse Public License 2.0 |
| * which accompanies this distribution, and is available at |
| * https://www.eclipse.org/legal/epl-2.0/ |
| * |
| * SPDX-License-Identifier: EPL-2.0 |
| * |
| * Contributors: |
| * ProSyst Software GmbH - initial API and implementation |
| *******************************************************************************/ |
| |
| package org.eclipse.equinox.internal.util.event; |
| |
| /** |
| * @author Pavlin Dobrev |
| * @version 1.0 |
| */ |
| |
| public class Queue { |
| |
| protected Object[] queue; |
| protected int first, last = -1; |
| protected int initial, count; |
| protected int increment; |
| protected int decrement; |
| |
| public Queue(int size) { |
| queue = new Object[initial = size]; |
| increment = initial / 2; |
| decrement = increment + (increment / 2); |
| } |
| |
| public void put(Object element) { |
| if (count == queue.length) |
| resize(true); |
| queue[++last == queue.length ? last = 0 : last] = element; |
| count++; |
| } |
| |
| public void unget(Object element) { |
| if (count == queue.length) |
| resize(true); |
| queue[--first == -1 ? first = queue.length - 1 : first] = element; |
| count++; |
| } |
| |
| public Object get() { |
| if (count == 0) |
| return null; |
| if (queue.length > initial && queue.length - count > decrement) |
| resize(false); |
| Object element = queue[first]; |
| queue[first++] = null; |
| if (first == queue.length) |
| first = 0; |
| count--; |
| return element; |
| } |
| |
| public void clear() { |
| if (queue.length > initial) { |
| queue = new Object[initial]; |
| count = 0; |
| } else |
| for (; count > 0; count--) { |
| queue[first++] = null; |
| if (first == queue.length) |
| first = 0; |
| } |
| first = 0; |
| last = -1; |
| } |
| |
| public int size() { |
| return count; |
| } |
| |
| protected void resize(boolean up) { |
| Object[] tmp = new Object[queue.length + (up ? increment : -increment)]; |
| if (first <= last) |
| System.arraycopy(queue, first, tmp, 0, count); |
| else { |
| int count1 = queue.length - first; |
| if (count1 > 0) |
| System.arraycopy(queue, first, tmp, 0, count1); |
| if (count > count1) |
| System.arraycopy(queue, 0, tmp, count1, count - count1); |
| } |
| queue = tmp; |
| first = 0; |
| last = count - 1; |
| |
| increment = queue.length / 2; |
| decrement = increment + (increment / 2); |
| } |
| } |