0N/A/*
2362N/A * Copyright (c) 1996, 2005, Oracle and/or its affiliates. All rights reserved.
0N/A * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
0N/A *
0N/A * This code is free software; you can redistribute it and/or modify it
0N/A * under the terms of the GNU General Public License version 2 only, as
2362N/A * published by the Free Software Foundation. Oracle designates this
0N/A * particular file as subject to the "Classpath" exception as provided
2362N/A * by Oracle in the LICENSE file that accompanied this code.
0N/A *
0N/A * This code is distributed in the hope that it will be useful, but WITHOUT
0N/A * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
0N/A * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
0N/A * version 2 for more details (a copy is included in the LICENSE file that
0N/A * accompanied this code).
0N/A *
0N/A * You should have received a copy of the GNU General Public License version
0N/A * 2 along with this work; if not, write to the Free Software Foundation,
0N/A * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
0N/A *
2362N/A * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
2362N/A * or visit www.oracle.com if you need additional information or have any
2362N/A * questions.
0N/A */
0N/A
0N/Apackage sun.misc;
0N/A
0N/Aimport java.util.Enumeration;
0N/Aimport java.util.NoSuchElementException;
0N/A
0N/A/**
0N/A * Queue: implements a simple queue mechanism. Allows for enumeration of the
0N/A * elements.
0N/A *
0N/A * @author Herb Jellinek
0N/A */
0N/A
0N/Apublic class Queue {
0N/A
0N/A int length = 0;
0N/A
0N/A QueueElement head = null;
0N/A QueueElement tail = null;
0N/A
0N/A public Queue() {
0N/A }
0N/A
0N/A /**
0N/A * Enqueue an object.
0N/A */
0N/A public synchronized void enqueue(Object obj) {
0N/A
0N/A QueueElement newElt = new QueueElement(obj);
0N/A
0N/A if (head == null) {
0N/A head = newElt;
0N/A tail = newElt;
0N/A length = 1;
0N/A } else {
0N/A newElt.next = head;
0N/A head.prev = newElt;
0N/A head = newElt;
0N/A length++;
0N/A }
0N/A notify();
0N/A }
0N/A
0N/A /**
0N/A * Dequeue the oldest object on the queue. Will wait indefinitely.
0N/A *
0N/A * @return the oldest object on the queue.
0N/A * @exception java.lang.InterruptedException if any thread has
0N/A * interrupted this thread.
0N/A */
0N/A public Object dequeue() throws InterruptedException {
0N/A return dequeue(0L);
0N/A }
0N/A
0N/A /**
0N/A * Dequeue the oldest object on the queue.
0N/A * @param timeOut the number of milliseconds to wait for something
0N/A * to arrive.
0N/A *
0N/A * @return the oldest object on the queue.
0N/A * @exception java.lang.InterruptedException if any thread has
0N/A * interrupted this thread.
0N/A */
0N/A public synchronized Object dequeue(long timeOut)
0N/A throws InterruptedException {
0N/A
0N/A while (tail == null) {
0N/A wait(timeOut);
0N/A }
0N/A QueueElement elt = tail;
0N/A tail = elt.prev;
0N/A if (tail == null) {
0N/A head = null;
0N/A } else {
0N/A tail.next = null;
0N/A }
0N/A length--;
0N/A return elt.obj;
0N/A }
0N/A
0N/A /**
0N/A * Is the queue empty?
0N/A * @return true if the queue is empty.
0N/A */
0N/A public synchronized boolean isEmpty() {
0N/A return (tail == null);
0N/A }
0N/A
0N/A /**
0N/A * Returns an enumeration of the elements in Last-In, First-Out
0N/A * order. Use the Enumeration methods on the returned object to
0N/A * fetch the elements sequentially.
0N/A */
0N/A public final synchronized Enumeration elements() {
0N/A return new LIFOQueueEnumerator(this);
0N/A }
0N/A
0N/A /**
0N/A * Returns an enumeration of the elements in First-In, First-Out
0N/A * order. Use the Enumeration methods on the returned object to
0N/A * fetch the elements sequentially.
0N/A */
0N/A public final synchronized Enumeration reverseElements() {
0N/A return new FIFOQueueEnumerator(this);
0N/A }
0N/A
0N/A public synchronized void dump(String msg) {
0N/A System.err.println(">> "+msg);
0N/A System.err.println("["+length+" elt(s); head = "+
0N/A (head == null ? "null" : (head.obj)+"")+
0N/A " tail = "+(tail == null ? "null" : (tail.obj)+""));
0N/A QueueElement cursor = head;
0N/A QueueElement last = null;
0N/A while (cursor != null) {
0N/A System.err.println(" "+cursor);
0N/A last = cursor;
0N/A cursor = cursor.next;
0N/A }
0N/A if (last != tail) {
0N/A System.err.println(" tail != last: "+tail+", "+last);
0N/A }
0N/A System.err.println("]");
0N/A }
0N/A}
0N/A
0N/Afinal class FIFOQueueEnumerator implements Enumeration {
0N/A Queue queue;
0N/A QueueElement cursor;
0N/A
0N/A FIFOQueueEnumerator(Queue q) {
0N/A queue = q;
0N/A cursor = q.tail;
0N/A }
0N/A
0N/A public boolean hasMoreElements() {
0N/A return (cursor != null);
0N/A }
0N/A
0N/A public Object nextElement() {
0N/A synchronized (queue) {
0N/A if (cursor != null) {
0N/A QueueElement result = cursor;
0N/A cursor = cursor.prev;
0N/A return result.obj;
0N/A }
0N/A }
0N/A throw new NoSuchElementException("FIFOQueueEnumerator");
0N/A }
0N/A}
0N/A
0N/Afinal class LIFOQueueEnumerator implements Enumeration {
0N/A Queue queue;
0N/A QueueElement cursor;
0N/A
0N/A LIFOQueueEnumerator(Queue q) {
0N/A queue = q;
0N/A cursor = q.head;
0N/A }
0N/A
0N/A public boolean hasMoreElements() {
0N/A return (cursor != null);
0N/A }
0N/A
0N/A public Object nextElement() {
0N/A synchronized (queue) {
0N/A if (cursor != null) {
0N/A QueueElement result = cursor;
0N/A cursor = cursor.next;
0N/A return result.obj;
0N/A }
0N/A }
0N/A throw new NoSuchElementException("LIFOQueueEnumerator");
0N/A }
0N/A}
0N/A
0N/Aclass QueueElement {
0N/A QueueElement next = null;
0N/A QueueElement prev = null;
0N/A
0N/A Object obj = null;
0N/A
0N/A QueueElement(Object obj) {
0N/A this.obj = obj;
0N/A }
0N/A
0N/A public String toString() {
0N/A return "QueueElement[obj="+obj+(prev == null ? " null" : " prev")+
0N/A (next == null ? " null" : " next")+"]";
0N/A }
0N/A}