| /* |
| * The Apache Software License, Version 1.1 |
| * |
| * |
| * Copyright (c) 2003 The Apache Software Foundation. All rights |
| * reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * |
| * 1. Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * |
| * 2. Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in |
| * the documentation and/or other materials provided with the |
| * distribution. |
| * |
| * 3. The end-user documentation included with the redistribution, |
| * if any, must include the following acknowledgment: |
| * "This product includes software developed by the |
| * Apache Software Foundation (http://www.apache.org/)." |
| * Alternately, this acknowledgment may appear in the software itself, |
| * if and wherever such third-party acknowledgments normally appear. |
| * |
| * 4. The names "Apache" and "Apache Software Foundation" must |
| * not be used to endorse or promote products derived from this |
| * software without prior written permission. For written |
| * permission, please contact apache@apache.org. |
| * |
| * 5. Products derived from this software may not be called "Apache |
| * XMLBeans", nor may "Apache" appear in their name, without prior |
| * written permission of the Apache Software Foundation. |
| * |
| * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED |
| * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
| * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE |
| * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR |
| * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF |
| * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND |
| * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, |
| * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT |
| * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| * SUCH DAMAGE. |
| * ==================================================================== |
| * |
| * This software consists of voluntary contributions made by many |
| * individuals on behalf of the Apache Software Foundation and was |
| * originally based on software copyright (c) 2000-2003 BEA Systems |
| * Inc., <http://www.bea.com/>. For more information on the Apache Software |
| * Foundation, please see <http://www.apache.org/>. |
| */ |
| |
| package org.apache.xmlbeans.impl.common; |
| |
| public class Mutex |
| { |
| private Thread owner = null; // Owner of mutex, null if nobody |
| private int lock_count = 0; |
| |
| /** |
| * Acquire the mutex. The mutex can be acquired multiple times |
| * by the same thread, provided that it is released as many |
| * times as it is acquired. The calling thread blocks until |
| * it has acquired the mutex. (There is no timeout). |
| */ |
| public synchronized void acquire() throws InterruptedException |
| { |
| while (tryToAcquire() == false) |
| { |
| this.wait(); |
| } |
| } |
| |
| /** |
| * Attempts to acquire the mutex. Returns false (and does not |
| * block) if it can't get it. |
| */ |
| |
| public synchronized boolean tryToAcquire() |
| { |
| // Try to get the mutex. Return true if you got it. |
| |
| if( owner == null ) |
| { |
| owner = Thread.currentThread(); |
| lock_count = 1; |
| return true; |
| } |
| |
| if( owner == Thread.currentThread() ) |
| { |
| ++lock_count; |
| return true; |
| } |
| |
| return false; |
| } |
| |
| /** |
| * Release the mutex. The mutex has to be released as many times |
| * as it was acquired to actually unlock the resource. The mutex |
| * must be released by the thread that acquired it |
| * |
| * @throws IllegalStateException (a RuntimeException) if a thread |
| * other than the current owner tries to release the mutex. |
| */ |
| |
| public synchronized void release() |
| { |
| if (owner != Thread.currentThread()) |
| throw new IllegalStateException("Thread calling release() doesn't own mutex"); |
| |
| if (--lock_count <= 0) |
| { |
| owner = null; |
| notify(); |
| } |
| } |
| } |
| |