| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you 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 org.apache.felix.deploymentadmin; |
| |
| /** |
| * A semaphore, that maintains one single permit. An <code>acquire()</code> blocks until a permit is |
| * available, whilst <code>release()</code> will unblock it. |
| */ |
| public class Semaphore { |
| private boolean m_available; |
| |
| /** |
| * Creates a new semaphore that is available. |
| */ |
| public Semaphore() { |
| m_available = true; |
| } |
| |
| /** |
| * Creates a new semaphore and allows you to specify if it's available or not. |
| * |
| * @param isAvailable should the semaphore be available or not |
| */ |
| public Semaphore(boolean isAvailable) { |
| m_available = isAvailable; |
| } |
| |
| /** |
| * Acquires the semaphore, or blocks until it's available or the thread is interrupted. |
| * |
| * @throws InterruptedException when the thread is interrupted |
| */ |
| public void acquire() throws InterruptedException { |
| if (Thread.interrupted()) { |
| throw new InterruptedException(); |
| } |
| synchronized (this) { |
| try { |
| if (!m_available) { |
| wait(); |
| } |
| m_available = false; |
| } |
| catch (InterruptedException ie) { |
| notify(); |
| throw ie; |
| } |
| } |
| } |
| |
| /** |
| * Tries to acquire the semaphore and waits for the duration of the specified timeout |
| * until it becomes available. |
| * |
| * @param timeout the number of milliseconds to wait |
| * @return <code>true</code> if the semaphore was acquired, <code>false</code> if it was |
| * not after waiting for the specified amount of time |
| * @throws InterruptedException when the thread is interrupted |
| */ |
| public boolean tryAcquire(long timeout) throws InterruptedException { |
| if (Thread.interrupted()) { |
| throw new InterruptedException(); |
| } |
| synchronized (this) { |
| if (m_available) { |
| m_available = false; |
| return true; |
| } |
| else if (timeout <= 0) { |
| return false; |
| } |
| else { |
| long startTime = System.currentTimeMillis(); |
| try { |
| while (true) { |
| wait(timeout); |
| if (m_available) { |
| m_available = false; |
| return true; |
| } |
| else { |
| timeout -= (System.currentTimeMillis() - startTime); |
| if (timeout <= 0) { |
| return false; |
| } |
| } |
| } |
| } |
| catch (InterruptedException ie) { |
| notify(); |
| throw ie; |
| } |
| } |
| } |
| } |
| |
| /** |
| * Releases the semaphore. If threads were waiting, one of them is |
| * notified. |
| */ |
| public synchronized void release() { |
| m_available = true; |
| notify(); |
| } |
| } |