| /******************************************************************************* |
| * Copyright (c) 2008, 2016 IBM Corporation and others |
| * All rights reserved. This program and the accompanying materials are made |
| * available under the terms of the Eclipse Public License v1.0 which |
| * accompanies this distribution, and is available at |
| * http://www.eclipse.org/legal/epl-v10.html |
| ******************************************************************************/ |
| package org.eclipse.osgi.internal.log; |
| |
| import java.util.ArrayList; |
| import java.util.List; |
| |
| public class BasicReadWriteLock { |
| private List<Thread> currentReaders = new ArrayList<>(2); |
| private int writersWaiting = 0; |
| private Thread writing = null; |
| |
| public synchronized int readLock() { |
| while (writing != null || writersWaiting != 0) { |
| try { |
| if (writing == Thread.currentThread()) |
| throw new IllegalStateException("Attempted to nest read lock inside a write lock"); //$NON-NLS-1$ |
| wait(); |
| } catch (InterruptedException e) { |
| // reset interrupted state but keep waiting |
| Thread.currentThread().interrupt(); |
| } |
| } |
| currentReaders.add(Thread.currentThread()); |
| if (currentReaders.size() == 1) |
| return 1; |
| Thread current = Thread.currentThread(); |
| int result = 0; |
| for (Thread reader : currentReaders) { |
| if (reader == current) |
| result++; |
| } |
| return result; |
| } |
| |
| public synchronized void readUnlock() { |
| currentReaders.remove(Thread.currentThread()); |
| notifyAll(); |
| } |
| |
| public synchronized void writeLock() { |
| writersWaiting++; |
| try { |
| while (writing != null || currentReaders.size() != 0) { |
| try { |
| if (writing == Thread.currentThread() || currentReaders.contains(Thread.currentThread())) |
| throw new IllegalStateException("Attempted to nest write lock inside a read or write lock"); //$NON-NLS-1$ |
| wait(); |
| } catch (InterruptedException e) { |
| // reset interrupted state but keep waiting |
| Thread.currentThread().interrupt(); |
| } |
| } |
| } finally { |
| writersWaiting--; |
| } |
| writing = Thread.currentThread(); |
| } |
| |
| public synchronized void writeUnlock() { |
| writing = null; |
| notifyAll(); |
| } |
| } |