| /* |
| * 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.ode.bpel.runtime; |
| |
| import java.util.HashSet; |
| import java.util.Iterator; |
| import java.util.LinkedList; |
| |
| import org.apache.ode.bpel.runtime.channels.ReadWriteLock; |
| import org.apache.ode.jacob.JacobRunnable; |
| import org.apache.ode.jacob.ReceiveProcess; |
| import org.apache.ode.jacob.Synch; |
| |
| /** |
| * A fair READ-WRITE lock. |
| * |
| * @author Maciej Szefler <mszefler at gmail dot com> |
| * |
| */ |
| public class READWRITELOCK extends JacobRunnable { |
| |
| private static final long serialVersionUID = -7415586067226921615L; |
| |
| private static enum Status { |
| UNLOCKED, READLOCK, WRITELOCK, |
| } |
| |
| private LinkedList<Waiter> _waiters = new LinkedList<Waiter>(); |
| |
| private HashSet<Synch> _owners = new HashSet<Synch>(); |
| |
| private Status _status = Status.UNLOCKED; |
| |
| private ReadWriteLock _self; |
| |
| public READWRITELOCK(ReadWriteLock self) { |
| _self = self; |
| } |
| |
| @Override |
| public void run() { |
| object(new ReceiveProcess() { |
| private static final long serialVersionUID = -8644268413754259515L; |
| }.setChannel(_self).setReceiver(new ReadWriteLock() { |
| public void readLock(Synch s) { |
| switch (_status) { |
| case UNLOCKED: |
| _status = Status.READLOCK; |
| _owners.add(s); |
| s.ret(); |
| break; |
| case READLOCK: |
| _owners.add(s); |
| s.ret(); |
| break; |
| case WRITELOCK: |
| _waiters.add(new Waiter(s, false)); |
| break; |
| } |
| |
| instance(READWRITELOCK.this); |
| } |
| |
| public void writeLock(Synch s) { |
| switch (_status) { |
| case UNLOCKED: |
| _status = Status.WRITELOCK; |
| _owners.add(s); |
| s.ret(); |
| break; |
| case READLOCK: |
| _waiters.add(new Waiter(s, true)); |
| break; |
| case WRITELOCK: |
| _waiters.add(new Waiter(s, false)); |
| break; |
| } |
| |
| instance(READWRITELOCK.this); |
| } |
| |
| public void unlock(Synch s) { |
| |
| _owners.remove(s); |
| if (_owners.isEmpty()) { |
| _status = Status.UNLOCKED; |
| if (!_waiters.isEmpty()) { |
| Waiter w = _waiters.removeFirst(); |
| _owners.add(w.synch); |
| _status = w.write ? Status.WRITELOCK : Status.READLOCK; |
| w.synch.ret(); |
| |
| if (_status == Status.READLOCK) { |
| for (Iterator<Waiter> i = _waiters.iterator(); i.hasNext();) { |
| Waiter w1 = i.next(); |
| if (w1.write) |
| break; |
| _owners.add(w1.synch); |
| w1.synch.ret(); |
| i.remove(); |
| } |
| } |
| } |
| } |
| |
| instance(READWRITELOCK.this); |
| } |
| })); |
| } |
| |
| private static class Waiter { |
| Synch synch; |
| boolean write; |
| |
| Waiter(Synch s, boolean w) { |
| synch = s; |
| write = w; |
| } |
| } |
| } |