/**
*
* Copyright 2004 Hiram Chirino
*
* Licensed 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.activeio.filter;
import java.io.IOException;
import java.io.InterruptedIOException;
import org.activeio.FilterSynchChannel;
import org.activeio.Packet;
import org.activeio.SynchChannel;
import org.activeio.SynchChannelServer;
import EDU.oswego.cs.dl.util.concurrent.Mutex;
import EDU.oswego.cs.dl.util.concurrent.Sync;
/**
* Used to synchronize concurrent access to a SynchChannel.
*
* Uses two different {@see EDU.oswego.cs.dl.util.concurrent.Sync} objects
* for write and read operations. All other operations such as {@see #stop(long)}
* and {@see #stop} just do a normal java synchronization against the SynchornizedSynchChannel
* object instance.
*
*/
public class SynchornizedSynchChannel extends FilterSynchChannel {
private final Sync readLock;
private final Sync writeLock;
public SynchornizedSynchChannel(SynchChannel next) {
this(next, new Mutex(), new Mutex());
}
public SynchornizedSynchChannel(SynchChannel next, Sync readLock, Sync writeLock) {
super(next);
this.readLock = readLock;
this.writeLock = writeLock;
}
public Packet read(long timeout) throws IOException {
try {
if( timeout==SynchChannelServer.WAIT_FOREVER_TIMEOUT ) {
readLock.acquire();
} else {
long start = System.currentTimeMillis();
if( !readLock.attempt(0) ) {
return null;
}
// Adjust the resulting timeout down to account for time taken to
// get the readLock.
timeout = Math.max(0, timeout-(System.currentTimeMillis()-start));
}
} catch (InterruptedException e) {
throw new InterruptedIOException(e.getMessage());
}
try {
return getNext().read(timeout);
} finally {
readLock.release();
}
}
public void write(Packet packet) throws IOException {
try {
writeLock.acquire();
} catch (InterruptedException e) {
throw new InterruptedIOException(e.getMessage());
}
try {
getNext().write(packet);
} finally {
writeLock.release();
}
}
public void flush() throws IOException {
try {
writeLock.acquire();
} catch (InterruptedException e) {
throw new InterruptedIOException(e.getMessage());
}
try {
getNext().flush();
} finally {
writeLock.release();
}
}
synchronized public void dispose() {
super.dispose();
}
synchronized public Object narrow(Class target) {
return super.narrow(target);
}
synchronized public void start() throws IOException {
super.start();
}
synchronized public void stop(long timeout) throws IOException {
super.stop(timeout);
}
public Sync getReadLock() {
return readLock;
}
public Sync getWriteLock() {
return writeLock;
}
}