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/*
* JBoss, Home of Professional Open Source.
*
* Copyright 2012 Red Hat, Inc. and/or its affiliates, and individual
* contributors as indicated by the @author tags.
*
* 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.xnio.channels;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
import org.xnio.ChannelListener;
import org.xnio.ChannelListeners;
import org.xnio.Option;
import org.xnio.XnioExecutor;
import org.xnio.XnioIoThread;
import org.xnio.XnioWorker;
import static org.xnio.Bits.allAreClear;
import static org.xnio.Bits.allAreSet;
import static org.xnio.Bits.anyAreSet;
/**
* A stream source channel which is always empty.
*
* @author David M. Lloyd
*/
public class EmptyStreamSourceChannel implements StreamSourceChannel, ReadListenerSettable, CloseListenerSettable {
private final XnioIoThread thread;
private final Runnable readRunnable = new Runnable() {
public void run() {
ChannelListener listener = readListener;
if (listener == null) {
suspendReads();
return;
}
ChannelListeners.invokeChannelListener(EmptyStreamSourceChannel.this, listener);
final int oldVal = state;
if (allAreSet(oldVal, RESUMED) && allAreClear(oldVal, EMPTIED | CLOSED)) {
thread.execute(this);
}
}
};
@SuppressWarnings("unused")
private volatile int state;
private ChannelListener readListener;
private ChannelListener closeListener;
private static final int CLOSED = 1 << 0;
private static final int EMPTIED = 1 << 1;
private static final int RESUMED = 1 << 2;
private static final AtomicIntegerFieldUpdater stateUpdater = AtomicIntegerFieldUpdater.newUpdater(EmptyStreamSourceChannel.class, "state");
/**
* Construct a new instance.
*
* @param thread the XNIO read thread to use
*/
public EmptyStreamSourceChannel(final XnioIoThread thread) {
this.thread = thread;
}
public long transferTo(final long position, final long count, final FileChannel target) throws IOException {
return 0;
}
public long transferTo(final long count, final ByteBuffer throughBuffer, final StreamSinkChannel target) throws IOException {
throughBuffer.limit(0);
emptied();
return -1;
}
public void setReadListener(final ChannelListener readListener) {
this.readListener = readListener;
}
public ChannelListener getReadListener() {
return readListener;
}
public void setCloseListener(final ChannelListener closeListener) {
this.closeListener = closeListener;
}
public ChannelListener getCloseListener() {
return closeListener;
}
public ChannelListener.Setter getReadSetter() {
return new ReadListenerSettable.Setter(this);
}
public ChannelListener.Setter getCloseSetter() {
return new CloseListenerSettable.Setter(this);
}
private void emptied() {
int oldVal, newVal;
do {
oldVal = state;
if (allAreSet(oldVal, EMPTIED)) {
return;
}
newVal = oldVal | EMPTIED;
} while (! stateUpdater.compareAndSet(this, oldVal, newVal));
}
public long read(final ByteBuffer[] dsts, final int offset, final int length) throws IOException {
emptied();
return -1;
}
public long read(final ByteBuffer[] dsts) throws IOException {
emptied();
return -1;
}
public int read(final ByteBuffer dst) throws IOException {
emptied();
return -1;
}
public void suspendReads() {
int oldVal, newVal;
do {
oldVal = state;
if (allAreClear(oldVal, RESUMED)) {
return;
}
newVal = oldVal & ~RESUMED;
} while (! stateUpdater.compareAndSet(this, oldVal, newVal));
}
public void resumeReads() {
int oldVal, newVal;
do {
oldVal = state;
if (anyAreSet(oldVal, RESUMED | CLOSED)) {
return;
}
newVal = RESUMED;
} while (! stateUpdater.compareAndSet(this, oldVal, newVal));
if (allAreClear(oldVal, EMPTIED)) {
thread.execute(readRunnable);
}
}
public boolean isReadResumed() {
return allAreSet(state, RESUMED);
}
public void wakeupReads() {
int oldVal, newVal;
do {
oldVal = state;
if (anyAreSet(oldVal, CLOSED)) {
return;
}
newVal = RESUMED;
} while (! stateUpdater.compareAndSet(this, oldVal, newVal));
thread.execute(readRunnable);
}
public void shutdownReads() throws IOException {
final int oldVal = stateUpdater.getAndSet(this, EMPTIED | CLOSED);
if (allAreClear(oldVal, CLOSED)) {
thread.execute(ChannelListeners.getChannelListenerTask(this, closeListener));
}
}
public void awaitReadable() throws IOException {
// return immediately
}
public void awaitReadable(final long time, final TimeUnit timeUnit) throws IOException {
// return immediately
}
@Deprecated
public XnioExecutor getReadThread() {
return thread;
}
public XnioIoThread getIoThread() {
return thread;
}
public XnioWorker getWorker() {
return thread.getWorker();
}
public boolean isOpen() {
return allAreClear(state, CLOSED);
}
public void close() throws IOException {
final int oldVal = stateUpdater.getAndSet(this, EMPTIED | CLOSED);
if (allAreClear(oldVal, CLOSED)) {
thread.execute(ChannelListeners.getChannelListenerTask(this, closeListener));
}
}
public boolean supportsOption(final Option option) {
return false;
}
public T getOption(final Option option) throws IOException {
return null;
}
public T setOption(final Option option, final T value) throws IllegalArgumentException, IOException {
return null;
}
}
