//
// ========================================================================
// Copyright (c) 1995-2014 Mort Bay Consulting Pty. Ltd.
// ------------------------------------------------------------------------
// All rights reserved. This program and the accompanying materials
// are made available under the terms of the Eclipse Public License v1.0
// and Apache License v2.0 which accompanies this distribution.
//
// The Eclipse Public License is available at
// http://www.eclipse.org/legal/epl-v10.html
//
// The Apache License v2.0 is available at
// http://www.opensource.org/licenses/apache2.0.php
//
// You may elect to redistribute this code under either of these licenses.
// ========================================================================
//
package com.facebook.presto.jdbc.internal.jetty.io;
import java.io.IOException;
import java.nio.channels.ClosedChannelException;
import java.nio.channels.ReadPendingException;
import java.util.concurrent.atomic.AtomicReference;
import com.facebook.presto.jdbc.internal.jetty.util.Callback;
import com.facebook.presto.jdbc.internal.jetty.util.log.Log;
import com.facebook.presto.jdbc.internal.jetty.util.log.Logger;
/* ------------------------------------------------------------ */
/**
* A Utility class to help implement {@link EndPoint#fillInterested(Callback)}
* by keeping state and calling the context and callback objects.
*
*/
public abstract class FillInterest
{
private final static Logger LOG = Log.getLogger(FillInterest.class);
private final AtomicReference<Callback> _interested = new AtomicReference<>(null);
/* ------------------------------------------------------------ */
protected FillInterest()
{
}
/* ------------------------------------------------------------ */
/** Call to register interest in a callback when a read is possible.
* The callback will be called either immediately if {@link #needsFill()}
* returns true or eventually once {@link #fillable()} is called.
* @param callback
* @throws ReadPendingException
*/
public <C> void register(Callback callback) throws ReadPendingException
{
if (callback==null)
throw new IllegalArgumentException();
if (!_interested.compareAndSet(null,callback))
{
LOG.warn("Read pending for "+_interested.get()+" pervented "+callback);
throw new ReadPendingException();
}
try
{
if (needsFill())
fillable();
}
catch(IOException e)
{
onFail(e);
}
}
/* ------------------------------------------------------------ */
/** Call to signal that a read is now possible.
*/
public void fillable()
{
Callback callback=_interested.get();
if (callback!=null && _interested.compareAndSet(callback,null))
callback.succeeded();
}
/* ------------------------------------------------------------ */
/**
* @return True if a read callback has been registered
*/
public boolean isInterested()
{
return _interested.get()!=null;
}
/* ------------------------------------------------------------ */
/** Call to signal a failure to a registered interest
*/
public void onFail(Throwable cause)
{
Callback callback=_interested.get();
if (callback!=null && _interested.compareAndSet(callback,null))
callback.failed(cause);
}
/* ------------------------------------------------------------ */
public void onClose()
{
Callback callback=_interested.get();
if (callback!=null && _interested.compareAndSet(callback,null))
callback.failed(new ClosedChannelException());
}
/* ------------------------------------------------------------ */
@Override
public String toString()
{
return String.format("FillInterest@%x{%b,%s}",hashCode(),_interested.get(),_interested.get());
}
/* ------------------------------------------------------------ */
/** Register the read interest
* Abstract method to be implemented by the Specific ReadInterest to
* enquire if a read is immediately possible and if not to schedule a future
* call to {@link #fillable()} or {@link #onFail(Throwable)}
* @return true if a read is possible
* @throws IOException
*/
abstract protected boolean needsFill() throws IOException;
}