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Artifact with commonly used I/O functionality and for connection related issues such as receiving or transmitting data in a unified way.
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// /////////////////////////////////////////////////////////////////////////////
// REFCODES.ORG
// =============================================================================
// This code is copyright (c) by Siegfried Steiner, Munich, Germany and licensed
// under the following (see "http://en.wikipedia.org/wiki/Multi-licensing")
// licenses:
// =============================================================================
// GNU General Public License, v3.0 ("http://www.gnu.org/licenses/gpl-3.0.html")
// together with the GPL linking exception applied; as being applied by the GNU
// Classpath ("http://www.gnu.org/software/classpath/license.html")
// =============================================================================
// Apache License, v2.0 ("http://www.apache.org/licenses/LICENSE-2.0")
// =============================================================================
// Please contact the copyright holding author(s) of the software artifacts in
// question for licensing issues not being covered by the above listed licenses,
// also regarding commercial licensing models or regarding the compatibility
// with other open source licenses.
// /////////////////////////////////////////////////////////////////////////////

package org.refcodes.io.impls;

import java.io.IOException;
import java.io.ObjectOutputStream;
import java.io.OutputStream;
import java.io.PipedInputStream;
import java.io.PipedOutputStream;
import java.io.Serializable;

import org.refcodes.component.CloseException;
import org.refcodes.component.ConnectionStatus;
import org.refcodes.component.OpenException;
import org.refcodes.io.OutputStreamConnectionByteSender;
import org.refcodes.io.OutputStreamConnectionSender;

/**
 * Implementation of the {@link OutputStreamConnectionSender} interface.
 */
public class OutputStreamConnectionByteSenderImpl extends AbstractByteSender implements OutputStreamConnectionByteSender {

	// /////////////////////////////////////////////////////////////////////////
	// CONSTANTS:
	// /////////////////////////////////////////////////////////////////////////

	// /////////////////////////////////////////////////////////////////////////
	// VARIABLES:
	// /////////////////////////////////////////////////////////////////////////

	private OutputStream _outputStream = null;

	// /////////////////////////////////////////////////////////////////////////
	// CONSTRUCTORS:
	// /////////////////////////////////////////////////////////////////////////

	// /////////////////////////////////////////////////////////////////////////
	// METHODS:
	// /////////////////////////////////////////////////////////////////////////

	/**
	 * {@inheritDoc} -----------------------------------------------------------
	 * -------------- HINT: For testing purposes you can pass an already flushed
	 * {@link ObjectOutputStream} (via {@link ObjectOutputStream#flush()})
	 * encapsulating a {@link PipedOutputStream} which in turn encapsulates a
	 * {@link PipedInputStream} to this {@link #open(OutputStream)} method. This
	 * enables you a non-blocking test of the
	 * {@link OutputStreamConnectionByteSenderImpl} connected with the
	 * {@link PrefetchInputStreamConnectionReceiverImpl} counterpart which is being
	 * opened with the {@link PipedInputStream}.
	 * -------------------------------------------------------------------------
	 * ATTENTION: For maintainers, please keep the below code in sync with the
	 * code from
	 * {@link PrefetchBidirectionalStreamConnectionTransceiverImpl#open(java.io.OutputStream)}
	 * .
	 */
	@Override
	public synchronized void open( OutputStream aOutputStream ) throws OpenException {
		if ( isOpened() ) { throw new OpenException( "Unable to open the connection is is is ALREADY OPEN; connection status is " + getConnectionStatus() + "." ); }
		try {
			_outputStream = aOutputStream;
			_outputStream.flush();
		}
		catch ( IOException aException ) {
			throw new OpenException( "Unable to open the I/O stream receiver as of a causing exception.", aException );
		}
		setConnectionStatus( ConnectionStatus.OPENED );
	}

	@Override
	public boolean isOpenable( OutputStream aOutputStream ) {
		if ( aOutputStream == null ) { return false; }
		return !isOpened();
	}

	@Override
	public void flush() throws OpenException {
		try {
			_outputStream.flush();
		}
		catch ( IOException e ) {
			throw new OpenException( "Unable to flush underlying output stream <" + _outputStream + ">.", e );
		}
	}

	@Override
	public synchronized void close() throws CloseException {
		super.close();
		try {
			_outputStream.close();
		}
		catch ( IOException aException ) {}
	}

	/**
	 * {@inheritDoc} -----------------------------------------------------------
	 * -------------- ATTENTION: For maintainers, please keep the below code in
	 * sync with the code from
	 * {@link PrefetchBidirectionalStreamConnectionTransceiverImpl#writeDatagram(Serializable)}
	 * .
	 */
	@Override
	public void writeDatagram( byte aDatagram ) throws OpenException {
		if ( !isOpened() ) { throw new OpenException( "Unable to write datagram <" + aDatagram + "> as the connection is NOT OPEN; connection status is " + getConnectionStatus() + "." ); }
		synchronized ( _outputStream ) {
			try {
				_outputStream.write( aDatagram );
				_outputStream.flush();
			}
			catch ( IOException aException ) {
				if ( isClosed() ) {
					return;
				}
				else {
					try {
						close();
					}
					catch ( CloseException e ) {
						throw new OpenException( "Unable to close malfunctioning connection.", e );
					}
				}
				throw new OpenException( aException );
			}
		}
	}

	// /////////////////////////////////////////////////////////////////////////
	// HOOKS:
	// /////////////////////////////////////////////////////////////////////////

	// /////////////////////////////////////////////////////////////////////////
	// HELPER:
	// /////////////////////////////////////////////////////////////////////////

}