StreamResultMessage.java

/* Copyright (c) 2006-2009 Jan S. Rellermeyer
 * Systems Group,
 * Department of Computer Science, ETH Zurich.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *    - Redistributions of source code must retain the above copyright notice,
 *      this list of conditions and the following disclaimer.
 *    - Redistributions in binary form must reproduce the above copyright
 *      notice, this list of conditions and the following disclaimer in the
 *      documentation and/or other materials provided with the distribution.
 *    - Neither the name of ETH Zurich nor the names of its contributors may be
 *      used to endorse or promote products derived from this software without
 *      specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */
package ch.ethz.iks.r_osgi.messages;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;

/**
 * Stream result message.
 * 
 * @author Michael Duller, ETH Zurich.
 */
public final class StreamResultMessage extends RemoteOSGiMessage {

	/**
	 * result indicates array.
	 */
	public static final short RESULT_ARRAY = -2;

	/**
	 * result indicates exception.
	 */
	public static final short RESULT_EXCEPTION = -3;

	/**
	 * result indicates write operation completed successfully.
	 */
	public static final short RESULT_WRITE_OK = -4;

	/**
	 * result of the operation.
	 */
	private short result;

	/**
	 * array containing read data.
	 */
	private byte[] b;

	/**
	 * length of b.
	 */
	private int len;

	/**
	 * the exception.
	 */
	private IOException exception;

	/**
	 * creates a new StreamResultMessage.
	 */
	public StreamResultMessage() {
		super(STREAM_RESULT);
	}

	/**
	 * creates a new StreamResultMessage from network packet:
	 * 
	 * <pre>
	 *       0                   1                   2                   3
	 *       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	 *      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	 *      |    R-OSGi header (function = StreamResultMsg = 11)            |
	 *      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	 *      |            result             | result == -2: len, -3: excep. \
	 *      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	 *      | result == -2 && len > 0: b                                    |
	 *      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	 * </pre>
	 * 
	 * .
	 * 
	 * @param input
	 *            an <code>ObjectInputStream</code> that provides the body of a
	 *            R-OSGi network packet.
	 * @throws IOException
	 *             in case of IO failures.
	 * @throws ClassNotFoundException
	 */
	StreamResultMessage(final ObjectInputStream input) throws IOException,
			ClassNotFoundException {
		super(STREAM_RESULT);
		result = input.readShort();
		switch (result) {
		case RESULT_ARRAY:
			len = input.readInt();
			if (len > 0) {
				b = new byte[len];
				int rem = len;
				int read;
				while ((rem > 0)
						&& ((read = input.read(b, len - rem, rem)) > 0)) {
					rem = rem - read;
				}
				if (rem > 0) {
					throw new IOException("Premature end of input stream."); //$NON-NLS-1$
				}
			}
			break;
		case RESULT_EXCEPTION:
			exception = (IOException) input.readObject();
			break;
		case RESULT_WRITE_OK:
			break;
		default:
			if ((result < -1) || (result > 255)) { // -1 indicates EOF -> valid
				throw new IllegalArgumentException(
						"result not within valid range: " + result); //$NON-NLS-1$
			}
			break;
		}
	}

	/**
	 * write the body of the message to a stream.
	 * 
	 * @param out
	 *            the ObjectOutputStream.
	 * @throws IOException
	 *             in case of IO failures.
	 */
	public void writeBody(final ObjectOutputStream out) throws IOException {
		out.writeShort(result);
		if (result == RESULT_ARRAY) {
			out.writeInt(len);
			if (len > 0) {
				out.write(b, 0, len);
			}
		} else if (result == RESULT_EXCEPTION) {
			out.writeObject(exception);
		}
	}

	/**
	 * did the stream operation cause an exception ?
	 * 
	 * @return <code>true</code>, if an exception has been thrown on the remote
	 *         side. In this case, the exception can be retrieved through the
	 *         <code>getException</code> method.
	 */
	public boolean causedException() {
		return (result == RESULT_EXCEPTION);
	}

	/**
	 * get the result value.
	 * 
	 * @return the return value of the invoked operation.
	 */
	public short getResult() {
		return result;
	}

	/**
	 * set the result value.
	 * 
	 * @param result
	 *            the result.
	 */
	public void setResult(final short result) {
		this.result = result;
	}

	/**
	 * get the data array.
	 * 
	 * @return the array containing the read data.
	 */
	public byte[] getData() {
		return b;
	}

	/**
	 * set the data array.
	 * 
	 * @param b
	 *            the array containing the read data.
	 */
	public void setData(final byte[] b) {
		this.b = b;
	}

	/**
	 * get the length.
	 * 
	 * @return the number of bytes read.
	 */
	public int getLen() {
		return len;
	}

	/**
	 * set the length.
	 * 
	 * @param len
	 *            the number of bytes read.
	 */
	public void setLen(final int len) {
		this.len = len;
	}

	/**
	 * get the exception.
	 * 
	 * @return the exception or <code>null</code> if none was thrown.
	 */
	public IOException getException() {
		return exception;
	}

	/**
	 * set the exception.
	 * 
	 * @param exception
	 *            the exception that was thrown.
	 */
	public void setException(final IOException exception) {
		this.exception = exception;
	}

	/**
	 * String representation for debug outputs.
	 * 
	 * @return a string representation.
	 * @see java.lang.Object#toString()
	 */
	public String toString() {
		final StringBuffer buffer = new StringBuffer();
		buffer.append("[STREAM_RESULT] - XID: "); //$NON-NLS-1$
		buffer.append(xid);
		buffer.append(", result: "); //$NON-NLS-1$
		buffer.append(result);
		if (causedException()) {
			buffer.append(", exception: "); //$NON-NLS-1$
			buffer.append(exception.getMessage());
		}
		return buffer.toString();
	}

}