PL132LData.java

/*
 * #%L
 * OW2 Chameleon - Fuchsia Framework
 * %%
 * Copyright (C) 2009 - 2014 OW2 Chameleon
 * %%
 * 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.
 * #L%
 */
/*
    Calimero - A library for KNX network access
    Copyright (C) 2006-2008 B. Malinowsky

    This program is free software; you can redistribute it and/or 
    modify it under the terms of the GNU General Public License 
    as published by the Free Software Foundation; either version 2 
    of the License, or at your option any later version. 
 
    This program is distributed in the hope that it will be useful, 
    but WITHOUT ANY WARRANTY; without even the implied warranty of 
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the 
    GNU General Public License for more details. 
 
    You should have received a copy of the GNU General Public License 
    along with this program; if not, write to the Free Software 
    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA. 
 
    Linking this library statically or dynamically with other modules is 
    making a combined work based on this library. Thus, the terms and 
    conditions of the GNU General Public License cover the whole 
    combination. 
 
    As a special exception, the copyright holders of this library give you 
    permission to link this library with independent modules to produce an 
    executable, regardless of the license terms of these independent 
    modules, and to copy and distribute the resulting executable under terms 
    of your choice, provided that you also meet, for each linked independent 
    module, the terms and conditions of the license of that module. An 
    independent module is a module which is not derived from or based on 
    this library. If you modify this library, you may extend this exception 
    to your version of the library, but you are not obligated to do so. If 
    you do not wish to do so, delete this exception statement from your 
    version. 
*/

package tuwien.auto.calimero.link.medium;

import java.io.ByteArrayInputStream;

import tuwien.auto.calimero.DataUnitBuilder;
import tuwien.auto.calimero.IndividualAddress;
import tuwien.auto.calimero.Priority;
import tuwien.auto.calimero.exception.KNXFormatException;

/**
 * L-data frame format on PL132 communication medium.
 * <p>
 * Supports standard and extended frame format.
 * 
 * @author B. Malinowsky
 */
public class PL132LData extends RawFrameBase
{
	private static final int MIN_LENGTH = 9;

	private final byte[] doa;
	private final boolean ack;
	
	/**
	 * Creates a new L-data frame out of a byte array.
	 * <p>
	 * 
	 * @param data byte array containing the L-data frame
	 * @param offset start offset of frame structure in <code>data</code>, offset >=
	 *        0
	 * @throws KNXFormatException if length of data too short for frame, on no valid frame
	 *         structure
	 */
	public PL132LData(byte[] data, int offset) throws KNXFormatException
	{
		final ByteArrayInputStream is =
			new ByteArrayInputStream(data, offset, data.length - offset);
		final int avail = is.available();
		if (avail < MIN_LENGTH)
			throw new KNXFormatException("data too short for L-data frame", avail);
		doa = new byte[2];
		is.read(doa, 0, 2);
		final int ctrl = is.read();
		// parse control field and check if valid
		if ((ctrl & 0xC) != 0xC)
			throw new KNXFormatException("invalid control field", ctrl);
		type = LDATA_FRAME;
		ext = (ctrl & 0x80) == 0;
		repetition = (ctrl & 0x40) == 0;
		p = Priority.get(ctrl & 0x3);
		final boolean group = (ctrl & 0x20) == 0x20;
		ack = (ctrl & 0x10) == 0x10;
		// check fourth byte for extended control field
		final int ctrle = ext ? readCtrlEx(is) : 0;
		src = new IndividualAddress((is.read() << 8) | is.read());
		setDestination((is.read() << 8) | is.read(), group);

		final int npci = is.read();
		final int len;
		if (ext) {
			hopcount = (ctrle & 0x70) >> 4;
			len = npci;
			if (len > 64)
				throw new KNXFormatException("APDU length exceeds maximum of 64 bytes",
					len);
		}
		else {
			hopcount = (npci & 0x70) >> 4;
			len = npci & 0x0f;
		}
		tpdu = new byte[len + 1];
		if (is.read(tpdu, 0, tpdu.length) != tpdu.length)
			throw new KNXFormatException("data too short for L-data TPDU");
		fcs = is.read() << 8 | is.read();
	}

	/**
	 * Returns the domain address of this frame.
	 * <p>
	 * The address is returned in network byte order.
	 * 
	 * @return domain address as byte array of length 2
	 */
	public final byte[] getDomainAddress()
	{
		return (byte[]) doa.clone();
	}

	/**
	 * Returns whether layer 2 acknowledge is requested or not.
	 * <p>
	 * 
	 * @return <code>true</code> if L2-ACK requested, <code>false</code> otherwise
	 */
	public final boolean isAckRequested()
	{
		return ack;
	}

	/* (non-Javadoc)
	 * @see tuwien.auto.calimero.link.medium.RawFrameBase#toString()
	 */
	public String toString()
	{
		final int domain = (doa[0] & 0xff) << 8 | (doa[1] & 0xff);
		return super.toString() + " hop count " + hopcount + " domain " + domain
			+ ", tpdu " + DataUnitBuilder.toHex(tpdu, " ");
	}
}