BtpLayer.java

/**
 *  Implementation of ITS Basic Transport Protocol layer 
 * 
 *  @author     ETSI / STF424
 *  @version    $URL$
 *              $Id$
 *
 */
package org.etsi.its.adapter.layers;

import java.util.HashMap;
import java.util.Map;
import java.util.Stack;

import org.etsi.common.ByteHelper;
import org.etsi.its.adapter.IManagementLayers;

/**
 *  Implementation of ITS Basic Transport Protocol layer 
 */
public class BtpLayer extends Layer {

    /**
     * Parameter name for BTP packet type
     */
    public static final String BTP_TYPE = "BtpType";
    
    /**
     * Parameter name for BTP destination port
     */    
    public static final String BTP_DSTPORT = "BtpDstPort";

    /**
     * Parameter name for BTP source port
     */    
    public static final String BTP_SRCPORT = "BtpSrcPort";
    
    /**
     * Parameter name for BTP destination port information
     */    
    public static final String BTP_DSTPORTINFO = "BtpDstPortInfo";
    
    /**
     * BTP packet type A
     */
    public static final int TYPE_A = 0;
    
    /**
     * BTP packet type B
     */    
    public static final int TYPE_B = 1;
    
    /**
     * Constructor
     * @param  management   Layer management instance
     * @param  lowerStack   Lower protocol stack   
     */
    public BtpLayer(IManagementLayers management, Stack<String> lowerStack) {
        super(management, lowerStack);
    }

    /* (non-Javadoc)
     * @see org.etsi.its.adapter.layers.Layer#send(byte[], java.util.Map)
     */
    @Override
    public boolean send(byte[] message, Map<String, Object> params) {
        
        // Destination Port (16 bits)
        int dstPort;
        try {
            dstPort = (Integer)params.get(BTP_DSTPORT);
        }
        catch (NullPointerException e) {
            dstPort = 0;
        }        
        byte[] encapsulated = ByteHelper.intToByteArray(dstPort, 2);
        
        if(params.get(BTP_TYPE).equals(TYPE_A)) {
            // Source Port (16 bits)
            int srcPort;
            try {
                srcPort = (Integer)params.get(BTP_SRCPORT);
            }
            catch (NullPointerException e) {
                srcPort = 0;
            }
            encapsulated = ByteHelper.concat(encapsulated, ByteHelper.intToByteArray(srcPort, 2));
        }
        else {
            // Destination port info (16 bits)
            int dstPortInfo;
            try {
                dstPortInfo = (Integer)params.get(BTP_DSTPORTINFO);
            }
            catch (NullPointerException e) {
                dstPortInfo = 0;
            }
            encapsulated = ByteHelper.concat(encapsulated, ByteHelper.intToByteArray(dstPortInfo, 2));
        }

        // Update params
//        if(lowerLayerName != null && lowerLayerName.equals("GN")) {
//            params.put(GnLayer.GN_NEXTHEADER, "BTP-A"); // TODO Alex to confirm removal
//        }
        
        return super.send(ByteHelper.concat(encapsulated, message), params);        
    }
    
    /* (non-Javadoc)
     * @see org.etsi.its.adapter.layers.Layer#receive(byte[])
     */
    @Override
    public void receive(byte[] message, Map<String, Object> lowerInfo) {
    
        byte[] dstPort = new byte[2];
        System.arraycopy(message, 0, dstPort, 0, 2);
        
        byte[] srcPort = new byte[2];
        System.arraycopy(message, 2, srcPort, 0, 2);
        
        int payloadLength = message.length - 4;
        byte[] payload = new byte[payloadLength];
        System.arraycopy(message, 4, payload, 0, payloadLength);
        
        lowerInfo.put(BTP_DSTPORT, dstPort);
        lowerInfo.put(BTP_DSTPORTINFO, srcPort);
        
        super.receive(payload, lowerInfo);
    }
}