/**
*    Copyright 2011, Big Switch Networks, Inc. 
*    Originally created by David Erickson & Rob Sherwood, Stanford University
* 
*    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.
**/

package org.openflow.vendor.nicira;

import org.jboss.netty.buffer.ChannelBuffer;
import org.openflow.protocol.vendor.OFVendorData;

/**
 * Base class for vendor data corresponding to a Nicira vendor extension.
 * Nicira vendor data always starts with a 4-byte integer data type value.
 * 
 * @author Rob Vaterlaus (rob.vaterlaus@bigswitch.com)
 */
public class OFNiciraVendorData implements OFVendorData {

    public static final int NX_VENDOR_ID = 0x00002320;
    /**
     * The value of the integer data type at the beginning of the vendor data
     */
    protected int dataType;
    
    /**
     * Construct empty (i.e. unspecified data type) Nicira vendor data.
     */
    public OFNiciraVendorData() {
    }
    
    /**
     * Contruct Nicira vendor data with the specified data type
     * @param dataType the data type value at the beginning of the vendor data.
     */
    public OFNiciraVendorData(int dataType) {
        this.dataType = dataType;
    }
    
    /**
     * Get the data type value at the beginning of the vendor data
     * @return the integer data type value
     */
    public int getDataType() {
        return dataType;
    }
    
    /**
     * Set the data type value
     * @param dataType the integer data type value at the beginning of the
     *     vendor data.
     */
    public void setDataType(int dataType) {
        this.dataType = dataType;
    }
    
    /**
     * Get the length of the vendor data. This implementation will normally
     * be the superclass for another class that will override this to return
     * the overall vendor data length. This implementation just returns the 
     * length of the part that includes the 4-byte integer data type value
     * at the beginning of the vendor data.
     */
    @Override
    public int getLength() {
        return 4;
    }

    /**
     * Read the vendor data from the ChannelBuffer
     * @param data the channel buffer from which we're deserializing
     * @param length the length to the end of the enclosing message
     */
    @Override
    public void readFrom(ChannelBuffer data, int length) {
        dataType = data.readInt();
    }

    /**
     * Write the vendor data to the ChannelBuffer
     * @param data the channel buffer to which we're serializing
     */
    @Override
    public void writeTo(ChannelBuffer data) {
        data.writeInt(dataType);
    }
}