XorOnlyAttribute.java

/*
 * 
 * Code derived and adapted from the Jitsi client side STUN framework.
 * 
 * Distributable under LGPL license.
 * See terms of license at gnu.org.
 */

package org.restcomm.media.stun.messages.attributes.general;

import org.restcomm.media.stun.StunException;
import org.restcomm.media.stun.messages.attributes.StunAttribute;

/**
 * This attribute is present in a Binding Request. It is used by a client to
 * request that a server compliant to this specification omit the MAPPED-ADDRESS
 * from a Binding Response, and include only the XOR- MAPPED-ADDRESS. This is
 * necessary in cases where a Binding Response is failing integrity checks
 * because a NAT is rewriting the contents of a MAPPED-ADDRESS in the Binding
 * Response.
 * 
 * This attribute has a length of zero, and therefore contains no other
 * information past the common attribute header.
 */
public class XorOnlyAttribute extends StunAttribute {

	public static final String NAME = "XOR-ONLY";
	public static final char DATA_LENGTH = 0;

	public XorOnlyAttribute() {
		super(StunAttribute.XOR_ONLY);
	}

	/**
	 * Sets this attribute's fields according to attributeValue array.
	 * 
	 * @param attributeValue
	 *            a binary array containing this attribute's field values and
	 *            NOT containing the attribute header.
	 * @param offset
	 *            the position where attribute values begin (most often offset
	 *            is equal to the index of the first byte after length)
	 * @param length
	 *            the length of the binary array.
	 * @throws StunException
	 *             if attrubteValue contains invalid data.
	 */
	public void decodeAttributeBody(byte[] attributeValue, char offset,
			char length) throws StunException {
		// nothing to do cause we have 0 length
	}

	/**
	 * Returns a binary representation of this attribute.
	 * 
	 * @return a binary representation of this attribute.
	 */
	public byte[] encode() {
		char type = getAttributeType();
		byte binValue[] = new byte[HEADER_LENGTH + getDataLength()];

		// Type
		binValue[0] = (byte) (type >> 8);
		binValue[1] = (byte) (type & 0x00FF);

		// Length
		binValue[2] = (byte) (getDataLength() >> 8);
		binValue[3] = (byte) (getDataLength() & 0x00FF);

		return binValue;
	}

	/**
	 * Returns the length of this attribute's body. (Which in the case of the
	 * XOR-ONLY attribute is 0);
	 * 
	 * @return the length of this attribute's value.
	 */
	public char getDataLength() {
		return DATA_LENGTH;
	}

	/**
	 * Returns the human readable name of this attribute.
	 * 
	 * @return this attribute's name.
	 */
	public String getName() {
		return NAME;
	}

	/**
	 * Compares two STUN Attributes. Two attributes are considered equal when
	 * they have the same type length and value.
	 * 
	 * @param obj
	 *            the object to compare this attribute with.
	 * @return true if the attributes are equal and false otherwise.
	 */

	public boolean equals(Object obj) {
		if (obj == null || !(obj instanceof XorOnlyAttribute)) {
			return false;
		}

		if (obj == this) {
			return true;
		}

		XorOnlyAttribute att = (XorOnlyAttribute) obj;
		if (att.getAttributeType() != getAttributeType()
				|| att.getDataLength() != getDataLength()) {
			return false;
		}
		return true;
	}
}