unknownattributesattribute.java

stun的java实现

/*
 * Stun4j, the OpenSource Java Solution for NAT and Firewall Traversal.
 *
 * Distributable under LGPL license.
 * See terms of license at gnu.org.
 */
package net.java.stun4j.attribute;

import java.util.ArrayList;
import java.util.*;
import net.java.stun4j.StunException;

/**
 * The UNKNOWN-ATTRIBUTES attribute is present only in a Binding Error
 * Response or Shared Secret Error Response when the response code in
 * the ERROR-CODE attribute is 420.
 *
 * The attribute contains a list of 16 bit values, each of which
 * represents an attribute type that was not understood by the server.
 * If the number of unknown attributes is an odd number, one of the
 * attributes MUST be repeated in the list, so that the total length of
 * the list is a multiple of 4 bytes.
 *
 * 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
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 * |      Attribute 1 Type           |     Attribute 2 Type        |
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 * |      Attribute 3 Type           |     Attribute 4 Type    ...
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *
 * <p>Copyright: Copyright (c) 2003</p>
 * <p>Organisation: Louis Pasteur University, Strasbourg, France</p>
 * <p>Network Research Team (http://www-r2.u-strasbg.fr)</p></p>
 * @author Emil Ivov
 * @version 0.1
 */

public class UnknownAttributesAttribute extends Attribute
{
    /**
     * A list of attribute types that were not understood by the server.
     */
    private ArrayList unknownAttributes = new ArrayList();



    UnknownAttributesAttribute()
    {
        super(UNKNOWN_ATTRIBUTES);
    }

    /**
     * Returns the human readable name of this attribute. Attribute names do
     * not really matter from the protocol point of view. They are only used
     * for debugging and readability.
     * @return this attribute's name.
     */
    public String getName()
    {
        return NAME;
    }

    public static String NAME = "UNKNOWN-ATTRIBUTES";

   /**
    * Returns the length (in bytes) of this attribute's body.
    * If the number of unknown attributes is an odd number, one of the
    * attributes MUST be repeated in the list, so that the total length of
    * the list is a multiple of 4 bytes.
    * @return the length of this attribute's value (a multiple of 4).
    */
    public char getDataLength()
    {
        char len = (char)unknownAttributes.size();

        if( (len % 2 ) != 0 )
            len++;

        return (char)(len*2);
    }

    /**
     * Adds the specified attribute type to the list of unknown attributes.
     * @param attributeID the id of an attribute to be listed as unknown in this
     * attribute
     */
    public void addAttributeID(char attributeID)
    {
        //some attributes may be repeated for padding
        //(packet length should be divisable by 4)
        if(!contains(attributeID))
            unknownAttributes.add(new Character(attributeID));
    }

    /**
     * Verifies whether the specified attributeID is contained by this attribute.
     * @param attributeID the attribute id to look for.
     * @return true if this attribute contains the specified attribute id.
     */
    public boolean contains(char attributeID)
    {
        return unknownAttributes.contains(new Character(attributeID));
    }

    /**
     * Returns an iterator over the list of attribute IDs contained by this
     * attribute.
     * @return an iterator over the list of attribute IDs contained by this
     * attribute.
     */
    public Iterator getAttributes()
    {
        return unknownAttributes.iterator();

    }

    /**
     * Returns the number of attribute IDs contained by this class.
     * @return the number of attribute IDs contained by this class.
     */
    public int getAttributeCount()
    {
        return unknownAttributes.size();
    }

    /**
     * Returns the attribute id with index i.
     * @param index the index of the attribute id to return.
     * @return the attribute id with index i.
     */
    public char getAttribute(int index )
    {
        return ((Character)unknownAttributes.get(index)).charValue();
    }

    /**
     * Returns a binary representation of this attribute.
     * @return a binary representation of this attribute.
     */
    public byte[] encode()
    {
        byte binValue[] = new byte[getDataLength() + HEADER_LENGTH];
        int  offset     = 0;

        //Type
        binValue[offset++] = (byte) (getAttributeType() >> 8);
        binValue[offset++] = (byte) (getAttributeType() & 0x00FF);

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


        Iterator attributes = getAttributes();
        while (attributes.hasNext()) {
            char att = ((Character)attributes.next()).charValue();
            binValue[offset++] = (byte)(att>>8);
            binValue[offset++] = (byte)(att & 0x00FF);
        }

       // If the number of unknown attributes is an odd number, one of the
       // attributes MUST be repeated in the list, so that the total length of
       // the list is a multiple of 4 bytes.
       if(offset < binValue.length)
       {
           char att = getAttribute(0);
           binValue[offset++] = (byte) (att >> 8);
           binValue[offset++] = (byte) (att & 0x00FF);
       }


        return binValue;
    }

    /**
     * Compares two STUN Attributes. Attributeas are considered equal when their
     * type, length, and all data are the same.
     *
     * @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 instanceof UnknownAttributesAttribute)
            || obj == null)
            return false;

        if (obj == this)
            return true;

        UnknownAttributesAttribute att = (UnknownAttributesAttribute) obj;
        if (att.getAttributeType() != getAttributeType()
            || att.getDataLength() != getDataLength()
            || !unknownAttributes.equals(att.unknownAttributes)
        )
            return false;

        return true;

    }

    /**
     * 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.
     */
    void decodeAttributeBody(byte[] attributeValue, char offset, char length) throws
        StunException
    {

        if( (length % 2 ) != 0)
            throw new StunException("Attribute IDs are 2 bytes long and the "
                                    +"passed binary array has an odd length value.");
        char originalOffset = (char)offset;
        for(int i = offset; i < originalOffset + length; i+=2)
        {
            char attributeID = (char)( (attributeValue[offset++]<<8) |
                               (attributeValue[offset++]) );
            addAttributeID(attributeID);
        }

    }

}