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SNMPSequence.java

/*
 * AirportBaseStationConfigurator
 *
 * Copyright (C) 2000, Jonathan Sevy <jsevy@mcs.drexel.edu>
 *
 * 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 */


package snmp;

import java.util.*;
import java.io.*;


/**
*     One of the most important SNMP classes. Represents a sequence of other SNMP data types.
*     Virtually all compound structures are subclasses of SNMPSequence - for example, the 
*     top-level SNMPMessage, and the SNMPPDU it contains, are both just specializations of 
*     SNMPSequence. Sequences are frequently nested within other sequences.
*/

public class SNMPSequence extends SNMPObject
{
      protected Vector sequence;    // Vector of whatever is in sequence
      
      protected int type = SNMPBERCodec.SNMPSEQUENCE;
            
      
      /**
      *     Create a new empty sequence.
      */
      
00047       public SNMPSequence()
      {
            sequence = new Vector();
      }
      
      
      
      
      /**
      *     Create a new SNMP sequence from the supplied Vector of SNMPObjects.
      *     @throws SNMPBadValueException Thrown if non-SNMP object supplied in Vector v.
      */
      
00060       public SNMPSequence(Vector v)
            throws SNMPBadValueException
      {
            
            Enumeration e = v.elements();
            
            while (e.hasMoreElements())
            {
                  if (!(e.nextElement() instanceof SNMPObject))
                        throw new SNMPBadValueException("Non-SNMPObject supplied to SNMPSequence.");
            }
            
            
            sequence = v;
      }
      
      
      
      
      /**
      *     Construct an SNMPMessage from a received ASN.1 byte representation.
      *     @throws SNMPBadValueException Indicates invalid SNMP sequence encoding supplied.
      */
      
00084       public SNMPSequence(byte[] enc)
            throws SNMPBadValueException
      {
            extractFromBEREncoding(enc);
      }
      
      
      
      
      
      /**
      *     Returns a Vector containing the SNMPObjects in the sequence.
      */
      
00098       public Object getValue()
      {
            return sequence;
      }
      
      
      
      
      
      /** 
      *     Used to set the contained SNMP objects from a supplied Vector.
      *     @throws SNMPBadValueException Indicates an incorrect object type supplied, or that the supplied
      *     Vector contains non-SNMPObjects.
      */
      
00113       public void setValue(Object newSequence)
            throws SNMPBadValueException
      {
            if (newSequence instanceof Vector)
            {
                  
                  // check that all objects in vector are SNMPObjects
                  
                  Enumeration e = ((Vector)newSequence).elements();
                  
                  while (e.hasMoreElements())
                  {
                        if (!(e.nextElement() instanceof SNMPObject))
                              throw new SNMPBadValueException("Non-SNMPObject supplied to SNMPSequence.");
                  }
                  
                  
                  this.sequence = (Vector)newSequence;
            }
            else
                  throw new SNMPBadValueException(" Sequence: bad object supplied to set value ");
      }
      
      
      
      /** 
      *     Return the number of SNMPObjects contained in the sequence.
      */
      
00142       public int size()
      {
            return sequence.size();
      }
      
      
      
      /** 
      *     Add the SNMP object to the end of the sequence.
      *     @throws SNMPBadValueException Relevant only in subclasses
      */
      
00154       public void addSNMPObject(SNMPObject newObject)
            throws SNMPBadValueException
      {
            sequence.insertElementAt(newObject, sequence.size());
      }
      
      
      
      
      
      /** 
      *     Return the SNMP object at the specified index. Indices are 0-based.
      */
      
00168       public SNMPObject getSNMPObjectAt(int index)
      {
            return (SNMPObject)(sequence.elementAt(index));
      }
      
      
      
      
      /** 
      *     Return the BER encoding for the sequence.
      */
      
00180       public byte[] getBEREncoding()
      {
            ByteArrayOutputStream outBytes = new ByteArrayOutputStream();
            
                  
            // recursively write contents of Vector
            byte[] data = encodeVector();
            
            // calculate encoding for length of data
            byte[] len = SNMPBERCodec.encodeLength(data.length);
            
            // encode T,L,V info
            outBytes.write(type);
            outBytes.write(len, 0, len.length);
            outBytes.write(data, 0, data.length);
            
            return outBytes.toByteArray();
      }
      
      
      
      private byte[] encodeVector()
      {
            ByteArrayOutputStream outBytes = new ByteArrayOutputStream();
            
            int numElements = sequence.size();
            for (int i = 0; i < numElements; ++i)
            {
                  byte[] nextBytes = ((SNMPObject)(sequence.elementAt(i))).getBEREncoding();
                  outBytes.write(nextBytes, 0, nextBytes.length);
            }
            
            return outBytes.toByteArray();
      }
      
      
      
      protected void extractFromBEREncoding(byte[] enc)
            throws SNMPBadValueException
      {
            Vector newVector = new Vector();
            
            int totalLength = enc.length;
            int position = 0;
            
            while (position < totalLength)
            {
                  SNMPTLV nextTLV = SNMPBERCodec.extractNextTLV(enc, position);
                  newVector.insertElementAt(SNMPBERCodec.extractEncoding(nextTLV), newVector.size());
                  position += nextTLV.totalLength;
            }
            
            sequence = newVector;
            
      }
      
      
      
      
      
      /** 
      *     Return a sequence of representations of the contained objects, separated by spaces
      *     and enclosed in parentheses.
      */
      
00245       public String toString()
      {
            String valueString = new String("(");
            
            
            for (int i = 0; i < sequence.size(); ++i)
            {
                  valueString +=  " " + ((SNMPObject)sequence.elementAt(i)).toString() + " ";
            }
            
            valueString += ")";
            return valueString;
      }
      
      
      
}

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