DERSequence.java

/*
 * Copyright (C) 2006-2008 Alfresco Software Limited.
 *
 * 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.

 * As a special exception to the terms and conditions of version 2.0 of 
 * the GPL, you may redistribute this Program in connection with Free/Libre 
 * and Open Source Software ("FLOSS") applications as described in Alfresco's 
 * FLOSS exception.  You should have recieved a copy of the text describing 
 * the FLOSS exception, and it is also available here: 
 * http://www.alfresco.com/legal/licensing"
 */

package org.alfresco.jlan.server.auth.asn;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

/**
 * DER Sequence Class
 * 
 * <p>Class to hold a list of DERObjects.
 *
 * @author gkspencer
 */
public class DERSequence extends DERObject {

  // List of objects
  
  private List<DERObject> m_list;
  
  /**
   * Default constructor
   */
  public DERSequence() {
    m_list = new ArrayList<DERObject>();
  }
  
  /**
   * Class constructor
   * 
   * @param tagNo int
   */
  public DERSequence(int tagNo) {
    setTagNo( tagNo);
    m_list = new ArrayList<DERObject>();
  }
  
  /**
   * Return the count of objects in the sequence
   * 
   * @return int
   */
  public final int numberOfObjects() {
    return m_list.size();
  }
  
  /**
   * Return an object from the sequence
   * 
   * @param idx int
   * @return DERObject
   */
  public final DERObject getObjectAt(int idx) {
    DERObject derObj = null;
    
    if ( idx >= 0 && idx < m_list.size())
      derObj = m_list.get( idx);
    
    return derObj;
  }

  /**
   * Find a tagged object within the list
   * 
   * @param tagNo int
   * @return DERObject
   */
  public final DERObject getTaggedObject(int tagNo) {
    
    // Check if the list is empty
    
    if ( m_list == null || m_list.size() == 0)
      return null;
    
    // Search for the required tagged object
    
    for ( int i = 0; i < m_list.size(); i++) {
      DERObject derObj = m_list.get( i);
      
      if ( derObj.getTagNo() == tagNo)
        return derObj;
    }
    
    return null;
  }
  
  /**
   * Add an object to the sequence
   * 
   * @param derObj DERObject
   */
  public final void addObject( DERObject derObj) {
    m_list.add( derObj);
  }
  
  /**
   * DER decode the object
   * 
   * @param buf DERBuffer
   */
  public void derDecode(DERBuffer buf)
    throws IOException {
    
    // Get the object type
    
    int typ = buf.unpackType();
    if ( DER.isType(typ) != DER.Sequence)
      throw new IOException("Wrong DER type, expected Sequence");
    
    // Get the sequence length and current buffer position
    
    int len = buf.unpackLength();
    int pos = buf.getPosition();
    
    // Clear the list and tag number
    
    m_list.clear();
    setTagNo( NotTagged);
    
    // Read objects from the buffer and add to the sequence
    
    if ( len > 0) {
      
      // Read objects until sequence length data has been read
      
      while (( buf.getPosition() - pos) < len) {
        
        // Read an object from the buffer and add to the sequence
        
        DERObject obj = buf.unpackObject();
        addObject( obj);
      }
    }
  }

  /**
   * DER encode the object
   * 
   * @param buf DERBuffer
   */
  public void derEncode( DERBuffer buf)
    throws IOException {
    
    // Pack the elements into a seperate buffer to get the total length
    
    int totLen = 0;
    DERBuffer objBuf = new DERBuffer();
    
    if ( numberOfObjects() > 0) {
    
      for ( int i = 0; i < numberOfObjects(); i++) {
        
        // Pack the current object
        
        DERObject derObj = getObjectAt( i);
        objBuf.packObject( derObj);
      }
      
      // Get the total length for the sequence

      totLen = objBuf.getLength();
    }

    // Pack the data type
    
    buf.packByte( DER.Sequence + DER.Constructed);
    
    buf.packLength( totLen);
    if ( totLen > 0)
      buf.packBytes( objBuf);
  }

  /**
   * Enumerate the list
   * 
   * @return Iterator<DERObject>
   */
  public final Iterator<DERObject> getObjects() {
	  return m_list.iterator();
  }
  /**
   * Return the sequence as a string
   * 
   * @return String
   */
  public String toString() {
    StringBuffer str = new StringBuffer();
    
    str.append("[Sequence:");
    str.append(numberOfObjects());
    str.append("]");
    
    return str.toString();
  }
}