code: /*
   * 
   * $Id: PDFObject.java,v 1.3 2007/09/22 12:48:16 gil1 Exp $
   *
   * $Date: 2007/09/22 12:48:16 $
   *
   * This library is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public 
   * License as published by the Free Software Foundation; either 
   * version 2.1 of the License, or (at your option) any later version. 
   * 
   * This library 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 
   * Lesser General Public License for more details. 
   * 
   * You should have received a copy of the GNU Lesser General Public 
   * License along with this library; if not, write to the Free Software 
   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA 
   */
  package pdf;
  
  import java.io.*;
  import java.util.*;
  
  /**
   * This is the base class for all Objects that form the PDF document.
   *
   * @author Peter T Mount, http://www.retep.org.uk/pdf/
   * @author Eric Z. Beard, ericzbeard@hotmail.com
   * @version $Revision: 1.3 $, $Date: 2007/09/22 12:48:16 $
   */
  public abstract class PDFObject implements Serializable
  {
  
    /*
     * NOTE: The original class is the work of Peter T. Mount, who released it 
     * in the uk.org.retep.pdf package.  It was modified by Eric Z. Beard as 
     * follows: 
     * The package name was changed to gnu.pdf.  
     * The formatting was changed a little bit.
     * It is still licensed under the LGPL.
     */
  
    /**
     * This is the object's PDF Type
     */
    private String type;
      
    /**
     * This is the unique serial number for this object.
     */
    protected int objser;
      
    /**
     * This allows any PDF object to refer to the document being constructed.
     */
    protected PDFDocument pdfDocument;
      
        
    /**
     * This is usually called by extensors to this class, and sets the
     * PDF Object Type
     * @param type the PDF Object Type
     */
    public PDFObject(String type)
    {
      this.type = type;
    }
      
    /**
     * Returns the PDF Type of this object
     * @return The PDF Type of this object
     */
    public String getType()
    {
      return type;
    }
      
    /**
     * Returns the unique serial number of this object.
     * @return Unique serial number of this object.
     */
    public final int getSerialID()
    {
      return objser;
    }
      
    /**
     * Returns the PDF document this object belongs to.
     * @return PDF containing this object
     */
    public final PDFDocument getPDFDocument()
    {
      return pdfDocument;
    }
      
    /**
     * <p>Writes the object to the output stream.
     * This method must be overidden.</p>
     *
     * <p><b>Note:</b> It should not write any other objects, even if they are
     * it's Kids, as they will be written by the calling routine.</p>
     *
     * @param os OutputStream to send the object to
     * @exception IOException on error
     */
    public abstract void write(OutputStream os) throws IOException;
      
    /**
     * The write method should call this before writing anything to the
     * OutputStream. This will send the standard header for each object.
     *
     * <p>Note: There are a few rare cases where this method is not called.
     *
     * @param os OutputStream to write to
     * @exception IOException on error
     */
    public final void writeStart(OutputStream os) throws IOException
    {
      os.write(Integer.toString(objser).getBytes());
      os.write(" 0 obj\n<<\n".getBytes());
      if(type!=null) {
        os.write("/Type ".getBytes());
        os.write(type.getBytes());
        os.write("\n".getBytes());
      }
    }
  
  
  
      
    /**
     * The write method should call this after writing anything to the
     * OutputStream. This will send the standard footer for each object.
     *
     * <p>Note: There are a few rare cases where this method is not called.
     *
     * @param os OutputStream to write to
     * @exception IOException on error
     */
    public final void writeEnd(OutputStream os) throws IOException
    {
      os.write(">>\nendobj\n".getBytes());
    }
      
    /**
     * Returns the unique serial number in PDF format
     * @return the serial number in PDF format
     */
    public String toString()
    {
      return ""+objser+" 0 R";
    }
      
    /**
     * This utility method returns a String containing an array definition
     * based on a Vector containing PDFObjects
     * @param v Vector containing PDFObjects
     * @return String containing a PDF array
     */
    public static String toArray(Vector<? extends PDFObject> v)
    {
      if(v.size()==0)
        return "";
          
      StringBuffer b = new StringBuffer();
      String bs = "[";
      for(PDFObject x : v) {
        b.append(bs);
        b.append(x.toString());
        bs = " ";
      }
      b.append("]");
      return b.toString();
    }
  }
  