package org.dbxml.core.corba;

/*
 * dbXML License, Version 1.0
 *
 *
 * Copyright (c) 1999-2001 The dbXML Group, L.L.C.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by
 *        The dbXML Group (http://www.dbxml.com/)."
 *    Alternately, this acknowledgment may appear in the software
 *    itself, if and wherever such third-party acknowledgments normally
 *    appear.
 *
 * 4. The names "dbXML" and "The dbXML Group" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For written permission, please contact
 *    info@dbxml.com.
 *
 * 5. Products derived from this software may not be called "dbXML",
 *    nor may "dbXML" appear in their name, without prior written
 *    permission of The dbXML Group.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE DBXML GROUP OR ITS CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
 * OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * $Id: SymbolDeserializer.java,v 1.3 2001/08/05 07:22:42 tom Exp $
 */

import org.dbxml.core.corba.db.*;

import org.dbxml.xml.*;
import org.dbxml.xml.dom.*;

import org.w3c.dom.*;

/**
 * SymbolDeserializer is a utility class for managing SymbolTables in
 * the client context of Wire Compression.
 */

public final class SymbolDeserializer {
   private static final byte[] EmptyBytes = new byte[0];
   private static final SymbolTableSymbols hcSyms = SymbolTableSymbols.getInstance();
   private static final Document elemFactory = new DocumentImpl();
   
   private SymbolTable syms = null; // The Collection's SymbolTable
   private long lastMod = 0;        // Last time we caught a SymbolTable modification
   
   public SymbolDeserializer() {
   }

   /**
    * convertToDocument converts the compressed EncodedBuffer to
    * a DOM Document.
    *
    * @param buffer The EncodedBuffer
    * @return The Document
    */
   public Document convertToDocument(EncodedBuffer buffer) {
      SymbolTable s = getSymbols(buffer);
      return new DocumentImpl(buffer.buf, s, null);
   }
   
   /**
    * getSymbols returns the current SymbolTable image for the
    * server-side Collection that is being managed.  The Symbol
    * table is shipped as part of an EncodedBuffer when the server
    * has determined that its image of the SymbolTable is out of
    * date.  This method either returns the current image or
    * extracts the new image from the EncodedBuffer.
    *
    * @param buffer The EncodedBuffer
    * @return The Symbol Table
    */
   public SymbolTable getSymbols(EncodedBuffer buffer) {
      if ( buffer.stamp != lastMod ) {
         lastMod = buffer.stamp;
         Document doc = new DocumentImpl(buffer.sym, hcSyms, null);
         if ( syms == null )
            syms = new SymbolTable();
         synchronized(syms) {
            syms.streamFromXML(doc.getDocumentElement());
         }
      }
      return syms;
   }
   
   /**
    * getLastModified returns the last modified time stamp of the
    * client's image of the managed Symbol Table.
    *
    * @return The last modified stamp
    */
   public long getLastModified() {
      return lastMod;
   }
}

