gcc/libjava/classpath/java/rmi/MarshalledObject.java

/* MarshalledObject.java --
   Copyright (c) 1996, 1997, 1998, 1999, 2004, 2006 
   Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath 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, or (at your option)
any later version.
 
GNU Classpath is distributed in the hope that it will be useful, but
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

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along with GNU Classpath; see the file COPYING.  If not, write to the
Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
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combination.

As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
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terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
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this exception to your version of the library, but you are not
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exception statement from your version. */


package java.rmi;

import gnu.java.rmi.RMIMarshalledObjectInputStream;
import gnu.java.rmi.RMIMarshalledObjectOutputStream;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.Serializable;

/**
 * A <code>MarshalledObject</code> consists of a serialized object which is
 * marshalled according to the RMI specification.
 * <p>
 * An object passed to the constructor is serialized and tagged with the needed
 * URL to retrieve its class definition for remote usage. If the object is a 
 * remote reference its stub is serialized instead. The instance of this 
 * marshalled object can be later retrieved by its <code>get()</code> method.
 * </p>
 *
 * @author unknown
 */
public final class MarshalledObject
  implements Serializable
{
  // The following fields are from Java API Documentation "Serialized form"
  private static final long serialVersionUID = 8988374069173025854L;

  byte[] objBytes;
  byte[] locBytes;
  int hash;

  /**
   * Constructs a <code>MarshalledObject</code> from the given object.
   * 
   * @param obj the object to marshal
   * @throws IOException if an I/O error during serialization occurs.
   */
  public MarshalledObject(Object obj) throws IOException
  {
    ByteArrayOutputStream objStream = new ByteArrayOutputStream();
    RMIMarshalledObjectOutputStream stream = 
      new RMIMarshalledObjectOutputStream(objStream);
    stream.writeObject(obj);
    stream.flush();
    objBytes = objStream.toByteArray();
    locBytes = stream.getLocBytes();

    // The following algorithm of calculating hashCode is similar to String
    hash = 0;
    for (int i = 0; i < objBytes.length; i++)
      hash = hash * 31 + objBytes[i];
    
    if (locBytes != null)
      for (int i = 0; i < locBytes.length; i++)
        hash = hash * 31 + locBytes[i];
  }

  /**
   * Checks if the given object is equal to this marshalled object.
   * 
   * <p>Marshalled objects are considered equal if they contain the
   * same serialized object. Codebase annotations where the class 
   * definition can be downloaded are ignored in the equals test.</p>
   *
   * @param obj the object to compare.   
   * @return <code>true</code> if equal, <code>false</code> otherwise.
   */
  public boolean equals(Object obj)
  {
    if (! (obj instanceof MarshalledObject))
      return false;

    // hashCode even differs, don't do the time-consuming comparisons
    if (obj.hashCode() != hash)
      return false;

    MarshalledObject aobj = (MarshalledObject) obj;
    if (objBytes == null || aobj.objBytes == null)
      return objBytes == aobj.objBytes;
    if (objBytes.length != aobj.objBytes.length)
      return false;
    for (int i = 0; i < objBytes.length; i++)
      {
        if (objBytes[i] != aobj.objBytes[i])
          return false;
      }
    // Ignore comparison of locBytes(annotation)
    return true;
  }

  /**
   * Constructs and returns a copy of the internal serialized object.
   * 
   * @return The deserialized object.
   * 
   * @throws IOException if an I/O exception occurs during deserialization.
   * @throws ClassNotFoundException if the class of the deserialized object 
   * cannot be found.
   */
  public Object get() throws IOException, ClassNotFoundException
  {
    if (objBytes == null)
      return null;
    
    RMIMarshalledObjectInputStream stream = 
      new RMIMarshalledObjectInputStream(objBytes, locBytes);
    return stream.readObject();
  }

  public int hashCode()
  {
    return hash;
  }

}