old-autovect-branch/libjava/classpath/gnu/classpath/jdwp/id/ObjectId.java

   1 /* ObjectId.java -- object IDs
   2    Copyright (C) 2005 Free Software Foundation
   3
   4 This file is part of GNU Classpath.
   5
   6 GNU Classpath is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU Classpath is distributed in the hope that it will be useful, but
  12 WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Classpath; see the file COPYING.  If not, write to the
  18 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19 02110-1301 USA.
  20
  21 Linking this library statically or dynamically with other modules is
  22 making a combined work based on this library.  Thus, the terms and
  23 conditions of the GNU General Public License cover the whole
  24 combination.
  25
  26 As a special exception, the copyright holders of this library give you
  27 permission to link this library with independent modules to produce an
  28 executable, regardless of the license terms of these independent
  29 modules, and to copy and distribute the resulting executable under
  30 terms of your choice, provided that you also meet, for each linked
  31 terms of your choice, provided that you also meet, for each linked
  32 independent module, the terms and conditions of the license of that
  33 module.  An independent module is a module which is not derived from
  34 or based on this library.  If you modify this library, you may extend
  35 this exception to your version of the library, but you are not
  36 obligated to do so.  If you do not wish to do so, delete this
  37 exception statement from your version. */
  38
  39
  40 package gnu.classpath.jdwp.id;
  41
  42 import gnu.classpath.jdwp.JdwpConstants;
  43 import gnu.classpath.jdwp.exception.InvalidObjectException;
  44
  45 import java.io.DataOutputStream;
  46 import java.io.IOException;
  47
  48 /**
  49  * This is a base class for all ObjectID-like entities in JDWP,
  50  * inculding Objects, ClassObject, ClassLoader, Thread, ThreadGroup,
  51  * etc.
  52  *
  53  * @author Keith Seitz  <keiths@redhat.com>
  54  */
  55 public class ObjectId
  56   extends JdwpId
  57 {
  58   /**
  59    * The object class that this id represents
  60    */
  61   public static final Class typeClass = Object.class;
  62
  63   // Handle to disable garbage collection
  64   private Object _handle;
  65
  66   /**
  67    * Constructs a new <code>ObjectId</code>
  68    */
  69   public ObjectId ()
  70   {
  71     super (JdwpConstants.Tag.OBJECT);
  72   }
  73
  74   /**
  75    * Constructs a new <code>ObjectId</code> of the
  76    * given type.
  77    *
  78    * @param  tag  the tag of this type of object ID
  79    */
  80   public ObjectId (byte tag)
  81   {
  82     super (tag);
  83   }
  84
  85   /**
  86    * Returns the size of this id type
  87    */
  88   public int size ()
  89   {
  90     return 8;
  91   }
  92
  93   /**
  94    * Returns the object referred to by this ID
  95    *
  96    * @returns the object
  97    * @throws InvalidObjectException if the object was garbage collected
  98    *           or is invalid
  99    */
 100   public Object getObject ()
 101     throws InvalidObjectException
 102   {
 103     Object obj = _reference.get ();
 104     if (obj == null)
 105       throw new InvalidObjectException (_id);
 106
 107     return obj;
 108   }
 109
 110   /**
 111    * Writes the id to the stream
 112    *
 113    * @param outStream  the stream to which to write
 114    * @throws IOException  when an error occurs on the <code>OutputStream</code>
 115    */
 116   public void write (DataOutputStream outStream)
 117     throws IOException
 118   {
 119     // All we need to do is write out our id as an 8-byte integer
 120     outStream.writeLong (_id);
 121   }
 122
 123   /**
 124    * Disable garbage collection on object
 125    */
 126   public void disableCollection ()
 127     throws InvalidObjectException
 128   {
 129     _handle = getObject ();
 130   }
 131
 132   /**
 133    * Enable garbage collection on object
 134    */
 135   public void enableCollection ()
 136   {
 137     _handle = null;
 138   }
 139 }