* vm/reference/gnu/classpath/jdwp/VMIdManager.java: New file

        with example implementation of ID-management for JDWP back-end.
        * gnu/classpath/jdwp/id/JdwpIdFactory.java: Removed. Now part of
        VMIdManager.

1 files changed, 434 insertions, 0 deletions

diff --git a/vm/reference/gnu/classpath/jdwp/VMIdManager.java b/vm/reference/gnu/classpath/jdwp/VMIdManager.java
new file mode 100644
index 000000000..e5b8447d2
--- /dev/null
+++ b/vm/reference/gnu/classpath/jdwp/VMIdManager.java
@@ -0,0 +1,434 @@
+/* VMIdManager.java -- A reference/example implementation of a manager for
+   JDWP object/reference type IDs
+
+   Copyright (C) 2005 Free Software Foundation
+
+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
+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 GNU Classpath; see the file COPYING.  If not, write to the
+Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+02111-1307 USA.
+
+Linking this library statically or dynamically with other modules is
+making a combined work based on this library.  Thus, the terms and
+conditions of the GNU General Public License cover the whole
+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
+modules, and to copy and distribute the resulting executable under
+terms of your choice, provided that you also meet, for each linked
+terms of your choice, provided that you also meet, for each linked
+independent module, the terms and conditions of the license of that
+module.  An independent module is a module which is not derived from
+or based on this library.  If you modify this library, you may extend
+this exception to your version of the library, but you are not
+obligated to do so.  If you do not wish to do so, delete this
+exception statement from your version. */
+
+
+package gnu.classpath.jdwp;
+
+import gnu.classpath.jdwp.exception.InvalidClassException;
+import gnu.classpath.jdwp.exception.InvalidObjectException;
+import gnu.classpath.jdwp.id.*;
+
+import java.lang.ref.Reference;
+import java.lang.ref.ReferenceQueue;
+import java.lang.ref.SoftReference;
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.util.HashMap;
+import java.util.Hashtable;
+import java.util.Iterator;
+
+/**
+ * This class manages objects and referencetypes that are reported
+ * to the debugger. All objects and referencetypes reported to the
+ * debugger should go through this manager.
+ *
+ * A brief summary of what an <code>IdManager</code> must provide:
+ *
+ * <code>
+ * public ObjectId getObjectId (Object theObject);
+ * public ObjectId get (long id);
+ * public ObjectId readObjectId (ByteBuffer bb);
+ * public ReferenceTypeId getReferenceTypeId (Class clazz);
+ * public ReferenceTypeId getReferenceType (long id);
+ * public ReferenceTypeId readReferenceTypeId (ByteBuffer bb);
+ * </code>
+ *
+ * See the javadoc on these methods later in this file for more
+ * information on these functions.
+ *
+ * <b>NOTE:</b> All IDs handled by the ID manager (all object and reference
+ * type IDs) are assumed to be of type <code>long</code>.
+ *
+ * @author Keith Seitz  (keiths@redhat.com)
+ */
+public class VMIdManager
+{
+  // This factory generates ids for objects and types that may
+  // be sent to a debugger.
+  private static class IdFactory
+  {
+    // ID of last object / referencetype
+    private static Object _idLock = new Object ();
+    private static Object _ridLock = new Object ();
+    private static long _lastId = 0;
+    private static long _lastRid = 0;
+
+    // A list of all ID types
+    private static HashMap _idList = new HashMap ();
+
+    // Initialize the id list with known types
+    static
+    {
+      // ObjectId and ArrayId are special cases. See newObjectId.
+      _idList.put (ClassLoaderId.typeClass, ClassLoaderId.class);
+      _idList.put (ClassObjectId.typeClass, ClassObjectId.class);
+      //_idList.put (FieldId.typeClass, FieldId.class);
+      //_idList.put (FrameId.typeClass, FrameId.class);
+      //_idList.put (MethodId.typeClass, MethodId.class);
+      _idList.put (StringId.typeClass, StringId.class);
+      _idList.put (ThreadId.typeClass, ThreadId.class);
+      _idList.put (ThreadGroupId.typeClass, ThreadGroupId.class);
+    }
+
+    /**
+     * Returns a new id for the given object
+     *
+     * @param object  the object for which an id is desired
+     * @returns a suitable object id
+     */
+    public static ObjectId newObjectId (SoftReference obj)
+    {
+      ObjectId id = null;
+      Object object = obj.get ();
+
+      // Special case: arrays
+      if (object.getClass ().isArray ())
+	id = new ArrayId ();
+      else
+	{
+	  // Loop through all classes until we hit baseclass
+	  Class myClass;
+	  for (myClass = object.getClass (); myClass != null;
+	       myClass = myClass.getSuperclass ())
+	    {
+	      Class clz = (Class) _idList.get (myClass);
+	      if (clz != null)
+		{
+		  try
+		    {
+		      id = (ObjectId) clz.newInstance ();
+		      synchronized (_idLock)
+			{
+			  id.setId (++_lastId);
+			}
+		      return id;
+		    }
+		  catch (InstantiationException ie)
+		    {
+		      // This really should not happen
+		      throw new RuntimeException ("cannot create new ID", ie);
+		    }
+		  catch (IllegalAccessException iae)
+		    {
+		      // This really should not happen
+		      throw new RuntimeException ("illegal access of ID", iae);
+		    }
+		}
+	    }
+
+	  /* getSuperclass returned null and no matching ID type found.
+	     So it must derive from Object. */
+	  id = new ObjectId ();
+	}
+
+      synchronized (_idLock)
+	{
+	  id.setId (++_lastId);
+	}
+
+      return id;
+    }
+
+    /**
+     * Returns a new reference type id for the given class
+     *
+     * @param clazz  the <code>Class</code> for which an id is desired
+     * @returns a suitable reference type id or <code>null</code>
+     */
+    public static ReferenceTypeId newReferenceTypeId (SoftReference ref)
+    {
+      ReferenceTypeId id = null;
+      Class clazz = (Class) ref.get ();
+
+      try
+	{
+	  if (clazz.isArray ())
+	    id = new ArrayReferenceTypeId ();
+	  else if (clazz.isInterface ())
+	    id = new InterfaceReferenceTypeId ();
+	  else
+	    id = new ClassReferenceTypeId ();
+	  synchronized (_ridLock)
+	    {
+	      id.setId (++_lastRid);
+	    }
+	  return id;
+	}
+      catch (InstantiationException ie)
+	{
+	  return null;
+	}
+      catch (IllegalAccessException iae)
+	{
+	  return null;
+	}
+    }
+  }
+
+  /**
+   * This class is a SoftReferenceIdentity type that is used by
+   * the ID manager.
+   */
+  class ReferenceKey extends SoftReference
+  {
+    // Hash code of referent
+    private int _hash;
+
+    /**
+     * Constructs a new <code>ReferenceKey</code> object
+     * with the given referent.
+     *
+     * <p>This constructor should only be used for object lookups
+     * by the backend.
+     *
+     * @param referent  the object to reference
+     */
+    public ReferenceKey (Object referent)
+    {
+      super (referent);
+      _hash = referent.hashCode ();
+    }
+    
+    /**
+     * Constructs a new <code>ReferenceKey</code> object
+     * with the given referent and reference queue.
+     *
+     * <p>The JDWP back-end stores a <code>ReferenceKey</code>
+     * with its corresponding <code>JdwpId</code>. This constructor
+     * is used by the back-end when adding new IDs to be managed.
+     *
+     * @param referent  the object to reference
+     * @param queue     the queue to which to report garbage collections
+     */
+    public ReferenceKey (Object referent, ReferenceQueue queue)
+    {
+      super (referent, queue);
+      _hash = referent.hashCode ();
+    }
+    
+    /**
+     * Returns the hash code of the referent.
+     * This seems hacky, but is required in order to use this class
+     * as a hash table key.
+     *
+     * @returns the hash code of the referent
+     */
+    public int hashCode ()
+    {
+      return _hash;
+    }
+
+    /**
+     * Comparator for keys
+     *
+     * This method can be used in two ways:
+     *
+     * <ol>
+     *    <li>For table lookups, where we want to compare referents</li>
+     *    <li>For clearing GCd objects, where we want to compare the actual
+     *        key object (not the referent)</li>
+     * </ol>
+     */
+    public boolean equals (Object obj)
+    {
+      if (obj instanceof ReferenceKey)
+	{
+	  ReferenceKey ref = (ReferenceKey) obj;
+	  
+	  /* First check if the two references are the same.
+	     If they are, that means we must be clearing GCd objects. */
+	  if (this == obj)
+	    return true;
+	  
+	  return (ref.get () == get ());
+	}
+      
+      return false;
+    }
+  }
+  
+  // instance of VMIdManager
+  private static VMIdManager _idm = new VMIdManager ();
+
+  // A reference queue for our objects
+  private ReferenceQueue _refQueue;
+
+  // Mapping of objects (ReferenceKey) to IDs (ObjectId)
+  private Hashtable _oidTable;
+
+  // Mapping of ID numbers (Long) to IDs (ObjectId)
+  private Hashtable _idTable;
+
+  /* Mapping of class (ReferenceKey) to IDs (ReferenceTypeId) for reference
+     types. Unlike other types, reference id types are NEVER released. */
+  private Hashtable _classTable;
+
+  // Mapping of ID numbers (Long) to reference type IDs (ReferenceTypeId)
+  private Hashtable _ridTable;
+
+  /**
+   * Gets the instance of VMIdManager, constructing a new one
+   * if none currently exists.
+   */
+  public static VMIdManager getDefault ()
+  {
+    return _idm;
+  }
+
+  // Constructs a new <code>IdManager</code>
+  private VMIdManager ()
+  {
+    _refQueue = new ReferenceQueue ();
+    _oidTable = new Hashtable (50);
+    _idTable = new Hashtable (50);
+    _classTable = new Hashtable (20);
+    _ridTable = new Hashtable (20);
+  }
+
+  // Updates the object ID table, removing IDs whose objects have
+  // been garbage collected.
+  private void _update ()
+  {
+    Reference ref;
+    while ((ref = _refQueue.poll ()) != null)
+      {
+	ObjectId id = (ObjectId) _oidTable.get (ref);
+	_oidTable.remove (ref);
+	_idTable.remove (new Long (id.getId ()));
+      }
+  }
+
+  /**
+   * Returns an id for the given object, adding it
+   * if it does not have an id.
+   *
+   * @param theObject  the object to get an ID/add
+   * @returns  the ID of the object
+   */
+  public ObjectId getObjectId (Object theObject)
+  {
+    ReferenceKey ref = new ReferenceKey (theObject, _refQueue);
+    ObjectId id = (ObjectId) _oidTable.get (ref);
+    if (id == null)
+      {
+	// update the tables -- this is an arbitrary place to put this
+	_update ();
+
+	// Object not found. Make new id for it
+	id = IdFactory.newObjectId (ref);
+	_oidTable.put (ref, id);
+	_idTable.put (new Long (id.getId ()), id);
+      }
+
+    return id;
+  }
+
+  /**
+   * Returns the <code>JdwpId</code> for a given ID. Unlike
+   * <code>getId</code>, it throws an exception if the ID is not
+   * known.
+   *
+   * @param id  the numerical ID of the desired <code>JdwpId</code>
+   * @throws InvalidObjectException if the ID is not found
+   */
+  public ObjectId get (long id)
+    throws InvalidObjectException
+  {
+    ObjectId oid = (ObjectId) _idTable.get (new Long (id));
+    if (oid == null)
+      throw new InvalidObjectException (id);
+ 
+    return oid;
+  }
+
+  public ObjectId readObjectId (ByteBuffer bb)
+    throws InvalidObjectException
+  {
+    long id = bb.getLong ();
+    return get (id);
+  }
+
+  /**
+   * Gets the reference type id for the given class, creating
+   * a new one if it does not already have an id
+   *
+   * @param clazz  the class for which to get an ID
+   * @returns  the ID of the class
+   */
+  public ReferenceTypeId getReferenceTypeId (Class clazz)
+  {
+    ReferenceKey ref = new ReferenceKey (clazz);
+    ReferenceTypeId id = (ReferenceTypeId)_classTable.get (ref);
+    if (id == null)
+      {
+	// Object not found. Make new id for it
+	id = IdFactory.newReferenceTypeId (ref);
+	_classTable.put (ref, id);
+	_ridTable.put (new Long (id.getId ()), id);
+      }
+
+    return id;
+  }
+
+  /**
+   * Returns the <code>ReferenceTypeId</code> for a given ID. Unlike
+   * <code>getReferenceTypeId</code>, it throws an exception if the ID is not
+   * known.
+   *
+   * @param id  the numerical ID of the desired reference type
+   * @throws InvalidClassException if the ID is not found
+   */
+  public ReferenceTypeId getReferenceType (long id)
+    throws InvalidClassException
+  {
+    ReferenceTypeId rid = (ReferenceTypeId) _ridTable.get (new Long (id));
+    if (rid == null)
+      throw new InvalidClassException (id);
+ 
+    return rid;
+  }
+
+  public ReferenceTypeId readReferenceTypeId (ByteBuffer bb)
+    throws InvalidClassException
+  {
+    long id = bb.getLong ();
+    return getReferenceType (id);
+  }
+}