[RFA/JDWP] IdManager

[Keith Seitz <keiths at redhat dot com>]

Hi,

Okay, after the questions raised about ReferenceKey, I think I'm just
going to submit this and get opinions.

This class manages all the IDs that get assigned in the back-end and
sent to the debugger. There are two sides to this coin: one used by the
back-end to get IDs for objects and one used by the processor package to
get objects associated with IDs.

For an event notification, for example, might need the ThreadId of the
thread in which the event occurred. To do this, it would call the
IdManager's getId method, which will return the ID for the thread or
create a new ID for it.

Similarly, when the packet processor (or some other class in that
package) needs an object for a given ID, it can either call get (long)
or readId (DataInputStream) to get the ObjectId of the object. That can
then be used to get the desired object.

Comments/questions/concerns?
Keith

ChangeLog
2005-06-20  Keith Seitz  <keiths@redhat.com>

	* gnu/classpath/jdwp/id/IdManager.java: New file.

Keith

Index: gnu/classpath/jdwp/id/IdManager.java
===================================================================
RCS file: gnu/classpath/jdwp/id/IdManager.java
diff -N gnu/classpath/jdwp/id/IdManager.java
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ gnu/classpath/jdwp/id/IdManager.java	20 Jun 2005 14:49:52 -0000
@@ -0,0 +1,215 @@
+/* IdManager.java -- 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.id;
+
+import gnu.classpath.jdwp.exception.InvalidClassException;
+import gnu.classpath.jdwp.exception.InvalidObjectException;
+
+import java.lang.ref.Reference;
+import java.lang.ref.ReferenceQueue;
+import java.io.DataInputStream;
+import java.io.IOException;
+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.
+ *
+ * @author Keith Seitz  (keiths@redhat.com)
+ */
+public class IdManager
+{
+  // 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 (Class) 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;
+
+  /**
+   * Constructs a new <code>IdManager</code>
+   */
+  public IdManager ()
+  {
+    _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 getId (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 = JdwpIdFactory.newId (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;
+  }
+
+  /**
+   * Reads a numerical ID from the stream, returning
+   * the actual ID associated with it
+   *
+   * @returns the object id
+   * @throws IOException for any errors reading from the stream
+   * @throws InvaildObjectException if ID is not found
+   */
+  public ObjectId readId (DataInputStream is)
+    throws IOException, InvalidObjectException
+  {
+    // All IDs are longs, making this really easy
+    long nid = is.readLong ();
+    return get (nid);
+  }
+
+  /**
+   * Gets the reference type id for the given class, creating
+   * a new one if it does not already have an id
+   *
+   * @param theClazz  the class for which to get an ID
+   * @returns  the ID of the class
+   */
+  public ReferenceTypeId getReferenceTypeId (Class clazz)
+  {
+    ReferenceTypeId id = (ReferenceTypeId)_classTable.get (clazz);
+    if (id == null)
+      {
+	// Object not found. Make new id for it
+	id = JdwpIdFactory.newReferenceTypeId (clazz);
+	_classTable.put (clazz, 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;
+  }
+
+  /**
+   * Reads a numerical ID from the stream, returning
+   * the actual reference type ID associated with it
+   *
+   * @returns the JdwpId
+   * @throws IOException for any errors reading from the stream
+   * @throws InvaildObjectException if ID is not found
+   */
+  public ReferenceTypeId readReferenceTypeId (DataInputStream is)
+    throws IOException, InvalidClassException
+  {
+    // All IDs are longs, making this really easy
+    long nid = is.readLong ();
+    return getReferenceType (nid);
+  }
+}