Hi,
This patch adds a wrapper for null objects for JDWP. In order to
distinguish between valid(object id 0) and invalid(null pointer) null
values, the NullObject class has been created to represent a case where
null is a valid value. This patch also update the reference VMIdManager
to properly create NullObjectIds (object id 0) which hold references to
NullObjects.
ChangeLog
2007-02-27 Kyle Galloway <[EMAIL PROTECTED]>
* gnu/classpath/jdwp/id/NullObjectId.java: New class.
* gnu/classpath/jdwp/util/NullObject.java: New class.
* vm/reference/gnu/classpath/jdwp/VMIdManager.java (getObjectId):
Handle null object.
(get): Handle objectId of 0.
Index: vm/reference/gnu/classpath/jdwp/VMIdManager.java
===================================================================
RCS file: /sources/classpath/classpath/vm/reference/gnu/classpath/jdwp/VMIdManager.java,v
retrieving revision 1.7
diff -u -r1.7 VMIdManager.java
--- vm/reference/gnu/classpath/jdwp/VMIdManager.java 9 Mar 2006 23:18:29 -0000 1.7
+++ vm/reference/gnu/classpath/jdwp/VMIdManager.java 27 Feb 2007 21:26:53 -0000
@@ -337,6 +337,10 @@
*/
public ObjectId getObjectId (Object theObject)
{
+ // Special case: null
+ if (theObject == null)
+ return new NullObjectId ();
+
ReferenceKey ref = new ReferenceKey (theObject, _refQueue);
ObjectId id = (ObjectId) _oidTable.get (ref);
if (id == null)
@@ -364,6 +368,10 @@
public ObjectId get (long id)
throws InvalidObjectException
{
+ // Special case: null
+ if (id == 0)
+ return new NullObjectId ();
+
ObjectId oid = (ObjectId) _idTable.get (new Long (id));
if (oid == null)
throw new InvalidObjectException (id);
Index: gnu/classpath/jdwp/id/NullObjectId.java
===================================================================
RCS file: gnu/classpath/jdwp/id/NullObjectId.java
diff -N gnu/classpath/jdwp/id/NullObjectId.java
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ gnu/classpath/jdwp/id/NullObjectId.java 1 Jan 1970 00:00:00 -0000
@@ -0,0 +1,42 @@
+package gnu.classpath.jdwp.id;
+
+import gnu.classpath.jdwp.exception.InvalidObjectException;
+import gnu.classpath.jdwp.util.NullObject;
+
+import java.lang.ref.SoftReference;
+
+/**
+ * This is a special case of an ObjectId. When a varaible slot contains
+ * null as its value, this is a valid value despite the fact that it does
+ * not reference an object. To represent this, this will always be the id
+ * of the NullObject (0).
+ *
+ * @author Kyle Galloway <[EMAIL PROTECTED]>
+ */
+public class NullObjectId
+ extends ObjectId
+{
+ /**
+ * The object class that this id represents
+ */
+ public static final Class typeClass = NullObject.class;
+
+ /**
+ * Constructs a new <code>NullObjectId</code>
+ */
+ public NullObjectId()
+ {
+ super();
+ setId((long) 0);
+ _reference = new SoftReference<NullObject>(new NullObject());
+ try
+ {
+ disableCollection();
+ }
+ catch(InvalidObjectException ex)
+ {
+ //This will not happen
+ }
+ }
+
+}
Index: gnu/classpath/jdwp/util/NullObject.java
===================================================================
RCS file: gnu/classpath/jdwp/util/NullObject.java
diff -N gnu/classpath/jdwp/util/NullObject.java
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ gnu/classpath/jdwp/util/NullObject.java 1 Jan 1970 00:00:00 -0000
@@ -0,0 +1,13 @@
+package gnu.classpath.jdwp.util;
+
+/**
+ * This is a placeholder for null. There are several places in JDWP where null
+ * is a valid value (i.e. when geting the value of a variable slot that
+ * contains a null reference at that time). This class distinguishes between
+ * these "meaningful" null values and invalid null pointers.
+ *
+ * @author Kyle Galloway <[EMAIL PROTECTED]>
+ */
+public class NullObject
+{
+}
