[cp-patches] [PATCH/JDWP] Event management/notification (really!)

[Keith Seitz]

Hi,

Okay, at long, long last, and after many rewrites/redesigns, and much 
lost hair, I think I've arrived at something which addresses people's 
conerns, yet doesn't contradict my intentions for this class.

<nitty-gritty-details>
The real problem is that there are two different ways to deal with 
events because there are really two main classes of events: one which 
doesn't necessarily need intervention from the VM and one which 
absolutely does.

The first class (not requiring VM intervention) is mainly one-off-ish 
events, like class load/unload, thread death/start, and the like. For 
most of these events, it is probably just easiest to allow EventManager 
to apply all the possible filters that may have been requested by the 
debugger. This was largely the same as a patch I posted many moons ago. 
The big difference is that today, this is not required in any way. VM 
adapters don't have to use this facility at all for filtering anything.

The second class (requiring VM intervention) contains those more 
nebulous execution-related events like breakpoints, field accesses, 
frame pops, etc. For this class of events, the VM is largely responsible 
for event notifications. However, at the discretion of the VM adapter, 
EventManager may once again be used to do the filtering.

So, there it is. EventManager ALWAYS records the debugger's event 
requests. Depending on how the VM implements event notifications, this 
information may or may not be used for filtering. [For example, calling 
Jdwp.notify will cause EventManager to evaluate filters on the event. 
However calling Jdwp.sendEvent bypasses all of this and sends the event 
notification down the wire.
</nitty-gritty-details>

Keith

ChangeLog
2005-08-25  Keith Seitz  <address@hidden>

        * gnu/classpath/jdwp/event/EventManager.java: New file
        concerning JDWP event request management and notification
        infrastructure.

Index: gnu/classpath/jdwp/event/EventManager.java
===================================================================
RCS file: gnu/classpath/jdwp/event/EventManager.java
diff -N gnu/classpath/jdwp/event/EventManager.java
--- /dev/null   1 Jan 1970 00:00:00 -0000
+++ gnu/classpath/jdwp/event/EventManager.java  25 Aug 2005 20:55:19 -0000
@@ -0,0 +1,293 @@
+/* EventManager.java -- event management and notification infrastructure
+   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., 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
+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.event;
+
+import gnu.classpath.jdwp.VMVirtualMachine;
+import gnu.classpath.jdwp.exception.InvalidEventTypeException;
+
+import java.util.Collection;
+import java.util.Hashtable;
+import java.util.Iterator;
+
+/**
+ * Manages event requests and filters event notifications.
+ *
+ * The purpose of this class is actually two-fold:
+ * 
+ * 1) Maintain a list of event requests from the debugger
+ * 2) Filter event notifications from the VM
+ * 
+ * If an event request arrives from the debugger, the back-end will
+ * call address@hidden #reqestEvent}, which will first check for a valid event.
+ * If it is valid, <code>EventManager</code> will record the request
+ * internally and register the event with the virtual machine, which may
+ * choose to handle the request itself (as is likely the case with
+ * breakpoints and other execution-related events), or it may decide to
+ * allow the <code>EventManager</code> to handle notifications and all
+ * filtering (which is convenient for other events such as class (un)loading).
+ * 
+ * @author Keith Seitz  (address@hidden)
+ */
+public class EventManager
+{
+  // Single instance
+  private static EventManager _instance = new EventManager ();
+
+  // maps event (EVENT_*) to lists of EventRequests
+  private Hashtable _requests = null;
+
+  /**
+   * Returns an instance of the event manager
+   *
+   * @return the event manager
+   */
+  public static EventManager getDefault ()
+  {
+    return _instance;
+  }
+
+  // Private constructs a new <code>EventManager</code>
+  private EventManager ()
+  {
+    _requests = new Hashtable ();
+
+    // Add lists for all the event types
+    _requests.put (new Byte (EventRequest.EVENT_SINGLE_STEP),
+                  new Hashtable ());
+    _requests.put (new Byte (EventRequest.EVENT_BREAKPOINT),
+                  new Hashtable ());
+    _requests.put (new Byte (EventRequest.EVENT_FRAME_POP),
+                  new Hashtable ());
+    _requests.put (new Byte (EventRequest.EVENT_EXCEPTION),
+                  new Hashtable ());
+    _requests.put (new Byte (EventRequest.EVENT_USER_DEFINED),
+                  new Hashtable ());
+    _requests.put (new Byte (EventRequest.EVENT_THREAD_START),
+                  new Hashtable ());
+    _requests.put (new Byte (EventRequest.EVENT_THREAD_END),
+                  new Hashtable ());
+    _requests.put (new Byte (EventRequest.EVENT_CLASS_PREPARE),
+                  new Hashtable ());
+    _requests.put (new Byte (EventRequest.EVENT_CLASS_UNLOAD),
+                  new Hashtable ());
+    _requests.put (new Byte (EventRequest.EVENT_CLASS_LOAD),
+                  new Hashtable ());
+    _requests.put (new Byte (EventRequest.EVENT_FIELD_ACCESS),
+                  new Hashtable ());
+    _requests.put (new Byte (EventRequest.EVENT_FIELD_MODIFY),
+                  new Hashtable ());
+    _requests.put (new Byte (EventRequest.EVENT_METHOD_ENTRY),
+                  new Hashtable ());
+    _requests.put (new Byte (EventRequest.EVENT_METHOD_EXIT),
+                  new Hashtable ());
+    _requests.put (new Byte (EventRequest.EVENT_VM_INIT),
+                  new Hashtable ());
+    _requests.put (new Byte (EventRequest.EVENT_VM_DEATH),
+                  new Hashtable ());
+
+    // Add auto-generated event notifications
+    // only two: VM_INIT, VM_DEATH
+    try
+      {
+       requestEvent (new EventRequest (0,
+                                       EventRequest.EVENT_VM_INIT,
+                                       EventRequest.SUSPEND_NONE));
+       requestEvent (new EventRequest (0,
+                                       EventRequest.EVENT_VM_DEATH,
+                                       EventRequest.SUSPEND_NONE));
+      }
+    catch (InvalidEventTypeException e)
+      {
+       // This can't happen
+      }
+  }
+
+  /**
+   * Returns a request for the given event. This method will only
+   * be used if the <code>EventManager</code> is handling event filtering.
+   *
+   * @param  event  the event
+   * @return request that was interested in this event
+   *         or <code>null</code> if none (and event should not be sent)
+   * @throws IllegalArgumentException for invalid event kind
+   */
+  public EventRequest getEventRequest (Event event)
+  {
+    EventRequest interestedRequest = null;
+    Hashtable requests;
+    Byte kind = new Byte (event.getEventKind ());
+    requests = (Hashtable) _requests.get (kind);
+    if (requests == null)
+      {
+       // Did not get a valid event type
+       throw new IllegalArgumentException ("invalid event kind: " + kind);
+      }
+    boolean match = false;
+
+    // Loop through the requests. Must look at ALL requests in order
+    // to evaluate all filters (think count filter).
+    // TODO: What if multiple matches? Spec isn't so clear on this.
+    Iterator rIter = requests.values().iterator ();
+    while (rIter.hasNext ())
+      {
+       EventRequest request = (EventRequest) rIter.next ();
+       if (request.matches (event))
+         interestedRequest = request;
+      }
+
+    return interestedRequest;
+  }
+
+  /**
+   * Requests monitoring of an event.
+   *
+   * The debugger registers for event notification through
+   * an event filter. If no event filter is specified for an event
+   * in the VM, it is assumed that the debugger is not interested in
+   * receiving notifications of this event.
+   *
+   * The virtual machine will be notified of the request.
+   *
+   * @param request  the request to monitor
+   * @throws InvalidEventTypeException for invalid event kind
+   */
+  public void requestEvent (EventRequest request)
+    throws InvalidEventTypeException
+  {
+    // Add request to request list
+    Hashtable requests;
+    Byte kind = new Byte (request.getEventKind ());
+    requests = (Hashtable) _requests.get (kind);
+    if (requests == null)
+      {
+       // Did not get a valid event type
+       throw new InvalidEventTypeException (request.getEventKind ());
+      }
+
+    // Register the event with the VM
+    VMVirtualMachine.getDefault().registerEvent (request);
+    requests.put (new Integer (request.getId ()), request);
+  }
+
+  /**
+   * Deletes the given request from the management table
+   *
+   * @param  kind  the event kind
+   * @param  id    the ID of the request to delete
+   * @throws IllegalArgumentException for invalid event kind
+   */
+  public void deleteRequest (byte kind, int id)
+  {
+    Hashtable requests;
+    requests = (Hashtable) _requests.get (new Byte (kind));
+    if (requests == null)
+      {
+       // Did not get a valid event type
+       throw new IllegalArgumentException ("invalid event kind: " + kind);
+      }
+
+    Integer iid = new Integer (id);
+    EventRequest request = (EventRequest) requests.get (iid);
+    if (request != null)
+      {
+       VMVirtualMachine.getDefault().unregisterEvent (request);
+       requests.remove (iid);
+      }
+  }
+
+  /**
+   * Clears all the requests for a given event
+   *
+   * @param  kind  the event kind
+   * @throws IllegalArgumentException for invalid event kind
+   */
+  public void clearRequests (byte kind)
+  {
+    Hashtable requests = (Hashtable) _requests.get (new Byte (kind));
+    if (requests == null)
+      {
+       // Did not get a valid event type
+       throw new IllegalArgumentException ("invalid event kind: " + kind);
+      }
+
+    VMVirtualMachine.getDefault().clearEvents (kind);
+    requests.clear ();
+  }
+
+  /**
+   * Returns a given event request for an event
+   *
+   * @param  kind  the kind of event for the request
+   * @param  id    the integer request id to return
+   * @return  the request for the given event kind with the given id
+   *          (or <code>null</code> if not found)
+   * @throws IllegalArgumentException for invalid event kind
+   */
+  public EventRequest getRequest (byte kind, int id)
+  {
+    Hashtable requests = (Hashtable) _requests.get (new Byte (kind));
+    if (requests == null)
+      {
+       // Did not get a valid event type
+       throw new IllegalArgumentException ("invalid event kind: " + kind);
+      }
+
+    return (EventRequest) requests.get (new Integer (id));
+  }
+
+  /**
+   * Returns all requests of the given event kind
+   *
+   * @param  kind  the event kind
+   * @returns a <code>Collection</code> of all the registered requests
+   * @throws IllegalArgumentException for invalid event kind
+   */
+  public Collection getRequests (byte kind)
+  {
+    Hashtable requests = (Hashtable) _requests.get (new Byte (kind));
+    if (requests == null)
+      {
+       // Did not get a valid event type
+       throw new IllegalArgumentException ("invalid event kind: " + kind);
+      }
+    
+    return requests.values ();
+  }
+}