--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/agent/src/share/classes/sun/jvm/hotspot/utilities/MessageQueue.java	Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,52 @@
+/*
+ * Copyright 2000 Sun Microsystems, Inc.  All Rights Reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code 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
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ *
+ */
+
+package sun.jvm.hotspot.utilities;
+
+/** <p> A two-way unbounded-length message queue useful for
+    communication between threads. Messages written on one side become
+    readable on the other in first-in, first-out order. This is an
+    interface to one of two "sides" of an underlying backend, for
+    example, the MessageQueueBackend. </p> */
+
+public interface MessageQueue {
+  /** This blocks until a message is available. Even if the thread is
+      interrupted while it is waiting, this will not return until a
+      message is written by the entity on the other side of the
+      queue. */
+  public Object readMessage();
+
+  /** This blocks for up to <code>millis</code> milliseconds until a
+      message is available. If no message becomes available within
+      this time period, or the thread is interrupted during the wait,
+      returns null. (This implies that passing the value null back and
+      forth is not distinguishable with this method.) Passing a value
+      of 0 for the <code>millis</code> argument causes this method to
+      return without blocking. The millis argument must be greater
+      than or equal to zero. */
+  public Object readMessageWithTimeout(long millis);
+
+  /** Write a message to the queue */
+  public void writeMessage(Object obj);
+}