--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/src/share/classes/java/io/SerialCallbackContext.java	Tue Sep 28 01:09:10 2010 -0700
@@ -0,0 +1,58 @@
+  /*
+   * %W% %E%
+   *
+   * Copyright (c) 2006, 2010  Oracle and/or its affiliates. All rights reserved.
+   * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
+   */
+
+  package java.io;
+
+  /**
+   * Context during upcalls from object stream to class-defined
+   * readObject/writeObject methods.
+   * Holds object currently being deserialized and descriptor for current class.
+   *
+   * This context keeps track of the thread it was constructed on, and allows
+   * only a single call of defaultReadObject, readFields, defaultWriteObject
+   * or writeFields which must be invoked on the same thread before the class's
+   * readObject/writeObject method has returned.
+   * If not set to the current thread, the getObj method throws NotActiveException.
+   */
+  final class SerialCallbackContext {
+      private final Object obj;
+      private final ObjectStreamClass desc;
+      /**
+       * Thread this context is in use by.
+       * As this only works in one thread, we do not need to worry about thread-safety.
+       */
+      private Thread thread;
+
+      public SerialCallbackContext(Object obj, ObjectStreamClass desc) {
+          this.obj = obj;
+          this.desc = desc;
+          this.thread = Thread.currentThread();
+      }
+
+      public Object getObj() throws NotActiveException {
+          checkAndSetUsed();
+          return obj;
+      }
+
+      public ObjectStreamClass getDesc() {
+          return desc;
+      }
+
+      private void checkAndSetUsed() throws NotActiveException {
+          if (thread != Thread.currentThread()) {
+               throw new NotActiveException(
+                "not in readObject invocation or fields already read");
+          }
+          thread = null;
+      }
+
+      public void setUsed() {
+          thread = null;
+      }
+  }
+
+