--- /dev/null	2018-04-03 12:55:20.301839954 +0200
+++ new/src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/gc/z/ZForwardingTableEntry.java	2018-06-06 00:42:35.858511279 +0200
@@ -0,0 +1,55 @@
+/*
+ * Copyright (c) 2018, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+package sun.jvm.hotspot.gc.z;
+
+import sun.jvm.hotspot.debugger.Address;
+
+class ZForwardingTableEntry {
+    private Address entry;
+
+    ZForwardingTableEntry(Address addr) {
+        entry = addr;
+    }
+
+    private static long empty() {
+        return ~0L;
+    }
+
+    boolean is_empty() {
+        return entry.asLongValue() == empty();
+    }
+
+    Address to_offset() {
+        return entry.andWithMask((1L << 42) - 1);
+    }
+
+    long from_index() {
+        return entry.asLongValue() >>> 42;
+    }
+
+    public String toString() {
+        return entry + " - from_index: " + from_index() + " to_offset: " + to_offset();
+    }
+}