--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/gc/z/ZForwardingTable.java	Tue Jun 12 17:40:28 2018 +0200
@@ -0,0 +1,117 @@
+/*
+ * 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;
+import sun.jvm.hotspot.runtime.VM;
+import sun.jvm.hotspot.runtime.VMObject;
+import sun.jvm.hotspot.types.AddressField;
+import sun.jvm.hotspot.types.CIntegerField;
+import sun.jvm.hotspot.types.Type;
+import sun.jvm.hotspot.types.TypeDataBase;
+
+public class ZForwardingTable extends VMObject {
+    private static AddressField tableField;
+    private static CIntegerField sizeField;
+
+    static {
+        VM.registerVMInitializedObserver((o, d) -> initialize(VM.getVM().getTypeDataBase()));
+    }
+
+    static private synchronized void initialize(TypeDataBase db) {
+        Type type = db.lookupType("ZForwardingTable");
+
+        tableField = type.getAddressField("_table");
+        sizeField = type.getCIntegerField("_size");
+    }
+
+    public ZForwardingTable(Address addr) {
+        super(addr);
+    }
+
+    Address table() {
+        return tableField.getAddress(addr);
+    }
+
+    long size() {
+        return sizeField.getJLong(addr);
+    }
+
+    ZForwardingTableEntry at(ZForwardingTableCursor cursor) {
+        return new ZForwardingTableEntry(table().getAddressAt(cursor._value * VM.getVM().getBytesPerLong()));
+    }
+
+    ZForwardingTableEntry first(long from_index, ZForwardingTableCursor cursor) {
+        long mask = size() - 1;
+        long hash = ZHash.uint32_to_uint32(from_index);
+        cursor._value = hash & mask;
+        return at(cursor);
+    }
+
+    ZForwardingTableEntry next(ZForwardingTableCursor cursor) {
+        long mask = size() - 1;
+        cursor._value = (cursor._value + 1) & mask;
+        return at(cursor);
+    }
+
+    ZForwardingTableEntry find(long from_index, ZForwardingTableCursor cursor) {
+        // Reading entries in the table races with the atomic cas done for
+        // insertion into the table. This is safe because each entry is at
+        // most updated once (from -1 to something else).
+        ZForwardingTableEntry entry = first(from_index, cursor);
+        while (!entry.is_empty()) {
+            if (entry.from_index() == from_index) {
+                // Match found, return matching entry
+                return entry;
+            }
+
+            entry = next(cursor);
+        }
+
+        // Match not found, return empty entry
+        return entry;
+    }
+
+    ZForwardingTableEntry find(long from_index) {
+        ZForwardingTableCursor dummy = new ZForwardingTableCursor();
+        return find(from_index, dummy);
+    }
+
+    void dump() {
+        long s = size();
+        long count = 0;
+        System.out.println("Dumping ZForwardingTable[" + s + "]:");
+        ZForwardingTableCursor cursor = new ZForwardingTableCursor();
+        for (long i = 0; i < s; i++) {
+            cursor._value = i;
+            ZForwardingTableEntry entry = at(cursor);
+            if (!entry.is_empty()) {
+                long hash = ZHash.uint32_to_uint32(entry.from_index());
+                System.out.println(i + " " + count + " " + entry + " hash: " + hash + " masked_hash: " + (hash & (s - 1)));
+                count++;
+            }
+        }
+    }
+}