8025925: jmap fails with "field _length not found in type HeapRegionSeq"

Summary: The change JDK-7163191 changed the data layout of a class that is referenced by the java code of the SA agent. This fix synchronizes the SA agent with that change.
Reviewed-by: sla, mgerdin

agent/src/share/classes/sun/jvm/hotspot/gc_implementation/g1/G1HeapRegionTable.java

+/*
+ * Copyright (c) 2013, 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_implementation.g1;
+
+import java.util.Iterator;
+import java.util.Observable;
+import java.util.Observer;
+
+import sun.jvm.hotspot.debugger.Address;
+import sun.jvm.hotspot.runtime.VM;
+import sun.jvm.hotspot.runtime.VMObject;
+import sun.jvm.hotspot.runtime.VMObjectFactory;
+import sun.jvm.hotspot.types.AddressField;
+import sun.jvm.hotspot.types.CIntegerField;
+import sun.jvm.hotspot.types.Type;
+import sun.jvm.hotspot.types.TypeDataBase;
+
+// Mirror class for G1HeapRegionTable. It's essentially an index -> HeapRegion map.
+
+public class G1HeapRegionTable extends VMObject {
+    // HeapRegion** _base;
+    static private AddressField baseField;
+    // uint _length;
+    static private CIntegerField lengthField;
+    // HeapRegion** _biased_base
+    static private AddressField biasedBaseField;
+    // size_t _bias
+    static private CIntegerField biasField;
+    // uint _shift_by
+    static private CIntegerField shiftByField;
+
+    static {
+        VM.registerVMInitializedObserver(new Observer() {
+                public void update(Observable o, Object data) {
+                    initialize(VM.getVM().getTypeDataBase());
+                }
+            });
+    }
+
+    static private synchronized void initialize(TypeDataBase db) {
+        Type type = db.lookupType("G1HeapRegionTable");
+
+        baseField = type.getAddressField("_base");
+        lengthField = type.getCIntegerField("_length");
+        biasedBaseField = type.getAddressField("_biased_base");
+        biasField = type.getCIntegerField("_bias");
+        shiftByField = type.getCIntegerField("_shift_by");
+    }
+
+    private HeapRegion at(long index) {
+        Address arrayAddr = baseField.getValue(addr);
+        // Offset of &_base[index]
+        long offset = index * VM.getVM().getAddressSize();
+        Address regionAddr = arrayAddr.getAddressAt(offset);
+        return (HeapRegion) VMObjectFactory.newObject(HeapRegion.class,
+                                                      regionAddr);
+    }
+
+    public long length() {
+        return lengthField.getValue(addr);
+    }
+
+    public long bias() {
+        return biasField.getValue(addr);
+    }
+
+    public long shiftBy() {
+        return shiftByField.getValue(addr);
+    }
+
+    private class HeapRegionIterator implements Iterator<HeapRegion> {
+        private long index;
+        private long length;
+
+        @Override
+        public boolean hasNext() { return index < length; }
+
+        @Override
+        public HeapRegion next() { return at(index++);    }
+
+        @Override
+        public void remove()     { /* not supported */    }
+
+        HeapRegionIterator(Address addr) {
+            index = 0;
+            length = length();
+        }
+    }
+
+    public Iterator<HeapRegion> heapRegionIterator() {
+        return new HeapRegionIterator(addr);
+    }
+
+    public G1HeapRegionTable(Address addr) {
+        super(addr);
+    }
+}

agent/src/share/classes/sun/jvm/hotspot/gc_implementation/g1/HeapRegionSeq.java

 /*
- * Copyright (c) 2011, 2012, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2011, 2013, 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
@@ -37,13 +37,11 @@ import sun.jvm.hotspot.types.CIntegerField;
 import sun.jvm.hotspot.types.Type;
 import sun.jvm.hotspot.types.TypeDataBase;
 
-// Mirror class for HeapRegionSeq. It's essentially an index -> HeapRegion map.
+// Mirror class for HeapRegionSeq. It essentially encapsulates the G1HeapRegionTable.
 
 public class HeapRegionSeq extends VMObject {
-    // HeapRegion** _regions;
-    static private AddressField regionsField;
-    // uint _length;
-    static private CIntegerField lengthField;
+    // G1HeapRegionTable _regions
+    static private long regionsFieldOffset;
 
     static {
         VM.registerVMInitializedObserver(new Observer() {
@@ -56,44 +54,21 @@ public class HeapRegionSeq extends VMObject {
     static private synchronized void initialize(TypeDataBase db) {
         Type type = db.lookupType("HeapRegionSeq");
 
-        regionsField = type.getAddressField("_regions");
-        lengthField = type.getCIntegerField("_length");
+        regionsFieldOffset = type.getField("_regions").getOffset();
     }
 
-    private HeapRegion at(long index) {
-        Address arrayAddr = regionsField.getValue(addr);
-        // Offset of &_region[index]
-        long offset = index * VM.getVM().getAddressSize();
-        Address regionAddr = arrayAddr.getAddressAt(offset);
-        return (HeapRegion) VMObjectFactory.newObject(HeapRegion.class,
-                                                      regionAddr);
+    private G1HeapRegionTable regions() {
+        Address regionsAddr = addr.addOffsetTo(regionsFieldOffset);
+        return (G1HeapRegionTable) VMObjectFactory.newObject(G1HeapRegionTable.class,
+                                                             regionsAddr);
     }
 
     public long length() {
-        return lengthField.getValue(addr);
-    }
-
-    private class HeapRegionIterator implements Iterator<HeapRegion> {
-        private long index;
-        private long length;
-
-        @Override
-        public boolean hasNext() { return index < length; }
-
-        @Override
-        public HeapRegion next() { return at(index++);    }
-
-        @Override
-        public void remove()     { /* not supported */    }
-
-        HeapRegionIterator(Address addr) {
-            index = 0;
-            length = length();
-        }
+        return regions().length();
     }
 
     public Iterator<HeapRegion> heapRegionIterator() {
-        return new HeapRegionIterator(addr);
+        return regions().heapRegionIterator();
     }
 
     public HeapRegionSeq(Address addr) {