--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/agent/src/share/classes/sun/jvm/hotspot/utilities/MarkBits.java	Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,93 @@
+/*
+ * Copyright 2001-2003 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;
+
+import sun.jvm.hotspot.debugger.*;
+import sun.jvm.hotspot.gc_interface.*;
+import sun.jvm.hotspot.memory.*;
+import sun.jvm.hotspot.oops.*;
+import sun.jvm.hotspot.runtime.*;
+
+/** Helper class which covers the reserved area of the heap with an
+    (object-external) set of mark bits, used for GC-like scans through
+    the heap like liveness analysis. */
+
+public class MarkBits {
+  public MarkBits(CollectedHeap heap) {
+    MemRegion reserved = heap.reservedRegion();
+    // Must cover "reserved" with one bit for each OopHandle
+    start = reserved.start();
+    end   = reserved.end();
+    long numOopHandles = end.minus(start) / VM.getVM().getOopSize();
+    // FIXME: will have trouble with larger heap sizes
+    bits = new BitMap((int) numOopHandles);
+  }
+
+  public void clear() {
+    bits.clear();
+  }
+
+  /** Returns true if a mark was newly placed for the given Oop, or
+      false if the Oop was already marked. If the Oop happens to lie
+      outside the heap (should not happen), prints a warning and
+      returns false. */
+  public boolean mark(Oop obj) {
+    if (obj == null) {
+      System.err.println("MarkBits: WARNING: null object, ignoring");
+      return false;
+    }
+
+    OopHandle handle = obj.getHandle();
+    // FIXME: will have trouble with larger heap sizes
+    long idx = handle.minus(start) / VM.getVM().getOopSize();
+    if ((idx < 0) || (idx >= bits.size())) {
+      System.err.println("MarkBits: WARNING: object " + handle + " outside of heap, ignoring");
+      return false;
+    }
+    int intIdx = (int) idx;
+    if (bits.at(intIdx)) {
+      return false; // already marked
+    }
+    bits.atPut(intIdx, true);
+    return true;
+  }
+
+  /** Forces clearing of a given mark bit. */
+  public void clear(Oop obj) {
+    OopHandle handle = obj.getHandle();
+    // FIXME: will have trouble with larger heap sizes
+    long idx = handle.minus(start) / VM.getVM().getOopSize();
+    if ((idx < 0) || (idx >= bits.size())) {
+      System.err.println("MarkBits: WARNING: object " + handle + " outside of heap, ignoring");
+      return;
+    }
+    int intIdx = (int) idx;
+    bits.atPut(intIdx, false);
+  }
+
+  private BitMap  bits;
+  private Address start;
+  private Address end;
+}