| /* |
| * Copyright (c) 2001, 2003, 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.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; |
| } |