hotspot/agent/src/share/classes/sun/jvm/hotspot/utilities/ProgressiveHeapVisitor.java

/*
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 * 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.
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package sun.jvm.hotspot.utilities;

import sun.jvm.hotspot.memory.*;
import sun.jvm.hotspot.oops.*;

/** This class wraps a user's chosen HeapVisitor with the
    functionality that a chosen "thunk" is called periodically during
    the heap traversal. This allows a progress bar to be displayed
    during long heap scans. */

public class ProgressiveHeapVisitor implements HeapVisitor {
  private HeapVisitor userHeapVisitor;
  private HeapProgressThunk thunk;
  private long usedSize;
  private long visitedSize;
  private double lastNotificationFraction;
  private static double MINIMUM_NOTIFICATION_FRACTION = 0.01;

  public ProgressiveHeapVisitor(HeapVisitor userHeapVisitor,
                                HeapProgressThunk thunk) {
    this.userHeapVisitor = userHeapVisitor;
    this.thunk = thunk;
  }

  public void prologue(long usedSize) {
    this.usedSize = usedSize;
    visitedSize = 0;
    userHeapVisitor.prologue(usedSize);
  }

  public boolean doObj(Oop obj) {
    userHeapVisitor.doObj(obj);
    visitedSize += obj.getObjectSize();
    double curFrac = (double) visitedSize / (double) usedSize;
    if (curFrac > lastNotificationFraction + MINIMUM_NOTIFICATION_FRACTION) {
      thunk.heapIterationFractionUpdate(curFrac);
      lastNotificationFraction = curFrac;
    }
    return false;
  }

  public void epilogue() {
    userHeapVisitor.epilogue();
    thunk.heapIterationComplete();
  }
}