Java example source code file (Space.java)

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Java - Java tags/keywords

address, addressfield, list\/\*, memregion, observer, oophandle, space, type, util, vmobject

The Space.java Java example source code

/*
 * Copyright (c) 2000, 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.memory;

import java.io.*;
import java.util.*;
import sun.jvm.hotspot.debugger.*;
import sun.jvm.hotspot.types.*;
import sun.jvm.hotspot.runtime.*;

/** <P> A Space describes a heap area. Class Space is an abstract base
    class. </P>

    <P> Space supports allocation, size computation and GC support is
    provided. </P>

    <P> Invariant: bottom() and end() are on page_size boundaries and: 


    <P> bottom() <= top() <= end() 


    <P> top() is inclusive and end() is exclusive. 
 */

public abstract class Space extends VMObject {
  private static AddressField bottomField;
  private static AddressField endField;

  static {
    VM.registerVMInitializedObserver(new Observer() {
        public void update(Observable o, Object data) {
          initialize(VM.getVM().getTypeDataBase());
        }
      });
  }

  private static synchronized void initialize(TypeDataBase db) {
    Type type = db.lookupType("Space");

    bottomField = type.getAddressField("_bottom");
    endField    = type.getAddressField("_end");
  }

  public Space(Address addr) {
    super(addr);
  }

  public Address   bottom()       { return bottomField.getValue(addr); }
  public Address   end()          { return endField.getValue(addr);    }

  /** Returns a subregion of the space containing all the objects in
      the space. */
  public MemRegion usedRegion() {
    return new MemRegion(bottom(), end());
  }

  /** Support for iteration over heap -- not sure how this will
      interact with GC in reflective system, but necessary for the
      debugging mechanism */
  public OopHandle bottomAsOopHandle() {
    return bottomField.getOopHandle(addr);
  }

  /** Support for iteration over heap -- not sure how this will
      interact with GC in reflective system, but necessary for the
      debugging mechanism */
  public OopHandle nextOopHandle(OopHandle handle, long size) {
    return handle.addOffsetToAsOopHandle(size);
  }

  /** returns all MemRegions where live objects are */
  public abstract List/*<MemRegion>*/ getLiveRegions();

  /** Returned value is in bytes */
  public long capacity() { return end().minus(bottom()); }
  /** Returned value is in bytes */
  public abstract long used();
  /** Returned value is in bytes */
  public abstract long free();

  /** Testers */
  public boolean contains(Address p) {
    return (bottom().lessThanOrEqual(p) && end().greaterThan(p));
  }

  public void print() { printOn(System.out); }
  public void printOn(PrintStream tty) {
    tty.print(" space capacity = ");
    tty.print(capacity());
    tty.print(", ");
    tty.print((double) used() * 100.0/ capacity());
    tty.print(" used");
  }
}