JDK14/Java14源码在线阅读

/*
 * Copyright (c) 2000, 2019, 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
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package sun.jvm.hotspot.gc.shared;

import java.io.*;
import java.util.*;

import sun.jvm.hotspot.debugger.*;
import sun.jvm.hotspot.memory.*;
import sun.jvm.hotspot.runtime.*;
import sun.jvm.hotspot.types.*;

public class ContiguousSpace extends CompactibleSpace implements LiveRegionsProvider {
  private static AddressField topField;

  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("ContiguousSpace");

    topField = type.getAddressField("_top");
  }

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

  public Address top() {
    return topField.getValue(addr);
  }

  /** In bytes */
  public long capacity() {
    return end().minus(bottom());
  }

  /** In bytes */
  public long used() {
    return top().minus(bottom());
  }

  /** In bytes */
  public long free() {
    return end().minus(top());
  }

  /** In a contiguous space we have a more obvious bound on what parts
      contain objects. */
  public MemRegion usedRegion() {
    return new MemRegion(bottom(), top());
  }

  /** Returns regions of Space where live objects live */
  public List<MemRegion> getLiveRegions() {
    List<MemRegion> res = new ArrayList<>();
    res.add(new MemRegion(bottom(), top()));
    return res;
  }


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