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Java example source code file (ThreadLocalAllocBuffer.java)

This example Java source code file (ThreadLocalAllocBuffer.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

address, addressfield, cintegerfield, observer, oophandle, threadlocalallocbuffer, type, util, vmobject

The ThreadLocalAllocBuffer.java Java example source code

/*
 * Copyright (c) 2000, 2013, 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.runtime;

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

/** <P> ThreadLocalAllocBuffer: a descriptor for thread-local storage
    used by the threads for allocation. </P>

    <P> It is thread-private at any time, but maybe multiplexed over
    time across multiple threads. </P> */

public class ThreadLocalAllocBuffer extends VMObject {
  private static AddressField  startField;
  private static AddressField  topField;
  private static AddressField  endField;
  private static CIntegerField desired_sizeField;

  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("ThreadLocalAllocBuffer");

    startField         = type.getAddressField("_start");
    topField           = type.getAddressField("_top");
    endField           = type.getAddressField("_end");
    desired_sizeField          = type.getCIntegerField("_desired_size");
  }

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

  public Address start()    { return startField.getValue(addr); }
  public Address end()      { return   endField.getValue(addr); }
  public Address top()      { return   topField.getValue(addr); }
  public Address hardEnd()  { return end().addOffsetTo(alignmentReserve()); }

  private long alignmentReserve() {
    return Oop.alignObjectSize(endReserve());
  }

  private long endReserve() {
    long minFillerArraySize = Array.baseOffsetInBytes(BasicType.T_INT);
    long reserveForAllocationPrefetch = VM.getVM().getReserveForAllocationPrefetch();
    long heapWordSize = VM.getVM().getHeapWordSize();

    return Math.max(minFillerArraySize, reserveForAllocationPrefetch * heapWordSize);
  }

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

  //  public int     size();           // FIXME: must adjust this to be in bytes
  //  public int     availableSize();  // FIXME: must adjust this to be in bytes
  public void print() {
    printOn(System.out);
  }

  public boolean contains(Address p) {
    if (top() == null) {
      return false;
    }
    return (start().lessThanOrEqual(p) && top().greaterThan(p));
  }

  public void printOn(PrintStream tty) {
    tty.println(" [" + start() + "," +
                top() + "," + end() + ",{" + hardEnd() + "})");
  }
}

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