cbarraylist.java

实现数据库的storage manager 功能

/*
 * Copyright (c) 2000-2004, Rickard C鰏ter, Martin Svensson
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without 
 * modification, are permitted provided that the following conditions are met:
 * 
 * Redistributions of source code must retain the above copyright notice, 
 * this list of conditions and the following disclaimer. 
 * Redistributions in binary form must reproduce the above copyright notice, 
 * this list of conditions and the following disclaimer in the documentation 
 * and/or other materials provided with the distribution. 
 * Neither the name of SICS nor the names of its contributors 
 * may be used to endorse or promote products derived from this software 
 * without specific prior written permission. 
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE 
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 
 * POSSIBILITY OF SUCH DAMAGE.
 *
 *
 */

package com.mellowtech.disc;

import java.util.ArrayList;
import java.util.Iterator;
import java.nio.*;

/**
 * A ByteStorable wrapper for an ArrayList
 *
 * @author Rickard C鰏ter
 * @version 1.0
 * @see java.util.ArrayList
 */
public class CBArrayList extends ByteStorable {

  /**
   * The internal ArrayList.
   *
   */
  protected ArrayList list = new ArrayList();

  /**
   * The name of the class type this array contains.
   *
   */
  protected CBString template = null;
  
  /**
   * Creates a new <code>CBArrayList</code> instance.
   *
   */
  public CBArrayList() {
  }
  
  /**
   * Creates a new <code>CBArrayList</code> instance.
   *
   * @param template that indicates what type of objects that is stored
   */
  public CBArrayList(ByteStorable template) {
    this.template = new CBString(template.getClass().getName());
  }
  
  /**
   * Set the template
   *
   * @param template that indicates what type of objects that is stored
   */
  public void setTemplate(ByteStorable template) {
    this.template = new CBString(template.getClass().getName());
  }
  
  /**
   * Get the internal ArrayList
   *
   * @return an <code>ArrayList</code> value
   */
  public ArrayList getArrayList() {
    return list;
  }
  
  public int byteSize() {
    int size = 8 + template.byteSize();
    for (Iterator iter = list.iterator(); iter.hasNext();) 
      size += ((ByteStorable) iter.next()).byteSize();
    return size;
  }
  
  public int byteSize(ByteBuffer bb) {
    int size = bb.getInt();
    bb.position(bb.position()-4);
    return size;
  }
  
  public void toBytes(ByteBuffer bb){
    bb.putInt(byteSize());
    bb.putInt(list.size());
    template.toBytes(bb);
    for (Iterator iter = list.iterator(); iter.hasNext();) {
      ByteStorable bs = (ByteStorable)iter.next();
      bs.toBytes(bb);
    }
  }
  
  public ByteStorable fromBytes(ByteBuffer bb) {
    CBArrayList cblist = new CBArrayList();
    int size = bb.getInt();
    int count = bb.getInt();
    cblist.template = new CBString();
    cblist.template = (CBString) cblist.template.fromBytes(bb);
    //System.out.println("In CBarraylist:frombytes\n" +
    //	       "size = " + size + " count = " + count);
    try {
      for (int i = 0; i < count; i++) {
	ByteStorable bs = (ByteStorable) 
	  Class.forName(cblist.template.toString()).newInstance();
	bs = bs.fromBytes(bb);
	//System.out.println(bs.toString());
	cblist.list.add(bs);
      }
    }
    catch(Exception e) {
      e.printStackTrace();
      return null;
    }
    return cblist;
  }
  
  
  public String toString() {
    StringBuffer sb = new StringBuffer();
    int count = 0;
    for (Iterator iter = list.iterator();iter.hasNext();) {
      sb.append(" "  + iter.next());
      count++;
    }
    return byteSize() + "\t" + count + "\t[" + sb.toString() + "]";
  }
  
  /*
  public static void main(String[] args) {
    CBArrayList cblist1 = new CBArrayList(new CBInt());
    ArrayList list = cblist1.getArrayList();
    for (int i = 0; i < 10; i++)
      list.add(new CBInt(i));
  
    ByteBuffer bb = ByteBuffer.allocate(cblist1.byteSize());
    cblist1.toBytes(bb);
    bb.flip();
    CBArrayList cblist2 = new CBArrayList();
    cblist2 = (CBArrayList) cblist2.fromBytes(bb);
    System.out.println(cblist1);
    System.out.println(cblist2);
    bb.flip();
    System.out.println(bb);
  }
  */
}