node.java

java版b树源码

/*
 * Node.java
 *
 * Created on 2006年11月18日, 上午10:38
 *
 * To change this template, choose Tools | Template Manager
 * and open the template in the editor.
 */

package btree;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;

/**
 *  BTree的节点类
 * @author Andy
 */
public class Node {
    /**
     * 每个节点包含键数的最小值
     */
    public static final int MIN_KEY_AMOUNT=1;
    /**
     * 包含键的数量
     */
    public int numKeys;
    /**
     * 键数组
     */
    public long[] keys=new long[MIN_KEY_AMOUNT*2];
    /**
     * 值数组
     */
    public long[] valuePointers=new long[MIN_KEY_AMOUNT*2];
    /**
     * 子节点数组
     */
    public long[] childrenPointers=new long[MIN_KEY_AMOUNT*2+1];
    /**
     * 子节点本身指针
     */
    public long pointer;
    
    /**
     * 序列化节点
     * @return 返回字节流
     */
    public byte[] serialize() throws IOException{
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        DataOutputStream dos = new DataOutputStream(baos);
        //写入各Fields
        dos.writeInt(numKeys);
        for (int i = 0; i < MIN_KEY_AMOUNT*2; i++)
            dos.writeLong(keys[i]);
        for (int i = 0; i < MIN_KEY_AMOUNT*2; i++)
            dos.writeLong(valuePointers[i]);
        for (int i = 0; i < MIN_KEY_AMOUNT*2+1; i++)
            dos.writeLong(childrenPointers[i]);
        dos.writeLong(pointer);
        
        baos.close();
        dos.close();
        return baos.toByteArray();
    }
    /**
     * 反序列化
     * @param b 字节流
     * @return 节点类
     */
    public static Node deserialize(byte[] b) throws IOException{
        ByteArrayInputStream bais = new ByteArrayInputStream(b);
        DataInputStream dis = new DataInputStream(bais);
        //读取各Fields
        Node newNode=new Node();
        newNode.numKeys=dis.readInt();
        for (int i = 0; i <  MIN_KEY_AMOUNT*2; i++)
            newNode.keys[i]=dis.readLong();
        for (int i = 0; i <  MIN_KEY_AMOUNT*2; i++)
            newNode.valuePointers[i]=dis.readLong();
        for (int i = 0; i <  MIN_KEY_AMOUNT*2+1; i++)
            newNode.childrenPointers[i]=dis.readLong();
        newNode.pointer=dis.readLong();
        
        bais.close();
        dis.close();
        
        return newNode;
    }
    
    /**
     * 获取当前的秩下的节点大小。
     * @return 返回节点大小
     */
    public static int size() {
        int size= 8*MIN_KEY_AMOUNT*2*2+
                8*(MIN_KEY_AMOUNT*2+1)+
                4+8;
        return size;
    }
}