block.java

一个简单的数据库

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package bufferedManager;
import database.*;
import java.io.*;
import catalogManager.*;
/**
 *
 * @author outlaw
 */
public class Block{
    public static final int BLOCKSIZE=4096;
    Tuple[] tuples;  //有数据，没数据总共的tuple集合
    int blockID;
    int tupleSize; //最多可存的tuple数
    int tbID;
    String tbName;
    Holder holder;
    boolean dirty;
   
    public Block(String tbName,int id,int tupleSize)
    {
        this.tbName=tbName;
        this.blockID=id;
        this.tupleSize=tupleSize;
        tuples=new Tuple[tupleSize];
        holder=new Holder(tupleSize);
        dirty=true;
    }
    public Block(byte[] data,String tbName,int blockID) throws Exception
    {
        ByteArrayInputStream bais=new ByteArrayInputStream(data);
        DataInputStream dis=new DataInputStream(bais);
        tupleSize=dis.readInt();
        this.blockID=blockID;
        holder=new Holder(tupleSize);
        for(int i=0;i<tupleSize;i++)
        {
            boolean tag=dis.readBoolean();
            holder.getHolders()[i]=tag;
            if(tag)
                holder.setHold(i);
        }
        TableData tb=CatalogManager.getTableByName(tbName);
        this.tbName=tb.getName();
        int tupleLengthInBytes=tb.getTupleLengtInBytes();
        tuples=new Tuple[tupleSize];
        boolean[] holders=holder.getHolders();
        for(int i=0;i<tupleSize;i++)
        {
            if(holders[i])
            {
                byte[] tpByteData=new byte[tupleLengthInBytes];
                dis.read(tpByteData);
                tuples[i]=new Tuple(tpByteData,tb.getAttribTypes());                
            }
            else
            {
                dis.skip(tupleLengthInBytes);
                tuples[i]=null;
            }
        }
        dirty=false;
    }
    public void setHold(int index)
    {
        TableData tb=CatalogManager.getTableByName(tbName);
        holder.setHold(index);
        tb.incTupleNumber();
        if(holder.isFull())
        {
            tb.blockIsFull.set(blockID,true);
        }
    }
    public void setNotHold(int index)
    {
        TableData tb=CatalogManager.getTableByName(tbName);
        holder.setNotHold(index);
        tb.decTupleNumber();
        if(!holder.isFull())
        {
            tb.blockIsFull.set(blockID,false); 
        }
    }
    public boolean isHold(int index)
    {
        return holder.isHold(index);
    }
    public boolean isFull()
    {
        return holder.isFull();
    }
    public int[] getAvailablePos()
    {
        return holder.getAvailablePos();
    }
    public int getFirstAvailablePos()
    {
        return holder.getFirstAvailablePos();
    }
    public String getTBName()
    {
        return tbName;
    }
    public int getBlockID()
    {
        return blockID;
    }
    public byte[] toBytes() throws Exception
    {
        ByteArrayOutputStream baos=new ByteArrayOutputStream();
        DataOutputStream dos=new DataOutputStream(baos);
        dos.writeInt(tupleSize);
        boolean[] holders=holder.getHolders();
        for(int i=0;i<holders.length;i++)
        {
            dos.writeBoolean(holders[i]);
        }
        for(int i=0;i<tupleSize;i++)
        {
            if(tuples[i]!=null)
                dos.write(tuples[i].toBytes(CatalogManager.getTableByName(tbName).getAttribTypes()));
            else
            {
                int len=CatalogManager.getTableByName(tbName).getTupleLengtInBytes();
                for(int j=0;j<len;j++)
                    dos.writeByte(0);
            }
        }
        return baos.toByteArray();
    }
    public int addTuple(Tuple tp) throws Exception
    {
        if(isFull())
            throw new OperationInfo("The block"+blockID+"is already full!");
        int index=getFirstAvailablePos();
        tuples[index]=tp;
        holder.setHold(index);
        return index;
    }
    public int[] getNotAvailablePos()
    {
        return holder.getNotAvailablePos();
    }
    public Tuple[] getTuples()
    {
        return tuples;
    }
    public boolean isDirty()
    {
        return dirty;
    }
    public void setDirty()
    {
        dirty=true;
    }
    public int getTupeNumber()
    {
        return this.tupleSize;
    }
}