blobpageimpl.java

用Java写的面相对象的数据库管理系统

// You can redistribute this software and/or modify it under the terms of
// the Ozone Library License version 1 published by ozone-db.org.
//
// The original code and portions created by SMB are
// Copyright (C) 1997-2000 by SMB GmbH. All rights reserved.
//
// $Id: BLOBPageImpl.java,v 1.3 2000/10/28 16:55:16 daniela Exp $

package org.ozoneDB.blob;

import org.ozoneDB.*;
import java.io.*;


/**
 * One page of an ozone BLOB.
 * 
 * 
 * @author <a href="http://www.softwarebuero.de/">SMB</a>
 * @version $Revision: 1.3 $Date: 2000/10/28 16:55:16 $
 */
public class BLOBPageImpl extends OzoneObject implements BLOBPage {
    
    byte[] data;
    int space;
    int size;
    
    
    public BLOBPageImpl() {
    }
    
    
    public void init( int _space ) {
        space = _space;
        data = new byte[space];
        size = 0;
    } 
    
    
    public int size() {
        return size;
    } 
    
    
    /** */
    public void write( byte[] b, int off ) {
        if (off == 0 && b.length == space) {
            data = b;
            size = space;
        } else {
            int len = b.length;
            // calculate the real length: 0 <= len <= (space-off)
            len = Math.max( Math.min( space - off, len ), 0 );
            
            System.arraycopy( b, 0, data, off, len );
            size = off + len;
        } 
    } 
    
    
    /** */
    public byte[] read( int off, int len ) {
        // calculate the real length: 0 <= len <= (size-off)
        len = Math.max( Math.min( size - off, len ), 0 );
        
        byte[] result = new byte[len];
        System.arraycopy( data, off, result, 0, len );
        
        //////////////////////////////////////////////////////
        //System.out.println ("return an array with length "+result.length);
        
        return result;
    } 
    
}