storepage.java

java 数据库 功能强大 效率高 SmallSQL Database is a free DBMS library for the Java(tm) platform. It runs on

/* =============================================================
 * SmallSQL : a free Java DBMS library for the Java(tm) platform
 * =============================================================
 *
 * (C) Copyright 2004-2006, by Volker Berlin.
 *
 * Project Info:  http://www.smallsql.de/
 *
 * This library is free software; you can redistribute it and/or modify it 
 * under the terms of the GNU Lesser General Public License as published by 
 * the Free Software Foundation; either version 2.1 of the License, or 
 * (at your option) any later version.
 *
 * This library 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 Lesser General Public 
 * License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, 
 * USA.  
 *
 * [Java is a trademark or registered trademark of Sun Microsystems, Inc. 
 * in the United States and other countries.]
 *
 * ---------------
 * StorePage.java
 * ---------------
 * Author: Volker Berlin
 * 
 * Created on 28.08.2004
 */
package smallsql.database;

import java.io.*;
import java.sql.SQLException;

/**
 * @author Volker Berlin
 */
class StorePage {
	byte[] page; // Daten einer Page
	int pageSize;
	RandomAccessFile raFile;
	long fileOffset; // Position in Datei

	StorePage(byte[] page, int pageSize, RandomAccessFile raFile, long fileOffset){
		this.page = page;
		this.pageSize = pageSize;
		this.raFile = raFile;
		this.fileOffset = fileOffset;
	}
	
	
	final void setPageData(byte[] data, int size){
		page = data;
		pageSize = size;
	}


	long commit() throws SQLException{
		try{
			if(raFile != null){
				// if new page then append at end of file
				if(fileOffset < 0){
					fileOffset = raFile.length();
				}
				raFile.seek(fileOffset);
				raFile.write(page, 0, pageSize);
				//raFile.getFD().sync();
			}
			return fileOffset;
		}catch(Exception e){
			throw Utils.createSQLException(e);
		}
	}

	
	final void rollback(){
		raFile = null;
	}
	
	void freeLock(){}
}