//
//RTree implementation.
//Copyright (C) 2002-2004 Wolfgang Baer - WBaer@gmx.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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

package org.deegree.io.rtree;

import java.io.Serializable;



/**
* <p>
* Abstract class implementing general methods of a PageFile.
* </p>
* @author Wolfgang Baer - WBaer@gmx.de
*/
abstract class PageFile implements Serializable {
	
	/** dimension of saved data */
	protected int dimension;
	/** capacity of a node (= MaxLoad + 1) */
	protected int capacity;
	/** minimum load of a node*/
	protected int minimum;

    /**
     * Returns the dimension of the PageFile
     * @return int
     * 
     */
    protected int getDimension() {
        return dimension;
    }

    /**
     * Returns the minimum load of a node
     * @return int
     */
    protected int getMinimum() {
        return minimum;
    }

    /**
     * Returns the capacity of a node in the PageFile.
     * Capacity is defined a maximum load of a node plus 1 for overflow
     * @return int
     */
    protected int getCapacity() {
        return capacity;
    }

	
	/**
	 * Reads a node from the PageFile for given index
	 * @param int - index of page file number where node is saved
	 * @return Node
	 * @throws PageFileException
	 */
	protected abstract Node readNode(int pageFileNumber) throws PageFileException ;
	
	/**
	 * Writes a node into the PageFile
	 * Method tests if node has already a PageNumber, otherwise
	 * a new page number is assigned and returned.
	 * @param node - Node to write
	 * @return int - page number
	 * @throws PageFileException
	 */
	protected abstract int writeNode(Node node) throws PageFileException ;
	
	/**
	 * Marks the node at given page number as deleted.
	 * @param int - page number
	 * @return Node - deleted node
	 */
	protected abstract Node deleteNode(int pageFileNumber) throws PageFileException;
	
	/**
	 * Initializes the PageFile.
	 * @param dimension - dimension of the data
	 * @param capacity - capacity of a node
	 * @throws PageFileException
	 */
	protected void initialize(int dimension, int capacity)  throws PageFileException {
		this.dimension = dimension;
		this.capacity = capacity;
		this.minimum = (int)Math.round((capacity -1) * 0.5);
		if(this.minimum < 2)
			this.minimum = 2;
	}
	
	/**
	 * Closes the pagefile.
	 */
	protected abstract void close() throws PageFileException;

}
/* ********************************************************************
Changes to this class. What the people have been up to:
$Log: PageFile.java,v $
Revision 1.6  2006/08/08 09:07:29  poth
*** empty log message ***

Revision 1.5  2006/07/12 14:46:17  poth
comment footer added

********************************************************************** */