001 //$HeadURL: svn+ssh://jwilden@svn.wald.intevation.org/deegree/base/branches/2.5_testing/src/org/deegree/io/rtree/PageFile.java $
002 //----------------------------------------
003 //RTree implementation.
004 //Copyright (C) 2002-2004 Wolfgang Baer - WBaer@gmx.de
005 //
006 //This library is free software; you can redistribute it and/or
007 //modify it under the terms of the GNU Lesser General Public
008 //License as published by the Free Software Foundation; either
009 //version 2.1 of the License, or (at your option) any later version.
010 //
011 //This library is distributed in the hope that it will be useful,
012 //but WITHOUT ANY WARRANTY; without even the implied warranty of
013 //MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
014 //Lesser General Public License for more details.
015 //
016 //You should have received a copy of the GNU Lesser General Public
017 //License along with this library; if not, write to the Free Software
018 //Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
019 //----------------------------------------
020
021 package org.deegree.io.rtree;
022
023 import java.io.Serializable;
024
025 /**
026 * <p>
027 * Abstract class implementing general methods of a PageFile.
028 * </p>
029 *
030 * @author Wolfgang Baer - WBaer@gmx.de
031 * @author last edited by: $Author: aschmitz $
032 *
033 * @version $Revision: 12519 $, $Date: 2008-06-25 11:37:30 +0200 (Mi, 25 Jun 2008) $
034 */
035 abstract class PageFile implements Serializable {
036
037 /** dimension of saved data */
038 protected int dimension;
039
040 /** capacity of a node (= MaxLoad + 1) */
041 protected int capacity;
042
043 /** minimum load of a node */
044 protected int minimum;
045
046 /**
047 * Returns the dimension of the PageFile
048 *
049 * @return int
050 *
051 */
052 protected int getDimension() {
053 return dimension;
054 }
055
056 /**
057 * Returns the minimum load of a node
058 *
059 * @return int
060 */
061 protected int getMinimum() {
062 return minimum;
063 }
064
065 /**
066 * Returns the capacity of a node in the PageFile. Capacity is defined a maximum load of a node
067 * plus 1 for overflow
068 *
069 * @return int
070 */
071 protected int getCapacity() {
072 return capacity;
073 }
074
075 /**
076 * Reads a node from the PageFile for given index
077 *
078 * @param pageFileNumber -
079 * index of page file number where node is saved
080 * @return Node
081 * @throws PageFileException
082 */
083 protected abstract Node readNode( int pageFileNumber )
084 throws PageFileException;
085
086 /**
087 * Writes a node into the PageFile Method tests if node has already a PageNumber, otherwise a
088 * new page number is assigned and returned.
089 *
090 * @param node -
091 * Node to write
092 * @return int - page number
093 * @throws PageFileException
094 */
095 protected abstract int writeNode( Node node )
096 throws PageFileException;
097
098 /**
099 * Marks the node at given page number as deleted.
100 *
101 * @param pageFileNumber -
102 * page number
103 * @return Node - deleted node
104 * @throws PageFileException
105 */
106 protected abstract Node deleteNode( int pageFileNumber )
107 throws PageFileException;
108
109 /**
110 * Initializes the PageFile.
111 *
112 * @param dimension -
113 * dimension of the data
114 * @param capacity -
115 * capacity of a node
116 * @throws PageFileException
117 */
118 protected void initialize( int dimension, int capacity )
119 throws PageFileException {
120 this.dimension = dimension;
121 this.capacity = capacity;
122 this.minimum = (int) Math.round( ( capacity - 1 ) * 0.5 );
123 if ( this.minimum < 2 )
124 this.minimum = 2;
125 }
126
127 /**
128 * Closes the pagefile.
129 *
130 * @throws PageFileException
131 */
132 protected abstract void close()
133 throws PageFileException;
134
135 }