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package de.lmu.ifi.dbs.elki.persistent;
/*
This file is part of ELKI:
Environment for Developing KDD-Applications Supported by Index-Structures
Copyright (C) 2011
Ludwig-Maximilians-Universität München
Lehr- und Forschungseinheit für Datenbanksysteme
ELKI Development Team
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program 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 Affero General Public License for more details.
You should have received a copy of the GNU Affero General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
import java.io.IOException;
import java.io.RandomAccessFile;
/**
* Defines the requirements for a header of a persistent page file. A header
* must at least store the size of a page in Bytes.
*
* @author Elke Achtert
*/
public interface PageHeader {
/**
* Returns the size of this header in Bytes.
*
* @return the size of this header in Bytes
*/
int size();
/**
* Initializes this header from the specified file.
*
* @param file the file to which this header belongs
* @throws IOException if an I/O-error occurs during reading
*/
void readHeader(RandomAccessFile file) throws IOException;
/**
* Initializes this header from the specified file.
*
* @param data byte array with the page data.
*/
void readHeader(byte[] data);
/**
* Writes this header to the specified file.
*
* @param file the file to which this header belongs
* @throws IOException IOException if an I/O-error occurs during writing
*/
void writeHeader(RandomAccessFile file) throws IOException;
/**
* Return the header as byte array
*
* @return header as byte array
*/
byte[] asByteArray();
/**
* Returns the size of a page in Bytes.
*
* @return the size of a page in Bytes
*/
int getPageSize();
/**
* Returns the number of pages necessary for the header
*
* @return the number of pages
*/
public int getReservedPages();
}
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