/* XXL: The eXtensible and fleXible Library for data processing

Copyright (C) 2000-2011 Prof. Dr. Bernhard Seeger
                        Head of the Database Research Group
                        Department of Mathematics and Computer Science
                        University of Marburg
                        Germany

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 3 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, see <http://www.gnu.org/licenses/>. 

    http://code.google.com/p/xxl/

*/

package xxl.core.io.raw;

/**
 * Allows user defined partitioning of a raw access. An object
 * of this class represents a consecutive part of a (usually) larger 
 * raw access.
 */
public class PartitionRawAccess implements RawAccess {
	/**
	 * Internally used raw access.
	 */
	private RawAccess ra;
	
	/**
	 * First sector of the raw access inside the raw access it is based on.
	 */
	private long startSector;
	
	/**
	 * Size of the raw access.
	 */
	private long size;
	
	/**
	 * Constructs a partition (raw access) inside a raw access.
	 * The partition has the same sector size with the base raw
	 * access.
	 * 
	 * @param ra base raw access
	 * @param startSector number of the start sector
	 * @param size size of the created partition in sectors
	 */
	public PartitionRawAccess (RawAccess ra, long startSector, long size) {
		this.ra = ra;
		this.startSector = startSector;
		this.size = size;
	}
	
	/**
	 * Opens the raw access (the base raw access already has to be open).
	 *
	 * @param filename name of the file (is not needed here).
 	 * @throws RawAccessException
	 */
	public void open(String filename) throws RawAccessException {
	}
	
	/**
	 * Close the raw access.
 	 * @throws RawAccessException
	 */
	public void close() throws RawAccessException {
	}
	
	/**
	 * Writes a block into the partition.
	 *
	 * @param block byte array of which will be written to the sector
	 * @param sector number of the sector in the file/device from where the block will be read
	 * @exception RawAccessException a specialized RuntimeException
	 */
	public void write(byte[] block, long sector) {
		if ((sector<0) || (sector>=size))
			throw new RawAccessException("Attempt to write outside boundary ("+sector+", size of the Partition:"+size+", startSector of the Partition:"+startSector+")");
		ra.write(block, startSector+sector);
	}
	
	/**
	 * Reads a block from the partition.
	 *
	 * @param block byte array of which will be written to the sector
	 * @param sector number of the sector in the file/device from where the block will be read
	 * @exception RawAccessException a specialized RuntimeException
	 */
	public void read(byte[] block, long sector) throws RawAccessException {
		if ((sector<0) || (sector>=size))
			throw new RawAccessException("Attempt to read outside boundary ("+sector+", length:"+size+", startSector="+startSector+")");
		ra.read(block, startSector+sector);
	}
	
	/**
	 * Returns the size of the partition in sectors.
	 *
	 * @return amount of sectors
	 */
	public long getNumSectors() {
		return size;
	}
	
	/**
	 * Returns the size of each sector (is the same with the sector size of the
	 * base raw access).
	 *
	 * @return size of sectors
	 */
	public int getSectorSize() {
		return ra.getSectorSize();
	}

	/**
	 * Outputs a String representation of the raw device.
	 * @return A String representation.
	 */
	public String toString()  {
		return "Partition raw access of: "+ra;
	}
}