src/main/java/org/eclipse/mdm/mdfsorter/mdf3/MDF3ProcessWriter.java - mdmbl/org.eclipse.mdm.mdfsorter - Git at Google

 /*
  * Copyright (c) 2016 Audi AG
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  */

 package org.eclipse.mdm.mdfsorter.mdf3;

 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.RandomAccessFile;
 import java.nio.ByteBuffer;
 import java.nio.channels.FileChannel;
 import java.util.HashMap;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
 import java.util.logging.Level;
 import java.util.zip.DataFormatException;

 import org.eclipse.mdm.mdfsorter.AbstractDataProvider;
 import org.eclipse.mdm.mdfsorter.ArgumentStruct;
 import org.eclipse.mdm.mdfsorter.DataBlockBuffer;
 import org.eclipse.mdm.mdfsorter.MDFAbstractProcessWriter;
 import org.eclipse.mdm.mdfsorter.MDFCompatibilityProblem;
 import org.eclipse.mdm.mdfsorter.MDFFileContent;
 import org.eclipse.mdm.mdfsorter.MDFProblemType;
 import org.eclipse.mdm.mdfsorter.MDFSorter;
 import org.eclipse.mdm.mdfsorter.WriteDataCache;
 import org.eclipse.mdm.mdfsorter.WriteWorker;
 import org.eclipse.mdm.mdfsorter.mdf4.MDF4Util;

 /**
  * Main Class for processing and writing of the output.
  *
  * @author Tobias Leemann
  *
  */
 public class MDF3ProcessWriter extends MDFAbstractProcessWriter<MDF3GenBlock> {

 	/**
 	 * Main Constructor.
 	 *
 	 * @param filestructure
 	 *            The result of parsing the MDF-File (MDFParser)
 	 * @param args
 	 *            The arguments of this programm call.
 	 */
 	public MDF3ProcessWriter(MDFFileContent<MDF3GenBlock> filestructure,
 			ArgumentStruct args) {
 		this.filestructure = filestructure;
 		this.args = args;
 		writtenblocks = new LinkedList<MDF3GenBlock>();
 	}

 	private int numberOfDatagroups = 0;

 	/**
 	 * Main Function of this class.
 	 *
 	 * @throws IOException
 	 *             If any I/O-Problems are encountered.
 	 * @throws DataFormatException
 	 *             If the data of any DZ-Blocks is not in a readable format.
 	 */
 	@Override
 	public void processAndWriteOut() throws IOException, DataFormatException {

 		// 1. Analyse situation
 		checkProblems();

 		// A data groups will be created for each channel, count channels!
 		for (MDF3GenBlock blk : filestructure.getList()) {
 			if (blk instanceof CGBLOCK) {
 				numberOfDatagroups++;
 			}
 		}
 		// Check if zip flag is not set
 		if (!args.unzip) {
 			throw new IllegalArgumentException(
 					"MDF3.x Files mustn't be zipped!");
 		}

 		// Open outputfile
 		FileOutputStream out = new FileOutputStream(args.outputname);

 		long start; Thread t; //Start time will be stored here later.

 		try(DataBlockBuffer buf = new DataBlockBuffer()){
 			//automatically stop writer thread if exeptions occur (Writer Thread is stopped vie the DataBlock Buffer.

 			myCache = new WriteDataCache(buf);

 			// Start writer Thread
 			start = System.currentTimeMillis();
 			t = new Thread(new WriteWorker(out, buf));
 			t.start();

 			// write out blocks
 			FileChannel reader = filestructure.getInput();
 			reader.position(0L);
 			// reader = filestructure.getIn();

 			// write header block first
 			ByteBuffer headerbuf = ByteBuffer.allocate(MDF4Util.headersize);
 			reader.read(headerbuf);

 			// If Data has to be zipped, the file version has be set to at least

 			performPut(headerbuf, headerbuf.capacity(), false);

 			for (MDF3GenBlock blk : filestructure.getList()) {
 				// copy block if untouched and no problem block
 				if (!blk.gettouched() && blk.getProblems() == null) {
 					if (blk instanceof HDBLOCK) {
 						((HDBLOCK) blk).setNumberOfDataGroups(numberOfDatagroups);
 						writeBlock(blk, null);
 					} else {
 						copyBlock(blk, reader);
 					}

 				} else {
 					if (blk.getProblems() != null) {
 						for (MDFCompatibilityProblem p : blk.getProblems()) {
 							MDFSorter.log.log(Level.FINE,
 									"Problem of Type: " + p.getType());
 						}
 						solveProblem(blk.getProblems());
 					} else {
 						// Do nothing if block is part of a bigger Problem.
 						// The Block will be written if the "head block" of the
 						// Problem is processed.
 					}
 				}
 			}

 			// Flush Cache
 			myCache.flush();
 		}
 		//Wait for completion of write operation.
 		try {
 			t.join();
 		} catch (InterruptedException e) {
 			e.printStackTrace();
 		}
 		//Close output stream.
 		out.close();

 		MDFSorter.log.log(Level.INFO, "Wrote " + writeptr / 1000 + " kB.");
 		MDFSorter.log.log(Level.INFO,
 				"Writing took " + (System.currentTimeMillis() - start) + " ms");

 		// Update links with RandomAccessFile
 		RandomAccessFile r = new RandomAccessFile(args.outputname, "rw");
 		for (MDF3GenBlock blk : writtenblocks) {
 			blk.updateLinks(r);
 		}
 		r.close();
 		MDFSorter.log.log(Level.INFO, "Links updated successfully.");
 	}

 	/**
 	 * Main sorting function.
 	 *
 	 * @param l
 	 *            list of problems, one specific node has.
 	 * @throws IOException
 	 *             If an I/O error occurs.
 	 * @throws DataFormatException
 	 *             If zipped Data is in an invalid format
 	 */
 	public void solveProblem(List<MDFCompatibilityProblem> l)
 			throws IOException, DataFormatException {
 		if (l.size() != 1) {
 			System.out.println("To many Problems.");
 			// This may be supported in later versions.
 			return;
 		} else {
 			MDFCompatibilityProblem prob = l.get(0);
 			MDFProblemType probtype = prob.getType();
 			MDF3GenBlock node = (MDF3GenBlock) prob.getStartnode();
 			if (probtype == MDFProblemType.UNSORTED_DATA_PROBLEM) {
 				// Refactor Channel Group!
 				// We have more than one channel group in a single
 				// DataGroup. We have to create new DataGroups for each
 				// Channel Group.
 				LinkedList<CGBLOCK> groups = getChannelGroupsfromDataGroup(
 						(DGBLOCK) node);
 				MDFSorter.log.log(Level.INFO,
 						"Found " + groups.size() + " Channel Groups in DG.");
 				MDF3GenBlock datasection = ((DGBLOCK) node).getLnkData();
 				SortDataGroup(prob, groups, datasection);

 			} else {
 				// Other Problems supported later.
 			}
 			return;
 		}
 	}

 	public LinkedList<CGBLOCK> getChannelGroupsfromDataGroup(
 			DGBLOCK startDataGroup) {
 		LinkedList<CGBLOCK> ret = new LinkedList<CGBLOCK>();
 		CGBLOCK next = (CGBLOCK) startDataGroup.getLnkCgFirst();
 		while (next != null) {
 			ret.add(next);
 			next = (CGBLOCK) next.getLnkCgNext();
 		}
 		return ret;
 	}

 	public void SortDataGroup(MDFCompatibilityProblem prob,
 			LinkedList<CGBLOCK> groups, MDF3GenBlock datasection)
 					throws IOException, DataFormatException {

 		DGBLOCK datagroup = (DGBLOCK) prob.getStartnode();
 		// sort records.
 		MDF3DataProvider prov = new MDF3DataProvider(datasection,
 				filestructure.getInput());

 		int idSize = 1;

 		// ids at the end of the record.
 		boolean redundantids = false;
 		if (datagroup.getNumOfRecId() == 2) {
 			redundantids = true;
 		}

 		int i = 0;
 		Map<Integer, Integer> recNumtoArrIdx = new HashMap<Integer, Integer>();
 		Map<Integer, Integer> recNumtoSize = new HashMap<Integer, Integer>();

 		long[] recCounters = new long[groups.size()];

 		for (CGBLOCK cgroup : groups) {

 			//Loop through records, and initialize variables
 			recCounters[i] = cgroup.getCycleCount();
 			int recID = cgroup.getRecordId();
 			recNumtoArrIdx.put(recID, i++);
 			recNumtoSize.put(recID, cgroup.getDataBytes());
 		}

 		long[][] startaddresses = fillRecordArray(recCounters, recNumtoArrIdx, recNumtoSize, prov, redundantids);

 		MDF3GenBlock last = (MDF3GenBlock) prob.getParentnode();

 		// write new blocks
 		for (CGBLOCK cgroup : groups) {
 			int arridx = recNumtoArrIdx.get(cgroup.getRecordId());
 			MDFSorter.log.fine("Writing data for Block " + arridx + ".");
 			long newlength;
 			// create new datagroup
 			last = copyChannelInfrastructure(last, cgroup);
 			long reclen = cgroup.getDataBytes();
 			newlength = cgroup.getCycleCount() * cgroup.getDataBytes();
 			MDF3BlocksSplittMerger splitmerger = new MDF3BlocksSplittMerger(
 					this, last, newlength, prov);

 			// write data sections.
 			for (long l : startaddresses[arridx]) {
 				splitmerger.splitmerge(l + idSize, reclen);
 			}
 			splitmerger.setLinks();
 		}
 	}


 	public long[][] fillRecordArray(long[] recordCounters, Map<Integer, Integer> recNumtoArrIdx, Map<Integer,
 			Integer> recNumtoSize, AbstractDataProvider prov, boolean redundantids) throws IOException, DataFormatException{

 		MDFSorter.log.info("Searching Records.");

 		long[][] startaddresses = new long[recordCounters.length][];
 		int idSize = 1;

 		//initilize array.
 		int counter =0;
 		long totalRecords = 0; //total number of records
 		for(long i : recordCounters){
 			totalRecords+=i;
 			startaddresses[counter++] = new long[(int) i];
 		}

 		int[] foundrecCounters = new int[recordCounters.length];

 		long sectionoffset = 0; //our position in the data section
 		long foundrecords = 0; //number of records we found

 		ByteBuffer databuf;
 		while (foundrecords < totalRecords) {
 			// Read Group number
 			databuf = prov.cachedRead(sectionoffset, idSize);
 			int foundID = MDF3Util.readUInt8(databuf);
 			Integer foundsize = recNumtoSize.get(foundID);
 			if(foundsize == null){ //Check if a size was found.
 				throw new RuntimeException("No Size known for record ID "+ foundID+ ".");
 			}
 			if (redundantids) {
 				// do a sanity check with the second id
 				databuf = prov.cachedRead(sectionoffset, idSize + foundsize);
 				int endID = MDF3Util.readUInt8(databuf);
 				if (endID != foundID) {
 					MDFSorter.log.warning("Found ID " + foundID
 							+ " at start of records, but ID " + endID
 							+ " at its end.");
 				}
 			}
 			Integer arridx = recNumtoArrIdx.get(foundID);
 			if(arridx == null){ //Check if an entry was found.
 				throw new RuntimeException("Record ID "+ foundID+ " is not known.");
 			}
 			startaddresses[arridx][foundrecCounters[arridx]++] = sectionoffset; // remember
 			// start
 			// of records
 			// Normal-Channel
 			sectionoffset = sectionoffset + foundsize + idSize;

 			// Skip id after record
 			if (redundantids) {
 				sectionoffset += 1;
 			}
 			foundrecords++;
 		}
 		MDFSorter.log.fine("Found " + foundrecords + " Records.");
 		return startaddresses;
 	}

 	public DGBLOCK copyChannelInfrastructure(MDF3GenBlock last, CGBLOCK towrite)
 			throws IOException {
 		// Create new Data Group with default values, and write to file.
 		DGBLOCK newdg = new DGBLOCK(filestructure.isBigEndian());
 		newdg.setChannelGroups(1);
 		writeBlock(newdg, null);
 		// set link to next DGblock.
 		last.setLink(0, newdg);
 		// set link to child CGblock.
 		newdg.setLink(1, towrite);

 		// Modify and write old channel group.
 		// No other channel.
 		towrite.setLink(0, null);
 		towrite.setRecordId(0);
 		writeBlock(towrite, null);
 		return newdg;
 	}

 	/**
 	 * Creates and writes the header of a DataBlock (any Block without links)
 	 *
 	 * @param size
 	 *            Size of this block's Data section (length is set to size +24
 	 *            Bytes for header fields.
 	 * @return The MDFBlock Object, which was created.
 	 */
 	public DTBLOCK create(long size) {
 		DTBLOCK ret;
 		ret = new DTBLOCK(filestructure.isBigEndian());
 		ret.setLength(size);
 		ret.setLinkCount(0);
 		ret.setOutputpos(writeptr);
 		writtenblocks.add(ret);
 		return ret;
 	}

 	@Override
 	public void writeSpacer(long length) {
 		// Do nothing in MDF3
 	}

 }
	/*
	* Copyright (c) 2016 Audi AG
	* All rights reserved. This program and the accompanying materials
	* are made available under the terms of the Eclipse Public License v1.0
	* which accompanies this distribution, and is available at
	* http://www.eclipse.org/legal/epl-v10.html
	*/

	package org.eclipse.mdm.mdfsorter.mdf3;

	import java.io.FileOutputStream;
	import java.io.IOException;
	import java.io.RandomAccessFile;
	import java.nio.ByteBuffer;
	import java.nio.channels.FileChannel;
	import java.util.HashMap;
	import java.util.LinkedList;
	import java.util.List;
	import java.util.Map;
	import java.util.logging.Level;
	import java.util.zip.DataFormatException;

	import org.eclipse.mdm.mdfsorter.AbstractDataProvider;
	import org.eclipse.mdm.mdfsorter.ArgumentStruct;
	import org.eclipse.mdm.mdfsorter.DataBlockBuffer;
	import org.eclipse.mdm.mdfsorter.MDFAbstractProcessWriter;
	import org.eclipse.mdm.mdfsorter.MDFCompatibilityProblem;
	import org.eclipse.mdm.mdfsorter.MDFFileContent;
	import org.eclipse.mdm.mdfsorter.MDFProblemType;
	import org.eclipse.mdm.mdfsorter.MDFSorter;
	import org.eclipse.mdm.mdfsorter.WriteDataCache;
	import org.eclipse.mdm.mdfsorter.WriteWorker;
	import org.eclipse.mdm.mdfsorter.mdf4.MDF4Util;

	/**
	* Main Class for processing and writing of the output.
	*
	* @author Tobias Leemann
	*
	*/
	public class MDF3ProcessWriter extends MDFAbstractProcessWriter<MDF3GenBlock> {

	/**
	* Main Constructor.
	*
	* @param filestructure
	* The result of parsing the MDF-File (MDFParser)
	* @param args
	* The arguments of this programm call.
	*/
	public MDF3ProcessWriter(MDFFileContent<MDF3GenBlock> filestructure,
	ArgumentStruct args) {
	this.filestructure = filestructure;
	this.args = args;
	writtenblocks = new LinkedList<MDF3GenBlock>();
	}

	private int numberOfDatagroups = 0;

	/**
	* Main Function of this class.
	*
	* @throws IOException
	* If any I/O-Problems are encountered.
	* @throws DataFormatException
	* If the data of any DZ-Blocks is not in a readable format.
	*/
	@Override
	public void processAndWriteOut() throws IOException, DataFormatException {

	// 1. Analyse situation
	checkProblems();

	// A data groups will be created for each channel, count channels!
	for (MDF3GenBlock blk : filestructure.getList()) {
	if (blk instanceof CGBLOCK) {
	numberOfDatagroups++;
	}
	}
	// Check if zip flag is not set
	if (!args.unzip) {
	throw new IllegalArgumentException(
	"MDF3.x Files mustn't be zipped!");
	}

	// Open outputfile
	FileOutputStream out = new FileOutputStream(args.outputname);

	long start; Thread t; //Start time will be stored here later.

	try(DataBlockBuffer buf = new DataBlockBuffer()){
	//automatically stop writer thread if exeptions occur (Writer Thread is stopped vie the DataBlock Buffer.

	myCache = new WriteDataCache(buf);

	// Start writer Thread
	start = System.currentTimeMillis();
	t = new Thread(new WriteWorker(out, buf));
	t.start();

	// write out blocks
	FileChannel reader = filestructure.getInput();
	reader.position(0L);
	// reader = filestructure.getIn();

	// write header block first
	ByteBuffer headerbuf = ByteBuffer.allocate(MDF4Util.headersize);
	reader.read(headerbuf);

	// If Data has to be zipped, the file version has be set to at least

	performPut(headerbuf, headerbuf.capacity(), false);

	for (MDF3GenBlock blk : filestructure.getList()) {
	// copy block if untouched and no problem block
	if (!blk.gettouched() && blk.getProblems() == null) {
	if (blk instanceof HDBLOCK) {
	((HDBLOCK) blk).setNumberOfDataGroups(numberOfDatagroups);
	writeBlock(blk, null);
	} else {
	copyBlock(blk, reader);
	}

	} else {
	if (blk.getProblems() != null) {
	for (MDFCompatibilityProblem p : blk.getProblems()) {
	MDFSorter.log.log(Level.FINE,
	"Problem of Type: " + p.getType());
	}
	solveProblem(blk.getProblems());
	} else {
	// Do nothing if block is part of a bigger Problem.
	// The Block will be written if the "head block" of the
	// Problem is processed.
	}
	}
	}

	// Flush Cache
	myCache.flush();
	}
	//Wait for completion of write operation.
	try {
	t.join();
	} catch (InterruptedException e) {
	e.printStackTrace();
	}
	//Close output stream.
	out.close();

	MDFSorter.log.log(Level.INFO, "Wrote " + writeptr / 1000 + " kB.");
	MDFSorter.log.log(Level.INFO,
	"Writing took " + (System.currentTimeMillis() - start) + " ms");

	// Update links with RandomAccessFile
	RandomAccessFile r = new RandomAccessFile(args.outputname, "rw");
	for (MDF3GenBlock blk : writtenblocks) {
	blk.updateLinks(r);
	}
	r.close();
	MDFSorter.log.log(Level.INFO, "Links updated successfully.");
	}

	/**
	* Main sorting function.
	*
	* @param l
	* list of problems, one specific node has.
	* @throws IOException
	* If an I/O error occurs.
	* @throws DataFormatException
	* If zipped Data is in an invalid format
	*/
	public void solveProblem(List<MDFCompatibilityProblem> l)
	throws IOException, DataFormatException {
	if (l.size() != 1) {
	System.out.println("To many Problems.");
	// This may be supported in later versions.
	return;
	} else {
	MDFCompatibilityProblem prob = l.get(0);
	MDFProblemType probtype = prob.getType();
	MDF3GenBlock node = (MDF3GenBlock) prob.getStartnode();
	if (probtype == MDFProblemType.UNSORTED_DATA_PROBLEM) {
	// Refactor Channel Group!
	// We have more than one channel group in a single
	// DataGroup. We have to create new DataGroups for each
	// Channel Group.
	LinkedList<CGBLOCK> groups = getChannelGroupsfromDataGroup(
	(DGBLOCK) node);
	MDFSorter.log.log(Level.INFO,
	"Found " + groups.size() + " Channel Groups in DG.");
	MDF3GenBlock datasection = ((DGBLOCK) node).getLnkData();
	SortDataGroup(prob, groups, datasection);

	} else {
	// Other Problems supported later.
	}
	return;
	}
	}

	public LinkedList<CGBLOCK> getChannelGroupsfromDataGroup(
	DGBLOCK startDataGroup) {
	LinkedList<CGBLOCK> ret = new LinkedList<CGBLOCK>();
	CGBLOCK next = (CGBLOCK) startDataGroup.getLnkCgFirst();
	while (next != null) {
	ret.add(next);
	next = (CGBLOCK) next.getLnkCgNext();
	}
	return ret;
	}

	public void SortDataGroup(MDFCompatibilityProblem prob,
	LinkedList<CGBLOCK> groups, MDF3GenBlock datasection)
	throws IOException, DataFormatException {

	DGBLOCK datagroup = (DGBLOCK) prob.getStartnode();
	// sort records.
	MDF3DataProvider prov = new MDF3DataProvider(datasection,
	filestructure.getInput());

	int idSize = 1;

	// ids at the end of the record.
	boolean redundantids = false;
	if (datagroup.getNumOfRecId() == 2) {
	redundantids = true;
	}

	int i = 0;
	Map<Integer, Integer> recNumtoArrIdx = new HashMap<Integer, Integer>();
	Map<Integer, Integer> recNumtoSize = new HashMap<Integer, Integer>();

	long[] recCounters = new long[groups.size()];

	for (CGBLOCK cgroup : groups) {

	//Loop through records, and initialize variables
	recCounters[i] = cgroup.getCycleCount();
	int recID = cgroup.getRecordId();
	recNumtoArrIdx.put(recID, i++);
	recNumtoSize.put(recID, cgroup.getDataBytes());
	}

	long[][] startaddresses = fillRecordArray(recCounters, recNumtoArrIdx, recNumtoSize, prov, redundantids);

	MDF3GenBlock last = (MDF3GenBlock) prob.getParentnode();

	// write new blocks
	for (CGBLOCK cgroup : groups) {
	int arridx = recNumtoArrIdx.get(cgroup.getRecordId());
	MDFSorter.log.fine("Writing data for Block " + arridx + ".");
	long newlength;
	// create new datagroup
	last = copyChannelInfrastructure(last, cgroup);
	long reclen = cgroup.getDataBytes();
	newlength = cgroup.getCycleCount() * cgroup.getDataBytes();
	MDF3BlocksSplittMerger splitmerger = new MDF3BlocksSplittMerger(
	this, last, newlength, prov);

	// write data sections.
	for (long l : startaddresses[arridx]) {
	splitmerger.splitmerge(l + idSize, reclen);
	}
	splitmerger.setLinks();
	}
	}


	public long[][] fillRecordArray(long[] recordCounters, Map<Integer, Integer> recNumtoArrIdx, Map<Integer,
	Integer> recNumtoSize, AbstractDataProvider prov, boolean redundantids) throws IOException, DataFormatException{

	MDFSorter.log.info("Searching Records.");

	long[][] startaddresses = new long[recordCounters.length][];
	int idSize = 1;

	//initilize array.
	int counter =0;
	long totalRecords = 0; //total number of records
	for(long i : recordCounters){
	totalRecords+=i;
	startaddresses[counter++] = new long[(int) i];
	}

	int[] foundrecCounters = new int[recordCounters.length];

	long sectionoffset = 0; //our position in the data section
	long foundrecords = 0; //number of records we found

	ByteBuffer databuf;
	while (foundrecords < totalRecords) {
	// Read Group number
	databuf = prov.cachedRead(sectionoffset, idSize);
	int foundID = MDF3Util.readUInt8(databuf);
	Integer foundsize = recNumtoSize.get(foundID);
	if(foundsize == null){ //Check if a size was found.
	throw new RuntimeException("No Size known for record ID "+ foundID+ ".");
	}
	if (redundantids) {
	// do a sanity check with the second id
	databuf = prov.cachedRead(sectionoffset, idSize + foundsize);
	int endID = MDF3Util.readUInt8(databuf);
	if (endID != foundID) {
	MDFSorter.log.warning("Found ID " + foundID
	+ " at start of records, but ID " + endID
	+ " at its end.");
	}
	}
	Integer arridx = recNumtoArrIdx.get(foundID);
	if(arridx == null){ //Check if an entry was found.
	throw new RuntimeException("Record ID "+ foundID+ " is not known.");
	}
	startaddresses[arridx][foundrecCounters[arridx]++] = sectionoffset; // remember
	// start
	// of records
	// Normal-Channel
	sectionoffset = sectionoffset + foundsize + idSize;

	// Skip id after record
	if (redundantids) {
	sectionoffset += 1;
	}
	foundrecords++;
	}
	MDFSorter.log.fine("Found " + foundrecords + " Records.");
	return startaddresses;
	}

	public DGBLOCK copyChannelInfrastructure(MDF3GenBlock last, CGBLOCK towrite)
	throws IOException {
	// Create new Data Group with default values, and write to file.
	DGBLOCK newdg = new DGBLOCK(filestructure.isBigEndian());
	newdg.setChannelGroups(1);
	writeBlock(newdg, null);
	// set link to next DGblock.
	last.setLink(0, newdg);
	// set link to child CGblock.
	newdg.setLink(1, towrite);

	// Modify and write old channel group.
	// No other channel.
	towrite.setLink(0, null);
	towrite.setRecordId(0);
	writeBlock(towrite, null);
	return newdg;
	}

	/**
	* Creates and writes the header of a DataBlock (any Block without links)
	*
	* @param size
	* Size of this block's Data section (length is set to size +24
	* Bytes for header fields.
	* @return The MDFBlock Object, which was created.
	*/
	public DTBLOCK create(long size) {
	DTBLOCK ret;
	ret = new DTBLOCK(filestructure.isBigEndian());
	ret.setLength(size);
	ret.setLinkCount(0);
	ret.setOutputpos(writeptr);
	writtenblocks.add(ret);
	return ret;
	}

	@Override
	public void writeSpacer(long length) {
	// Do nothing in MDF3
	}

	}