How to use

FSEditLogLoader$PositionTrackingInputStream

in

org.apache.hadoop.hdfs.server.namenode

fStream = log.getInputStream();
bin = new BufferedInputStream(fStream);
tracker = new FSEditLogLoader.PositionTrackingInputStream(bin);
dataIn = new DataInputStream(tracker);
try {

long skipAmt = log.length() - tracker.getPos();
if (skipAmt > 0) {
 if (LOG.isDebugEnabled()) {
    " out of " + lastTxId);
 tracker.clearLimit();
 IOUtils.skipFully(tracker, skipAmt);

@Override
public int read(byte[] data, int offset, int length) throws IOException {
 checkLimit(length);
 int ret = super.read(data, offset, length);
 if (ret > 0) curPos += ret;
 return ret;
}

long skipAmt = log.length() - tracker.getPos();
if (skipAmt > 0) {
 if (LOG.isDebugEnabled()) {
    " out of " + lastTxId);
 tracker.clearLimit();
 IOUtils.skipFully(tracker, skipAmt);

long skipAmt = log.length() - tracker.getPos();
if (skipAmt > 0) {
 if (LOG.isDebugEnabled()) {
    " out of " + lastTxId);
 tracker.clearLimit();
 IOUtils.skipFully(tracker, skipAmt);

BufferedInputStream bin = new BufferedInputStream(fin);
FSEditLogLoader.PositionTrackingInputStream tracker = 
  new FSEditLogLoader.PositionTrackingInputStream(bin);
try {
 tracker.setLimit(2);
 tracker.mark(100);
 tracker.read();
 tracker.read();
 try {
  tracker.read();
  fail("expected to get IOException after reading past the limit");
 } catch (IOException e) {
 tracker.reset();
 tracker.mark(100);
 byte arr[] = new byte[3];
 try {
  tracker.read(arr);
  fail("expected to get IOException after reading past the limit");
 } catch (IOException e) {
 tracker.reset();
 arr = new byte[2];
 tracker.read(arr);
} finally {
 tracker.close();

fStream = log.getInputStream();
bin = new BufferedInputStream(fStream);
tracker = new FSEditLogLoader.PositionTrackingInputStream(bin);
dataIn = new DataInputStream(tracker);
try {

fStream = log.getInputStream();
bin = new BufferedInputStream(fStream);
tracker = new FSEditLogLoader.PositionTrackingInputStream(bin);
dataIn = new DataInputStream(tracker);
try {

/**
 * Open an EditLogInputStream for the given file.
 * @param name filename to open
 * @param firstTxId first transaction found in file
 * @param lastTxId last transaction id found in file
 * @throws LogHeaderCorruptException if the header is either missing or
 *         appears to be corrupt/truncated
 * @throws IOException if an actual IO error occurs while reading the
 *         header
 */
EditLogFileInputStream(File name, long firstTxId, long lastTxId)
  throws LogHeaderCorruptException, IOException {
 file = name;
 rp = new RandomAccessFile(file, "r");    
 fStream = new FileInputStream(rp.getFD());
 fc = rp.getChannel();
 BufferedInputStream bin = new BufferedInputStream(fStream);  
 tracker = new FSEditLogLoader.PositionTrackingInputStream(bin);  
 DataInputStream in = new DataInputStream(tracker);
 try {
  logVersion = readLogVersion(in);
 } catch (EOFException eofe) {
  throw new LogHeaderCorruptException("No header found in log");
 }
 reader = new FSEditLogOp.Reader(in, logVersion);
 this.firstTxId = firstTxId;
 this.lastTxId = lastTxId;
}

/**
 * Process image file.
 */
public void go() throws IOException  {
 DataInputStream in = null;
 PositionTrackingInputStream tracker = null;
 ImageLoader fsip = null;
 boolean done = false;
 try {
  tracker = new PositionTrackingInputStream(new BufferedInputStream(
       new FileInputStream(new File(inputFile))));
  in = new DataInputStream(tracker);
  int imageVersionFile = findImageVersion(in);
  fsip = ImageLoader.LoaderFactory.getLoader(imageVersionFile);
  if(fsip == null) 
   throw new IOException("No image processor to read version " +
     imageVersionFile + " is available.");
  fsip.loadImage(in, processor, skipBlocks);
  done = true;
 } finally {
  if (!done) {
   LOG.error("image loading failed at offset " + tracker.getPos());
  }
  IOUtils.cleanup(LOG, in, tracker);
 }
}

/**
 * Process image file.
 */
public void go() throws IOException  {
 DataInputStream in = null;
 PositionTrackingInputStream tracker = null;
 ImageLoader fsip = null;
 boolean done = false;
 try {
  tracker = new PositionTrackingInputStream(new BufferedInputStream(
       new FileInputStream(new File(inputFile))));
  in = new DataInputStream(tracker);
  int imageVersionFile = findImageVersion(in);
  fsip = ImageLoader.LoaderFactory.getLoader(imageVersionFile);
  if(fsip == null) 
   throw new IOException("No image processor to read version " +
     imageVersionFile + " is available.");
  fsip.loadImage(in, processor, skipBlocks);
  done = true;
 } finally {
  if (!done) {
   LOG.error("image loading failed at offset " + tracker.getPos());
  }
  IOUtils.cleanup(LOG, in, tracker);
 }
}

@Override
public long getPosition() {
 return tracker.getPos();
}

@Override
public long getPosition() {
 return tracker.getPos();
}

@Override
public long getPosition() {
 return tracker.getPos();
}

void setBytes(byte[] newBytes, int version) throws IOException {
 inner.setData(newBytes);
 tracker = new FSEditLogLoader.PositionTrackingInputStream(inner);
 in = new DataInputStream(tracker);
 this.version = version;
 reader = new FSEditLogOp.Reader(in, tracker, version);
}

@Override
public long getPosition() {
 if (state == State.OPEN) {
  return tracker.getPos();
 } else {
  return 0;
 }
}

@Override
public int read(byte[] data) throws IOException {
 checkLimit(data.length);
 int ret = super.read(data);
 if (ret > 0) curPos += ret;
 return ret;
}

@Override
public int read(byte[] data, int offset, int length) throws IOException {
 checkLimit(length);
 int ret = super.read(data, offset, length);
 if (ret > 0) curPos += ret;
 return ret;
}

@Override
public long getPosition() throws IOException{
 return tracker.getPos();
}

@Override
public int read(byte[] data) throws IOException {
 checkLimit(data.length);
 int ret = super.read(data);
 if (ret > 0) curPos += ret;
 return ret;
}