code: @Override
  	protected void readDataBlock(byte[] data, int offset, int len, int blockHandle) throws DataStoreException
      {
  		try
  		{
  	        dataRandomAccessFile.seek((long)blockHandle*blockSize);
  	        if (dataRandomAccessFile.read(data,offset,len) != len)
  	            throw new DataStoreException("Cannot read "+len+" bytes from store file");
  		}
  		catch (DataStoreException e)
  		{
  		    throw e;
  		}
          catch (IOException e)
          {
              throw new DataStoreException("Could not read data block "+blockHandle+" : "+dataFile.getAbsolutePath(),e);
          }
      }
docs: /*
  (non-Javadoc)
  @see net.timewalker.ffmq4.storage.data.impl.AbstractBlockBasedDataStore#readDataBlock(byte[], int, int, int)