code: public byte[] getByteArray(Integer offset)
     {
        byte[] result = null;
  
        if (offset != null)
        {
           result = m_map.get(offset);
        }
  
        return (result);
     }
docs: This method retrieves a byte array containing the data at the
  given offset in the block. If no data is found at the given offset
  this method returns null.
  
  @param offset offset of required data
  @return byte array containing required data