code: def read_chunk(filename, offset=-1, length=-1, escape_data=False):
    
    try:
      length = int(length)
      offset = int(offset)
    except ValueError:
      return {}
  
    if not os.path.isfile(filename):
      return {}
  
    try:
      fstat = os.stat(filename)
    except Exception:
      return {}
  
    if offset == -1:
      offset = fstat.st_size
  
    if length == -1:
      length = fstat.st_size - offset
  
    with open(filename, "r") as fp:
      fp.seek(offset)
      try:
        data = fp.read(length)
      except IOError:
        return {}
  
    if data:
      data = _escape_data(data) if escape_data else data
      return dict(offset=offset, length=len(data), data=data)
  
    return dict(offset=offset, length=0)
docs: Read a chunk of a file from an offset upto the length.