Parse the file.

def Parse(self):
    """Parse the file."""
    if not self._file:
      logging.error("Couldn't open file")
      return

    # Limit read size to 5MB.
    self.input_dat = self._file.read(1024 * 1024 * 5)
    if not self.input_dat.startswith(self.FILE_HEADER):
      logging.error("Invalid index.dat file %s", self._file)
      return

    # Events aren't time ordered in the history file, so we collect them all
    # then sort.
    events = []
    for event in self._DoParse():
      events.append(event)

    for event in sorted(events, key=operator.itemgetter("mtime")):
      yield event