Search the data for a hit.

def FindLiteral(self, pattern, data):
    """Search the data for a hit."""
    pattern = utils.Xor(pattern, self.xor_in_key)

    offset = 0
    while 1:
      # We assume here that data.find does not make a copy of pattern.
      offset = data.find(pattern, offset)

      if offset < 0:
        break

      yield (offset, offset + len(pattern))

      offset += 1