Avoid allocating bytes slice in encoding pre-parse

html5lib/_inputstream.py

@@ -658,9 +658,7 @@ def matchBytes(self, bytes):
  """Look for a sequence of bytes at the start of a string. If the bytes
  are found return True and advance the position to the byte after the
  match. Otherwise return False and leave the position alone"""
- p = self.position
- data = self[p:p + len(bytes)]
- rv = data.startswith(bytes)
+ rv = self.startswith(bytes, self.position)
  if rv:
  self.position += len(bytes)
  return rv