code: def readtag_header(self):
          
          pos = self.tell()
          tag_type_and_length = self.readUI16()
          tag_length = tag_type_and_length & 0x003f
          if tag_length == 0x3f:
              # The SWF10 spec sez that this is a signed int.
              # Shouldn't it be an unsigned int?
              tag_length = self.readSI32();
          return SWFRecordHeader(tag_type_and_length >> 6, tag_length, self.tell() - pos)
docs: Read a tag header