def _get_codepage_char_map(self, encoding):
<EOL>if encoding in self.available_characters:<EOL><INDENT>return self.available_characters[encoding]<EOL><DEDENT>codepage_char_list = self._get_codepage_char_list(encoding)<EOL>codepage_char_map = dict((utf8, i + <NUM_LIT>) for (i, utf8) in enumerate(codepage_char_list))<EOL>self.available_characters[encoding] = codepage_char_map<EOL>return codepage_char_map<EOL>
Get codepage character map

        Process an encoding and return a map of UTF-characters to code points
        in this encoding.

        This is generated once only, and returned from a cache.

        :param encoding: The name of the encoding.