SV * parse_string(CLASS, str, …)

        char * CLASS
        char * str
    PREINIT:
        STRLEN n_a;
        xmlDtdPtr res;
        SV * encoding_sv;
        xmlParserInputBufferPtr buffer;
        xmlCharEncoding enc = XML_CHAR_ENCODING_NONE;
        xmlChar * new_string;
        STRLEN len;
    CODE:
        LibXML_init_error();
        if (items > 2) {
            encoding_sv = ST(2);
            if (items > 3) {
                croak("parse_string: too many parameters");
            }
            // warn("getting encoding...\n");
            enc = xmlParseCharEncoding(SvPV(encoding_sv, n_a));
            if (enc == XML_CHAR_ENCODING_ERROR) {
                croak("Parse of encoding %s failed: %s", SvPV(encoding_sv, n_a), SvPV(LibXML_error, n_a));
            }
        }
        buffer = xmlAllocParserInputBuffer(enc);
        // buffer = xmlParserInputBufferCreateMem(str, xmlStrlen(str), enc);
        if ( !buffer)
            croak("cant create buffer!\n" );

        new_string = xmlStrdup((const xmlChar*)str);
        xmlParserInputBufferPush(buffer, xmlStrlen(new_string), (const char*)new_string);

        res = xmlIOParseDTD(NULL, buffer, enc);

        // NOTE: For some reason freeing this InputBuffer causes a segfault!
        // xmlFreeParserInputBuffer(buffer);
        xmlFree(new_string);

        sv_2mortal( LibXML_error );
        LibXML_croak_error();

        if (res == NULL) {
            croak("no DTD parsed!");
        }
        RETVAL = PmmNodeToSv((xmlNodePtr)res, NULL);
    OUTPUT:
        RETVAL