void odbc_lob_read(sth, colno, bufsv, length, attr = NULL)
     SV *sth
     int colno
     SV *bufsv
     UV  length
     SV *attr;
    PROTOTYPE: $$$$;$
    PREINIT:
     char *buf;
     UV ret_len;
     IV sql_type = 0;
    CODE:
     if (length == 0) {
         croak("Cannot retrieve 0 length lob");
     }
     if (SvROK(bufsv)) {
         bufsv = SvRV(bufsv);
     }
     if (attr) {
         SV **svp;
         DBD_ATTRIBS_CHECK("odbc_lob_read", sth, attr);
         DBD_ATTRIB_GET_IV(attr, "Type", 4, svp, sql_type);
     }
     sv_setpvn(bufsv, "", 0);                   /* ensure we can grow ok */
     buf = SvGROW(bufsv, length + 1);
     ret_len = odbc_st_lob_read(sth, colno, bufsv, length, sql_type);
     if (ret_len < 0) {
         ST(0) = &PL_sv_undef;
     } else {
         SvCUR_set(bufsv, ret_len);      /* set length in SV */
         *SvEND(bufsv) = '\0';           /* NUL terminate */
         SvSETMAGIC(bufsv);
         ST(0) = sv_2mortal(newSViv(ret_len));
     }
     XSRETURN(1);