private int Import_url_chk(
     byte[] rel_url_prefix,
     byte[] src,
     int src_len,
     int old_pos,
     int find_bgn,
     byte[] url_raw,
     Bry_bfr bfr) {
   if (find_bgn < Bry_import_len) return Bry_find_.Not_found;
   if (!Bry_.Match(src, find_bgn - Bry_import_len, find_bgn, Bry_import))
     return Bry_find_.Not_found;
   byte[] css_url = url_raw;
   int css_url_len = css_url.length;
   if (css_url_len > 0
       && css_url[0]
           == Byte_ascii
               .Slash) { // css_url starts with "/"; EX: "/page" or "//site/page" DATE:2014-02-03
     if (css_url_len > 1
         && css_url[1] != Byte_ascii.Slash) // skip if css_url starts with "//"; EX: "//site/page"
     css_url = Bry_.Add(rel_url_prefix, css_url); // "/w/a.css" -> "//en.wikipedia.org/w/a.css"
   }
   css_url =
       Bry_.Replace(
           css_url,
           Byte_ascii.Space,
           Byte_ascii
               .Underline); // NOTE: must replace spaces with underlines else download will fail;
                            // EX:https://it.wikivoyage.org/w/index.php?title=MediaWiki:Container e
                            // Infobox.css&action=raw&ctype=text/css; DATE:2015-03-08
   byte[] css_src_bry = Import_url_build(stylesheet_prefix, rel_url_prefix, css_url);
   String css_src_str = String_.new_u8(css_src_bry);
   download_wkr.Download_xrg()
       .Prog_fmt_hdr_(
           usr_dlg.Log_many(
               GRP_KEY, "logo.download", "downloading import for '~{0}'", css_src_str));
   byte[] css_trg_bry = download_wkr.Download_xrg().Exec_as_bry(css_src_str);
   if (css_trg_bry == null) {
     usr_dlg.Warn_many("", "", "could not import css: url=~{0}", css_src_str);
     return Bry_find_.Not_found; // css not found
   }
   bfr.Add_mid(src, old_pos, find_bgn - Bry_import_len).Add_byte_nl();
   bfr.Add(Bry_comment_bgn).Add(css_url).Add(Bry_comment_end).Add_byte_nl();
   if (Bry_find_.Find_fwd(css_url, Wikisource_dynimg_ttl) != -1)
     css_trg_bry =
         Bry_.Replace(
             css_trg_bry,
             Wikisource_dynimg_find,
             Wikisource_dynimg_repl); // FreedImg hack;
                                      // PAGE:en.s:Page:Notes_on_Osteology_of_Baptanodon._With_a_Description_of_a_New_Species.pdf/3 DATE:2014-09-06
   bfr.Add(css_trg_bry).Add_byte_nl();
   bfr.Add_byte_nl();
   int semic_pos = Bry_find_.Find_fwd(src, Byte_ascii.Semic, find_bgn + url_raw.length, src_len);
   return semic_pos + Int_.Const_dlm_len;
 }
 private void Download_fils(Io_url css_dir, String[] ary) {
   int ary_len = ary.length;
   for (int i = 0; i < ary_len; i++) {
     String src = ary[i];
     Io_url trg =
         css_dir.GenSubFil_nest(
             Op_sys.Cur().Fsys_http_frag_to_url_str(Replace_invalid_chars_str(src)));
     if (Io_mgr.Instance.ExistsFil(trg)) continue;
     download_wkr.Download(true, "https://" + src, trg, "download: " + src); // ILN
     if (Io_mgr.Instance.QueryFil(trg).Size()
         == 0) { // warn if 0 byte files downloaded; DATE:2015-07-06
       Xoa_app_.Usr_dlg()
           .Warn_many("", "", "css.download; 0 byte file downloaded; file=~{0}", trg.Raw());
     }
   }
 }