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;
 }
 public byte[] Convert_to_local_urls(byte[] rel_url_prefix, byte[] src, List_adp list) {
   try {
     int src_len = src.length;
     int prv_pos = 0;
     Bry_bfr bfr = Bry_bfr_.New_w_size(src_len);
     Hash_adp img_hash = Hash_adp_bry.cs();
     while (true) {
       int url_pos = Bry_find_.Find_fwd(src, Bry_url, prv_pos);
       if (url_pos == Bry_find_.Not_found) {
         bfr.Add_mid(src, prv_pos, src_len);
         break;
       } // no more "url("; exit;
       int bgn_pos = url_pos + Bry_url_len; // set bgn_pos after "url("
       byte bgn_byte = src[bgn_pos];
       byte end_byte = Byte_ascii.Null;
       boolean quoted = true;
       switch (bgn_byte) { // find end_byte
         case Byte_ascii.Quote:
         case Byte_ascii.Apos: // quoted; end_byte is ' or "
           end_byte = bgn_byte;
           ++bgn_pos;
           break;
         default: // not quoted; end byte is ")"
           end_byte = Byte_ascii.Paren_end;
           quoted = false;
           break;
       }
       int end_pos = Bry_find_.Find_fwd(src, end_byte, bgn_pos, src_len);
       if (end_pos
           == Bry_find_.Not_found) { // unclosed "url("; exit since nothing else will be found
         usr_dlg.Warn_many(
             GRP_KEY,
             "parse.invalid_url.end_missing",
             "could not find end_sequence for 'url(': bgn='~{0}' end='~{1}'",
             prv_pos,
             String_.new_u8__by_len(src, prv_pos, prv_pos + 25));
         bfr.Add_mid(src, prv_pos, src_len);
         break;
       }
       if (end_pos - bgn_pos == 0) { // empty; "url()"; ignore
         usr_dlg.Warn_many(
             GRP_KEY,
             "parse.invalid_url.empty",
             "'url(' is empty: bgn='~{0}' end='~{1}'",
             prv_pos,
             String_.new_u8__by_len(src, prv_pos, prv_pos + 25));
         bfr.Add_mid(src, prv_pos, bgn_pos);
         prv_pos = bgn_pos;
         continue;
       }
       byte[] img_raw = Bry_.Mid(src, bgn_pos, end_pos);
       int img_raw_len = img_raw.length;
       if (Bry_.Has_at_bgn(img_raw, Bry_data_image, 0, img_raw_len)) { // base64
         bfr.Add_mid(src, prv_pos, end_pos); // nothing to download; just add entire String
         prv_pos = end_pos;
         continue;
       }
       int import_url_end =
           Import_url_chk(
               rel_url_prefix,
               src,
               src_len,
               prv_pos,
               url_pos,
               img_raw,
               bfr); // check for embedded stylesheets via @import tag
       if (import_url_end != Bry_find_.Not_found) {
         prv_pos = import_url_end;
         continue;
       }
       byte[] img_cleaned = Xob_url_fixer.Fix(wiki_domain, img_raw, img_raw_len);
       if (img_cleaned == null) { // could not clean img
         usr_dlg.Warn_many(
             GRP_KEY,
             "parse.invalid_url.clean_failed",
             "could not extract valid http src: bgn='~{0}' end='~{1}'",
             prv_pos,
             String_.new_u8(img_raw));
         bfr.Add_mid(src, prv_pos, bgn_pos);
         prv_pos = bgn_pos;
         continue;
       }
       if (!img_hash.Has(img_cleaned)) { // only add unique items for download;
         img_hash.Add_as_key_and_val(img_cleaned);
         list.Add(String_.new_u8(img_cleaned));
       }
       img_cleaned =
           Replace_invalid_chars(
               Bry_.Copy(
                   img_cleaned)); // NOTE: must call ByteAry.Copy else img_cleaned will change
                                  // *inside* hash
       bfr.Add_mid(src, prv_pos, bgn_pos);
       if (!quoted) bfr.Add_byte(Byte_ascii.Quote);
       bfr.Add(img_cleaned);
       if (!quoted) bfr.Add_byte(Byte_ascii.Quote);
       prv_pos = end_pos;
     }
     return bfr.To_bry_and_clear();
   } catch (Exception e) {
     usr_dlg.Warn_many(
         "",
         "",
         "failed to convert local_urls: ~{0} ~{1}",
         String_.new_u8(rel_url_prefix),
         Err_.Message_gplx_full(e));
     return src;
   }
 }