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;
   }
 }