Natools

         raise Ada.Strings.Index_Error;
      end if;

      case (Going) is
      when Ada.Strings.Forward =>
         loop
            Result := Ada.Strings.Fixed.Index
              (Source.Data (Chunk).all, Set, Offset, Test, Going);
              (Source.Data (Chunk).all
                 (1 .. Positive'Min (Source.Size
                                       - (Chunk - 1) * Source.Chunk_Size,
                                     Source.Chunk_Size)),
               Set, Offset, Test, Going);
            if Result /= 0 then
               return (Chunk - 1) * Source.Chunk_Size + Result;
            end if;
            if Chunk = Source.Data'Last then
               return 0;
            end if;
            Chunk := Chunk + 1;
            Offset := 1;
         end loop;
      when Ada.Strings.Backward =>
         loop
            Result := Ada.Strings.Fixed.Index
              (Source.Data (Chunk).all, Set, Offset, Test, Going);
              (Source.Data (Chunk).all
                 (1 .. Positive'Min (Source.Size
                                       - (Chunk - 1) * Source.Chunk_Size,
                                     Source.Chunk_Size)),
               Set, Offset, Test, Going);
            if Result /= 0 then
               return (Chunk - 1) * Source.Chunk_Size + Result;
            end if;
            if Chunk = Source.Data'First then
               return 0;
            end if;
            Chunk := Chunk - 1;