Optimising string handling in application

[Frode Tenneboe <ft@alne.edh.ericsson.se>]

I have a small-ish procedure which only purpose is to take a
formatted string (see example) and replace the callsign(s)
inside with another.

The strings look like:

"ME000=F012;ME001=AAA,BBB,CCC;ME002=FOO...."

I would like to replace "ME001=AAA,BBB,CCC" with "ME001=AAA". The
procedure below does just that. However, looking at the code, I don't
like the lumpyness (in lack of a better word). There must be a
more elegant way of doing this? Any ideas?


   C_Max_Msg_Size : constant Integer := 1450;
   C_Max_Msg_Callsign_Length : constant Integer := 20;

   subtype T_Msg_Data_Str is String(1..C_Max_Msg_Size);
   subtype T_Msg_Callsign is String(1..C_Max_Msg_Callsign_Length);

   procedure Replace_Callsign_In_Msg
     (Msg             : in out Dpu_Loc_Messages.T_Msg_Data_Str;
      Msg_Length      : in out T_Integer_32;
      Callsign        : in     Dpu_Loc_Messages.T_Msg_Callsign;
      Callsign_Length : in     Positive) is

      Data           : Dpu_Loc_Messages.T_Msg_Data_Str;
      Data_Length    : Positive;
      Delete_Start   : Positive;
      Delete_Stop    : Natural;

   begin

      -- Prepare data string for new ME001
      Delete_Start := Ada.Strings.Fixed.Index
        (Source => Msg(1..Msg_Length),
         Pattern => "ME001=") + 6;
      for I in Delete_Start .. Msg_Length loop
         if Msg(I) = ';' then
            Delete_Stop := I - 1;
            exit;
         end if;
      end loop;

      -- delete all callsigns
      declare
         Dummy : String := Ada.Strings.Fixed.Delete
           (Source  => Msg(1..Msg_Length),
            From    => Delete_Start,
            Through => Delete_Stop);
      begin
         Data_Length := Dummy'Length;
         Data(Data'First .. Data'First + Dummy'Length - 1) := Dummy;
      end;

      -- insert new callsign
      declare
         Dummy : String := Ada.Strings.Fixed.Insert
           (Source   => Data(Data'First .. Data_Length),
            Before   => Delete_Start,
            New_Item => Callsign(Callsign'First..Callsign'First + Callsign_Length -1));
      begin
         Data_Length := Dummy'Length;
         Msg(Msg'First .. Msg'First + Data_Length - 1) := Dummy;
      end;

   end Replace_Callsign_In_Msg;



 -Frode

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