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From: general@ciberpiula.net (Santiago A.)
Newsgroups: comp.lang.ada
Subject: Newbie, returning strings in Ada
Date: 16 Feb 2003 03:33:52 -0800
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Date: 2003-02-16T11:33:52+00:00
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Hello:
 I'm a newbie in Ada, and I'm trying to test AdaSockets. Using the
example listener.adb", I try to read a line from a socket but the
program has a strange behavior. After a little investigation I think
it has little to do with sockets, I'm afraid it's about something I
haven't understood about Ada strings. So I decided to to post it in
ada group instead AddSockets developers, if it's not the case, sorry
;-)

I use get_line function of AdaSockets, this reads character by
character from the socket, and add them to a string, if the char is LF
then returns. Everything works fine until It returns, then Depending
upon how I call the function, the programa stops.

This is the original procedure found in AdaSockets body:

     
   function Get_Line (
          Socket : Socket_Fd'Class ) 
      return String is 
       Result : String (1 .. 1024);  
       Index  : Positive           := Result'First;  
       Char   : Character;  
    begin
       loop
          Char := Get_Char (Socket);
          if Char = Lf then
             return Result (1 .. Index - 1);
          elsif Char /= Cr then
             Result (Index) := Char;
             Index := Index + 1;
             if Index > Result'Last then
                return Result & Get_Line (Socket);
             end if;
          end if;
       end loop;
    end Get_Line;

1) This case works fine:
      Put_Line (Sock, get_line(Socket) );

   where put_line spec is:  

      procedure Put_Line (Socket : in Socket_FD'Class;
                         Str : in String)

2) This case works fine too:

        var U_Line:Unbounded_String;
          ....
        U_Line:=To_Unbounded_String(Get_Line(Sock));


3) This case fails 

        var F_Line:string:="1234567890";   
         .....
        F_Line:=Get_Line(Sock);

I type two characters in the client side and press enter. Everything
seems to work fine, the server reads the first character, reads the
second,reads the LF, enters in the return sentence and... never
returns to the caller.

Is there any problem in a function that returns a string with lenght 2
into a variable string(10)?

Must the returned string and the variable that will hold the result be
of the same length?

By the way, I'm working with gnat-3.15p on Windows 2000.

Thanks