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From: "Steve" <nospam_steved94@attbi.com>
Newsgroups: comp.lang.ada
References: <bat3ee$2ec$1@ns.felk.cvut.cz>
Subject: Re: I/O - exception handling
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Here's an approach that only uses close once, but it isn't pretty either.

 begin
    begin
       begin
          Open (File, Name => "test.txt", Mode => In_File);
       exception
            when others =>
                null; -- report exception opening file ???
                return;
       end;
       Get_Line (File, S1);
       Get_Line (File, S2);
    exception
       when others =>
           null; -- report exception???
    end;
    Close (File);
 exception
    when others =>
      null; -- report exception ???
 end Read_Something;

Steve
(The Duck)

"Sergey Koshcheyev" <serko84@hotmail.com> wrote in message
news:bat3ee$2ec$1@ns.felk.cvut.cz...
> Hi,
>
> I have this problem: I have a simple piece of code opening a file, reading
a
> few lines, then closing it. Now, I want this piece of code to be "safe",
> i.e. not to leak any resources (the open file) in case of errors and not
to
> propagate any exceptions. What is the best style to write this code?
>
> Currently, I have something like (not compiled):
>
> procedure Read_Something (...) is
>    use Ada.Text_IO;
>    use Ada.Strings.Unbounded;
>    use Ada.Strings.Unbounded.Text_IO;
>    --  GNAT-specific package, I believe
>
>    File : File_Type;
>    S1, S2 : Unbounded_String;
>
> begin
>    Open (File, Name => "test.txt", Mode => In_File);
>    Get_Line (File, S1);
>    Get_Line (File, S2);
>    Close (File);
>
> exception
>    when others =>
>       if Is_Open (File) then
>          begin
>             Close (File);
>          exception
>             --  Close can raise exceptions too!
>             when others => null;
>          end;
>       end if;
> end Read_Something;
>
> However, this looks ugly to me, since I have to close the file in two
> places, and also guard for exceptions while handling exceptions. Is there
a
> better solution or is this sort of thing OK in the Ada way?
>
> Sergey.
>
>