Re: String view of file

["Jeffrey R.Carter" <spam.jrcarter.not@spam.acm.org.not>]

On 2022-11-21 09:30, Jesper Quorning wrote:
> 
> Is it possible to write something like this with ADA

"Ada" is a woman's name, not an acronymn.

> package my_rw_file is new file
>    (name => "whatever"
>     ,mode => read_write
>     ,implementation => standard -- or portable or fast
>    );
> package as_string is new. xxx(from => my_rw_file);
> 
> -- parse (as_string);
> package data is new parse (as_string, format => markdown); -- or whatever

If I presume that the '.' in the declaration of As_String is a typo, what you 
have here is a sequence of related generic pkg instantiations, so you can write 
this in Ada if you have the corresponding generic pkgs. I have no idea what the 
result would provide.

If you want to read the arbitrary contents of a file into a String, that's 
easily done:

with Ada.Directories;

package String_A_File is
    use type Ada.Directories.File_Size;

    function File_As_String (Name : in String) return String with
       Pre  => Ada.Directories.Exists (Name) and then
               Ada.Directories.Size (Name) <=
               Ada.Directories.File_Size (Integer'Last),
       Post => File_As_String'Result'First = 1 and
               File_As_String'Result'Last =
               Integer (Ada.Directories.Size (Name) );
end String_A_File;

with Ada.Sequential_IO;

package body String_A_File is
    function File_As_String (Name : in String) return String is
       subtype FAS is String (1 .. Integer (Ada.Directories.Size (Name) ) );

       package FAS_IO is new Ada.Sequential_IO (Element_Type => FAS);

       File   : FAS_IO.File_Type;
       Result : FAS;
    begin -- File_As_String
       FAS_IO.Open (File => File, Mode => FAS_IO.In_File, Name => Name);
       FAS_IO.Read (File => File, Item => Result;
       FAS_IO.Close (File => File);

       return Result;
    end File_As_String;
end String_A_File;

This presumes that Result will fit on the stack. If that's likely to be a 
problem, then you will need to use Unbounded_String and read the file Character 
by Character.

-- 
Jeff Carter
"I have a very small head and I had
better learn to live with it ..."
Edsger Dijkstra
158