Re: reading a text file into a string

["Nick Roberts" <nick.roberts@acm.org>]

On Fri, 16 Jul 2004 03:27:57 +1000, zork <zork@nospam.com> wrote:

> hi, i would like to read a whole text file into a string. I thought of  
> using
> an unbounded_string for this:
>
> ----------
> c, char: character;
> text : unbounded_string;
> ...
> -- read in text file
> while not end_of_file ( File ) loop
>     Get ( File, c );
>     append ( text, c );
> end loop;
> ...
> put ( to_string ( text ) ); -- display content of unbounded_string
>
> -- process text
> for i in 1 .. length ( text ) loop
>   char := element ( text, i );
>   ...
> end loop;
> -----------
>
> ... is this the general way of going about it? or is there a more  
> prefered
> method of reading in a whole text file (into whatever format) for
> processing?

It is usual to read and process information from files a piece at a time.

Quite often a file is read a piece at a time, each piece is interpreted in  
some way, and then some structure is built up in memory from the  
interpreted pieces. Then, typically, further processing is done using the  
whole structure.

It is unusual to read an entire text file into a string in memory.  
However, sometimes this may be a quick and convenient technique for  
achieving results in a hurry. An unbounded string will generally be the  
appropriate data structure to use for this purpose. The problem you do not  
address with the code you suggest above -- as another poster has pointed  
out -- is that of line breaks. One easy possibility might be to insert:

    if End_of_Line(File) then
       Append( text, Ada.Characters.Latin_1.NUL );
       Skip_Line(File);
    end if;

between the Get and the append. Line breaks are then indicated by the NUL  
character, and could be processed as such. This should work provided the  
file itself does not contain any NULs.

-- 
Nick Roberts