Re: Concatenating files

[Jacob Sparre Andersen <sparre@nbi.dk>]

mhamel_98@yahoo.com writes:

> Hello c.l.a.  I have a storage system for a program of mine that
> uses two files for each object - a text header file via text_io and
> a data file via sequential_io.  I am wondering if there is an
> elegant way to put the contents of these two files into one.  The
> textual header bit is fixed size/length.  Any ideas?  ObjectAda 95
> on NT.

If ObjectAda 95 on NT has something like POSIX.Memory_Mapping, then
you could do it like this:

   Data_Length : constant Natural
     := (File_Size (File) - Fixed_Header_Length) * 8 / Element_Type'Size;

   type File_Content is
      record
         Header : String (1 .. Fixed_Header_Length);
         Data   : array (1 .. Data_Length) of Element_Type;
      end record;
   
   [...]

   Address := Map_Memory (Length     => File_Size (File),
                          Protection => Allow_Read + Allow_Write,
                          Mapping    => Map_Shared,
                          File       => File,
                          Offset     => 0);

   [...]

   Content : File_Content;
   for Content'Address use Address;

   --  Here you can access Content.Header and Content.Data just like
   --  any other object in Ada.

The tricky part in this is when you want to append to the file.  For
now I will leave that as an exercise for the reader.

Greetings,

Jacob (a big fan of POSIX.Memory_Mapping ;-)
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