Re: Minimum Record Size? LONG

[Rick Stikkers <rstikkers@telis.org>]

Steve wrote:

>Here's an approach taking advantage of using "Slices" of arrays (tested
>w/Gnat3.15p-nt):
>
>  
>
If you're not worried about machine cross compatibility, the other 
option would be to just give in to the endianness of the machine and 
swap everything so that the endianness is fully preserved.  The 
following code segment gives the desired results.

with TEXT_IO;
procedure comp is

type six_bits is range 0..2**6-1;
for six_bits'SIZE use 6;
type four_sixes is record
  six_bits_0 : six_bits;
  six_bits_1 : six_bits;
  six_bits_2 : six_bits;
  six_bits_3 : six_bits;
end record;
for four_sixes use record
  six_bits_0 at 0 range 18..23;
  six_bits_1 at 0 range 12..17;
  six_bits_2 at 0 range 6..11;
  six_bits_3 at 0 range 0..5;
end record;
for four_sixes'SIZE use 24;

type eight_bits is range 0..2**8-1;
for eight_bits'SIZE use 8;
type three_eights is record
  eight_bits_0 : eight_bits;
  eight_bits_1 : eight_bits;
  eight_bits_2 : eight_bits;
end record;
for three_eights use record
  eight_bits_0 at 2 range 0..7;
  eight_bits_1 at 1 range 0..7;
  eight_bits_2 at 0 range 0..7;
end record;
for three_eights'SIZE use 24;

six_var : four_sixes;
eight_var : three_eights;
for eight_var use at six_var'ADDRESS;

begin
  six_var.six_bits_0 := 28;
  six_var.six_bits_1 := 55;
  six_var.six_bits_2 := 25;
  six_var.six_bits_3 := 50;
  text_io.put_line(eight_bits'IMAGE(eight_var.eight_bits_0)&"  "&
                          eight_bits'IMAGE(eight_var.eight_bits_1)&"   "&
                          eight_bits'IMAGE(eight_var.eight_bits_2));
end;