Re: GNAT Ada for DOS - Reading Integers Problem

[tore@lis.pitt.edu (Tore Joergensen)]

William Paul Berriss (strberis) wrote:
[...snip...]
: What it does is this:
: When reading in the peppers.ras file it gets the nymbers form the header BUT
: instead of 512 it shows (on the screen) 131072, and instead of 24 it shows 
: something huge like 6291456.  All these 'wrong' numbers can be made from
: other numbers, e.g. 131072 is 256 times 512.  It should have been 512!

: The image is fine, I can view it on PaintBrush for windows say.
: Also, if I strip this header of 'huge' numbers and replace it with the
: numbers 512 ,512, 24, 1 etc then when I read it in again I do get the correct
: numbers, 512, 512 ,24, 1 etc.  But then, of course? , PaintBrush cannot read
: in the image. Obviously the numbers look 'funny' to IT !
[...snip...]

What you have discovered is the little endian vs. big endian problem.
You can read about it in Ada95-LRM:13.5.3. I'm not sure if gnat supports
specifying the bit_order attribute or not, but there are simple solutions
to fix it. One way to do it would be to define a 16 bit unsigned integer
and use 'A := shift_left(A,8)+shift_right(A,8);' (see LRM:B.2). I guess
somebody can tell you the best way to do it (if it isn't the above
solution).
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| Tore B. Joergensen      | e-mail : tore@lis.pitt.edu                |
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