Am 13.08.2020 um 22:37 schrieb Bo Berglund via fpc-pascal:
I am working on the conversion of a service application from
Windows/Delphi to Linux/FPC.
When going through the code I found this procedure, which I do not
quite understand the workings of, can someone please explain how it
operates?
procedure Swap2(var Source);
var
H, L: word;
begin
H := Hi(word(Source));
L := Lo(word(Source));
word(Source) := (L * 256) + H;
end;
It is used in the code like this where Hd is a record and numSteps is
a word sized field:
Swap2(Hd.numSteps);
In other places when word sized variables need to be swapped
(Little/Big-endian conversions) it is done like this instead where
CmdProgNum is a smallint value and the built-in swap function is used:
FR.CmdProgNum := Swap(FR.CmdProgNum);
So the code uses a mix of these and I do not understand what the
strange looking function does...
It also does an endian swap, but in place (it's a *procedure* with a var
parameter) instead of as a function that returns the swapped value, but
leaves the input untouched.
Regards,
Sven
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