i want to know if A + B will overflow.
i don't want to go ahead and add them, and try to catch an exception
(catching exceptions is much slower; and besides, it's not exceptional -
it's perfectly reasonable to excpect it to happen, and i am going to have to
react anyway).
Also, it is for a library unit. So i don't want to do the (pseudo-code):
procedure IncrementSomeNumber(var A: LongWord; const N: LongWord; var Carry:
LongWord);
begin
{$OVERFLOWCHECKS ON}
try
A := A + N;
Carry := 0;
except
on EIntOverflow do
Carry := 1;
end;
{$OVERFLOWCHECKS OFF}
end;
because i don't know if Overflowchecks *were* off before i got there.
So i'm thinking that i might have to do something ugly like:
procedure IncrementSomeNumber(var A: LongWord; const N: LongWord; var Carry:
LongWord);
var
Intermediate: Inte64;
begin
Intermediate := A + N;
A := Intermediate and $FFFFFFFF;
C := Intermediate shr 32;
end;
promotion to an Int64, and then picking it apart?
Isn't there something inside Delphi itself i can use?
Some of the code that is generated by Delphi itself to look for an overflow?
