I tried to use the bit helpers like https://www.freepascal.org/docs-html/rtl/sysutils/twordhelper.testbit.html but the bit to test is 0..15. I expected this to work like https://wiki.freepascal.org/Bit_manipulation but that doesn't seem to be the case.

Does there exist bit helpers like GetBit (from the last link) in the RTL?

Regards,
Ryan Joseph

Ryan Joseph wrote

I tried to use the bit helpers like https://www.freepascal.org/docs-html/rtl/sysutils/twordhelper.testbit.html but the bit to test is 0..15.

There are only 16 bits in a word, so that is correct.

Yes, this is testbit.

Why do you say it does not work ?

Michael.

Oh my, I was confusing my terms I think. I wanted to do bit masking (I think it's called). I was expecting there to be something like TestFlag in the RTL since I can never remember the syntax "Value = (Value or Index)"

function TestFlag(Value: QWord; Index: Byte): Boolean;
begin
  result := Value = (Value or Index);
end;
const
  KMOD_LCTRL = $0040;
  KMOD_RCTRL = $0080;
var
  flags: LongWord;
begin
  flags := KMOD_LCTRL + KMOD_RCTRL;
  writeln('TestBit: ', flags.TestBit(KMOD_LCTRL));
  writeln('TestFlag: ', TestFlag(flags, KMOD_LCTRL));

Regards,
Ryan Joseph

Hm. I'm not sure that this code does what you need.

But masking is indeed not in the helpers.

Michael.

W dniu 2022-02-21 o 13:18, Ryan Joseph via fpc-pascal pisze:

Should you use the "AND" operator instead of "OR" for bit testing?

result := Value = (Value AND Index);

Michał.

W dniu 2022-02-21 o 13:34, gabor via fpc-pascal pisze:

Of course not. My mistake.
Michał.

Try it yourself, it does indeed work. How else are you supposed to test these kinds of bit flag APIs where all the flags are OR'd together into an LongWord? A type helper would be great because clearly this stuff is hard to remember.

Regards,
Ryan Joseph

No.

result := (Byte(Value) AND Index)>0;
result := Index = (Byte(Value) AND Index);
result := Byte(Value) = (Byte(Value) OR Index);

Mattias