How to save/load Set of Types?

Question

I have this code

type
  TXSample = (xsType1, xsType2, xsType3, xsType4, xsType5, xsType6, xsType6, xsTyp7, xsType8); // up to FXSample30;  
..

private
  FX         


        

Answer 1

Or we can make compiler forget about the types completly and then define what it should see (in case we know in compile-time what it sould see). This solution is so awful as it can be written on just one line.

type
  // Controls.TCMMouseWheel relies on TShiftState not exceeding 2 bytes in size 
  TShiftState = set of (ssShift, ssAlt, ssCtrl,
                        ssLeft, ssRight, ssMiddle, 
                        ssDouble, ssTouch, ssPen, 
                        ssCommand, ssHorizontal); 

var 
  Shifts : TShiftState;
  Value :  Integer;
begin
  Shifts := TShiftState((Pointer(@Value))^):

  Value  := (PInteger(@Shifts))^;

  if ssShift in TShiftState((Pointer(@Value))^) then 
     Exit;
end;

It happens that unused (top) bits are set (or not) but it has no influence on set operations (in, =, +, -, * .. ).

This line in Delphi:

Shifts := TShiftState((Pointer(@Value))^);

is like this in Assembler (Delphi XE6):

lea eax,[ebp-$0c]
mov ax,[eax]
mov [ebp-$06],ax

On Delphi 2007 (where is TShiftState is smaller so Byte can be used) this Assembler:

movzx eax,[esi]
mov [ebp-$01],al