function HexToBin(Text, Buffer: PChar; BufSize: Integer): Integer; assembler;
const
Convert: array['0'..'f'] of SmallInt =
( 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,-1,-1,-1,-1,-1,-1,
-1,10,11,12,13,14,15,-1,-1,-1,-1,-1,-1,-1,-1,-1,
-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
-1,10,11,12,13,14,15);
var
I: Integer;
begin
I := BufSize;
while I > 0 do
begin
if not (Text[0] in ['0'..'f']) or not (Text[1] in ['0'..'f']) then Break;
Buffer[0] := Char((Convert[Text[0]] shl 4) + Convert[Text[1]]);
Inc(Buffer);
Inc(Text, 2);
Dec(I);
end;
Result := BufSize - I;
end;