I need to combine two 32-bit values to create a 64-bit value. I'm looking for something analogous to MAKEWORD and MAKELONG. I can easily define my own macro or function, but if the API already provides one, I'd prefer to use that.
2 Answers
I cannot find any in the Windows API. However, I do know that you work mostly (or, at least, a lot) with Delphi, so here is a quick Delphi function:
function MAKELONGLONG(A, B: cardinal): UInt64; inline; begin PCardinal(@result)^ := A; PCardinal(cardinal(@result) + sizeof(cardinal))^ := B; end; Even faster:
function MAKELONGLONG(A, B: cardinal): UInt64; asm end; Explanation: In the normal register calling convention, the first two arguments (if cardinal-sized) are stored in EAX and EDX, respetively. A (cardinal-sized) result is stored in EAX. Now, a 64-bit result is stored in EAX (less significant bits, low address) and EDX (more significant bits, high address); hence we need to move A to EAX and B to EDX, but they are already there!
Personally I prefer C-macros
#define MAKE_i64(hi, lo) ( (LONGLONG(DWORD(hi) & 0xffffffff) << 32 ) | LONGLONG(DWORD(lo) & 0xffffffff) ) 
