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.

4

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!

2

Personally I prefer C-macros

#define MAKE_i64(hi, lo) ( (LONGLONG(DWORD(hi) & 0xffffffff) << 32 ) | LONGLONG(DWORD(lo) & 0xffffffff) )
1

Your Answer

Sign up or log in

Sign up using Google Sign up using Facebook Sign up using Email and Password

Post as a guest

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.