Passing 64bit int via Windows message

[Dan203]

I need to send a private message from a control class back to my main window via PostMessage. This message needs to carry a 64bit int value that indicates the current position of the control. (it's a video control) The catch is that I'm pretty sure that WPARAM and LPARAM are both 32bit types, so I think I need to split the 64bit value between the two params and then recombine them in the message handler. Does that sound like the right way to handle this? If so how do you split a 64bit value between two 32bit params? If not how else would you handle it?

Thanks,
Dan

[MrViggy]

You could split the value, using masking and shifting. Or, you can just allocate a 64 bit integer on the heap; pass the pointer to your main window; and release the memory in your message handler.

Viggy

[VictorN]

Do you mean "SendMessage" or PostMessage?
If former - then the size of the buffer to send doesn't matter - you can pass a pointer to this buffer as either WPARAM or LPARAM.
If latter - then in the case of "64bit int value" there is an obvious solution: split it using LARGE_INTEGER (or ULARGE_INTEGER) structure

[OReubens]

have a look at how the LOWORD() and HIWORD() macro's are defined for DWORD->WORD and you can do the same for UINT64->DWORD

the reverse (2 WORD -> 1 DWORD) is done with the MAKELONG() macro, making a MAKEUINT64() would be analogous

[Dan203]

Thanks guys. I got it working using LARGE_INTEGER.

Dan