OpenEuphoria

RE: Damn Unions

• Posted by Don Phillips <Graebel at hotmail.com> Jul 26, 2002
• 402 views

Hey Jordah =)

Dont sweat the details on this too hard.  You have been working
with unions all along (kinda), you just didnt know it.  Heres a
good example I hope will make since.

wParam and lParam are 32 bit (DWORD) variables in memory.  Most
of the time you will use them whole (same as dwOemId).  If however
you are processing a WM_MOUSE or similar message, it is no longer
a DWORD but two WORD's (x and y positions).  This is a union.
It can be accessed either by DWORD or 2 WORDS.  In this case just
declare that whole union as DWORD dwOemId.  If you need the other
two elements, peek4u it out into a Euphoria variable and use 
Win32Libs built in lo_word() / hi_word() to extract the parts you
need...

Don Phillips

jordah ferguson wrote:
> Hi All,
> 
> Is there some one out there who can help me link this structure
> to euphoria. My lack of understanding of what a union is has led to 
> this.
> 
> typedef struct _SYSTEM_INFO { // sinf 
> 
>     union { 
>         DWORD  dwOemId; 
>         struct { 
>             WORD wProcessorArchitecture; 
>             WORD wReserved; 
>         }; 
>     }; 
>     DWORD  dwPageSize; 
>     LPVOID lpMinimumApplicationAddress; 
>     LPVOID lpMaximumApplicationAddress; 
>     DWORD  dwActiveProcessorMask; 
>     DWORD  dwNumberOfProcessors; 
>     DWORD  dwProcessorType; 
>     DWORD  dwAllocationGranularity; 
>     WORD  wProcessorLevel; 
>     WORD  wProcessorRevision; 
> } SYSTEM_INFO; 
> 
> Jordah Ferguson.
> 
>