[SOLVED]Bitwise "Or" Question.

[S G H]

I'm working on Functions that need "Flags", just like MessageBox.
But, Let's assume i call a function like:
void Test(DWORD Flags)
Let's say i put "MB_OK | MB_ICONERROR" (From the MessageBox, just for testing)
How would i find each value? I know how Or, And, Xor works.

[Albatross]

It's possible that each flag's value is a power of two, in which case one could easily determine the flags from expressing the resulting value as a sum of powers of two. I don't know the mechanics behind the WinAPI MessageBox, but that's just a possibility. :)

-Albatross

[S G H]

It's a nice idea. I may try giving an eye to the values of MB_OK, etc etc. and post here what i get. Thanks for the idea. EDIT: Yes, they use approximatively that idea. This may explain something:

#define MB_OK                       0x00000000L
#define MB_OKCANCEL                 0x00000001L
#define MB_ABORTRETRYIGNORE         0x00000002L
#define MB_YESNOCANCEL              0x00000003L
#define MB_YESNO                    0x00000004L
#define MB_RETRYCANCEL              0x00000005L
#define MB_CANCELTRYCONTINUE        0x00000006L


#define MB_ICONHAND                 0x00000010L
#define MB_ICONQUESTION             0x00000020L
#define MB_ICONEXCLAMATION          0x00000030L
#define MB_ICONASTERISK             0x00000040L

#define MB_USERICON                 0x00000080L

#define MB_DEFBUTTON1               0x00000000L
#define MB_DEFBUTTON2               0x00000100L
#define MB_DEFBUTTON3               0x00000200L
#define MB_DEFBUTTON4               0x00000300L

#define MB_APPLMODAL                0x00000000L
#define MB_SYSTEMMODAL              0x00001000L
#define MB_TASKMODAL                0x00002000L
#define MB_HELP                     0x00004000L

#define MB_NOFOCUS                  0x00008000L
#define MB_SETFOREGROUND            0x00010000L
#define MB_DEFAULT_DESKTOP_ONLY     0x00020000L

#define MB_TOPMOST                  0x00040000L
#define MB_RIGHT                    0x00080000L
#define MB_RTLREADING               0x00100000L

#define MB_TYPEMASK                 0x0000000FL
#define MB_ICONMASK                 0x000000F0L
#define MB_DEFMASK                  0x00000F00L
#define MB_MODEMASK                 0x00003000L
#define MB_MISCMASK                 0x0000C000L 

Depending on the "Section" there are various choices (MB_OK and MB_OKCANCEL cannot be used together), as section i mean: Buttons that will be shown, icon that will be shown...

[Stewbond]

Well, in this case each bit is treated separately. So I'd just do something like the following in your Test(DWORD ) function:

if (Flags & 0x1) do_something();
if (Flags & 0x2) do_something_else();
if (Flags & 0x4) do_something_further();
if (Flags & 0x8) do_another thing();
if (Flags & 0x10) do_yet_another_thing();

[andywestken]

But with names for the flags, not magic numbers, of course!

if (Flags & MB_ICONERROR)
    handleIconError();
if (Flags & MB_OK)
    handleOk();
....

(And actions taken to a condition should be on a different line to the test for it, if you want the VC++ debugger or gdb to work properly.)

[S G H]

Perfect, now i have all I was looking for. Thank you!