> On Sun, Aug 17, 2014 at 3:28 PM, Ruben J=F6nsson <ruben@rjjournal.net> wr=
ote:
> > Well actually it could be something like this instead:
> >
> > typedef union {
> >   uint32_t rgb_32;
> >   struct {
> >     uint8_t red:8;
> >     uint8_t green:8;
> >     uint8_t blue:8;
> >     uint8_t pad:8;
> >   }col;
> > }RGB;
> >
> > Then you can do:
> >
> > RGB rgb;
> > rgb.col.red=3D12;
>=20
> And would I then do "rgb.col =3D 0x12345678" to dump a color in all at on=
ce?
>=20
No, that is what the rgb_32 member is for: rgb.rgb_32=3D0x12345678;

A uinon means that all the members in it shares the same memory. So
the address of rgb.rgb_32 is the same as the address for rgb.col. The
union only has two members, rgb_32 and the col struct.

You can also do:

typedef struct {
  uint8_t red:8;
  uint8_t green:8;
  uint8_t blue:8;
  uint8_t pad:8;
}COL;

typedef union {
  uint32_t rgb_32;
  COL col;
}RGB;

Which more clearly shows that the union has two members.

/Ruben
--=20
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