[Solved]What is the meaning of this syntax?

[stereomatching]

@
struct Private
{
inline Private(): type(Invalid), is_shared(false), is_null(true) { data.ptr = 0; }
inline Private(const Private &other)
: data(other.data), type(other.type),
is_shared(other.is_shared), is_null(other.is_null)
{}
union Data
{
char c;
int i;
uint u;
bool b;
double d;
float f;
qreal real;
qlonglong ll;
qulonglong ull;
QObject *o;
void *ptr;
PrivateShared *shared;
} data;
uint type : 30;
uint is_shared : 1;
uint is_null : 1;
};
@

some codes from QVariant, I have no idea what is the meaning of

@
uint type : 30;
uint is_shared : 1;
uint is_null : 1;
@

Thanks

[hpollak]

Looks like definition of BIT-Fields

See:

"Wikipedia":http://en.wikipedia.org/wiki/C++_classes

scroll down to BIT Fields.

So this means this 3 vars uses together 32Bit :

type use 30 Bits
is_shared use 1 Bit
is_null use 1 Bit

if the definition is without bit fields than:

32 Bits for type
32 Bits for is_shared and
32 Bits for is_null

[stereomatching]

Thanks, I learn one more thing.