Miguel Tadeu
Posts: 1
Nickname: mtadeunet
Registered: Nov, 2007
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Re: Why not C bitfields?
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Posted: Nov 12, 2007 10:36 AM
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I read a book that noted just that(can remember which), but I picked the example described there and added a few features:
// from the book
template<unsigned long N>
struct binary
{
static const unsigned int digit = N % 10;
BOOST_STATIC_ASSERT(digit == 0 || digit == 1);
static unsigned long const value = binary<N/10>::value * 2 + digit;
};
template<>
struct binary<0>
{
static unsigned int const value = 0;
};
// from me...
template<unsigned long N, unsigned long S>
struct binary_shift_left : binary<N>
{
static unsigned long const value = (binary<N>::value << S);
};
template<unsigned long N, unsigned long S>
struct binary_shift_right : binary<N>
{
static unsigned long const value = (binary<N>::value >> S);
};
template<unsigned long N, unsigned long P = 0>
struct flag : binary_shift_left<N, P> { };
template<unsigned long P>
struct bit_flag : flag<1, P>{ };
// usage
int main(int argc, char *argv[])
{
unsigned long flags = 0x00;
flags = binary<1010101010>::value;
flags |= bit_flag< 1 >::value;
flags |= bit_flag< 2 >::value;
flags |= bit_flag< 3 >::value;
flags |= bit_flag< 4 >::value;
flags |= bit_flag< 5 >::value;
flags |= bit_flag< 6 >::value;
flags |= bit_flag< 7 >::value;
flags |= bit_flag< 8 >::value;
flags |= flag<11, 9>::value | flag<101, 5>::value;
cout << binary<1111>::value << endl;
return EXIT_SUCCESS;
}
It's to be noticed that recent compilers will resolve the templates and the code remains as optimized as in C.
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