Re: Help on bit operation

[Ben Rosenberg <scdlbx@gmail.com>]

On Thu, Aug 27, 2009 at 9:52 PM, Randi Botse<nightdecoder@gmail.com> wrote:
> Hi again.
>
> I was able to solve my bit packing/unpacking problems with bit mask
> and shift operations, but i have no idea how to do this using a
> bit-field structure, can someone give me a example?
>
> Thanks
>             - Randi
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Glynn's example of bitfields is cleaner and better than this, but I
put a basic implementation of bitfields using your parameters at the
end of this message. From my understanding, the way bitfields are
implemented in C is with bit shifts and masks, so I don't think there
is a performance difference between the two.

#include <stdio.h>

struct bitfield {
    unsigned int a:6;
    unsigned int b:4;
    unsigned int c:8;
    unsigned int d:5;
    unsigned int e:9;
};

int main(void) {
    struct bitfield foo;
    foo.a =  43;
    foo.b =  11;
    foo.c = 120;
    foo.d =  30;
    foo.e = 418;
    printf("%u %u %u %u %u\n",foo.a,foo.b,foo.c,foo.d,foo.e);
    return 0;
}


Ben
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