Writing C readable bitfield structs?

[phark52 at yahoo.com]

Roy Smith wrote:
> In article <1111002678.866378.102970 at l41g2000cwc.googlegroups.com>,
> Cappy2112 <cappy2112 at gmail.com> wrote:
> >there is a bitfiled mainpulator class inthe Cookbook, but I don't
> >understand his explanation, and the example given doesn't really
show
> >off the features of the class.
>
> I assume you're talking about the struct module?  If you give an
> example of the C struct you're trying to read/write, I could come up
> with some sample code to do it.

struct S {
    unsigned int a : 1;
    unsigned int b : 1;
    unsigned int c : 1;
    unsigned int d : 1;
};

fread(from file (file written by Python app) into an instance of struct
S)
then I want it to be used as follows:
if (instance.a) f();
if (instance.b) g();
struct S comes out to 4 on my arch. I do not want to use a new int for
every member of struct S.