Thread: bit fields and union

Hi everyone,

Just a quick question. If I make my code like this:

Code:

typedef struct{
     unsigned long btfd1:8;
     unsigned long btfd2:8;
     unsigned long btfd3:8;
     unsigned long btfd4:8;
} a;

typedef union{
     a union_btfd;
     unsigned long con; 
} b;

int main(void)
{
     
     ...

     a structBT;
     b hold;
     b temp;

     hold.union_btfd = structBT;
     temp.con = htonl(hold.con);
     structBT = temp.union_btfd;

     return 0;
}

Would this actually work as I think it will? Meaning will the union also apply the htonl() function to struct a? I tried it but I'm still not so sure if I'm correct.

Thanks.

Thanks matsp.

I knew it was too easy to work. I was really hoping for a work around using htonl() and etc but from what I understand it converts by blocks rather than converting bit by bit (kindly correct me if I'm wrong).

Actually, that is exactly my problem with the bit fields I have, they have varying bit field widths. So, just a confirmation, is there no work around to my problem? And do I have to extract and rearrange the bit fields bit by bit so to speak?

Again thanks.

Okay, will try what you suggested.

Kind of weird to ask for a confirmation but I really wanted to be sure. You see I'm working on a porting project that states in its documents that I should use htonl() on the bit fields in order to convert it. But, as you now know, I wasn't too keen that it was possible. At least now, I've got another's opinion.

Thanks.