C - operations on bits representing a structure

Question

I'm trying to write hashset in C, and I've found one hash function, that hashes according to bits in data. I have the following structure:

struct triple
{
    int a;
    int b;
    int c;
};

The question is - how to get bit representation from object of type struct triple? Let's say I want to XOR its bits with 8-bit integer. How would I do that?

Answer 1

Iterate over all the bytes of the struct and XOR each one individually, e.g.,

void bytexor(unsigned char xor_byte, void *data, size_t size) {
    unsigned char *p = data;
    while (size--) {
        *p++ ^= xor_byte;
    }
}

Usage would be:

struct triple my_struct;
// ...
bytexor(0xFF, &my_struct, sizeof my_struct);

(Note: This answers the question of how to XOR the struct with a byte. As for implementing a general hash function based on this, it may not be a particularly good idea since a struct may have padding, i.e., extra bytes with potentially non-deterministic values unrelated to the values of the actual payload fields.)