Control Register Using Nested Bitfields

Code

#include <stdio.h>

typedef union {
    unsigned char reg;
    struct {
        unsigned char enable : 1;
        unsigned char mode : 1;
        unsigned char priority : 2;
        unsigned char reserved : 4;
    } bits;
} ControlRegister;


    int validate_register(ControlRegister *ctrl) {
    if (ctrl->bits.enable != 1)
        return 0;
    if (ctrl->bits.priority > 2)
        return 0;
    if (ctrl->bits.reserved != 0)
        return 0;

    return 1;
}



int main() {
    ControlRegister ctrl;
    scanf("%hhx", &ctrl.reg);

    int result = validate_register(&ctrl);
    printf("%d", result);

    return 0;
}

Solving Approach