25. Pack Multiple Fields into a 16-bit Control Register

#include <stdio.h>
#include <stdint.h>

typedef union{
    uint16_t reg;

    struct{
        uint16_t mode:     3;
        uint16_t speed:    5;
        uint16_t reserved: 2;
        uint16_t status:   6;
    }reg_t;
}CTRL_REG_t;

uint16_t pack_register(uint8_t mode, uint8_t speed, uint8_t status) {
    CTRL_REG_t control_register = {0};
    control_register.reg_t.mode = mode;
    control_register.reg_t.speed = speed;
    control_register.reg_t.status = status;

    return control_register.reg;
    
}

int main() {
    uint8_t mode, speed, status;
    scanf("%hhu %hhu %hhu", &mode, &speed, &status);

    uint16_t reg = pack_register(mode, speed, status);
    printf("%u", reg);
    return 0;
}