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

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

uint16_t clear_range(uint16_t reg, uint8_t start, uint8_t end) {
    uint16_t mask = 0x0000;
    for (uint8_t i = start; i <= end; i++) {
        mask |= (1U << i);
    }
    reg &= ~mask;
    return reg;
}

uint16_t extract_field(uint16_t reg, uint8_t pos, uint8_t len) {
    reg = clear_range(reg >>= pos, len, 31);
    return reg;
}

uint16_t replace_field(uint16_t reg, uint16_t val, uint8_t pos, uint8_t len) {
    // Your code here
    
    /*clear range "len" starting from "pos" position in "reg"*/
    reg = clear_range(reg, pos, pos + len - 1);

    /*clear "val" except first "len" bits*/
    uint16_t masked_val = extract_field(val, 0, len);

    /*replace_field*/
    reg |= (masked_val << pos);
    return reg;
}

uint16_t pack_register(uint8_t mode, uint8_t speed, uint8_t status) {
    // Your logic here
    uint16_t reg;
    reg = replace_field(reg, (uint16_t)mode, 0, 3);
    reg = replace_field(reg, (uint16_t)speed, 3, 5);
    reg = replace_field(reg, (uint16_t)status, 10, 6);
    return 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;
}