21. Replace Bit Field in a 32-bit Register

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

uint32_t clear_range(uint32_t reg, uint8_t start, uint8_t end) {
    uint32_t mask = 0x00000000;
    for (uint8_t i = start; i <= end; i++) {
        mask |= (1U << i);
    }
    reg &= ~mask;
    return reg;
}

uint32_t extract_field(uint32_t reg, uint8_t pos, uint8_t len) {
    reg = clear_range(reg >>= pos, len, 31);
    return reg;
}

uint32_t replace_field(uint32_t reg, uint32_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*/
    uint32_t masked_val = extract_field(val, 0, len);

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

int main() {
    uint32_t reg, val;
    uint8_t pos, len;
    scanf("%u %u %hhu %hhu", &reg, &val, &pos, &len);
    printf("%u", replace_field(reg, val, pos, len));
    return 0;
}