21. Replace Bit Field in a 32-bit Register

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

uint32_t replace_field(uint32_t reg, uint32_t val, uint8_t pos, uint8_t len) {
    uint32_t msk = 0x0000;
    uint32_t tempval = 0;
    int i = pos;
    while(i < (pos + len))
    {
        msk |= (1 << i);
        i++;
    }
    tempval = (reg & (~msk));
    reg = tempval | (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;
}