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) {
    unsigned int reg_val;
    int mask = 0;
    for(int i = pos; i<pos+len; i++)
    {
        mask |= (1 << i);
    }
    reg_val = (reg & ~mask);
    reg_val = reg_val | (val << pos);
    return reg_val;
}

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;
}