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) {
    int j=0;
    for(int i=pos;i<32;i++)
    {
        if(len<=0)
        {
            return reg;
        }
        if(val & (1<<j))
        {
            reg |=(1<<i);
        }
        else if((val & 1<<j)!=1)
        {
            reg &=~(1<<i);
        }
        --len;
        ++j;
    }
    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;
}