Replace Bit Field in a 32-bit Register

Code

#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<pos+len; i++){
        uint32_t reg_new=0;
        reg_new |= (val & (1<<j)) ;
        if(reg_new ==0){
            reg &= ~((1<<i));
        }
        else{
            reg |=  (1<<i);
        }
        //printf("1: %d \n",reg_new);
        //printf("2: %d \n",reg);
        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;
}

Solving Approach