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 i=(1<<31);
    uint32_t j=0xffffffff;
    val|=(i>>(31-len));
    reg&=(val<<pos);
    if(pos!=0)
    reg|=(j>>(32-pos));
    else
    return reg;
    
    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;
}