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) {
    // Your code here
    // pos 4 and len = 4
    // reg = 0xaabbccdd; //value = 0x11442233 ==> reg = 0xaabbcc3d
    int mask = ((1 << len) -1) << pos ;
    reg = (reg & ~ mask) | ((val & ((1U<<len)-1))<<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;
}