21. Replace Bit Field in a 32-bit Register

#include <stdio.h>
#include <stdint.h>

#define MASK(BITS) ((1U << (BITS))-1)
#define SHIFT_MASK(REG, POS) ((REG) << (POS)) 


uint32_t replace_field(uint32_t reg, uint32_t val, uint8_t pos, uint8_t len) {
    // Your code here
    return (reg & ~SHIFT_MASK(MASK(len), pos)) | ((val & MASK(len)) << pos);
}

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;
}