Replace Bit Field in a 32-bit Register

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

//0000 1111 reg
//0000 0010 val
//0000 0100 shifted val
//0000 0110 mask
//1111 1001 inverted mask
//1111 1101 temp = shifted val + inverted mask
//0000 1101 result = temp & reg

//1111 1111 reg
//0000 0000 val
//0000 0000 shifted val
//1111 0000 mask
//0000 1111 inverted mask
//0000 1111 temp = shifted val + inverted mask
//0000 1111 result = temp & reg

//0000 1111 reg
//0000 0010 val
//0000 0100 shifted val
//0000 0110 mask
//1111 1001 inverted mask
//1111 1101 temp = shifted val + inverted mask
//0000 1101 result = temp & reg

uint32_t replace_field(uint32_t reg, uint32_t val, uint8_t pos, uint8_t len) {
    // Your code here
    val=val<<pos;
    uint32_t mask = ((1<<len)-1)<<pos;
    mask = ~mask;
    val=val|mask;
    reg=reg&val;
    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;
}