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
    int mask;
    int i;

    mask = 0;
    for (i=0; i < len; i++) {
        mask = (mask | (1 << (pos + i)));
    }
    mask = mask ^ 0xFFFFFFFF; // create the patch
    reg= reg & mask;          // doing AND to clear patch
    val = (val << pos);       // get the patch into place
    reg= (reg | val);		  // final value

    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

Create a mask of all 1s except in the desired patch where it is all zeroes

then do a bitwise AND with the register to preserve all bits other than the patch

then left shift the val to position and bitwise OR it with the reg