Set Specific Bits in a 32-bit Register

Code

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

uint32_t set_bits(uint32_t reg, uint8_t pos, uint8_t len) {
    // Your code here 8 - 4 = 4: 0000 1111 
    // cast = 0000 0111 << 3: 0111 1000

    //I know this is how you set 1 bit now how do I make this happen for multiple bits
    uint32_t cast = 0xFFFFFFFF >> 32 - len;
    cast = cast << pos;
    reg |= cast;

     
    return reg;
}

int main() {
    uint32_t reg;
    uint8_t pos, len;
    scanf("%u %hhu %hhu", &reg, &pos, &len);
    printf("%u", set_bits(reg, pos, len));
    return 0;
}

Solving Approach