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) {
    uint8_t high = pos + len - 1;
    uint8_t BITS_32BIT_SHIFT = 31;
    uint32_t mask = (1 << BITS_32BIT_SHIFT) | ((1 << BITS_32BIT_SHIFT) - 1);

    reg = reg | ((mask >> (BITS_32BIT_SHIFT - high)) - ((1 << pos) - 1));

    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