19. Extract a Bit Field from a 32-bit Register

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

uint32_t extract_field(uint32_t reg, uint8_t pos, uint8_t len) {
    if (len == 0 || pos >= 32) return 0;  // invalid case
    if (len > 32 - pos) len = 32 - pos;   // clamp to valid range

    uint32_t mask = (1u << len) - 1;      // make mask of len bits
    return (reg >> pos) & mask;           // extract
}

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