77. Validate Configuration Register Layout

#include <stdio.h>

typedef struct {
    unsigned short reg;
} ConfigRegister;

int validate_config(ConfigRegister *cfg) {
    unsigned short value = cfg->reg;
    if(value == 0x0000) return 0; //Bit 0 is disabled
    if(((value>>2) & 3) == 0x0003) return 0; //Invalid priority
    if((value>>4)&0x0FFF != 0x0000) return 0; //Invalid reserved bits;
    return 1;
}

int main() {
    ConfigRegister cfg;
    scanf("%hx", &cfg.reg);

    int result = validate_config(&cfg);
    printf("%d", result);

    return 0;
}