Bitfields in C

bitfield.c

/* Some simple demonstration code to show the use of bit fields in C */

#include <stdio.h>

typedef struct {
        unsigned int s0 : 1;
        unsigned int s1 : 1;
        unsigned int s2 : 1;
        unsigned int s3 : 1;
        unsigned int s4 : 1;
        unsigned int s5 : 1;
        unsigned int s6 : 1;
        unsigned int s7 : 1;
} sensor;

/* Simple inline functions to work on the bitfields */
inline void sns_init(sensor *s)
{
        s->s0 = 0; s->s1 = 0; s->s2 = 0; s->s3 = 0;
        s->s4 = 0; s->s5 = 0; s->s6 = 0; s->s7 = 0;
}

inline unsigned int sns_and(sensor s)
{
        return s.s0 & s.s1 & s.s2 & s.s3 &s.s4 & s.s5 & s.s6 & s.s7;
}

inline unsigned int sns_or(sensor s)
{
        return s.s0 | s.s1 | s.s2 | s.s3 |s.s4 | s.s5 | s.s6 | s.s7;
}

inline void sns_print(sensor s)
{
        printf("Sensor values are:\n");
        printf("%d %d %d %d %d %d %d %d\n",
               s.s0, s.s1, s.s2, s.s3,s.s4, s.s5, s.s6, s.s7);
}

int sns_changed(sensor sense, sensor changed)
{

        /* Has anything changed since initialization? */
        if (sns_or(changed)) {
                printf("Sensor values changed\n");
                sns_print(sense);
                return 1;
        } else {
                printf("No sensor values changed\n");
                return 0;
        }
}

/* A little example */
void main()
{
        sensor sense;
        sensor changed;

        sns_init(&sense);
        sns_init(&changed);

        printf("Size of a sensor type is %d\n", sizeof(sensor));
        sns_print(sense);

        /* Let's change something */
        sense.s1 = 1; sense.s3 = 1; sense.s6 = 1;
        changed.s1 = 1; changed.s3 = 1; changed.s6 = 1;

        if (sns_changed(sense, changed)) {
                sns_init(&changed);
        }

        sense.s2 = 1; sense.s3 = 0; sense.s4 = 1;
        changed.s2 = 1; changed.s3 = 1; changed.s4 = 1;

        if (sns_changed(sense, changed)) {
                sns_init(&changed);
        }
}