bit_twiddling.h

#include <assert.h>
#include <stdint.h>


/* boolean value */
#define BIT_IS_SET(VAL, POS) \
    ((VAL >> (POS)) & 1)


/* unsigned number */
#define BITCOUNT(VAL) \
    (sizeof(VAL) * 8)


/* function-like macros */

#define SET_BIT(VAL, POS) \
    do { \
        assert((POS) < BITCOUNT(VAL)); \
        VAL |= (1 << (POS)); \
    } while(0)


#define UNSET_BIT(VAL, POS) \
    do { \
        assert((POS) < BITCOUNT(VAL)); \
        VAL ^= (1 << (POS)); \
    } while(0)


#define INVERT_ALL_BITS(VAL) \
    do { VAL = ~VAL; } while(0)


#define INVERT_BIT(VAL, POS) \
    do { \
        if (BIT_IS_SET(VAL, (POS))) { \
            UNSET_BIT(VAL, (POS)); \
        } else { \
            SET_BIT(VAL, (POS)); \
        } \
    } while(0)


#define BITS_TO_STRING(FLAGS) \
    bits_to_string(FLAGS, BITCOUNT(FLAGS))


static inline const char *bits_to_string(uint64_t flags, uint8_t size)
{
    static char buf[65] = {0};

    assert(size <= 64);

    for (uint8_t i = size; i > 0; --i, flags >>= 1) {
        buf[i-1] = (flags & 1) ? '1' : '0';
    }

    return buf;
}