Bit set data structure (C99)

bitset.c

/**
 * @file bitset.c
 * @brief Implementation of a bit set data structure.
 */

#include <stdlib.h>
#include <assert.h>

#include "bitset.h"


static inline unsigned int num_chunks(size_t length)
{
        div_t d = div((int) length, UINT_BITS);
        return (unsigned int) (d.rem == 0 ? d.quot : d.quot+1);
}

struct bitset *new_bitset(size_t length)
{
	struct bitset *b;
        size_t total_size;

        if (length == 0)
                return NULL;

        total_size = sizeof(struct bitset) + num_chunks(length)*sizeof(unsigned);

        if ((b = calloc(1, total_size)) == NULL)
		return NULL;

	b->length = length;

	return b;
}

void delete_bitset(struct bitset *self)
{
	assert(self);

	free(self);
}

bitset.h

#ifndef BITSET_H
#define BITSET_H
/**
 * @file bitset.h
 * @brief Interface to the bitset data structure.
 */

#include <stdlib.h>
#include <limits.h>


#define UINT_BITS        sizeof(unsigned)*CHAR_BIT


/**
 * Bitset data structure.
 */
struct bitset {
	size_t length;          /**< Length in bits. */
	unsigned chunk[];       /**< Storage for the set. */
};


extern struct bitset *new_bitset(size_t length);

extern void delete_bitset(struct bitset *self);

static inline void bitset_set(struct bitset *self, int index)
{
        div_t d = div(index, UINT_BITS);
        self->chunk[d.quot] |= (1 << (unsigned) d.rem);
}

static inline int bitset_get(const struct bitset *self, int index)
{
        div_t d = div(index, UINT_BITS);
        return (self->chunk[d.quot] >> (unsigned) d.rem) & 1;
}

static inline void bitset_clear(struct bitset *self, int index)
{
        div_t d = div(index, UINT_BITS);
        self->chunk[d.quot] &= ~(1 << (unsigned) d.rem);
}
#endif // !BITSET_H