Open addressing, linear probing hash table

hash.c

#include "hash.h"
#include <assert.h>

void **hash_find(void **base, size_t n, void *key,
	size_t hash, int (*equal)(const void *, const void *))
{
	void **p, **q, **end;

	p = q = base + hash % n;
	end = base + n;
	while (*p && !(*equal)(key, *p))
		if (++p == end)
			p = base;
		else
			assert(p != q);
	return p;
}

void hash_del(void **base, size_t n, void **p,
	size_t (*hasher)(const void *))
{
	void **q, **r, **end;

	q = p;
	end = base + n;
erase:
	*p = NULL;
	for (;;) {
		if (++q == end)
			q = base;
		if (*q == NULL)
			break;
		r = base + (*hasher)(*q) % n;
		if ((r <= p) + (q < r) + (p < q) == 2) {
			*p = *q;
			p = q;
			goto erase;
		}
	}
}

void hash_copy(void **dst, size_t ndst, void **src, size_t nsrc,
	size_t (*hasher)(const void *))
{
	void **p, **end;

	end = dst + ndst;
	assert(dst != src);
	for (; nsrc--; src++) {
		if (*src) {
			p = dst + (*hasher)(*src) % ndst;
			while (*p)
				if (++p == end)
					p = dst;
			*p = *src;
		}
	}
}

hash.h

/*
 * Hash Table
 */

#ifndef HASH_H
#define HASH_H

#include <stddef.h>

extern void **hash_find(void **base, size_t n, void *key,
	size_t hash, int (*equal)(const void *, const void *));
extern void hash_del(void **base, size_t n, void **p,
	size_t (*hasher)(const void *));
extern void hash_copy(void **dst, size_t ndst, void **src, size_t nsrc,
	size_t (*hasher)(const void *));

#endif /* HASH_H */