xref: /src/usr.bin/m4/lib/ohash_lookup_interval.c

/* $OpenBSD: ohash_lookup_interval.c,v 1.3 2006/01/16 15:52:25 espie Exp $ */
/* ex:ts=8 sw=4:
 */

/* Copyright (c) 1999, 2004 Marc Espie <espie (at) openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include "ohash_int.h"

unsigned int
ohash_lookup_interval(struct ohash *h, const char *start, const char *end,
    uint32_t hv)
{
	unsigned int 	i, incr;
	unsigned int	empty;

#ifdef STATS_HASH
	STAT_HASH_LOOKUP++;
#endif
	empty = NONE;
	i = hv % h->size;
	incr = ((hv % (h->size-2)) & ~1) + 1;
	while (h->t[i].p != NULL) {
#ifdef STATS_HASH
		STAT_HASH_LENGTH++;
#endif
		if (h->t[i].p == DELETED) {
			if (empty == NONE)
				empty = i;
		} else if (h->t[i].hv == hv &&
		    strncmp(h->t[i].p+h->info.key_offset, start,
		    	end - start) == 0 &&
		    (h->t[i].p+h->info.key_offset)[end-start] == '\0') {
		    	if (empty != NONE) {
				h->t[empty].hv = hv;
				h->t[empty].p = h->t[i].p;
				h->t[i].p = DELETED;
				return empty;
			} else {
#ifdef STATS_HASH
				STAT_HASH_POSITIVE++;
#endif
				return i;
			}
		}
		i += incr;
		if (i >= h->size)
			i -= h->size;
	}

	/* Found an empty position.  */
	if (empty != NONE)
		i = empty;
	h->t[i].hv = hv;
	return i;
}