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      1 /* $OpenBSD: ohash_lookup_interval.c,v 1.3 2006/01/16 15:52:25 espie Exp $ */
      2 /* ex:ts=8 sw=4:
      3  */
      4 
      5 /* Copyright (c) 1999, 2004 Marc Espie <espie (at) openbsd.org>
      6  *
      7  * Permission to use, copy, modify, and distribute this software for any
      8  * purpose with or without fee is hereby granted, provided that the above
      9  * copyright notice and this permission notice appear in all copies.
     10  *
     11  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
     12  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
     13  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
     14  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
     15  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
     16  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
     17  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
     18  */
     19 
     20 #include "ohash_int.h"
     21 
     22 unsigned int
     23 ohash_lookup_interval(struct ohash *h, const char *start, const char *end,
     24     uint32_t hv)
     25 {
     26 	unsigned int 	i, incr;
     27 	unsigned int	empty;
     28 
     29 #ifdef STATS_HASH
     30 	STAT_HASH_LOOKUP++;
     31 #endif
     32 	empty = NONE;
     33 	i = hv % h->size;
     34 	incr = ((hv % (h->size-2)) & ~1) + 1;
     35 	while (h->t[i].p != NULL) {
     36 #ifdef STATS_HASH
     37 		STAT_HASH_LENGTH++;
     38 #endif
     39 		if (h->t[i].p == DELETED) {
     40 			if (empty == NONE)
     41 				empty = i;
     42 		} else if (h->t[i].hv == hv &&
     43 		    strncmp(h->t[i].p+h->info.key_offset, start,
     44 		    	end - start) == 0 &&
     45 		    (h->t[i].p+h->info.key_offset)[end-start] == '\0') {
     46 		    	if (empty != NONE) {
     47 				h->t[empty].hv = hv;
     48 				h->t[empty].p = h->t[i].p;
     49 				h->t[i].p = DELETED;
     50 				return empty;
     51 			} else {
     52 #ifdef STATS_HASH
     53 				STAT_HASH_POSITIVE++;
     54 #endif
     55 				return i;
     56 			}
     57 		}
     58 		i += incr;
     59 		if (i >= h->size)
     60 			i -= h->size;
     61 	}
     62 
     63 	/* Found an empty position.  */
     64 	if (empty != NONE)
     65 		i = empty;
     66 	h->t[i].hv = hv;
     67 	return i;
     68 }
     69