1/* Licensed to the Apache Software Foundation (ASF) under one or more
2 * contributor license agreements.  See the NOTICE file distributed with
3 * this work for additional information regarding copyright ownership.
4 * The ASF licenses this file to You under the Apache License, Version 2.0
5 * (the "License"); you may not use this file except in compliance with
6 * the License.  You may obtain a copy of the License at
7 *
8 *     http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17/*
18 * sdbm - ndbm work-alike hashed database library
19 * based on Per-Aake Larson's Dynamic Hashing algorithms. BIT 18 (1978).
20 * author: oz@nexus.yorku.ca
21 * status: ex-public domain. keep it that way.
22 *
23 * hashing routine
24 */
25
26#include "apr_sdbm.h"
27#include "sdbm_private.h"
28
29/*
30 * polynomial conversion ignoring overflows
31 * [this seems to work remarkably well, in fact better
32 * then the ndbm hash function. Replace at your own risk]
33 * use: 65599	nice.
34 *      65587   even better.
35 */
36long sdbm_hash(const char *str, int len)
37{
38	register unsigned long n = 0;
39
40#define DUFF	/* go ahead and use the loop-unrolled version */
41#ifdef DUFF
42
43#define HASHC	n = *str++ + 65599 * n
44
45	if (len > 0) {
46		register int loop = (len + 8 - 1) >> 3;
47
48		switch(len & (8 - 1)) {
49		case 0:	do {
50			HASHC;	case 7:	HASHC;
51		case 6:	HASHC;	case 5:	HASHC;
52		case 4:	HASHC;	case 3:	HASHC;
53		case 2:	HASHC;	case 1:	HASHC;
54			} while (--loop);
55		}
56
57	}
58#else
59	while (len--)
60		n = *str++ + 65599 * n;
61#endif
62	return n;
63}
64