1 /* $NetBSD: hash.h,v 1.5 2021/12/19 12:02:40 riastradh Exp $ */
2
3 /*-
4 * Copyright (c) 2013 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Taylor R. Campbell.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29 * POSSIBILITY OF SUCH DAMAGE.
30 */
31
32 #ifndef _LINUX_HASH_H_
33 #define _LINUX_HASH_H_
34
35 #include <sys/param.h>
36 #include <machine/limits.h>
37
38 static inline unsigned long
hash_long(unsigned long value,unsigned int bits)39 hash_long(unsigned long value, unsigned int bits)
40 {
41 const unsigned long factor = (sizeof(factor) > 4?
42 0x9e37fffffffc0001ull : 0x9e370001ul);
43
44 return ((value * factor) >> ((CHAR_BIT * sizeof(value)) - bits));
45 }
46
47 static inline uint32_t
hash_32(uint32_t value,unsigned int bits)48 hash_32(uint32_t value, unsigned int bits)
49 {
50 return (value * 0x61c88647) >> (32 - bits);
51 }
52
53 static inline uint64_t
hash_64(uint64_t value,unsigned int bits)54 hash_64(uint64_t value, unsigned int bits)
55 {
56 return (value * 0x61c8864680b583ebull) >> (64 - bits);
57 }
58
59 #endif /* _LINUX_HASH_H_ */
60