1#ifndef _JHASH_H
2#define _JHASH_H
3
4/* jhash.h: Jenkins hash support.
5 *
6 * Copyright (C) 1996 Bob Jenkins (bob_jenkins@burtleburtle.net)
7 *
8 * http://burtleburtle.net/bob/hash/
9 *
10 * These are the credits from Bob's sources:
11 *
12 * lookup2.c, by Bob Jenkins, December 1996, Public Domain.
13 * hash(), hash2(), hash3, and mix() are externally useful functions.
14 * Routines to test the hash are included if SELF_TEST is defined.
15 * You can use this free for any purpose.  It has no warranty.
16 *
17 * $FreeBSD: releng/10.3/sys/dev/cxgb/common/jhash.h 169978 2007-05-25 09:48:20Z kmacy $
18 */
19
20/* NOTE: Arguments are modified. */
21#define __jhash_mix(a, b, c) \
22{ \
23  a -= b; a -= c; a ^= (c>>13); \
24  b -= c; b -= a; b ^= (a<<8); \
25  c -= a; c -= b; c ^= (b>>13); \
26  a -= b; a -= c; a ^= (c>>12);  \
27  b -= c; b -= a; b ^= (a<<16); \
28  c -= a; c -= b; c ^= (b>>5); \
29  a -= b; a -= c; a ^= (c>>3);  \
30  b -= c; b -= a; b ^= (a<<10); \
31  c -= a; c -= b; c ^= (b>>15); \
32}
33
34/* The golden ration: an arbitrary value */
35#define JHASH_GOLDEN_RATIO	0x9e3779b9
36
37/* The most generic version, hashes an arbitrary sequence
38 * of bytes.  No alignment or length assumptions are made about
39 * the input key.
40 */
41static inline u32 jhash(const void *key, u32 length, u32 initval)
42{
43	u32 a, b, c, len;
44	const u8 *k = key;
45
46	len = length;
47	a = b = JHASH_GOLDEN_RATIO;
48	c = initval;
49
50	while (len >= 12) {
51		a += (k[0] +((u32)k[1]<<8) +((u32)k[2]<<16) +((u32)k[3]<<24));
52		b += (k[4] +((u32)k[5]<<8) +((u32)k[6]<<16) +((u32)k[7]<<24));
53		c += (k[8] +((u32)k[9]<<8) +((u32)k[10]<<16)+((u32)k[11]<<24));
54
55		__jhash_mix(a,b,c);
56
57		k += 12;
58		len -= 12;
59	}
60
61	c += length;
62	switch (len) {
63	case 11: c += ((u32)k[10]<<24);
64	case 10: c += ((u32)k[9]<<16);
65	case 9 : c += ((u32)k[8]<<8);
66	case 8 : b += ((u32)k[7]<<24);
67	case 7 : b += ((u32)k[6]<<16);
68	case 6 : b += ((u32)k[5]<<8);
69	case 5 : b += k[4];
70	case 4 : a += ((u32)k[3]<<24);
71	case 3 : a += ((u32)k[2]<<16);
72	case 2 : a += ((u32)k[1]<<8);
73	case 1 : a += k[0];
74	};
75
76	__jhash_mix(a,b,c);
77
78	return c;
79}
80
81/* A special optimized version that handles 1 or more of u32s.
82 * The length parameter here is the number of u32s in the key.
83 */
84static inline u32 jhash2(u32 *k, u32 length, u32 initval)
85{
86	u32 a, b, c, len;
87
88	a = b = JHASH_GOLDEN_RATIO;
89	c = initval;
90	len = length;
91
92	while (len >= 3) {
93		a += k[0];
94		b += k[1];
95		c += k[2];
96		__jhash_mix(a, b, c);
97		k += 3; len -= 3;
98	}
99
100	c += length * 4;
101
102	switch (len) {
103	case 2 : b += k[1];
104	case 1 : a += k[0];
105	};
106
107	__jhash_mix(a,b,c);
108
109	return c;
110}
111
112
113/* A special ultra-optimized versions that knows they are hashing exactly
114 * 3, 2 or 1 word(s).
115 *
116 * NOTE: In partilar the "c += length; __jhash_mix(a,b,c);" normally
117 *       done at the end is not done here.
118 */
119static inline u32 jhash_3words(u32 a, u32 b, u32 c, u32 initval)
120{
121	a += JHASH_GOLDEN_RATIO;
122	b += JHASH_GOLDEN_RATIO;
123	c += initval;
124
125	__jhash_mix(a, b, c);
126
127	return c;
128}
129
130static inline u32 jhash_2words(u32 a, u32 b, u32 initval)
131{
132	return jhash_3words(a, b, 0, initval);
133}
134
135static inline u32 jhash_1word(u32 a, u32 initval)
136{
137	return jhash_3words(a, 0, 0, initval);
138}
139
140#endif /* _JHASH_H */
141