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
18 /* NOTE: Arguments are modified. */
19 #define __jhash_mix(a, b, c) \
20 { \
21 a -= b; a -= c; a ^= (c>>13); \
22 b -= c; b -= a; b ^= (a<<8); \
23 c -= a; c -= b; c ^= (b>>13); \
24 a -= b; a -= c; a ^= (c>>12); \
25 b -= c; b -= a; b ^= (a<<16); \
26 c -= a; c -= b; c ^= (b>>5); \
27 a -= b; a -= c; a ^= (c>>3); \
28 b -= c; b -= a; b ^= (a<<10); \
29 c -= a; c -= b; c ^= (b>>15); \
30 }
31
32 /* The golden ration: an arbitrary value */
33 #define JHASH_GOLDEN_RATIO 0x9e3779b9
34
35 /* The most generic version, hashes an arbitrary sequence
36 * of bytes. No alignment or length assumptions are made about
37 * the input key.
38 */
jhash(const void * key,u32 length,u32 initval)39 static inline u32 jhash(const void *key, u32 length, u32 initval)
40 {
41 u32 a, b, c, len;
42 const u8 *k = key;
43
44 len = length;
45 a = b = JHASH_GOLDEN_RATIO;
46 c = initval;
47
48 while (len >= 12) {
49 a += (k[0] +((u32)k[1]<<8) +((u32)k[2]<<16) +((u32)k[3]<<24));
50 b += (k[4] +((u32)k[5]<<8) +((u32)k[6]<<16) +((u32)k[7]<<24));
51 c += (k[8] +((u32)k[9]<<8) +((u32)k[10]<<16)+((u32)k[11]<<24));
52
53 __jhash_mix(a,b,c);
54
55 k += 12;
56 len -= 12;
57 }
58
59 c += length;
60 switch (len) {
61 case 11: c += ((u32)k[10]<<24);
62 case 10: c += ((u32)k[9]<<16);
63 case 9 : c += ((u32)k[8]<<8);
64 case 8 : b += ((u32)k[7]<<24);
65 case 7 : b += ((u32)k[6]<<16);
66 case 6 : b += ((u32)k[5]<<8);
67 case 5 : b += k[4];
68 case 4 : a += ((u32)k[3]<<24);
69 case 3 : a += ((u32)k[2]<<16);
70 case 2 : a += ((u32)k[1]<<8);
71 case 1 : a += k[0];
72 };
73
74 __jhash_mix(a,b,c);
75
76 return c;
77 }
78
79 /* A special optimized version that handles 1 or more of u32s.
80 * The length parameter here is the number of u32s in the key.
81 */
jhash2(u32 * k,u32 length,u32 initval)82 static inline u32 jhash2(u32 *k, u32 length, u32 initval)
83 {
84 u32 a, b, c, len;
85
86 a = b = JHASH_GOLDEN_RATIO;
87 c = initval;
88 len = length;
89
90 while (len >= 3) {
91 a += k[0];
92 b += k[1];
93 c += k[2];
94 __jhash_mix(a, b, c);
95 k += 3; len -= 3;
96 }
97
98 c += length * 4;
99
100 switch (len) {
101 case 2 : b += k[1];
102 case 1 : a += k[0];
103 };
104
105 __jhash_mix(a,b,c);
106
107 return c;
108 }
109
110
111 /* A special ultra-optimized versions that knows they are hashing exactly
112 * 3, 2 or 1 word(s).
113 *
114 * NOTE: In partilar the "c += length; __jhash_mix(a,b,c);" normally
115 * done at the end is not done here.
116 */
jhash_3words(u32 a,u32 b,u32 c,u32 initval)117 static inline u32 jhash_3words(u32 a, u32 b, u32 c, u32 initval)
118 {
119 a += JHASH_GOLDEN_RATIO;
120 b += JHASH_GOLDEN_RATIO;
121 c += initval;
122
123 __jhash_mix(a, b, c);
124
125 return c;
126 }
127
jhash_2words(u32 a,u32 b,u32 initval)128 static inline u32 jhash_2words(u32 a, u32 b, u32 initval)
129 {
130 return jhash_3words(a, b, 0, initval);
131 }
132
jhash_1word(u32 a,u32 initval)133 static inline u32 jhash_1word(u32 a, u32 initval)
134 {
135 return jhash_3words(a, 0, 0, initval);
136 }
137
138 #endif /* _JHASH_H */
139