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1 | #ifndef _LINUX_JHASH_H |
2 | #define _LINUX_JHASH_H |
3 | |
4 | /* jhash.h: Jenkins hash support. |
5 | * |
6 | * Copyright (C) 2006. 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 | * lookup3.c, by Bob Jenkins, May 2006, Public Domain. |
13 | * |
14 | * These are functions for producing 32-bit hashes for hash table lookup. |
15 | * hashword(), hashlittle(), hashlittle2(), hashbig(), mix(), and final() |
16 | * are externally useful functions. Routines to test the hash are included |
17 | * if SELF_TEST is defined. You can use this free for any purpose. It's in |
18 | * the public domain. It has no warranty. |
19 | * |
20 | * Copyright (C) 2009-2010 Jozsef Kadlecsik (kadlec@blackhole.kfki.hu) |
21 | * |
22 | * I've modified Bob's hash to be useful in the Linux kernel, and |
23 | * any bugs present are my fault. |
24 | * Jozsef |
25 | */ |
26 | #include <linux/bitops.h> |
27 | #include <linux/unaligned/packed_struct.h> |
28 | |
29 | /* Best hash sizes are of power of two */ |
30 | #define jhash_size(n) ((u32)1<<(n)) |
31 | /* Mask the hash value, i.e (value & jhash_mask(n)) instead of (value % n) */ |
32 | #define jhash_mask(n) (jhash_size(n)-1) |
33 | |
34 | /* __jhash_mix -- mix 3 32-bit values reversibly. */ |
35 | #define __jhash_mix(a, b, c) \ |
36 | { \ |
37 | a -= c; a ^= rol32(c, 4); c += b; \ |
38 | b -= a; b ^= rol32(a, 6); a += c; \ |
39 | c -= b; c ^= rol32(b, 8); b += a; \ |
40 | a -= c; a ^= rol32(c, 16); c += b; \ |
41 | b -= a; b ^= rol32(a, 19); a += c; \ |
42 | c -= b; c ^= rol32(b, 4); b += a; \ |
43 | } |
44 | |
45 | /* __jhash_final - final mixing of 3 32-bit values (a,b,c) into c */ |
46 | #define __jhash_final(a, b, c) \ |
47 | { \ |
48 | c ^= b; c -= rol32(b, 14); \ |
49 | a ^= c; a -= rol32(c, 11); \ |
50 | b ^= a; b -= rol32(a, 25); \ |
51 | c ^= b; c -= rol32(b, 16); \ |
52 | a ^= c; a -= rol32(c, 4); \ |
53 | b ^= a; b -= rol32(a, 14); \ |
54 | c ^= b; c -= rol32(b, 24); \ |
55 | } |
56 | |
57 | /* An arbitrary initial parameter */ |
58 | #define JHASH_INITVAL 0xdeadbeef |
59 | |
60 | /* jhash - hash an arbitrary key |
61 | * @k: sequence of bytes as key |
62 | * @length: the length of the key |
63 | * @initval: the previous hash, or an arbitray value |
64 | * |
65 | * The generic version, hashes an arbitrary sequence of bytes. |
66 | * No alignment or length assumptions are made about the input key. |
67 | * |
68 | * Returns the hash value of the key. The result depends on endianness. |
69 | */ |
70 | static inline u32 jhash(const void *key, u32 length, u32 initval) |
71 | { |
72 | u32 a, b, c; |
73 | const u8 *k = key; |
74 | |
75 | /* Set up the internal state */ |
76 | a = b = c = JHASH_INITVAL + length + initval; |
77 | |
78 | /* All but the last block: affect some 32 bits of (a,b,c) */ |
79 | while (length > 12) { |
80 | a += __get_unaligned_cpu32(k); |
81 | b += __get_unaligned_cpu32(k + 4); |
82 | c += __get_unaligned_cpu32(k + 8); |
83 | __jhash_mix(a, b, c); |
84 | length -= 12; |
85 | k += 12; |
86 | } |
87 | /* Last block: affect all 32 bits of (c) */ |
88 | /* All the case statements fall through */ |
89 | switch (length) { |
90 | case 12: c += (u32)k[11]<<24; |
91 | case 11: c += (u32)k[10]<<16; |
92 | case 10: c += (u32)k[9]<<8; |
93 | case 9: c += k[8]; |
94 | case 8: b += (u32)k[7]<<24; |
95 | case 7: b += (u32)k[6]<<16; |
96 | case 6: b += (u32)k[5]<<8; |
97 | case 5: b += k[4]; |
98 | case 4: a += (u32)k[3]<<24; |
99 | case 3: a += (u32)k[2]<<16; |
100 | case 2: a += (u32)k[1]<<8; |
101 | case 1: a += k[0]; |
102 | __jhash_final(a, b, c); |
103 | case 0: /* Nothing left to add */ |
104 | break; |
105 | } |
106 | |
107 | return c; |
108 | } |
109 | |
110 | /* jhash2 - hash an array of u32's |
111 | * @k: the key which must be an array of u32's |
112 | * @length: the number of u32's in the key |
113 | * @initval: the previous hash, or an arbitray value |
114 | * |
115 | * Returns the hash value of the key. |
116 | */ |
117 | static inline u32 jhash2(const u32 *k, u32 length, u32 initval) |
118 | { |
119 | u32 a, b, c; |
120 | |
121 | /* Set up the internal state */ |
122 | a = b = c = JHASH_INITVAL + (length<<2) + initval; |
123 | |
124 | /* Handle most of the key */ |
125 | while (length > 3) { |
126 | a += k[0]; |
127 | b += k[1]; |
128 | c += k[2]; |
129 | __jhash_mix(a, b, c); |
130 | length -= 3; |
131 | k += 3; |
132 | } |
133 | |
134 | /* Handle the last 3 u32's: all the case statements fall through */ |
135 | switch (length) { |
136 | case 3: c += k[2]; |
137 | case 2: b += k[1]; |
138 | case 1: a += k[0]; |
139 | __jhash_final(a, b, c); |
140 | case 0: /* Nothing left to add */ |
141 | break; |
142 | } |
143 | |
144 | return c; |
145 | } |
146 | |
147 | |
148 | /* jhash_3words - hash exactly 3, 2 or 1 word(s) */ |
149 | static inline u32 jhash_3words(u32 a, u32 b, u32 c, u32 initval) |
150 | { |
151 | a += JHASH_INITVAL; |
152 | b += JHASH_INITVAL; |
153 | c += initval; |
154 | |
155 | __jhash_final(a, b, c); |
156 | |
157 | return c; |
158 | } |
159 | |
160 | static inline u32 jhash_2words(u32 a, u32 b, u32 initval) |
161 | { |
162 | return jhash_3words(a, b, 0, initval); |
163 | } |
164 | |
165 | static inline u32 jhash_1word(u32 a, u32 initval) |
166 | { |
167 | return jhash_3words(a, 0, 0, initval); |
168 | } |
169 | |
170 | #endif /* _LINUX_JHASH_H */ |
171 |
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