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1da177e4 LT |
1 | #ifndef _LINUX_JHASH_H |
2 | #define _LINUX_JHASH_H | |
3 | ||
4 | /* jhash.h: Jenkins hash support. | |
5 | * | |
60d509c8 | 6 | * Copyright (C) 2006. Bob Jenkins (bob_jenkins@burtleburtle.net) |
1da177e4 LT |
7 | * |
8 | * http://burtleburtle.net/bob/hash/ | |
9 | * | |
10 | * These are the credits from Bob's sources: | |
11 | * | |
60d509c8 | 12 | * lookup3.c, by Bob Jenkins, May 2006, Public Domain. |
1da177e4 | 13 | * |
60d509c8 JK |
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 | * | |
fe03d474 | 20 | * Copyright (C) 2009-2010 Jozsef Kadlecsik (kadlec@netfilter.org) |
1da177e4 LT |
21 | * |
22 | * I've modified Bob's hash to be useful in the Linux kernel, and | |
60d509c8 JK |
23 | * any bugs present are my fault. |
24 | * Jozsef | |
1da177e4 | 25 | */ |
60d509c8 JK |
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 | } | |
1da177e4 | 44 | |
60d509c8 JK |
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); \ | |
1da177e4 LT |
55 | } |
56 | ||
60d509c8 JK |
57 | /* An arbitrary initial parameter */ |
58 | #define JHASH_INITVAL 0xdeadbeef | |
1da177e4 | 59 | |
60d509c8 JK |
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. | |
1da177e4 LT |
69 | */ |
70 | static inline u32 jhash(const void *key, u32 length, u32 initval) | |
71 | { | |
60d509c8 | 72 | u32 a, b, c; |
1da177e4 LT |
73 | const u8 *k = key; |
74 | ||
60d509c8 JK |
75 | /* Set up the internal state */ |
76 | a = b = c = JHASH_INITVAL + length + initval; | |
1da177e4 | 77 | |
60d509c8 JK |
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; | |
1da177e4 | 85 | k += 12; |
1da177e4 | 86 | } |
60d509c8 | 87 | /* Last block: affect all 32 bits of (c) */ |
60d509c8 | 88 | switch (length) { |
13c401f3 JK |
89 | case 12: c += (u32)k[11]<<24; /* fall through */ |
90 | case 11: c += (u32)k[10]<<16; /* fall through */ | |
91 | case 10: c += (u32)k[9]<<8; /* fall through */ | |
92 | case 9: c += k[8]; /* fall through */ | |
93 | case 8: b += (u32)k[7]<<24; /* fall through */ | |
94 | case 7: b += (u32)k[6]<<16; /* fall through */ | |
95 | case 6: b += (u32)k[5]<<8; /* fall through */ | |
96 | case 5: b += k[4]; /* fall through */ | |
97 | case 4: a += (u32)k[3]<<24; /* fall through */ | |
98 | case 3: a += (u32)k[2]<<16; /* fall through */ | |
99 | case 2: a += (u32)k[1]<<8; /* fall through */ | |
60d509c8 JK |
100 | case 1: a += k[0]; |
101 | __jhash_final(a, b, c); | |
102 | case 0: /* Nothing left to add */ | |
103 | break; | |
104 | } | |
1da177e4 LT |
105 | |
106 | return c; | |
107 | } | |
108 | ||
60d509c8 JK |
109 | /* jhash2 - hash an array of u32's |
110 | * @k: the key which must be an array of u32's | |
111 | * @length: the number of u32's in the key | |
112 | * @initval: the previous hash, or an arbitray value | |
113 | * | |
114 | * Returns the hash value of the key. | |
1da177e4 | 115 | */ |
8e87e014 | 116 | static inline u32 jhash2(const u32 *k, u32 length, u32 initval) |
1da177e4 | 117 | { |
60d509c8 | 118 | u32 a, b, c; |
1da177e4 | 119 | |
60d509c8 JK |
120 | /* Set up the internal state */ |
121 | a = b = c = JHASH_INITVAL + (length<<2) + initval; | |
1da177e4 | 122 | |
60d509c8 JK |
123 | /* Handle most of the key */ |
124 | while (length > 3) { | |
1da177e4 LT |
125 | a += k[0]; |
126 | b += k[1]; | |
127 | c += k[2]; | |
128 | __jhash_mix(a, b, c); | |
60d509c8 JK |
129 | length -= 3; |
130 | k += 3; | |
1da177e4 LT |
131 | } |
132 | ||
13c401f3 | 133 | /* Handle the last 3 u32's */ |
60d509c8 | 134 | switch (length) { |
13c401f3 JK |
135 | case 3: c += k[2]; /* fall through */ |
136 | case 2: b += k[1]; /* fall through */ | |
60d509c8 JK |
137 | case 1: a += k[0]; |
138 | __jhash_final(a, b, c); | |
139 | case 0: /* Nothing left to add */ | |
140 | break; | |
141 | } | |
1da177e4 LT |
142 | |
143 | return c; | |
144 | } | |
145 | ||
146 | ||
2e7056c4 AD |
147 | /* __jhash_nwords - hash exactly 3, 2 or 1 word(s) */ |
148 | static inline u32 __jhash_nwords(u32 a, u32 b, u32 c, u32 initval) | |
1da177e4 | 149 | { |
2e7056c4 AD |
150 | a += initval; |
151 | b += initval; | |
1da177e4 LT |
152 | c += initval; |
153 | ||
60d509c8 | 154 | __jhash_final(a, b, c); |
1da177e4 LT |
155 | |
156 | return c; | |
157 | } | |
158 | ||
2e7056c4 AD |
159 | static inline u32 jhash_3words(u32 a, u32 b, u32 c, u32 initval) |
160 | { | |
161 | return __jhash_nwords(a, b, c, initval + JHASH_INITVAL + (3 << 2)); | |
162 | } | |
163 | ||
1da177e4 LT |
164 | static inline u32 jhash_2words(u32 a, u32 b, u32 initval) |
165 | { | |
2e7056c4 | 166 | return __jhash_nwords(a, b, 0, initval + JHASH_INITVAL + (2 << 2)); |
1da177e4 LT |
167 | } |
168 | ||
169 | static inline u32 jhash_1word(u32 a, u32 initval) | |
170 | { | |
2e7056c4 | 171 | return __jhash_nwords(a, 0, 0, initval + JHASH_INITVAL + (1 << 2)); |
1da177e4 LT |
172 | } |
173 | ||
174 | #endif /* _LINUX_JHASH_H */ |