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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 | * | |
79e3ea5a | 8 | * https://burtleburtle.net/bob/hash/ |
6c8e6483 LASL |
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_nwords - hash exactly 3, 2 or 1 word(s) */ | |
149 | static inline u32 __jhash_nwords(u32 a, u32 b, u32 c, u32 initval) | |
150 | { | |
151 | a += initval; | |
152 | b += initval; | |
153 | c += initval; | |
154 | ||
155 | __jhash_final(a, b, c); | |
156 | ||
157 | return c; | |
158 | } | |
159 | ||
160 | static inline u32 jhash_3words(u32 a, u32 b, u32 c, u32 initval) | |
161 | { | |
162 | return __jhash_nwords(a, b, c, initval + JHASH_INITVAL + (3 << 2)); | |
163 | } | |
164 | ||
165 | static inline u32 jhash_2words(u32 a, u32 b, u32 initval) | |
166 | { | |
167 | return __jhash_nwords(a, b, 0, initval + JHASH_INITVAL + (2 << 2)); | |
168 | } | |
169 | ||
170 | static inline u32 jhash_1word(u32 a, u32 initval) | |
171 | { | |
172 | return __jhash_nwords(a, 0, 0, initval + JHASH_INITVAL + (1 << 2)); | |
173 | } | |
174 | ||
175 | #endif /* _LINUX_JHASH_H */ |