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1 | #ifndef _KCOMPAT_JHASH_H |
2 | #define _KCOMPAT_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 | * Copyright (C) 2003 David S. Miller (davem@redhat.com) | |
18 | * | |
19 | * I've modified Bob's hash to be useful in the Linux kernel, and | |
20 | * any bugs present are surely my fault. -DaveM | |
21 | */ | |
22 | ||
23 | #include <stdint.h> | |
24 | ||
25 | typedef uint32_t u32; | |
26 | ||
27 | /* NOTE: Arguments are modified. */ | |
28 | #define __jhash_mix(a, b, c) \ | |
29 | { \ | |
30 | a -= b; a -= c; a ^= (c>>13); \ | |
31 | b -= c; b -= a; b ^= (a<<8); \ | |
32 | c -= a; c -= b; c ^= (b>>13); \ | |
33 | a -= b; a -= c; a ^= (c>>12); \ | |
34 | b -= c; b -= a; b ^= (a<<16); \ | |
35 | c -= a; c -= b; c ^= (b>>5); \ | |
36 | a -= b; a -= c; a ^= (c>>3); \ | |
37 | b -= c; b -= a; b ^= (a<<10); \ | |
38 | c -= a; c -= b; c ^= (b>>15); \ | |
39 | } | |
40 | ||
41 | /* The golden ration: an arbitrary value */ | |
42 | #define JHASH_GOLDEN_RATIO 0x9e3779b9 | |
43 | ||
44 | /* The most generic version, hashes an arbitrary sequence | |
45 | * of bytes. No alignment or length assumptions are made about | |
46 | * the input key. | |
47 | */ | |
48 | static inline u32 jhash(const void *key, u32 length, u32 initval) | |
49 | { | |
50 | u32 a, b, c, len; | |
51 | const u8 *k = key; | |
52 | ||
53 | len = length; | |
54 | a = b = JHASH_GOLDEN_RATIO; | |
55 | c = initval; | |
56 | ||
57 | while (len >= 12) { | |
58 | a += (k[0] +((u32)k[1]<<8) +((u32)k[2]<<16) +((u32)k[3]<<24)); | |
59 | b += (k[4] +((u32)k[5]<<8) +((u32)k[6]<<16) +((u32)k[7]<<24)); | |
60 | c += (k[8] +((u32)k[9]<<8) +((u32)k[10]<<16)+((u32)k[11]<<24)); | |
61 | ||
62 | __jhash_mix(a,b,c); | |
63 | ||
64 | k += 12; | |
65 | len -= 12; | |
66 | } | |
67 | ||
68 | c += length; | |
69 | switch (len) { | |
70 | case 11: c += ((u32)k[10]<<24); | |
71 | case 10: c += ((u32)k[9]<<16); | |
72 | case 9 : c += ((u32)k[8]<<8); | |
73 | case 8 : b += ((u32)k[7]<<24); | |
74 | case 7 : b += ((u32)k[6]<<16); | |
75 | case 6 : b += ((u32)k[5]<<8); | |
76 | case 5 : b += k[4]; | |
77 | case 4 : a += ((u32)k[3]<<24); | |
78 | case 3 : a += ((u32)k[2]<<16); | |
79 | case 2 : a += ((u32)k[1]<<8); | |
80 | case 1 : a += k[0]; | |
81 | }; | |
82 | ||
83 | __jhash_mix(a,b,c); | |
84 | ||
85 | return c; | |
86 | } | |
87 | ||
88 | #endif /* _KCOMPAT_JHASH_H */ |