projects / userspace-rcu.git / blame
| Commit | Line | Data |
|---|---|---|
| 674f7a69 MD |
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 | ||
| 5e28c532 | 25 | typedef uint8_t u8; |
| 674f7a69 MD |
26 | typedef uint32_t u32; |
| 27 | ||
| 28 | /* NOTE: Arguments are modified. */ | |
| 29 | #define __jhash_mix(a, b, c) \ | |
| 30 | { \ | |
| 31 | a -= b; a -= c; a ^= (c>>13); \ | |
| 32 | b -= c; b -= a; b ^= (a<<8); \ | |
| 33 | c -= a; c -= b; c ^= (b>>13); \ | |
| 34 | a -= b; a -= c; a ^= (c>>12); \ | |
| 35 | b -= c; b -= a; b ^= (a<<16); \ | |
| 36 | c -= a; c -= b; c ^= (b>>5); \ | |
| 37 | a -= b; a -= c; a ^= (c>>3); \ | |
| 38 | b -= c; b -= a; b ^= (a<<10); \ | |
| 39 | c -= a; c -= b; c ^= (b>>15); \ | |
| 40 | } | |
| 41 | ||
| 42 | /* The golden ration: an arbitrary value */ | |
| 43 | #define JHASH_GOLDEN_RATIO 0x9e3779b9 | |
| 44 | ||
| 45 | /* The most generic version, hashes an arbitrary sequence | |
| 46 | * of bytes. No alignment or length assumptions are made about | |
| 47 | * the input key. | |
| 48 | */ | |
| 49 | static inline u32 jhash(const void *key, u32 length, u32 initval) | |
| 50 | { | |
| 51 | u32 a, b, c, len; | |
| 52 | const u8 *k = key; | |
| 53 | ||
| 54 | len = length; | |
| 55 | a = b = JHASH_GOLDEN_RATIO; | |
| 56 | c = initval; | |
| 57 | ||
| 58 | while (len >= 12) { | |
| 59 | a += (k[0] +((u32)k[1]<<8) +((u32)k[2]<<16) +((u32)k[3]<<24)); | |
| 60 | b += (k[4] +((u32)k[5]<<8) +((u32)k[6]<<16) +((u32)k[7]<<24)); | |
| 61 | c += (k[8] +((u32)k[9]<<8) +((u32)k[10]<<16)+((u32)k[11]<<24)); | |
| 62 | ||
| 63 | __jhash_mix(a,b,c); | |
| 64 | ||
| 65 | k += 12; | |
| 66 | len -= 12; | |
| 67 | } | |
| 68 | ||
| 69 | c += length; | |
| 70 | switch (len) { | |
| 71 | case 11: c += ((u32)k[10]<<24); | |
| 72 | case 10: c += ((u32)k[9]<<16); | |
| 73 | case 9 : c += ((u32)k[8]<<8); | |
| 74 | case 8 : b += ((u32)k[7]<<24); | |
| 75 | case 7 : b += ((u32)k[6]<<16); | |
| 76 | case 6 : b += ((u32)k[5]<<8); | |
| 77 | case 5 : b += k[4]; | |
| 78 | case 4 : a += ((u32)k[3]<<24); | |
| 79 | case 3 : a += ((u32)k[2]<<16); | |
| 80 | case 2 : a += ((u32)k[1]<<8); | |
| 81 | case 1 : a += k[0]; | |
| 82 | }; | |
| 83 | ||
| 84 | __jhash_mix(a,b,c); | |
| 85 | ||
| 86 | return c; | |
| 87 | } | |
| 88 | ||
| 89 | #endif /* _KCOMPAT_JHASH_H */ |