Details | Last modification | View Log | RSS feed
| Rev | Author | Line No. | Line |
|---|---|---|---|
| 422 | giacomo | 1 | #ifndef _LINUX_JHASH_H |
| 2 | #define _LINUX_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 | /* NOTE: Arguments are modified. */ |
||
| 24 | #define __jhash_mix(a, b, c) \ |
||
| 25 | { \ |
||
| 26 | a -= b; a -= c; a ^= (c>>13); \ |
||
| 27 | b -= c; b -= a; b ^= (a<<8); \ |
||
| 28 | c -= a; c -= b; c ^= (b>>13); \ |
||
| 29 | a -= b; a -= c; a ^= (c>>12); \ |
||
| 30 | b -= c; b -= a; b ^= (a<<16); \ |
||
| 31 | c -= a; c -= b; c ^= (b>>5); \ |
||
| 32 | a -= b; a -= c; a ^= (c>>3); \ |
||
| 33 | b -= c; b -= a; b ^= (a<<10); \ |
||
| 34 | c -= a; c -= b; c ^= (b>>15); \ |
||
| 35 | } |
||
| 36 | |||
| 37 | /* The golden ration: an arbitrary value */ |
||
| 38 | #define JHASH_GOLDEN_RATIO 0x9e3779b9 |
||
| 39 | |||
| 40 | /* The most generic version, hashes an arbitrary sequence |
||
| 41 | * of bytes. No alignment or length assumptions are made about |
||
| 42 | * the input key. |
||
| 43 | */ |
||
| 44 | static inline u32 jhash(void *key, u32 length, u32 initval) |
||
| 45 | { |
||
| 46 | u32 a, b, c, len; |
||
| 47 | u8 *k = key; |
||
| 48 | |||
| 49 | len = length; |
||
| 50 | a = b = JHASH_GOLDEN_RATIO; |
||
| 51 | c = initval; |
||
| 52 | |||
| 53 | while (len >= 12) { |
||
| 54 | a += (k[0] +((u32)k[1]<<8) +((u32)k[2]<<16) +((u32)k[3]<<24)); |
||
| 55 | b += (k[4] +((u32)k[5]<<8) +((u32)k[6]<<16) +((u32)k[7]<<24)); |
||
| 56 | c += (k[8] +((u32)k[9]<<8) +((u32)k[10]<<16)+((u32)k[11]<<24)); |
||
| 57 | |||
| 58 | __jhash_mix(a,b,c); |
||
| 59 | |||
| 60 | k += 12; |
||
| 61 | len -= 12; |
||
| 62 | } |
||
| 63 | |||
| 64 | c += length; |
||
| 65 | switch (len) { |
||
| 66 | case 11: c += ((u32)k[10]<<24); |
||
| 67 | case 10: c += ((u32)k[9]<<16); |
||
| 68 | case 9 : c += ((u32)k[8]<<8); |
||
| 69 | case 8 : b += ((u32)k[7]<<24); |
||
| 70 | case 7 : b += ((u32)k[6]<<16); |
||
| 71 | case 6 : b += ((u32)k[5]<<8); |
||
| 72 | case 5 : b += k[4]; |
||
| 73 | case 4 : a += ((u32)k[3]<<24); |
||
| 74 | case 3 : a += ((u32)k[2]<<16); |
||
| 75 | case 2 : a += ((u32)k[1]<<8); |
||
| 76 | case 1 : a += k[0]; |
||
| 77 | }; |
||
| 78 | |||
| 79 | __jhash_mix(a,b,c); |
||
| 80 | |||
| 81 | return c; |
||
| 82 | } |
||
| 83 | |||
| 84 | /* A special optimized version that handles 1 or more of u32s. |
||
| 85 | * The length parameter here is the number of u32s in the key. |
||
| 86 | */ |
||
| 87 | static inline u32 jhash2(u32 *k, u32 length, u32 initval) |
||
| 88 | { |
||
| 89 | u32 a, b, c, len; |
||
| 90 | |||
| 91 | a = b = JHASH_GOLDEN_RATIO; |
||
| 92 | c = initval; |
||
| 93 | len = length; |
||
| 94 | |||
| 95 | while (len >= 3) { |
||
| 96 | a += k[0]; |
||
| 97 | b += k[1]; |
||
| 98 | c += k[2]; |
||
| 99 | __jhash_mix(a, b, c); |
||
| 100 | k += 3; len -= 3; |
||
| 101 | } |
||
| 102 | |||
| 103 | c += length * 4; |
||
| 104 | |||
| 105 | switch (len) { |
||
| 106 | case 2 : b += k[1]; |
||
| 107 | case 1 : a += k[0]; |
||
| 108 | }; |
||
| 109 | |||
| 110 | __jhash_mix(a,b,c); |
||
| 111 | |||
| 112 | return c; |
||
| 113 | } |
||
| 114 | |||
| 115 | |||
| 116 | /* A special ultra-optimized versions that knows they are hashing exactly |
||
| 117 | * 3, 2 or 1 word(s). |
||
| 118 | * |
||
| 119 | * NOTE: In partilar the "c += length; __jhash_mix(a,b,c);" normally |
||
| 120 | * done at the end is not done here. |
||
| 121 | */ |
||
| 122 | static inline u32 jhash_3words(u32 a, u32 b, u32 c, u32 initval) |
||
| 123 | { |
||
| 124 | a += JHASH_GOLDEN_RATIO; |
||
| 125 | b += JHASH_GOLDEN_RATIO; |
||
| 126 | c += initval; |
||
| 127 | |||
| 128 | __jhash_mix(a, b, c); |
||
| 129 | |||
| 130 | return c; |
||
| 131 | } |
||
| 132 | |||
| 133 | static inline u32 jhash_2words(u32 a, u32 b, u32 initval) |
||
| 134 | { |
||
| 135 | return jhash_3words(a, b, 0, initval); |
||
| 136 | } |
||
| 137 | |||
| 138 | static inline u32 jhash_1word(u32 a, u32 initval) |
||
| 139 | { |
||
| 140 | return jhash_3words(a, 0, 0, initval); |
||
| 141 | } |
||
| 142 | |||
| 143 | #endif /* _LINUX_JHASH_H */ |