| 1 | #ifndef _LINUX_JHASH_H
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| 2 | #define _LINUX_JHASH_H
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| 3 |
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| 4 | |
| 5 | *
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| 6 | * Copyright (C) 1996 Bob Jenkins ([email protected])
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| 7 | *
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| 8 | * http://burtleburtle.net/bob/hash/
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| 9 | *
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| 10 | * These are the credits from Bob's sources:
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| 11 | *
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| 12 | * lookup2.c, by Bob Jenkins, December 1996, Public Domain.
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| 13 | * hash(), hash2(), hash3, and mix() are externally useful functions.
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| 14 | * Routines to test the hash are included if SELF_TEST is defined.
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| 15 | * You can use this free for any purpose. It has no warranty.
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| 16 | *
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| 17 | * Copyright (C) 2003 David S. Miller ([email protected])
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| 18 | *
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| 19 | * I've modified Bob's hash to be useful in the Linux kernel, and
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| 20 | * any bugs present are surely my fault. -DaveM
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| 21 |
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| 22 |
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| 23 |
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| 24 | #define __jhash_mix(a, b, c) \
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| 25 | { \
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| 26 | a -= b; a -= c; a ^= (c>>13); \
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| 27 | b -= c; b -= a; b ^= (a<<8); \
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| 28 | c -= a; c -= b; c ^= (b>>13); \
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| 29 | a -= b; a -= c; a ^= (c>>12); \
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| 30 | b -= c; b -= a; b ^= (a<<16); \
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| 31 | c -= a; c -= b; c ^= (b>>5); \
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| 32 | a -= b; a -= c; a ^= (c>>3); \
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| 33 | b -= c; b -= a; b ^= (a<<10); \
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| 34 | c -= a; c -= b; c ^= (b>>15); \
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| 35 | }
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| 36 |
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| 37 |
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| 38 | #define JHASH_GOLDEN_RATIO 0x9e3779b9
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| 39 |
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| 40 | |
| 41 | * of bytes. No alignment or length assumptions are made about
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| 42 | * the input key.
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| 43 |
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| 44 | static inline u32 jhash(const void *key, u32 length, u32 initval)
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| 45 | {
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| 46 | u32 a, b, c, len;
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| 47 | const u8 *k = key;
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| 48 |
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| 49 | len = length;
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| 50 | a = b = JHASH_GOLDEN_RATIO;
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| 51 | c = initval;
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| 52 |
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| 53 | while (len >= 12) {
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| 54 | a += (k[0] +((u32)k[1]<<8) +((u32)k[2]<<16) +((u32)k[3]<<24));
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| 55 | b += (k[4] +((u32)k[5]<<8) +((u32)k[6]<<16) +((u32)k[7]<<24));
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| 56 | c += (k[8] +((u32)k[9]<<8) +((u32)k[10]<<16)+((u32)k[11]<<24));
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| 57 |
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| 58 | __jhash_mix(a,b,c);
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| 59 |
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| 60 | k += 12;
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| 61 | len -= 12;
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| 62 | }
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| 63 |
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| 64 | c += length;
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| 65 | switch (len) {
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| 66 | case 11: c += ((u32)k[10]<<24);
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| 67 | case 10: c += ((u32)k[9]<<16);
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| 68 | case 9 : c += ((u32)k[8]<<8);
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| 69 | case 8 : b += ((u32)k[7]<<24);
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| 70 | case 7 : b += ((u32)k[6]<<16);
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| 71 | case 6 : b += ((u32)k[5]<<8);
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| 72 | case 5 : b += k[4];
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| 73 | case 4 : a += ((u32)k[3]<<24);
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| 74 | case 3 : a += ((u32)k[2]<<16);
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| 75 | case 2 : a += ((u32)k[1]<<8);
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| 76 | case 1 : a += k[0];
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| 77 | };
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| 78 |
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| 79 | __jhash_mix(a,b,c);
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| 80 |
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| 81 | return c;
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| 82 | }
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| 83 |
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| 84 | |
| 85 | * The length parameter here is the number of u32s in the key.
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| 86 |
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| 87 | static inline u32 jhash2(u32 *k, u32 length, u32 initval)
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| 88 | {
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| 89 | u32 a, b, c, len;
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| 90 |
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| 91 | a = b = JHASH_GOLDEN_RATIO;
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| 92 | c = initval;
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| 93 | len = length;
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| 94 |
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| 95 | while (len >= 3) {
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| 96 | a += k[0];
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| 97 | b += k[1];
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| 98 | c += k[2];
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| 99 | __jhash_mix(a, b, c);
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| 100 | k += 3; len -= 3;
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| 101 | }
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| 102 |
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| 103 | c += length * 4;
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| 104 |
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| 105 | switch (len) {
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| 106 | case 2 : b += k[1];
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| 107 | case 1 : a += k[0];
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| 108 | };
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| 109 |
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| 110 | __jhash_mix(a,b,c);
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| 111 |
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| 112 | return c;
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| 113 | }
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| 114 |
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| 115 |
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| 116 | |
| 117 | * 3, 2 or 1 word(s).
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| 118 | *
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| 119 | * NOTE: In partilar the "c += length; __jhash_mix(a,b,c);" normally
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| 120 | * done at the end is not done here.
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| 121 |
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| 122 | static inline u32 jhash_3words(u32 a, u32 b, u32 c, u32 initval)
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| 123 | {
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| 124 | a += JHASH_GOLDEN_RATIO;
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| 125 | b += JHASH_GOLDEN_RATIO;
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| 126 | c += initval;
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| 127 |
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| 128 | __jhash_mix(a, b, c);
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| 129 |
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| 130 | return c;
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| 131 | }
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| 132 |
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| 133 | static inline u32 jhash_2words(u32 a, u32 b, u32 initval)
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| 134 | {
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| 135 | return jhash_3words(a, b, 0, initval);
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| 136 | }
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| 137 |
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| 138 | static inline u32 jhash_1word(u32 a, u32 initval)
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| 139 | {
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| 140 | return jhash_3words(a, 0, 0, initval);
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| 141 | }
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| 142 |
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| 143 | #endif
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