1 #ifndef _JHASH_H 2 #define _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 * $FreeBSD$ 18 */ 19 20 /* NOTE: Arguments are modified. */ 21 #define __jhash_mix(a, b, c) \ 22 { \ 23 a -= b; a -= c; a ^= (c>>13); \ 24 b -= c; b -= a; b ^= (a<<8); \ 25 c -= a; c -= b; c ^= (b>>13); \ 26 a -= b; a -= c; a ^= (c>>12); \ 27 b -= c; b -= a; b ^= (a<<16); \ 28 c -= a; c -= b; c ^= (b>>5); \ 29 a -= b; a -= c; a ^= (c>>3); \ 30 b -= c; b -= a; b ^= (a<<10); \ 31 c -= a; c -= b; c ^= (b>>15); \ 32 } 33 34 /* The golden ration: an arbitrary value */ 35 #define JHASH_GOLDEN_RATIO 0x9e3779b9 36 37 /* The most generic version, hashes an arbitrary sequence 38 * of bytes. No alignment or length assumptions are made about 39 * the input key. 40 */ 41 static inline u32 jhash(const void *key, u32 length, u32 initval) 42 { 43 u32 a, b, c, len; 44 const u8 *k = key; 45 46 len = length; 47 a = b = JHASH_GOLDEN_RATIO; 48 c = initval; 49 50 while (len >= 12) { 51 a += (k[0] +((u32)k[1]<<8) +((u32)k[2]<<16) +((u32)k[3]<<24)); 52 b += (k[4] +((u32)k[5]<<8) +((u32)k[6]<<16) +((u32)k[7]<<24)); 53 c += (k[8] +((u32)k[9]<<8) +((u32)k[10]<<16)+((u32)k[11]<<24)); 54 55 __jhash_mix(a,b,c); 56 57 k += 12; 58 len -= 12; 59 } 60 61 c += length; 62 switch (len) { 63 case 11: c += ((u32)k[10]<<24); 64 case 10: c += ((u32)k[9]<<16); 65 case 9 : c += ((u32)k[8]<<8); 66 case 8 : b += ((u32)k[7]<<24); 67 case 7 : b += ((u32)k[6]<<16); 68 case 6 : b += ((u32)k[5]<<8); 69 case 5 : b += k[4]; 70 case 4 : a += ((u32)k[3]<<24); 71 case 3 : a += ((u32)k[2]<<16); 72 case 2 : a += ((u32)k[1]<<8); 73 case 1 : a += k[0]; 74 }; 75 76 __jhash_mix(a,b,c); 77 78 return c; 79 } 80 81 /* A special optimized version that handles 1 or more of u32s. 82 * The length parameter here is the number of u32s in the key. 83 */ 84 static inline u32 jhash2(u32 *k, u32 length, u32 initval) 85 { 86 u32 a, b, c, len; 87 88 a = b = JHASH_GOLDEN_RATIO; 89 c = initval; 90 len = length; 91 92 while (len >= 3) { 93 a += k[0]; 94 b += k[1]; 95 c += k[2]; 96 __jhash_mix(a, b, c); 97 k += 3; len -= 3; 98 } 99 100 c += length * 4; 101 102 switch (len) { 103 case 2 : b += k[1]; 104 case 1 : a += k[0]; 105 }; 106 107 __jhash_mix(a,b,c); 108 109 return c; 110 } 111 112 113 /* A special ultra-optimized versions that knows they are hashing exactly 114 * 3, 2 or 1 word(s). 115 * 116 * NOTE: In partilar the "c += length; __jhash_mix(a,b,c);" normally 117 * done at the end is not done here. 118 */ 119 static inline u32 jhash_3words(u32 a, u32 b, u32 c, u32 initval) 120 { 121 a += JHASH_GOLDEN_RATIO; 122 b += JHASH_GOLDEN_RATIO; 123 c += initval; 124 125 __jhash_mix(a, b, c); 126 127 return c; 128 } 129 130 static inline u32 jhash_2words(u32 a, u32 b, u32 initval) 131 { 132 return jhash_3words(a, b, 0, initval); 133 } 134 135 static inline u32 jhash_1word(u32 a, u32 initval) 136 { 137 return jhash_3words(a, 0, 0, initval); 138 } 139 140 #endif /* _JHASH_H */ 141