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