1 #ifndef _LINUXKPI_LINUX_JHASH_H_ 2 #define _LINUXKPI_LINUX_JHASH_H_ 3 4 #include <asm/types.h> 5 6 /* jhash.h: Jenkins hash support. 7 * 8 * Copyright (C) 1996 Bob Jenkins (bob_jenkins@burtleburtle.net) 9 * 10 * http://burtleburtle.net/bob/hash/ 11 * 12 * These are the credits from Bob's sources: 13 * 14 * lookup2.c, by Bob Jenkins, December 1996, Public Domain. 15 * hash(), hash2(), hash3, and mix() are externally useful functions. 16 * Routines to test the hash are included if SELF_TEST is defined. 17 * You can use this free for any purpose. It has no warranty. 18 * 19 * Copyright (C) 2003 David S. Miller (davem@redhat.com) 20 * 21 * I've modified Bob's hash to be useful in the Linux kernel, and 22 * any bugs present are surely my fault. -DaveM 23 */ 24 25 /* NOTE: Arguments are modified. */ 26 #define __jhash_mix(a, b, c) \ 27 { \ 28 a -= b; a -= c; a ^= (c>>13); \ 29 b -= c; b -= a; b ^= (a<<8); \ 30 c -= a; c -= b; c ^= (b>>13); \ 31 a -= b; a -= c; a ^= (c>>12); \ 32 b -= c; b -= a; b ^= (a<<16); \ 33 c -= a; c -= b; c ^= (b>>5); \ 34 a -= b; a -= c; a ^= (c>>3); \ 35 b -= c; b -= a; b ^= (a<<10); \ 36 c -= a; c -= b; c ^= (b>>15); \ 37 } 38 39 /* The golden ration: an arbitrary value */ 40 #define JHASH_GOLDEN_RATIO 0x9e3779b9 41 42 /* The most generic version, hashes an arbitrary sequence 43 * of bytes. No alignment or length assumptions are made about 44 * the input key. 45 */ 46 static inline u32 jhash(const void *key, u32 length, u32 initval) 47 { 48 u32 a, b, c, len; 49 const u8 *k = key; 50 51 len = length; 52 a = b = JHASH_GOLDEN_RATIO; 53 c = initval; 54 55 while (len >= 12) { 56 a += (k[0] +((u32)k[1]<<8) +((u32)k[2]<<16) +((u32)k[3]<<24)); 57 b += (k[4] +((u32)k[5]<<8) +((u32)k[6]<<16) +((u32)k[7]<<24)); 58 c += (k[8] +((u32)k[9]<<8) +((u32)k[10]<<16)+((u32)k[11]<<24)); 59 60 __jhash_mix(a,b,c); 61 62 k += 12; 63 len -= 12; 64 } 65 66 c += length; 67 switch (len) { 68 case 11: c += ((u32)k[10]<<24); 69 case 10: c += ((u32)k[9]<<16); 70 case 9 : c += ((u32)k[8]<<8); 71 case 8 : b += ((u32)k[7]<<24); 72 case 7 : b += ((u32)k[6]<<16); 73 case 6 : b += ((u32)k[5]<<8); 74 case 5 : b += k[4]; 75 case 4 : a += ((u32)k[3]<<24); 76 case 3 : a += ((u32)k[2]<<16); 77 case 2 : a += ((u32)k[1]<<8); 78 case 1 : a += k[0]; 79 }; 80 81 __jhash_mix(a,b,c); 82 83 return c; 84 } 85 86 /* A special optimized version that handles 1 or more of u32s. 87 * The length parameter here is the number of u32s in the key. 88 */ 89 static inline u32 jhash2(const u32 *k, u32 length, u32 initval) 90 { 91 u32 a, b, c, len; 92 93 a = b = JHASH_GOLDEN_RATIO; 94 c = initval; 95 len = length; 96 97 while (len >= 3) { 98 a += k[0]; 99 b += k[1]; 100 c += k[2]; 101 __jhash_mix(a, b, c); 102 k += 3; len -= 3; 103 } 104 105 c += length * 4; 106 107 switch (len) { 108 case 2 : b += k[1]; 109 case 1 : a += k[0]; 110 }; 111 112 __jhash_mix(a,b,c); 113 114 return c; 115 } 116 117 /* A special ultra-optimized versions that knows they are hashing exactly 118 * 3, 2 or 1 word(s). 119 * 120 * NOTE: In partilar the "c += length; __jhash_mix(a,b,c);" normally 121 * done at the end is not done here. 122 */ 123 static inline u32 jhash_3words(u32 a, u32 b, u32 c, u32 initval) 124 { 125 a += JHASH_GOLDEN_RATIO; 126 b += JHASH_GOLDEN_RATIO; 127 c += initval; 128 129 __jhash_mix(a, b, c); 130 131 return c; 132 } 133 134 static inline u32 jhash_2words(u32 a, u32 b, u32 initval) 135 { 136 return jhash_3words(a, b, 0, initval); 137 } 138 139 static inline u32 jhash_1word(u32 a, u32 initval) 140 { 141 return jhash_3words(a, 0, 0, initval); 142 } 143 144 #endif /* _LINUXKPI_LINUX_JHASH_H_ */ 145