sys/dev/pci/cxgb_jhash.h

   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: src/sys/dev/cxgb/common/jhash.h,v 1.1 2007/05/25 09:48:19 kmacy Exp $
  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 */