jhash.h

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    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 */

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FreeBSD/Linux Kernel Cross Reference sys/dev/cxgb/common/jhash.h

FreeBSD/Linux Kernel Cross Reference
sys/dev/cxgb/common/jhash.h