jhash.h

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    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  * $FreeBSD$
   25  */
   26 
   27 /* NOTE: Arguments are modified. */
   28 #define __jhash_mix(a, b, c) \
   29 { \
   30   a -= b; a -= c; a ^= (c>>13); \
   31   b -= c; b -= a; b ^= (a<<8); \
   32   c -= a; c -= b; c ^= (b>>13); \
   33   a -= b; a -= c; a ^= (c>>12);  \
   34   b -= c; b -= a; b ^= (a<<16); \
   35   c -= a; c -= b; c ^= (b>>5); \
   36   a -= b; a -= c; a ^= (c>>3);  \
   37   b -= c; b -= a; b ^= (a<<10); \
   38   c -= a; c -= b; c ^= (b>>15); \
   39 }
   40 
   41 /* The golden ration: an arbitrary value */
   42 #define JHASH_GOLDEN_RATIO      0x9e3779b9
   43 
   44 /* The most generic version, hashes an arbitrary sequence
   45  * of bytes.  No alignment or length assumptions are made about
   46  * the input key.
   47  */
   48 static inline u32 jhash(const void *key, u32 length, u32 initval)
   49 {
   50         u32 a, b, c, len;
   51         const u8 *k = key;
   52 
   53         len = length;
   54         a = b = JHASH_GOLDEN_RATIO;
   55         c = initval;
   56 
   57         while (len >= 12) {
   58                 a += (k[0] +((u32)k[1]<<8) +((u32)k[2]<<16) +((u32)k[3]<<24));
   59                 b += (k[4] +((u32)k[5]<<8) +((u32)k[6]<<16) +((u32)k[7]<<24));
   60                 c += (k[8] +((u32)k[9]<<8) +((u32)k[10]<<16)+((u32)k[11]<<24));
   61 
   62                 __jhash_mix(a,b,c);
   63 
   64                 k += 12;
   65                 len -= 12;
   66         }
   67 
   68         c += length;
   69         switch (len) {
   70         case 11: c += ((u32)k[10]<<24);
   71         case 10: c += ((u32)k[9]<<16);
   72         case 9 : c += ((u32)k[8]<<8);
   73         case 8 : b += ((u32)k[7]<<24);
   74         case 7 : b += ((u32)k[6]<<16);
   75         case 6 : b += ((u32)k[5]<<8);
   76         case 5 : b += k[4];
   77         case 4 : a += ((u32)k[3]<<24);
   78         case 3 : a += ((u32)k[2]<<16);
   79         case 2 : a += ((u32)k[1]<<8);
   80         case 1 : a += k[0];
   81         };
   82 
   83         __jhash_mix(a,b,c);
   84 
   85         return c;
   86 }
   87 
   88 /* A special optimized version that handles 1 or more of u32s.
   89  * The length parameter here is the number of u32s in the key.
   90  */
   91 static inline u32 jhash2(const u32 *k, u32 length, u32 initval)
   92 {
   93         u32 a, b, c, len;
   94 
   95         a = b = JHASH_GOLDEN_RATIO;
   96         c = initval;
   97         len = length;
   98 
   99         while (len >= 3) {
  100                 a += k[0];
  101                 b += k[1];
  102                 c += k[2];
  103                 __jhash_mix(a, b, c);
  104                 k += 3; len -= 3;
  105         }
  106 
  107         c += length * 4;
  108 
  109         switch (len) {
  110         case 2 : b += k[1];
  111         case 1 : a += k[0];
  112         };
  113 
  114         __jhash_mix(a,b,c);
  115 
  116         return c;
  117 }
  118 
  119 /* A special ultra-optimized versions that knows they are hashing exactly
  120  * 3, 2 or 1 word(s).
  121  *
  122  * NOTE: In partilar the "c += length; __jhash_mix(a,b,c);" normally
  123  *       done at the end is not done here.
  124  */
  125 static inline u32 jhash_3words(u32 a, u32 b, u32 c, u32 initval)
  126 {
  127         a += JHASH_GOLDEN_RATIO;
  128         b += JHASH_GOLDEN_RATIO;
  129         c += initval;
  130 
  131         __jhash_mix(a, b, c);
  132 
  133         return c;
  134 }
  135 
  136 static inline u32 jhash_2words(u32 a, u32 b, u32 initval)
  137 {
  138         return jhash_3words(a, b, 0, initval);
  139 }
  140 
  141 static inline u32 jhash_1word(u32 a, u32 initval)
  142 {
  143         return jhash_3words(a, 0, 0, initval);
  144 }
  145 
  146 #endif  /* _LINUXKPI_LINUX_JHASH_H_ */

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FreeBSD/Linux Kernel Cross Reference sys/compat/linuxkpi/common/include/linux/jhash.h

FreeBSD/Linux Kernel Cross Reference
sys/compat/linuxkpi/common/include/linux/jhash.h