target/linux/generic-2.6/patches-2.6.28/201-jhash3.patch

   1 --- a/include/linux/jhash.h
   2 +++ b/include/linux/jhash.h
   3 @@ -3,80 +3,95 @@
   4
   5  /* jhash.h: Jenkins hash support.
   6   *
   7 - * Copyright (C) 1996 Bob Jenkins (bob_jenkins@burtleburtle.net)
   8 + * Copyright (C) 2006. 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 + * lookup3.c, by Bob Jenkins, May 2006, Public Domain.
  19   *
  20 - * Copyright (C) 2003 David S. Miller (davem@redhat.com)
  21 + * These are functions for producing 32-bit hashes for hash table lookup.
  22 + * hashword(), hashlittle(), hashlittle2(), hashbig(), mix(), and final()
  23 + * are externally useful functions.  Routines to test the hash are included
  24 + * if SELF_TEST is defined.  You can use this free for any purpose.  It's in
  25 + * the public domain.  It has no warranty.
  26 + *
  27 + * Copyright (C) 2009 Jozsef Kadlecsik (kadlec@blackhole.kfki.hu)
  28   *
  29   * I've modified Bob's hash to be useful in the Linux kernel, and
  30 - * any bugs present are surely my fault.  -DaveM
  31 + * any bugs present are my fault.  Jozsef
  32   */
  33
  34 -/* NOTE: Arguments are modified. */
  35 -#define __jhash_mix(a, b, c) \
  36 +#define __rot(x,k) (((x)<<(k)) | ((x)>>(32-(k))))
  37 +
  38 +/* __jhash_mix - mix 3 32-bit values reversibly. */
  39 +#define __jhash_mix(a,b,c) \
  40 +{ \
  41 +  a -= c;  a ^= __rot(c, 4);  c += b; \
  42 +  b -= a;  b ^= __rot(a, 6);  a += c; \
  43 +  c -= b;  c ^= __rot(b, 8);  b += a; \
  44 +  a -= c;  a ^= __rot(c,16);  c += b; \
  45 +  b -= a;  b ^= __rot(a,19);  a += c; \
  46 +  c -= b;  c ^= __rot(b, 4);  b += a; \
  47 +}
  48 +
  49 +/* __jhash_final - final mixing of 3 32-bit values (a,b,c) into c */
  50 +#define __jhash_final(a,b,c) \
  51  { \
  52 -  a -= b; a -= c; a ^= (c>>13); \
  53 -  b -= c; b -= a; b ^= (a<<8); \
  54 -  c -= a; c -= b; c ^= (b>>13); \
  55 -  a -= b; a -= c; a ^= (c>>12);  \
  56 -  b -= c; b -= a; b ^= (a<<16); \
  57 -  c -= a; c -= b; c ^= (b>>5); \
  58 -  a -= b; a -= c; a ^= (c>>3);  \
  59 -  b -= c; b -= a; b ^= (a<<10); \
  60 -  c -= a; c -= b; c ^= (b>>15); \
  61 +  c ^= b; c -= __rot(b,14); \
  62 +  a ^= c; a -= __rot(c,11); \
  63 +  b ^= a; b -= __rot(a,25); \
  64 +  c ^= b; c -= __rot(b,16); \
  65 +  a ^= c; a -= __rot(c,4);  \
  66 +  b ^= a; b -= __rot(a,14); \
  67 +  c ^= b; c -= __rot(b,24); \
  68  }
  69
  70 -/* The golden ration: an arbitrary value */
  71 -#define JHASH_GOLDEN_RATIO     0x9e3779b9
  72 +/* An arbitrary initial parameter */
  73 +#define JHASH_GOLDEN_RATIO     0xdeadbeef
  74
  75  /* The most generic version, hashes an arbitrary sequence
  76   * of bytes.  No alignment or length assumptions are made about
  77 - * the input key.
  78 + * the input key. The result depends on endianness.
  79   */
  80  static inline u32 jhash(const void *key, u32 length, u32 initval)
  81  {
  82 -       u32 a, b, c, len;
  83 +       u32 a,b,c;
  84         const u8 *k = key;
  85
  86 -       len = length;
  87 -       a = b = JHASH_GOLDEN_RATIO;
  88 -       c = initval;
  89 -
  90 -       while (len >= 12) {
  91 -               a += (k[0] +((u32)k[1]<<8) +((u32)k[2]<<16) +((u32)k[3]<<24));
  92 -               b += (k[4] +((u32)k[5]<<8) +((u32)k[6]<<16) +((u32)k[7]<<24));
  93 -               c += (k[8] +((u32)k[9]<<8) +((u32)k[10]<<16)+((u32)k[11]<<24));
  94 -
  95 -               __jhash_mix(a,b,c);
  96 +       /* Set up the internal state */
  97 +       a = b = c = JHASH_GOLDEN_RATIO + length + initval;
  98
  99 +       /* all but the last block: affect some 32 bits of (a,b,c) */
 100 +       while (length > 12) {
 101 +               a += (k[0] + ((u32)k[1]<<8) + ((u32)k[2]<<16) + ((u32)k[3]<<24));
 102 +               b += (k[4] + ((u32)k[5]<<8) + ((u32)k[6]<<16) + ((u32)k[7]<<24));
 103 +               c += (k[8] + ((u32)k[9]<<8) + ((u32)k[10]<<16) + ((u32)k[11]<<24));
 104 +               __jhash_mix(a, b, c);
 105 +               length -= 12;
 106                 k += 12;
 107 -               len -= 12;
 108         }
 109
 110 -       c += length;
 111 -       switch (len) {
 112 -       case 11: c += ((u32)k[10]<<24);
 113 -       case 10: c += ((u32)k[9]<<16);
 114 -       case 9 : c += ((u32)k[8]<<8);
 115 -       case 8 : b += ((u32)k[7]<<24);
 116 -       case 7 : b += ((u32)k[6]<<16);
 117 -       case 6 : b += ((u32)k[5]<<8);
 118 +       /* last block: affect all 32 bits of (c) */
 119 +       /* all the case statements fall through */
 120 +       switch (length) {
 121 +       case 12: c += (u32)k[11]<<24;
 122 +       case 11: c += (u32)k[10]<<16;
 123 +       case 10: c += (u32)k[9]<<8;
 124 +       case 9 : c += k[8];
 125 +       case 8 : b += (u32)k[7]<<24;
 126 +       case 7 : b += (u32)k[6]<<16;
 127 +       case 6 : b += (u32)k[5]<<8;
 128         case 5 : b += k[4];
 129 -       case 4 : a += ((u32)k[3]<<24);
 130 -       case 3 : a += ((u32)k[2]<<16);
 131 -       case 2 : a += ((u32)k[1]<<8);
 132 +       case 4 : a += (u32)k[3]<<24;
 133 +       case 3 : a += (u32)k[2]<<16;
 134 +       case 2 : a += (u32)k[1]<<8;
 135         case 1 : a += k[0];
 136 -       };
 137 -
 138 -       __jhash_mix(a,b,c);
 139 +               __jhash_final(a, b, c);
 140 +       case 0 :
 141 +               break;
 142 +       }
 143
 144         return c;
 145  }
 146 @@ -86,58 +101,57 @@ static inline u32 jhash(const void *key,
 147   */
 148  static inline u32 jhash2(const u32 *k, u32 length, u32 initval)
 149  {
 150 -       u32 a, b, c, len;
 151 +       u32 a, b, c;
 152
 153 -       a = b = JHASH_GOLDEN_RATIO;
 154 -       c = initval;
 155 -       len = length;
 156 +       /* Set up the internal state */
 157 +       a = b = c = JHASH_GOLDEN_RATIO + (length<<2) + initval;
 158
 159 -       while (len >= 3) {
 160 +       /* handle most of the key */
 161 +       while (length > 3) {
 162                 a += k[0];
 163                 b += k[1];
 164                 c += k[2];
 165                 __jhash_mix(a, b, c);
 166 -               k += 3; len -= 3;
 167 +               length -= 3;
 168 +               k += 3;
 169         }
 170
 171 -       c += length * 4;
 172 -
 173 -       switch (len) {
 174 -       case 2 : b += k[1];
 175 -       case 1 : a += k[0];
 176 -       };
 177 -
 178 -       __jhash_mix(a,b,c);
 179 +       /* handle the last 3 u32's */
 180 +       /* all the case statements fall through */
 181 +       switch (length) {
 182 +       case 3: c += k[2];
 183 +       case 2: b += k[1];
 184 +       case 1: a += k[0];
 185 +               __jhash_final(a, b, c);
 186 +       case 0:     /* case 0: nothing left to add */
 187 +               break;
 188 +       }
 189
 190         return c;
 191  }
 192
 193 -
 194  /* A special ultra-optimized versions that knows they are hashing exactly
 195   * 3, 2 or 1 word(s).
 196 - *
 197 - * NOTE: In partilar the "c += length; __jhash_mix(a,b,c);" normally
 198 - *       done at the end is not done here.
 199   */
 200  static inline u32 jhash_3words(u32 a, u32 b, u32 c, u32 initval)
 201  {
 202 -       a += JHASH_GOLDEN_RATIO;
 203 -       b += JHASH_GOLDEN_RATIO;
 204 -       c += initval;
 205 +       a += JHASH_GOLDEN_RATIO + initval;
 206 +       b += JHASH_GOLDEN_RATIO + initval;
 207 +       c += JHASH_GOLDEN_RATIO + initval;
 208
 209 -       __jhash_mix(a, b, c);
 210 +       __jhash_final(a, b, c);
 211
 212         return c;
 213  }
 214
 215  static inline u32 jhash_2words(u32 a, u32 b, u32 initval)
 216  {
 217 -       return jhash_3words(a, b, 0, initval);
 218 +       return jhash_3words(0, a, b, initval);
 219  }
 220
 221  static inline u32 jhash_1word(u32 a, u32 initval)
 222  {
 223 -       return jhash_3words(a, 0, 0, initval);
 224 +       return jhash_3words(0, 0, a, initval);
 225  }
 226
 227  #endif /* _LINUX_JHASH_H */