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   1 /*  vim:expandtab:shiftwidth=2:tabstop=2:smarttab:
   2  *
   3  *  HashKit library
   4  *
   5  *  Copyright (C) 2011-2012 Data Differential, http://datadifferential.com/
   6  *  Copyright (C) 2006-2009 Brian Aker All rights reserved.
   7  *
   8  *  Redistribution and use in source and binary forms, with or without
   9  *  modification, are permitted provided that the following conditions are
  10  *  met:
  11  *
  12  *      * Redistributions of source code must retain the above copyright
  13  *  notice, this list of conditions and the following disclaimer.
  14  *
  15  *      * Redistributions in binary form must reproduce the above
  16  *  copyright notice, this list of conditions and the following disclaimer
  17  *  in the documentation and/or other materials provided with the
  18  *  distribution.
  19  *
  20  *      * The names of its contributors may not be used to endorse or
  21  *  promote products derived from this software without specific prior
  22  *  written permission.
  23  *
  24  *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  25  *  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  26  *  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  27  *  A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  28  *  OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  29  *  SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  30  *  LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  31  *  DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  32  *  THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  33  *  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  34  *  OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  35  *
  36  */
  37
  38 /*
  39 *
  40 * By Bob Jenkins, 2006.  bob_jenkins@burtleburtle.net.  You may use this
  41 * code any way you wish, private, educational, or commercial.  It's free.
  42 * Use for hash table lookup, or anything where one collision in 2^^32 is
  43 * acceptable.  Do NOT use for cryptographic purposes.
  44 * http://burtleburtle.net/bob/hash/index.html
  45 *
  46 * Modified by Brian Pontz for libmemcached
  47 * TODO:
  48 * Add big endian support
  49 */
  50
  51 #include "libhashkit/common.h"
  52
  53 #define hashsize(n) ((uint32_t)1<<(n))
  54 #define hashmask(n) (hashsize(n)-1)
  55 #define rot(x,k) (((x)<<(k)) | ((x)>>(32-(k))))
  56
  57 #define mix(a,b,c) \
  58 { \
  59   a -= c;  a ^= rot(c, 4);  c += b; \
  60   b -= a;  b ^= rot(a, 6);  a += c; \
  61   c -= b;  c ^= rot(b, 8);  b += a; \
  62   a -= c;  a ^= rot(c,16);  c += b; \
  63   b -= a;  b ^= rot(a,19);  a += c; \
  64   c -= b;  c ^= rot(b, 4);  b += a; \
  65 }
  66
  67 #define final(a,b,c) \
  68 { \
  69   c ^= b; c -= rot(b,14); \
  70   a ^= c; a -= rot(c,11); \
  71   b ^= a; b -= rot(a,25); \
  72   c ^= b; c -= rot(b,16); \
  73   a ^= c; a -= rot(c,4);  \
  74   b ^= a; b -= rot(a,14); \
  75   c ^= b; c -= rot(b,24); \
  76 }
  77
  78 #define JENKINS_INITVAL 13
  79
  80 /*
  81 jenkins_hash() -- hash a variable-length key into a 32-bit value
  82   k       : the key (the unaligned variable-length array of bytes)
  83   length  : the length of the key, counting by bytes
  84   initval : can be any 4-byte value
  85 Returns a 32-bit value.  Every bit of the key affects every bit of
  86 the return value.  Two keys differing by one or two bits will have
  87 totally different hash values.
  88
  89 The best hash table sizes are powers of 2.  There is no need to do
  90 mod a prime (mod is sooo slow!).  If you need less than 32 bits,
  91 use a bitmask.  For example, if you need only 10 bits, do
  92   h = (h & hashmask(10));
  93 In which case, the hash table should have hashsize(10) elements.
  94 */
  95
  96 #if HAVE_ASAN
  97 __attribute__((no_sanitize_address,no_sanitize("address")))
  98 #endif
  99 uint32_t hashkit_jenkins(const char *key, size_t length, void *)
 100 {
 101   uint32_t a,b,c;                                          /* internal state */
 102 #if !WORDS_BIGENDIAN
 103   union { const void *ptr; size_t i; } u;
 104   u.ptr = key;
 105 #endif
 106
 107   /* Set up the internal state */
 108   a = b = c = 0xdeadbeef + ((uint32_t)length) + JENKINS_INITVAL;
 109
 110 #if !WORDS_BIGENDIAN
 111   if ((u.i & 0x3) == 0)
 112   {
 113     const uint32_t *k = (const uint32_t *)key;         /* read 32-bit chunks */
 114
 115     /*------ all but last block: aligned reads and affect 32 bits of (a,b,c) */
 116     while (length > 12)
 117     {
 118       a += k[0];
 119       b += k[1];
 120       c += k[2];
 121       mix(a,b,c);
 122       length -= 12;
 123       k += 3;
 124     }
 125
 126     /*----------------------------- handle the last (probably partial) block */
 127     /*
 128      * "k[2]&0xffffff" actually reads beyond the end of the string, but
 129      * then masks off the part it's not allowed to read.  Because the
 130      * string is aligned, the masked-off tail is in the same word as the
 131      * rest of the string.  Every machine with memory protection I've seen
 132      * does it on word boundaries, so is OK with this.  But VALGRIND will
 133      * still catch it and complain.  The masking trick does make the hash
 134      * noticably faster for short strings (like English words).
 135      */
 136     switch(length)
 137     {
 138     case 12: c+=k[2]; b+=k[1]; a+=k[0]; break;
 139     case 11: c+=k[2]&0xffffff; b+=k[1]; a+=k[0]; break;
 140     case 10: c+=k[2]&0xffff; b+=k[1]; a+=k[0]; break;
 141     case 9 : c+=k[2]&0xff; b+=k[1]; a+=k[0]; break;
 142     case 8 : b+=k[1]; a+=k[0]; break;
 143     case 7 : b+=k[1]&0xffffff; a+=k[0]; break;
 144     case 6 : b+=k[1]&0xffff; a+=k[0]; break;
 145     case 5 : b+=k[1]&0xff; a+=k[0]; break;
 146     case 4 : a+=k[0]; break;
 147     case 3 : a+=k[0]&0xffffff; break;
 148     case 2 : a+=k[0]&0xffff; break;
 149     case 1 : a+=k[0]&0xff; break;
 150     case 0 : return c;              /* zero length strings require no mixing */
 151     default: return c;
 152     }
 153
 154   }
 155   else if ((u.i & 0x1) == 0)
 156   {
 157     const uint16_t *k = (const uint16_t *)key;         /* read 16-bit chunks */
 158     const uint8_t  *k8;
 159
 160     /*--------------- all but last block: aligned reads and different mixing */
 161     while (length > 12)
 162     {
 163       a += k[0] + (((uint32_t)k[1])<<16);
 164       b += k[2] + (((uint32_t)k[3])<<16);
 165       c += k[4] + (((uint32_t)k[5])<<16);
 166       mix(a,b,c);
 167       length -= 12;
 168       k += 6;
 169     }
 170
 171     /*----------------------------- handle the last (probably partial) block */
 172     k8 = (const uint8_t *)k;
 173     switch(length)
 174     {
 175     case 12: c+=k[4]+(((uint32_t)k[5])<<16);
 176              b+=k[2]+(((uint32_t)k[3])<<16);
 177              a+=k[0]+(((uint32_t)k[1])<<16);
 178              break;
 179     case 11: c+=((uint32_t)k8[10])<<16;
 180              /* fall through */
 181     case 10: c+=k[4];
 182              b+=k[2]+(((uint32_t)k[3])<<16);
 183              a+=k[0]+(((uint32_t)k[1])<<16);
 184              break;
 185     case 9 : c+=k8[8];
 186              /* fall through */
 187     case 8 : b+=k[2]+(((uint32_t)k[3])<<16);
 188              a+=k[0]+(((uint32_t)k[1])<<16);
 189              break;
 190     case 7 : b+=((uint32_t)k8[6])<<16;
 191              /* fall through */
 192     case 6 : b+=k[2];
 193              a+=k[0]+(((uint32_t)k[1])<<16);
 194              break;
 195     case 5 : b+=k8[4];
 196              /* fall through */
 197     case 4 : a+=k[0]+(((uint32_t)k[1])<<16);
 198              break;
 199     case 3 : a+=((uint32_t)k8[2])<<16;
 200              /* fall through */
 201     case 2 : a+=k[0];
 202              break;
 203     case 1 : a+=k8[0];
 204              break;
 205     case 0 : return c;                     /* zero length requires no mixing */
 206     default: return c;
 207     }
 208
 209   }
 210   else
 211   {                        /* need to read the key one byte at a time */
 212 #endif /* little endian */
 213     const uint8_t *k = (const uint8_t *)key;
 214
 215     /*--------------- all but the last block: affect some 32 bits of (a,b,c) */
 216     while (length > 12)
 217     {
 218       a += k[0];
 219       a += ((uint32_t)k[1])<<8;
 220       a += ((uint32_t)k[2])<<16;
 221       a += ((uint32_t)k[3])<<24;
 222       b += k[4];
 223       b += ((uint32_t)k[5])<<8;
 224       b += ((uint32_t)k[6])<<16;
 225       b += ((uint32_t)k[7])<<24;
 226       c += k[8];
 227       c += ((uint32_t)k[9])<<8;
 228       c += ((uint32_t)k[10])<<16;
 229       c += ((uint32_t)k[11])<<24;
 230       mix(a,b,c);
 231       length -= 12;
 232       k += 12;
 233     }
 234
 235     /*-------------------------------- last block: affect all 32 bits of (c) */
 236     switch(length)                   /* all the case statements fall through */
 237     {
 238     case 12: c+=((uint32_t)k[11])<<24;
 239              /* fall through */
 240     case 11: c+=((uint32_t)k[10])<<16;
 241              /* fall through */
 242     case 10: c+=((uint32_t)k[9])<<8;
 243              /* fall through */
 244     case 9 : c+=k[8];
 245              /* fall through */
 246     case 8 : b+=((uint32_t)k[7])<<24;
 247              /* fall through */
 248     case 7 : b+=((uint32_t)k[6])<<16;
 249              /* fall through */
 250     case 6 : b+=((uint32_t)k[5])<<8;
 251              /* fall through */
 252     case 5 : b+=k[4];
 253              /* fall through */
 254     case 4 : a+=((uint32_t)k[3])<<24;
 255              /* fall through */
 256     case 3 : a+=((uint32_t)k[2])<<16;
 257              /* fall through */
 258     case 2 : a+=((uint32_t)k[1])<<8;
 259              /* fall through */
 260     case 1 : a+=k[0];
 261              break;
 262     case 0 : return c;
 263     default : return c;
 264     }
 265 #if !WORDS_BIGENDIAN
 266   }
 267 #endif
 268
 269   final(a,b,c);
 270   return c;
 271 }