git.m6w6.name Git - awesomized/libmemcached/blob - lib/murmur_hash.c

   1 #include "common.h"
   2
   3 /*
   4   "Murmur"hash provided by Austin, tanjent@gmail.com
   5 #define MURMUR_POSTMIX
   6 */
   7
   8 uint32_t murmur_hash(char *key, size_t length)
   9 {
  10   const unsigned int m= 0x7fd652ad;
  11   const int r= 16;
  12
  13   uint32_t h= 0xdeadbeef;
  14
  15   while(length >= 4)
  16   {
  17     h += *(unsigned int *)key;
  18     h *= m;
  19     h ^= h >> r;
  20
  21     key += 4;
  22     length -= 4;
  23   }
  24
  25   switch(length)
  26   {
  27   case 3:
  28     h += key[2] << 16;
  29   case 2:
  30     h += key[1] << 8;
  31   case 1:
  32   default:
  33     h += key[0];
  34     h *= m;
  35     h ^= h >> r;
  36   };
  37
  38 #ifdef MURMUR_POSTMIX
  39
  40   h *= m;
  41   h ^= h >> 10;
  42   h *= m;
  43   h ^= h >> 17;
  44
  45 #endif
  46
  47   return h;
  48 }