hash.c

   1 #include <stdint.h>
   2 #include <stdlib.h>
   3 #include "hash.h"
   4
   5 //-----------------------------------------------------------------------------
   6 // MurmurHashNeutral2, by Austin Appleby
   7
   8 // Same as MurmurHash2, but endian- and alignment-neutral.
   9 uint32_t hash_murmur2(const void * key, int len)
  10 {
  11         const unsigned int seed = 0xdeadc0de;
  12         const unsigned int m = 0x5bd1e995;
  13         const int r = 24;
  14
  15         unsigned int h = seed ^ len;
  16
  17         const unsigned char * data = (const unsigned char *)key;
  18
  19         while(len >= 4)
  20         {
  21                 unsigned int k;
  22
  23                 k  = data[0];
  24                 k |= data[1] << 8;
  25                 k |= data[2] << 16;
  26                 k |= data[3] << 24;
  27
  28                 k *= m;
  29                 k ^= k >> r;
  30                 k *= m;
  31
  32                 h *= m;
  33                 h ^= k;
  34
  35                 data += 4;
  36                 len -= 4;
  37         }
  38
  39         switch(len)
  40         {
  41         case 3: h ^= data[2] << 16;
  42         case 2: h ^= data[1] << 8;
  43         case 1: h ^= data[0];
  44                 h *= m;
  45         };
  46
  47         h ^= h >> 13;
  48         h *= m;
  49         h ^= h >> 15;
  50
  51         return h;
  52 }
  53
  54