ext/tdb/fnv.c

   1 #include "rbtdb.h"
   2
   3 #define FNV1A_32A_INIT (unsigned int)0x811c9dc5
   4 #define FNV_32_PRIME (unsigned int)0x01000193
   5
   6 unsigned int rbtdb_fnv1a(TDB_DATA * data)
   7 {
   8         unsigned char *bp = data->dptr;
   9         unsigned char *be = bp + data->dsize;
  10         unsigned int h = FNV1A_32A_INIT;
  11
  12         /* FNV-1a hash each octet in the buffer */
  13         while (bp < be) {
  14
  15                 /* xor the bottom with the current octet */
  16                 h ^= (unsigned)*bp++;
  17
  18                 /* multiply by the 32 bit FNV magic prime mod 2^32 */
  19 #if defined(NO_FNV_GCC_OPTIMIZATION)
  20                 h *= FNV_32_PRIME;
  21 #else
  22                 h += (h << 1) + (h << 4) + (h << 7) + (h << 8) + (h << 24);
  23 #endif
  24         }
  25
  26         /* return our new hash value */
  27         return h;
  28 }