git.m6w6.name Git - m6w6/libmemcached/blob - lib/memcached_hash.c

   1 #include "common.h"
   2
   3 /* Prototypes */
   4 static unsigned int internal_generate_hash(char *key, size_t key_length);
   5
   6 unsigned int memcached_generate_hash(memcached_st *ptr, char *key, size_t key_length)
   7 {
   8   unsigned int hash;
   9
  10   if (ptr->flags & MEM_USE_MD5)
  11   {
  12     unsigned char results[16];
  13
  14     md5_signature((unsigned char*)key, (unsigned int)key_length, results);
  15
  16     hash= (unsigned int)(( results[3] << 24 )
  17                                  | ( results[2] << 16 )
  18                                  | ( results[1] <<  8 )
  19                                  |   results[0] );
  20   }
  21   else
  22     hash= internal_generate_hash(key, key_length);
  23
  24   if (ptr->flags & MEM_USE_KETAMA)
  25     assert(0);
  26   else
  27     return hash % ptr->number_of_hosts;
  28 }
  29
  30 static unsigned int internal_generate_hash(char *key, size_t key_length)
  31 {
  32   char *ptr= key;
  33   unsigned int value= 0;
  34
  35   while (--key_length)
  36   {
  37     value += *ptr++;
  38     value += (value << 10);
  39     value ^= (value >> 6);
  40   }
  41   value += (value << 3);
  42   value ^= (value >> 11);
  43   value += (value << 15);
  44
  45   return value == 0 ? 1 : value;
  46 }