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

   1 #include "common.h"
   2
   3 /* Defines */
   4 static uint64_t FNV_64_INIT= 0xcbf29ce484222325L;
   5 static uint64_t FNV_64_PRIME= 0x100000001b3L;
   6
   7 static uint32_t FNV_32_INIT= 2166136261L;
   8 static uint32_t FNV_32_PRIME= 16777619;
   9
  10 /* Prototypes */
  11 static unsigned int internal_generate_hash(char *key, size_t key_length);
  12 static uint32_t internal_generate_md5(char *key, size_t key_length);
  13 static uint32_t internal_generate_md5(char *key, size_t key_length);
  14
  15 unsigned int memcached_generate_hash(memcached_st *ptr, char *key, size_t key_length)
  16 {
  17   uint32_t hash;
  18
  19   switch (ptr->hash)
  20   {
  21   case MEMCACHED_HASH_DEFAULT:
  22     hash= internal_generate_hash(key, key_length);
  23     break;
  24   case MEMCACHED_HASH_MD5:
  25     hash= internal_generate_md5(key, key_length);
  26     break;
  27   case MEMCACHED_HASH_CRC:
  28     hash= hash_crc32(key, key_length);
  29     break;
  30   }
  31
  32   if (ptr->flags & MEM_USE_KETAMA)
  33   {
  34     WATCHPOINT_ASSERT(0);
  35     return 0;
  36   }
  37   else
  38     return hash % ptr->number_of_hosts;
  39 }
  40
  41 static uint32_t internal_generate_hash(char *key, size_t key_length)
  42 {
  43   char *ptr= key;
  44   unsigned int value= 0;
  45
  46   while (--key_length)
  47   {
  48     value += *ptr++;
  49     value += (value << 10);
  50     value ^= (value >> 6);
  51   }
  52   value += (value << 3);
  53   value ^= (value >> 11);
  54   value += (value << 15);
  55
  56   return value == 0 ? 1 : value;
  57 }
  58
  59 static uint32_t internal_generate_md5(char *key, size_t key_length)
  60 {
  61   unsigned char results[16];
  62
  63   md5_signature((unsigned char*)key, (unsigned int)key_length, results);
  64
  65   return (uint32_t)(( results[3] << 24 )
  66                     | ( results[2] << 16 )
  67                     | ( results[1] <<  8 )
  68                     |   results[0] );
  69 }