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= 0xcbf29ce484222325LL;
   5 static uint64_t FNV_64_PRIME= 0x100000001b3LL;
   6
   7 static uint32_t FNV_32_INIT= 2166136261UL;
   8 static uint32_t FNV_32_PRIME= 16777619;
   9
  10 /* Prototypes */
  11 static uint32_t 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_ketama_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= 1; /* Just here to remove compile warning */
  18   unsigned int x;
  19
  20   WATCHPOINT_ASSERT(ptr->number_of_hosts);
  21
  22   if (ptr->number_of_hosts == 1)
  23     return 0;
  24
  25   switch (ptr->hash)
  26   {
  27   case MEMCACHED_HASH_DEFAULT:
  28     hash= internal_generate_hash(key, key_length);
  29     break;
  30   case MEMCACHED_HASH_MD5:
  31     hash= internal_generate_md5(key, key_length);
  32     break;
  33   case MEMCACHED_HASH_CRC:
  34     hash= ((hash_crc32(key, key_length) >> 16) & 0x7fff);
  35     if (hash == 0)
  36       hash= 1;
  37     break;
  38     /* FNV hash'es lifted from Dustin Sallings work */
  39   case MEMCACHED_HASH_FNV1_64:
  40     {
  41       /* Thanks to pierre@demartines.com for the pointer */
  42       uint64_t temp_hash;
  43
  44       temp_hash= FNV_64_INIT;
  45       for (x= 0; x < key_length; x++)
  46       {
  47         temp_hash *= FNV_64_PRIME;
  48         temp_hash ^= key[x];
  49       }
  50       hash= (uint32_t)temp_hash;
  51     }
  52     break;
  53   case MEMCACHED_HASH_FNV1A_64:
  54     {
  55       hash= FNV_64_INIT;
  56       for (x= 0; x < key_length; x++)
  57       {
  58         hash ^= key[x];
  59         hash *= FNV_64_PRIME;
  60       }
  61     }
  62     break;
  63   case MEMCACHED_HASH_FNV1_32:
  64     {
  65       hash= FNV_32_INIT;
  66       for (x= 0; x < key_length; x++)
  67       {
  68         hash *= FNV_32_PRIME;
  69         hash ^= key[x];
  70       }
  71     }
  72     break;
  73   case MEMCACHED_HASH_FNV1A_32:
  74     {
  75       hash= FNV_32_INIT;
  76       for (x= 0; x < key_length; x++)
  77       {
  78         hash ^= key[x];
  79         hash *= FNV_32_PRIME;
  80       }
  81     }
  82     break;
  83     case MEMCACHED_HASH_KETAMA:
  84     {
  85       hash= internal_generate_ketama_md5(key, key_length);
  86       break;
  87     }
  88     case MEMCACHED_HASH_HSIEH:
  89     {
  90       hash= hsieh_hash(key, key_length);
  91       break;
  92     }
  93   }
  94
  95   WATCHPOINT_ASSERT(hash);
  96
  97   if (ptr->distribution == MEMCACHED_DISTRIBUTION_MODULA)
  98   {
  99     return hash % ptr->number_of_hosts;
 100   }
 101   else
 102   {
 103     unsigned int server_key;
 104
 105     server_key= hash % MEMCACHED_WHEEL_SIZE;
 106
 107     return ptr->wheel[server_key];
 108   }
 109 }
 110
 111 static uint32_t internal_generate_hash(char *key, size_t key_length)
 112 {
 113   char *ptr= key;
 114   uint32_t value= 0;
 115
 116   while (--key_length)
 117   {
 118     value += *ptr++;
 119     value += (value << 10);
 120     value ^= (value >> 6);
 121   }
 122   value += (value << 3);
 123   value ^= (value >> 11);
 124   value += (value << 15);
 125
 126   return value == 0 ? 1 : value;
 127 }
 128
 129 static uint32_t internal_generate_md5(char *key, size_t key_length)
 130 {
 131   unsigned char results[16];
 132
 133   md5_signature((unsigned char*)key, (unsigned int)key_length, results);
 134
 135   return (uint32_t)(( results[3] << 24 )
 136                     | ( results[2] << 16 )
 137                     | ( results[1] <<  8 )
 138                     |   results[0] );
 139 }
 140
 141 static uint32_t internal_generate_ketama_md5(char *key, size_t key_length)
 142 {
 143   unsigned char results[16];
 144
 145   md5_signature((unsigned char*)key, (unsigned int)key_length, results);
 146
 147   return ((uint32_t) (results[3] & 0xFF) << 24)
 148     | ((uint32_t) (results[2] & 0xFF) << 16)
 149     | ((uint32_t) (results[1] & 0xFF) << 8)
 150     | (results[0] & 0xFF);
 151 }