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

   1 #include "common.h"
   2
   3
   4 /* Defines */
   5 static uint64_t FNV_64_INIT= UINT64_C(0xcbf29ce484222325);
   6 static uint64_t FNV_64_PRIME= UINT64_C(0x100000001b3);
   7
   8 static uint32_t FNV_32_INIT= 2166136261UL;
   9 static uint32_t FNV_32_PRIME= 16777619;
  10
  11 /* Prototypes */
  12 static uint32_t internal_generate_hash(const char *key, size_t key_length);
  13 static uint32_t internal_generate_md5(const char *key, size_t key_length);
  14
  15 uint32_t memcached_generate_hash_value(const char *key, size_t key_length, memcached_hash hash_algorithm)
  16 {
  17   uint32_t hash= 1; /* Just here to remove compile warning */
  18   uint32_t x= 0;
  19
  20   switch (hash_algorithm)
  21   {
  22   case MEMCACHED_HASH_DEFAULT:
  23     hash= internal_generate_hash(key, key_length);
  24     break;
  25   case MEMCACHED_HASH_MD5:
  26     hash= internal_generate_md5(key, key_length);
  27     break;
  28   case MEMCACHED_HASH_CRC:
  29     hash= ((hash_crc32(key, key_length) >> 16) & 0x7fff);
  30     if (hash == 0)
  31       hash= 1;
  32     break;
  33     /* FNV hash'es lifted from Dustin Sallings work */
  34   case MEMCACHED_HASH_FNV1_64:
  35     {
  36       /* Thanks to pierre@demartines.com for the pointer */
  37       uint64_t temp_hash;
  38
  39       temp_hash= FNV_64_INIT;
  40       for (x= 0; x < key_length; x++)
  41       {
  42         temp_hash *= FNV_64_PRIME;
  43         temp_hash ^= (uint64_t)key[x];
  44       }
  45       hash= (uint32_t)temp_hash;
  46     }
  47     break;
  48   case MEMCACHED_HASH_FNV1A_64:
  49     {
  50       hash= (uint32_t) FNV_64_INIT;
  51       for (x= 0; x < key_length; x++)
  52       {
  53         uint32_t val= (uint32_t)key[x];
  54         hash ^= val;
  55         hash *= (uint32_t) FNV_64_PRIME;
  56       }
  57     }
  58     break;
  59   case MEMCACHED_HASH_FNV1_32:
  60     {
  61       hash= FNV_32_INIT;
  62       for (x= 0; x < key_length; x++)
  63       {
  64         uint32_t val= (uint32_t)key[x];
  65         hash *= FNV_32_PRIME;
  66         hash ^= val;
  67       }
  68     }
  69     break;
  70   case MEMCACHED_HASH_FNV1A_32:
  71     {
  72       hash= FNV_32_INIT;
  73       for (x= 0; x < key_length; x++)
  74       {
  75         uint32_t val= (uint32_t)key[x];
  76         hash ^= val;
  77         hash *= FNV_32_PRIME;
  78       }
  79     }
  80     break;
  81     case MEMCACHED_HASH_HSIEH:
  82     {
  83 #ifdef HAVE_HSIEH_HASH
  84       hash= hsieh_hash(key, key_length);
  85 #endif
  86       break;
  87     }
  88     case MEMCACHED_HASH_MURMUR:
  89     {
  90       hash= murmur_hash(key, key_length);
  91       break;
  92     }
  93     case MEMCACHED_HASH_JENKINS:
  94     {
  95       hash=jenkins_hash(key, key_length, 13);
  96       break;
  97     }
  98     default:
  99     {
 100       WATCHPOINT_ASSERT(hash_algorithm);
 101       break;
 102     }
 103   }
 104   return hash;
 105 }
 106
 107 uint32_t generate_hash(memcached_st *ptr, const char *key, size_t key_length)
 108 {
 109   uint32_t hash= 1; /* Just here to remove compile warning */
 110
 111
 112   WATCHPOINT_ASSERT(ptr->number_of_hosts);
 113
 114   if (ptr->number_of_hosts == 1)
 115     return 0;
 116
 117   hash= memcached_generate_hash_value(key, key_length, ptr->hash);
 118   WATCHPOINT_ASSERT(hash);
 119   return hash;
 120 }
 121
 122 static uint32_t dispatch_host(memcached_st *ptr, uint32_t hash)
 123 {
 124   switch (ptr->distribution)
 125   {
 126   case MEMCACHED_DISTRIBUTION_CONSISTENT:
 127   case MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA:
 128     {
 129       uint32_t num= ptr->continuum_points_counter;
 130       WATCHPOINT_ASSERT(ptr->continuum);
 131
 132       hash= hash;
 133       memcached_continuum_item_st *begin, *end, *left, *right, *middle;
 134       begin= left= ptr->continuum;
 135       end= right= ptr->continuum + num;
 136
 137       while (left < right)
 138       {
 139         middle= left + (right - left) / 2;
 140         if (middle->value < hash)
 141           left= middle + 1;
 142         else
 143           right= middle;
 144       }
 145       if (right == end)
 146         right= begin;
 147       return right->index;
 148     }
 149   case MEMCACHED_DISTRIBUTION_MODULA:
 150     return hash % ptr->number_of_hosts;
 151   case MEMCACHED_DISTRIBUTION_RANDOM:
 152     return (uint32_t) random() % ptr->number_of_hosts;
 153   default:
 154     WATCHPOINT_ASSERT(0); /* We have added a distribution without extending the logic */
 155     return hash % ptr->number_of_hosts;
 156   }
 157
 158   /* NOTREACHED */
 159 }
 160
 161 /*
 162   One day make this public, and have it return the actual memcached_server_st
 163   to the calling application.
 164 */
 165 uint32_t memcached_generate_hash(memcached_st *ptr, const char *key, size_t key_length)
 166 {
 167   uint32_t hash= 1; /* Just here to remove compile warning */
 168
 169   WATCHPOINT_ASSERT(ptr->number_of_hosts);
 170
 171   if (ptr->number_of_hosts == 1)
 172     return 0;
 173
 174   if (ptr->flags & MEM_HASH_WITH_PREFIX_KEY)
 175   {
 176     size_t temp_length= ptr->prefix_key_length + key_length;
 177     char temp[temp_length];
 178
 179     if (temp_length > MEMCACHED_MAX_KEY -1)
 180       return 0;
 181
 182     strncpy(temp, ptr->prefix_key, ptr->prefix_key_length);
 183     strncpy(temp + ptr->prefix_key_length, key, key_length);
 184     hash= generate_hash(ptr, temp, temp_length);
 185   }
 186   else
 187   {
 188     hash= generate_hash(ptr, key, key_length);
 189   }
 190
 191   WATCHPOINT_ASSERT(hash);
 192
 193   if (memcached_behavior_get(ptr, MEMCACHED_BEHAVIOR_AUTO_EJECT_HOSTS) && ptr->next_distribution_rebuild) {
 194     struct timeval now;
 195
 196     if (gettimeofday(&now, NULL) == 0 &&
 197         now.tv_sec > ptr->next_distribution_rebuild)
 198       run_distribution(ptr);
 199   }
 200
 201   return dispatch_host(ptr, hash);
 202 }
 203
 204 static uint32_t internal_generate_hash(const char *key, size_t key_length)
 205 {
 206   const char *ptr= key;
 207   uint32_t value= 0;
 208
 209   while (key_length--)
 210   {
 211     uint32_t val= (uint32_t) *ptr++;
 212     value += val;
 213     value += (value << 10);
 214     value ^= (value >> 6);
 215   }
 216   value += (value << 3);
 217   value ^= (value >> 11);
 218   value += (value << 15);
 219
 220   return value == 0 ? 1 : (uint32_t) value;
 221 }
 222
 223 static uint32_t internal_generate_md5(const char *key, size_t key_length)
 224 {
 225   unsigned char results[16];
 226
 227   md5_signature((unsigned char*)key, (unsigned int)key_length, results);
 228
 229   return ((uint32_t) (results[3] & 0xFF) << 24)
 230     | ((uint32_t) (results[2] & 0xFF) << 16)
 231     | ((uint32_t) (results[1] & 0xFF) << 8)
 232     | (results[0] & 0xFF);
 233 }