git.m6w6.name Git - awesomized/libmemcached/blob - libmemcached/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(const char *key, size_t key_length);
  12 static uint32_t internal_generate_md5(const char *key, size_t key_length);
  13
  14 uint32_t memcached_generate_hash_value(const char *key, size_t key_length, memcached_hash hash_algorithm)
  15 {
  16   uint32_t hash= 1; /* Just here to remove compile warning */
  17   uint32_t x= 0;
  18
  19   switch (hash_algorithm)
  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) >> 16) & 0x7fff);
  29     if (hash == 0)
  30       hash= 1;
  31     break;
  32     /* FNV hash'es lifted from Dustin Sallings work */
  33   case MEMCACHED_HASH_FNV1_64:
  34     {
  35       /* Thanks to pierre@demartines.com for the pointer */
  36       uint64_t temp_hash;
  37
  38       temp_hash= FNV_64_INIT;
  39       for (x= 0; x < key_length; x++)
  40       {
  41         temp_hash *= FNV_64_PRIME;
  42         temp_hash ^= key[x];
  43       }
  44       hash= (uint32_t)temp_hash;
  45     }
  46     break;
  47   case MEMCACHED_HASH_FNV1A_64:
  48     {
  49       hash= FNV_64_INIT;
  50       for (x= 0; x < key_length; x++)
  51       {
  52         hash ^= key[x];
  53         hash *= FNV_64_PRIME;
  54       }
  55     }
  56     break;
  57   case MEMCACHED_HASH_FNV1_32:
  58     {
  59       hash= FNV_32_INIT;
  60       for (x= 0; x < key_length; x++)
  61       {
  62         hash *= FNV_32_PRIME;
  63         hash ^= key[x];
  64       }
  65     }
  66     break;
  67   case MEMCACHED_HASH_FNV1A_32:
  68     {
  69       hash= FNV_32_INIT;
  70       for (x= 0; x < key_length; x++)
  71       {
  72         hash ^= key[x];
  73         hash *= FNV_32_PRIME;
  74       }
  75     }
  76     break;
  77 #ifdef HAVE_HSIEH_HASH
  78     case MEMCACHED_HASH_HSIEH:
  79     {
  80       hash= hsieh_hash(key, key_length);
  81       break;
  82     }
  83 #endif
  84     case MEMCACHED_HASH_MURMUR:
  85     {
  86       hash= murmur_hash(key, key_length);
  87       break;
  88     }
  89     case MEMCACHED_HASH_JENKINS:
  90     {
  91       hash=jenkins_hash(key, key_length, 13);
  92       break;
  93     }
  94   }
  95   return hash;
  96 }
  97
  98 uint32_t generate_hash(memcached_st *ptr, const char *key, size_t key_length)
  99 {
 100   uint32_t hash= 1; /* Just here to remove compile warning */
 101
 102
 103   WATCHPOINT_ASSERT(ptr->number_of_hosts);
 104
 105   if (ptr->number_of_hosts == 1)
 106     return 0;
 107
 108   hash= memcached_generate_hash_value(key, key_length, ptr->hash);
 109   WATCHPOINT_ASSERT(hash);
 110   return hash;
 111 }
 112
 113 static uint32_t dispatch_host(memcached_st *ptr, uint32_t hash)
 114 {
 115   switch (ptr->distribution)
 116   {
 117   case MEMCACHED_DISTRIBUTION_CONSISTENT:
 118   case MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA:
 119     {
 120       uint32_t num= ptr->continuum_points_counter;
 121       WATCHPOINT_ASSERT(ptr->continuum);
 122
 123       hash= hash;
 124       memcached_continuum_item_st *begin, *end, *left, *right, *middle;
 125       begin= left= ptr->continuum;
 126       end= right= ptr->continuum + num;
 127
 128       while (left < right)
 129       {
 130         middle= left + (right - left) / 2;
 131         if (middle->value < hash)
 132           left= middle + 1;
 133         else
 134           right= middle;
 135       }
 136       if (right == end)
 137         right= begin;
 138       return right->index;
 139     }
 140     break;
 141   case MEMCACHED_DISTRIBUTION_MODULA:
 142     return hash % ptr->number_of_hosts;
 143   case MEMCACHED_DISTRIBUTION_RANDOM:
 144     return random() % ptr->number_of_hosts;
 145   default:
 146     WATCHPOINT_ASSERT(0); /* We have added a distribution without extending the logic */
 147     return hash % ptr->number_of_hosts;
 148   }
 149
 150   /* NOTREACHED */
 151 }
 152
 153 /*
 154   One day make this public, and have it return the actual memcached_server_st
 155   to the calling application.
 156 */
 157 uint32_t memcached_generate_hash(memcached_st *ptr, const char *key, size_t key_length)
 158 {
 159   uint32_t hash= 1; /* Just here to remove compile warning */
 160
 161   WATCHPOINT_ASSERT(ptr->number_of_hosts);
 162
 163   if (ptr->number_of_hosts == 1)
 164     return 0;
 165
 166   if (ptr->flags & MEM_HASH_WITH_PREFIX_KEY)
 167   {
 168     int temp_len= ptr->prefix_key_length + key_length;
 169     char *temp= (char *)malloc(temp_len);
 170     strncpy(temp, ptr->prefix_key, ptr->prefix_key_length);
 171     strncpy(temp + ptr->prefix_key_length, key, key_length);
 172     hash= generate_hash(ptr, temp, temp_len);
 173     free(temp);
 174   }
 175   else
 176   {
 177     hash= generate_hash(ptr, key, key_length);
 178   }
 179
 180   WATCHPOINT_ASSERT(hash);
 181
 182   return dispatch_host(ptr, hash);
 183 }
 184
 185 static uint32_t internal_generate_hash(const char *key, size_t key_length)
 186 {
 187   const char *ptr= key;
 188   uint32_t value= 0;
 189
 190   while (key_length--)
 191   {
 192     value += *ptr++;
 193     value += (value << 10);
 194     value ^= (value >> 6);
 195   }
 196   value += (value << 3);
 197   value ^= (value >> 11);
 198   value += (value << 15);
 199
 200   return value == 0 ? 1 : value;
 201 }
 202
 203 static uint32_t internal_generate_md5(const char *key, size_t key_length)
 204 {
 205   unsigned char results[16];
 206
 207   md5_signature((unsigned char*)key, (unsigned int)key_length, results);
 208
 209   return ((uint32_t) (results[3] & 0xFF) << 24)
 210     | ((uint32_t) (results[2] & 0xFF) << 16)
 211     | ((uint32_t) (results[1] & 0xFF) << 8)
 212     | (results[0] & 0xFF);
 213 }