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 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     case MEMCACHED_HASH_HSIEH:
  78     {
  79       hash= hsieh_hash(key, key_length);
  80       break;
  81     }
  82     case MEMCACHED_HASH_MURMUR:
  83     {
  84       hash= murmur_hash(key, key_length);
  85       break;
  86     }
  87   }
  88   return hash;
  89 }
  90
  91 uint32_t generate_hash(memcached_st *ptr, const char *key, size_t key_length)
  92 {
  93   uint32_t hash= 1; /* Just here to remove compile warning */
  94
  95
  96   WATCHPOINT_ASSERT(ptr->number_of_hosts);
  97
  98   if (ptr->number_of_hosts == 1)
  99     return 0;
 100
 101   hash= generate_hash_value(key, key_length, ptr->hash);
 102   WATCHPOINT_ASSERT(hash);
 103   return hash;
 104 }
 105
 106 unsigned int dispatch_host(memcached_st *ptr, uint32_t hash)
 107 {
 108   switch (ptr->distribution)
 109   {
 110   case MEMCACHED_DISTRIBUTION_CONSISTENT:
 111   case MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA:
 112     {
 113       uint32_t num= ptr->continuum_points_counter;
 114       WATCHPOINT_ASSERT(ptr->continuum);
 115
 116       hash= hash;
 117       memcached_continuum_item_st *begin, *end, *left, *right, *middle;
 118       begin= left= ptr->continuum;
 119       end= right= ptr->continuum + (num - 1);
 120
 121       while (1)
 122       {
 123         memcached_continuum_item_st *rmiddle;
 124
 125         middle = left + (right - left) / 2;
 126
 127         if (middle==end)
 128           return begin->index;
 129
 130         if (middle==begin)
 131           return end->index;
 132
 133         rmiddle = middle+1;
 134
 135         if (hash<rmiddle->value && hash>=middle->value)
 136           return middle->index;
 137
 138         if (middle->value < hash)
 139           left = middle + 1;
 140         else if (middle->value > hash)
 141           right = middle - 1;
 142
 143         if (left>right)
 144           return left->index;
 145       }
 146     }
 147     break;
 148   case MEMCACHED_DISTRIBUTION_MODULA:
 149     return hash % ptr->number_of_hosts;
 150   default:
 151     WATCHPOINT_ASSERT(0); /* We have added a distribution without extending the logic */
 152     return hash % ptr->number_of_hosts;
 153   }
 154
 155   WATCHPOINT_ASSERT(0); /* We should never reach here */
 156   return 0;
 157 }
 158
 159 /*
 160   One day make this public, and have it return the actual memcached_server_st
 161   to the calling application.
 162 */
 163 uint32_t memcached_generate_hash(memcached_st *ptr, const char *key, size_t key_length)
 164 {
 165   uint32_t hash= 1; /* Just here to remove compile warning */
 166
 167   WATCHPOINT_ASSERT(ptr->number_of_hosts);
 168
 169   if (ptr->number_of_hosts == 1)
 170     return 0;
 171
 172   hash = generate_hash(ptr, key, key_length);
 173
 174   WATCHPOINT_ASSERT(hash);
 175
 176   return dispatch_host(ptr, hash);
 177 }
 178
 179 static uint32_t internal_generate_hash(const char *key, size_t key_length)
 180 {
 181   const char *ptr= key;
 182   uint32_t value= 0;
 183
 184   while (--key_length)
 185   {
 186     value += *ptr++;
 187     value += (value << 10);
 188     value ^= (value >> 6);
 189   }
 190   value += (value << 3);
 191   value ^= (value >> 11);
 192   value += (value << 15);
 193
 194   return value == 0 ? 1 : value;
 195 }
 196
 197 static uint32_t internal_generate_md5(const char *key, size_t key_length)
 198 {
 199   unsigned char results[16];
 200
 201   md5_signature((unsigned char*)key, (unsigned int)key_length, results);
 202
 203   return ((uint32_t) (results[3] & 0xFF) << 24)
 204     | ((uint32_t) (results[2] & 0xFF) << 16)
 205     | ((uint32_t) (results[1] & 0xFF) << 8)
 206     | (results[0] & 0xFF);
 207 }