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     case MEMCACHED_HASH_JENKINS:
  88     {
  89       hash=jenkins_hash(key, key_length, 13);
  90       break;
  91     }
  92   }
  93   return hash;
  94 }
  95
  96 uint32_t generate_hash(memcached_st *ptr, const char *key, size_t key_length)
  97 {
  98   uint32_t hash= 1; /* Just here to remove compile warning */
  99
 100
 101   WATCHPOINT_ASSERT(ptr->number_of_hosts);
 102
 103   if (ptr->number_of_hosts == 1)
 104     return 0;
 105
 106   hash= generate_hash_value(key, key_length, ptr->hash);
 107   WATCHPOINT_ASSERT(hash);
 108   return hash;
 109 }
 110
 111 static uint32_t dispatch_host(memcached_st *ptr, uint32_t hash)
 112 {
 113   switch (ptr->distribution)
 114   {
 115   case MEMCACHED_DISTRIBUTION_CONSISTENT:
 116   case MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA:
 117     {
 118       uint32_t num= ptr->continuum_points_counter;
 119       WATCHPOINT_ASSERT(ptr->continuum);
 120
 121       hash= hash;
 122       memcached_continuum_item_st *begin, *end, *left, *right, *middle;
 123       begin= left= ptr->continuum;
 124       end= right= ptr->continuum + num;
 125
 126       while (left < right)
 127       {
 128         middle= left + (right - left) / 2;
 129         if (middle->value < hash)
 130           left= middle + 1;
 131         else
 132           right= middle;
 133       }
 134       if (right > end)
 135         right= begin;
 136       return right->index;
 137     }
 138     break;
 139   case MEMCACHED_DISTRIBUTION_MODULA:
 140     return hash % ptr->number_of_hosts;
 141   case MEMCACHED_DISTRIBUTION_RANDOM:
 142     return random() % ptr->number_of_hosts;
 143   default:
 144     WATCHPOINT_ASSERT(0); /* We have added a distribution without extending the logic */
 145     return hash % ptr->number_of_hosts;
 146   }
 147
 148   WATCHPOINT_ASSERT(0); /* We should never reach here */
 149   return 0;
 150 }
 151
 152 /*
 153   One day make this public, and have it return the actual memcached_server_st
 154   to the calling application.
 155 */
 156 uint32_t memcached_generate_hash(memcached_st *ptr, const char *key, size_t key_length)
 157 {
 158   uint32_t hash= 1; /* Just here to remove compile warning */
 159
 160   WATCHPOINT_ASSERT(ptr->number_of_hosts);
 161
 162   if (ptr->number_of_hosts == 1)
 163     return 0;
 164
 165   if (ptr->flags & MEM_HASH_WITH_PREFIX_KEY)
 166   {
 167     int temp_len= ptr->prefix_key_length + key_length;
 168     char *temp= (char *)malloc(temp_len);
 169     strncpy(temp, ptr->prefix_key, ptr->prefix_key_length);
 170     strncpy(temp + ptr->prefix_key_length, key, key_length);
 171     hash= generate_hash(ptr, temp, temp_len);
 172     free(temp);
 173   }
 174   else
 175   {
 176     hash= generate_hash(ptr, key, key_length);
 177   }
 178
 179   WATCHPOINT_ASSERT(hash);
 180
 181   return dispatch_host(ptr, hash);
 182 }
 183
 184 static uint32_t internal_generate_hash(const char *key, size_t key_length)
 185 {
 186   const char *ptr= key;
 187   uint32_t value= 0;
 188
 189   while (--key_length)
 190   {
 191     value += *ptr++;
 192     value += (value << 10);
 193     value ^= (value >> 6);
 194   }
 195   value += (value << 3);
 196   value ^= (value >> 11);
 197   value += (value << 15);
 198
 199   return value == 0 ? 1 : value;
 200 }
 201
 202 static uint32_t internal_generate_md5(const char *key, size_t key_length)
 203 {
 204   unsigned char results[16];
 205
 206   md5_signature((unsigned char*)key, (unsigned int)key_length, results);
 207
 208   return ((uint32_t) (results[3] & 0xFF) << 24)
 209     | ((uint32_t) (results[2] & 0xFF) << 16)
 210     | ((uint32_t) (results[1] & 0xFF) << 8)
 211     | (results[0] & 0xFF);
 212 }