git.m6w6.name Git - m6w6/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 uint64_t internal_generate_hash(char *key, size_t key_length);
  12 static uint64_t internal_generate_md5(char *key, size_t key_length);
  13 static uint64_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   uint64_t hash= 1; /* Just here to remove compile warning */
  18   unsigned int x;
  19
  20   WATCHPOINT_ASSERT(ptr->number_of_hosts);
  21
  22   switch (ptr->hash)
  23   {
  24   case MEMCACHED_HASH_DEFAULT:
  25     hash= internal_generate_hash(key, key_length);
  26     break;
  27   case MEMCACHED_HASH_MD5:
  28     hash= internal_generate_md5(key, key_length);
  29     break;
  30   case MEMCACHED_HASH_CRC:
  31     hash= ((hash_crc32(key, key_length) >> 16) & 0x7fff);
  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       hash= FNV_64_INIT;
  38       for (x= 0; x < key_length; x++)
  39       {
  40         hash *= FNV_64_PRIME;
  41         hash ^= key[x];
  42       }
  43     }
  44     break;
  45   case MEMCACHED_HASH_FNV1A_64:
  46     {
  47       hash= FNV_64_INIT;
  48       for (x= 0; x < key_length; x++)
  49       {
  50         hash ^= key[x];
  51         hash *= FNV_64_PRIME;
  52       }
  53     }
  54     break;
  55   case MEMCACHED_HASH_FNV1_32:
  56     {
  57       hash= FNV_32_INIT;
  58       for (x= 0; x < key_length; x++)
  59       {
  60         hash *= FNV_32_PRIME;
  61         hash ^= key[x];
  62       }
  63     }
  64     break;
  65   case MEMCACHED_HASH_FNV1A_32:
  66     {
  67       hash= FNV_32_INIT;
  68       for (x= 0; x < key_length; x++)
  69       {
  70         hash ^= key[x];
  71         hash *= FNV_32_PRIME;
  72       }
  73     }
  74     break;
  75     case MEMCACHED_HASH_KETAMA:
  76     {
  77       hash= internal_generate_ketama_md5(key, key_length);
  78       break;
  79     }
  80     case MEMCACHED_HASH_HSIEH:
  81     {
  82       hash= hsieh_hash(key, key_length);
  83       break;
  84     }
  85   }
  86
  87   WATCHPOINT_ASSERT(hash);
  88
  89   if (ptr->distribution == MEMCACHED_DISTRIBUTION_MODULA)
  90   {
  91     return hash % ptr->number_of_hosts;
  92   }
  93   else
  94   {
  95     unsigned int server_key;
  96
  97     server_key= hash % MEMCACHED_WHEEL_SIZE;
  98
  99     return ptr->wheel[server_key];
 100   }
 101 }
 102
 103 static uint64_t internal_generate_hash(char *key, size_t key_length)
 104 {
 105   char *ptr= key;
 106   uint64_t value= 0;
 107
 108   while (--key_length)
 109   {
 110     value += *ptr++;
 111     value += (value << 10);
 112     value ^= (value >> 6);
 113   }
 114   value += (value << 3);
 115   value ^= (value >> 11);
 116   value += (value << 15);
 117
 118   return value == 0 ? 1 : value;
 119 }
 120
 121 static uint64_t internal_generate_md5(char *key, size_t key_length)
 122 {
 123   unsigned char results[16];
 124
 125   md5_signature((unsigned char*)key, (unsigned int)key_length, results);
 126
 127   return (uint64_t)(( results[3] << 24 )
 128                     | ( results[2] << 16 )
 129                     | ( results[1] <<  8 )
 130                     |   results[0] );
 131 }
 132
 133 static uint64_t internal_generate_ketama_md5(char *key, size_t key_length)
 134 {
 135   unsigned char results[16];
 136
 137   md5_signature((unsigned char*)key, (unsigned int)key_length, results);
 138
 139   return ((uint32_t) (results[3] & 0xFF) << 24)
 140     | ((uint32_t) (results[2] & 0xFF) << 16)
 141     | ((uint32_t) (results[1] & 0xFF) << 8)
 142     | (results[0] & 0xFF);
 143 }