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

   1 /* LibMemcached
   2  * Copyright (C) 2006-2010 Brian Aker
   3  * All rights reserved.
   4  *
   5  * Use and distribution licensed under the BSD license.  See
   6  * the COPYING file in the parent directory for full text.
   7  *
   8  * Summary:
   9  *
  10  */
  11
  12 #include "common.h"
  13
  14
  15 uint32_t memcached_generate_hash_value(const char *key, size_t key_length, memcached_hash_t hash_algorithm)
  16 {
  17   return libhashkit_digest(key, key_length, (hashkit_hash_algorithm_t)hash_algorithm);
  18 }
  19
  20 static inline uint32_t generate_hash(const memcached_st *ptr, const char *key, size_t key_length)
  21 {
  22   return hashkit_digest(&ptr->hashkit, key, key_length);
  23 }
  24
  25 static uint32_t dispatch_host(const memcached_st *ptr, uint32_t hash)
  26 {
  27   switch (ptr->distribution)
  28   {
  29   case MEMCACHED_DISTRIBUTION_CONSISTENT:
  30   case MEMCACHED_DISTRIBUTION_CONSISTENT_WEIGHTED:
  31   case MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA:
  32   case MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA_SPY:
  33     {
  34       uint32_t num= ptr->ketama.continuum_points_counter;
  35       WATCHPOINT_ASSERT(ptr->continuum);
  36
  37       hash= hash;
  38       memcached_continuum_item_st *begin, *end, *left, *right, *middle;
  39       begin= left= ptr->ketama.continuum;
  40       end= right= ptr->ketama.continuum + num;
  41
  42       while (left < right)
  43       {
  44         middle= left + (right - left) / 2;
  45         if (middle->value < hash)
  46           left= middle + 1;
  47         else
  48           right= middle;
  49       }
  50       if (right == end)
  51         right= begin;
  52       return right->index;
  53     }
  54   case MEMCACHED_DISTRIBUTION_MODULA:
  55     return hash % memcached_server_count(ptr);
  56   case MEMCACHED_DISTRIBUTION_RANDOM:
  57     return (uint32_t) random() % memcached_server_count(ptr);
  58   case MEMCACHED_DISTRIBUTION_CONSISTENT_MAX:
  59   default:
  60     WATCHPOINT_ASSERT(0); /* We have added a distribution without extending the logic */
  61     return hash % memcached_server_count(ptr);
  62   }
  63   /* NOTREACHED */
  64 }
  65
  66 /*
  67   One version is public and will not modify the distribution hash, the other will.
  68 */
  69 static inline uint32_t _generate_hash_wrapper(const memcached_st *ptr, const char *key, size_t key_length)
  70 {
  71   WATCHPOINT_ASSERT(memcached_server_count(ptr));
  72
  73   if (memcached_server_count(ptr) == 1)
  74     return 0;
  75
  76   if (ptr->flags.hash_with_prefix_key)
  77   {
  78     size_t temp_length= memcached_array_size(ptr->prefix_key) + key_length;
  79     char temp[temp_length];
  80
  81     if (temp_length > MEMCACHED_MAX_KEY -1)
  82       return 0;
  83
  84     strncpy(temp, memcached_array_string(ptr->prefix_key), memcached_array_size(ptr->prefix_key));
  85     strncpy(temp + memcached_array_size(ptr->prefix_key), key, key_length);
  86
  87     return generate_hash(ptr, temp, temp_length);
  88   }
  89   else
  90   {
  91     return generate_hash(ptr, key, key_length);
  92   }
  93 }
  94
  95 static inline void _regen_for_auto_eject(memcached_st *ptr)
  96 {
  97   if (_is_auto_eject_host(ptr) && ptr->ketama.next_distribution_rebuild)
  98   {
  99     struct timeval now;
 100
 101     if (gettimeofday(&now, NULL) == 0 &&
 102         now.tv_sec > ptr->ketama.next_distribution_rebuild)
 103     {
 104       run_distribution(ptr);
 105     }
 106   }
 107 }
 108
 109 void memcached_autoeject(memcached_st *ptr)
 110 {
 111   _regen_for_auto_eject(ptr);
 112 }
 113
 114 uint32_t memcached_generate_hash_with_redistribution(memcached_st *ptr, const char *key, size_t key_length)
 115 {
 116   uint32_t hash= _generate_hash_wrapper(ptr, key, key_length);
 117
 118   _regen_for_auto_eject(ptr);
 119
 120   return dispatch_host(ptr, hash);
 121 }
 122
 123 uint32_t memcached_generate_hash(const memcached_st *ptr, const char *key, size_t key_length)
 124 {
 125   return dispatch_host(ptr, _generate_hash_wrapper(ptr, key, key_length));
 126 }
 127
 128 const hashkit_st *memcached_get_hashkit(const memcached_st *ptr)
 129 {
 130   return &ptr->hashkit;
 131 }
 132
 133 memcached_return_t memcached_set_hashkit(memcached_st *self, hashkit_st *hashk)
 134 {
 135   hashkit_free(&self->hashkit);
 136   hashkit_clone(&self->hashkit, hashk);
 137
 138   return MEMCACHED_SUCCESS;
 139 }
 140
 141 const char * libmemcached_string_hash(memcached_hash_t type)
 142 {
 143   switch (type)
 144   {
 145   case MEMCACHED_HASH_DEFAULT: return "MEMCACHED_HASH_DEFAULT";
 146   case MEMCACHED_HASH_MD5: return "MEMCACHED_HASH_MD5";
 147   case MEMCACHED_HASH_CRC: return "MEMCACHED_HASH_CRC";
 148   case MEMCACHED_HASH_FNV1_64: return "MEMCACHED_HASH_FNV1_64";
 149   case MEMCACHED_HASH_FNV1A_64: return "MEMCACHED_HASH_FNV1A_64";
 150   case MEMCACHED_HASH_FNV1_32: return "MEMCACHED_HASH_FNV1_32";
 151   case MEMCACHED_HASH_FNV1A_32: return "MEMCACHED_HASH_FNV1A_32";
 152   case MEMCACHED_HASH_HSIEH: return "MEMCACHED_HASH_HSIEH";
 153   case MEMCACHED_HASH_MURMUR: return "MEMCACHED_HASH_MURMUR";
 154   case MEMCACHED_HASH_JENKINS: return "MEMCACHED_HASH_JENKINS";
 155   case MEMCACHED_HASH_CUSTOM: return "MEMCACHED_HASH_CUSTOM";
 156   default:
 157   case MEMCACHED_HASH_MAX: return "INVALID memcached_hash_t";
 158   }
 159 }