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_KETAMA:
  31   case MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA_SPY:
  32     {
  33       uint32_t num= ptr->continuum_points_counter;
  34       WATCHPOINT_ASSERT(ptr->continuum);
  35
  36       hash= hash;
  37       memcached_continuum_item_st *begin, *end, *left, *right, *middle;
  38       begin= left= ptr->continuum;
  39       end= right= ptr->continuum + num;
  40
  41       while (left < right)
  42       {
  43         middle= left + (right - left) / 2;
  44         if (middle->value < hash)
  45           left= middle + 1;
  46         else
  47           right= middle;
  48       }
  49       if (right == end)
  50         right= begin;
  51       return right->index;
  52     }
  53   case MEMCACHED_DISTRIBUTION_MODULA:
  54     return hash % memcached_server_count(ptr);
  55   case MEMCACHED_DISTRIBUTION_RANDOM:
  56     return (uint32_t) random() % memcached_server_count(ptr);
  57   case MEMCACHED_DISTRIBUTION_CONSISTENT_MAX:
  58   default:
  59     WATCHPOINT_ASSERT(0); /* We have added a distribution without extending the logic */
  60     return hash % memcached_server_count(ptr);
  61   }
  62   /* NOTREACHED */
  63 }
  64
  65 /*
  66   One version is public and will not modify the distribution hash, the other will.
  67 */
  68 static inline uint32_t _generate_hash_wrapper(const memcached_st *ptr, const char *key, size_t key_length)
  69 {
  70   WATCHPOINT_ASSERT(memcached_server_count(ptr));
  71
  72   if (memcached_server_count(ptr) == 1)
  73     return 0;
  74
  75   if (ptr->flags.hash_with_prefix_key)
  76   {
  77     size_t temp_length= ptr->prefix_key_length + key_length;
  78     char temp[temp_length];
  79
  80     if (temp_length > MEMCACHED_MAX_KEY -1)
  81       return 0;
  82
  83     strncpy(temp, ptr->prefix_key, ptr->prefix_key_length);
  84     strncpy(temp + ptr->prefix_key_length, key, key_length);
  85
  86     return generate_hash(ptr, temp, temp_length);
  87   }
  88   else
  89   {
  90     return generate_hash(ptr, key, key_length);
  91   }
  92 }
  93
  94 static inline void _regen_for_auto_eject(memcached_st *ptr)
  95 {
  96   if (_is_auto_eject_host(ptr) && ptr->next_distribution_rebuild)
  97   {
  98     struct timeval now;
  99
 100     if (gettimeofday(&now, NULL) == 0 &&
 101         now.tv_sec > ptr->next_distribution_rebuild)
 102     {
 103       run_distribution(ptr);
 104     }
 105   }
 106 }
 107
 108 void memcached_autoeject(memcached_st *ptr)
 109 {
 110   _regen_for_auto_eject(ptr);
 111 }
 112
 113 uint32_t memcached_generate_hash_with_redistribution(memcached_st *ptr, const char *key, size_t key_length)
 114 {
 115   uint32_t hash= _generate_hash_wrapper(ptr, key, key_length);
 116
 117   _regen_for_auto_eject(ptr);
 118
 119   return dispatch_host(ptr, hash);
 120 }
 121
 122 uint32_t memcached_generate_hash(const memcached_st *ptr, const char *key, size_t key_length)
 123 {
 124   return dispatch_host(ptr, _generate_hash_wrapper(ptr, key, key_length));
 125 }
 126
 127 hashkit_st *memcached_get_hashkit(memcached_st *ptr)
 128 {
 129   return &ptr->hashkit;
 130 }